Torque accumulation for hybrid transducer ultrasonic motors using a coaxial driveshaft connection mechanism

This paper describes the results of combining several hybrid transducer ultrasonic motors together in parallel on a single central shaft in order to obtain a large output torque. The authors propose a practical connection mechanism using the hollow cylindrical motors. The rotor of each motor is connected together via a rod which penetrates through the center of each motor, and thus, the rod collects the output torque from each of the motors; the accumulated torque appears at the end of the rod. In a theoretical study, an equivalent electrical circuit model is introduced to represent the torque accumulation mechanics and it indicates that the maximum torque of the combined system is equal to the summation of the maximum torque obtained from each motor. Two combinations of the system composed of two motors are tested in an experimental study. The measured maximum torque of each system is equal to the summation of the maximum torque obtained from each motor as shown in the theoretical investigation.