A new controller based on the modified Riccati-like Equation is developed in this paper. The interval type 2 fuzzy model is applied and embedded in the controller to ensure the robustness to parameter uncertainties and also to support calculation progress. The proposed input control includes equivalent control and robustness control. The equivalent control is found from the conventional analysis with the sliding surface, but this control is not sufficient to resolve the uncertainties and disturbances such as error approximation of the fuzzy model. Thus, a proportional-integral-derivative (PID) controller and matrices of the traditional model of Riccati equation are utilized to ensure the robustness. In the synthesis of this control part, the H infinity technique is adopted and the stability of the system is proved using Lyapunov stability. Subsequently, to validate the effectiveness of the proposed controller, it was applied to vibration control of a vehicle seat suspension with a magnetorheological (MR) damper subjected to stiffness variation due to the magnitude of the input current. In this problem, two types of road conditions, bump and random step wave, were adopted and control performance was evaluated in both simulations and experiments. Based on these evaluations, the proposed controller provides high control performances, effectively controlling the acceleration and displacement at the driver position.
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