Interlaced Backstepping and Integrator Forwarding for Nonlinear Control of an Electrohydraulic Active Suspension

Passengers' comfort in long road trips is of crucial importance; as a result, active suspension control became a vital subject in recent researches. This paper studies the control of an electrohydraulic active suspension, based on a combination of backstepping and integrator forwarding. Our goal is to control and reduce the car's vertical motion and keep it to zero. The active suspension model is highly nonlinear and non-differentiable due to the hydraulic components, especially the servovalve and the hydraulic actuator whose chambers' volume varies during extension and retraction. Therefore, a powerful control strategy is required. In such cases, Lyapunov-based control strategies are the most suitable for offering a lot of maneuverability in building an analytical control signal. The mathematical model of an electrohydraulic active suspension can be classified among interlaced systems. This means that the state space model is a sequence of feedback and feedforward equations. Therefore, interlaced backstepping and integrator forwarding is an optimal control strategy to stabilize this class of systems, particularly electrohydraulic active suspension. Afterwards, we will introduce and define this constructive control method and its basis. The foremost advantage of this interlaced strategy is that, unlike others, it leaves no internal dynamic. This is a great relief in control issues, because an unstable internal dynamic will destabilize the whole system whatever control method is being used. As will be demonstrated, the interlaced backstepping and integrator forwarding is an outstanding control strategy to compensate the effect of chaotic roads on the stability of cars. The results are compared with a classic Proportional-Integral-Derivative regulator and a sliding mode controller, to show that the proposed controller outperforms a range of existing controllers for a range of perturbation signals.