A compact planar motion system with flexure bearings and magnetic position sensors

Pao Yue-kong Library Electronic Theses Database

A compact planar motion system with flexure bearings and magnetic position sensors


Author: Luk, Man Yu Andrew
Title: A compact planar motion system with flexure bearings and magnetic position sensors
Degree: M.Sc.
Year: 2013
Subject: Integrated circuits -- Design and construction
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Mechanical Engineering
Pages: xvi, 134 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2597950
URI: http://theses.lib.polyu.edu.hk/handle/200/6937
Abstract: In semiconductor industry, integrated circuit (IC) probing is one of the most important processes to evaluate the performance and ensure the quality of electronic devices. In order to achieve high throughput and reliability, an innovative planar motion platform with flexural bearings and magnetic encoders is developed. The planar motion platform included two pairs of flexural bearings which enable precise X-Y positioning in a compact size. The 3μm repeatability and 20μm position accuracy can be achieved with the proposed mechanical system. Moreover, a new Voice Coil Motor (VCM), which provides two directional forces simultaneously in one coil, and a magnetic encoder, which provides low cost solution for position feedback, are used in the proposed system. In order to improve the system performance with a stable and rapid system response, a PID controller is implemented for the prototype system. Swept-sine test is conducted on the experimental system to identify the actual system behaviour for the PID controller and filter design. However, the system performance is degraded due to the predictable non-linearity of the motor force constant, and the system parameters change because of the assembly variation. By the reason, a Model-Reference Adaptive System (MRAS) is also proposed to further improve the system dynamics and the steady state response. Numerical simulation of the proposed MRAS is also performed to evaluate the system performance. The superior performance of MRAS is found in the simulation which outperforms the conventional PID controller on handling the non-linearity, the system parameter variation and the disturbance injection.

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