Direct Teaching Of Industrial Robots Based On Current Feedback

Teaching box is widely used in the industrial robot system.However,with the rapid changes and growing complexity of industrial demand,teaching box cannot meet the requirement of massive teaching works.The existing direct teaching scheme can be divided into two categories.The first is the costly force/torque sensor based method.The second is torque control based scheme,which is not able to apply in the robot not supporting the torque command.This dissertation focus on sensorless direct teaching technology based on velocity command.The key to realizing direct teaching is compensating the gravity and friction of robots by the torque of the motor.This dissertation proposes the velocity command and current feedback based scheme for directing teaching against the method of complete dynamic torque compensation with the problem of complex model identification,the large noise of acceleration and not being able to apply in the robot not supporting torque command.The main idea is as follows.To compensate gravity and friction of robots by velocity command,velocity servo is modeled.To improve the performance of direct teaching,the gain of external to rque signal is introduced.Furthermore,the external torque is estimated by the current feedback based method and the velocity command and current feedback based direct teaching scheme is generated without a force/torque sensor.Besides,lowpass filter is adopted to smooth the planning velocity and the parameter t uning method is given.Direct teaching is performed on the industrial 6-DOF robot,and a force/torque sensor is used to measure the external force and torque.The result shows that the external force spent during direct teaching is about 8N and the maximum is not larger than 20 N.Finally,to solve the problem of trajectory dithering,the median average filter is utilized.Feature points of the trajectory are extracted using the Douglas-Peucker algorithm.The final trajectory is generated through spline and cubic interpolation.The result shows that real trajectory is consistent with the planning one,which implies the validity of the teaching and playback scheme.