Time-varying Mechanical Characteristic And Time Delay Compensation Control For Magnetorheological Damper Of Semi-active Suspension

Due to temperature changes,component aging,particle deposition and other reasons,the mechanical characteristics of MR damper will be real-time changes.In addition,the response speed of the driver’s output current also has an important impact on the timedelay of MR damper.To reduce the influence of the time-varying mechanical characteristic and time-delay of MR damper on the performance of MR semi-active suspension,an extended Kalman filter and equivalent replacement first-order Taylor series-LQG time-varying mechanical characteristic and time-delay compensation control strategies are proposed and verified through numerical simulation.The specific works are as follows:Firstly,the INSTRON single-channel hydraulic servo system is used to test the mechanical characteristics of MR damper.The hyperbolic tangent mechanical model which is easy to obtain the control current is selected according to the mechanical characteristics test data of MR damper and fitting model parameters.Secondly,to improve the control current of MR damper response speed,a fastresponse adjustable driver is designed according to the principle of the current control mode switching power supply.Based on this driver,the time-delay of MR damper test is performed under the test conditions with triangular wave displacement input.Thirdly,based on the 1/4 car 2-DOF MR semi-active suspension model,the nonlinear part of MR damper output force and the time-varying mechanical characteristic are linear by written into a differential equation with minimum term system characteristic,and design extended Kalman filter by using sprung mass and unsprung mass acceleration as input to observe the time-varying mechanical characteristic and system state vector of MR semi-active suspension.In order to enable the predictive control force outputted by the time-delay compensation controller to accurately track the ideal semi-active force,since the principle that the L2 norm of the time-delay active control force is equal to the corresponding predictive active control force,an equivalent replacement first-order Taylor series-LQG time-delay compensation control strategy is proposed based on the existing one.Finally,in view of the problem that the existing filtered white noise method cannot accurately model the road roughness,a method for setting the parameters of the filtered white noise model to ensure the modeling accuracy is proposed.The working performance of MR semi-active suspension based on the extended Kalman filter and equivalent replacement first-order Taylor series-LQG control is verified under the nominal working condition of D-class road with speed of 50km/h.The research results show that: With the goal of reaching 95% of the final value of the required damper force,the rise and fall time-delay of MR damper driving by the driver designed in this paper are 11 ms and 8ms respectively.Based on the extended Kalman filter and equivalent replacement first-order Taylor series-LQG control,the car body acceleration and the suspension comprehensive performance indicators of MR semiactive suspension are improved by 22.76% and 35.39% respectively compared with the passive suspension,the difference with ideal semi-active suspension are only 3.73% and2.64% respectively.