CN110962626B - Self-adaptive electronic differential control method for multi-shaft hub motor driven vehicle - Google Patents
Self-adaptive electronic differential control method for multi-shaft hub motor driven vehicle Download PDFInfo
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- B60L15/20—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
- B60L15/2036—Electric differentials, e.g. for supporting steering vehicles
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- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
- B60L15/32—Control or regulation of multiple-unit electrically-propelled vehicles
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- B60—VEHICLES IN GENERAL
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- B60L2220/00—Electrical machine types; Structures or applications thereof
- B60L2220/40—Electrical machine applications
- B60L2220/42—Electrical machine applications with use of more than one motor
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L2220/00—Electrical machine types; Structures or applications thereof
- B60L2220/40—Electrical machine applications
- B60L2220/44—Wheel Hub motors, i.e. integrated in the wheel hub
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
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- B60L2240/00—Control parameters of input or output; Target parameters
- B60L2240/10—Vehicle control parameters
- B60L2240/24—Steering angle
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L2240/00—Control parameters of input or output; Target parameters
- B60L2240/40—Drive Train control parameters
- B60L2240/42—Drive Train control parameters related to electric machines
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- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L2250/00—Driver interactions
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Abstract
The invention provides a self-adaptive electronic differential control method for a multi-shaft hub motor driven vehicle, aims to solve the problems that the electronic differential control of the existing electric wheel driven vehicle cannot adapt to various running working conditions, the motor performance requirement is high and the like, and belongs to an automobile control system. The control method comprises the following steps: s1, establishing an 8 x 8 in-wheel motor independent drive vehicle body motion equation; s2, establishing a wheel vertical jumping model; s3, establishing a wheel rotation dynamics equation; and S4, making a control strategy, and selecting the driving torque as a control parameter to control the motor. The invention has the advantages that the power distribution characteristic of the traditional automobile power transmission is simulated in a mode of motor torque instruction control and rotating speed follow-up, so that the multi-shaft hub motor driven vehicle has better differential performance under three working conditions of steering, uneven road surface and different wheel rolling radiuses, and the accuracy of electronic differential control and the self-adaptive capacity of the system under various working conditions are improved.
Description
Technical Field
The invention belongs to an automobile control system, and particularly relates to a self-adaptive electronic differential control method for a multi-shaft hub motor driven vehicle.
Background
The hub motor independently drives the vehicle, and a transmission system of the traditional vehicle is omitted, and meanwhile, the driving torque of each wheel is independently controllable, and information such as torque, rotating speed and the like can be accurately fed back in real time, so that the transmission efficiency of the whole vehicle is greatly improved, and the arrangement design is more flexible. The electronic differential mainly replaces a mechanical differential of a traditional vehicle, and the electronic differential ensures the operation stability of the vehicle during running by coordinating all driving motors. Because the dead weight and the load of the multi-shaft heavy vehicle are large, the running working condition is complex and changeable, and the differential problem is relatively more prominent and serious, the self-adaptive capacity of the hub motor electronic differential controller is also required to be higher. A balance equation is established according to the actual stress state of each wheel of the multi-axis in-wheel motor driven vehicle, and meanwhile, the requirements of the differential performance of the whole vehicle under various running working conditions are considered, so that the self-adaptive electronic differential control method of the multi-axis in-wheel motor driven vehicle is provided, the accuracy of the electronic differential control of the in-wheel motor and the self-adaptive capacity of system control are further improved, the electronic differential control strategy is guaranteed to be capable of adapting to various differential working conditions, and the differential performance is better.
Some vehicle enterprises in japan, europe, america, etc. such as honda, audi, general, etc. successively apply the electronic differential system to the in-wheel motor driven vehicle. In recent years, domestic researchers have also conducted relevant research on electronic differential control systems in order to fully utilize the outstanding advantages of electronic differential systems to meet actual driving needs. For example, Chinese patent publication No. CN110116635A, publication No. 2019-08-13, discloses an electronic differential control method for a two-wheel independent drive vehicle. The control method is based on a double-wheel independent driving system, the driving wheels on two sides output basically the same driving torque by adjusting the rotating speed difference of two motors, and good turning differential speed can be realized. Chinese patent publication No. CN108177693A, publication No. 2018-06-19, discloses an electronic differential control system of a hub-driven electric automobile. The system calculates the target rotating speeds of the inner and outer driving wheels through the measured wheel steering angle and the target driving speed, and completes closed-loop control on the rotating speed of the driving wheels through the deviation calculation with the actual rotating speed, so that the actual speed of the driving wheels follows the target speed, and differential control is realized. According to the invention, aiming at the requirements of the differential performance of the whole vehicle under various running conditions, the motor torque control is realized by carrying out closed-loop feedback on the rotating speed signal of the hub motor, and the power distribution characteristic from a power system to a differential mechanism of the traditional vehicle is simulated, so that the multi-shaft hub motor driven vehicle realizes better differential performance under various running conditions, and has stronger robustness and adaptability.
Disclosure of Invention
The invention aims to solve the technical problems that an electronic differential control system of the existing multi-axis in-wheel motor driven vehicle cannot realize differential coordination of all wheels under various working conditions, cannot ensure that the system can realize self-adaptive control and the like, and provides a self-adaptive electronic differential control method of the multi-axis in-wheel motor driven vehicle.
In order to solve the technical problems, the invention adopts the following technical scheme: comprises the following steps:
1. a self-adaptive electronic differential control method of a multi-shaft hub motor driven vehicle is characterized by comprising the following steps:
firstly, establishing an 8 multiplied by 8 wheel hub motor independent driving vehicle motion equation;
establishing a coordinate system according to the longitudinal, lateral, vertical, yaw, pitch and roll motion of the vehicle body with 6 degrees of freedom, wherein the positive direction of an x axis is positive forwards along the longitudinal symmetrical line of the vehicle body; the y-axis is positive to the right along the transverse position of the automobile through the mass center; the z axis is vertically downward positive according to the right hand rule; establishing a vehicle body motion equation;
the method comprises the following steps of considering the interaction force of a suspension and a wheel on the basis of the stress of the wheel of a traditional vehicle, and establishing a wheel rotation dynamic equation as shown in a formula (1):
in the formula:Iw-moment of inertia of the wheel
Tq-wheel drive torque
FdLongitudinal forces between the tyre and the ground
TbBraking torque
Mω-wheel mass
Xi-coefficient of action
In the formula (1), the last term on the right side of the equation is the counterforce formed on the ground by the action of the wheel shaft on the wheel center of the driven wheel, the problem of dynamics of the driving wheel and the driven wheel can be simultaneously expressed by the supplementary term in the formula (1), and xi is determined by the formula (2):
secondly, calculating the actual movement speed of the wheel center of the wheel;
calculating the horizontal movement speed of the wheel center by using the formula (3):
in the formula: v. ofhiHorizontal movement velocity of the wheel center of each wheel
u-longitudinal speed of vehicle body
v-lateral velocity of vehicle body
r-vehicle body yaw rate
LiThe distance of the axes to the centre of mass in the plane
δi-deflection angle of each wheel
The vertical movement speed w of the wheel center is calculated by the formula (4)ui:
In the formula: muiUnsprung masses at each wheel
wui-vertical movement speed of wheel center
KuiVertical stiffness of the tyre
Zri-unevenness of the road surface on which the wheels are located
ZuiHeight of center of mass of wheel
CuiVertical damping of the tire
wri-rate of change of road surface unevenness at wheels
Fvi-forces acting on the suspension in the direction of the z-axis from the wheels
Bi-structural parameters of the suspension
Calculating the actual movement velocity v at the wheel center of the wheel by using the formula (5)wi:
Thirdly, calculating the comprehensive vehicle speed;
obtaining the expected speed value V of the driver according to the accelerator-vehicle speed table look-upR(ii) a Calculating to obtain the actual speed V of the vehicle by using the rotating speed of the wheelsZ(ii) a And performing weighted calculation according to the obtained driver expected speed value and the vehicle actual speed value to obtain a comprehensive speed value, as shown in formula (6):
VT=AVR+BVZ (6)
in the formula: vT-integrated vehicle speed
A. B is a weighting coefficient, and is calibrated through experiments;
fourthly, calculating target torque of each driving motor;
taking the opening degree of an accelerator pedal and the current steering wheel angle as control inputs, and obtaining the expected speed of each wheel center by utilizing the geometrical relationship of the structure of the vehicle according to the comprehensive vehicle speed value calculated by the formula (6); and inputting the calculated actual speed at the wheel center of the wheel and the expected speed at the wheel center of each wheel into a PID controller, and calculating the target torque of each driving motor by using an equation (7):
TTi=KP(vTi-vwi)+KI(vTi-vwi)+KD(vTi-vwi) (7)
in the formula: t isTi-target torques of the drive motors
vTi-desired speed at the wheel center of each wheel
KP、KI、KD-PID controller parameters, calibrated by experiment;
the actual rotating speed of the wheels is determined by the balance point of the driving torque of the motor and the stress of the actual wheels, and is fed back to the whole vehicle controller to realize closed loop, the self-adaptive differential speed of each wheel is realized according to the strategy of torque instruction control and rotating speed follow-up, and the whole vehicle control system outputs a driving motor torque instruction signal according to the motion state of the vehicle, so that the accelerator pedal controls the vehicle speed and the motor torque at the same time; the motor torque can be controlled by open loop or closed loop feedback.
The wheel differential operating conditions include: A. when the vehicle is steered to run, the vehicle generates yaw motion, so that the acceleration at the wheel center of each wheel generates difference, and the wheel speed of each wheel is different; B. when the vehicle runs on an uneven road surface, the lengths of tracks passed by the wheel centers of the wheels are different, so that the rotating speeds of the wheels are different; C. when the rolling radius of each wheel is different, the rotating speed of each wheel is different because each wheel core passes through the same track length.
2. The electronic differential control system includes: the system comprises a main controller, hub motors, a controller system and a CAN bus communication network.
Compared with the prior art, the invention has the beneficial effects that:
1. the self-adaptive electronic differential control method of the multi-shaft hub motor driven vehicle can adapt to various running working conditions by adopting the torque instruction control and the rotating speed follow-up mode of the hub motor, so that the wheels freely rotate according to the self stress state, and the self-adaptive electronic differential control method has better differential performance and strong robustness;
2. according to the self-adaptive electronic differential control method for the multi-shaft hub motor driven vehicle, disclosed by the invention, the motor torque control is realized by carrying out closed-loop feedback on the rotating speed signal of the hub motor, the power distribution characteristic from a power system to a differential mechanism of a traditional vehicle can be simulated, the control mode of the electronic differential system is more reasonable, and the characteristic of independent drive of the hub motor is fully exerted;
3. according to the self-adaptive electronic differential control method for the multi-shaft in-wheel motor driven vehicle, the interaction force of the suspension and the wheel and the problems of the driving wheel and the driven wheel are considered on the basis of the stress of the wheel of the traditional vehicle, a wheel rotation dynamic equation capable of reflecting the influence of the driving, braking and road surface effects of the driving wheel and the interaction between the vehicle body and the wheel on the motion of the driven wheel is established, and the rotation dynamic analysis requirement of the wheel independently driven by the in-wheel motor is fully met.
Drawings
The invention is further described below with reference to the accompanying drawings:
FIG. 1 is a flow chart of an adaptive electronic differential control method for a multi-axle hub motor driven vehicle according to the present invention;
FIG. 2 is a schematic view of a wheel complete rotation dynamic model of a multi-axle hub motor driven vehicle according to the invention;
fig. 3 is a schematic diagram of a suspension model of a multi-axle hub motor driven vehicle according to the invention.
Detailed Description
The invention is described in detail below with reference to the attached drawing figures:
the invention discloses a self-adaptive electronic differential control method of a multi-shaft in-wheel motor driven vehicle, which utilizes deviation values of expected vehicle speed and wheel speed signals of a driver to obtain target torque of a driving motor, carries out torque control on each wheel and feeds back actual rotating speed of the wheel to a vehicle control unit to form closed-loop control, thereby realizing control of torque instructions and rotating speed follow-up of the in-wheel motor, simulating power distribution characteristics from a power system to a differential mechanism of a traditional vehicle, effectively avoiding the slip phenomenon of each wheel due to the differential problem, and ensuring that the multi-shaft in-wheel motor driven vehicle has better differential performance under three running conditions of different steering, uneven road surfaces and wheel rolling radiuses.
Referring to fig. 1, the adaptive electronic differential control method for a multi-axle hub motor-driven vehicle according to the present invention mainly includes: establishing an 8 x 8 hub motor independent drive vehicle body motion equation; calculating the actual movement speed of the wheel center of the wheel; calculating a comprehensive vehicle speed; and calculating the target torque of each driving motor. The following step specifically describes an adaptive electronic differential control method for a multi-shaft hub motor driven vehicle.
Comprises the following steps:
firstly, establishing an 8 multiplied by 8 hub motor independent drive vehicle body motion equation;
establishing a coordinate system according to the longitudinal, lateral, vertical, yaw, pitch and roll motion of the vehicle body with 6 degrees of freedom, wherein the x axis is positive forwards along the longitudinal symmetrical line of the vehicle body; the y-axis passes through the center of mass and is positive to the right along the transverse position of the automobile; the z-axis is positive vertically downward according to the right hand rule. According to the stress condition of the vehicle, the influence between the motions in all directions is comprehensively considered, and the motion equation of the vehicle body is calculated by the following equations (1), (2), (3), (4), (5) and (6):
longitudinal movement
Lateral movement
Vertical movement
In the formula: mt-total mass of the vehicle
u-longitudinal speed of vehicle body
v-lateral velocity of vehicle body
w-vehicle body vertical velocity
r-vehicle body yaw rate
p-vehicle body roll angular velocity
q-vehicle body pitch angular velocity
MsSprung mass
h' -distance from center of mass of sprung mass to roll axis
FfTotal running resistance
Fxi-forces acting on the suspension in the direction of the x-axis from the wheels
Fyi-forces acting on the suspension in the direction of the y-axis from the wheels
Fvi-forces acting on the suspension in the direction of the z-axis from the wheels
Bi-structural parameters of the suspension
Pitching movement
Transverse swinging motion
Roll motion
In the formula: i isxxsMoment of inertia of sprung mass about x-axis
IyysMoment of inertia of sprung mass about y-axis
IzzsMoment of inertia of sprung mass about z-axis
IxxMoment of inertia of the entire vehicle about the x-axis
IyyMoment of inertia of the entire vehicle about the y-axis
IzzMoment of inertia of the vehicle about the z-axis
Ai-structural parameters of the suspension
T-wheel track
LiThe distance of the axes to the centre of mass in the plane
Phi-vehicle body side inclination angle
Referring to fig. 2, the dynamic model of the complete rotation of the vehicle wheel driven by the multi-shaft in-wheel motor according to the invention is shown schematically. Using equation (7), the angular acceleration of the driven wheel at the wheel center contact point p during non-braking is calculated:
in the formula: omegapAngular velocity of the wheel centre point of contact p
rωWheel rolling radius
vω-wheel center velocity
The wheel rotation angular acceleration and the angular acceleration at the wheel center around the ground point are equal, and equation (7) can be expressed as equation (8):
in the formula: omegao-angular velocity of wheel rotation
The method comprises the following steps of considering the interaction force of a suspension and a wheel on the basis of the stress of the wheel of a traditional vehicle, and establishing a wheel rotation dynamic equation as shown in a formula (9):
in the formula: i isw-moment of inertia of wheel
Tq-wheel drive torque
FdLongitudinal forces between the tyre and the ground
Tb-braking torque
Mω-wheel mass
Xi-coefficient of action
In the formula (9), the last term on the right side of the equation is the counterforce formed on the ground by the action of the wheel shaft on the wheel center of the driven wheel, the problem of dynamics of the driving wheel and the driven wheel can be simultaneously expressed by the formula (9) through the supplementary term, and the xi value is determined by the formula (10)
Secondly, calculating the actual movement speed of the wheel center of the wheel;
calculating the horizontal movement speed of the wheel center by using the formula (11):
in the formula: v. ofhiHorizontal movement velocity of the wheel center of each wheel
δi-deflection angle of each wheel
Referring to fig. 3, the multi-shaft in-wheel motor driven vehicle adopts a Macpherson independent suspension, wherein C' is a sprung mass center of mass; k isui、KsiVertical stiffness of each tire and suspension; cui、CsiRespectively corresponding damping; zriUnevenness of a road surface on which the wheels are located; zuiIs the height of the mass center of each wheel; z is a linear or branched membersIs the sprung mass centre of mass height; a isi、bi、diIs a suspension geometry parameter. The vertical wheel runout is calculated according to the formula (12):
in the formula: muiUnsprung masses at each wheel
wui-vertical speed of movement of wheels
wri-rate of change of road surface unevenness at wheels
In the formulae (3), (4), (6), (12)Suspension structural parameter Ai、BiCalculated by the following formulas (13), (14), respectively:
calculating the actual velocity v at the wheel center of the wheel using equation (15)wi:
Thirdly, calculating the comprehensive vehicle speed;
obtaining the expected speed value V of the driver according to the accelerator-vehicle speed table look-upR(ii) a Calculating to obtain the actual speed V of the vehicle by using the rotating speed of the wheelsZ(ii) a And performing weighted calculation according to the obtained driver expected speed value and the vehicle actual speed value to obtain a comprehensive speed value, as shown in formula (16):
VT=AVR+BVZ (16)
in the formula: vT-integrated vehicle speed
A. B is a weighting coefficient, and is calibrated through experiments;
fourthly, calculating target torque of each driving motor;
taking the opening degree of an accelerator pedal and the current steering wheel angle as control inputs, and obtaining the expected speed of each wheel center by utilizing the geometrical relationship of the structure of the vehicle according to the comprehensive vehicle speed value calculated by the formula (16); inputting the calculated actual speed at the wheel center and the expected speed at each wheel center into a PID controller, and calculating each driving motor target torque by using an equation (17):
TTi=KP(vTi-vwi)+KI(vTi-vwi)+KD(vTi-vwi) (17)
in the formula: t isTi-target torques of the drive motors
vTi-desired speed at the wheel center of each wheel
KP、KI、KD-PID controller parameters, calibrated by experiment;
the actual rotating speed of the wheels is determined by the balance point of the driving torque of the motor and the stress of the actual wheels, and is fed back to the whole vehicle controller to realize closed loop, the self-adaptive differential speed of each wheel is realized according to the strategy of torque instruction control and rotating speed follow-up, and the whole vehicle control system outputs a driving motor torque instruction signal according to the motion state of the vehicle, so that the accelerator pedal controls the vehicle speed and the motor torque at the same time; the motor torque can be controlled by open loop or closed loop feedback.
The invention discloses a self-adaptive electronic differential control method of a multi-shaft hub motor driven vehicle, which is characterized in that the wheel differential working condition comprises the following steps: A. when the vehicle is steered to run, the vehicle generates yaw motion, so that the acceleration at the wheel center of each wheel generates difference, and the wheel speed of each wheel is different; B. when the vehicle runs on an uneven road surface, the lengths of tracks passed by the wheel centers of the wheels are different, so that the rotating speeds of the wheels are different; C. when the rolling radius of each wheel is different, the rotating speed of each wheel is different because each wheel center passes through the same track length.
The invention discloses a self-adaptive electronic differential control method of a multi-shaft hub motor driven vehicle, which is characterized in that an electronic differential control system comprises: the system comprises a main controller, hub motors, a controller system and a CAN bus communication network.
Claims (3)
1. A self-adaptive electronic differential control method of a multi-shaft hub motor driven vehicle is characterized by comprising the following steps:
firstly, establishing an 8 multiplied by 8 hub motor independent driving vehicle motion equation;
establishing a coordinate system according to 6 degrees of freedom of longitudinal, lateral, vertical, yaw, pitch and roll motions of the vehicle body, wherein the positive direction of the x axis is positive along the longitudinal symmetric line of the vehicle body; the y-axis is positive to the right along the transverse position of the automobile through the mass center; the z axis is vertically downward positive according to the right hand rule; establishing a vehicle body motion equation;
the method comprises the following steps of considering the interaction force of a suspension and a wheel on the basis of the stress of the wheel of a traditional vehicle, and establishing a wheel rotation dynamic equation as shown in a formula (1):
in the formula: I.C. Aw-moment of inertia of the wheel
Tq-wheel drive torque
FdLongitudinal forces between the tyre and the ground
Tb-braking torque
Mω-wheel mass
Xi-coefficient of action
rωWheel rolling radius
vω-wheel center velocity
ωo-angular velocity of wheel rotation
In the formula (1), the last term on the right side of the equation is the counterforce formed on the ground by the action of the wheel shaft on the wheel center of the driven wheel, the driving wheel and the driven wheel dynamics problem can be simultaneously represented by the formula (1), and xi is determined by the formula (2):
secondly, calculating the actual movement speed of the wheel center of the wheel;
calculating the horizontal movement speed of the wheel center by using the formula (3):
in the formula: v. ofhi-wheel centers of respective wheelsSpeed of horizontal movement
u-longitudinal speed of vehicle body
v-lateral velocity of vehicle body
r-vehicle body yaw rate
LiDistances of the axes to the centre of mass in the plane
δi-deflection angle of each wheel
The vertical movement speed w of the wheel center is calculated by the formula (4)ui:
In the formula: muiUnsprung masses at each wheel
wui-vertical movement speed of wheel center
KuiVertical stiffness of the tire
Zri-unevenness of the road surface on which the wheels are located
ZuiHeight of center of mass of wheel
CuiVertical damping of the tire
wri-rate of change of road surface unevenness at wheels
Fvi-forces acting on the suspension in the direction of the z-axis from the wheels
Bi-suspension structural parameters
Calculating the actual movement velocity v at the wheel center of the wheel by using the formula (5)wi:
Thirdly, calculating the comprehensive vehicle speed;
obtaining the expected speed value V of the driver according to the accelerator-vehicle speed table look-upR(ii) a Calculating to obtain the actual speed V of the vehicle by using the rotating speed of the wheelsZ(ii) a Carrying out weighting calculation according to the obtained expected vehicle speed value of the driver and the actual vehicle speed value of the vehicle to obtain the comprehensive vehicle speedThe value, as shown in equation (6):
VT=AVR+BVZ (6)
in the formula: vT-integrated vehicle speed
A. B is a weighting coefficient, and is calibrated through experiments;
fourthly, calculating target torque of each driving motor;
taking the opening degree of an accelerator pedal and the current steering wheel angle as control inputs, and obtaining the expected speed of each wheel center by utilizing the geometrical relationship of the structure of the vehicle according to the comprehensive vehicle speed value calculated by the formula (6); inputting the calculated actual speed at the wheel center and the expected speed at each wheel center into a PID controller, and calculating the target torque of each driving motor by using an equation (7):
TTi=KP(vTi-vwi)+KI(vTi-vwi)+KD(vTi-vwi) (7)
in the formula: t isTi-target torques of the drive motors
vTi-desired speed at the wheel center of each wheel
KP、KI、KD-PID controller parameters, calibrated by experiment;
the actual rotating speed of the wheels is determined by the balance point of the driving torque of the motor and the stress of the actual wheels, and is fed back to the whole vehicle controller to realize closed loop, the self-adaptive differential speed of each wheel is realized according to the strategy of torque instruction control and rotating speed follow-up, and the whole vehicle control system outputs a driving motor torque instruction signal according to the motion state of the vehicle, so that the accelerator pedal controls the vehicle speed and the motor torque at the same time; the motor torque can be controlled by open loop or closed loop feedback.
2. The adaptive electronic differential control method for a multi-axle in-wheel motor-driven vehicle according to claim 1, wherein the wheel differential operation comprises: A. when the vehicle is steered to run, the vehicle generates yaw motion, so that the acceleration at the wheel center of each wheel generates difference, and the wheel speed of each wheel is different; B. when the vehicle runs on an uneven road surface, the lengths of tracks passed by the wheel centers of the wheels are different, so that the rotating speeds of the wheels are different; C. when the rolling radius of each wheel is different, the rotating speed of each wheel is different because each wheel core passes through the same track length.
3. An adaptive electronic differential control method for a multi-axis in-wheel motor-driven vehicle according to claim 1, wherein the electronic differential control system comprises: the device comprises a main controller, hub motors, a controller system and a CAN bus communication network.
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