Design and Some Experimental Results of the U-Type Permanent Magnet Three-Phase Linear Motor Based Position Control System with the Backstepping Technique Based Disturbance Observer

Author(s):  
C. X. Tuyen ◽  
N. T. Huong
Author(s):  
Yohichi Nakao ◽  
Naoya Asaoka

A precise spindle is essential to achieve precision machining, such as diamond turning. A fluid driven spindle supported by hydrostatic bearings was thus designed and tested. A feature of the spindle is that several flow channels are designed in its rotor so that driving torque can be generated by supplying pressurized flow into the channels. Rotational speed of the spindle can be controlled by the flow rate. In addition, the rotational direction of the spindle can be controlled by switching supply ports. Thus angular position control of the spindle is achieved by designing appropriate feedback controller. In the present paper, mathematical model of the spindle was thus derived in order for designing an angular position control system. Then spindle characteristics calculated by the mathematical model were compared with experimental results. Furthermore, the angular position control system that has a disturbance observer in its feedback loop was designed based on the mathematical model. The performance of the designed control system was experimentally investigated through the step response. Experimental results verified that the designed controller minimizes the steady state error of angular position of the spindle. Consequently, the steady state error was comparable with the resolution of the rotary encoder, 0.018 degree. In particular, the experimental results indicated that the disturbance observer effectively reduced the influence of various load torque on the angular position of the spindle.


Author(s):  
Y Nakao ◽  
M Ishikawa

This paper describes the design of a rotational speed-control system and an angular position-control system for a fluid-driven bi-directional motor. The fluid-driven bi-directional motor has a driving principle similar to that of the fluid-driven spindle, which is designed for use in ultra-precision machine tools. The fluid-driven bi-directional motor was designed so that it is driven by low viscosity oil flow power. In this paper, the rotational speed controller for the motor is first discussed. In order to reduce the influence of external load torque on the rotational speed, a conventional disturbance observer is combined with the rotational speed-control system. The angular position-control system, which possesses the rotational speed feedback loop with the disturbance observer in the angular position feedback loop, is then discussed. The designed rotational speed and angular position-control systems are conventional I—P control and proportional control systems, respectively. The performance of the designed rotational speed-control system and the angular position-control system is studied via simulations and experiments. The performance of the designed control system is tested by the step response method as well as by the frequency response method, respectively. The simulation and experimental results show that the rotational speed and the angular position of the motor can be controlled by the rotational speed controller and angular position controller, respectively. In addition, the influence of the external load torque acting on the motor is successfully compensated for by means of the disturbance observer. The experimental result shows that the designed angular position-control system suppresses the steady-state positioning error to less than 0.02°, even if external constant load torque acts on the motor.


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