External Torque Observer Based On Generalized Momentum And Collaborative Robots Collision Detection

Cooperative robots and operators share a working space.Operator safety is the primary consideration and mandatory constraint in the field of human-robot collaboration.Effective detection of human-robot collision is one of the important links to ensure the safety of operators.Factors such as the collaborative robots have multiple degrees of freedom,collisions may occur at any joint of the robot;the collision time may be short or long-lasting;the intensity of the collision force constitute complex human-robot collision situations.In this paper,the UR5 six degree of freedom collaborative robot is used as a research reference.Based on the robot dynamics and generalized momentum,a collision detection algorithm for constructing an external torque observer is designed.The main work and achievements are:Based on the DH convention,the link coordinate system of is established,and the positive kinematics equation of the robot is established.On the basis of robot kinematics,based on the Euler-Lagrange method,the dynamics equation of the robot is established.The joint torque is obtained by establishing a virtual prototype in ADAMS,and compared with the joint torque calculated by MATLAB,the correctness of the robot dynamics equation is verified.This paper proposes a collision detection algorithm based on robot dynamics and generalized momentum.The collision force is added to the ADAMS virtual prototype to simulate human-robot collision.The robot kinematics information is used as the input of the collision detection algorithm,the results show that the external torque changes during the collision,and the algorithm can effectively detect the collision.The transposition of the Jacobian matrix converts the collision force acting on the robot into the calculated external torque of each joint,which can guide the adjustment of the observer.Based on ADAMS and MATLAB design co-simulation,the results show that for a variety of complex human-robot collision situations summarized by ISO/TS15066:2016(E): 1)different joints,extending from joint 5 to joint 4;2)transient collision0.1 second and quasi-static collision 1 second;3)collision forces of different intensity of 300 N and 150 N,the collision detection algorithm can effectively perform collision detection,and has a certain universality.The algorithm designed in this paper can provide a reference for solving the collision detection problems in complex scenes such as different joints that collide during human-machine collision,the length of the collision time,and the intensity of the collision force.Compared with the traditional method,the algorithm in this paper can save cost without external sensors,and has a certain practical application significance.