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The focus of this study is a moment compensation control algorithm driven by a direct current servo motor. Zero moment robot teaching is achieved with a joint moment compensation algorithm. The moment equilibrium equation is derived based on moment compensation. The current signal detected by a Hall effect sensor is multiplied by a torque constant to estimate the torque value of the robot joint. The compensation current is obtained through parameter identification to overcome gravitational and friction torques. The two variables of speed and position are separately controlled, allowing the compensation current of Coulomb friction and viscous friction force to be separated from the compensation current of friction torque. This study presents the system research, design, and development of a high-precision position control theory of a robot zero moment teaching control method. A collaborative robot is used as the test and verification platform to confirm the feasibility and effectiveness of the proposed theoretical method and implementation technology.

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This paper present a method for detecting collision occurs in the robot manipulator and reacting according to collision direction. An experiment was conducted to read the joints speed during collision of the UR3 robot at static position, where the joints speeds are supposed to be zero. The experiment showed that when collision occurs within the manipulator there is oscillatory speed produced in joints, which is suggested to be duo to the stiffness of the harmonic drive. The harmonic drive is a flexible transmission generates stiffness behavior, as a spring, between the motor and the link. The collision is determined from the oscillatory speed produced in robot joints at static position. The method successfully identified the collision impact at joints, and reacted according to the collision direction. The experimental setup and the results are presented in this paper.