A Study On Active Control Engine Mount

The ride comfort is used as one of the most important guide line to estimate the automobiles'especially the cars'capability. So the NVH (Noise, Vibration and Harshness) characteristics reflecting the ride comfort get much more attention. Engine is a primary factor to bring the vibration and noise of automobile. How to isolate the engine vibration has become the key to improve the NVH characteristics of the whole vehicle. Mount is a bridge connecting the engine and the body, and is also a transfer path between the power-plant and the body. A favorable engine mounting system not only can reduce the force transferred to the frame, decrease the vibration and noise inside the body, enhance the ride comfort, but also can protect the engine mounting system better. For that the structure characteristic of conventional passive mount and semi-active mount can not satisfy the isolation requirement of vehicles'many working states, the design and exploitation of active mount becomes the key technology to solve the vibration isolation of power-plant.Based on the independence exploitation of active engine mount, the structure and the working principle of active mount system, the electromagnetic actuator and the design of active control system are discussed deeply. Simulation and test about the dynamic characteristics of active mount are analyzed and researched. The active mount with electromagnetic actuator is designed. The adaptive feed-forward control strategy is used to design the active control system. The isolation effect of active mount is validated through computer analysis technology and test research. The research work in the dissertation provides the exploring research and the technology preparation for the active mount design and application. The main research work follows:Several actuators of vibration active control are introduced based on a great deal of domestic and overseas reference papers. The advantages and disadvantages of these actuators are analyzed and compared. Electromagnetic actuator becomes the executer of the active mount in the dissertation for its advantages of compact structure, low expending, sensitive reaction, wide frequency band, and big displacement. Then electromagnetic actuator is used as research object. Its elements and characteristics are analyzed. The mechanical model and mathematical model of it are set up. The capability of it is simulated. The results of the simulation indicate that there exists obvious linear relation between the action force and the control voltage of the electromagnetic actuator. This is in favor of active control. Then the effect on capability of actuators'structure parameters are analyzed, it supplies the theory foundation for the design and parameters choice of electromagnetic actuator.The electromagnetic actuator adapt to vibration active control is designed and made. The test research of electromagnetic actuator is accomplished. The results of test and simulation inosculate well. This proves the correctness of the simulation model, and meanwhile establishes the foundation of active mounts'design and manufacture.Several kinds of control arithmetic usually used in active mount control are recommended. The feed-forward control method is used in the dissertation based on comparing the feed-forward control method with the feedback one. Because the continuous change of the systems'parameters (dynamic stiffness and damping) in actual application, adaptive feed-forward control method and filtered-X LMS algorithm are used in this dissertation. LMS algorithm is described in detail. The traits, stability and convergence are analyzed. Then the expression of algorithm and the control flow in actual control application are given.The state and dynamic characteristics of the hydraulic mount is studied. Start with the resolution of the question that dynamic stiffness in high frequency is too high, the design idea and the basic structure of active mount are put forward, an active mount with its electromagnetic actuator driving the decouple directly is designed. The mechanical model and simulation model of active mount is built up. The dynamic characteristics of active mount is simulated and tested. The results of simulation and test inosculate well, and it can be used to supervise the theory research and the design of active mount.The mechanical model of vehicle active mount is built up. The simulation model is set up by using the simulink module of Matlab software, this model can simulate many working states of vehicle isolation capability. The vibration source of engine is analyzed. The calculation formula of four-cylinder-four-stroke engine's second order inertial force is deduced. The off-line simulation research of active mount systems'isolation capability is executed. The simulation results indicate that:①The off-line simulation model has the functions needed for the active mount study.②The vibration transferred to body from engine is effectively decreased by active mount in idle speed.③The vibration of engine and the noise in cab can be obviously attenuated by active mount in high running speed. The NVH capability is effectively advanced.The research indicates that: following the varieties of system parameters, LMS algorithm can make the active mount system convergence in short time, and adjust the isolation capability of system to be best. These prove that the adaptive ability and the stability of LMS algorithm, and this algorithm is fit for application in active mount.According to the research of engine mount system, vibration acceleration is used as evaluation guide line, the hardware-in-loop-test-bed of active engine mount system is set up. The characteristics of the test-bed as follows:①Through the control of motor's rotate speed by transducer to realize the aim of controlling the vehicle's working state.②The software system of test-bed is exploited by C program language to carry out the data collection and processing for different vehicle working states.③The signal processing system consists of data acquisition card and power amplifier is used to accomplish the collection of acceleration sensors'signal and the driving of the electromagnetic actuator.④The dynamic simulation of vehicle mount system's working states is executed indoor, and this makes the design period of active mount consumedly shorten.⑤The test research of active mount is achieved on this test-bed. The results indicate that active mount can decrease the transmissibility of the engine vibration to the body, meanwhile it proves the correctness of the simulation results before.The domestic active isolation technology of power-plant is still in primary stage. The foreign corrrelative reports is a few. Several key technology needs to be solved. The research work in this dissertation has supervising meaning for the study and design of power-plant active isolation system.