Study On Crucial Technology Of Active Vibration Isolation System Based On Structure-Optimized Giant Magnetostrictive Actuator

With the advancement of active control on vibration, higher demands on actuator catalyze the creation and development of intelligent materials. Due to its giant magnetostrictive strain, high power density, high electromechanical coupling coefficient and high response speed, the giant magnetostrictive actuator (GMA) has been widely concerned in the field of intelligent actuator by researchers in China and abroad. However, there're also many disadvantages which challenge its actual application, such as nonlinearity, hysteresis and radiation. Based on the analysis of the giant magnetostrictive phenomenon and its form mechanism, research of optimization design which could improve the performance of the GMA are processed as follows:1) Magnetism material is used to make the inner wall and the two tips of GMA in order to form a closed loop around the giant magnetostrictive material (GMM) rod. Two pieces of magnetizer are placed at each end of GMM to proportion the distribution of magnetic field in GMA and reduce the leakage of magnetism.2) Methods of selecting the intensity of pre-magnetic field and drive magnetic field are discussed to increase linearity and to eliminate frequency multiplication in GMA.3) Pre-pressure is applied to GMM by a spring to improve the ratio of expansion, and the rigidity of the spring is optimized.4) The shape of the drive solenoid is optimized to enhance the work efficiency of GMA.5) GMM is cut into small slices along the axes so that the whirlpool effect is weakened.6) The traditional water cooling controlling system is replaced by configuration with rib, which makes the application of GMA more flexible and convenient.7) To reduce the disturbance to other equipments around it, GMA is shielded with non-magnetism material.Principles of vibration isolation (VI) are intensively analyzed after finishing the optimization design of GMA. An opinion that the essential of VI here is displacement tracking is proposed, which is compared with traditional force control. Then the model of VI platform is established based on displacement tracking, and how the parameters of passive VI affects the VI capability of the whole system is discussed. Simulation results show that displacement tracking has better performance of stability and less steady-state error than force control does.About control arithmetic, a new arithmetic of constraint weight function based on normalized LMS which originates from minimum mean square adaptive LMS is raised in order to improve the stability of system. This new arithmetic has both the advantages of changeable step LMS and constraint weight function. In the active vibration isolation system, the effect of secondary path is very important, and it's usually solved by using on line identification. But the white noise used in the identification enters into the error signal which would damage the performance of the system. In this dissertation the white noise is separated from the error signal by using improved Fx-LMS arithmetic to increase the identification precision and system capability.Furthermore, the actual output ability of the controller is often neglected by people while doing researches on control arithmetic, this could make the elements burnt while in practice. But high frequency noise will be brought in if simply using slicing to protect the elements. A new error constraint adaptive control arithmetic is proposed in this dissertation to solve those problems above, which could restrict the feedback signal to make system achieve a non-zero convergence. Simulation results show that this method could protect the elements without bringing in high frequency noise.Experiments are done with the equipments available about control arithmetic in order to validate the ideas and simulations above. Signal generator is used to simulate the vibration of the platform, and the displacement outputs of the actuators are controlled to follow the vibration signal, while the actual displacements of the actuators are tested by displacement sensors. Simulation results show that the arithmetic proposed in this paper could control the periodic signal and has a good stability.Next, both static and compatible simulations of GMA are done by piezoelectric- piezomagnetic analogy, mainly using ANSYS. Results show that the design of the actuators here is proper as the performance is good.Last, after finishing the capability checkout of the actuator, a virtual vibration isolation platform based on GMA is built using UG, MATLAB and ADAMS, and simulations of the proposed algorithms and the system model are done on this platform for proof. Results show that the model is simple and effective and the arithmetic proposed in the paper could implement the vibration isolation and also has a good stability, so it might be used for reference in engineering application.