State feedback adaptive control of a direct drive motor

Since direct drive motors do not have reduction gears, the variation of the load and the disturbance torque directly influence parameter changes in motor dynamics. In order to solve this problem, the paper presents a state feedback adaptive control method for position control of a direct drive motor. The proposed control scheme does not require an accurate mathematical model of the system. The controller consists of a feedforward signal from the desired trajectory based on the inverse system model, feedback from the actual trajectory, and an auxiliary input. The feedforward terms are adjusted by an adaptation law that eliminated the steady-state position errors. In order to compensate for incorrect motor parameters, feedback terms are employed. The auxiliary input is introduced to improve the tracking performance. The proposed controller is applied to position control of a direct drive motor with payload and parameter uncertainty, and the effectiveness is verified by simulation results.