CN113212543B - Variable transmission ratio circulating ball type electro-hydraulic steering system and control method thereof - Google Patents

Variable transmission ratio circulating ball type electro-hydraulic steering system and control method thereof Download PDF

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Publication number
CN113212543B
CN113212543B CN202110652247.1A CN202110652247A CN113212543B CN 113212543 B CN113212543 B CN 113212543B CN 202110652247 A CN202110652247 A CN 202110652247A CN 113212543 B CN113212543 B CN 113212543B
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motor
steering
corner
assisted
signal
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CN113212543A (en
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徐坤豪
赵万忠
邹松春
栾众楷
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D3/00—Steering gears
    • B62D3/02—Steering gears mechanical
    • B62D3/04—Steering gears mechanical of worm type
    • B62D3/06—Steering gears mechanical of worm type with screw and nut
    • B62D3/08—Steering gears mechanical of worm type with screw and nut using intermediate balls or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0421—Electric motor acting on or near steering gear
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
    • B62D5/065—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle characterised by specially adapted means for varying pressurised fluid supply based on need, e.g. on-demand, variable assist
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Power Steering Mechanism (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)

Abstract

The invention discloses a variable transmission ratio circulating ball type electro-hydraulic steering system and a control method thereof, wherein the control method comprises the following steps: the system comprises a steering wheel module, a variable transmission ratio hydraulic power-assisted module, a mechanical transmission module, a motor power-assisted module and a main controller module; the electro-hydraulic steering system can select different motor power-assisted modes according to transmission ratio signals of different working conditions, realizes the adjustment of the steering power-assisted force along with the transmission ratio signal of a harmonic rotation angle by coordinately controlling the steering through the hydraulic power-assisted motor and the electric power-assisted motor, integrates the triple advantages of quick electric response, large hydraulic power-assisted force and good variable transmission ratio stability, improves the response speed, enhances the anti-interference capability and reduces the overall energy consumption to a certain extent.

Description

Variable transmission ratio circulating ball type electro-hydraulic steering system and control method thereof
Technical Field
The invention belongs to the technical field of automobile steering systems, and particularly relates to a variable transmission ratio circulating ball type electro-hydraulic steering system and a control method thereof.
Background
With the development of vehicle control technology and the higher requirements of people on driving safety and comfort; the hydraulic power-assisted steering system cannot meet new requirements due to the problems that active control cannot be achieved, the steering power-assisted characteristic is not adjustable and the like. Although the electric power steering system can solve the problems, the electric power steering system has the defect of insufficient power assistance in the application of medium and heavy commercial vehicles, and the electric control hydraulic steering system provided at present still has the defects of high energy consumption, low response speed, poor road feel and the like. Therefore, the research on the compound type electric control hydraulic power-assisted steering system has important significance.
The transmission ratio of the existing commercial vehicle electric control hydraulic power-assisted steering system is fixed, active correction control cannot be realized according to the requirement of the vehicle running condition on the operation stability, and when the steering is carried out at low speed, the steering force of a driver is large, and the steering hand feeling and the comfort are poor; at the time of high-speed steering, the operation reaction time of the driver is short, and the mass inertia of the commercial vehicle is large, so that the safety and stability are low. The variable transmission ratio mechanism composed of a plurality of planet gears and a rack and pinion steering gear provided in the prior art is difficult to meet the characteristics of large transmission ratio and large torque required by a commercial vehicle, and the novel variable transmission ratio mechanism suitable for the commercial vehicle needs to be researched.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a variable transmission ratio circulating ball type electro-hydraulic steering system and a control method thereof, so as to solve the problems of fixed transmission ratio, lower transmission efficiency, poorer road feel and slow response speed of the conventional commercial vehicle steering system.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the invention discloses a variable transmission ratio circulating ball type electro-hydraulic steering system, which comprises: the system comprises a steering wheel module, a variable transmission ratio hydraulic power-assisted module, a mechanical transmission module, a motor power-assisted module and a main controller module; wherein the content of the first and second substances,
the steering wheel module includes: the steering wheel, the first steering column, the steering wheel angle sensor and the steering wheel torque sensor;
the steering wheel is fixedly connected with the first steering column;
the steering wheel corner sensor and the steering wheel torque sensor are fixedly connected with the first steering column, respectively acquire corner and torque signals of the steering wheel and send the acquired signals to the main controller module;
the variable transmission ratio hydraulic power assisting module comprises: the steering system comprises a variable transmission ratio module, a second steering column torque sensor, a circulating ball type hydraulic power-assisted steering gear and a hydraulic power-assisted module;
the second steering column torque sensor is fixedly connected with the second steering column and used for acquiring a torque signal of the second steering column and sending the acquired signal to the main controller module;
the variable transmission ratio module includes: the device comprises a corner motor, a corner motor corner controller, a corner motor corner sensor, a harmonic gear mechanism and a locking mechanism;
the corner motor corner sensor is fixedly connected with the corner motor and used for collecting a corner signal of the corner motor; the locking mechanism is arranged on the corner motor and used for locking the corner motor when the corner motor does not work or fails; the input end of the corner controller of the corner motor is connected with the main controller module, the output end of the corner controller is connected with the corner motor, and the corner controller is used for converting the front wheel corner at the current moment to obtain the actual corner to be output by the corner motor, subtracting the ideal corner of the corner motor from the actual corner of the corner motor to obtain a real-time corner motor control signal and controlling the corner motor;
the harmonic gear mechanism includes: a wave generator, a flexible gear and a rigid gear; the flexible gear is an external gear, the rigid gear is an internal gear, and a gear difference exists between the rigid gear and the flexible gear; the first steering column is used as an input end and is in gapless connection with a flexible gear of the harmonic gear mechanism through a spline to drive the flexible gear to rotate; the wave generator consists of a rotary part and a flexible bearing; the wave generator is arranged in an inner ring of the flexible gear, the outer side surface of the wave generator drives the flexible gear to generate elastic deformation through the flexible bearing, and the flexible gear is changed into an elliptic gear and rotates along with the rotation direction opposite to the rotation direction of the rotary component; the rotary part positioned in the middle of the wave generator is connected with a rotor shaft of the corner motor; the outer teeth of the flexible gear are meshed with the inner teeth of the rigid gear; the rigid wheel is in gapless connection with one end of the second steering column through a spline; the other end of the second steering column is connected with the circulating ball type hydraulic power-assisted steering gear;
the circulating ball type hydraulic power-assisted steering gear (13) is composed of two-stage transmission pairs: the first stage is a screw and nut transmission pair (11); the second stage is a rack and sector transmission pair (12); the second steering column is connected with the circulating ball type hydraulic power-assisted steering gear through a screw and nut transmission pair;
the hydraulic power assisting module comprises: the hydraulic pump, the hydraulic pump driving motor controller, the first speed reducing mechanism, the oil tank, the servo proportional solenoid valve, the oil pipe, the first pressure sensor and the second pressure sensor; the input end of the hydraulic pump driving motor controller is connected with the main controller module, and the output end of the hydraulic pump driving motor controller is connected with the hydraulic pump driving motor and used for receiving a hydraulic pump driving motor control signal sent by the main controller module to control the hydraulic pump driving motor; the hydraulic pump driving motor is connected with the hydraulic pump through a first speed reducing mechanism, hydraulic oil from an oil tank is pumped into the circulating ball type hydraulic power-assisted steering gear through the servo proportional electromagnetic valve, oil pressure difference is formed in the circulating ball type hydraulic power-assisted steering gear, and power is provided for a steering system under the action of the oil pressure difference; the first pressure sensor and the second pressure sensor are arranged on an oil pipe of an oil inlet and outlet way of the recirculating ball type hydraulic power steering gear and are used for detecting hydraulic power assistance on two sides of the recirculating ball type hydraulic power steering gear and sending an actual hydraulic power assistance signal;
the mechanical transmission module comprises: the steering system comprises a steering rocker arm, a steering drag link, a left steering wheel, a left steering knuckle arm, a left steering trapezoid arm, a steering tie rod, a right steering trapezoid arm, a right steering knuckle and a right steering wheel;
the output end of the circulating ball type hydraulic power-assisted steering gear is connected with the sector transmission pair and one end of a steering rocker arm through a rack, and the other end of the steering rocker arm is connected with a left steering knuckle arm through a steering drag link to drive a left steering knuckle and a left steering wheel to deflect; the left steering knuckle arm is connected with one end of a steering tie rod through a left steering trapezoid arm; the other end of the tie rod is connected with a right steering trapezoid arm, the right steering trapezoid arm is connected with a right steering knuckle through a right knuckle arm, and the right steering knuckle drives a right steering wheel to steer;
the motor assist module includes: the electric power-assisted motor, the electric power-assisted motor controller and the second speed reducing mechanism; the input end of the electric power-assisted motor controller is connected with the main controller module, and the output end of the electric power-assisted motor controller is connected with the electric power-assisted motor; the electric power-assisted motor transmits the electric power-assisted force to a second steering column through a second speed reducing mechanism to provide power-assisted force for a steering system;
the main controller module includes: the system comprises a signal processing unit, other state units of a vehicle, an ideal transmission ratio controller, a corner motor corner calculator, a stability controller, a power-assisted decision unit, a diagnosis unit, a fault alarm unit and a motor driving unit;
the signal processing unit is electrically connected with the sensors, acquires signals acquired by the sensors in real time, and receives a steering wheel corner signal A, a steering wheel torque signal B, a corner motor corner signal C, an actual hydraulic power-assisted signal D and a second steering column torque signal; meanwhile, the signal processing unit is electrically connected with other state units of the vehicle to acquire other state signals of the vehicle;
the other state units of the vehicle are used for acquiring a vehicle speed signal I, a yaw rate signal J, a mass center side deviation angle signal K and a lateral acceleration signal L of the current vehicle state;
the ideal transmission ratio controller is used for determining a transmission ratio signal at the current moment through a preset vehicle speed-steering wheel rotation angle-ideal transmission ratio map according to the vehicle speed signal and the steering wheel rotation angle signal obtained by the signal processing unit and calculating an expected front wheel rotation angle signal at the current moment; inputting the transmission ratio signal and a steering wheel corner signal into a corner motor corner calculator together to obtain an ideal corner signal of a corner motor, and superposing an additional corner provided by the corner motor and a corner of a first steering column to realize variable transmission ratio control;
the stability controller is used for passing through H according to the vehicle speed signal, the yaw rate signal, the lateral acceleration signal and the mass center and lateral deviation angle signal obtained by the signal processing unit2/H∞A robust control method obtains a vehicle stability control signal; then the obtained vehicle stability control signal and the obtained corner motor mechanism are combinedInputting the wanted rotation angle signal and the rotation angle signal of the rotation angle motor into a rotation angle controller of the rotation angle motor together, converting the rotation angle of the front wheel to obtain the actual rotation angle of the rotation angle motor, subtracting the ideal rotation angle of the rotation angle motor from the actual rotation angle of the rotation angle motor, and obtaining a real-time rotation angle motor control signal through PID (proportion integration differentiation) setting;
the output end of the main controller module is respectively electrically connected with a corner motor, an electric power-assisted motor, a servo proportional solenoid valve and a hydraulic pump driving motor, and outputs a corner motor control signal F to control the corner motor to output a corner; outputting a hydraulic pump driving motor control signal G to control the torque of a hydraulic pump driving motor; outputting a servo proportional solenoid valve control signal H to control the opening of the servo proportional solenoid valve; outputting a control signal M of the electric power-assisted motor to control the output torque of the electric power-assisted motor;
the diagnosis unit detects whether the electro-hydraulic steering system works normally in the running process of the vehicle, compares a transmission ratio signal received by the main controller module with a given transmission ratio threshold value and judges the working mode of each motor;
the power-assisted decision unit receives input signals of the signal processing unit and the diagnosis unit through a vehicle-mounted communication line, and outputs instructions to the motor driving unit through the vehicle-mounted communication line after calculation according to a power-assisted distribution strategy; in the steering wheel aligning process of a steering system, a power-assisted decision unit compensates road feel change caused by an additional steering angle generated by a steering angle motor after variable transmission ratio and stability control according to a steering angle motor control signal, a steering wheel torque signal and a transmission ratio signal, and outputs an instruction to a motor driving unit through a vehicle-mounted communication line after calculation;
the motor driving unit selects different working modes according to an output instruction of the power-assisted decision control unit and respectively outputs a corner motor control signal, an electric power-assisted motor control signal and a hydraulic pump driving motor control signal;
the fault alarm unit is used for reminding a driver of fault information.
Further, the outline of the rotary part is a curve outline.
Furthermore, the corner motor is a direct-current brushless motor, is packaged in a variable transmission ratio module shell and consists of a permanent magnet, a coil and a rotor shaft, and the rotor shaft is connected with a wave generator and transmits the torque of the corner motor to a harmonic gear mechanism; the locking mechanism consists of a lock frame fixed on the corner motor, a lock rod arranged on the shell and an electromagnetic valve for enabling the lock rod to act.
Further, the power-assisted distribution strategy is to obtain the total required power-assisted torque of the steering system according to the obtained steering wheel torque, the front wheel rotation angle and the transmission ratio signal; wherein when the transmission ratio signal i received by the main controller module is less than or equal to i0When the electric power assisting device is used, the hydraulic power assisting module and the electric power assisting module work simultaneously, wherein the power assisting provided by the hydraulic power assisting module and the power assisting provided by the electric power assisting motor are 3: 2.
The harmonic gear mechanism is a transmission device which achieves the transmission purpose by means of elastic deformation movement, a first steering pipe column is used as an input end to drive a flexible gear of the harmonic gear mechanism to rotate, when a corner motor drives the corner motor, a rotor of the corner motor drives a wave generator to rotate, the flexible gear is driven by a flexible bearing to deform in the rotating process of the wave generator, the superposition of corners is realized, the flexible gear is meshed with a rigid gear in the long axis direction of the wave generator, the short axis direction is disengaged, the meshing area of the flexible gear and the rigid gear is continuously changed along with the rotation of the wave generator, the wave generator rotates for one circle, the flexible gear and the rigid gear have several tooth differences, the flexible gear can generate displacement movement of several teeth relative to the rigid gear, so that the transmission ratio is changed, then, the rigid gear of the harmonic gear drives a second steering pipe column, the superposed corners are output, and the input of auxiliary corners is realized.
In the electro-hydraulic steering system, a current transmission ratio signal is calculated through an ideal transmission ratio controller, a variable transmission ratio module is controlled to realize active steering, and different motor power-assisted modes are selected according to the transmission ratio signal under the current working condition; calculating the power-assisted and return-timing compensation moment required by steering through the steering wheel angle and the torque, and controlling the output torque of the electric power-assisted motor, the torque of a hydraulic pump driving motor and the opening degree of a servo proportional solenoid valve according to the power-assisted so as to control the moment transmitted to the recirculating ball type hydraulic power-assisted steering device by the motor power-assisted module and the flow rate of hydraulic oil in the hydraulic power-assisted module flowing into the recirculating ball type hydraulic power-assisted steering device; the circulating ball type hydraulic power-assisted steering device is used for forming steering power assistance and road feel compensation according to the torque transmitted by the motor power-assisted module and the flow of hydraulic oil flowing into the motor power-assisted module, and further driving wheels of a vehicle to rotate.
The invention discloses a control method of a variable transmission ratio circulating ball type electro-hydraulic steering system, which is based on the system and comprises the following steps:
1) according to the driving condition of the vehicle, inputting a steering wheel corner, and receiving a steering wheel corner signal, a steering wheel torque signal, a vehicle speed signal, a yaw velocity signal, a lateral acceleration signal, a mass center side deviation angle signal, a corner motor corner signal and a second steering column torque signal in real time through a signal processing unit;
2) and (3) carrying out variable transmission ratio control: inputting the obtained vehicle speed signal and steering wheel rotation angle signal into an ideal transmission ratio controller, determining a transmission ratio signal according to a preset vehicle speed-steering wheel rotation angle-ideal transmission ratio map, calculating a front wheel rotation angle signal expected at the current moment, and inputting the transmission ratio signal and the steering wheel rotation angle signal into a rotation angle motor rotation angle calculator together to obtain a rotation angle motor ideal rotation angle signal;
3) and (3) carrying out stability control: inputting the obtained vehicle speed signal, yaw rate signal, lateral acceleration signal and mass center and lateral deviation angle signal into a vehicle stability controller, and utilizing H2/H∞A robust control method obtains a vehicle stability control signal; then inputting the obtained vehicle stability control signal, the obtained ideal corner signal of the corner motor and the corner signal of the corner motor into a corner motor controller, converting the front wheel corner to obtain the actual corner of the corner motor, subtracting the ideal corner of the corner motor and the actual corner of the corner motor, and obtaining a real-time corner motor control signal through PID (proportion integration differentiation) setting;
controlling the rotation angle of the rotation angle motor according to the obtained real-time rotation angle motor control signal, driving a harmonic gear mechanism to move, and simultaneously overlapping the rotation angle input to a flexible wheel by a steering wheel to complete variable transmission ratio control and stability control of a steering system and realize the automatic steering of a vehicle driver;
4) controlling a hydraulic pump driving motor: when the diagnosis unit judges that hydraulic assistance is needed, a target hydraulic assistance signal is obtained according to an assistance distribution strategy; the first pressure sensor and the second pressure sensor collect oil pressure on the left side and the right side of the power-assisted oil cylinder, the generated actual hydraulic power-assisted signal is used as feedback, the difference value of the target hydraulic power-assisted signal and the actual hydraulic power-assisted signal is transmitted to the main controller module, and the difference value is transmitted to the main controller module through the H2/H∞The robust control method forms a closed loop; the opening of the servo proportional solenoid valve and the torque of a hydraulic pump driving motor are controlled through the main controller module, so that hydraulic power is generated to realize vehicle steering;
5) carrying out electric power-assisted motor control: when the diagnosis unit judges that electric power assistance is needed, a target electric power assistance signal is obtained according to a power assistance distribution strategy, then an actual torque signal generated by a second steering column torque sensor is used as feedback, and an electric power assistance motor controller performs closed-loop control through PID according to the target torque and the actual torque signal to obtain a control signal of an electric power assistance motor;
6) in the running process of a vehicle, the diagnosis unit detects whether the electro-hydraulic steering system works normally or not and judges the working mode of the motor according to a transmission ratio signal at the current moment, the motor driving unit selects different working modes and a road feel compensation mode of the motor according to an output instruction of the power-assisted decision unit, and simultaneously, an electric power-assisted motor control signal and a hydraulic power-assisted motor control signal are respectively output according to a power-assisted distribution strategy, so that power-assisted distribution is realized.
Further, the power-assisted distribution strategy is specifically as follows: according to the obtained steering wheel torque, the front wheel rotation angle and the transmission ratio signal, the total required power-assisted torque of the steering system is obtained and is determined by the following formulas (1) and (2); wherein when the transmission ratio signal i received by the main controller module is less than or equal to i0When the electric power assisting device is used, the hydraulic power assisting module and the electric power assisting module work simultaneously, wherein the power assisting provided by the hydraulic power assisting module and the power assisting provided by the electric power assisting motor are 3: 2;
Figure BDA0003112053850000051
Figure BDA0003112053850000052
Tz＝Te+Th (3)
in the formula, TzAnd TzmaxRespectively a total required power-assisted torque and a maximum total required power-assisted torque; t isd0，TdAnd TdmaxThe steering wheel torque at the time of starting power assistance, the steering wheel torque and the steering wheel torque at the time of maximum power assistance are respectively; ki(i) Is the transmission ratio inductance; alpha is an assisting force distribution proportion coefficient, and is specifically 0.8-0.95; t isRTo the steering resistance torque, deltafIs the front wheel angle, G is the first reduction gear reduction ratio, i0＝11.5,TeAssistance provided for a hydraulic assistance module, ThThe power assisting device provides power assisting for the electric power assisting motor.
Further, the step 6) of selecting the working mode of the motor driving unit specifically includes the following steps:
61) when the corner motor works normally, variable transmission ratio control is carried out, an additional corner is provided by driving the harmonic gear mechanism, linear superposition is carried out on the additional corner and the corner input of the steering wheel, and the additional corner and the corner input are output to a second steering column, so that variable transmission ratio control and stability control are realized;
62) when the vehicle starts, the transmission ratio of the steering system is small, and the transmission ratio i output by the variable transmission ratio driving module is smaller than or equal to the transmission ratio i0The electric power-assisted motor starts to work, the hydraulic power-assisted module starts to work again, the servo proportional solenoid valve is opened, the hydraulic pump drives the motor to work and distributes power-assisted torque, and the hydraulic power-assisted module provides most power for the system;
wherein, when the transmission ratio i is less than or equal to the transmission ratio i2And is less than i0When the road is in use, the generated front wheel has a large steering angle, and the driving motor of the hydraulic pump compensates the road feel; when the transmission ratio becomes larger, the transmission ratio i is larger than i2And is less than or equal to i0When the vehicle runs, the road feel is compensated by the electric power-assisted motor;
63) when the vehicle speed is increased, the transmission ratio of the steering system is increased, and the transmission ratio i output by the system variable transmission ratio driving module is larger than the transmission ratio i0Is less than or equal to the transmission ratio i1When the system is used, the electric power-assisted motor stops providing power assistance, and only the hydraulic power-assisted module works to provide steering power assistance for the system; the electric power-assisted motor works only when the steering wheel turns back to compensate the road feel;
64) when the transmission ratio i output by the variable transmission ratio driving module is larger than the transmission ratio i1When the hydraulic power-assisted module stops working, only the electric power-assisted motor provides steering power, and meanwhile, the electric power-assisted motor compensates the road feel;
65) when the corner motor fails, the main controller module cuts off the power supply of a locking electromagnetic valve in the variable transmission ratio module, locks the corner motor and runs at a constant steering transmission ratio, and the electric power-assisted motor and the hydraulic pump drive motor work simultaneously to provide power assistance and trigger a failure alarm unit to remind a driver of failure information;
66) when the hydraulic power-assisted module or the motor power-assisted module breaks down, the other one of the hydraulic power-assisted module and the motor power-assisted module is used for providing power-assisted steering instead of the power-assisted steering, and meanwhile, the fault alarm unit is triggered to remind a driver of fault information;
wherein i2＝4.3，i0＝11.5，i1＝20.8。
Further, the road feel compensation in step 6) is specifically as follows: inputting the steering wheel torque signal and the transmission ratio signal in the step 3) into a power-assisted decision unit, compensating the road feel change caused by the additional steering angle generated by the steering wheel motor after the variable transmission ratio and the stability control, and reducing the provided power assistance by a hydraulic pump driving motor or an electric power-assisted motor or providing reverse power assistance to achieve the aim of road feel compensation.
Further, when the corner motor is not electrified or fails, the harmonic gear mechanism is locked, and the transmission ratio of the steering system is kept constant; when the rotation angle motor drives the wave generator, the flexible gear is driven to rotate, and when the elliptical rotor and the flexible gear rotate in the same direction, the number of teeth of the flexible gear is less than that of the outer ring rigid gear, so that the transmission ratio of a steering system is reduced; when the elliptical rotor and the flexible gear rotate reversely, the rotation angle of the rigid gear is smaller than that of the flexible gear, the transmission ratio of the steering system is increased, and controllable variable transmission ratio control is realized.
The invention has the beneficial effects that:
1. the harmonic gear mechanism is driven by the corner motor, so that the transmission clearance is small, the transmission ratio range is large, the bearing capacity is strong, the transmission is stable, the precision is high, and the cost is low; the variable transmission ratio function of the power-assisted steering system of the large-load commercial vehicle can be realized, the active safety of the vehicle is enhanced, the requirements of the steering sensitivity of the vehicle during low-speed running and the steering stability of the vehicle during high-speed running are met, and the characteristics of the commercial vehicle of large transmission ratio and large torque are met;
2. the electro-hydraulic steering system can coordinate and control steering through the hydraulic power-assisted motor and the electric power-assisted motor, realizes that the steering power-assisted force is adjustable along with a transmission ratio signal of a harmonic rotation angle, integrates the triple advantages of quick electric response, large hydraulic power-assisted force and good variable transmission ratio stability, improves the response speed, strengthens the anti-interference capability and reduces the overall energy consumption;
3. according to the invention, by compensating the road feel in real time, the hydraulic system damping can be adopted to compensate the road feel or the electric power system can compensate the road feel according to the working condition, so that the hydraulic hybrid steering system has multiple road feel compensation modes, and the overall road feel comfort level of the electro-hydraulic hybrid steering system is improved.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
FIG. 2 is an internal detail view of the variable ratio module;
FIG. 3 is a flow chart of the switching of the operation modes of the motor driving unit according to the present invention;
FIG. 4 is a schematic diagram of a control method for an electro-hydraulic steering system according to the present invention;
FIG. 5 is a flow chart of a power-assisted distribution strategy control of the present invention;
in the figure, 1-steering wheel, 2-first steering column, 3-steering wheel angle sensor, 4-steering wheel torque sensor, 5-variable transmission ratio hydraulic power-assisted module, 6-variable transmission ratio module, 7-angle motor, 8-harmonic gear, 9-second steering column torque sensor, 10-second steering column, 11-screw and nut transmission pair, 12-rack and sector transmission pair, 13-circulating ball type hydraulic power-assisted steering gear, 14-steering rocker arm, 15-left steering wheel, 16-left steering knuckle, 17-left steering knuckle arm, 18-left steering trapezoid arm, 19-steering straight pull rod, 20-electric power-assisted motor, 21-second speed reducing mechanism, 22-hydraulic power-assisted module, 23-servo proportion solenoid valve, 24-tie rod, 25-right steering trapezoid arm, 26-right steering knuckle arm, 27-right steering knuckle, 28-right steering wheel, 29-oil tank, 30-hydraulic pump driving motor, 31-hydraulic pump, 32-vehicle other state unit, 33-main controller module, 34-first pressure sensor, 35-second pressure sensor, 36-first speed reducing mechanism, 61-corner motor corner sensor, 62-wave generator (elliptic rotor), 63-flexible wheel, 64-rigid wheel, 65-spline;
the control method comprises the steps of A-a steering wheel turning angle signal, B-a steering wheel torque signal, C-a turning angle motor turning angle signal, D-an actual hydraulic power assisting signal, an F-turning angle motor control signal, a G-hydraulic pump driving motor control signal, an H-servo proportional solenoid valve control signal, an M-electric power assisting motor control signal, an I-vehicle speed signal, a J-yaw rate signal, a K-mass center side deviation angle signal and an L-lateral acceleration signal.
Detailed Description
In order to facilitate understanding of those skilled in the art, the present invention will be further described with reference to the following examples and drawings, which are not intended to limit the present invention.
Referring to fig. 1 and 2, the variable transmission ratio recirculating ball type electro-hydraulic steering system of the invention comprises: the system comprises a steering wheel module, a variable transmission ratio hydraulic power-assisted module 5, a mechanical transmission module, a motor power-assisted module and a main controller module 33; wherein the content of the first and second substances,
the steering wheel module includes: the steering wheel comprises a steering wheel 1, a first steering column 2, a steering wheel corner sensor 3 and a steering wheel torque sensor 4;
the steering wheel 1 is fixedly connected with a first steering column 2;
the steering wheel corner sensor 3 and the steering wheel torque sensor 4 are fixedly connected with the first steering column 2, respectively collect corner and torque signals of a steering wheel, and send the collected signals to the main controller module 33;
the variable transmission ratio hydraulic power assisting module 5 comprises: the variable transmission ratio module 6, the second steering column 10, the second steering column torque sensor 9, the recirculating ball type hydraulic power steering gear 13 and the hydraulic power assisting module 22;
the second steering column torque sensor 9 is fixedly connected with the second steering column 10 and used for acquiring a torque signal of the second steering column and sending the acquired signal to the main controller module 33;
the variable transmission ratio module 6 includes: the device comprises a corner motor 7, a corner motor corner controller, a corner motor corner sensor 61, a harmonic gear mechanism 8 and a locking mechanism;
the corner motor corner sensor 61 is fixedly connected with the corner motor 7 and is used for collecting a corner signal of the corner motor; the locking mechanism is arranged on the corner motor and used for locking the corner motor when the corner motor 7 does not work or fails; the input end of the corner controller of the corner motor is connected with the main controller module, the output end of the corner controller is connected with the corner motor, and the corner controller is used for converting the front wheel corner at the current moment to obtain the actual corner to be output by the corner motor, subtracting the ideal corner of the corner motor from the actual corner of the corner motor, obtaining a real-time corner motor control signal through PID (proportion integration differentiation) setting, and controlling the corner motor;
the harmonic gear mechanism 8 includes: a wave generator 62, a flexible gear 63 and a rigid gear 64; the flexible gear is an external gear, the rigid gear is an internal gear, and a gear difference exists between the rigid gear 64 and the flexible gear 63; the first steering column 2 is used as an input end and is in gapless connection with a flexible gear 63 of the harmonic gear mechanism through a spline 65 to drive the flexible gear 63 to rotate; the wave generator 62 is composed of a rotary part and a flexible bearing, wherein the outline of the rotary part is a curve outline; the wave generator 62 is arranged in the inner ring of the flexible gear, the outer side surface of the wave generator drives the flexible gear 63 to generate elastic deformation through a flexible bearing, and the flexible gear 63 is changed into an elliptic gear and rotates along with the rotation direction of the rotary component; the rotary part positioned in the middle of the wave generator is connected with a rotor shaft of the corner motor; the outer teeth of the flexible gear are meshed with the inner teeth of the rigid gear; the rigid wheel is connected with one end of the second steering column 10 in a gapless way through a spline; the other end of the second steering column 10 is connected with a recirculating ball type hydraulic power-assisted steering gear 13;
the recirculating ball type hydraulic power-assisted steering gear 13 is composed of two stages of transmission pairs: the first stage is a screw and nut transmission pair 11; the second stage is a rack and gear sector transmission pair 12; the circulating ball type hydraulic power-assisted steering gear 13 is provided with an oil inlet, an oil outlet, a constant-current rotary valve and a power-assisted oil cylinder; the constant-flow rotary valve consists of a valve body and a valve core, wherein the valve body is provided with a middle oil ring groove, an upper oil ring groove and a lower oil ring groove; the power-assisted oil cylinder comprises a left steering power cavity, a right steering power cavity and a piston push rod; the second steering column 10 is connected with a circulating ball type hydraulic power-assisted steering gear 13 through a screw and nut transmission pair 11; the power-assisted oil cylinder is fixedly connected with the middle part of the steering rocker arm 14 through a piston push rod; working oil flows into a middle oil ring groove of a valve body of a constant-current type rotary valve from an oil inlet of a circulating ball type hydraulic power steering gear shell, enters between the valve body and a valve core through a through hole at the bottom of the oil ring groove, flows to an upper oil ring groove and a lower oil ring groove of the excircle of the valve body, and then flows to a left steering power cavity and a right steering power cavity of a power cylinder through an oil duct of the circulating ball type hydraulic power steering gear shell; meanwhile, the oil flowing into the valve body returns to the oil tank from the oil outlet through the oil pipe to form normal flow type oil circulation;
the second steering column is connected with a circulating ball type hydraulic power-assisted steering gear 13 through a screw and nut transmission pair 11; the power-assisted oil cylinder is fixedly connected with the middle part of a steering rocker arm of the mechanical transmission module through a piston push rod; working oil flows into a middle oil ring groove of a constant-current type rotary valve from an oil inlet of a shell of the circulating ball type hydraulic power-assisted steering gear, enters between a valve body and a valve core, flows to an upper oil ring groove and a lower oil ring groove on the excircle of the valve body, and flows to a left steering power cavity and a right steering power cavity of a power-assisted oil cylinder through the shell;
the hydraulic assist module 22 includes: a hydraulic pump 31, a hydraulic pump driving motor 30, a hydraulic pump driving motor controller, a first speed reducing mechanism 36, an oil tank 29, a servo proportional solenoid valve 23, an oil pipe, a first pressure sensor 34 and a second pressure sensor 35; the input end of the hydraulic pump driving motor controller is connected with the main controller module 33, and the output end of the hydraulic pump driving motor controller is connected with the hydraulic pump driving motor 30 and used for receiving a hydraulic pump driving motor control signal sent by the main controller module 33 to control the hydraulic pump driving motor; the hydraulic pump driving motor 30 is connected with the hydraulic pump 31 through a first speed reducing mechanism 36, hydraulic oil from the oil tank 29 is pumped into the circulating ball type hydraulic power steering gear 13 through the servo proportional electromagnetic valve 23, oil pressure difference is formed in the power cylinder, and a piston push rod provides power for a steering system under the action of the oil pressure difference; the first pressure sensor and the second pressure sensor are arranged on an oil pipe of an oil inlet and outlet way of the recirculating ball type hydraulic power steering gear 13 and are used for detecting hydraulic power assistance on two sides of the recirculating ball type hydraulic power steering gear and sending an actual hydraulic power assistance signal;
the mechanical transmission module comprises: a steering rocker 14, a steering drag link 19, a left steering wheel 15, a left steering knuckle 16, a left steering knuckle arm 17, a left steering trapezoid arm 18, a steering tie rod 24, a right steering trapezoid arm 25, a right steering knuckle arm 26, a right steering knuckle 27, and a right steering wheel 28;
the output end of the circulating ball type hydraulic power-assisted steering gear is connected with one end of a steering rocker arm 14 through a rack and sector transmission pair 12, and the other end of the steering rocker arm 14 is connected with a left steering knuckle arm 17 through a steering drag link 19 to drive a left steering knuckle 16 and a left steering wheel 15 to deflect; the left knuckle arm 17 is connected with one end of a tie rod 24 through a left steering trapezoid arm 18; the other end of the tie rod 24 is connected with a right steering trapezoid arm 25, the right steering trapezoid arm 25 is connected with a right knuckle 27 through a right knuckle arm 26, and the right knuckle 27 drives a right steering wheel 28 to steer;
the motor assist module includes: an electric assist motor 20, an electric assist motor controller, and a second reduction mechanism 21; the input end of the electric power-assisted motor controller is connected with the main controller module 33, and the output end of the electric power-assisted motor controller is connected with the electric power-assisted motor 20; the electric power-assisted motor 20 transmits electric power assistance to the second steering column through a second speed reducing mechanism 21 to provide power assistance for the steering system;
the main controller module 33 includes: the system comprises a signal processing unit, a vehicle other state unit 32, an ideal transmission ratio controller, a corner motor corner calculator, a stability controller, a power-assisted decision unit, a diagnosis unit, a fault alarm unit and a motor driving unit;
the signal processing unit is electrically connected with the sensors, acquires signals acquired by the sensors in real time, and receives a steering wheel corner signal A, a steering wheel torque signal B, a corner motor corner signal C, an actual hydraulic power-assisted signal D and a second steering column torque signal; meanwhile, the signal processing unit is electrically connected with other state units of the vehicle to acquire other state signals of the vehicle;
the other state units of the vehicle are used for acquiring a vehicle speed signal I, a yaw rate signal J, a mass center side deviation angle signal K and a lateral acceleration signal L of the current vehicle state;
the ideal transmission ratio controller is used for determining a transmission ratio signal at the current moment through a preset vehicle speed-steering wheel rotation angle-ideal transmission ratio map according to the vehicle speed signal and the steering wheel rotation angle signal obtained by the signal processing unit and calculating an expected front wheel rotation angle signal at the current moment; inputting the transmission ratio signal and a steering wheel corner signal into a corner motor corner calculator together to obtain an ideal corner signal of a corner motor, and superposing an additional corner provided by the corner motor and a corner of a first steering column to realize variable transmission ratio control;
the stability controller is used for passing through H according to the vehicle speed signal, the yaw rate signal, the lateral acceleration signal and the mass center and lateral deviation angle signal obtained by the signal processing unit2/H∞A robust control method obtains a vehicle stability control signal; inputting the obtained vehicle stability control signal, the obtained ideal corner signal of the corner motor and the corner signal of the corner motor into a corner motor controller, converting the front wheel corner to obtain the actual corner of the corner motor, subtracting the ideal corner of the corner motor and the actual corner of the corner motor, and obtaining a real-time corner motor control signal through PID (proportion integration differentiation) setting;
the output end of the main controller module is electrically connected with the corner motor 7, the electric power-assisted motor 20, the servo proportional solenoid valve 23 and the hydraulic pump driving motor 30, outputs a corner motor control signal F, controls the corner motor to output a corner, outputs a hydraulic pump driving motor control signal G, controls the torque of the hydraulic pump driving motor, outputs a servo proportional solenoid valve control signal H, controls the opening of the servo proportional solenoid valve, outputs an electric power-assisted motor control signal M and controls the electric power-assisted motor to output the torque;
the diagnosis unit detects whether the system works normally in the running process of the vehicle, compares a transmission ratio signal received by the main controller module with a given transmission ratio threshold value and judges the working mode of each motor;
the power-assisted decision unit receives input signals of the signal processing unit and the diagnosis unit through a vehicle-mounted communication line, and outputs instructions to the motor driving unit through the vehicle-mounted communication line after calculation according to a power-assisted distribution strategy; in the steering wheel aligning process of a steering system, a power-assisted decision unit compensates road feel change caused by an additional steering angle generated by a steering angle motor after variable transmission ratio and stability control according to a steering angle motor control signal, a steering wheel torque signal and a transmission ratio signal, and outputs an instruction to a motor driving unit through a vehicle-mounted communication line after calculation;
the power-assisted distribution strategy is to obtain the total required power-assisted torque of the steering system according to the obtained steering wheel torque, the front wheel rotation angle and the transmission ratio signal; wherein when the transmission ratio signal i received by the main controller module is less than or equal to i0When the electric power assisting device is used, the hydraulic power assisting module and the electric power assisting module work simultaneously, wherein the power assisting provided by the hydraulic power assisting module and the power assisting provided by the electric power assisting motor are 3: 2;
the motor driving unit selects different working modes according to an output instruction of the power-assisted decision control unit and respectively outputs a corner motor control signal, an electric power-assisted motor control signal and a hydraulic pump driving motor control signal;
the fault alarm unit is used for reminding a driver of fault information.
The corner motor is a direct-current brushless motor, is packaged in a variable transmission ratio module shell and consists of a permanent magnet, a coil and a rotor shaft, and the rotor shaft is connected with a wave generator and transmits the torque of the corner motor to a harmonic gear mechanism; the locking mechanism consists of a lock frame fixed on the corner motor, a lock rod arranged on the shell and an electromagnetic valve for enabling the lock rod to act.
The harmonic gear mechanism is a transmission device which achieves the transmission purpose by means of elastic deformation movement, a first steering pipe column is used as an input end to drive a flexible gear of the harmonic gear mechanism to rotate, when a corner motor drives the corner motor, a rotor of the corner motor drives a wave generator to rotate, the flexible gear is driven by a flexible bearing to deform in the rotating process of the wave generator, the superposition of corners is realized, the flexible gear is meshed with a rigid gear in the long axis direction of the wave generator, the short axis direction is disengaged, the meshing area of the flexible gear and the rigid gear is continuously changed along with the rotation of the wave generator, the wave generator rotates for one circle, the flexible gear and the rigid gear have several tooth differences, the flexible gear can generate displacement movement of several teeth relative to the rigid gear, so that the transmission ratio is changed, then, the rigid gear of the harmonic gear drives a second steering pipe column, the superposed corners are output, and the input of auxiliary corners is realized.
In the electro-hydraulic steering system, the current transmission ratio signal is calculated by the ideal transmission ratio controller, and the variable transmission ratio module is controlled to realize active steering; calculating the power-assisted and return-timing compensation moment required by steering through the steering wheel angle and the torque, and controlling the output torque of the electric power-assisted motor, the torque of a hydraulic pump driving motor and the opening degree of a servo proportional solenoid valve according to the power-assisted so as to control the moment transmitted to the recirculating ball type hydraulic power-assisted steering device by the motor power-assisted module and the flow rate of hydraulic oil in the hydraulic power-assisted module flowing into the recirculating ball type hydraulic power-assisted steering device; the circulating ball type hydraulic power-assisted steering device is used for forming steering power assistance and road feel compensation according to the torque transmitted by the motor power-assisted module and the flow of hydraulic oil flowing into the motor power-assisted module, and further driving wheels of a vehicle to rotate.
Referring to fig. 4 and 5, the control method of the variable transmission ratio recirculating ball type electro-hydraulic steering system of the invention is based on the system and comprises the following steps:
1) according to the driving condition of the vehicle, inputting a steering wheel corner, and receiving a steering wheel corner signal, a steering wheel torque signal, a vehicle speed signal, a yaw velocity signal, a lateral acceleration signal, a mass center side deviation angle signal, a corner motor corner signal and a second steering column torque signal in real time through a signal processing unit;
2) and (3) carrying out variable transmission ratio control: inputting the obtained vehicle speed signal and steering wheel rotation angle signal into an ideal transmission ratio controller, determining a transmission ratio signal according to a preset vehicle speed-steering wheel rotation angle-ideal transmission ratio map, calculating a front wheel rotation angle signal expected at the current moment, and inputting the transmission ratio signal and the steering wheel rotation angle signal into a rotation angle motor rotation angle calculator together to obtain a rotation angle motor ideal rotation angle signal;
3) and (3) carrying out stability control: inputting the obtained vehicle speed signal, yaw rate signal, lateral acceleration signal and mass center and lateral deviation angle signal into a vehicle stability controller, and utilizing H2/H∞A robust control method obtains a vehicle stability control signal; then inputting the obtained vehicle stability control signal, the obtained ideal corner signal of the corner motor and the corner signal of the corner motor into a corner motor controller, converting the front wheel corner to obtain the actual corner of the corner motor, subtracting the ideal corner of the corner motor and the actual corner of the corner motor, and obtaining a real-time corner motor control signal through PID (proportion integration differentiation) setting;
controlling the rotation angle of the rotation angle motor according to the obtained real-time rotation angle motor control signal, driving a harmonic gear mechanism to move, and simultaneously overlapping the rotation angle input to a flexible wheel by a steering wheel to complete variable transmission ratio control and stability control of a steering system and realize the automatic steering of a vehicle driver;
4) controlling a hydraulic pump driving motor: when the diagnosis unit judges that hydraulic assistance is needed, a target hydraulic assistance signal is obtained according to an assistance distribution strategy; the first pressure sensor and the second pressure sensor collect oil pressure on the left side and the right side of the power-assisted oil cylinder, the generated actual hydraulic power-assisted signal is used as feedback, the difference value of the target hydraulic power-assisted signal and the actual hydraulic power-assisted signal is transmitted to the main controller module, and the difference value is transmitted to the main controller module through the H2/H∞The robust control method forms a closed loop; and then through the master controlThe controller module controls the opening of the servo proportional solenoid valve and the torque of a hydraulic pump driving motor so as to generate hydraulic assistance to realize vehicle steering;
5) carrying out electric power-assisted motor control: when the diagnosis unit judges that electric power assistance is needed, a target electric power assistance signal is obtained according to a power assistance distribution strategy, then an actual torque signal generated by a second steering column torque sensor is used as feedback, and an electric power assistance motor controller performs closed-loop control through PID according to the target torque and the actual torque signal to obtain a control signal of an electric power assistance motor;
6) in the running process of a vehicle, a diagnosis unit detects whether an electro-hydraulic steering system works normally and judges the working mode of a motor according to a transmission ratio signal at the current moment, a motor driving unit selects different working modes and a road feel compensation mode of the motor according to an output instruction of a power-assisted decision unit, and simultaneously outputs an electric power-assisted motor control signal and a hydraulic power-assisted motor control signal respectively according to a power-assisted distribution strategy to realize power-assisted distribution;
the power-assisted distribution strategy specifically comprises the following steps: according to the obtained steering wheel torque, the front wheel rotation angle and the transmission ratio signal, the total required power-assisted torque of the steering system is obtained and is determined by the following formulas (1) and (2); wherein when the transmission ratio signal i received by the main controller module is less than or equal to i0When the electric power assisting device is used, the hydraulic power assisting module and the electric power assisting module work simultaneously, wherein the power assisting provided by the hydraulic power assisting module and the power assisting provided by the electric power assisting motor are 3: 2;
Figure BDA0003112053850000121
Figure BDA0003112053850000122
Tz＝Te+Th (3)
in the formula, TzAnd TzmaxRespectively a total required power-assisted torque and a maximum total required power-assisted torque; t isd0，TdAnd TdmaxThe steering wheel torque at the time of starting power assistance, the steering wheel torque and the steering wheel torque at the time of maximum power assistance are respectively; ki(i) Is the transmission ratio inductance; alpha is an assisting force distribution proportion coefficient, and is specifically 0.8-0.95; t isRTo the steering resistance torque, deltafIs the front wheel angle, G is the first reduction gear reduction ratio, i0＝11.5,TeAssistance provided for a hydraulic assistance module, ThThe power assisting device provides power assisting for the electric power assisting motor.
Referring to fig. 3, the step 6) of selecting the operation mode of the motor driving unit specifically includes the following steps:
61) when the corner motor works normally, variable transmission ratio control is carried out, an additional corner is provided by driving the harmonic gear mechanism, linear superposition is carried out on the additional corner and the corner input of the steering wheel, and the additional corner and the corner input are output to a second steering column, so that variable transmission ratio control and stability control are realized;
62) when the vehicle starts, the transmission ratio of the steering system is small, and the transmission ratio i output by the variable transmission ratio driving module is smaller than or equal to the transmission ratio i0The electric power-assisted motor starts to work, the hydraulic power-assisted module starts to work again, the servo proportional solenoid valve is opened, the hydraulic pump drives the motor to work and distributes power-assisted torque, and the hydraulic power-assisted module provides most power for the system;
when the transmission ratio i is less than/equal to the transmission ratio i2And is less than i0When the road is in use, the generated front wheel has a large steering angle, and the driving motor of the hydraulic pump compensates the road feel; when the transmission ratio becomes larger, the transmission ratio i is larger than i2And is less than or equal to i0When the vehicle runs, the road feel is compensated by the electric power-assisted motor;
63) when the vehicle speed is increased, the transmission ratio of the steering system is increased, and the transmission ratio i output by the system variable transmission ratio driving module is larger than the transmission ratio i0Is less than or equal to the transmission ratio i1When the system is used, the electric power-assisted motor stops providing power assistance, and only the hydraulic power-assisted module works to provide steering power assistance for the system; the electric power-assisted motor works only when the steering wheel turns back to compensate the road feel;
64) when the transmission ratio i output by the variable transmission ratio driving module is larger than the transmission ratio i1When the hydraulic power-assisted module stops working, only the electric power-assisted motor provides steering power, and meanwhile, the electric power-assisted motor compensates the road feel;
65) when the corner motor fails, the main controller module cuts off the power supply of a locking electromagnetic valve in the variable transmission ratio module, locks the corner motor and runs at a constant steering transmission ratio, and the electric power-assisted motor and the hydraulic pump drive motor work simultaneously to provide power assistance and trigger a failure alarm unit to remind a driver of failure information;
66) when the hydraulic power-assisted module or the motor power-assisted module breaks down, the other one of the hydraulic power-assisted module and the motor power-assisted module is used for providing power-assisted steering instead of the power-assisted steering, and meanwhile, the fault alarm unit is triggered to remind a driver of fault information;
wherein i2＝4.3，i0＝11.5，i1＝20.8。
The road feel compensation in the step 6) is specifically as follows: inputting the steering wheel torque signal and the transmission ratio signal in the step 3) into a power-assisted decision unit, compensating the road feel change caused by the additional steering angle generated by the steering wheel motor after the variable transmission ratio and the stability control, and reducing the provided power assistance by a hydraulic pump driving motor or an electric power-assisted motor or providing reverse power assistance to achieve the aim of road feel compensation.
When the corner motor is not electrified or fails, the harmonic gear mechanism is locked, and the transmission ratio of the steering system is kept constant; when the rotation angle motor drives the wave generator, the flexible gear is driven to rotate, and when the elliptical rotor and the flexible gear rotate in the same direction, the number of teeth of the flexible gear is less than that of the outer ring rigid gear, so that the transmission ratio of a steering system is reduced; when the elliptical rotor and the flexible gear rotate reversely, the rotation angle of the rigid gear is smaller than that of the flexible gear, the transmission ratio of the steering system is increased, and controllable variable transmission ratio control is realized.
While the invention has been described in terms of its preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims (7)

1. A variable ratio recirculating ball electro-hydraulic steering system, comprising: the device comprises a steering wheel module, a variable transmission ratio hydraulic power-assisted module (5), a mechanical transmission module, a motor power-assisted module and a main controller module (33);
the steering wheel module includes: the steering wheel torque sensor comprises a steering wheel (1), a first steering column (2), a steering wheel angle sensor (3) and a steering wheel torque sensor (4);
the steering wheel (1) is fixedly connected with the first steering column (2);
the steering wheel corner sensor (3) and the steering wheel torque sensor (4) are fixedly connected with the first steering column (2), respectively collect corner and torque signals of a steering wheel, and send the collected signals to the main controller module (33);
the variable transmission ratio hydraulic power assisting module (5) comprises: the steering system comprises a variable transmission ratio module (6), a second steering column (10), a second steering column torque sensor (9), a circulating ball type hydraulic power-assisted steering gear (13) and a hydraulic power-assisted module (22);
the second steering column torque sensor (9) is fixedly connected with the second steering column (10) and is used for acquiring a torque signal of the second steering column (10) and sending the acquired signal to the main controller module (33);
the variable transmission ratio module (6) comprises: the device comprises a corner motor (7), a corner motor corner controller, a corner motor corner sensor (61), a harmonic gear mechanism (8) and a locking mechanism;
the corner motor corner sensor (61) is fixedly connected with the corner motor (7) and is used for acquiring a corner signal of the corner motor (7); the locking mechanism is arranged on the corner motor (7) and used for locking the corner motor when the corner motor does not work or fails; the input end of the corner controller of the corner motor is connected with the main controller module (33), the output end of the corner controller is connected with the corner motor, and the corner controller is used for converting the front wheel corner at the current moment to obtain the actual corner to be output by the corner motor, subtracting the ideal corner of the corner motor from the actual corner of the corner motor to obtain a real-time corner motor control signal and controlling the corner motor;
the harmonic gear mechanism (8) includes: the flexible gear comprises a wave generator (62), a flexible gear (63) and a rigid gear (64); the flexible gear (63) is an external gear, the rigid gear (64) is an internal gear, and a tooth difference exists between the rigid gear (64) and the flexible gear (63); the first steering column (2) is used as an input end and is in gapless connection with the flexible gear (63) through a spline (65) to drive the flexible gear (63) to rotate; the wave generator (62) consists of a rotary part and a flexible bearing; the wave generator (62) is arranged in an inner ring of the flexible gear (63), the outer side surface of the wave generator drives the flexible gear to generate elastic deformation through the flexible bearing, and the flexible gear (63) becomes an elliptic gear and rotates along with the opposite direction of the rotation of the rotary component; the rotary part positioned in the middle of the wave generator (62) is connected with a rotor shaft of the corner motor; the outer teeth of the flexible gear are meshed with the inner teeth of the rigid gear; the rigid wheel is connected with one end of a second steering column (10) in a gapless way through a spline; the other end of the second steering column (10) is connected with a circulating ball type hydraulic power-assisted steering gear (13);
the circulating ball type hydraulic power-assisted steering gear (13) is composed of two-stage transmission pairs: the first stage is a screw and nut transmission pair (11); the second stage is a rack and sector transmission pair (12); the second steering column is connected with a circulating ball type hydraulic power-assisted steering device (13) through a screw and nut transmission pair (11);
the hydraulic boost module (22) comprises: the hydraulic control system comprises a hydraulic pump (31), a hydraulic pump driving motor (30), a hydraulic pump driving motor controller, a first speed reducing mechanism (36), an oil tank (29), a servo proportional solenoid valve (23), an oil pipe, a first pressure sensor (34) and a second pressure sensor (35); the input end of the hydraulic pump driving motor controller is connected with the main controller module (33), the output end of the hydraulic pump driving motor controller is connected with the hydraulic pump driving motor (30) and is used for receiving a hydraulic pump driving motor control signal sent by the main controller module (33) to control the hydraulic pump driving motor (30); the hydraulic pump driving motor (30) is connected with the hydraulic pump (31) through a first speed reducing mechanism (36), hydraulic oil from an oil tank (29) is pumped into the circulating ball type hydraulic power-assisted steering gear (13) through the servo proportional electromagnetic valve, oil pressure difference is formed in the circulating ball type hydraulic power-assisted steering gear (13), and power assistance is provided for a steering system under the action of the oil pressure difference; the first pressure sensor and the second pressure sensor are arranged on an oil pipe of an oil inlet and outlet way of the recirculating ball type hydraulic power steering gear and are used for detecting hydraulic power assistance on two sides of the recirculating ball type hydraulic power steering gear and sending an actual hydraulic power assistance signal;
the mechanical transmission module comprises: the steering mechanism comprises a steering rocker arm (14), a steering drag link (19), a left steering wheel (15), a left steering knuckle (16), a left steering knuckle arm (17), a left steering trapezoid arm (18), a steering tie rod (24), a right steering trapezoid arm (25), a right steering knuckle arm (26), a right steering knuckle (27) and a right steering wheel (28);
the output end of the circulating ball type hydraulic power-assisted steering gear (13) is connected with one ends of a sector transmission pair (12) and a steering rocker arm (14) through a rack, and the other end of the steering rocker arm (14) is connected with a left steering knuckle arm (17) through a steering drag link (19) to drive a left steering knuckle (16) and a left steering wheel (15) to deflect; the left steering knuckle arm (17) is connected with one end of a steering tie rod (24) through a left steering trapezoid arm (18); the other end of the tie rod (24) is connected with a right steering trapezoid arm (25), the right steering trapezoid arm (25) is connected with a right steering knuckle (27) through a right steering knuckle arm (26), and the right steering knuckle drives a right steering wheel (28) to steer;
the motor assist module includes: an electric power motor (20), an electric power motor controller and a second speed reduction mechanism (21); the input end of the electric power-assisted motor controller is connected with the main controller module (33), and the output end of the electric power-assisted motor controller is connected with the electric power-assisted motor (20); the electric power-assisted motor (20) transmits electric power assistance to the second steering column (10) through a second speed reducing mechanism (21) to provide power assistance for a steering system;
the main controller module (33) comprises: the device comprises a signal processing unit, a vehicle other state unit (32), an ideal transmission ratio controller, a corner motor corner calculator, a stability controller, a power-assisted decision unit, a diagnosis unit, a fault alarm unit and a motor driving unit;
the signal processing unit is electrically connected with the sensors, acquires signals acquired by the sensors in real time, and receives a steering wheel corner signal A, a steering wheel torque signal B, a corner motor corner signal C, an actual hydraulic power-assisted signal D and a second steering column torque signal; meanwhile, the signal processing unit is electrically connected with other state units of the vehicle to acquire other state signals of the vehicle;
the other state units of the vehicle are used for acquiring a vehicle speed signal I, a yaw rate signal J, a mass center side deviation angle signal K and a lateral acceleration signal L of the current vehicle state;
the ideal transmission ratio controller is used for determining a transmission ratio signal at the current moment through a preset vehicle speed-steering wheel rotation angle-ideal transmission ratio map according to the vehicle speed signal and the steering wheel rotation angle signal obtained by the signal processing unit and calculating an expected front wheel rotation angle signal at the current moment; inputting the transmission ratio signal and a steering wheel corner signal into a corner motor corner calculator together to obtain an ideal corner signal of a corner motor, and superposing an additional corner provided by the corner motor and a corner of a first steering column to realize variable transmission ratio control;
the stability controller is used for passing through H according to the vehicle speed signal, the yaw rate signal, the lateral acceleration signal and the mass center and lateral deviation angle signal obtained by the signal processing unit2/H∞A robust control method obtains a vehicle stability control signal; inputting the obtained vehicle stability control signal, the obtained ideal corner signal of the corner motor and the corner signal of the corner motor into a corner motor controller, converting the front wheel corner to obtain the actual corner of the corner motor, subtracting the ideal corner of the corner motor and the actual corner of the corner motor, and obtaining a real-time corner motor control signal through PID (proportion integration differentiation) setting;
the output end of the main controller module is respectively electrically connected with a corner motor (7), an electric power-assisted motor (20), a servo proportional solenoid valve (23) and a hydraulic pump driving motor (30) to output a corner motor control signal F and control the corner motor to output a corner; outputting a hydraulic pump driving motor control signal G to control the torque of a hydraulic pump driving motor; outputting a servo proportional solenoid valve control signal H to control the opening of the servo proportional solenoid valve; outputting a control signal M of the electric power-assisted motor to control the output torque of the electric power-assisted motor;
the diagnosis unit detects whether the electro-hydraulic steering system works normally in the running process of the vehicle, compares a transmission ratio signal received by the main controller module with a given transmission ratio threshold value and judges the working mode of each motor;
the power-assisted decision unit receives input signals of the signal processing unit and the diagnosis unit through a vehicle-mounted communication line, and outputs instructions to the motor driving unit through the vehicle-mounted communication line after calculation according to a power-assisted distribution strategy; in the steering wheel aligning process of a steering system, a power-assisted decision unit compensates road feel change caused by an additional steering angle generated by a steering angle motor after variable transmission ratio and stability control according to a steering angle motor control signal, a steering wheel torque signal and a transmission ratio signal, and outputs an instruction to a motor driving unit through a vehicle-mounted communication line after calculation;
the motor driving unit selects different working modes according to an output instruction of the power-assisted decision control unit and respectively outputs a corner motor control signal, an electric power-assisted motor control signal and a hydraulic pump driving motor control signal;
the fault alarm unit is used for reminding a driver of fault information.
2. The variable ratio recirculating ball electro-hydraulic steering system of claim 1, wherein the rotating member profile is a curvilinear profile.
3. The variable transmission ratio recirculating ball type electro-hydraulic steering system according to claim 1, wherein the angle motor is a direct current brushless motor, is packaged in a variable transmission ratio module shell, and consists of a permanent magnet, a coil and a rotor shaft, and the rotor shaft is connected with a wave generator and transmits the torque of the angle motor to the harmonic gear mechanism; the locking mechanism consists of a lock frame fixed on the corner motor, a lock rod arranged on the shell and an electromagnetic valve for enabling the lock rod to act.
4. The variable transmission ratio recirculating ball type electro-hydraulic steering system according to claim 1, wherein the power distribution strategy is to obtain the total required power-assisted torque of the steering system according to the obtained steering wheel torque, the front wheel rotation angle and the transmission ratio signal; wherein when the transmission ratio signal i received by the main controller module is less than or equal to i0The hydraulic power-assisted module and the electric power-assisted module work simultaneously, wherein the hydraulic power-assisted module assistsThe assistance provided by the force module and the assistance provided by the electric assistance motor are 3: 2.
5. A control method of a variable transmission ratio circulating ball type electro-hydraulic steering system based on the system of any one of claims 1-4 is characterized by comprising the following steps:
1) according to the driving condition of the vehicle, inputting a steering wheel corner, and receiving a steering wheel corner signal, a steering wheel torque signal, a vehicle speed signal, a yaw velocity signal, a lateral acceleration signal, a mass center side deviation angle signal, a corner motor corner signal and a second steering column torque signal in real time through a signal processing unit;
2) and (3) carrying out variable transmission ratio control: inputting the obtained vehicle speed signal and steering wheel rotation angle signal into an ideal transmission ratio controller, determining a transmission ratio signal according to a preset vehicle speed-steering wheel rotation angle-ideal transmission ratio map, calculating a front wheel rotation angle signal expected at the current moment, and inputting the transmission ratio signal and the steering wheel rotation angle signal into a rotation angle motor rotation angle calculator together to obtain a rotation angle motor ideal rotation angle signal;
3) and (3) carrying out stability control: inputting the obtained vehicle speed signal, yaw rate signal, lateral acceleration signal and mass center and lateral deviation angle signal into a vehicle stability controller, and utilizing H2/H∞A robust control method obtains a vehicle stability control signal; inputting the obtained vehicle stability control signal, the obtained ideal corner signal of the corner motor and the corner signal of the corner motor into a corner motor controller, converting the front wheel corner to obtain the actual corner of the corner motor, subtracting the ideal corner of the corner motor from the actual corner of the corner motor, and performing PID (proportion integration differentiation) setting to obtain a real-time corner motor control signal;
controlling the rotation angle of the rotation angle motor according to the obtained real-time rotation angle motor control signal, driving a harmonic gear mechanism to move, and simultaneously overlapping the rotation angle input to a flexible wheel by a steering wheel to complete variable transmission ratio control and stability control of a steering system and realize the automatic steering of a vehicle driver;
4) controlling a hydraulic pump driving motor: when diagnosing the unitWhen hydraulic assistance is judged to be needed, a target hydraulic assistance signal is obtained according to an assistance distribution strategy; the first pressure sensor and the second pressure sensor collect oil pressure on the left side and the right side of the power-assisted oil cylinder, the generated actual hydraulic power-assisted signal is used as feedback, the difference value of the target hydraulic power-assisted signal and the actual hydraulic power-assisted signal is transmitted to the main controller module, and the difference value is transmitted to the main controller module through the H2/H∞The robust control method forms a closed loop; the opening of the servo proportional solenoid valve and the torque of a hydraulic pump driving motor are controlled through the main controller module, so that hydraulic power is generated to realize vehicle steering;
5) carrying out electric power-assisted motor control: when the diagnosis unit judges that electric power assistance is needed, a target electric power assistance signal is obtained according to a power assistance distribution strategy, then an actual torque signal generated by a second steering column torque sensor is used as feedback, and an electric power assistance motor controller performs closed-loop control through PID according to the target torque and the actual torque signal to obtain a control signal of an electric power assistance motor;
6) in the running process of a vehicle, the diagnosis unit detects whether the electro-hydraulic steering system works normally or not and judges the working mode of the motor according to a transmission ratio signal at the current moment, the motor driving unit selects different working modes and a road feel compensation mode of the motor according to an output instruction of the power-assisted decision unit, and simultaneously, an electric power-assisted motor control signal and a hydraulic power-assisted motor control signal are respectively output according to a power-assisted distribution strategy, so that power-assisted distribution is realized.
6. The control method of the variable transmission ratio recirculating ball electro-hydraulic steering system according to claim 5, wherein the power-assisted distribution strategy is specifically: according to the obtained steering wheel torque, the front wheel rotation angle and the transmission ratio signal, the total required power-assisted torque of the steering system is obtained and is determined by the following formulas (1) and (2); wherein when the transmission ratio signal i received by the main controller module is less than or equal to i0When the electric power assisting device is used, the hydraulic power assisting module and the electric power assisting module work simultaneously, wherein the power assisting provided by the hydraulic power assisting module and the power assisting provided by the electric power assisting motor are 3: 2;
Figure FDA0003466289340000051
Figure FDA0003466289340000052
Tz＝Te+Th (3)
in the formula, TzAnd TzmaxRespectively a total required power-assisted torque and a maximum total required power-assisted torque; t isd0，TdAnd TdmaxThe steering wheel torque at the time of starting power assistance, the steering wheel torque and the steering wheel torque at the time of maximum power assistance are respectively; ki(i) Is the transmission ratio inductance; alpha is an assisting force distribution proportion coefficient, and is specifically 0.8-0.95; t isRTo the steering resistance torque, deltafIs the front wheel angle, G is the first reduction gear reduction ratio, i0＝11.5，TeAssistance provided for a hydraulic assistance module, ThThe power assisting device provides power assisting for the electric power assisting motor.
7. The control method of the variable transmission ratio recirculating ball electro-hydraulic steering system according to claim 6, wherein the step 6) selection of the operating mode of the motor drive unit specifically comprises the steps of:
61) when the corner motor works normally, variable transmission ratio control is carried out, an additional corner is provided by driving the harmonic gear mechanism, linear superposition is carried out on the additional corner and the corner input of the steering wheel, and the additional corner and the corner input are output to a second steering column, so that variable transmission ratio control and stability control are realized;
62) when the vehicle starts, the transmission ratio of the steering system is small, and the transmission ratio i output by the variable transmission ratio driving module is smaller than or equal to the transmission ratio i0The electric power-assisted motor starts to work, the hydraulic power-assisted module starts to work again, the servo proportional solenoid valve is opened, the hydraulic pump drives the motor to work and distributes power-assisted torque, and the hydraulic power-assisted module provides most power for the system;
when the transmission ratio i is less than or equal to the transmission ratio i2And is less than i0When the road is in use, the generated front wheel has a large steering angle, and the driving motor of the hydraulic pump compensates the road feel; when the transmission ratio becomes larger, the transmission ratio i is larger than i2And is less than or equal to i0When the vehicle runs, the road feel is compensated by the electric power-assisted motor;
63) when the vehicle speed is increased, the transmission ratio of the steering system is increased, and the transmission ratio i output by the system variable transmission ratio driving module is larger than the transmission ratio i0And is less than or equal to the transmission ratio i1When the system is used, the electric power-assisted motor stops providing power assistance, and only the hydraulic power-assisted module works to provide steering power assistance for the system; the electric power-assisted motor works only when the steering wheel turns back to compensate the road feel;
64) when the transmission ratio i output by the variable transmission ratio driving module is larger than the transmission ratio i1When the hydraulic power-assisted module stops working, only the electric power-assisted motor provides steering power, and meanwhile, the electric power-assisted motor compensates the road feel;
65) when the corner motor fails, the main controller module cuts off the power supply of a locking electromagnetic valve in the variable transmission ratio module, locks the corner motor and runs at a constant steering transmission ratio, and the electric power-assisted motor and the hydraulic pump drive motor work simultaneously to provide power assistance and trigger a failure alarm unit to remind a driver of failure information;
66) when the hydraulic power-assisted module or the motor power-assisted module breaks down, the other one of the hydraulic power-assisted module and the motor power-assisted module is used for providing power-assisted steering instead of the power-assisted steering, and meanwhile, the fault alarm unit is triggered to remind a driver of fault information;
wherein i2＝4.3，i0＝11.5，i1＝20.8。
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