TWI426408B - Four wheels steer vehicle handling performance simulation systems - Google Patents

Description

Four-wheel steering vehicle handling performance simulation system

The invention relates to a vehicle handling performance simulation system, in particular to a four-wheel steering vehicle handling performance simulation system.

In recent years, the Electric Power Steering System (EPS) is independent of the four wheels because the vehicle system has gradually increased the research field and application range in terms of integrating mechanical, electrical, electronic and vehicle performance and has been valued by car manufacturers and related companies all over the world. The Four Wheel Steer System (4WS) is gradually being developed for use in general vehicle systems. The advantage of these technologies is that they do not consume engine power and have no oil leakage.

However, there are many design difficulties when using electric assisted steering and four-wheel independent steering systems for vehicles. These difficulties, for example, include (1) today's technology mostly uses motor-assisted steering power as the analog system, and there is no independent four-wheel steering control simulation system; (2) lack of four-wheel steering control performance, can not be evaluated, if In the actual vehicle, the adjustment is more difficult, and the operation is prone to danger; (3) the slip rate of the tire itself (Slip) and the relative radius of the relative wheel rotation are not considered; (4) the function formula corresponding to the specific vehicle Estimated handling performance, not suitable for use in other different vehicles; (5) does not consider the steering system, braking system and suspension system will affect the vehicle driving dynamics.

Although the prior art also has specific commercial software, such as Carsim, it can simulate the handling performance of four-wheel independent steering vehicles. But this soft system is a closed software, and It is limited to special applications and does not flexibly modify specific handling performance according to the designer's needs.

In view of the above problems, the present invention proposes a four-wheel steering vehicle handling performance simulation system to solve the above problems.

A four-wheel steering vehicle control performance simulation system includes a vehicle plane motion control performance simulation module. The vehicle plane motion control performance simulation module simulates the lateral acceleration, the lateral speed and the yaw rate of the vehicle body according to the longitudinal force of the tire, the lateral force of the tire and the positive return torque. The longitudinal force of the tire includes a longitudinal force of the left front wheel, a longitudinal force of the right front wheel, a longitudinal force of the left rear wheel, and a longitudinal force of the right rear wheel. The tire lateral force includes the left front wheel lateral force, the right front wheel lateral force, the left rear wheel lateral force, and the right rear wheel lateral force.

The four-wheel steering vehicle handling performance simulation system proposed by the invention further comprises a tire slip simulation module. The tire slip simulation module estimates the left front wheel slip angle according to the left front wheel steering angle, the right front wheel steering angle, the left rear wheel steering angle, the right rear wheel steering angle, the vehicle longitudinal speed, the vehicle lateral speed, and the vehicle body yaw rate. , right front wheel slip angle, left rear wheel slip angle and right rear wheel slip angle.

The four-wheel steering vehicle handling performance simulation system proposed by the invention further comprises a wheel positive force simulation module. The wheel positive force simulation module simulates the left front wheel forward force, the right front wheel positive force, the left rear wheel positive force, and the right rear wheel positive force according to the lateral acceleration and the vehicle weight.

The four-wheel steering vehicle handling performance simulation system proposed by the invention further comprises a steering motor output power simulation module. Steering motor output power simulation module based on tire Moment of inertia, tire angular velocity, steering arm length, and tire steering angle to simulate steering motor output power.

In summary, the four-wheel steering vehicle handling performance simulation system proposed by the present invention effectively simulates the movement of the vehicle on the road surface, and the simulation result is almost the same as the commercial software CarSim. In addition, the handling properties of body length, body height, weight, gear ratio, etc. can be freely modified to evaluate the power or performance of the output to reduce development time.

The detailed features and advantages of the present invention are described in the following detailed description of the embodiments of the present invention. The related objects and advantages of the present invention will be readily understood by those skilled in the art.

In order to make the present invention clear to those skilled in the art, the related nouns used in the present invention are defined first. The lateral direction is defined as the direction of the link between the left front wheel and the right front wheel. Longitudinal is defined as the horizontal plane and the vertical direction of the landscape. The forward direction is defined as the direction of gravity.

Please refer to "Figure 1", which is a system block diagram of the vehicle plane motion control performance simulation module. The vehicle plane motion control performance simulation module 10 simulates the lateral acceleration a _Y , the lateral velocity V _Y and the vehicle body yaw rate Ω _z according to the tire longitudinal force F _x , the tire lateral force F _Y and the positive return torque M _Z . Wherein the longitudinal force of the tire and comprising the longitudinal force F _{x F} xFL left front wheel longitudinal force F _xRR longitudinal force _F xFR the right front wheel, left rear wheel longitudinal force _F xRL of the right rear wheel tire lateral force F _Y includes a left front wheel lateral force _F yRR transverse force _F yFL, the lateral force _F yFR the right front wheel, the lateral force _F yRL left rear and the right rear wheel.

The detailed calculation method of the vehicle plane motion control performance simulation module can be based on the following equation: The above equation can be further rewritten as:

among them, Is the differential value of the longitudinal speed of the vehicle, It is the differential value of the lateral speed of the vehicle, a _X is the longitudinal acceleration of the vehicle, a _Y is the lateral acceleration of the vehicle, L1 is the distance between the left front wheel and the right front wheel to the center of gravity of the vehicle, and the L2 is the left rear wheel and the right rear wheel. Connected to the vehicle's center of gravity distance, R _x is the total longitudinal resistance of the vehicle, and R _y is the total lateral resistance of the vehicle.

Those skilled in the art can determine the tire longitudinal force F _X , the tire lateral force F _Y and the return positive torque M _z by Magic Formula. Then, as long as the set longitudinal speed V _X of the vehicle and the longitudinal acceleration a _{X of the} vehicle, and according to the previously known L1 and L2, the lateral acceleration a _Y , the lateral speed V _Y and the vehicle body can be obtained by the above equation. The yaw rate is Ω _z .

Please refer to Figure 2A for a block diagram of the tire slip simulation module. The tire slip simulation module 20 is used to generate four tires (left front wheel, right front wheel, left rear wheel and right rear wheel) slip angles α _FL , α _FR , α _RL and α _RR . These handling properties are generated by the following equations:

Among them, please refer to "2B", which is a schematic diagram of the angle of the four-wheel steering vehicle of the tire slip simulation module. Where δ _FL , δ _FR , δ _RL and δ _RR are the left front wheel steering angle, the right front wheel steering angle, the left rear wheel steering angle and the right rear wheel steering angle, and the L1 system is the left front wheel and the right front wheel connection to the vehicle center of gravity L2 is the distance between the left rear wheel and the right rear wheel to the center of gravity of the vehicle, the T system is the distance between the left and right wheels, the T1 is the distance between the left front wheel and the left rear wheel to the center of gravity of the vehicle, and the T2 is the right front wheel and right. The rear wheel is connected to the vehicle's center of gravity distance, Ω _z is the vehicle body yaw rate, V _X is the vehicle longitudinal speed and V _Y is the vehicle lateral speed. The vehicle body yaw rate Ω _z and the vehicle lateral speed V _Y can be obtained by the vehicle plane motion control performance simulation module.

Please refer to "3A" for the wheel positive force simulation module. Positive force control wheel normal force F _ZFL system performance simulation module for generating a left front wheel 30, the normal force F normal force F _ZFR the right front wheel, left rear wheel normal force F and the rear right wheel _{ZRL zRR} .

This wheel positive force control performance simulation module can be obtained by the following equation: mgt ₁ + F _ZR T + ma _y H =0

F _ZL = mg - F _ZR

For the relevant handling performance, please refer to "3B" and "3C". H is the vehicle to the center of gravity, m weight, L front and rear wheel distance, L1 is the distance between the left front wheel and the right front wheel to the vehicle center of gravity, L2 is the distance between the left rear wheel and the right rear wheel to the vehicle's center of gravity, the T system is the distance between the left and right wheels, the T1 is the left-wheel center of gravity, and the T2 is the right-wheel center of gravity.

Thus, according to the vehicle mass m as long as the lateral acceleration a _Y, the left front wheel to obtain the normal force _F zFL, normal force _F zFR the right front wheel, left rear wheel normal force _F zRL the right rear wheel of a positive To force F _zRR .

Please refer to Figure 4A for the steering motor output power simulation module. The steering motor output power simulation module 40 is modeled according to the model of FIG. 4B. This simulation module is simulated according to the following equation: Σ T = J _w α _w

T _fric = C _w N _w

F _r = T _in ÷( a ×cos( θ + δ ))

F _r × V _r = P J _w is the tire moment of inertia, α _w is the tire angular velocity, F _Y is the lateral force, N _w is the tire rotation speed, C _w is the tire damping coefficient, and F _r is the steering The arm moment, V _r is the steering arm speed, a is the steering arm (Steer arm) length, δ is the tire steering angle, θ is the steering arm angle, and P is the power required to rotate the tire. Since the tire rotation system is all driven by the steering motor on the electric assist steering system, according to the present invention, the power required for the tire to rotate is equal to the steering motor output power.

The tire damping coefficient C _w and the tire moment of inertia J _w can be preset. In general, the tire damping coefficient C _w can be set equal to 40, and the tire moment of inertia J _w is equal to 1.8. With this constant, the motor output power can be simulated by matching the steering arm length and the steering angle of the tire.

The above-mentioned vehicle plane motion control performance simulation module, tire slip simulation module, wheel positive force simulation module and steering motor and steering rod output power simulation module can be realized by Matlab/Simulink software, or by hard Body architecture implementation.

Please refer to FIG. 5A, which is a simulation diagram of the vehicle body yaw rate of the tire slip simulation module according to the present invention. In this figure, the horizontal axis represents time in seconds and the vertical axis represents yaw rate in degrees per second. The dotted line in the figure is the tire slip simulation module proposed by the present invention, and the solid line in the figure is the result of the simulation by the CarSim software.

Please refer to FIG. 5B, which is a lateral acceleration simulation diagram of the lateral acceleration simulation map proposed according to the present invention. In this figure, the horizontal axis represents time in seconds and the vertical axis represents lateral acceleration in meters per second per second. The dotted line in the figure is the tire slip simulation module proposed by the present invention, and the solid line in the figure is the result of the simulation by the CarSim software.

Please refer to "6A", "6B", "6C" and "6D". It is a comparison chart of simulation results of the tire slip angle simulation module according to the present invention. "Picture 6A" is the left front wheel slip angle simulation diagram, "6B diagram" is the right front wheel slip angle simulation diagram, "6C diagram" is the left rear wheel slip angle simulation diagram, "6D diagram" The system is a simulation diagram of the right rear wheel slip angle. In these figures, the horizontal axis represents time in seconds and the vertical axis represents the slip angle in degrees. The dotted line in the figure is the tire slip simulation module proposed by the present invention, and the solid line in the figure is the result of simulation by Carsim software.

Please refer to "7A", "7B", "7C" and "7D" as a comparison of simulation results of the wheel positive force simulation module according to the present invention. "7A" is the left front wheel forward force simulation map, "7B" is the right front wheel forward force simulation map, and "7C map" is the left rear wheel forward force simulation map, "7D map" The system is a simulation diagram of the right rear wheel forward force. In these figures, the horizontal axis represents time in seconds and the vertical axis represents positive force in Newtons. The dotted line in the figure is the longitudinal force simulation module of the vehicle proposed by the present invention, and the solid line in the figure is the result of simulation by Carsim software.

It can be seen from the simulation results that the tire slip simulation module proposed by the present invention is quite close to the simulation result of the Carsim commercial software, and the error is within a tolerable range.

In summary, the four-wheel steering vehicle control performance simulation system proposed by the present invention simulates the movement of the vehicle on the road surface, and the simulation result is almost the same as the commercial software CarSim. In addition, the handling characteristics of body length, body height, vehicle weight, gear ratio, etc. can be freely modified to evaluate the power or performance of the output to shorten R&D trial and error time.

Although the present invention has been disclosed above in the foregoing embodiments, it is not intended to limit the invention. It is within the scope of the invention to be modified and modified without departing from the spirit and scope of the invention. Please refer to the attached patent application for the scope of protection defined by the present invention.

10‧‧‧ Vehicle Plane Motion Control Performance Simulation Module

20‧‧‧ Tire slip simulation module

30‧‧‧ Wheel positive force control performance simulation module

40‧‧‧Steering motor output power simulation module

1 is a system block diagram of a vehicle plane motion control performance simulation module according to the present invention; "2A" is a block diagram of a tire slip simulation module according to the present invention; "2B" The figure is a perspective view of a four-wheel steering vehicle according to the tire slip simulation module of the present invention; "3A" is a wheel positive force simulation module according to the present invention; "3B" and "3C" Is a schematic diagram of the forward force of the wheel according to the present invention; "FIG. 4A" is a steering motor output power simulation module according to the present invention; "FIG. 4B" is a schematic diagram of the steering motor output simulation according to the present invention; 5A is a simulation diagram of the vehicle body yaw rate according to the tire slip simulation module proposed by the present invention; FIG. 5B is a lateral acceleration simulation diagram of the directional acceleration simulation diagram according to the present invention. "Fig. 6A" is a simulation diagram of the left front wheel slip angle according to the present invention; "Fig. 6B" is a simulation diagram of the right front wheel slip angle according to the present invention; "Fig. 6C" is a left rear wheel slip angle simulation diagram according to the present invention; "6D diagram" is according to the present invention The right rear wheel slip angle simulation diagram; "7A diagram" is a left front wheel forward force simulation diagram according to the present invention; "7B diagram" is a right front wheel forward force simulation diagram according to the present invention; "7C The diagram is a left rear wheel forward force simulation diagram according to the present invention; and the "7D diagram" is a right rear wheel forward force simulation diagram according to the present invention.

10‧‧‧ Vehicle Plane Motion Control Performance Simulation Module

Claims (6)

A four-wheel steering vehicle control performance simulation system includes: a vehicle plane motion control performance simulation module, the vehicle plane motion control performance simulation module simulates a tire according to a tire longitudinal force, a tire lateral force and a positive torque Lateral acceleration, a lateral speed and a vehicle body yaw rate, wherein the tire longitudinal force comprises a left front wheel longitudinal force, a right front wheel longitudinal force, a left rear wheel longitudinal force, a right rear wheel longitudinal force, and the tire lateral force The utility model comprises a left front wheel lateral force, a right front wheel lateral force, a left rear wheel lateral force and a right rear wheel lateral force; the steering motor output power simulation module is based on the tire moment of inertia, the tire angular velocity, the steering arm length and the tire steering Angle to simulate steering motor output power. The four-wheel steering vehicle handling performance simulation system according to claim 1, further comprising a tire slip simulation module, wherein the tire slip simulation module is based on a left front wheel steering angle, a right front wheel steering angle, and a left rear Wheel steering angle, a right rear wheel steering angle, a vehicle longitudinal speed, the lateral speed and the vehicle body yaw rate, estimating a left front wheel slip angle, a right front wheel slip angle, a left rear wheel slip angle and A right rear wheel slip angle. The four-wheel steering vehicle handling performance simulation system according to claim 2, wherein the tire slip simulation module estimates the left front wheel slip angle, the right front wheel slip angle, and the left rear wheel slip angle according to the following equation Slip angle with the right rear wheel: Wherein, α _FL for the left front wheel slip angle based, α _FR for the front right roller-based shift angle, α _RL system for the left rear wheel slip angle, α _RR for the right rear wheel slip angle based, δ _FL The left front wheel steering angle is δ _FR is the right front wheel steering angle, δ _RL is the left rear wheel steering angle, δ _RR is the right rear wheel steering angle, and L1 is the left front wheel and the right front wheel a distance connecting the center of gravity of a vehicle, L2 is a distance between the left rear wheel and the right rear wheel to the center of gravity of the vehicle, and T1 is a connection between the left front wheel and the left rear wheel to A distance of the center of gravity of the vehicle, T2 is a distance between the line connecting the right front wheel and the right rear wheel to the center of gravity of the vehicle. The four-wheel steering vehicle handling performance simulation system according to claim 1, further comprising a wheel positive force simulation module, wherein the wheel positive force simulation module is based on the lateral acceleration and a vehicle weight to simulate a left front wheel Positive force, a right front wheel positive force, a left rear wheel positive force and a right rear wheel positive force. The four-wheel steering vehicle handling performance simulation system of claim 4, wherein the wheel positive force simulation module estimates the left front wheel positive force, the right front wheel positive force, and the left rear wheel forward direction according to the following equation Force and the right rear wheel positive force: mgt ₁ + F _ZR T + ma _y H =0 F _ZL = mg - F _ZR Wherein, F _zFL is the left front wheel positive force, F _zFR is the right front wheel positive force, F _zRL is the left rear wheel positive force, F _zRR is the right rear wheel positive force, L system For the left front wheel to the left rear wheel distance, m is the vehicle weight, and a _Y is the lateral acceleration. The four-wheel steering vehicle handling performance simulation system of claim 1, wherein the steering motor output power simulation module estimates the steering motor output power according to the following equation: Σ T = J _w α _w T _fric = C _w N _w F _r = T _in ÷( a ×cos( θ + δ )) F _r × V _r = P, where P is the steering motor output power, J _w is the tire moment of inertia, α _w is the tire angular velocity, N _w is a tire rotation speed, and C _w is a tire damping The coefficient, F _r is a steering arm torque, V _r is a steering arm speed, a is a steering arm length, δ is a tire steering angle, and θ is a steering arm angle.