Research On Improved And Practical H_∞ Control Strategy For Active Suspension Based On D-K Iteration

As the most important part of the vehicle, suspension system can isolate the vibration caused by road uneven and guarantee the tire contact force with the ground to some extent, which determines the ride comfort and handling stability directly. Experienced nearly hundred years of history, passive suspension has grown more and more mature. Although numerous forms have their own characteristics, each one’s improvement are based on the classic spring-damper vibration isolation system. They cannot change related design parameters real-timely, and as a result, the vibration isolation effect is limited. The rise of active suspension is a breakthrough in this aspact. The added actuators in the suspention system can make active response to the road vibration and impulse force under the command of the central controller, which suppresses the vibration of the car-body significantly.With the special fund project of Jilin province automobile industry development "Research and manufacture on inertial control technology for the car’s active suspension"(Project No. 20112330), this paper mainly analyzes and designs the improved practical H￥controlled(namelym synthesis) electro-hydraulic servo active suspension based on D-K iteration, in the aspacts of the active suspension nominal performance, robust-stability and performance.From the perspectives of vehicle riding comfort, handling stability and car-body mechanical constraints, this paper structures the state space equation and output performance equation, with the research framework of seven degrees of freedom. It takes the comfort performance of the vehicle as the optimization goal, and introduces the sensitive frequency bands based on the human body vibration comfort evaluation standards. This paper describes the problem of active suspension controller design in the approach of linear matrix inequality, and weights the input/output vectors in frequency domain, in order to design the traditional H￥ controller with full state feedback and output feedback based on the nominal model. For the controller based on the improved practical H￥ control strategy(the theory of m synthesis), the paper firstly deals with the uncertain parameters in the method of linear fractional transformation, and establishes the generalized closed-loop mathematical model with the perturbation parameters, taking the road input disturbance and noise interference of state information into consideration. And then it introduces the relevant mathematical theory about m synthesis, as the small gain theorem, the robust performance and stability theorem. Complete the design of m controller based on the state feedback and output feedback by means of D-K iteration method for the seven degrees of freedom perturbation model of active suspension, and reducts the controllers’ order with Hankel norm optimal order reduction method.The paper establishes the simulation model with Matlab/Simulink software. Taking the random road surface and pulse input as incentives, in the forms of state feedback and output feedback, it compares the passive suspension, the H￥-active suspension based on the nominal model, the improved H￥-active suspension(m-active suspension) based on perturbation model, in both time and frequency domain.In the experimental section, the paper introduces the active suspension platform from the aspacts of mechanical system, hydraulic system and electric control system, including the frame design, the installation of the actuator, the active and passive switching design, and circuit design. In the pulse road input, tests the comfortability of active and passive suspension, and detects the car body acceleration signal with vibration measuring instrument, in order to verify the effectiveness of different control strategies according to the results.