Hydrostatic double-sided drive control method, control system and skid steer loader

Abstract

The application discloses a control method and system of hydrostatic double-side driving and a skid steer loader. The control method comprises the following steps: when a vehicle is in a straight driving mode controlled by a vehicle driving handle, collecting the rotation speed of left and right motors of the vehicle in real time through a rotation speed sensor, and calculating the speed difference V between the left and right wheels in real time differ ; when the speed difference V differ between the left and right wheels is lower than a set speed difference value V differ 1, not triggering the left and right wheel speed compensation; when the speed difference V differ between the left and right wheels reaches or is higher than the set speed difference value V differ 1, triggering the current compensation of the left and right variable pumps, and then realizing the left and right wheel speed compensation. The application solves the problems of the normal straight driving deviation of the double-side driving vehicle caused by the actual parameter difference and variable characteristic difference of the left and right variable pumps and variable motors, and solves the problems of the driving deviation caused by the response difference of the motor displacement change during gear shifting and the impact of the gear shifting process of the vehicle.

Description

Technical Field

[0001] This invention relates to the field of engineering machinery technology, and more particularly to the field of hydrostatic dual-drive vehicle linear motion control technology. Background Technology

[0002] Hydrostatic dual-sided drive is widely used in traveling machinery such as skid steer loaders, bulldozers, and pavers. A hydrostatic drive system consisting of a hydraulic pump and a hydraulic motor is installed on each wheel side. The hydraulic pump is a variable displacement pump, and the hydraulic motor is typically a radial piston motor (fixed displacement or variable displacement motor). The left and right speeds of the machine are controlled by operating the travel handle to achieve various actions such as straight-line travel or steering. Because it is a dual-sided drive system, differences in the displacement and control characteristics of the hydraulic pumps and motors on both sides, as well as wear and tear on transmission components, tracks, or tires, can all cause speed differences between the two sides, leading to deviation during straight-line travel. During travel, if gear shifting occurs, the change in hydraulic motor displacement, and differences in the response and process of displacement change between the two motors, will also cause speed differences during straight-line travel. Due to the rapid gear shifting time, this can cause significant deviation. Furthermore, if gear shifting causes a travel shock, resulting in fluctuations in the travel handle control, and a slight deviation to the left or right from the straight-line position, it can easily cause the machine to lose its straight-line travel capability. When performing skid steering control, this can also easily lead to deviation problems.

[0003] To address the issue of vehicle deviation during straight-line travel in hydrostatic drive systems, some existing technical solutions involve setting and adjusting correction factors. This essentially involves modifying the displacement control parameters of a single-sided variable pump to ensure consistent actual speeds on both wheels, thus maintaining straight-line travel. However, this requires the operator to subjectively assess deviation and adjust parameter settings accordingly. The maximum adjustable deviation range is limited, such as ±1%, primarily addressing deviation caused by inconsistent tire or track speeds or wear. Other technical solutions, when one side is moving at a lower speed and the controller receives a straight-line movement command, can adjust the output flow of either the first or second variable pump until the first speed value equals the second speed value, even if the first and second speed values ​​are inconsistent.

[0004] The existing solution has the following technical defects: (1) Static setting of correction factor, subjective feeling of deviation phenomenon after the correction factor is adjusted, and then driving verification is carried out. Usually, multiple modifications and verifications are required, which is inefficient and inaccurate. It cannot solve the influence of different parameter differences in the full displacement range of pump motor (such as the difference in actual displacement corresponding to bilateral components under different currents), and cannot solve the deviation phenomenon caused by dynamic changes in the walking process, such as the inconsistent load of the left and right systems causing inconsistent efficiency of the left and right pump motors. (2) After detecting that the left and right speeds are inconsistent, only the side with the larger speed is reduced. Unilateral adjustment is prone to causing significant speed reduction. Unilateral adjustment at low speeds is prone to causing the vehicle to stop. At the same time, if the speeds are inconsistent, the adjustment is entered and needs to be completely consistent before exiting. Due to fluctuations in the speed sensor, it is easier to enter the adjustment and harder to exit. If the adjustment is continuously performed, it is easy to cause the dual-sided drive to adjust back and forth, and the vehicle actually adjusts back and forth left and right, resulting in poor straight-line handling. (3) During the shifting process, the motor displacement changes rapidly, and the performance differences between the left and right motors cause inconsistent changes, which can easily lead to deviation during straight driving. At the same time, the impact during the shifting process causes the instantaneous change in the lever control, resulting in deviation. The existing solution cannot solve the deviation problem in similar working conditions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a control method, control system and skid steer loader for a hydrostatic dual-drive vehicle, which solves the problem of deviation during normal straight-line travel caused by differences in the actual parameters and variable characteristics of the left and right variable pumps and variable motors; at the same time, it solves the problem of deviation caused by the difference in response of the motor displacement change during gear shifting and the micro-movement of the handle caused by the impact of the gear shifting process during driving.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A control method for hydrostatic dual-sided drive includes: An engine speed request signal is generated by the vehicle's accelerator pedal. This signal is parsed by the vehicle controller and sent to the engine controller, which then controls the engine to set the requested speed. The vehicle controller controls the displacement of the left and right variable pumps by controlling the current of the displacement control valves. The hydraulic oil output by the two variable pumps drives the left and right motors to rotate, thereby driving the vehicle to move. When the vehicle is in straight-line mode controlled by the drive handle, the speed sensor collects the speed of the left and right motors in real time and calculates the speed difference V between the left and right wheels in real time. differ ; When the speed difference between the left and right wheels is V differ Lower than the set speed difference value V differ At time 1, left and right wheel speed compensation is not triggered; when the speed difference between the left and right wheels of the vehicle is V... differ Reaching or exceeding the set speed difference value V differ At time 1, the left and right variable pumps are triggered to perform current compensation control simultaneously, thereby achieving left and right wheel speed compensation; During the left and right wheel speed current compensation process, the left and right wheel speed difference V differ Lower than the set speed difference value V differ 2. Or, if the vehicle is identified as not in straight-ahead mode, disengage the left and right wheel speed compensation control, where Vdiffer 2 is less than V differ 1.

[0007] The aforementioned control method for hydrostatic dual-sided drive is characterized in that: the wheel speed compensation control method is as follows: When moving in a straight line, set the current of the left and right variable pumps to A1, and the speed difference between the left and right wheels to V. differ Reaching or exceeding the set speed difference value V differ At time 1, set the speed difference V between the left and right wheels. differ The corresponding compensation current value is A2, and the compensation current value A2 is based on the speed difference value V. differ The magnitude corresponds to a linear change; When the speed difference between the left and right wheels is V differ When the value is positive, that is, the speed of the left wheel is greater than the speed of the right wheel, the current controlling the displacement control valve of the left variable pump is A1-A2, and the current controlling the displacement control valve of the right variable pump is A1+A2. When the speed difference between the left and right wheels is V differ When the current is negative, that is, the speed of the left wheel is less than the speed of the right wheel, the current controlling the displacement control valve of the left variable pump is A1+A2, and the current controlling the displacement control valve of the right variable pump is A1-A2. The rate of change of the control current of the variable pump displacement control valve increasing is defined as a1, and the rate of change of the control current of the variable pump displacement control valve decreasing is defined as b1. The magnitudes of a1 and b1 are positively correlated with the vehicle speed.

[0008] The aforementioned hydrostatic dual-sided drive control method is characterized in that: when the vehicle is in straight-line mode and a gear shifting operation is performed, i.e., when upshifting or downshifting: Set the compensation time limit t1; When the speed difference between the left and right wheels is V differ Reaching or exceeding the set speed difference value V differ At time 1, the left and right variable pumps are triggered to simultaneously perform current compensation control, and the speed difference V between the left and right wheels is set. differ The corresponding compensation current value is A3, and the compensation current value A3 is based on the speed difference value V. differ The magnitude of A3 corresponds to a linear change; for the same difference in speed between the left and right wheels, A3 is greater than A2. When the speed difference between the left and right wheels is V differ When the value is positive, that is, the speed of the left wheel is greater than the speed of the right wheel, the current controlling the displacement control valve of the left variable pump is A1-A3, and the current controlling the displacement control valve of the right variable pump is A1+A3. When the speed difference between the left and right wheels is V differ When the current is negative, that is, the speed of the left wheel is less than the speed of the right wheel, the current controlling the displacement control valve of the left variable pump is A1+A3, and the current controlling the displacement control valve of the right variable pump is A1-A3. The rate of change of the control current of the variable pump displacement control valve increasing is defined as a2, and the rate of change of the control current of the variable pump displacement control valve decreasing is defined as b2. The magnitudes of a2 and b2 are positively correlated with the vehicle speed, and at the same vehicle speed, a2 is greater than a1 and b2 is greater than b1.

[0009] The aforementioned control method for hydrostatic dual-sided drive is characterized in that: when compensated to the speed difference V between the left and right wheels... differ Lower than the set speed difference value V differ 2. Increase the waiting time t2. If the speed difference V between the left and right wheels is within the time range of t2... differ It has always been below V differ If 2, then perform compensation exit; otherwise, maintain left and right wheel speed compensation control.

[0010] The aforementioned hydrostatic dual-sided drive control method is characterized in that: within a limited time t1 after gear shift triggering, if the travel handle is in a non-straight-going mode, and the lateral coordinate value X of the travel handle is less than the longitudinal coordinate value Y, and the lateral coordinate value X is less than the set boundary value X1, then it is still considered to be in straight-going mode, and the left and right wheel speed compensation control continues; if the lateral coordinate value X of the travel handle is greater than the longitudinal coordinate value Y or the lateral coordinate value X is greater than the set boundary value X1, then the wheel speed compensation control is exited, and the corresponding slip steering action is executed.

[0011] The aforementioned control method for hydrostatic dual-sided drive is characterized in that: during wheel speed compensation control caused by gear shifting in straight-line mode, when shifting up or down at the maximum speed or near the maximum speed of the current gear, i.e., when the current A1 of the left and right variable pump displacement control valves reaches or is close to the actual current A20 corresponding to the maximum displacement of the variable pump, the current range of the corresponding variable pump displacement control valve is adjusted within a limited time t1, that is, the current application range of the variable pump displacement control valve is adjusted to A10~A30, and A30 is less than A20, wherein the current A10 is the current value corresponding to the minimum displacement of the variable pump. During wheel speed compensation at the maximum speed or near the maximum speed, the control current A1 of the variable pump displacement control valve on the lower speed side increases upward from A30 or near A30, and the control current A1 of the variable pump displacement control valve on the higher speed side decreases downward from A30 or near A30.

[0012] The aforementioned hydrostatic dual-wheel drive control method is characterized in that: the motor is an electronically controlled variable displacement motor, whose displacement can be linearly and steplessly adjusted according to the speed difference V between the left and right wheels. differ While compensating for the current of the left and right variable pump displacement control valves, the displacement of the electronically controlled variable motor can be proportionally controlled when the speed difference V between the left and right wheels... differWhen the left wheel speed is greater than the right wheel speed, based on the aforementioned left and right variable pump compensation control, the displacement of the left electronically controlled variable motor is increased, and the displacement of the right electronically controlled variable motor is decreased; when the speed difference between the left and right wheels is V... differ When the value is negative, meaning the left wheel speed is less than the right wheel speed, based on the aforementioned left and right variable pump compensation control, the displacement of the left electronically controlled variable motor is reduced, and the displacement of the right electronically controlled variable motor is increased, thereby achieving a rapid reduction in the speed difference between the two wheels.

[0013] A hydrostatic dual-drive control system includes a vehicle controller, an engine controller, an engine, a left variable pump, a left pump displacement control valve, a right variable pump, a right pump displacement control valve, a shift control valve, a left hydraulic motor, a right hydraulic motor, a left motor displacement control valve, and a right motor displacement control valve; wherein, The vehicle controller is connected to the engine controller; The output terminal of the vehicle controller is connected to the signal input terminals of the left pump displacement control valve and the right pump displacement control valve; The left variable pump input shaft is directly connected to the engine output shaft, and the right variable pump and the left variable pump form a series pump. The two oil ports of the left variable pump are directly connected to the two oil ports of the left hydraulic motor through pipelines, and the two oil ports of the right variable pump are directly connected to the two oil ports of the right hydraulic motor through pipelines. The left and right hydraulic motors drive the left and right wheels of the vehicle to move respectively. The left pump displacement control valve and the right pump displacement control valve control the displacement of the left variable pump and the right variable pump, respectively. The input terminal of the vehicle controller is also connected to the accelerator pedal signal, the travel handle signal, and the shift button signal. The output terminal of the vehicle controller is also connected to the shift control valve signal input terminal. The output terminal of the shift control valve is connected to the input terminal of the displacement control valve of the left hydraulic motor and the right hydraulic motor. The output shafts of the left hydraulic motor and the right hydraulic motor are each equipped with a speed sensor, which is connected to the input terminal of the vehicle controller.

[0014] A hydrostatic dual-drive control system includes a vehicle controller, an engine controller, an engine, a left variable pump, a left pump displacement control valve, a right variable pump, a right pump displacement control valve, a left electric variable motor, a right electric variable motor, a left motor displacement control valve, and a right motor displacement control valve; wherein, The vehicle controller is connected to the engine controller; The output terminal of the vehicle controller is connected to the signal input terminals of the engine controller, the left pump displacement control valve, the right pump displacement control valve, the left electronic variable motor displacement control valve, and the right electronic variable motor displacement control valve. The left variable pump input shaft is directly connected to the engine output shaft, and the right variable pump and the left variable pump form a series pump. The two oil ports of the left variable pump are directly connected to the two oil ports of the left electronically controlled variable motor through pipelines, and the two oil ports of the right variable pump are directly connected to the two oil ports of the right electronically controlled variable motor through pipelines. The left and right electronically controlled variable motors drive the left and right wheels of the vehicle respectively. The left pump displacement control valve and the right pump displacement control valve control the displacement of the left variable pump and the right variable pump, respectively. The input terminal of the vehicle controller is also connected to the accelerator pedal signal, the drive handle signal, and the gear shift button signal; Both the left and right electronically controlled variable motors have speed sensors installed on their output shafts, which are connected to the input of the vehicle controller.

[0015] A skid steer loader, the aforementioned control system, the control system being used to execute the aforementioned control method.

[0016] The beneficial effects of this invention are: 1. During normal straight-line deviation, bilateral compensation is performed to quickly compensate for deviation. The greater the speed difference, the greater the compensation amount, and the faster the deviation correction is performed. Independent current increase and decrease rates are set, and the deviation correction process changes smoothly. 2. To address the issue of gear shifting causing deviation in straight-line mode, a time-limited straight-line mode definition is implemented to prevent shift shock from causing handle fluctuation and deviation caused by exiting compensation; exit boundary conditions are set to maintain speed difference compensation; a new variable pump compensation current change rate is set to achieve rapid compensation and quick correction; for maximum speed shifting, the dual variable pump current range is actively adjusted to achieve dual-sided compensation for gear shift deviation at maximum speed. 3. For the electronically controlled variable motor scheme, the pump current compensation control process is enhanced by adding an adjustable controlled object to achieve rapid left and right speed difference compensation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 : A schematic diagram of a control system for a hydrostatic dual-drive vehicle according to Embodiment 2 of the present invention; Figure 2 : A schematic diagram of a control system for a hydrostatic dual-drive vehicle according to Embodiment 3 of the present invention; Figure 3 : Schematic diagram of electric control handle operation; Figure 4 : Variable pump compensation current and left and right wheel speed difference V differA diagram illustrating the linear relationship between them; In the diagram: 1. Left variable pump; 2. Left pump displacement control valve; 3. Right variable pump; 4. Right pump displacement control valve; 5. Left motor; 5a. Left motor speed sensor; 5b. Left motor displacement control valve; 5c. Left electronic variable motor displacement control valve; 6. Right motor; 6a. Right motor speed sensor; 6b. Right motor displacement control valve; 6c. Right electronic variable motor displacement control valve; 7. Shift control valve; 8. Engine; 9. Engine controller; 10. Vehicle controller; 11. Accelerator pedal; 12. Travel lever; 13. Shift button. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus. Example 1

[0020] This embodiment provides a control method for hydrostatic dual-sided drive, specifically including the following steps: An engine speed request signal is generated by the vehicle's accelerator pedal. This signal is parsed by the vehicle controller and sent to the engine controller, which then controls the engine to set the requested speed. The vehicle controller controls the displacement of the left and right variable pumps by controlling the current of the displacement control valves of the left and right variable pumps. The hydraulic oil output by the left and right variable pumps drives the left and right motors to rotate, thereby driving the vehicle to move. When the vehicle is in straight-line mode controlled by the drive handle, the speed sensor collects the speed of the left and right motors in real time and calculates the speed difference V between the left and right wheels in real time. differ ; When the speed difference between the left and right wheels is Vdiffer Lower than the set speed difference value V differ At time 1, it indicates the wheel speed difference V between the two sides. differ The difference is within an acceptable range, and the vehicle remains in a nearly straight-line state, without triggering left and right wheel speed compensation. When the left and right wheel speed difference V is within an acceptable range... differ Reaching or exceeding the set speed difference value V differ At time 1, it indicates the wheel speed difference V between the two sides. differ The difference has exceeded the acceptable range, triggering the left and right variable pumps to perform current compensation simultaneously, thereby achieving left and right wheel speed compensation; During the left and right wheel speed current compensation process, the left and right wheel speed difference V differ Lower than the set speed difference value V differ 2. Or, if the vehicle is identified as not in straight-ahead mode, disengage the left and right wheel speed compensation control, where V differ 2 is less than V differ 1. By setting the speed difference value V differ 2, as a condition for exiting compensation, increases the difficulty of exiting compensation, keeping the vehicle in a compensation control state for a longer period, while avoiding the left and right wheel speed difference V. differ There is a situation where entry and exit compensation occur repeatedly.

[0021] The method achieves rapid compensation of left and right wheel speeds through dual-wheel drive. When compensating for left and right wheel speeds, the method actually has two compensation modes: the first is the straight-line driving deviation control mode, and the second is the straight-line driving gear shift deviation control mode.

[0022] For the first straight-line driving deviation control mode, the specific compensation process is as follows: When traveling in a straight line, the current of the left and right variable displacement pump control valves is set to A1. When the speed difference between the left and right wheels is V... differ Reaching or exceeding the set speed difference value V differ At time 1, set the speed difference V between the left and right wheels. differ The corresponding compensation current value is A2, where the current compensation value A2 is related to the speed difference V between the left and right wheels. differ The linear relationship between them is as follows Figure 4 The A2 curve shown; when the speed difference V between the left and right wheels... differ When the left wheel speed is greater than the right wheel speed, adjust the current of the left variable pump displacement control valve to A1-A2, and adjust the current of the right variable pump displacement control valve to A1+A2; when the speed difference between the left and right wheels is V... differ When the current is negative, meaning the left wheel speed is less than the right wheel speed, the current of the left variable pump displacement control valve is adjusted to A1+A2, and the current of the right variable pump displacement control valve is adjusted to A1-A2. The rate of change of the variable pump displacement control valve's control current is defined as a1, and the rate of change of the variable pump displacement control valve's control current is defined as b1. The magnitudes of a1 and b1 are positively correlated with the vehicle speed.

[0023] For the second mode, which is the straight-driving shift deviation control mode, this mode refers to shifting gears when the vehicle is driving straight. The specific compensation process is: Setting a limited time t1; Left and right wheel speed difference V differ reaches or exceeds the set speed difference value V differ 1, the left and right variable pumps are triggered to perform current compensation control simultaneously, and the left and right wheel speed difference V is set differ the corresponding compensation current value is A3, when the left and right wheel speed difference V differ is positive, that is, the left wheel speed is greater than the right wheel speed, the current of the displacement control valve of the left variable pump is controlled to be A1-A3, and the current of the displacement control valve of the right variable pump is controlled to be A1+A3; when the left and right wheel speed difference V differ is negative, that is, the left wheel speed is less than the right wheel speed, the current of the displacement control valve of the left variable pump is controlled to be A1+A3, and the current of the displacement control valve of the right variable pump is controlled to be A1-A3; and the change rate of the increase in the control current of the variable pump displacement control valve is defined as a2, and the change rate of the decrease in the control current of the variable pump displacement control valve is defined as b2. a2 and b2 are positively correlated with the vehicle speed, and at the same vehicle speed, a2 is greater than a1, and b2 is greater than b1.

[0024] When compensating until the left and right wheel speed difference V differ is lower than the set speed difference value V differ 2, a waiting time t2 is added, where t2<<t1. If the left and right wheel speed difference V within the time range of t2 differ has been lower than V differ 2, the compensation is exited; otherwise, the left and right wheel speed compensation control is maintained. By setting the waiting time t2, the vehicle will not easily exit the bilateral wheel speed compensation mode. Even if the vehicle has met the exit condition at a certain time point, it is required to confirm that the exit condition is satisfied throughout the entire time period of t2 before exiting the compensation; otherwise, the vehicle continues to enter the cycle of bilateral wheel speed compensation, thereby filtering out false triggers or interference signals that instantaneously meet the exit condition during the shifting operation.

[0025] The premise of straight-line driving shifting deviation compensation is that the drive lever is kept in straight-line operation. Because the speed change after the vehicle shifts gears causes the whole vehicle to be impacted and the lever moves slightly, it is easy to cause the straight-line mode to exit. Therefore, this embodiment introduces a wide straight-line range of the lever: within the action time t1 after the gear shift is triggered, if the drive lever is in non-straight-line mode, and the lateral coordinate value X of the drive lever is less than the longitudinal coordinate value Y, and the lateral coordinate value X is less than the set boundary value X1 (the boundary value X1 can be set according to the actual situation), it is still considered to be in straight-line mode, and wheel speed bilateral compensation continues. If the lateral coordinate value X of the drive lever is greater than the longitudinal coordinate value Y or the lateral coordinate value X is greater than the set boundary value X1 (indicating that the angle of the drive lever deflection is large, which is considered to be a steering action), then the straight-line wheel speed compensation is exited, and the corresponding slip steering action is executed.

[0026] It should be noted that during wheel speed compensation caused by gear shifting in straight-line mode, when shifting up or down at or near the maximum speed of the current gear, the displacement of the variable pump has reached or is close to its maximum. Within the set time range t1, the control range of the variable pump displacement control valve is adjusted, and the current application range of the variable pump displacement control valve is adjusted accordingly to A10~A30. The value of A30 is less than the actual current value A20 corresponding to the maximum displacement of the variable pump. Here, the current A10 is the current value corresponding to the minimum displacement of the variable pump. During wheel speed compensation control at or near the maximum speed, the control current A1 of the variable pump displacement control valve on the lower speed side increases from or near A30 upwards, and the control current A1 of the variable pump displacement control valve on the higher speed side decreases from or near A30 downwards.

[0027] In both of the above modes, during wheel speed compensation, the compensation current value and the wheel speed difference V are... differ They are linearly related, and under the same wheel speed difference V differ In this case, the compensation current value in straight-shift mode is greater than the compensation current value in straight-drive mode, such as... Figure 4 As shown, curve A2 represents the current compensation value and the speed difference V between the left and right wheels in straight-line mode. differ The linear relationship between them is shown in curve A3, which represents the current compensation value and the speed difference V between the left and right wheels in straight-line shifting mode. differ The linear relationship between them. Furthermore, when wheel speed compensation is performed in both modes, the rate of change of the compensation current value is positively correlated with the vehicle speed.

[0028] It should be noted that in this embodiment, curves A2 and A3 reflect the correspondence between wheel speed difference and compensation current value under two modes. In actual operation, this relationship can be linear or set in a non-linear manner with multiple segments as required. The larger the wheel speed difference, the larger the compensation current.

[0029] In this embodiment, the selected motor is a hydraulic dual-displacement motor, which can be an electronically controlled variable displacement motor. Its displacement changes linearly and can be steplessly adjusted. Its output is reduced in speed by a reducer and then drives the wheels. Unlike the above-mentioned scheme of adjusting the displacement of the left and right variable pumps to compensate for speed difference, based on the above control scheme, during straight-line movement, in addition to monitoring the left and right speed difference and performing bilateral variable pump displacement compensation control, the displacement control of the electronically controlled variable motor is added. If the left wheel speed is greater than the right wheel speed, in addition to reducing the displacement of the left pump and increasing the displacement of the right pump, the displacement of the left electronically controlled variable motor is further reduced and the displacement of the right electronically controlled variable motor is increased to rapidly reduce the bilateral speed difference and realize the straight-line control of the whole machine. Example 2

[0030] A hydrostatic dual-drive vehicle system, such as Figure 1As shown, the system includes a vehicle controller 10, an engine controller 9, an engine 8, a left variable pump 1, a left pump displacement control valve 2, a right variable pump 3, a right pump displacement control valve 4, a left motor 5, and a right motor 6. Both the left motor 5 and the right motor 6 are dual-displacement hydraulic motors. The vehicle controller 10 is connected to the engine controller 9. The output of the vehicle controller 10 is connected to the signal input of the left pump displacement control valve 2 and the right pump displacement control valve 4. The input shaft of the left variable pump 1 is directly connected to the output shaft of the engine 8. The right variable pump 3 and the left variable pump 1 form a series pump. The two ports of the left variable pump 1 are directly connected to the two ports of the left hydraulic motor via pipelines. The two oil ports of the right variable pump 3 are directly connected to the two oil ports of the right hydraulic motor through pipelines. The left and right hydraulic motors drive the left and right wheels of the vehicle respectively. The left pump displacement control valve 2 and the right pump displacement control valve 4 control the displacement of the left variable pump 1 and the right variable pump 3 respectively, so as to realize different flow outputs of the pumps. The shift control valve 7 is connected to the left motor displacement control valve 5b of the left hydraulic motor and the right motor displacement control valve 6b of the right hydraulic motor. The output shafts of the left and right hydraulic motors are respectively equipped with left motor speed sensors 5a and right motor speed sensors 6a to detect the actual left and right wheel motor speeds. The actual left and right wheel speeds can be calculated based on the speed ratio and wheel diameter. The left and right hydraulic motors switch their displacements via the left motor displacement control valve 5b and the right motor displacement control valve 6b, respectively, with the control pressure output through the shift control valve 7. The signals from the left motor speed sensor 5a and the right motor speed sensor 6a are directly connected to the input of the vehicle controller 10. The input of the vehicle controller 10 is also connected to the signals from the accelerator pedal 11, the drive handle 12, and the shift button 13. Simultaneously, the actual engine speed is received from the engine controller 9 via CAN communication. The vehicle controller 10 and the engine controller 9 achieve engine speed control through CAN communication. The output of the vehicle controller 10 is connected to the left pump displacement control valve 2, the right pump displacement control valve 4, and the shift control valve 7. By setting different currents, the displacement of the variable pump and the output pressure of the shift valve are controlled.

[0031] For electronically controlled handles, such as Figure 3 As shown, it usually has X and Y coordinate positions, corresponding to values ​​of [0 1000] respectively. If X is 0 and Y has a value, it is a straight movement. If Y is 0 and X has a value, it is a turning movement in place. Other X and Y combinations are walking and turning movements. For example, the FR and FL positions are forward right turn or forward left turn movements. Example 3

[0032] A hydrostatic bilateral drive control system, such as Figure 2As shown, the system includes a vehicle controller 10, an engine controller 9, an engine 8, a left variable pump 1, a left pump displacement control valve 2, a right variable pump 3, a right pump displacement control valve 4, a left motor 5, and a right motor 6, wherein the left motor 5 and the right motor 6 are both electronically controlled variable motors; the vehicle controller 10 is connected to the engine controller 9; the output terminal of the vehicle controller 10 is connected to the signal input terminals of the left pump displacement control valve 2, the right pump displacement control valve 4, the left electronically controlled variable motor displacement control valve 5c, and the right electronically controlled variable motor displacement control valve 6c; the input shaft of the left variable pump 1 is directly connected to the output shaft of the engine 8, and the right variable pump 3 and the left variable pump 1 form a series pump; the left variable pump 1... The two oil ports of the left electric variable motor 5 are directly connected to the two oil ports of the right electric variable pump 3 through pipelines, and the two oil ports of the right electric variable motor 6 are directly connected to the two oil ports of the right electric variable motor 6 through pipelines. The left and right electric variable motors drive the left and right wheels of the vehicle respectively. The left pump displacement control valve 2 and the right pump displacement control valve 4 control the displacement of the left variable pump 1 and the right variable pump 3 respectively, so as to realize different flow outputs of the pumps. The input terminal of the vehicle controller 10 is also connected to the accelerator pedal 11 signal, the drive handle 12 signal and the shift button 13 signal. The output shafts of the left electric variable motor 5 and the right electric variable motor 6 are equipped with speed sensors 5a and 6a, which are connected to the input terminal of the vehicle controller 10.

[0033] Compared to Embodiment 2, this embodiment uses electronically controlled variable displacement motors for the left and right motors, and eliminates the shift control valve. The displacement control valves of the left and right electronically controlled variable displacement motors are directly controlled by the vehicle controller 10. Since the displacement of the electronically controlled variable displacement motor changes linearly, it can be steplessly adjusted. Based on monitoring the left and right speed difference, in addition to bilateral left and right pump displacement compensation control, the vehicle controller 10 adds displacement control of the electronically controlled variable displacement motor. If the left wheel speed is greater than the right wheel speed, in addition to reducing the left pump displacement and increasing the right pump displacement, the left motor displacement is further increased and the right motor displacement is decreased to rapidly reduce the bilateral speed difference and achieve straight-line control of the whole machine. Example 4

[0034] A skid steer loader includes the aforementioned control system, which is used to execute the aforementioned control method.

[0035] In summary, the hydrostatic dual-sided drive control method, control system, and skid steer loader of the present invention solve the problem of deviation during normal straight-line driving of dual-sided drive vehicles caused by differences in actual parameters and variable characteristics of left and right variable pumps and variable motors; at the same time, it solves the problem of deviation caused by differences in the response of motor displacement changes during gear shifting and the micro-movement of the handle caused by the impact of gear shifting during driving.

[0036] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A control method for hydrostatic bilateral drive, characterized in that: include: An engine speed request signal is generated by the vehicle's accelerator pedal. This signal is parsed by the vehicle controller and sent to the engine controller, which then controls the engine to set the requested speed. The vehicle controller controls the displacement of the left and right variable pumps by controlling the current of the displacement control valves of the left and right variable pumps. The hydraulic oil output by the left and right variable pumps drives the left and right motors to rotate, thereby driving the vehicle to move. When the vehicle is in straight-line mode controlled by the drive handle, the speed sensor collects the speed of the left and right motors in real time and calculates the speed difference V between the left and right wheels in real time. differ ; When the speed difference between the left and right wheels is V differ Lower than the set speed difference value V differ At time 1, left and right wheel speed compensation control is not triggered; when the speed difference between the left and right wheels of the vehicle is V... differ Reaching or exceeding the set speed difference value V differ At time 1, the left and right variable pumps are triggered to perform current compensation control simultaneously; During the left and right wheel speed current compensation process, the left and right wheel speed difference V differ Lower than the set speed difference value V differ 2. Or, if the vehicle is identified as not in straight-ahead mode, disengage the left and right wheel speed compensation control, where V differ 2 is less than V differ 1; When traveling in a straight line, the current of the left and right variable displacement pump control valves is set to A1, and the speed difference between the left and right wheels is V. differ Reaching or exceeding the set speed difference value V differ At time 1, set the speed difference V between the left and right wheels. differ The corresponding compensation current value is A2, and the compensation current value A2 is based on the speed difference value V. differ The magnitude corresponds to a linear change; When shifting gears while the vehicle is in straight-line mode, i.e., when upshifting or downshifting: Set the compensation time limit t1; When the speed difference between the left and right wheels is V differ Reaching or exceeding the set speed difference value V differ At time 1, the left and right variable pumps are triggered to simultaneously perform current compensation control, and the speed difference V between the left and right wheels is set. differ The corresponding compensation current value is A3, and the compensation current value A3 is based on the speed difference value V. differ The magnitude of A3 corresponds to a linear change; for the same difference in speed between the left and right wheels, A3 is greater than A2. When the speed difference between the left and right wheels is V differ When the value is positive, that is, the speed of the left wheel is greater than the speed of the right wheel, the current controlling the displacement control valve of the left variable pump is A1-A3, and the current controlling the displacement control valve of the right variable pump is A1+A3. When the speed difference between the left and right wheels is V differ When the current is negative, that is, the speed of the left wheel is less than the speed of the right wheel, the current controlling the displacement control valve of the left variable pump is A1+A3, and the current controlling the displacement control valve of the right variable pump is A1-A3. The rate of change of the control current of the variable pump displacement control valve increasing is defined as a2, and the rate of change of the control current of the variable pump displacement control valve decreasing is defined as b2. The magnitudes of a2 and b2 are positively correlated with the vehicle speed.

2. The control method for hydrostatic bilateral drive according to claim 1, characterized in that: The wheel speed compensation control method is as follows: When walking in a straight line When the speed difference between the left and right wheels is V differ When the value is positive, that is, the speed of the left wheel is greater than the speed of the right wheel, the current controlling the displacement control valve of the left variable pump is A1-A2, and the current controlling the displacement control valve of the right variable pump is A1+A2. When the speed difference between the left and right wheels is V differ When the current is negative, that is, the speed of the left wheel is less than the speed of the right wheel, the current controlling the displacement control valve of the left variable pump is A1+A2, and the current controlling the displacement control valve of the right variable pump is A1-A2. The rate of change of the control current of the variable pump displacement control valve is defined as a1, and the rate of change of the control current of the variable pump displacement control valve is defined as b1. The magnitudes of a1 and b1 are positively correlated with the vehicle speed, and at the same vehicle speed, a2 is greater than a1 and b2 is greater than b1.

3. The control method for hydrostatic bilateral drive according to claim 1, characterized in that: Within a limited time t1 after a gear shifting operation is performed when the vehicle is in a straight driving mode, during the left and right wheel speed compensation control, when the left and right wheel speed difference V differ is lower than a set wheel speed difference V differ 2, a waiting time t2 is added, t2<<t1, if the left and right wheel speed difference V differ is always lower than V differ 2 within the time t2, the compensation is exited; otherwise, the left and right wheel speed compensation control is maintained.

4. The control method for hydrostatic bilateral drive according to claim 1, characterized in that: Within a limited time t1 after the gear shift is triggered, if the travel handle is in non-straight-going mode, and the lateral coordinate value X of the travel handle is less than the longitudinal coordinate value Y, and the lateral coordinate value X is less than the set boundary value X1, then it is still considered to be in straight-going mode, and the left and right wheel speed compensation control continues. If the lateral coordinate value X of the travel handle is greater than the longitudinal coordinate value Y or the lateral coordinate value X is greater than the set boundary value X1, then the wheel speed compensation control is exited, and the corresponding slip steering action is executed.

5. The control method for hydrostatic bilateral drive according to claim 1, characterized in that: When wheel speed compensation control is applied during gear shifting in straight-line mode, when shifting up or down at or near the maximum speed of the current gear, i.e. when the current A1 of the left and right variable pump displacement control valves reaches or approaches the actual current A20 corresponding to the maximum displacement of the variable pump, the control range of the variable pump displacement control valve is adjusted within a limited time t1. That is, the application range of the variable pump displacement control valve current is adjusted to A10~A30, and A30 is less than A20. A10 is the current value corresponding to the minimum displacement of the variable pump. During wheel speed compensation control at or near the maximum speed, the control current A1 of the variable pump displacement control valve on the lower speed side increases from or near A30, and the control current A1 of the variable pump displacement control valve on the higher speed side decreases from or near A30.

6. The control method for hydrostatic bilateral drive according to claim 1, characterized in that: The motor is an electronically controlled variable displacement motor, whose displacement can be linearly and steplessly adjusted according to the speed difference V between the left and right wheels. differ While compensating for the current of the left and right variable pump displacement control valves, the displacement of the electronically controlled variable motor can be proportionally controlled when the speed difference V between the left and right wheels... differ When the left wheel speed is greater than the right wheel speed, based on the above-mentioned left and right variable pump compensation control, the displacement of the left electronically controlled variable motor is increased, and the displacement of the right electronically controlled variable motor is decreased; when the speed difference between the left and right wheels is V... differ When the value is negative, meaning the left wheel speed is less than the right wheel speed, based on the above-mentioned left and right variable pump compensation control, the displacement of the left electronically controlled variable motor is reduced, and the displacement of the right electronically controlled variable motor is increased, thereby achieving a rapid reduction in the speed difference between the two wheels.

7. A hydrostatic bilateral drive control system for implementing the control method according to any one of claims 1-6, characterized in that: It includes a vehicle controller, an engine controller, an engine, a left variable pump, a left pump displacement control valve, a right variable pump, a right pump displacement control valve, a shift control valve, a left hydraulic motor and a right hydraulic motor, a left motor displacement control valve, and a right motor displacement control valve; wherein, the vehicle controller is connected to the engine controller; The output terminal of the vehicle controller is connected to the signal input terminals of the left pump displacement control valve, the right pump displacement control valve, and the shift control valve. The left variable pump input shaft is directly connected to the engine output shaft, and the right variable pump and the left variable pump form a series pump; The two oil ports of the left variable pump are directly connected to the two oil ports of the left hydraulic motor through pipelines, and the two oil ports of the right variable pump are directly connected to the two oil ports of the right hydraulic motor through pipelines. The left and right hydraulic motors drive the left and right wheels of the vehicle to move respectively. The input terminal of the vehicle controller is also connected to the accelerator pedal signal, the travel handle signal, and the shift button signal. The output terminal of the shift control valve is connected to the input terminal of the left and right motor displacement control valves. The output shafts of the left and right hydraulic motors are each equipped with a speed sensor, which is connected to the input terminal of the vehicle controller.

8. A hydrostatic bilateral drive control system for implementing the control method according to any one of claims 1-6, characterized in that: This includes the vehicle controller, engine controller, engine, left variable pump, left pump displacement control valve, right variable pump, right pump displacement control valve, left and right electronically controlled variable motors, left motor displacement control valve, and right motor displacement control valve; among which, The vehicle controller is connected to the engine controller; The output terminal of the vehicle controller is connected to the signal input terminals of the engine controller, the left pump displacement control valve, the right pump displacement control valve, the left electronic variable motor displacement control valve, and the right electronic variable motor displacement control valve. The left variable pump input shaft is directly connected to the engine output shaft, and the right variable pump and the left variable pump form a series pump; The two oil ports of the left variable pump are directly connected to the two oil ports of the left electronically controlled variable motor through pipelines, and the two oil ports of the right variable pump are directly connected to the two oil ports of the right electronically controlled variable motor through pipelines. The left and right electronically controlled variable motors drive the left and right wheels of the vehicle respectively. The input terminal of the vehicle controller is also connected to the accelerator pedal signal, the drive handle signal, and the gear shift button signal; Both the left and right electronically controlled variable motors have speed sensors installed on their output shafts, which are connected to the input of the vehicle controller.

9. A skid steer loader, characterized in that: The system includes the control system described in claim 7 or 8, which is used to perform the control method described in any one of claims 1-6.

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