Time-delay Compensation Control Of Parallel Active Suspension With Fewer Degrees Of Freedom

The vehicle suspension system is the general name of all the connection devices between the vehicle body and the wheel,which is composed of elastic element,damping element and guide mechanism.The vehicle suspension system is used to connect the car body and the wheel,and transfer the force and moment generated by the impact of the wheel from the uneven road surface to the car body,which attenuates the vibration of the car body caused by the uneven road surface and improves the ride comfort.Active suspension can replace the traditional passive suspension to improve the driving performance of vehicles,but there is often a working time delay problem that will affect the control performance of the active suspension system.Aiming at the suspension system time delay problem,this paper introduces a parallel mechanism shock absorber with fewer degrees of freedom to carry out the specific work as follows:Firstly,the structure and working principle of the parallel shock absorber with less degree of freedom are introduced.Then,the working principle of the parallel mechanism with fewer degrees of freedom was analyzed from the perspective of dynamics,and the structure and size of the motion conversion mechanism were selected according to its characteristics.The electromagnetic damping expression of the shock absorber was solved through the motion conversion relationship.The mechanism of time delay of active suspension system was analyzed,and based on the canopy damping active suspension system,a two-degree-of-freedom one-quarter suspension model with time delay was established,and three performance indexes of vehicle suspension system were expounded.The influence of time delay on closed loop system is analyzed,the critical time delay of active suspension system is calculated,the relationship among critical time delay,controllable damping and base value damping is analyzed,and the influence of time delay on the amplitude-frequency characteristics of active suspension system is analyzed.This paper analyzes the principle and application of PID controller and its limitations,selects the fuzzy PID control strategy,constructs the fuzzy PID controller according to the working principle and characteristics of the fuzzy PID control method,formulates the fuzzy rules,realizes the upper control of the active suspension with fewer degrees of freedom,and uses the current hysteresis control method to control the motor in real time.The output damping force can track the ideal damping force and be used in the suspension system.The principle of Smith predictive compensation control method is introduced,and the Smith predictive compensation controller for active suspension system with fewer degrees of freedom is designed according to this principle.Considering the influence of interference factors,an improved Smith time-delay compensation controller is designed on the basis of the traditional Smith time-delay compensation controller.The active suspension system with fewer degrees of freedom was simulated by Simulink and compared with the passive suspension system.According to the working principle of the time-delay compensation suspension system with fewer degrees of freedom,a simulation model was built to analyze the influence of different time-delays on the active suspension system with fewer degrees of freedom,and the anti-interference ability and timedelay compensation effect of the improved time-delay compensation controller were analyzed through simulation.