Kinematic model calibration of a collaborative redundant robot using a closed kinematic chain

Abstract

In this paper, we propose a novel approach for the kinematic calibration of collaborative redundat robots, focusing on improving their precision using a cost-effective and efficient method. We exploit the redundancy of the closed-loop kinematic chain by utilizing a spherical joint, enabling precise definition of the robot end-effector position while maintaining free joint motion in the null space. Leveraging the availability of joint torque sensors in most collaborative robots, we employ a kinesthetic approach to obtain constrained joint motion for calibration. An optimization approach is utilized to determine the optimal kinematic parameters based on measured joint positions and a constrained end-effector position defined by the spherical joint. The effectiveness of the proposed method is demonstrated and validated on the Franka Emika Panda robot, a 7-DoF robot. Results indicate a significant enhancement in absolute accuracy, with comparable performance to more expensive sensor systems such as optical measurement systems. Our approach offers a practical and cost-effective solution for improving the precision of collaborative robots.

Adaptive Dynamic Boundary Sliding Mode Control for Robotic Manipulators under Varying Disturbances

“…As shown in Figure 9, the validation of the ADBSMC is demonstrated using a 7-DOF Franka-Emika-Panda robot equipped with high-precision torque sensors. Control of the robot is achieved through the Franka Control Interface (FCI), and real-time control values are transmitted at a frequency of 1 kHz [28]. The FCI provides a framework that enables the robot to receive real-time feedback from external sensors.…”