Design of an Adaptive Fuzzy Observer-Based Fault Tolerant Controller for Pneumatic Active Suspension With Displacement Constraint

Abstract

This paper proposes an adaptive fuzzy observer based fault tolerant controller for a pneumatic active suspension system considering unknown parameters, actuator failures, and displacement constraints. A pneumatic spring is used for a quarter car model to enhance the vibration attenuation performance. Since the pneumatic system contains uncertain nonlinearities, fuzzy logic systems are utilized to approximate unknown nonlinear functions of unmodeled dynamics and various masses of passengers. Besides, a nonlinear disturbance observer is proposed to estimate the effects of the actuator failures, approximation errors, and external disturbances. By utilizing the disturbance estimation and fuzzy approximation techniques, an adaptive fault tolerant control (FTC) is designed to enhance the output performance of the vehicle suspension. Meanwhile, the command filtered scheme is introduced to solve the explosion of complexity problem in the traditional backstepping approach by avoiding virtual controller derivatives. In contrast to previous results, the proposed control can handle the fault tolerant problem and ensure the tracking error of vertical displacement converges into a small-predefined boundary by introducing the prescribed performance function. Moreover, the stability of the closed-loop system is analyzed according to the Lyapunov theory. Finally, comparative simulation examples and experimental studies are performed on the active pneumatic suspension test bench to verify the feasibility of the proposed scheme.INDEX TERMS Active suspension systems (ASSs), nonlinear disturbance observer (NDOB), prescribed performance function (PPF), fuzzy logic systems (FLSs), command filtered control (CFC).

A Review of Fuzzy Logic Method Development in Hydraulic and Pneumatic Systems

“…In turn, Ho et al conducted a series of studies on various aspects of active air suspension control using fuzzy logic. Ho consecutively published the results of their research on the design of an adaptive observer-based fuzzy controller with displacement constraints [64], on similar research with considered actuator failures [65], and on a suspension with the unknown death zone [66].…”

Adaptive Fuzzy Observer Control for Half-Car Active Suspension Systems with Prescribed Performance and Actuator Fault

“…where (27) Based on Equation ( 27), the unknown function F v (X v ) contains the effectiveness factors of actuator failures µ v and φ v that cannot be determined. The mass of passengers is an uncertain parameter, which cannot be applied to the control design.…”

“…Instead, many proposed controllers assume that the ideal actuators are used to dissipate external vibration even though the non-smooth nature of actuator failure can destroy the suspension performance [24]. To improve the control efficiency and ensure system stability, the issue of fault-tolerant control should be investigated for vehicle suspension [25][26][27]. Liu et al [28] proposed an adaptive faulttolerant control problem to stabilize vehicle suspension under the effect of unknown actuator failures.…”