Research On Control Algorithm Of Semi-active Suspension With Continuously Adjustable Shock Absorber

The pros and cons of the vehicle suspension system in a great extent affect the vehicle ride comfort and handling stability,each performance between traditional passive suspension system of contradictions exist,has been unable to meet the performance requirements of modern vehicles with high dynamic performance of suspension system.Excellent semiactive suspension has solved the contradiction between ride comfort ability and handling stability of passive suspension,and it can adjust suspension force in a better way,give considerations to both sides in any road conditions.The control quality of semi-active suspension and active suspension is close,but semi-active suspension's structure is simple and its price is cheap.In this paper,the continuously adjustable shock absorber which is the core of semiactive suspension is studied.The mathematic model and the AMESim model of the continuously adjustable shock absorber were established.On the basis of this,the control strategy of semi-active suspension damping based on vehicle ride comfort is developed.The hardware-in-the-loop simulation of semi-active suspension based on the dSPACE is designed to demonstrate the performance of the Model Reference Sliding Mode Controller,the simulation and experimental results show the better performance and better robust and robust stability by adopting the proposed controllers.The main research work and conclusions are as follows:(1)The random road model was established based on MATLAB,and then the model was verified by simulation.Based on the analysis of the structure and principle of doubletube shock absorber,the structure and principle of continuously adjustable shock absorber was also analyzed.Its mathematic model of rebound stoke and compress stoke was established,and the AMESim model of continuously adjustable shock absorber was also built.Then the continuously adjustable shock absorber damper model was validated and modified according to bench test data.Finally the main structure parameters to the damping characteristic were analyzed by the co-simulation of MATLAB and AMESim,the theoretical reference is provided for the design and optimization of the continuously adjustable shock absorber.(2)Aiming at the nonlinear characteristics of semi-active suspension,a nonlinear model reference sliding mode control strategy was proposed based on the 1/4 vehicle model of semiactive suspension.A skyhook model was adopted as the reference model,and the response error between the controlled device and the skyhook reference model was used to design the sliding surface.By controlling the damping force,the response of the controlled device would follow that of the skyhook reference model as much as possible.Besides,the electromagnetic valve was analyzed to get the damping force characteristic curve of the continuously adjustable shock absorber.And then to know the electromagnetic valve variable orifice diameter at a certain speed of piston rod and expected damping force by dealing with the data,which provides effective data source for shock absorber control.Finally,the effectiveness of the model reference sliding mode controller for one fourth vehicle with two degree of freedom suspension model was analyzed through simulation.And the simulation results show that the comprehensive performance of model reference sliding mode control is better than that of passive suspension.And the model reference sliding mode control is more suitable for the damping control of the semi-active suspension.(3)According to the vibration characteristics of the whole vehicle and the principle of sliding mode control,a whole vehicle model reference sliding mode control strategy was proposed in this paper.A 7 degrees of freedom full vehicle vibration model with nonlinear semi-active suspension was established.And then a whole vehicle skyhook model was adopted as reference model.Three sliding model controllers were designed separately corresponding to the vertical,roll and pitch vibration of the whole vehicle sprung mass.Then the output of these three controllers was converted to the controlled damping force of four suspensions on the car according to the relation of four suspensions in vehicle body vibration to make the response of the controlled device to follow that of the skyhook reference model as much as possible.The comparison between the simulation results of the semi-active suspension with sliding mode control and the passive suspension show that the proposed algorithm based full vehicle model reference sliding mode controller can decline the vertical,roll and pitch vibration at the same time and improve the full vehicle ride performance effectively.(4)In order to verify the control effect of the whole vehicle model reference sliding mode control strategy proposed in this paper,the hardware in the loop simulation test project based on the dSPACE real time system was proposed.Software and hardware configuration and their working principle were elaborated.Meanwhile,the hardware circuit and program for the control system were well prepared.The hardware in the loop simulation test for semiactive suspension damping force control system which was enclosed by the CAN bus was completed by using AutoBox system and TTC200 high speed controller.The ride performance test shows that under the random road input,the whole vehicle model reference sliding mode control algorithm can obviously reduce the vibration acceleration response of the body,improve the ride comfort of the vehicle,and the overall performance of the semiactive suspension with the algorithm is better than that of passive suspension.Besides,the real time of the whole vehicle model reference sliding mode control strategy and the effectiveness of this platform were verified,too.Finally,HIL test also provided important reference for the further research of semi-active suspension control system.