Motion Control of a Direct Drive Permanent-Magnet Motor Selective Compliant Articulated Robot for Assembly

A direct drive selective compliant articulated robot for assembly (SCARA) was developed to allow back-drivability. However, because of its load-to-motor inertia ratio, it exhibits resonance problems. To mitigate this issue, we measured the SCARA’s resonance frequency and amplitude in various postures and implemented the real-time filter based on it. The filter reduced the resonance amplitude and eliminated the vibration. As the coupling between the two axes leads to significant current shocks and velocity overshoot, we employed the dynamics feedforward (DFF) function obtained by decoupling the SCARA’s dynamics. The DFF successfully eliminated the velocity overshoot, reducing the motor current overshoot. These enhancements significantly improve the performance of the SCARA system.