Encoderless robot motion control using vision sensor and back electromotive force

This paper focuses on a possibility of application of a method to simplification of robotic arm systems by removal joint encoders. The method which has been proposed achieves precise control of robotic arms using visual feedback with camera calibration errors. In this paper, the method is improved for an encoderless robotic arm system to ease several difficulties to use encoders. Encoders are fundamental components of most robotic arm systems to control joint angles precisely. However, encoders sometimes make some difficulties of wiring, structure and maintenance. The enhanced method for encoderless robotic arm systems is able to overcome these difficulties. Moreover, this method is also useful for robotic systems which have encoders since the method is able to be activated as a fail-safe system of robots with encoders just in case encoders are broken down. This new approach acquires information on joint angles from not encoders but estimation using back electromotive force. The information on joint angles includes some errors. The method, however, realizes precise manipulation. It is finally shown that this method allows errors caused by not only from camera calibrations but also joint angles.