Optimum Design Of Engine Mounting System And Software Development

Ride comfort is the main performance index for the automobile, especially for the car. There are two sources of vibration in a motor vehicle, one is the road surface random exciting while running; the other one is the vibration of the engine. In one hand, the fist one has been greatly reduced with the improvement of road condition and suspension system design, the influence in this aspect are lowered to a certain degree; on the other hand, the design of the modern car put emphasis on reducing the weight, adopting new-type, high-strength, light-nature materials in order to minimize the mass of the whole motor vehicle, But it is very difficult to reduce the weight of engine. Thus the proportion of the engine in the weight of the whole vehicle is increased. But most of the engine are four-cylinder four-stoke which have bad balance characteristic, most of the car use the integrity pattern and thin-cell-fabric body which leads to the increasing of the flexibility of the bodywork, thus the vibration exciting of the engine on the bodywork increases comparatively. So the vibration exciting of the engine becomes the main vibration source of the car. The rotation torque oscillation which output by the engine and vertical reciprocating inertia force which produced by the piston not only excite the rigid and elastic vibration of the engine, but also excite the torsional and bending vibration of the transmission system and all kinds of vibration of the car body and noise which produced by the air inside the passenger cabin resonances. So the vibration isolating characteristics of the engine mounting system have a great influence on the ride comfort of the car. An engine mounting system which is designed properly can not only reduce the force which is transmitted to the car body and the noise, but also increase the ride comfort and protect the powertrain effectively. How to design an engine mounting system which can isolate vibration of the engine from the rest of the vehicle effectively has became a difficult problem of car design. There are many design parameters which can affect the isolating characteristics, such as the stiffness and damper value of the mount, mount locations and orientations. The main task of the engine mounting system design is to make it has a good isolating performance by select the stiffness and damper value of the mount, mount locations and orientations rationally. For simplifying the engine mounting design and reducing the period of the engine mounting design, it is very necessary to develop software which can optimize the design of the engine mounting system. The main contents of the dissertation are as follows: 1. After referring many research papers about engine mount, the history of research about engine mounting system is summarized, the developing history of the engine mount is reviewed and the design method of the engine mounting system is also illustrated in detail. Then the developing trend is pointed out briefly. 2. The mechanical and mathematic model of rubber mount and hydraulic mount is set up; then the 6-Degree-of-Freedom model of engine mounting system is set up too. The characteristic of engine exciting is analyzed. The methods about intrinsic characteristic analysis, static analysis, dynamic analysis and vibration transmitting rate analysis are illustrated in detail. 3. The principle of engine mounting system design is analyzed in detail. Then the optimum design models with rational disposition of intrinsic frequency, decoupling the model kinetic energy of each mode, minimizing vibration transmitting rate, minimizing force transmitted though mounts and unified objective function as objective function is carried out. The conditions of those Non-Linear models using are pointed out also. In the end, the mathematic optimum methods of those Non-Linear models are analyzed and selected. For those Non-Linear models, the penalty function and Powell method are used. Those Non-Linear constrained programming problem is transformed to unconstrained optimization problem by using penalty function. Then solve this unconstrained optimization problem by using Powell method. 4. According to the Object-Oriented method of software design, the engine mounting system is studied using Object-Oriented Analysis and Object-Oriented...