The research on the suspension and the braking system has achieved good results in improving the braking performance of the vehicle.
Simulations under Matlab/Simulink show that using joint control not only improves ride comfort but also improves driving safety, demonstrating the effectiveness of this control method. With the continuous development of automotive technology, the ride comfort and safety of automobiles are increasingly valued by people. Automobiles are becoming more intelligent, integrated, electronic, and lightweight. Researchers have gradually moved from a single system study to a multi-system joint control study, which is also a trend in the future of vehicle development. This article is based on this purpose, the suspension and braking system joint control, so that the system to obtain better performance.
The research on the suspension and the braking system has achieved good results in improving the braking performance of the vehicle, but at the cost of reducing the ride comfort. In this paper, the vehicle freedom model is established and two controllers are used to jointly control the two controllers. This control method is different from the single controller's control of the two systems, so that when we design a single system controller, we do not need to adopt a complex control method, the controller structure is simple, and the joint control can make the system achieve good performance. . The establishment of the system model is based on the following assumptions to establish a system model: The agricultural equipment and vehicle engineering model is shown in the figure. According to the model, each system is subjected to force analysis and a differential equation of motion is written. Suspension System Model Suspension Vertical Equation of Motion Tire Model The tire model is used in this article to specifically indicate the following braking torque model. Hydraulic braking system braking torque for agricultural equipment and vehicle engineering needs to be pointed out that under braking conditions, the vertical tire load will change , that is, generate dynamic loads. The dynamic load calculation formula is as follows: The pitch angle stiffness can be calculated by the following formula: Therefore, the vertical tire load is composed of static load and dynamic load: the meanings of the physical quantities in the above formulae are as follows: Vehicle speed, longitudinal deceleration Force; non-suspension centroid height before and after pitch angle stiffness for each wheel vertical load; front and rear track. Road surface model This article uses a filtered white noise road surface model, as follows: where: road roughness coefficient; Gauss white noise cut-off frequency with mean zero. Control method and controller design. Suspension and braking system joint control strategy Vehicle braking, due to the influence of braking inertia, the body produces front and rear pitch movement and dynamic load transfer. On the one hand, due to the transfer of dynamic loads, the vertical load on the front and rear tires changes on the ground, affecting the ground braking force. On the other hand, the vertical displacement of the suspension causes the adjustment of the suspension actuator due to the presence of the pitching motion of the vehicle body, and the degree of adjustment is related to the magnitude of the braking strength. At the same time, during the braking process of the car, the vehicle speed is continuously reduced, and the filtered white noise road surface is time-varying, which will also cause corresponding adjustment of the suspension actuator.
Based on the relationship between the above two systems, the joint control strategy for the vehicle suspension and brake system is shown in the figure. Two controllers are designed to control the car brake system and suspension system respectively. Through the parameter information of the interaction between the two systems, such as pitch angle, longitudinal deceleration, and vehicle speed, the intrinsic relationship between the two systems is analyzed, and the two controller parameters are coordinated and controlled to improve the braking performance and improve the suspension performance. That is, the control parameter adjustment of the suspension system is optimized according to the braking system control parameters and control results. Conversely, the adjustment of the control parameters of the braking system is also optimized based on the suspension system control parameters and control results. Braking system For the braking system, this article uses a logic threshold based on the slip rate control, take the optimal slip rate. During the braking process, the sensor collects some vehicle motion state parameters, solves the vehicle braking deceleration, slip rate, and calculates the maximum braking force that the ground can provide based on the tire mechanics model. When the slip rate is greater than the optimal slip rate. At that time, the return line is opened and the brake is depressurized so that the brake braking torque becomes the magnitude of the braking torque provided by the ground braking force derived from the optimal slip ratio to the wheel to brake the wheel. As the vehicle speed decreases, the longitudinal adhesion coefficient increases, so that the longitudinal braking force of the wheel becomes larger, the oil inlet pipe is opened, the brake is pressurized, and the braking torque is slowly increased, so that the vehicle can control the braking torque according to the maximum ground braking force. To brake. This kind of control method can keep the slip ratio near the optimal slip ratio and improve the braking of the system. When the vehicle parameters and weight coefficients are determined, the optimal control feedback gain matrix K can be obtained by the Riccati equation. Simulation Calculation and Analysis Simulate the above two systems and use certain vehicle parameters. The initial vehicle speed is m/s.
Simulated comparisons were made with and without control. After commissioning, when taking the weighting coefficient as follows, the figure shows the vertical acceleration of the figure, the vertical acceleration time t plus the control without control figure, the vertical displacement of the suspension comparison chart, the time t plus the control without control, the vertical displacement of the suspension, m figure, the body roll angle comparison chart... ... Time roll angle rad plus control without control diagram Body pitch angle comparison chart Pitch angle time t plus control without control & & Yang Liuqing et al.: Co-simulation of vehicle suspension and brake system Coordinated control effect between braking system and suspension system it is good. From the above simulation results, it can be seen that after the joint control, the roll angle, pitch angle, and vertical acceleration of the suspension system respectively reduce the vertical displacement of the suspension, and the vertical acceleration is significantly increased, the braking distance is significantly reduced, and the slip is reduced. The rate is always there. Nearby fluctuations, the increase in the longitudinal adhesion coefficient of the front wheels is conducive to increasing the front wheel braking force, and the longitudinal adhesion coefficient of the rear wheels is reduced, which reduces the tailing phenomenon of the vehicle during braking. The results show that both the ride comfort and driving safety are greatly improved after the two systems are jointly controlled, which proves the effectiveness of the joint control method.
Conclusion In this paper, the suspension system and the braking system are jointly controlled. The control method and the controller are simple in design and the control effect is good. We can consider how to make complex systems get good performance through simple control strategies. This article is a good attempt. In addition, from the modeling and analysis of this paper, we can see that the roll motion of the vehicle will also cause the transfer of dynamic load, change the vertical load of the left and right tires, and have an impact on the braking process. This point is worthy of further research in future studies, and it also provides the basis for joint control of steering systems and braking systems.
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