| High precision micro displacement technology is one of the key technologies of precision engineering and precision instrument. The micro displacement technology is widely applied in the manufacturing and testing of large scale integrated circuit, biology chip technology, nano technology, position of optical components, fiber connection, microelectronic products manufacture, precision and ultra precision machining, precision operation, precision measurement, biomedical engineering, material surface atomic structure analysis, ect. The development of micro displacement positioning technology is closely related to the progress of the defense industry and the national economy, and its technical indicators are the important signs of the high-tech development of various countries. With the rapid development of microelectronic technology, communication technology and ultra precision machining technology, the requirement becomes higher and higher in precision positioning technology. Some application fields requires that its system owns nanoscale resolution, sub micron or even nanometer level repeat positioning accuracy. Therefore, the micro displacement work platform is required to have these technical requirements, such as large displacement, high accuracy, small size and rapid response etc.Firstly, the importance and significance of the subject are described, and the composition of the micro displacement platform and the research status of the domestic and foreign are introduced, and the research content is presented.Secondly, the work principle and characteristics of piezoelectric material and piezoelectric stack are introduced. The finite element method are discussed. On this basis, the output displacement characteristics of piezoelectric stack are analyzed using finite element analysis software ANSYS. The results show that the output displacement of the piezoelectric stack is linear with the applied voltage under some conditions, and when the length of the piezoelectric stack is unchanged, the piezoelectric ceramic piece is thinner, the output displacement is greater.Thirdly, a displacement amplification mechanism is proposed for the characteristics of the small displacement output of the piezoelectric stack, which is based on the principle of the orthogonal triangular magnification. The working principle of amplification mechanism is introduced. The statics analysis method and energy method are used to calculate the work characteristics of displacement amplification mechanism. The ANSYS finite element software is used to calculate the mechanism’s static state and dynamic state feature. Theoretical analysis and practical tests show that the displacement amplification actuator not only can provide large output displacement and output torque, but also have good static and dynamic characteristics. It can be used as micro displacement platform drives.Fourthly, a large torque micro displacement platform is manufactured. Its location characteristic is obtained through theoretical analysis. The displacement, stress, vibration modes and dynamic respond of the platform are analyzed by finite element method. At the same time, the characteristics of this platform are tested by the way of laser testing. It can be seen that the micro displacement platform can get the stable and fast large output displacement through the static and dynamic test. Because the hysteresis and creep properties of piezoelectric material which are shown in characteristic test, a series of control method is provided to achieve fast and accurate position. The platform’s drive system based on Lab VIEW is designed and made out. The location drive method includes open-loop control, increment type PID closed-loop control and neural network PID closed loop which based on MATLAB. These location control methods are designed and analyzed.Finally, The experimental results show that compared with open loop control, the PID closed-loop control not only don’t effect the micro displacement platform’s response speed, and overcomes the piezoelectric material’s hysteresis and creep effects. Therefore the platform’s positioning precision and accuracy can be guaranteed. PID parameter self-setting based on BP neural network, compared with artificial parameter setting, can avoid the complicated and not timely, and can improve the practicality and position’s accuracy and speed. It is worth further developing and application in practice.The micro displacement platform is composed of the piezoelectric stack, triangle amplified’s displacement actuator, hinge etc. its size is 115mm× 115mm ×20mm; maximum displacement is 140 μ m×140 μ m; repeat precision is±0.02 u m; maximum load is 250N。 Theoretical analysis, prototype production and experimental test are used to introduce the micro displacement platform form various angles and scales. The closed-loop drive system is applied in this platform, it makes up these shortcoming of piezoelectric material’s hysteresis and creep. Finally the micro displacement platform is made out which owns high precision, large displacement and quickly response. |
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