Comparative Evaluation of Quarter-Car-Model-Based Modular Synthesis and Symmetry-Based Full-Car-Based Centralized Synthesis for Active Suspension Control

This paper presents a comparative evaluation of quarter-car-model-based modular synthesis (QCMS) and full-car-based centralized synthesis (FCCS) for active suspension control in full-car systems. FCCS explicitly accounts for the coupled vertical, pitch, and roll dynamics by incorporating the geometric configuration of the sprung mass; however, this centralized formulation increases model complexity and controller–synthesis effort. In contrast, QCMS reduces the synthesis complexity by designing local suspension controllers using a quarter-car model and applying them modularly to the four suspension corners of a full-car system. Within both synthesis frameworks, linear quadratic (LQ) static output feedback (SOF) controllers and recursive-least-squares/extended-Kalman-filter (RLS/EKF)-based controllers are developed under comparable but structurally different control objectives. In particular, the proposed FCCS framework uses the geometric symmetry of the sprung mass not merely as a modeling assumption but as an explicit force-allocation structure that transforms the desired vertical force, roll moment, and pitch moment into four suspension actuator forces. Thus, four controllers are considered: LQSOF-QCMS and RLS/EKF-QCMS as modular quarter-car-based controllers, and LQSOF-FCCS and RLS/EKF-FCCS as centralized full-car-based controllers. In addition, the computational complexity of the LQSOF- and RLS/EKF-based controllers is compared in terms of their implementation burden. The main contribution of this study is not merely to show that the full-car-based FCCS improves the suppression of coupled body motions, but to clarify, under identical control and simulation conditions, the quantitative trade-off between the modular simplicity of QCMS and the symmetry-based centralized performance of FCCS. These controllers are evaluated through CarSim-based simulations under selected representative road-profile conditions in terms of ride comfort, motion-sickness mitigation, sensor requirements, and implementation complexity. The simulation results show that QCMS offers a low-complexity and modular implementation with acceptable ride-comfort performance, whereas FCCS justifies its increased synthesis and implementation burden when the suppression of coupled vertical, pitch, and roll motions and motion-sickness-related responses is required.