CN113775755B - Optimal dynamic control method and system for hydraulic stepless transmission - Google Patents

Optimal dynamic control method and system for hydraulic stepless transmission Download PDF

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CN113775755B
CN113775755B CN202111141234.4A CN202111141234A CN113775755B CN 113775755 B CN113775755 B CN 113775755B CN 202111141234 A CN202111141234 A CN 202111141234A CN 113775755 B CN113775755 B CN 113775755B
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hydraulic
displacement
current
hydraulic pump
hydraulic motor
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CN113775755A (en
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吴维
潘丰
罗俊林
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Beijing Institute of Technology BIT
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/42—Control of exclusively fluid gearing hydrostatic involving adjustment of a pump or motor with adjustable output or capacity
    • F16H61/425—Motor capacity control by electric actuators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/14—Inputs being a function of torque or torque demand
    • F16H59/24—Inputs being a function of torque or torque demand dependent on the throttle opening
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/68—Inputs being a function of gearing status
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/74—Inputs being a function of engine parameters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/42—Control of exclusively fluid gearing hydrostatic involving adjustment of a pump or motor with adjustable output or capacity
    • F16H61/435—Pump capacity control by electric actuators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/68—Inputs being a function of gearing status
    • F16H2059/6838—Sensing gearing status of hydrostatic transmissions
    • F16H2059/6846—Sensing gearing status of hydrostatic transmissions the flow in hydrostatic transmissions circuits, e.g. high, low or differential pressures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/68—Inputs being a function of gearing status
    • F16H2059/6838—Sensing gearing status of hydrostatic transmissions
    • F16H2059/6853—Sensing gearing status of hydrostatic transmissions the state of the transmission units, i.e. motor or pump capacity, e.g. for controlled shifting of range gear
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/68—Inputs being a function of gearing status
    • F16H2059/6838—Sensing gearing status of hydrostatic transmissions
    • F16H2059/6876—Sensing gearing status of hydrostatic transmissions the motor speed

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Fluid Gearings (AREA)
  • Control Of Transmission Device (AREA)

Abstract

The application discloses a method and a system for controlling optimal dynamic property of a hydraulic stepless speed changer, wherein the method comprises the following steps: obtaining the current displacement of the hydraulic pump and the hydraulic motor according to the opening of the accelerator and the rotating speed of the hydraulic motor; obtaining a target speed ratio according to the current discharge capacities of a hydraulic pump and the hydraulic motor; obtaining a target displacement of the hydraulic motor and a target displacement of the hydraulic pump according to the target speed ratio and the actual speed ratio; and controlling the current of the hydraulic motor and the current of the hydraulic pump according to the relation between the target displacement of the hydraulic motor and the target displacement and the current of the hydraulic pump, and finishing the optimal dynamic control of the hydraulic continuously variable transmission. The maximum power performance of the vehicle can be realized on the basis of fully considering the characteristics of the hydraulic system and the output characteristics of the engine; the method has the advantages that the condition of the all-terrain road is complex and changeable, the actual speed ratio of the vehicle can be kept to follow the target speed ratio, and the realization of the maximum power capacity is further guaranteed.

Description

Optimal dynamic control method and system for hydraulic stepless transmission
Technical Field
The application belongs to the technical field of vehicle speed change control, and particularly relates to a method and a system for controlling optimal dynamic property of a hydraulic stepless transmission.
Background
The conventional automatic transmission for the vehicle mainly comprises a hydraulic Automatic Transmission (AT), a mechanical automatic transmission (AMT), a Dual Clutch Transmission (DCT) and a metal belt type Continuously Variable Transmission (CVT), wherein the transmissions are generally called mechanical transmissions, and corresponding automatic gear shifting control methods are relatively mature, so that the vehicle can obtain a proper running gear by properly compromising the dynamic property and the economical property, and a gear shifting strategy with priority on the dynamic property or a gear shifting strategy with priority on the economical property can be selected according to the personalized requirements of a driver.
However, the hydraulic stepless transmission is significantly different from the above mechanical automatic transmission, because the engine and the wheels are not directly mechanically connected in the hydraulic stepless transmission, the power of the engine is firstly converted into hydraulic energy by the hydraulic pump, and then the hydraulic energy is converted into mechanical energy by the hydraulic motor and is output to the wheels, and the rotating speed relationship between the hydraulic pump and the hydraulic motor is changed along with the displacement and the volumetric efficiency, therefore, compared with the mechanical automatic transmission, the hydraulic stepless transmission can realize the function of decoupling the engine and the wheels, the off-road vehicle has complex driving road conditions and severe driving resistance change, the hydraulic stepless transmission system can have good overload protection capability and wider speed regulation capability, and the vehicle can cope with the complex road conditions. The dynamic performance is a key technical index for evaluating the vehicle, and the acceleration capacity of the vehicle is often used as an evaluation parameter, so that how to develop and design a set of optimal dynamic performance control method for the vehicle provided with the hydraulic stepless transmission is of great significance.
Disclosure of Invention
The application provides an optimal dynamic control method and system for a hydraulic stepless transmission, which are used for calculating the optimal economic speed ratio and the optimal dynamic speed ratio of the hydraulic stepless transmission under different accelerator opening degrees and different running speeds on the basis of vehicle parameters including the characteristics of a power device, the parameters of mechanical parts and hydraulic parts of a transmission system, the quality of a finished vehicle, the radius of wheels and the like.
In order to achieve the above purpose, the present application provides the following solutions:
an optimal dynamics control method of a hydraulic continuously variable transmission, comprising the steps of:
according to the accelerator opening of the engine and the current rotating speed of the hydraulic motor, the current displacement of the hydraulic pump and the current displacement of the hydraulic motor under the corresponding rotating speed of the hydraulic motor are obtained;
obtaining a target speed ratio according to the current displacement of the hydraulic pump and the current displacement of the hydraulic motor;
obtaining the target displacement of a hydraulic motor of the hydraulic motor and the target displacement of a hydraulic pump of the hydraulic pump according to the target speed ratio and the collected actual speed ratio;
and controlling the current of the hydraulic motor and the current of the hydraulic pump according to the relation between the target displacement of the hydraulic motor and the target displacement and the current of the hydraulic pump, and finishing the optimal dynamic control of the hydraulic continuously variable transmission.
Preferably, the method for obtaining the current displacement of the hydraulic pump and the current displacement of the hydraulic motor comprises the following steps:
obtaining the maximum pressure of a hydraulic system which can be reached by the hydraulic system according to the accelerator opening and the maximum output torque of the engine, and obtaining the maximum output flow of the hydraulic pump based on the maximum pressure of the hydraulic system;
according to the engine speed and the displacement of the hydraulic pump, the working speeds of the hydraulic motor under different working conditions are obtained, and the working conditions comprise: the hydraulic pump is in a state when the hydraulic pump is in the maximum output flow, a state when the displacement of the hydraulic motor is minimum and a state when the rotating speed of an engine is maximum;
and obtaining the current displacement of the hydraulic pump and the current displacement of the hydraulic motor at the current motor rotating speed according to the accelerator opening, the current motor rotating speed and the working rotating speed of the hydraulic motor.
Preferably, the maximum output flow Q of the hydraulic pumpmaxComprises the following steps:
Figure BDA0003284027490000031
wherein, VpIs the displacement of the hydraulic pump, neAs the engine speed, ieFor reduction ratio, η, between engine output and hydraulic pumppvIs the volumetric efficiency of the hydraulic pump.
Preferably, the method for calculating the working rotating speed of the hydraulic motor under different working conditions comprises the following steps:
the working speed n of the hydraulic motor when the hydraulic pump is in the state of the maximum output flow of the hydraulic pumpm0Is composed of
Figure BDA0003284027490000032
Wherein n ise0Is the current speed of the engine, Vp0Is the current displacement, η, of the hydraulic pumpmvFor volumetric efficiency of the hydraulic motor, Vm,maxIs the maximum displacement of the hydraulic motor;
the working speed n of the hydraulic motor in the state of the minimum displacement of the hydraulic motorm1Is composed of
Figure BDA0003284027490000033
Wherein, Vm,minIs the minimum effective displacement of the hydraulic motor;
working speed n of hydraulic motor in state of maximum engine speedm2Is composed of
Figure BDA0003284027490000041
Wherein n ise,maxThe maximum engine speed.
Preferably, the current motor speed nmIs nm<nm0When the displacement of the hydraulic motor is at a maximum value Vm,maxThe displacement of the hydraulic pump is calculated according to the following formula,
Figure BDA0003284027490000042
current motor speed nmIs nm0<nm<nm1The displacement of the hydraulic motor is calculated by the following formula,
Figure BDA0003284027490000043
current hydraulic motor speed nmIs nm1<nm<nm2When the displacement of the hydraulic pump is kept at V, the hydraulic motor is at the minimum displacement Vm, minp0；
Current hydraulic motor speed nmIs nm>nm2When the displacement of the hydraulic pump is calculated according to the following formula,
Figure BDA0003284027490000044
wherein, Vm,minIs hydraulic pressureMinimum effective displacement of the motor, ne,maxThe maximum engine speed.
Preferably, the target speed ratio id(a，nm) Is composed of
Figure BDA0003284027490000045
Wherein a is the accelerator opening.
Preferably, the method of obtaining the target displacement of the hydraulic motor and the target displacement of the hydraulic pump includes:
performing closed-loop correction on the target speed ratio and the actual speed ratio to obtain corrected output, wherein the actual speed ratio iaComprises the following steps:
Figure BDA0003284027490000051
wherein n ispThe rotating speed of the hydraulic pump;
converting the corrected output into the hydraulic motor target displacement and the hydraulic pump target displacement.
Preferably, the target displacement of the hydraulic motor is
Figure BDA0003284027490000052
The target displacement of the hydraulic pump
Figure BDA0003284027490000053
The application also discloses an optimal dynamic control system of the hydraulic stepless transmission, which comprises a hydraulic pump motor current displacement module, a target speed ratio module, a hydraulic pump motor target displacement module and a current control module which are sequentially connected;
the hydraulic pump current displacement module is used for obtaining the current displacement of the hydraulic pump and the current displacement of the hydraulic motor under the corresponding rotating speed of the hydraulic motor according to the accelerator opening of the engine and the current rotating speed of the hydraulic motor;
the target speed ratio module is used for obtaining a target speed ratio according to the current displacement of the hydraulic pump and the current displacement of the hydraulic motor;
the hydraulic pump motor target displacement module is used for obtaining the hydraulic motor target displacement of the hydraulic motor and the hydraulic pump target displacement of the hydraulic pump according to the target speed ratio and the collected actual speed ratio;
the current control module is used for controlling the current of the hydraulic motor and the current of the hydraulic pump according to the relation between the target displacement of the hydraulic motor and the target displacement of the hydraulic pump and the current, and the current of the hydraulic motor and the current of the hydraulic pump are used for controlling the power of the hydraulic stepless transmission.
The beneficial effect of this application does:
the application discloses an optimal dynamic control method and system for a hydraulic stepless transmission, which can realize the maximum dynamic performance of a vehicle by calculating the optimal economic speed ratio and the optimal dynamic speed ratio of the hydraulic stepless transmission under different accelerator opening degrees and different running speeds on the basis of fully considering the characteristics of a hydraulic system and the output characteristics of an engine; in consideration of the fact that the all-terrain road conditions are complex and changeable, the actual speed ratio of the vehicle can be kept to follow the target speed ratio by adopting a feedforward and speed ratio closed-loop control method, and then the realization of the maximum power capacity is guaranteed.
Drawings
In order to more clearly illustrate the technical solution of the present application, the drawings needed to be used in the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without inventive exercise.
FIG. 1 is a flow chart of a new method for controlling optimal dynamics of a hydraulic continuously variable transmission according to a first embodiment of the present application;
FIG. 2 is a schematic diagram illustrating the relationship between the displacement of the hydraulic pump and the hydraulic motor and the rotation speed of the hydraulic motor when the calculated accelerator opening a is equal to 1 according to the first embodiment of the present application;
FIG. 3 is a schematic flow chart of a closed loop control according to a first embodiment of the present application;
FIG. 4 is a schematic diagram of an output torque of a hydraulic motor in a process of controlling full-throttle acceleration of a vehicle by using a control method according to a first embodiment of the present application;
fig. 5 is a schematic structural diagram of an optimal dynamics control system of a hydraulic continuously variable transmission according to a second embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, the present application is described in further detail with reference to the accompanying drawings and the detailed description.
Example one
Referring to fig. 1, a flow chart of a method for controlling optimal dynamics of a new hydraulic continuously variable transmission provided by an embodiment of the present application is shown, and the method is mainly divided into a calculation part and a control part, which are described below in the form of specific embodiments.
The first part, the calculation part.
In the first embodiment, first, the power parameters of the vehicle, including the power plant characteristics, the parameters of the mechanical components and hydraulic components of the transmission system, the vehicle mass, the wheel radius, etc., are set, and the key parameter settings of the first embodiment are shown in table 1.
TABLE 1
Figure BDA0003284027490000081
S1, obtaining the current displacement of a hydraulic pump and the current displacement of a hydraulic motor when the hydraulic motor is at the corresponding rotating speed according to the accelerator opening of the engine and the current rotating speed of the hydraulic motor.
The method mainly comprises the following three steps:
s1.1, obtaining the maximum pressure of a hydraulic system which can be achieved by the hydraulic system according to the accelerator opening and the maximum output torque of the engine, and obtaining the maximum output flow of the hydraulic pump based on the maximum pressure of the hydraulic system.
In the first embodiment, the engine throttle opening is set to a, and the maximum output torque of the engine corresponding to a is set to TemaxSetting the maximum pressure of the hydraulic system to be Pmax. For example, the following steps are carried out: when the accelerator opening is calculated to be 1, according to the parameters in table 1, the maximum pressure of the hydraulic system can be calculated by the following formula (1):
Figure BDA0003284027490000091
in the formula (1), VpminFor minimum displacement of hydraulic pump during driving, ieFor reduction ratio, η, between engine output and hydraulic pumpeFor engine output of retarder efficiency, ηpmThe mechanical efficiency of the hydraulic pump. It should be noted that the highest pressure of the hydraulic system is simultaneously subjected to the relief valve pressure Pmax0And (4) limiting.
At this time, P at which the hydraulic system pressure is kept highestmaxLet Q be the maximum flow rate output by the hydraulic pump at this timemaxSetting the value range of the engine speed as n according to the parameters in the table 1e＝[800:100:5000]Displacement range V of hydraulic pumpp＝[10:1:50]Preferably, the displacement of the hydraulic pump is 10ml/r, the rotating speed of the engine is from the minimum value to the maximum value, the output flow of the hydraulic pump when the output flow accords with the constraint condition formula (3) is calculated, all the rotating speeds of the engine and the displacement of the hydraulic pump are traversed, and finally, the corresponding rotating speed of the engine and the corresponding displacement of the pump when the maximum output flow of the hydraulic pump is realized are obtained through comparison.
Figure BDA0003284027490000092
In the formula, neThe maximum output torque of the engine can be obtained by looking up a rotating speed characteristic MAP chart and is marked as Temax＝f(a,ne)。
Engine torque T demanded of hydraulic pumpedIn order to realize the purpose,
Figure BDA0003284027490000101
the hydraulic pump output flow calculation equation is as follows:
Figure BDA0003284027490000102
in the formula, VpThe displacement of the hydraulic pump; n ispThe rotating speed of the hydraulic pump; etapv is the volumetric efficiency of the hydraulic pump; qp,outThe output flow of the hydraulic pump.
When calculating the output flow of the hydraulic pump, the following torque constraint conditions need to be satisfied simultaneously:
Ted≤Temax (5)
the combination formula (1) -formula (5) can calculate the maximum hydraulic system pressure P which can be realized under different accelerator opening degreesmaxAnd the displacement of the hydraulic pump at which the maximum flow output of the hydraulic pump is achieved while maintaining the system pressure, is denoted Vp0＝min(50,Vp0) And at this time the corresponding engine speed ne0。
S1.2, according to engine speed and hydraulic pump discharge capacity, obtain hydraulic motor operating speed of hydraulic motor under different operating modes, the operating mode includes: the hydraulic pump is in a state when the maximum output flow of the hydraulic pump is achieved, a state when the displacement of the hydraulic motor is minimum and a state when the rotating speed of the engine is maximum;
first, the engine speed n is calculated from the abovee0And the displacement V of the hydraulic pumpp0(at this time, the hydraulic pump is in the maximum flow output state), and the rotating speed n of the hydraulic motor at this time can be calculatedm0Comprises the following steps:
Figure BDA0003284027490000111
in the formula etamvFor the volumetric efficiency of the hydraulic motor, the value 0.9, V is adopted in the first embodimentm,maxThe maximum displacement of the hydraulic motor is 100 in the first embodiment.
Then, the hydraulic motor speed n at which the displacement of the hydraulic motor is minimum is calculatedm1，
Figure BDA0003284027490000112
Thirdly, calculating the rotating speed n of the hydraulic motor when the rotating speed of the engine is maximumm2，
Figure BDA0003284027490000113
In the formula, Vm,minFor the minimum effective displacement of the hydraulic motor, the value 10, n is taken in the first embodimente,maxThe first embodiment takes 5000 as the maximum engine speed.
S1.3, according to the opening degree a of the accelerator and the current rotating speed n of the motormWorking speed n of hydraulic motor under different working conditionsm0、nm1、nm2Calculating to obtain the current motor rotating speed nmThe current displacement of the hydraulic pump and the current displacement of the hydraulic motor are as follows:
1) when the rotating speed of the hydraulic motor is nm<nm0While the displacement of the hydraulic motor is always kept at the maximum value Vm,maxThe displacement of the hydraulic pump is increased along with the increase of the rotating speed of the hydraulic motor, the current displacement of the hydraulic pump at the stage is calculated according to the following formula,
Figure BDA0003284027490000114
2) when the rotating speed of the hydraulic motor is nm0<nm<nm1 hour, ensure the displacement of the hydraulic pump to keep Vp0The displacement of the hydraulic motor is reduced along with the increase of the rotating speed, the current displacement of the hydraulic motor at the stage is calculated by the following formula,
Figure BDA0003284027490000121
3) when the rotating speed of the hydraulic motor is nm1<nm<nm2While the hydraulic motor maintains the minimum displacement Vm，minThe displacement of the hydraulic pump is kept at Vp0And is not changed.
4) When the rotating speed of the hydraulic motor is nm>nm2At the moment, the rotating speed of the engine is maximum, the increase of the supply flow can be realized only by increasing the displacement of the hydraulic pump, the current displacement of the hydraulic pump at the stage is calculated according to the following formula,
Figure BDA0003284027490000122
according to the parameters of table 1 adopted in the first embodiment, when the accelerator opening a is equal to 1, the displacement of the hydraulic pump and the hydraulic motor can be calculated as shown in the following fig. 2
S2, obtaining a target speed ratio i according to the current discharge capacity of the hydraulic pump and the current discharge capacity of the hydraulic motord。
The throttle opening in the allowable range, the current displacement of the hydraulic pump under the rotating speed of the motor and the current displacement of the hydraulic motor can be calculated through the formulas (1) to (11), the value range of the throttle opening is more than or equal to 0 and less than or equal to 1, and the value range of the working rotating speed of the hydraulic motor is more than or equal to 0 and less than or equal to nm≤nmmax. For convenience of control, the pump motor discharge capacity calculated in the way is converted into a target speed ratio i according to the flow conservation of the pump motord(a，nm)：
Figure BDA0003284027490000123
Target speed ratio i obtained in the above equationd(a，nm) Relates to the throttle opening degree a and the working speed n of the hydraulic motormThe throttle value range is more than or equal to 0 and less than or equal to 1, and the motor rotating speed value range is more than or equal to 0 and less than or equal to nm≤nmmax。
A second section, a control section.
S3, according to the target speed ratio idAnd the actual speed ratio i collectedaAnd obtaining the target displacement of the hydraulic motor and the target displacement of the hydraulic pump.
In the first embodiment, a PID control algorithm is adopted to realize closed-loop correction of the displacement of the pump motor.
In the first embodiment, the actual speed ratio iaComprises the following steps:
Figure BDA0003284027490000131
in the above formula npFor the rotational speed of the hydraulic pump, np＝ne/ie。
Speed ratio deviation eiComprises the following steps:
ei＝id-ia (14)
in the first embodiment, the PID correction amount is:
Figure BDA0003284027490000132
the actual control correction output is:
u＝u0+u1 (16)
the control amount u is converted into a target displacement of the hydraulic pump motor,
Figure BDA0003284027490000133
Figure BDA0003284027490000141
the target displacement of the hydraulic pump and the target displacement of the hydraulic motor of the formulas (17) and (18) are between the maximum and minimum values, namely V is satisfiedpmin≤Vp’≤Vpmax，Vmmin≤Vm’≤Vmmax。
And S4, controlling the current of the electromagnet according to the relation between the displacement of the hydraulic pump motor and the current, further realizing the expected displacement of the pump motor, and realizing the optimal dynamic control of the hydraulic stepless transmission.
The control part adopts a PID closed-loop control strategy for correction, and completes the control of the transmission system in the form of control current, and the flow schematic is shown in FIG. 3.
The output torque of the hydraulic motor in the process of controlling the full-accelerator acceleration of the vehicle by adopting the control method is shown in fig. 4, so that the method can realize an ideal motor torque output curve, wherein constant torque output is performed at the early stage, and then constant power output is performed, which shows that the optimal vehicle power performance can be realized.
Example two
As shown in fig. 5, a schematic structural diagram of an optimal dynamic control system of a hydraulic continuously variable transmission according to a second embodiment of the present invention is characterized by comprising a hydraulic pump motor current displacement module, a target speed ratio module, a hydraulic pump motor target displacement module, and a current control module, which are connected in sequence;
the hydraulic pump current displacement module is used for obtaining the current displacement of the hydraulic pump and the current displacement of the hydraulic motor under the corresponding rotating speed of the hydraulic motor according to the accelerator opening of the engine and the current rotating speed of the hydraulic motor;
the target speed ratio module is used for obtaining a target speed ratio according to the current displacement of the hydraulic pump and the current displacement of the hydraulic motor;
the hydraulic pump motor target displacement module is used for obtaining the hydraulic motor target displacement of the hydraulic motor and the hydraulic pump target displacement of the hydraulic pump according to the target speed ratio and the collected actual speed ratio;
the current control module is used for controlling the current of the hydraulic motor and the current of the hydraulic pump according to the relation between the target displacement of the hydraulic motor and the target displacement of the hydraulic pump and the current, and the current of the hydraulic motor and the current of the hydraulic pump are used for controlling the power of the hydraulic stepless transmission.
The above-described embodiments are merely illustrative of the preferred embodiments of the present application, and do not limit the scope of the present application, and various modifications and improvements made to the technical solutions of the present application by those skilled in the art without departing from the spirit of the present application should fall within the protection scope defined by the claims of the present application.

Claims (9)

1. A method of controlling optimum dynamics of a hydraulic continuously variable transmission, characterized by comprising the steps of:
according to the accelerator opening of the engine and the current rotating speed of the hydraulic motor, the current displacement of the hydraulic pump and the current displacement of the hydraulic motor under the corresponding rotating speed of the hydraulic motor are obtained;
obtaining a target speed ratio according to the current displacement of the hydraulic pump and the current displacement of the hydraulic motor;
obtaining the target displacement of a hydraulic motor of the hydraulic motor and the target displacement of a hydraulic pump of the hydraulic pump according to the target speed ratio and the collected actual speed ratio;
and controlling the current of the hydraulic motor and the current of the hydraulic pump according to the relation between the target displacement of the hydraulic motor and the target displacement and the current of the hydraulic pump, and finishing the optimal dynamic control of the hydraulic continuously variable transmission.
2. The method of claim 1, wherein the method of deriving the current displacement of the hydraulic pump and the current displacement of the hydraulic motor comprises:
obtaining the maximum pressure of a hydraulic system which can be reached by the hydraulic system according to the accelerator opening and the maximum output torque of the engine, and obtaining the maximum output flow of the hydraulic pump based on the maximum pressure of the hydraulic system;
according to the engine speed and the current displacement of the hydraulic pump, the working speeds of the hydraulic motor under different working conditions are obtained, and the working conditions comprise: the hydraulic pump is in a state when the hydraulic pump is in the maximum output flow, a state when the displacement of the hydraulic motor is minimum and a state when the rotating speed of an engine is maximum;
and obtaining the current displacement of the hydraulic pump and the current displacement of the hydraulic motor at the current motor rotating speed according to the accelerator opening, the current motor rotating speed and the working rotating speed of the hydraulic motor.
3. The hydraulic continuously variable transmission optimal dynamics control method according to claim 2, characterized in that the hydraulic pump maximum output flow rate QmaxComprises the following steps:
Figure FDA0003509967860000021
wherein, VpIs the displacement of the hydraulic pump, neAs the engine speed, ieFor reduction ratio, η, between engine output and hydraulic pumppvIs the volumetric efficiency of the hydraulic pump.
4. The method for controlling the optimal dynamic property of the hydraulic stepless speed changer according to the claim 2, characterized in that the working rotating speed of the hydraulic motor under different working conditions is calculated by the following method:
the working speed n of the hydraulic motor when the hydraulic pump is in the state of the maximum output flow of the hydraulic pumpm0Is composed of
Figure FDA0003509967860000022
Wherein n ise0Is the current speed of the engine, Vp0Is the current displacement, η, of the hydraulic pumpmvFor volumetric efficiency of the hydraulic motor, Vm,maxIs the maximum displacement of the hydraulic motor;
at the state of minimum displacement of the hydraulic motorOperating speed n of hydraulic motorm1Is composed of
Figure FDA0003509967860000023
Wherein, Vm,minIs the minimum effective displacement of the hydraulic motor;
working speed n of hydraulic motor in state of maximum engine speedm2Is composed of
Figure FDA0003509967860000024
Wherein n ise,maxThe maximum engine speed.
5. The optimal dynamics control method of a hydraulic continuously variable transmission according to claim 4, characterized in that the current motor speed nmIs nm<nm0When the displacement of the hydraulic motor is at a maximum value Vm,maxThe displacement of the hydraulic pump is calculated according to the following formula,
Figure FDA0003509967860000031
current motor speed nmIs nm0<nm<nm1The displacement of the hydraulic motor is calculated by the following formula,
Figure FDA0003509967860000032
current hydraulic motor speed nmIs nm1<nm<nm2When the hydraulic motor is at a minimum displacement Vm,minThe displacement of the hydraulic pump is kept at Vp0；
Current hydraulic motor speed nmIs nm>nm2When the hydraulic pump is discharged according toThe following formula is used for calculation,
Figure FDA0003509967860000033
wherein, Vm,minIs the minimum effective displacement, n, of the hydraulic motore,maxThe maximum engine speed.
6. The optimal dynamics control method of a hydraulic continuously variable transmission according to claim 5, characterized in that the target speed ratio id(a，nm) Is composed of
Figure FDA0003509967860000034
Wherein a is the accelerator opening.
7. The hydraulic continuously variable transmission optimal dynamics control method according to claim 6, wherein the method of obtaining the hydraulic motor target displacement and the hydraulic pump target displacement includes:
performing closed-loop correction on the target speed ratio and the actual speed ratio to obtain corrected output, wherein the actual speed ratio iaComprises the following steps:
Figure FDA0003509967860000035
wherein n ispThe rotating speed of the hydraulic pump;
converting the corrected output into the hydraulic motor target displacement and the hydraulic pump target displacement.
8. The hydraulic continuously variable transmission optimal dynamics control method according to claim 7, characterized in that the hydraulic motor target displacement is
Figure FDA0003509967860000041
The target displacement of the hydraulic pump
Figure FDA0003509967860000042
9. The optimal dynamic control system of the hydraulic stepless transmission is characterized by comprising a hydraulic pump motor current displacement module, a target speed ratio module, a hydraulic pump motor target displacement module and a current control module which are sequentially connected;
the hydraulic pump current displacement module is used for obtaining the current displacement of the hydraulic pump and the current displacement of the hydraulic motor under the corresponding rotating speed of the hydraulic motor according to the accelerator opening of the engine and the current rotating speed of the hydraulic motor;
the target speed ratio module is used for obtaining a target speed ratio according to the current displacement of the hydraulic pump and the current displacement of the hydraulic motor;
the hydraulic pump motor target displacement module is used for obtaining the hydraulic motor target displacement of the hydraulic motor and the hydraulic pump target displacement of the hydraulic pump according to the target speed ratio and the collected actual speed ratio;
the current control module is used for controlling the current of the hydraulic motor and the current of the hydraulic pump according to the relation between the target displacement of the hydraulic motor and the target displacement of the hydraulic pump and the current, and the current of the hydraulic motor and the current of the hydraulic pump are used for controlling the power of the hydraulic stepless transmission.
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