| The suspension is one of the important assembly of a vehicle,and its performance has a direct impact on ride comfort and handling stability.Special vehicles have higher performance requirement on suspension systems,especially emergency rescue vehicles need to operate while moving sometimes,which have special requirement on stability of the vehicle attitude.It is hard to achieve the target for conventional suspension system.Active suspension system could control the vehicle attitude in real-time,so that the vehicle body becomes an inertial stabilization platform to satisfy the situation on the vehicle attitude stabilization control requirements.This dissertation is funded by National Key Technologies R&D Program “Key Technology Research on Special Chassis and Suspension for High-mobility Emergency Rescue Vehicle(Including Fire Fighting Vehicle)”(Project Number: 2016YFC0802902)and the Special funds of Automobile Industry in Jilin Province for the project “Research and Development of Inertial Control Technology for Car Active Suspension”(Project Number: 20112330).The methods to keep stability of the vehicle attitude for special vehicles are conducted research in depth,a servo controller for active suspension actuator and a set of active disturbance rejection controllers(ADRC)for the vehicle attitude stability control are designed,the main work is as follows:(1)The dynamic model of valve controlled asymmetric hydraulic cylinder and the nonlinear model of 1/4 active suspension are built.The dynamic model of valve controlled asymmetric hydraulic cylinder is built on different working conditions.The nonlinear model of 1/4 active suspension is built with nonlinear parts of spring and shock absorber.Then,the relative accurate model parameters are obtained by the method of parameter identification with multiple experimental data.(2)A servo controller for active suspension actuator is designed.According to definition of fractional order calculus and theory of fractional order system,an Oustaloup recursive approximation(ORA)fractional order PID(FOPID)controller is designed as the servo controller for active suspension actuator.Then,the parallel adaptive clonal selection algorithm(PACSA)is proposed to tuning the FOPID parameters.(3)A set of ADRC for the vehicle attitude stability control is designed.The problem of multi-input multi-output(MIMO)coupling of vehicle attitude stability control system is solved by setting virtual control variables,according to the features of ADRC.And the displacement-velocity(or angle-angular velocity)dual-loop ADRC is designed for decoupled vertical,pitching and rolling control channels.Then the decoupling effects of this control method and the vehicle attitude stability control performance are verified by simulation research.(4)The problem of displacement output saturation of active suspension actuator is studied.In order to solve the problem of actuator displacement output saturation caused by the impact of road surface,the control strategy of virtual limit block is designed on the basis of analyzing the traditional processing method of the problem.In order to solve the problem of actuator displacement output saturation caused by rise and fall of the slope road,a method is proposed to estimate slope envelope,the improvements of the vertical stability controller and pitch stabilization controller are designed respectively based on the method.The effectiveness of the proposed method is verified by simulation analysis for two conditions of actuator displacement output saturation.(5)The prototype of active suspension vehicle is built based on the suspension of FAW “Besturn” car,the road experiments are carried out to verify the vehicle attitude control.With the experimental conditions of pulse input road and uneven terrain,the performance of vehicle attitude control using displacement-velocity(or angle-angular velocity)dual-loop decoupling ADRC which proposed in this dissertation is verified and compared with the passive suspension set of the same vehicle. |
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