Real-time quintic Hermite interpolation for robot trajectory execution

• Main Author: Morten Lind
• Format: Article
• Language: English
• Published: PeerJ Inc. 2020-11-01
• Series: PeerJ Computer Science
• Subjects: Interpolation; Robotics; Real-time; Python; Joint control; Trajectory
• Online Access: https://peerj.com/articles/cs-304.pdf

This paper presents a real-time joint trajectory interpolation system for the purpose of frequency scaling the low cycle time of a robot controller, allowing a Python application to real-time control the robot at a moderate cycle time. Interpolation is based on quintic Hermite piece-wise splines. The splines are calculated in real-time, in a piecewise manner between the high-level, long cycle time trajectory points, while sampling of these splines at an appropriate, shorter cycle time for the real-time requirement of the lower-level system. The principle is usable in general, and the specific implementation presented is for control of the Panda robot from Franka Emika. Tracking delay analysis is presented based on a cosine trajectory. A simple test application has been implemented, demonstrating real-time feeding of a pre-calculated trajectory for cutting with a knife. Estimated forces on the robot wrist are recorded during cutting and presented in the paper.