1993 Fiscal Year Final Research Report Summary
Study of Lonlinear Control of Pecision Positioning Systems
| Project/Area Number |
04452158
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
機械力学・制御工学
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| Research Institution | Tokyo Metoropolitan University |
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Principal Investigator |
WATANABE Atsushi Tokyo Metoropolitan Unive., Technology, Professor, 工学部, 教授 (70167104)
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| Co-Investigator(Kenkyū-buntansha) |
MORONUKI Nobuyuki Tokyo Metoropolitan Unive., Technology, Assc. Professor, 工学部, 助教授 (90166463)
KAWATA Siichi Tokyo Metoropolitan Unive., Technology, Assc. Professor, 工学部, 助教授 (20152960)
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| Project Period (FY) |
1992 – 1993
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| Keywords | high precision positioning / servo control / variable structure / sliding mode / PID control / state feedback control / control design / optical linear encoder |
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| Research Abstract |
Precision of a positioning unit is heavily influenced by coulomb friction and backlash which exist in the mechanism of the positioning system. Dimension variation and deformation due to force or heat also cause inaccuracy of positioning. This study is to investigate control methods which overcome these obstructing factors commonly found in positioning units and make posible an ultra-high precision positioning. The outline of the study results is given below.
1. Preparatory Study
Several schemes of control were tested on an existing linear positioning system which consists of a ball screw and positioning table driven by a servo-motor. Among the tested control schemes the sliding mode control in the variable structure ontol system was found most promising. An ordinary PID feedback control combined with a pulse mainipulating input was also found practical in its simplicity and good performance.
2. Assemblage of a High Precision Positioning Unit
A new positioning system was assembled in the same construction as the existing system with a much higher precision. The position of the positioning table was measured by an optical linear encoder of 10nm resolution. The reading of the encoder was directly fed back to the control loop.
3. Comparison of Control Schemes
Mathematical models of the third order, the fourth order and the fifth order were constructed. For each model a state feedback control system and a sliding mode control system were designed and tested for performance by both simulations and experiments. In either control scheme, for the third order model neglected higher order modes caused high frequency vibration in responses. The fifth order model had a difficulty in determining good parameter values in identification process. The sliding mode control designed with the fourth order model gave the best results.
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