Control of Automotive Air-Spring Suspension System Using Z-Number Based Fuzzy System

This paper presents the control of an automotive air-spring suspension system using a Z-number based fuzzy inference system. One of automotive suspension functions is to isolate vehicle body from road disturbance which is described by transmissibility coefficient. There is a conflict between ride comfort and handling requirements. Lower transmissibility coefficient results in improving passengers’ comfort. In this study, an air-spring suspension system is connected to two additional volumes of different sizes via ON-OFF valves that are controlled by the proposed control strategy. The stiffness of the suspension system is the control parameter that is controlled by changing the enclosed pressure and the total air volume inside the air-spring within one of four chosen levels. The proposed Z-number control scheme is characterized by two components; constraint and reliability. The interpolating reasoning of the Z-number fuzzy is constructed and applied. Genetic Algorithm is used to estimate the optimal control gains and switching levels of the air volumes. The proposed control system is applied to a simulated quarter car model to evaluate system performance. Then, the proposed controller is compared to a conventional fuzzy controller and a fuzzy controller merged with discrete volume control. The results show that the proposed controller improves the air suspension performance compared to the other controllers with a maximum acceleration of 1.1 cm/s2.