Research On Joint Force Compliance Control Of Service Robot

Human-robot interaction is an important development direction of robot technology,which mainly deals with the interaction and cooperation between human and robot.The research on the technology of robot collision detection and the joint force compliance control improves the man-machine integration ability of service robot.Currently,the common way to perceive accidental collisions of robotic arms is to add external sensors,and the use of such sensors significantly increases the hardware cost.In order to solve this problem,this paper takes Cruzr service robot manipulator designed by UBTECH as the research object,analyzes the collision detection method with current as the parameter,and studies the joint force compliance control of service robot.The major work contains following content.According to the mechanical structure of Cruzr robot arm,the link coordinate system was established,the forward kinematics equation calculation algorithm was designed,and the accuracy of the algorithm was verified by Matlab Robotics Toolbox.The closed solution method was used to solve the inverse kinematics.The dynamic modeling of Cruzr robot arm was completed by Newton-Euler method.The method of detecting collision by current was analyzed and the dynamic model was established.In order to simplify dynamic parameter identification,a simple and effective collision detection method based on current change rate was proposed.After that,collision detection algorithm based on current change rate was further improved to prevent misjudgment of collision caused by current mutation when the velocity of the robot arm was changed.To determine the threshold of collision detection,a dynamic threshold detection method based on different motor speeds is proposed.Aiming at the realization of compliant drag,the force/position hybrid control and impedance control were compared and analyzed.Based on this,a kind of the use of joint current change speed to achieve smooth control method was proposed.To solve the problem of how to determine the direction of collision force,two solutions are proposed,one is to use potentiometer to assist in judging the direction of collision force,and the other is to determine the direction of collision force by anticipation collision force direction and then determined by next periodic changing current.The force perception algorithm and the compliance control algorithm are experimentally verified by the joint collision detection experiment and the compliance drag experiment.The experimental results show that when the collision occurs,the mechanical arm can quickly detect the collision and make a response.On Cruzr robot,external collision force greater than 1N can be detected and the response time is less than 30 ms.The service robot can be dragged by hand at low speed,achieving the desired goal.