Improvement of position measurement for 6R robot using magnetic encoder AS5045

Recording the variation of joint angles as a feedback to the control unit is frequent in articulated arms. In this paper, magnetic sensor AS5045, which is a contactless encoder, is employed to measure joint angles of 6R robot andthe performance of that is examined. The sensor has a low volume, two digital outputs and provides a high resolution measurement for users; furthermore its zero position is adjustable. Installation and use of thismeasurement system on 6R robot has been expressed by using output signals of sensor AS5045 in the digital control board of 6R and equipped with ARM processor LPC1768. First, a sample of digital board is used for controlling aDC motor in both speed and position, in order to investigate specifications of AS5045’s digital and analogue outputs. Simulation of 6R robot in point-topointmotion has been performed with MATLAB software using a proportional derivative (PD) controller. Then, experiment with the same condition and gains via a PD controller has been designed and implementedon the digital control board. The feedback system has been also checked in a circular path to show its advantages in trajectory tracking. The comparison of simulation results with experiments shows improvement: less error andbetter performance of 6R robot. This new setup omitted the noise of previous analogue feedback system since its digital outputs provides a precise measurement.

Keywords:

Magnetic sensors , 6R robot , joint angle , PD controller