Design and implementation of a new torque controller via FPGA for 6-DOF articulated robots

This study aims to design a force/torque position-based proportional-integral-derivative (PID) controller based on kinematics of 6-degree-of-freedom (DOF) HIWIN RA605 articulated robot and a field-programmable gate array (FPGA) implementation in high-speed. This novel force/torque controller is appropriate for collaborating with humans or grinding, winding tasks, or any jobs that require force/torque accuracy, and it can even reduce the harm caused by robot-human or robot-robot collisions. A digital algorithm for 6-DOF controller is developed using Verilog HDL and validated with an FPGA to implement several tasks (e.g., encoder counters, digital filter, analog generator, PID controller, and communication) to drive alternating current (AC) servo motors. Digital filter is a crucial algorithm implemented inside the FPGA to minimize the error from encoder signals. A proposed force/torque controller works with an analog voltage rather than a pulse-width modulation as some prior controllers accomplished. The process time by FPGA is 160 ns. The total time response of the control system including hardware response is 82 mu s. In this study, the position error at the end effector is around 0.19 mm.