Synthesiology - English edition

−273 Synthesiology English edition Vol.1 No.4 (2009) the arm of a robot, smooth movement can be achieved by increasing the number of scale tick marks written on the 360o /cycle and thereby increasing the resolution. To control the position of the arm accurately, deviation between the angle information provided by the rotary encoder and the ideal angle position is evaluated, and accurate angle position control can be achieved by correcting the angle deviation. To accomplish this, it is necessary to measure the factor that cause the deviation of angle information obtained from the rotary encoder as shown in Fig. 1 and Fig. 2. However, although encoder manufacturers possessed technology to measure deviation in several tens of graduated scale, they did not have the technology to measure several thousands to ten thousands of scale, and therefore could not comprehensively and quantitatively evaluate various factors of angle deviation. As result, “accuracy” described in the product catalog of the encoder was not calibration curve that represents the angle deviation as shown in Fig. 3, but instead, it was safety tolerance where angle deviation is set as 0 and upper and lower lines are used to block off the large area of safety tolerance. Therefore, the “accuracy” as defined by the manufacturer was “black box” value where which angle deviation factors are included in what values were unknown.