SYNERGETIC SYNTHESIS OF SLIDING MODE CONTROL FOR VEHICLE’S ACTIVE SUSPENSION SYSTEM

Abstract

This article discusses the problem of designing vehicle’s active suspension systems in which the actuator is not ideal and is a subject to the influence of hysteresis and dead zone. The main goal of this work is to synthesize a control system that reduces the influence of hysteresis and deadzone on the efficiency of the adaptive suspension system. System parameters like hysteresis require significant efforts to identify them and, moreover, can vary widely over the life cycle of the system. Thus, it is very difficult to take into account hysteresis in the synthesis of the control system, as well as the construction of observers. The solution to this problem is use of sliding control systems, which to a certain extent are robust to parametric and structural changes in the control object. Existing approaches to the synthesis of sliding control systems are based on a linear or linearized model of the control object. Thus, the effectiveness of such systems can vary significantly when the regulator operates as part of a real, non-linear control object. The proposed sliding mode control allows to reducing sensitivity of the system to disturbances due to imperfect actuator, and also takes into account the nonlinear structure of the control object. The efficiency of a closed system is investigated on a dynamic model built in Simulink package. The proposed controller is compared with an adaptive synergetic regulator. Road of class C (according to ISO 8608 classification) was selected as a disturbance. To investigate the effectiveness of the proposed control system, the following parameters are evaluated: weighted acceleration of the sprung mass; relative motion of suspension and tire reaction force. The RMS and maximum values are calculated for each parameter. The results of numerical simulations allow to conclude that the use of sliding control systems can improve the following adaptive suspension performance indicators: reduce the maximum value of the weighted acceleration of the sprung mass by more than two times and reduce the maximum load on the tire by more than 20 %.