Challenges in Controlling Active Suspensions for High-Speed Off-Road Vehicles

Abstract

Abstract The literature includes several useful control approaches for active suspension of off-road vehicles. Some of these approaches rely on preview (look-ahead) of the terrain, while others require knowledge of certain variables that have proven difficult to measure reliably for off-road applications. Sky-hook damping is a widely accepted active suspension control law. Experimental and analytical research with active suspension systems for on- and off-road vehicles have successfully demonstrated substantial improvement in ride quality. The paper begins with a short discussion of a bond graph model of an off-road vehicle equipped with an electromechanical active suspension. The bond graph model facilitated the development of a SIMULINK model used for simulation. Comparison of simulation and experimental results has validated the model, especially for high-frequency terrain inputs. The paper examines how specific examples of off-road conditions challenge control algorithm development. Simulations demonstrate that sky-hook damping (without modification) with gains selected for very high attenuation of high-frequency terrain disturbances do not perform well in response to large displacement, low-frequency inputs and cause suspension bottoming out. By modifying the basic control laws and selecting appropriate controller gains, excellent ride performance was achieved in recent field tests under general terrain conditions.