Idle shake vibration optimization of an engine mounting system through the practical application of transfer path analysis

This article presents a practical application of experimental transfer path analysis (TPA) for optimizing idle shake vibrations of a front-wheel-drive car with a transversely mounted four-cylinder diesel engine. Performance control of the vehicle engine mounting system must take into account the multiple dynamic interactions between the engine mounting system, subframe modes and the vehicle suspension. Experimental methods can be used in conjunction with simulations to design and optimize the engine mounting system. TPA is a powerful tool for the diagnosis of vibration and noise transmission via multiple solid paths. TPA allows a quick diagnosis of the engine mounting system performances on vehicle comfort. A strong synergy between numerical model and experimental data finally makes it possible to find better design alternatives, not necessarily obvious to the designer. This study is the guideline for an optimization of the engine mount noise vibration and harshness (NVH) performances by using a hybrid approach, combining an analytical approach and measurement data. First, a diagnosis of the transmission of structure-borne vibrations via the engine mounting system to the seat floor is done at constant idle speed. This method is used to rank individual engine mount contributions in the low-frequency vibration level inside the vehicle. Then, an original approach allows the optimization of the vibration level at idle speed by offsetting contributions of the engine mount paths by adding damping in the right engine mount. This approach has led to the design and validation of an original double inertia-track hydroelastic mount prototype which allows a 5-dB reduction on the seat floor vibration level. The future development of a new version is planned to confirm and optimized the obtained results. The length of the second inertia track will be increased to reach the targeted characteristics, and the adjustment system will be removed to respect the overall dimension constraints of the mount.

Active Engine Vibration Isolation Using Robust Control

This paper introduces a prototype active engine mount (AEM) system designed for commercial passenger, requiring a good engine vibration solation performance. The AEM consists of a conventional hydraulic engine mount and an internal electromagnetic actuator. The robust H controller was adopted to cancel out the force transmitted through the AEM. The vibration isolation performance tests were carried out by simulating the engine idle shake. The experimental result confirmed that can control unwanted vibration from the engine operation by using active mounts.

Application of Evolutionary Computation in Automotive Powertrain Mount Tuning

Engine mount tuning is a multi-disciplinary exercise since it affects Idle-shake, Road-shake and power-train noise response. Engine inertia is often used as a tuned absorber for controlling suspension resonance related road-shake issues. Last but not least, vehicle ride and handling may also be affected by mount tuning. In this work, Torque-Roll-Axis (TRA) decoupling of the rigid powertrain was used as a starting point for mount tuning. Nodal point of flexible powertrain bending was used to define the envelop for transmission mount locations. The frequency corresponding to the decoupled roll mode of the rigid powertrain was then adjusted for idle-shake and road-shake response management.A TRA decoupling procedure, cast as a multi-objective optimization problem, was applied to a body-on-frame sport-utility vehicle powertrain system. In addition to a standard gradient based optimization algorithm, available in commercial finite element software, an evolutionary computation paradigm known as Evolutionary Strategies (ES) was used to solve the optimization problem. The primary advantages of evolutionary computation over gradient based algorithms are as follows: i) They are less likely to get trapped in local minima and less dependent on initial values of the design parameters and therefore able to handle multi-modal optimization problems unlike gradient based algorithms, ii) They produce a population of viable solutions, unlike gradient based algorithms which yields a single solution. The second advantage is very attractive in a production environment since packaging and other multi-disciplinary constraints often require multiple quality solutions for the same problem. The process outlined in this work was verified by exercising a full-vehicle finite element model. The process produced a set of production feasible powertrain mount parameters for acceptable idle and road shake performance.

Tuning of a Rear Electronic Control Engine Mount

This paper refers to mathematical tuning, by the sinusoidal steady-state transfer function method, of an adjustable hydraulic rear engine mount for reduction of perceived vibration during engine idle situations. The problem being addressed, in particular, is the reduction of “idle shake”. The accuracy of this method is confirmed by individual component testing along with in situ vibration measurements. During this work, a general approach to transfer function calculation is given by evaluating the system components with the linear-graph system of modeling. This is complemented by component verification and curve-fitting to arrive at the final transfer function which reveals the inherent tendencies of the overall system. Secondary measurements are then employed to rectify the contradiction between mathematical values and subjective results.