ACTIVE ENGINE MOUNTS

Active Engine Mounts



Active Engine Mounts

Introduction

The perfect engine mount system should isolate engine vibration caused by engine disturbance force in motor pace variety and prevent engine rebound from shock excitation. This suggests that the dynamic stiffness and damping of the engine climb on should be frequency and amplitude dependent. (Kevin, 2000, pp. 10)The conventional active engine mounts do not meet all the requirements and can only offer a trade-off between static deflection and vibration isolation, but there is still some room for improving the properties of active engine mounts. (Vessel, 2004, pp. 80)

Passive hydraulic mounts can supply a better presentation than elastomeric mounts particularly in the reduced frequency range. Semi-active techniques are usually used to farther improve presentation of hydraulic mounts by making them more appropriate. (Sammy, 2005, pp. 35)The optimisation of the engine mounting scheme is rather useful both in periods of hasten and more effective design. (Simon, 2006, pp. 99) This will have a large influence on controller synthesis, performance, and stability verifications. (Kevin, 2000, pp. 10)

Review of Relevant Literature

This paper deals with active vibration isolation of an automobile engine. The engine is a three point suspended 5-cylinder combustion diesel engine that is attached to the vehicle body at the left and right hand sides via two rubber engine mounts. Furthermore, it is also connected to the sub frame via a torque rod with rubber bushings at both ends. (Vessel, 2004, pp. 80)The active engine mounts suspension scheme has to support the engine at static equilibrium state, avert large movements due to transient and reduced frequency street excitations, and isolate engine dynamic vibration developed by motor and road excitations for distinct gearing ratios in the whole variety of engine rotational speed. The physical system is non-linear due to material characteristics (rubber) and large displacements. (Kevin, 2000, pp. 10)

Global complete vehicle co-ordinates system as well as the local one of the engine. The vehicle co-ordinate system has its origin outside the vehicle front, its x-axis pointing longitudinally from the vehicle front to its rear, and its z-axis pointing upwards. Whereas the local engine co-ordinate system located at centre of gravity of the engine with x-axis aligned with the centre line of the crankshaft pointing towards the gearbox and z-axis being parallel with the cylinder bores pointing upwards. (Sammy, 2005, pp. 35)

The Active Engine Mount System solution presented in this work is based on active engine mounts schematically shown using a simplified SISO model, where Fs is the actuator for ce and Fp corresponds to the internal and external engine excitation. M is the mass of the engine, K and C are the stiffness and damping of passive isolation elements in parallel to the actuator, i.e. representing a passive mount, x is the mass displacement relative the static equilibrium position and Fy represents a feedback controller force. For an AES system with main objective to suppress spectral components of excitations at and above the natural frequencies of the passive engine suspension system, this configuration has certain good properties, ...