Abstract
This paper presents a constrained robust H∞ controller design of active suspension system for in-wheel-independent-drive electric vehicles considering control constraint and parameter variation. In the active suspension system model, parameter uncertainties of sprung mass are analyzed via linear fraction transformation, and the perturbation bounds can be also limited, then the uncertain quarter-vehicle active suspension model where the in-wheel motor is suspended as a dynamic vibration absorber is built. The constrained robust H∞ feedback controller of the closed-loop active suspension system is designed using the concept of reachable sets and ellipsoids, in which the dynamic tire displacements and the suspension working spaces are constrained, and a comprehensive solution is finally derived from H∞ performance and robust stability. Simulations on frequency responses and road excitations are implemented to verify and evaluate the performance of the designed controller; results show that the active suspension with a developed H∞ controller can effectively achieve better ride comfort and road-holding ability compared with passive suspension despite the existence of control constraints and parameter variations.
Highlights
Emerging in-wheel-motor-driven electric vehicles (IWMD-EV) have appeared as promising vehicle architectures in terms of several advantages, such as less fuel consumption and environmental pollution, clean energy with electrified power sources, and advanced vehicle dynamics control [1,2]
A continuous saturated controller using smooth saturation functions for an active suspension system is designed, in which nonlinear uncertainties, unknown road excitations, and bounded disturbances are considered by employing the advantages of the robust integral of the sign of the error (RISE) control technique to improve the ride comfort [30]
Note that it is feasible to obtain the best performance by applying this constrained H∞ control strategy for each motor of the quarter-car active suspension, whereas global coordination or multi-objective optimization is necessary between the controllers when the full-car suspension, seat suspension, and driver body model is used and integrated because the main control objectives for integrated suspension system are to reduce the vibration of human body and vehicle as well as ensure vehicle handling and stability
Summary
Emerging in-wheel-motor-driven electric vehicles (IWMD-EV) have appeared as promising vehicle architectures in terms of several advantages, such as less fuel consumption and environmental pollution, clean energy with electrified power sources, and advanced vehicle dynamics control [1,2]. A continuous saturated controller using smooth saturation functions for an active suspension system is designed, in which nonlinear uncertainties, unknown road excitations, and bounded disturbances are considered by employing the advantages of the robust integral of the sign of the error (RISE) control technique to improve the ride comfort [30]. This paper intends to design a constrained robust H∞ controller for active suspension system to improve ride comfort and road-holding ability of IWMD-EV. Nq (12e) where w(t) = Zg, u(t) = Fa. In order to enhance the vehicle’s ride comfort, the road-holding performance of IWMD-EV, our main control goal is to guarantee robust stability and performance for a closed-loop system of active suspension. Note that it is feasible to obtain the best performance by applying this constrained H∞ control strategy for each motor of the quarter-car active suspension, whereas global coordination or multi-objective optimization is necessary between the controllers when the full-car suspension, seat suspension, and driver body model is used and integrated because the main control objectives for integrated suspension system are to reduce the vibration of human body and vehicle as well as ensure vehicle handling and stability
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