Engine, chassis and cab of a heavy truck are susceptible to undesirable vibrations due to two sources of excitation: unbalanced forces in the reciprocating engine and disturbances from the road transmitted through the suspension system. Engine induced vibrations generally have frequency range of 30-250(Hz) with amplitudes less than 0.3(mm). To isolate the noise and the transmitted forces from the engine to the vehicle structure, it is desirable to reduce the stiffness and damping of the engine mounts. Nevertheless, this reduction is restrained by the limitations on the relative motion of the engine to satisfy mechanical constraints and the fact that the engine mounting system should stand the weight of the engine.

Furthermore, for road induced vibrations or vibrations from the engine at idle that typically have frequencies below 30(Hz) and amplitudes greater than 0.3(mm) , engine mounts should have high dynamic stiffness and damping. At present conventional elastomeric mounts are widely used for engine mounting systems for commercial vehicles. However, these mounts cannot fulfill the above mentioned conflicting characteristic requirements for the best isolation in case of road or/and engine induced vibrations. Therefore, to improve the noise and vibration isolation of commercial vehicles it is necessary to go beyond traditional passive isolators and use semi-active or active vibration control systems due to their capabilities of addressing the conflicting requirements in different road and engine conditions. To improve existing and develop new advanced engine mounts, validated and verified computational models of mounts are well desirable.

These models can especially be useful in analyzing the effects of frequency and amplitude of external excitation on dynamic stiffness and damping of a mount. The aim of the research project is to first develop mathematical and computational models of elastomeric engine mounts for heavy trucks and investigate the nonlinear behavior of dynamic stiffness and damping of the mounts, and finally use the developed models to design and analyze an adaptronic engine mounting system and vehicle suspensions. Adaptronic engine mounting system is referred to a mounting system where actuators, sensors and controller are incorporated optimally in the conventional elastomeric mounting system.

The developed computational model of the engine mounts was implemented in Matlab/Simulink and used in a 3D engine model with which vibration dynamics analysis under different engine excitations and realistic road inputs are conducted. Using the developed model, stiffness and damping of engine mounts, which are in use for commercial vehicle engine mounting system, have been estimated for a frequency range of 5-100 (Hz) and amplitude range of 0.025-2 (mm). It has been shown that the changes of mounts’ stiffness are up to %33 with respect to amplitude and %28 with frequency changes. Nondimensional damping changes up to %40 and %490 with the change in amplitude and frequency of excitation, respectively. The model has been validated against measurement data for harmonic excitations of conventional mounts. For different inputs of amplitude and frequency, the model shows a good and practically admissible agreement with the measurement data. The tolerances of estimation of stif fness and damping regarding the measurement data do not exceed 11 %.

The possibility and advantages of using active engine mounts have been studied by incorporating actuators into the above mentioned 3D engine model with conventional mounting system for heavy trucks. Simulations of the engine vibration dynamics under similar engine and road excitations have also been done for the adaptronic mounting system and compared to the results from the conventional engine mounting system. The results of simulations of engine vibration dynamics and transmitted forces to the vehicle structure have shown good potential for vibration isolation improvement in heavy trucks by using adaptronic engine mounting systems In continuation of this research, Pareto optimality approach will be applied to the engine mount parameter determination for different frequency regions.

A model with more degrees of freedom for the wheel suspension and for the chassis will be used in Pareto optimality. In addition, more advanced dynamics of the actuators will be used so that within the given concept the actuators will be optimally designed with restrictions on the maximum exerted force. There is also a need to optimize the location of the actuators.

Another issue is solving the optimal control problem considering the controller design.