Autocompensation of torque ripple of direct drive motor by torque observer

Since a direct drive motor (DDM) does not require a reduction gear, the drive system can be made simple, and therefore it is used in high-precision robot and machine tool applications. However, without reduction gear, a disturbance torque is directly reflected to the motor shaft, and a torque ripple generated by the motor is directly transmitted to the load, causing poor speed control characteristics. An improved torque control system for DDM with a permanent magnet rotor, equipped with a torque observer implemented by digital signal software, is proposed. The speed fluctuation can be fully removed with a torque feedforward loop