Asynchronous and synchronous load leveling compensation algorithm in airspring suspension

The electronically controlled air suspension system is usually used to control a vehicle height by regulating air mass of the air springs. One of the control challenges of the air suspension system is how to handle the time varying model uncertainties, such as vertical load of each corner, temperature and coupled geometric property of each corners. This paper proposes two different ways of the air suspension height control, the asynchronous control and the synchronous control, to handle the model uncertainties. The asynchronous control method regulates the height error by alternatively controlling front corners and rear corners. At each step, the front two corners or rear corners are selected alternatively to be controlled. On the other hand, the synchronous control method regulates the height differences among every corner to be within a small value at a given instance so the balance of the vehicle are maintained well while performing the height control. Because the normal forces on the four corners are assumed to be unknown, the synchronous control method is especially difficult because of the time varying model uncertainties. In this paper, fuzzy logic control is used to handle the difficulty caused by the uncertainties. Both the control methods are verified by the simulation.