A method, control system and device for controlling downhill driving of a hydrostatically driven vehicle.

Abstract

This invention discloses a method, control system, and device for downhill control of a hydrostatically driven vehicle. The method includes: acquiring the vehicle's current driving data and determining whether the vehicle is in a downhill condition based on the data; when the vehicle is determined to be in a downhill condition, assessing its power limitation level based on the current gradient; and, if the power limitation level indicates that anti-stall control is required, controlling one or more of the vehicle's engine, closed-loop variable pump, and variable displacement motor to combine and limit power according to the power limitation level. By determining the vehicle's current operating condition based on relevant vehicle signals, and adaptively adjusting different levels of power limitation and limit values ​​according to the gradient and specific operating conditions, the invention prevents the vehicle from stalling, protecting both the operator and the vehicle's variable displacement motor and engine.

Description

Technical Field

[0001] This invention belongs to the fields of engineering machinery and forestry machinery. Specifically, it relates to a method, control system and device for controlling downhill driving of hydrostatic vehicles, which can realize the function of preventing stalling on downhill slopes. Background Technology

[0002] Hydrostatic drive technology is one of the core technologies of current agricultural machinery, forestry machinery, and mobile construction machinery. When a hydrostatically driven mobile device goes downhill, the speed will increase under the action of gravity and the power of the whole machine, and it will lose control and stall, which can easily cause damage to the pump and motor. If the power is then restricted, it will rely on the engine's anti-drag braking ability, which can easily cause the engine to overspeed and damage the engine.

[0003] Existing solutions typically detect vehicle speed and make judgments based on the current speed. When the vehicle speed reaches the first overspeed range, the motor displacement is maintained at the current value. When the vehicle speed reaches the second overspeed range, the engine output torque is adjusted to reduce the engine output torque to the minimum while maintaining the motor speed at the current value. When the vehicle speed reaches the third stage, in addition to maintaining the above two controls, the pump displacement is controlled according to the pump's suction and discharge pressures to prevent the reverse driving torque generated by the pump from causing the engine's negative torque to exceed a preset threshold. Furthermore, the overspeed prevention control is differentiated between driving and parking based on the accelerator pedal signal.

[0004] The above scheme mainly focuses on speed control during downhill driving. However, in actual driving conditions, the required speed control threshold varies depending on the slope. Furthermore, for downhill driving, there are no further restrictions based on the current driving conditions, making it impossible to protect against different driving conditions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method, control system and device for controlling downhill driving of hydrostatically driven vehicles. By judging the current working condition of the vehicle based on relevant vehicle signals, and adaptively adjusting the power limit and limit value at different levels according to the slope value and specific working condition of the vehicle under the corresponding working condition, the vehicle is prevented from stalling. This protects the operator on the one hand, and the variable motor and engine of the vehicle on the other hand.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for controlling downhill driving of a hydrostatically driven vehicle, comprising: Obtain the vehicle's current driving data and determine whether the vehicle is in a downhill condition based on the driving data; When a vehicle is determined to be in a downhill condition, its power limitation level is assessed based on the vehicle's current gradient. When the current vehicle is determined to require anti-stall control based on its power limitation level, the system will control one or more of the vehicle's engine, closed variable pump, and variable motor to restrict power in combination, according to the power limitation level.

[0007] The aforementioned method for controlling downhill driving of a hydrostatically driven vehicle is characterized by the following: the power limitation level is divided into four levels, namely no power limitation, level one power limitation, level two power limitation, and level three power limitation, wherein: Under Level 1 power limiting conditions, the power of one of the vehicle's engine, closed-loop variable pump, and variable motor is limited. Under Level 2 power limiting conditions, power is limited by controlling two of the vehicle's engine, closed-loop variable pump, and variable motor. Under Level 3 power limitation conditions, the engine, closed-loop variable pump, and variable motor of the vehicle are all subject to power limitation.

[0008] The aforementioned method for controlling downhill driving of a hydrostatically driven vehicle is characterized in that: the division of the power limitation level is based on the threshold range of the current slope value, and the specific steps are as follows: Based on the vehicle's driving conditions, multiple gradient values ​​are set, and anti-stall control tests are conducted at each gradient value. If, at a certain slope value, speed control can be achieved without limiting any of the devices among the engine, closed variable pump, and variable motor, and beyond that slope, limiting one of the devices among the engine, closed variable pump, and variable motor is required to achieve speed control, then that slope value is defined as the first slope threshold. If, at a certain slope value, speed control cannot be achieved by using only one of the following devices: engine, closed variable pump, or variable motor, then that slope value is defined as the second slope threshold. If, at a certain slope value, speed control cannot be achieved using only two of the following devices: engine, closed variable pump, and variable motor, then that slope value is defined as the third slope threshold. When the vehicle's current gradient value is less than the first gradient threshold, it is defined as no power restriction; when the vehicle's current gradient value is greater than the first gradient threshold but less than the second gradient threshold, it is defined as Level 1 power restriction; when the vehicle's current gradient value is greater than the second gradient threshold but less than the third gradient threshold, it is defined as Level 2 power restriction; and when the vehicle's current gradient value is greater than the third gradient threshold, it is defined as Level 3 power restriction.

[0009] The aforementioned method for controlling downhill driving of a hydrostatically driven vehicle is characterized by the following steps in determining the interpolation curves between the limit values ​​of the engine, closed-loop variable pump, and variable motor and the slope value at various slopes: Multiple gradient values ​​are set according to the vehicle's driving conditions; Randomly select one of the following devices—engine, closed variable pump, or variable motor—to conduct anti-stall tests from low to high gradient. Obtain the limit value of the equipment that can ensure the vehicle does not stall under various slopes, until the limit value of the equipment reaches its maximum limit value, and obtain the limit interpolation curve between the equipment and the slope. While the first device maintains its maximum limit value, the test slope value is increased. The second device then intervenes in the anti-stall test to obtain the limit value of the second device that can ensure the vehicle does not stall under each slope, until the limit value of the second device reaches its maximum limit value, and the limit interpolation curve between the second device and the slope is obtained. While keeping the first and second devices at their maximum limits, the test gradient is increased further, and the third device is introduced to prevent stalling. The limit value of the third device that can ensure the vehicle does not stall is obtained at each gradient until the limit value of the third device reaches its maximum limit value. The limit interpolation curve between the third device and the gradient is then obtained. This allows us to obtain the correlation between the slope at each level of power limitation and the corresponding limitation value of each device.

[0010] The aforementioned hydrostatic drive vehicle downhill control method is characterized in that: the current driving data of the vehicle also includes transmission gear information; when the transmission is detected to be in a high gear, the power limit value of one or more of the vehicle's engine, closed variable pump and variable motor is set and multiplied by a first coefficient based on the linear relationship with the slope value.

[0011] The aforementioned method for controlling downhill driving of a hydrostatically driven vehicle is characterized in that: the current driving data of the vehicle includes: seat orientation signal, gear switch signal and slope value.

[0012] The aforementioned method for controlling downhill driving of a hydrostatically driven vehicle is characterized in that: when the anti-stall control is in progress, if the detected gear switch signal is reverse gear, the power limit value of one or more of the vehicle's engine, closed variable pump, and variable motor is multiplied by a second coefficient based on the linear relationship with the slope value.

[0013] The aforementioned hydrostatic drive vehicle downhill control method is characterized in that: the current driving data of the vehicle also includes the vehicle driving pressure value, and the current driving pressure value determines whether the vehicle is in a heavy-load driving condition or a light-load driving condition. When performing anti-stall control under heavy-load driving conditions, the power limit value of one or more of the vehicle's engine, closed variable pump and variable motor is set and multiplied by a third coefficient based on the linear relationship with the slope value.

[0014] The aforementioned hydrostatic drive vehicle downhill control method is characterized in that: when performing anti-stall control on the vehicle, the engine speed signal is acquired in real time, and when the engine speed exceeds a set threshold, the closed variable pump displacement limit is prohibited from being intervened.

[0015] A hydrostatic drive vehicle downhill control system includes a hydrostatic controller, an engine controller, an engine, a closed-loop variable pump, a closed-loop variable pump electro-proportional displacement control valve, a variable motor, and a variable motor electro-proportional displacement control valve, wherein: The signal output terminal of the hydrostatic controller is connected to the signal input terminals of the engine controller, the closed variable pump electro-proportional displacement control valve, and the variable motor electro-proportional displacement control valve. The signal input terminal of the hydrostatic controller is connected to the signal output terminals of the engine controller, gearbox, slope detection sensor and FNR gear switch; The signal input terminal of the hydrostatic controller is also connected to a vehicle speed sensor and / or a motor speed sensor. The closed-loop variable pump has two electro-proportional displacement control valves, both of which are connected to the closed-loop variable pump. The variable motor electro-proportional displacement control valve is connected to the variable motor. The input end of the engine is connected to the output end of the engine controller, and the output shaft end of the engine is connected to the input shaft end of the closed-loop power pump. The two oil ports of the closed-loop variable pump and the two oil ports of the electronically controlled variable motor are connected by pipelines to form a closed loop, and the output shaft end of the electronically controlled variable motor is connected to the gearbox.

[0016] The aforementioned hydrostatic drive vehicle downhill control system is characterized in that: the signal input terminal of the hydrostatic controller is also connected to a seat orientation detection sensor.

[0017] The aforementioned hydrostatic drive vehicle downhill control system is characterized in that: the signal input terminal of the hydrostatic controller is further connected to a pressure sensor installed at the inlet and outlet of the closed variable pump or the inlet and outlet of the variable motor.

[0018] A hydrostatic drive vehicle downhill control device includes the aforementioned control system, which is used to execute the aforementioned control method.

[0019] The beneficial effects of this invention are: 1. By collecting multiple relevant driving signals during vehicle operation, the current driving conditions are identified. After detecting downhill conditions, corresponding limiting controls are applied to the closed variable pump, variable motor, and engine at different slopes to achieve anti-stall control under multiple conditions. 2. Based on the detected driving signals, the corresponding closed-loop variable pump, variable motor and engine limit values ​​are precisely controlled for dangerous or heavy-load conditions. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of a hydrostatic drive vehicle downhill control method according to the present invention. Figure 2 This is a schematic diagram of the structure of a hydrostatic drive vehicle downhill control system according to the present invention; Figure 2 In the system, the components are: 1. Engine controller; 2. Engine; 3. Closed-loop variable pump; 4. Variable displacement motor; 5. Speed ​​sensor; 6. Gearbox; 7. Motor-electric proportional displacement control valve; 8. Pressure sensor; 9. First closed-loop pump-electric proportional displacement control valve; 10. Second closed-loop pump-electric proportional displacement control valve; 11. Hydrostatic controller; 12. Seat orientation detection sensor; 13. Slope detection sensor; 14. FNR gear position switch; 15. Vehicle speed sensor. Detailed Implementation

[0021] 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.

[0022] 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

[0023] like Figure 1 As shown, a downhill control method for a hydrostatically driven vehicle includes: First: Obtain the vehicle's current driving data and determine whether the vehicle is in a downhill condition based on the driving data. In this embodiment, the current driving data to be obtained mainly includes: seat orientation signal, gear switch signal, and slope value. First, the current seat orientation is identified based on the seat orientation signal. Then, the vehicle's driving direction is determined based on the gear switch signal (hereinafter, driving towards the front of the vehicle is considered positive, and driving towards the rear of the vehicle is considered negative). Finally, the actual driving condition is determined based on the slope value (hereinafter, a positive slope value is considered uphill).

[0024] When the seat is facing forward and the vehicle is in F gear, the driver is facing the front of the vehicle and the vehicle is moving forward. At this time, if the slope detection is positive, it is a climbing condition; if the slope detection is negative, it is a downhill condition. When the seat is facing forward and the vehicle is in reverse (R) gear, the driver is facing the front of the vehicle and the vehicle is moving in the opposite direction. If the slope detection value is positive, it is a downhill condition; if the slope detection value is negative, it is an uphill condition. When the seat is facing backward and the vehicle is in F gear, the driver is facing the rear of the vehicle and the vehicle is moving in the opposite direction. If the slope detection value is positive, it is a downhill condition; if the slope detection value is negative, it is a climbing condition. When the seat is facing backward and the vehicle is in reverse (R) gear, the driver is facing the rear of the vehicle and the vehicle is moving forward. If the slope detection value is positive, it is a climbing condition; if the slope detection value is negative, it is a downhill condition.

[0025] Secondly: When a vehicle is determined to be in a downhill condition based on the corresponding driving data, its power limitation level is assessed based on the vehicle's current gradient value.

[0026] Finally: If the current vehicle requires anti-stall control based on its power limitation level, then control one or more of the vehicle's engine, closed variable pump, and variable motor to combine and limit the power according to the power limitation level.

[0027] Specifically, in this embodiment, the power limitation levels are divided into four levels: no power limitation, Level 1 power limitation, Level 2 power limitation, and Level 3 power limitation, wherein: Under Level 1 power limiting conditions, the power of one of the vehicle's engine, closed-loop variable pump, and variable motor is limited. Under Level 2 power limiting conditions, power is limited by controlling two of the vehicle's engine, closed-loop variable pump, and variable motor. Under Level 3 power limitation conditions, the engine, closed-loop variable pump, and variable motor of the vehicle are all subject to power limitation.

[0028] The classification of the dynamic limitation level is based on the threshold range of the current slope value, and the specific classification steps are as follows: Based on the vehicle's driving conditions, multiple gradient values ​​are set, and anti-stall control tests are conducted at each gradient value. If, at a certain slope value, speed control can be achieved without limiting any of the devices among the engine, closed variable pump, and variable motor, and beyond that slope, limiting one of the devices among the engine, closed variable pump, and variable motor is required to achieve speed control, then that slope value is defined as the first slope threshold. If, at a certain slope value, speed control cannot be achieved by using only one of the following devices: engine, closed variable pump, or variable motor, then that slope value is defined as the second slope threshold. If, at a certain slope value, speed control cannot be achieved using only two of the following devices: engine, closed variable pump, and variable motor, then that slope value is defined as the third slope threshold. When the vehicle's current gradient value is less than the first gradient threshold, it is defined as no power restriction; when the vehicle's current gradient value is greater than the first gradient threshold but less than the second gradient threshold, it is defined as Level 1 power restriction; when the vehicle's current gradient value is greater than the second gradient threshold but less than the third gradient threshold, it is defined as Level 2 power restriction; and when the vehicle's current gradient value is greater than the third gradient threshold, it is defined as Level 3 power restriction.

[0029] It should be noted that under various power limiting conditions, the degree of limitation of the engine, closed variable pump, and variable motor all form a limitation difference curve with respect to the slope value of the vehicle.

[0030] The specific steps for obtaining the interpolation curves between the limit values ​​of the engine, closed variable pump, and variable motor and the slope value at various slopes are as follows: Multiple gradient values ​​are set according to the vehicle's driving conditions; Randomly select one of the following devices—engine, closed variable pump, or variable motor—to conduct anti-stall tests from low to high gradient. Obtain the limit value of the equipment that can ensure the vehicle does not stall under various slopes, until the limit value of the equipment reaches its maximum limit value, and obtain the limit interpolation curve between the equipment and the slope. While the first device maintains its maximum limit value, the test slope value is increased. The second device then intervenes in the anti-stall test to obtain the limit value of the second device that can ensure the vehicle does not stall under each slope, until the limit value of the second device reaches its maximum limit value, and the limit interpolation curve between the second device and the slope is obtained. While keeping the first and second devices at their maximum limits, the test gradient is increased further, and the third device is introduced to prevent stalling. The limit value of the third device that can ensure the vehicle does not stall is obtained at each gradient until the limit value of the third device reaches its maximum limit value. The limit interpolation curve between the third device and the gradient is then obtained. This allows us to obtain the correlation between the slope at each level of power limitation and the corresponding limitation value of each device.

[0031] Taking the variable displacement motor as the limiting device for Level 1 power limitation, the variable displacement motor and closed-loop variable displacement pump as the limiting devices for Level 2 power limitation, and the variable displacement motor, closed-loop variable displacement pump, and engine as the limiting devices for Level 3 power limitation, this example illustrates how to determine the relationship between the limiting values ​​of each device and the slope value for each gradient: First, based on the vehicle's driving conditions and test conditions, the main slopes are divided into several slope test values, and then tests are conducted from low to high slopes. The critical displacement values ​​of the variable motor that ensure the vehicle does not stall are obtained at each slope until the variable motor limit value reaches its maximum, thus obtaining the slope-variable motor displacement limit interpolation curve. At this point, further increases in slope cannot limit speed by adjusting the variable motor displacement; therefore, secondary power limiting intervenes, limiting the displacement of the closed variable pump until the closed variable pump limit value reaches its maximum, thus obtaining the slope-closed variable pump displacement limit interpolation curve. Finally, the engine speed is limited, obtaining the slope-engine limit speed interpolation curve. This establishes the correlation between slope and limit values ​​at each level of power limiting, ensuring that stalling does not occur under any operating condition.

[0032] Furthermore, for the values ​​of motor displacement limit, pump displacement limit, and engine speed limit, in addition to determining them based on the slope-limit value curve, it is also necessary to determine the limit coefficient based on the driving conditions. For example, it is necessary to consider high and low gear positions for further restrictions, dangerous driving conditions for further restrictions, and heavy and light load driving conditions for further restrictions; ultimately, the limit values ​​under different slopes and different driving conditions are obtained. Specifically: the current driving data of the vehicle, including the transmission gear information, is obtained. When the transmission is detected to be in a high gear, the power limit value of one or more of the vehicle's engine, closed variable pump, and variable motor is set and multiplied by a first coefficient based on the linear relationship with the slope value.

[0033] When stall prevention control is in effect, if the detected gear switch signal is reverse (R gear), the power limit value of one or more of the vehicle's engine, closed variable pump, and variable motor is multiplied by a second coefficient based on the linear relationship with the gradient value.

[0034] Obtaining the vehicle's current driving data also includes the vehicle's driving pressure value. Based on the driving pressure value, it is determined whether the vehicle is currently in a heavy-load or light-load driving condition. When performing anti-stall control under heavy-load driving conditions, the power limit value of one or more of the vehicle's engine, closed variable pump, and variable motor is set and multiplied by a third coefficient based on the linear relationship with the gradient value.

[0035] The first and third coefficients for anti-stall control when the transmission is in high gear and under heavy load conditions are obtained through testing under extreme conditions. The specific testing process is similar to that of limiting interpolation curve testing. Secondly, when performing anti-stall control in downshifting conditions, the condition is considered dangerous, and the second coefficient is manually set mainly based on the driver's actual experience.

[0036] When implementing anti-stall control for vehicles, it is necessary to obtain the engine speed signal in real time. When the engine speed exceeds the set threshold, it is prohibited to intervene in the closed variable pump displacement limit. This is because if the closed variable pump displacement limit is suddenly triggered due to the slope at a high engine speed, the displacement of the closed variable pump will decrease. During the descent, the speed of the closed variable pump will increase, thereby driving the engine speed to increase, leading to overspeed. Therefore, it is necessary to judge the engine speed. Example 2

[0037] like Figure 2 As shown, a hydrostatic drive vehicle downhill control system includes a hydrostatic controller 11, an engine controller 1, an engine 2, a closed-loop variable pump 3, a closed-loop variable pump electro-proportional displacement control valve, a variable motor 4, and a variable motor electro-proportional displacement control valve 7, wherein: The signal output terminal of the hydrostatic controller 11 is connected to the signal input terminals of the engine controller 1, the closed variable pump electro-proportional displacement control valve, and the variable motor electro-proportional displacement control valve 7. The signal input terminal of the hydrostatic controller 11 is connected to the signal output terminals of the engine controller 1, the gearbox 6, the slope detection sensor 13, and the FNR gear switch 14. The signal input terminal of the hydrostatic controller 11 is also connected to a vehicle speed sensor 15 and / or a motor speed sensor 5. The closed-loop variable pump electro-proportional displacement control valve is of two types: a first closed-loop variable pump electro-proportional displacement control valve 9 and a second closed-loop variable pump electro-proportional displacement control valve 10. Both valves are connected to the closed-loop variable pump, enabling stepless switching of the closed-loop variable pump displacement between the forward maximum displacement and the reverse maximum displacement. The variable displacement electric proportional displacement control valve 7 is connected to the variable motor 4; the input end of the engine 2 is connected to the output end of the engine controller 1, and the output shaft end of the engine 2 is connected to the input shaft end of the closed-loop electric pump 3; the two oil ports of the closed-loop pump 3 and the two oil ports of the electric variable motor 4 are respectively connected by pipelines to form a closed loop, and the output shaft end of the electric variable motor 4 is connected to the gearbox.

[0038] The engine controller 1 is used to receive the requested speed signal to control the engine 2 and to feed back the actual speed signal. The motor speed sensor 5 is used to detect the motor speed signal, and the vehicle speed sensor 15 is used to detect the vehicle speed. In this embodiment, the vehicle speed sensor 15 and the motor speed sensor 5 are redundantly controlled. The vehicle speed can be obtained by calculating the motor speed, and the motor speed can also be calculated from the vehicle speed, thereby preventing problems from occurring when a sensor signal is lost.

[0039] The gearbox 6 is used to change the gear ratio to enable high and low speed driving of the vehicle. The gearbox also provides feedback on the current high and low gear positions, providing a basis for determining the vehicle's driving conditions. The motor electric proportional displacement control valve 7 controls the displacement of the variable motor by controlling the current. The hydrostatic controller 11 is the main controller of the system, and this controller incorporates the aforementioned downhill anti-stall control method. By receiving signals from multiple sensors, it performs logical judgment and control according to the aforementioned downhill anti-stall control method, and finally outputs the requested engine speed to the engine controller, the closed variable pump control current to the closed variable pump electric proportional displacement control valve, and the variable motor control current to the motor electric proportional displacement control valve 7.

[0040] For vehicles with switchable seat orientation, the signal input terminal of the hydrostatic controller is also connected to a seat orientation detection sensor 12 to detect the current seat orientation and determine the vehicle's driving direction in conjunction with the signal from the FNR gear switch 14. One seat orientation detection sensor 12 can be installed for automatic determination, or two can be installed to determine the orientation by detecting the seat's working angle; alternatively, a manual signal can be set for operator control, ultimately sending the signal to the controller. For vehicles with fixed seats, this sensor is not required.

[0041] The signal input terminal of the hydrostatic controller is also connected to a pressure sensor 8 installed at the inlet and outlet of the closed variable pump or the inlet and outlet of the variable motor. The pressure sensor 8 detects the real-time load pressure value of the vehicle under various working conditions. Combined with the detected signals from other vehicles, the vehicle climbing and descending conditions are divided into heavy-load climbing, heavy-load descending, light-load climbing, and light-load descending conditions to achieve more precise control. Example 3

[0042] A hydrostatic drive vehicle downhill control device includes the aforementioned control system, which is used to execute the aforementioned control method.

[0043] In summary, the hydrostatic drive vehicle downhill control method, control system, and device of the present invention determine the current working condition of the vehicle based on relevant vehicle signals, and adaptively adjust the power limit and limit value at different levels according to the slope value and specific working condition of the vehicle under the corresponding working condition, so as to prevent the vehicle from stalling. On the one hand, it protects the operator, and on the other hand, it protects the vehicle's variable displacement motor and engine.

[0044] 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 method for controlling downhill driving of a hydrostatically driven vehicle, characterized in that: include: Obtain the vehicle's current driving data and determine whether the vehicle is in a downhill condition based on the driving data; When a vehicle is determined to be in a downhill condition, its power limitation level is assessed based on the vehicle's current gradient. When the current vehicle is determined to require anti-stall control based on its power limitation level, the power of one or more of the vehicle's engine, closed variable pump, and variable motor will be controlled in combination to limit the power according to the power limitation level. The power restriction levels are divided into four levels: no power restriction, Level 1 power restriction, Level 2 power restriction, and Level 3 power restriction. Under Level 1 power limiting conditions, the power of one of the vehicle's engine, closed-loop variable pump, and variable motor is limited. Under Level 2 power limiting conditions, power is limited by controlling two of the vehicle's engine, closed-loop variable pump, and variable motor. Under Level 3 power limiting conditions, the engine, closed-loop variable pump, and variable motor of the vehicle are all subject to power limiting. The classification of the dynamic limitation level is based on the threshold range of the current slope value, and the specific steps are as follows: Based on the vehicle's driving conditions, multiple gradient values ​​are set, and anti-stall control tests are conducted at each gradient value. If, at a certain slope value, speed control can be achieved without limiting any of the devices among the engine, closed variable pump, and variable motor, and when the slope value is exceeded, speed control requires limiting one of the devices among the engine, closed variable pump, and variable motor, then the slope value is defined as the first slope threshold. If, at a certain slope value, speed control cannot be achieved by using only one of the following devices: engine, closed variable pump, or variable motor, then that slope value is defined as the second slope threshold. If, at a certain slope value, speed control cannot be achieved using only two of the following devices: engine, closed variable pump, and variable motor, then that slope value is defined as the third slope threshold. When the vehicle's current gradient value is less than the first gradient threshold, it is defined as no power restriction; when the vehicle's current gradient value is greater than the first gradient threshold but less than the second gradient threshold, it is defined as Level 1 power restriction; when the vehicle's current gradient value is greater than the second gradient threshold but less than the third gradient threshold, it is defined as Level 2 power restriction; and when the vehicle's current gradient value is greater than the third gradient threshold, it is defined as Level 3 power restriction.

2. The method for controlling downhill driving of a hydrostatically driven vehicle according to claim 1, characterized in that: The specific steps for determining the interpolation curves between the limit values ​​of the engine, closed-loop variable pump, and variable motor and the slope value at various gradients are as follows: Multiple gradient values ​​are set according to the vehicle's driving conditions; Randomly select one of the following devices—engine, closed variable pump, or variable motor—to conduct anti-stall tests from low to high gradient. Obtain the limit value of the equipment that can ensure the vehicle does not stall under various slopes, until the limit value of the equipment reaches its maximum limit value, and obtain the limit interpolation curve between the equipment and the slope. While the first device maintains its maximum limit value, the test slope value is increased. The second device then intervenes in the anti-stall test to obtain the limit value of the second device that can ensure the vehicle does not stall under each slope, until the limit value of the second device reaches its maximum limit value, and the limit interpolation curve between the second device and the slope is obtained. While keeping the first and second devices at their maximum limits, the test gradient is increased further, and the third device is introduced to prevent stalling. The limit value of the third device that can ensure the vehicle does not stall is obtained at each gradient until the limit value of the third device reaches its maximum limit value. The limit interpolation curve between the third device and the gradient is then obtained. This allows us to obtain the correlation between the slope at each level of power limitation and the corresponding limitation value of each device.

3. The method for controlling downhill driving of a hydrostatically driven vehicle according to claim 2, characterized in that: The vehicle's current driving data is obtained, including transmission gear information. When the transmission is detected to be in a high gear, the power limit value of one or more of the vehicle's engine, closed variable pump, and variable motor is set and multiplied by a first coefficient based on the linear relationship with the gradient value.

4. The method for controlling downhill driving of a hydrostatically driven vehicle according to claim 2, characterized in that: Obtaining the vehicle's current driving data also includes: seat orientation signal, gear shift signal, and slope value.

5. The downhill control method for a hydrostatically driven vehicle according to claim 4, characterized in that: When stall prevention control is in effect, if the detected gear switch signal is reverse gear, the power limit value of one or more of the vehicle's engine, closed variable pump, and variable motor is multiplied by a second coefficient based on the linear relationship with the gradient value.

6. The method for controlling downhill driving of a hydrostatically driven vehicle according to claim 2, characterized in that: Obtaining the vehicle's current driving data also includes the vehicle's driving pressure value. Based on the driving pressure value, it is determined whether the vehicle is currently in a heavy-load or light-load driving condition. When performing anti-stall control under heavy-load driving conditions, the power limit value of one or more of the vehicle's engine, closed variable pump, and variable motor is set and multiplied by a third coefficient based on the linear relationship with the gradient value.

7. The method for controlling downhill driving of a hydrostatically driven vehicle according to claim 1, characterized in that: When performing anti-stall control on the vehicle, the engine speed signal is acquired in real time. When the engine speed exceeds the set threshold, the closed variable pump displacement limit is prohibited from being activated.

8. A hydrostatic drive vehicle downhill control system, used to execute the hydrostatic drive vehicle downhill control method according to any one of claims 1-7, characterized in that: This includes a hydrostatic controller, an engine controller, an engine, a closed-loop variable pump, a closed-loop variable pump electro-proportional displacement control valve, a variable motor, and a variable motor electro-proportional displacement control valve, wherein: The signal output terminal of the hydrostatic controller is connected to the signal input terminals of the engine controller, the closed variable pump electro-proportional displacement control valve, and the variable motor electro-proportional displacement control valve. The signal input terminal of the hydrostatic controller is connected to the signal output terminals of the engine controller, gearbox, slope detection sensor and FNR gear switch; The signal input terminal of the hydrostatic controller is also connected to a vehicle speed sensor and / or a motor speed sensor. The closed-loop variable pump has two electro-proportional displacement control valves, both of which are connected to the closed-loop variable pump. The variable motor electro-proportional displacement control valve is connected to the variable motor. The input end of the engine is connected to the output end of the engine controller, and the output shaft end of the engine is connected to the input shaft end of the closed variable pump. The two oil ports of the closed-loop variable pump and the two oil ports of the variable motor are connected by pipelines to form a closed loop, and the output shaft of the variable motor is connected to the gearbox.

9. A hydrostatic drive vehicle downhill control system according to claim 8, characterized in that: The signal input terminal of the hydrostatic controller is also connected to a seat orientation detection sensor.

10. A hydrostatic drive vehicle downhill control system according to claim 8, characterized in that: The signal input terminal of the hydrostatic controller is also connected to a pressure sensor installed at the inlet and outlet of the closed variable pump or the inlet and outlet of the variable motor.

11. A hydrostatic drive vehicle downhill control device, characterized in that: The control system includes any one of claims 8-10.

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