The Study Of The Isolation Characteristics Of An Active Control Hydraulic Mount With Electromagnetic-actuator

The ride comfort is one of the most important criteria in the market. As a result, the noise, vibration and harshness (NVH) characteristics are seriously taken into account in designing an automobile. As the same time, customers want to reduce the expenditure on their cars, and governments want to control the air pollution from cars, so there is a strong requirement for fuel efficiency. To improve fuel efficiency, makers are trying to improve engine performance and to cut down the weight of automobiles, but there measures are harmful to the NVH characteristics.Engines are one of the most important sources of noise and vibration in automobiles, so the isolation of engine vibration is critical to the improvement of NVH characteristics. Mount is a bridge that connects engine with chassis. High performance engine mounts can not only reduce the vibration that is transmitted by the engine to the vehicle chassis, eliminate"booming"sound inside the vehicle interior, but also provide the engine-transmission assembly superior protection. The primary function of engine mounts is to support the weight of the engine, and effectively isolate the vibration. Conventional elastomeric mounts and hydraulic mounts are unable to satisfy these two aspects synchronously, one solution to this problem is active mounts. At present many motor corporation and R&D institution pay attention to the research and design of active engine mounts.The active control hydraulic mount with electromagnetic-actuator researched in this paper consists of intrinsic passive hydraulic mount and electromagnetic-actuator. Because hydraulic mounts have superior isolation ability in the low frequency range, and electromagnetic actuator can provide favorable active vibration control performance in relative high frequency range, so the active engine mount can isolation the vibration of engine in much widerfrequency range.First, this paper introduces the history of mounts, based on large amount of internal and external thesis. The representative structures of different active mounts have been introduced in detail, and the advantage and disadvantage of different type mount have been list. From the history of mount, we can know that there is an trend to use active engine mounts with good performance.Secondly, several different actuators have been introduced in the active vibration control, and the advantage and disadvantage of different type actuators have been listed. Electromagnetic actuators satisfy the requirements of the active engine mount. Because the voice coil actuators are compact, have a high frequency bandwidth and generate a force outputs linearly proportional to input current. The characteristics of electromagnetic actuators is studied, and on the physical model and mathematic model is built, and then the performance is simulated in Matlab, we can find out that voice coil actuators can generate a force outputs linearly proportional to input current from the result of simulation.The control schemes for active vibration isolation can be classified into two categories: feedback and feedforword controllers. The advantage and disadvantage of different schemes have been analyzed. The feedforward controllers are generally accepted to be more advantageous in active vibration control. However, parameters of system vary from system and change according to the ageing of system. So an adaptive nature is introduced to feedforword controllers to resolve this problem because it enables the feedforward controllers to adjust themselves according to such variations. The filtered-X LMS algorithm is adopted for its simple structure and good performance. As the same time, the development and improvement of LMS algorithm is introduced in detail. The characteristics and stability of the LMS algorithm is analyzed.The reason for engine vibration is analyzed, and the design theory and structure of the active engine mount with electromagnetic-actuator have beenintroduced. The mechanical and mathematical models of active engine mount have been built.On the foundation of the mathematics model that sets up in the front chapter, a Simulink model is set up in the end, and the performance with control and without control is simulated in Matlab. The result of the simulation indicates that the active engine mount can isolate the vibration that is transmitted by the engine to the vehicle chassis effectively. The transmitted force with control is less than 10% than that without control in five seconds. LMS algorithm works very well in the whole engine working frequency range from 600rmp to 5000rmp when the characteristics of the systems are varied. The result confirmed the adaptive ability and stability of the LMS algorithm. The active engine mount system is capable of significantly reducing the force transmitted through the active engine mount. The active engine mounts have been considered as the next generation of engine mount.