Soft prescribed performance control of active seat suspension with uncertain dynamics

This paper proposes a soft prescribed performance control (SPPC) strategy for an active seat suspension system with uncertain dynamics. Its primary contribution lies in the innovative use of an auxiliary system, which is ingeniously integrated with the prescribed performance function (PPF) to transform traditional hard constraints into soft, manageable ones. This design effectively resolves the contradiction between vibration isolation and suspension deformation limits. The auxiliary system combined with PPF enables the controller to prioritize ride comfort under small disturbances by allowing larger suspension travel, while automatically prioritizing safety by actively constraining deformation before reaching physical limits under large excitations, thus preventing performance violation and controller singularity. An adaptive law is designed to estimate uncertainties like sprung mass and friction. Simulations and experiments confirm that the proposed SPPC outperforms H∞ and traditional adaptive backstepping controllers, offering superior vibration suppression and guaranteed safety.