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Active Engine Mounts for Improved Passenger Comfort
Published May 23, 2004 by Society of Automotive Engineers of Korea in South Korea
Automotive engine mounts are required to support the engine and limit the low frequency vibration resulting from road inputs. It is also necessary for the chassis to be isolated from high frequency engine vibrations resulting from the rotation of out-of-balance masses and gas ignition forces. These high frequency vibrations can excite components in contact with the driver and passengers (e.g., steering column and seat rails), and can generate significant acoustic noise. These effects are compounded as demand increases for vehicles that are both lighter in weight and more refined. Increasingly passive mounts are unable to meet requirements.
Active engine mounts can overcome this problem. In this case it is a design requirement that the active mount should be capable of being fitted to a range of vehicles without the need for special tuning. This requirement, combined with the fact that the vibration dynamics of the system are time-varying (e.g., with temperature and load), necessitates the use of an adaptive control algorithm that will operate with no a priori knowledge of the system dynamics.
This paper describes the application of a fully adaptive control strategy based upon the Filtered-X LMS algorithm. The algorithm is applied to an active mount fitted to a saloon car equipped with a four- cylinder turbo-diesel engine. The performance of the mount is assessed in terms of speed of response, stability and level of cancellation under typical driving conditions.
The mount is found to perform well, achieving up to 90% cancellation with good transient performance and stability. This reduction in chassis vibration significantly reduces audible boom and the vibration transmitted to components in contact with occupants, improving passenger comfort.