Comparative Assessment of Several Nutation Motor Types

A new type of pneumatic stepping motor, named a nutation motor, has been developed. By using a simple mechanism in a compact body, this motor can generate high torque. The nutation motor consists of three small linear pneumatic actuators and a gear-reduction mechanism that transforms their motion into rotation of the output shaft. Driving each pneumatic actuator sequentially with pneumatic digital signals results in nutation of the input bevel gear, which causes the output shaft to rotate. In this paper, the structure, working principle, and theoretical characteristics of a pneumatic nutation motor are presented. The design and fabrication of five prototype models and the results of experimental evaluations are also reported in detail. The prototype motors range in size from 10 to 50 mm in diameter and from 11.5 to 49 mm in length. It was found that the torque/volume ratios of the pneumatic nutation motors were about 2-29 times larger than those of a typical conventional electromagnetic geared motor.