Approximation-free finite-time control for uncertain active suspensions with unknown time-varying input delays

This article investigates a new approximation-free finite-time control method for active suspension systems (ASSs) to address uncertain nonlinearities and unknown time-varying input delays (UTIDs), while enhancing suspension performance. First, to improve the transient performance of ASSs, a unique finite-time prescribed performance function (FPPF) is designed to ensure that the suspension motion converges to a predetermined range within a finite time. Then, a novel compensator is developed to resolve the impact of unknown input delays in the closed-loop system. Finally, an approximation-free finite-time control method is presented for uncertain ASSs using the FPPF and the compensator. In this method, neural networks and fuzzy logic systems are not required to handle system uncertainties, and finite-time prescribed performance convergence of suspension motion can be achieved even in the presence of UTIDs. To exhibit the usefulness of the proposed method, a combined dynamic simulator is built using MATLAB and Simpack, a professional vehicle simulation software. Simulation results are presented to validate the effectiveness of the proposed method and show improved suspension performance.