Study And Optimization Of The Characteristics Of A 3-axis BD Optical Head Actuator

In this dissertation, a 3-axis 5°wire-angle optical head actuator has been simulated by using magnetic analysis, model analysis and harmonic analysis, and the 3-axis BD actuator simulating model is built after comparing the emulated results with the experiments, and also the effective stiffness model and the sensitivity of the actuator has been carried out for theory investigation and optimization.Firstly, the rules of focusing and tracking of optical actuator and the components of optical head are introduced. The actuator is one of the most components of the optical head in optical storage, and the characteristics of actuator determine the capability of the optical head. Along with the development of optical storage, the conventional 2-axis optical wire actuator can't meet with the needs after the invention of BD storage, and the 3-axie optical wire actuator is for the new challenge. The civil research on actuator is only on 2-axis actuator, the study on 3-axis actuator is a big blank. The 3-axis actuator has more complex structure and higher sensitivity relative to 2-axis actuator, and the size of actuator is smaller, therefore, the 3-axis actuator has super research value. The main characterics of actuator are characterics of focusing direction and tracking direction, the characterics of the directions and its experiment methods as well as the principle of focusing and tracking are measured and introduced.The magnetic field analytic model of 3-axis BD optical head actuator is built. The 3-axis actuator is to achieve focus move, track move and tilt move because of the force on the coils in the magnetic fields. The theories models of the magnetic fields of actuator is built, and magnetic poralized theory is for magnet analysis, and Biot - Savart Law is for coils analysis. By using finite element method software ANSYS, structure model for coils model and the current density for current source is set up, and the magnetic fields distribution on coils and the force distribution on coils are gotten with MVP method after the vector element SOLID97 for dispersing.The low frequency characteristic analysis model of 3-axis BD actuator is achieved. The main parts of 3-axis actuator are movable part and unmovable part, among them, the unmovable part is mainly consist of magnets and the iron, and also the movable part is made up of lens, frame of lens, five groups of coils and six hanging wires. The actuator always lies to state of vibration when it works. The main characteristics of actuator are the first resonance frequency, the first resonance peak, 5Hz sensitivity, and 200Hz sensitivity and so on. so the model analysis of the software ANSYS is used to get the modes of movable part. The main modes of movable part in low frequency region are the focus mode, track mode and tilt mode, and they are 50.5Hz, 54.8Hz and 205.2Hz respectively, and the error in the three direction is less than 1% after compard with the experiment results. The modes of actuator in high region are the flexibility resonance, and the second resonance frequency of movable part is above 20 kHz. The harmonic analysis of ANSYS software is used to simulate the characteristics of actuator, and the effective damp matrix is calculated for the damping effect of actuator, and the results error of simulation is less than 5% after compared with experiment results.The effective stiffness model of 3-axis BD actuator is set up with mechanics of materials in three directions. According to vibration theory, the six hanging wires of movable part can be regarded as ideal cantilever and they are parallel joint. Through the force analysis for wires, deflection method in materials mechanics is used for solving the effective stiffness model in three directions, and the effective stiffness model is only 5% less error comparing with experiment. The length of wire, the radius of wire, the wire-angle of wire, the different sections of wire and the different sections for six wires are simulated for the first resonance frequency of actuator.The sensitivity of 3-axis BD acutaotr is optimized after selecting the seven magnetic parameters by using taguchi method. Seven parameters of magnetic fields are refined for sensitivity optimization, and the L₁₈( 3⁷) table is set up, and the results show the distance of magnets and the polared direction are main parameter, and the sensitivity of optimization can be increased nearly 40%.