Study On Multi-objective Output Feedback Control Of Semi-Active Suspension Based On LMI

Vehicle suspensions have been an active research area due to its important role in vehicle performances in recent years. Performance requirements for advanced vehicle suspensions include: 1) isolating passengers from vibration and shock arising from road roughness; 2) suppressing the hop of the wheels so as to maintain firm and uninterrupted contact of wheels to road; and 3) keeping suspension strokes within an allowable maximum. Generally speaking, the ride comfort and handling stability of vehicle are conflicting objectives. The ride comfort requires that the car body achieves lowest acceleration levels. On the other hands, the handling performance implies that the wheel normal forces are kept as constant as possible. Physically, this means that wheels should follow the road profiles well, so as to achieve as constant tire deflection as possible. This paper tries to design a kind of algorithm for semi-active suspension which should be simple to realize and can achieve a balanced ride and handling performance however the parameters and the disturbance change, that is to say , the new suspension must be robust. The main purpose of this study is to provide good control method for semi-active suspension control system.In this thesis, multi-objective output feedback controller based on linear matrix inequality (LMI) is designed for quarter car model and the effciency of the proposed approach is validated. In this strategy, select H2 system norm of the transfer function from road profile vertical velocity disturbance to output evaluating signal as the evaluating index of ride comfort performance, select H∞system norm of the transfer function from road profile vertical velocity disturbance to output evaluating signal as the evaluating index of handling stability performance, and the control method optimizes the mixed H2 / H∞performance. Then, multi-objective output feedback centralized and distributed controllers of active suspension are designed for vertical vehicle dynamic model with seven degrees of freedom. The simulation results show that the distributed approach can obtain better efficiency, is simple to realize, and consume less energy in comparison with centralized approach. Consider semi-active constrained condition, the distributed control approach of the full-car semi-active suspension is studied and simulated. The simulation results show that the distributed multi-objective output feedback controller of semi-active suspension can effectively suppress the vibration of vehicle, the RMS of body heave, roll, pitch accelerations, dynamic tire loads and suspension deflections are reduced significantly, and the proposed contoller has a good robustness to the parameters and the disturb change. The study of the proposed approach supply valuable theoretic references to further research of vehicle semi-active suspension control.