Fully active electrohydraulic control of a quarter-car test rig is considered from both a modelling and experimental point of view. This paper develops a nonlinear active hydraulic design for the active suspension system, which improves the inherent trade-off between ride quality and suspension travel. The novelty is in the use of pole assessment controller to drive a nonlinear active suspension with a new insight into the model through consideration of a new term, friction forces. Therefore, this model has taken into account the dynamic inclination angle
between linkage and actuator regardless of the fact that the designer made an only vertical motion (bounce mode) of the wheel and body units. The second contribution of this paper is that it investigated the control force generation, therefore, the nonlinear hydraulic actuator whose effective bandwidth depends on the magnitude of the suspension travel, which incorporates the dynamic equation of servovalve, is deeply researched. The nonlinear friction model is accurately established, which relies on the dynamics system analysis and the fact of slipping the body on lubricant supported bearings; this model will caption all the friction behaviours that have been observed experimentally. In addition, the hydraulic system is used to generate the system inputs as a road simulator. The controller smoothly shifts its focus between the conflicting objectives of ride comfort and rattle space utilisation, softening the suspension when suspension travel is small and stiffening it as it approaches the travel limits. Thus, the nonlinear design allows the closed-loop system to behave differently in different operating regions. The improvement achieved with our design is illustrated through comparative experiments and simulations. C++ compiler environment is used to simulate the physical system to be controlled. The results show good servo control and fast regulation of abrupt disturbances.
