LMI-based robust model predictive control for a quarter car with series active variable geometry suspension

TL;DR

This paper introduces a robust model predictive control method based on linear matrix inequalities for a quarter car with a series active variable geometry suspension, enhancing ride comfort and road holding under various road conditions.

Contribution

It develops a new uncertain system model for SAVGS that captures unmodeled dynamics and disturbances, and integrates an LMI-based RMPC scheme with the nonlinear system for improved control.

Findings

Demonstrates robustness against unmodeled dynamics and disturbances.

Achieves significant performance improvements over passive and H-infinity controlled SAVGS.

Validates effectiveness through numerical simulations with ISO road events.

Abstract

This paper proposes a robust model predictive control-based solution for the recently introduced series active variable geometry suspension (SAVGS) to improve the ride comfort and road holding of a quarter car. In order to close the gap between the nonlinear multi-body SAVGS model and its linear equivalent, a new uncertain system characterization is proposed that captures unmodeled dynamics, parameter variation, and external disturbances. Based on the newly proposed linear uncertain model for the quarter car SAVGS system, a constrained optimal control problem (OCP) is presented in the form of a linear matrix inequality (LMI) optimization. More specifically, utilizing semidefinite relaxation techniques a state-feedback robust model predictive control (RMPC) scheme is presented and integrated with the nonlinear multi-body SAVGS model, where state-feedback gain and control perturbation are computed online to optimise performance, while physical and design constraints are preserved. Numerical simulation results with different ISO-defined road events demonstrate the robustness and significant performance improvement in terms of ride comfort and road holding of the proposed approach, as compared to the conventional passive suspension, as well as, to actively controlled SAVGS by a previously developed conventional H-infinity control scheme.