Safety Control for UR-Type Robotic Manipulators via High-Order Control Barrier Functions and Analytical Inverse Kinematics

In robotics field, safety is an extensively researched subject. This article proposes an approach, which is based on high-order control barrier functions (HOCBFs) and computed torque control (CTC), for UR-type manipulators to guarantee safety while minimizing input changes. Since modeling accuracy influences the final performance, a novel analytic solution of inverse kinematics is proposed in this article with complete singularity analysis. Using CTC to construct a nominal controller, a quadratic program (QP) is formed by combining it with designed HOCBF constraints. Solving the QP, trajectory tracking can be achieved under particular safety constraints. The proposed approach has been validated on the UR3 robot in simulation and experiment, taking an obstacle avoidance task as safety constraints.