Nonlinear active suspension control design applied to a half-car model

This paper develops a novel nonlinear backstepping design for the control of half-car active suspension systems to improve the inherent tradeoff between ride quality and suspension travel. Since ride quality depends on a combination of vertical displacement and angular displacement of the vehicle body, an active suspension controller must be able to minimize heave and pitch movements in order to guarantee ride comfort of passengers. To avoid damaging vehicle components and generating more passenger discomfort, the controller must be capable of preventing the suspension from hitting it travel limits. Our design, with two additional nonlinear filters, shows potentials to achieve these conflicting control objectives. The novelty is in the use of two nonlinear filters at both front and rear wheels. The effective bandwidths of these two nonlinear filters depend on the magnitudes of the front and rear suspension travels individually. As a result, the improvement of tradeoff between ride quality and suspension travel is guaranteed and then demonstrated through comparative simulations.