Nonlinear Sliding Mode Controller for Automotive Engine Vibration Isolation With Model Uncertainties

One of the primary concerns in the automotive industry is how to improve passenger comfort by attenuating unwanted vibrations. In vehicles, car manufacturers use engine mounts to support the engine and isolate vibrations while it is running. Although passive engine mounts have been widely used in many commercial vehicles, they are only effective within a limited range of excitation frequencies. To overcome this limitation, active engine mounts have been introduced. The advantage of the active engine mounting technique is that it can be very stiff at low frequencies and tuned to be very soft at higher frequencies to isolate vibrations. An electromagnetic actuator is generally used in active engine mounts to generate the counterforce that cancels out vibrations. Thus, the dynamic force of the actuator must be designed in such a way as to isolate engine vibration. In this paper, a nonlinear sliding mode control method for active engine vibration isolation is adopted to attenuate vehicle engine vibrations. The proposed controller employs a logarithm-based switching function to create a boundary state that forces the vibration amplitude to be reduced within the maximum amplitude set by the designer. Simulation results show that the proposed logarithm-based sliding mode controller not only performs better in terms of vibration isolation, but also robust in the presence of model uncertainty.