Optical Rotary Encoder Research Articles

ＹＡＧレーザマーカによる金属表面直接描画光エンコーダ

A new patterning method of an optical rotary encoder gratings is proposed and tested for higher precision and higher rotational speed more than 30000 min-1, which marks the grating patterns directly on the metallic shaft of an air spindle by using YAG laser marker. It is pointed that the second harmonic generated YAG laser wave is more effective for this application rather than the fundamental wave. The experimental patterning system applies a precise speed control system using a flywheel and the PLL (Phase Locked Loop) speed control system with the unique error compensation. The validity of this method is proved from a microscopic examination of the patterned gratings and the regeneration of the encoder signal with a standard optical detector.

超小型減速機・エンコーダを内蔵したサーボアクチュエータの開発

ブラシレスDCモータと遊星歯車減速機および光ファイバエンコーダを一体化して, 外径3mm, 5mmのサーボアクチュエータを開発した.トルクと回転数の間, トルクと電流の間の出力特性には線形関係があった.さらに, これらのアクチュエータを用いてマイクロスカラロボットを開発し, 本アクチュエータはマイクロマシンなどの駆動源として有用であることを確認した.アクチュエータのさらなる高トルク化を図るために, モータの高出力化と減速機の高減速比が課題である.今後はこれらの課題を解決し, 発電プラントの配管内のような狭い場所を点検する移動ロボットの駆動源として応用範囲を広げていく.

Closed-Loop Posture Control of Parallel Biwheel Vehicle Driven with Stepping Motor.

A simple motion control scheme of a dynamical system driven with a stepping motor is proposed. The scheme is examined through posture control of a parallel biwheel vehicle that consists of an inverted pendulum supported by two coaxial parallel wheels. Posture of the vehicle is regulated by state feedback where a step rate of the stepping motor instead of a motor torque is used as control input to the system. The proposed scheme can produce steady vehicle motion around an unstable equilibrium position by numerical simulation. The simulated initial responses reveal that there is an appropriate range of peak static torque values of the stepping motor. A large peak static torque results in the increase of vibrational amplitude of the vehicle around the unstable equilibrium position, and a small torque causes step failure due to overload before appearance of unrecoverable tumbling motion. In experiments, the posture of the vehicle can be regulated within an inclination angle of ±5×10-3 rad under the proposed scheme with a 5-phase 500 step/rev stepping motor. An optical rotary encoder of 1.75×10-3 rad/pulse resolution is used as the inclination angular sensor.

Speed Control of a Hybrid Transducer-type Ultrasonic Motor.

A hybrid transducer-type ultrasonic motor serves a high controllability, since the driving force can be controlled independently of the friction controlling component. The torsional vibration velocity has a direct effect on the speed, while the longitudinal vibration controls the traction transmission through friction. We can change the speed smoothly, if we vary the torsional vibration velocity, with the longitudinal vibration being maintained at the optimum value.This paper presents an experimental study of a speed control system for a hybrid transducer-type ultrasonic motor. First, we utilize an optical rotary encoder to measure the speed of the rotor, and it is feedbacked to the excitation magnitude of the torsional vibration. Stability and transient responses of the speed are improved. Second, we point out that the speed has a linear relation to the current of the torsional port. Then, by monitoring the current, a feedback system can be built without any auxiliary encoders.

A Motor-driven Ventricular Assist Device Controlled with an Optical Encoder System

An electric motor-driven ventricular assist device has been developed for long-term use inside the body. The system is composed of a pusher-plate-type blood pump and an actuator consisting of an electrical motor and a ball screw. Cyclic change of the direction of motor rotation makes a back-and-forth axial movement of the ball screw shaft. The shaft, which is detached from the pump diaphragm, pushes the diaphragm via a pusher plate to eject blood during systole; blood is sucked by the diaphragm resilience during diastole. Using the output signals from a newly designed, incremental-type, miniature optical rotary encoder mounted inside the actuator, the input voltage of the motor is optimally controlled referring to the phase difference between the current position of the moving rotor and the electrical reference signal of the rotation generated by a microprocessor-based controller. In vitro performance tests indicated that the system fulfills required specifications. The maximum efficiency was 11%, which was about twice as high as that obtained with the previous open-loop prototype system. In the air, the surface temperature of the actuator elevated to 20 degrees C above the room temperature. An acute in vivo test showed its feasibility as a left ventricular assist device. Analysis of the energy loss in each component of the system indicated that redesign and precise assembly of the mechanical parts could increase the system efficiency.

The measurement of the piston velocity of a hydraulic actuator

The use of three types of transducers to measure the velocity of the piston shaft of a hydraulic actuator is investigated. The types of transducers are linear magnetic scale, magnetostrictive, and optical rotary encoder. Different methods of calculating the piston velocity from the position information are proposed, and the results of the test measurement are presented. >