Cooperative Manipulator Control Based on IgH Ethercat Master

Abstract

Cooperative manipulators are widely used in the scenarios where the human and the robot work closely to perform tasks such as assembling, medical care and surgical operation. More advanced control laws such as model-based force regulation with space constraint are increasingly needed to endow the robot with safe interaction capability in medical scenarios. These advanced control laws require complete control of the robot manipulator with minimal control latency. Unfortunately, commercial manipulators do not provide users with low-level access to the controller. Therefore, we developed a six-axis robotic manipulator for cooperative tasks with human. A control system based on EtherCAT with high real-time performance and satisfied motion control effect is proposed in this paper. The open source IgH EtherCAT is employed as the master and each drive of the axis motors serves as the slave node. A Linux + Xenomai dual-kernel system is configured to ensure the real-time performance. A motion control system based on IgH EtherCAT is built. On this basis, the free drag control in task space based on admittance control is achieved. The experimental results show that the communication time was less than $4 \times 10 ^{4}$ nanosecond (ns), and the cycle jitter was below $20 \mu \mathrm{s}$. The maximum average joint velocity error during the task space free drag was $6.85 \times 10 ^{-4}$ rad/s.