CN-121973850-A - Three-fulcrum vehicle differential calculation method and differential control system

Abstract

The application relates to the technical field of vehicle differential calculation, in particular to a three-pivot vehicle differential calculation method and a differential control system, which comprise the following steps that S1, real-time parameters of a vehicle are obtained, wherein the real-time parameters comprise a rear wheel real-time steering angle, two front wheel wheelbases, front and rear wheel wheelbases, a vehicle center of gravity, a front axle distance and a real-time command vehicle speed value; S2, calculating differential offset parameters, S3, comprehensively calculating the left wheel differential speed and the right wheel differential speed, and S4, comprehensively calculating the real-time differential rotation speed value of the left wheel and the real-time differential rotation speed value of the right wheel. Based on a real vehicle calibration test, the method and the device measure the deviation between the theoretical turning radius and the actual turning radius under different steering angles, generate differential offset parameters, calculate the wheel difference rate through the differential offset parameters, and correct the theoretical wheel speed calculation value in the geometric kinematic model through the wheel difference rate, so that the left wheel rotating speed and the right wheel rotating speed can be accurately matched with the real path requirement.

Inventors

• Guo Guangchuan
• LI FEI
• YAO XIN

Assignees

• 嘉晨云控新能源(上海)有限公司

Dates

Publication Date

20260505

Application Date

20260203

Claims (10)

1. 1. A three-fulcrum vehicle differential speed calculating method is characterized by comprising the following steps: s1, acquiring real-time parameters of a vehicle through a parameter acquisition unit, wherein the parameters comprise a real-time steering angle of a rear wheel, wheelbases of two front wheels, wheelbases of the front and rear wheels, the distance between the center of gravity of the vehicle and the front axle and a real-time command vehicle speed value; s2, measuring a theoretical turning radius and an actual turning radius of the vehicle under a specific steering angle through a real-vehicle calibration test, calculating a geometric sensitivity coefficient through a proportional relation between the theoretical turning radius and the actual turning radius, and calculating a differential offset parameter through a differential offset calculation module based on a functional relation between the geometric sensitivity coefficient and the real-time steering angle of the rear wheel so as to compensate a design tolerance and an assembly error; S3, comprehensively calculating a left wheel difference rate and a right wheel difference rate by using a geometric kinematic model through a difference rate operation unit based on the real-time parameters of the vehicle obtained in the step S1 and the differential offset parameters obtained in the step S2 so as to be used for quantifying the wheel speed difference of the left wheel and the right wheel; S4, comprehensively calculating a real-time differential speed value of the left wheel and a real-time differential speed value of the right wheel through a speed control module based on the left wheel difference speed, the right wheel difference speed, the real-time command speed value and the differential speed calculation coefficient, wherein the differential speed calculation coefficient is determined by the proportional relation between the actual speed of the front wheel and the real-time command speed value of the vehicle when the vehicle runs in a straight line.
2. 2. The method for calculating the differential speed of the three-pivot vehicle according to claim 1, wherein the dynamic compensation unit is used for acquiring the tire slip rate parameter in real time, the tire slip rate parameter is calculated by the wheel speed sensor data, and the calculation result of the left wheel differential speed and the right wheel differential speed is corrected based on the parameter, so that the differential speed is dynamically adjusted; When the tire slip ratio parameter increases, the left wheel difference speed and the right wheel difference speed are reduced, so that the tail flick or steering failure of the vehicle is restrained, and the balance of the vehicle is maintained; as the tire slip parameter decreases, the left and right wheel differential rates will increase, thereby counteracting the increase in steering radius caused by the decrease in tire grip to maintain vehicle balance.
3. 3. The method for calculating the differential speed of the three-pivot vehicle according to claim 2, wherein the dynamic compensation unit is used for acquiring the road surface friction coefficient parameter in real time, the road surface friction coefficient parameter is acquired through a visual sensor or preset high-precision map data, and the calculation result of the left wheel differential speed and the right wheel differential speed is corrected based on the parameter, so that the differential speed is dynamically adjusted; when the friction coefficient parameter of the road surface is increased, the left wheel difference speed and the right wheel difference speed are reduced, so that the abrupt change of centrifugal force caused by strong adhesive force of the vehicle is counteracted, and the balance of the vehicle is maintained; when the road friction coefficient parameter decreases, the left wheel differential speed and the right wheel differential speed will increase, thereby counteracting the increase in steering radius caused by the decrease in tire grip to maintain vehicle balance.
4. 4. The three-pivot vehicle differential calculation method of claim 3, wherein the vehicle load data is obtained in real time through the dynamic compensation unit, the real-time vehicle load is obtained through measurement of the suspension pressure sensor, and the differential offset parameter is adjusted in proportion according to the deviation of the vehicle load data relative to the reference load so as to dynamically compensate and calculate the differential offset parameter in real time; When the real-time load of the vehicle is increased, the differential offset parameter is increased so as to inhibit understeer caused by the backward movement of the center of gravity of the vehicle, so that the balance of the vehicle is maintained; When the real-time load of the vehicle is reduced, the differential offset parameter is reduced to offset yaw moment unbalance caused by superposition of forward movement of the center of gravity of the vehicle and reduced adhesion of the rear wheels so as to maintain balance of the vehicle.
5. 5. The method for calculating the differential speed of the three-pivot vehicle according to claim 4, wherein the dynamic compensation unit is used for acquiring accumulated driving distance data in real time, the accumulated driving distance data is acquired through a vehicle system, and the differential speed offset parameter is adjusted according to a linear attenuation rule according to the accumulated driving distance data so as to dynamically compensate and calculate the differential speed offset parameter in real time; when the accumulated driving mileage data is increased, the differential offset parameter is reduced, so that the compensation strength is reduced to offset transmission virtual position errors caused by mechanical aging, and the balance of the vehicle is maintained; as the accumulated range data decreases, the differential offset parameter will increase, thereby counteracting the yaw moment imbalance caused by the center of gravity offset to maintain vehicle balance.
6. 6. The differential control system of the three-pivot vehicle differential computing method according to any one of claims 1 to 5, characterized by comprising: The parameter acquisition unit is used for acquiring the steering angle of the rear wheel, the wheelbase of the two front wheels, the wheelbase of the front and rear wheels, the distance between the center of gravity of the vehicle and the front axle and a real-time command vehicle speed value in real time; The differential deviation calculation module is used for measuring the theoretical turning radius and the actual turning radius of the vehicle under a specific steering angle through a real-vehicle calibration test, calculating a geometric sensitivity coefficient through the proportional relation between the theoretical turning radius and the actual turning radius, and calculating a differential deviation parameter based on the functional relation between the geometric sensitivity coefficient and the real-time steering angle of the rear wheel so as to be used for compensating design tolerance and assembly error; a difference rate calculation unit calculating a left wheel difference rate and a right wheel difference rate through a geometric kinematic model according to the vehicle real-time parameter and the differential offset parameter for quantifying a left and right wheel speed difference; The rotating speed control module comprehensively calculates a left wheel real-time differential rotating speed value and a right wheel real-time differential rotating speed value based on the left wheel differential speed, the right wheel differential speed, the real-time command vehicle speed value and the differential rotating speed calculation coefficient, is used for matching the real path requirement, and outputs a target rotating speed instruction when the left wheel real-time differential rotating speed value and the right wheel real-time differential rotating speed value are obtained; And the executing mechanism is used for driving motors of the left wheel and the right wheel to operate according to the differential ratio after receiving the rotating speed command and communicating with the vehicle controller through the CAN bus.
7. 7. The differential control system of the three-pivot vehicle differential calculation method according to claim 6, further comprising a dynamic compensation unit for acquiring a tire slip parameter in real time, the tire slip parameter being used for correcting the calculation results of the left wheel differential rate and the right wheel differential rate, thereby dynamically adjusting the differential rate; When the tire slip ratio parameter increases, the left wheel difference speed and the right wheel difference speed are reduced, so that the tail flick or steering failure of the vehicle is restrained, and the balance of the vehicle is maintained; as the tire slip parameter decreases, the left and right wheel differential rates will increase, thereby counteracting the increase in steering radius caused by the decrease in tire grip to maintain vehicle balance.
8. 8. The differential control system of the three-pivot vehicle differential calculation method according to claim 7, wherein the dynamic compensation unit is further configured to acquire a road surface friction coefficient parameter in real time, and the road surface friction coefficient parameter is used for correcting the calculation results of the left wheel differential speed and the right wheel differential speed, so as to dynamically adjust the differential speed; when the friction coefficient parameter of the road surface is increased, the left wheel difference speed and the right wheel difference speed are reduced, so that the abrupt change of centrifugal force caused by strong adhesive force of the vehicle is counteracted, and the balance of the vehicle is maintained; when the road friction coefficient parameter decreases, the left wheel differential speed and the right wheel differential speed will increase, thereby counteracting the increase in steering radius caused by the decrease in tire grip to maintain vehicle balance.
9. 9. The differential control system of the three-pivot vehicle differential calculation method according to claim 8, wherein the dynamic compensation unit is further used for acquiring vehicle load data in real time, and adjusting differential offset parameters in proportion according to the deviation of the vehicle load data relative to a reference load so as to dynamically compensate and calculate the differential offset parameters in real time; When the real-time load of the vehicle is increased, the differential offset parameter is increased so as to inhibit understeer caused by the backward movement of the center of gravity of the vehicle, so that the balance of the vehicle is maintained; When the real-time load of the vehicle is reduced, the differential offset parameter is reduced to offset yaw moment unbalance caused by superposition of forward movement of the center of gravity of the vehicle and reduced adhesion of the rear wheels so as to maintain balance of the vehicle.
10. 10. The differential control system of the three-pivot vehicle differential calculation method according to claim 9, wherein the dynamic compensation unit is further used for acquiring accumulated driving mileage data in real time, and adjusting differential offset parameters according to a linear attenuation rule according to the accumulated driving mileage data so as to dynamically compensate and calculate the differential offset parameters in real time; when the accumulated driving mileage data is increased, the differential offset parameter is reduced, so that the compensation strength is reduced to offset transmission virtual position errors caused by mechanical aging, and the balance of the vehicle is maintained; as the accumulated range data decreases, the differential offset parameter will increase, thereby counteracting the yaw moment imbalance caused by the center of gravity offset to maintain vehicle balance.

Description

Three-fulcrum vehicle differential calculation method and differential control system Technical Field The application relates to the technical field of vehicle differential speed calculation, in particular to a three-fulcrum vehicle differential speed calculation method and a differential speed control system. Background The three-fulcrum vehicle has two front wheels, which are driving wheels for driving the vehicle to travel, and one rear wheel, which is a steering wheel for controlling the steering of the vehicle. When the three-fulcrum vehicle turns, the rear wheels are used for controlling the turning, and the two front wheels respectively adopt different rotating speeds according to the turning angles of the rear wheels, so that the vehicle turns leftwards and rightwards. Based on the above principle, the turning radius of the three-fulcrum vehicle is made small, so that it is possible to travel in a narrow and crowded tunnel. When a three-fulcrum vehicle turns, the rotating speeds of left and right wheels are calculated by the system according to the steering angle, the theoretical turning radius is determined by the wheelbase of the front wheels, the wheelbase of the front wheels and the steering angle, and the actual turning radius of the vehicle is different from the theoretical turning radius due to design tolerance and assembly error of the vehicle, and the actual turning radius of the vehicle is further influenced by the change of road conditions, the change of tire wear, the change of vehicle load and the change of mechanical aging, so that the rotating speeds of the left and right wheels calculated by the system cannot be accurately matched with the actual path requirements, and the wheel speed mismatch causes the following problems: 1. the vehicle is caused to generate understeer, so that the actual turning radius is larger than the theoretical turning radius, the vehicle needs larger steering space, and the trafficability of the vehicle in a narrow passage is reduced; 2. The sliding friction between the tire and the ground is aggravated, so that the abrasion rate of the tire is improved, and the service life of the tire is influenced; 3. The abrupt change of the centrifugal force and the offset of the acting point of the centrifugal force of the vehicle are caused, so that additional moment is generated, the lateral swing of the vehicle body is induced, and the comfort and the safety of a driver are influenced. Disclosure of Invention In order to enable the rotation speeds of left and right wheels to be accurately matched with the real path requirements, the application provides a three-fulcrum vehicle differential speed calculation method and a differential speed control system. In a first aspect, the application provides a three-fulcrum vehicle differential speed calculation method, which adopts the following technical scheme that the three-fulcrum vehicle differential speed calculation method comprises the following steps: s1, acquiring real-time parameters of a vehicle through a parameter acquisition unit, wherein the parameters comprise a real-time steering angle of a rear wheel, wheelbases of two front wheels, wheelbases of the front and rear wheels, the distance between the center of gravity of the vehicle and the front axle and a real-time command vehicle speed value; s2, measuring a theoretical turning radius and an actual turning radius of the vehicle under a specific steering angle through a real-vehicle calibration test, calculating a geometric sensitivity coefficient through a proportional relation between the theoretical turning radius and the actual turning radius, and calculating a differential offset parameter through a differential offset calculation module based on a functional relation between the geometric sensitivity coefficient and the real-time steering angle of the rear wheel so as to compensate a design tolerance and an assembly error; S3, comprehensively calculating a left wheel difference rate and a right wheel difference rate by using a geometric kinematic model through a difference rate operation unit based on the real-time parameters of the vehicle obtained in the step S1 and the differential offset parameters obtained in the step S2 so as to be used for quantifying the wheel speed difference of the left wheel and the right wheel; S4, comprehensively calculating a real-time differential speed value of the left wheel and a real-time differential speed value of the right wheel through a speed control module based on the left wheel difference speed, the right wheel difference speed, the real-time command speed value and the differential speed calculation coefficient, wherein the differential speed calculation coefficient is determined by the proportional relation between the actual speed of the front wheel and the real-time command speed value of the vehicle when the vehicle runs in a straight line. Optionally, the tire slip rate parameter is obtained in real time