| According to the operating characteristics of ultrasonic motors (USMs), a new position-velocity feedback control strategy is proposed and implemented in a three-joint robot directly driven by USMs. Robust parameter design has been used to obtain an optimal and robust set of PID controller gains. The index of average position error of joints has been reduced to 87.5%. Results show that, the proposed control strategy can achieve the best performance of the robot and robust parameter design is effective and convenient to the USMs. |