Layne Clemen, and Donald Margolis
Active suspensions have been a popular area of research for many years but due to power consumption and corresponding degradation of fuel economy, they have seldom been implemented in production vehicles. In this paper, a quarter car model of an active suspension including an electrodynamic damper and air spring is developed using bond graph techniques. The model incorporates two components into a quarter car model: a simplistic regenerative damper model and a variable-volume air spring. This model enables control design using multiple techniques. Due to the nonlinearities inherent in the air spring thermodynamics, linear control techniques are difficult to use. Using the nonlinear equations derived from the bond graph model, a sliding mode controller is designed for the system to regulate the ride. Simulation results show that the energy-regenerating damper is capable of harvesting enough power to sustain an active suspension on a normal roadway and that sliding mode control out-performs traditional linear control techniques.