A soft gear motor

Abstract

Flexible, active catheter and micro-manipulator devices can provide doctors with extra control during intra-body procedures, improving the quality of in vivo information and micro-surgery. There is currently a lack of an actuation mechanism to make these devices a reality. A soft, low complexity, artificial muscle motor that is capable of multiple degrees of freedom actuation is a potential driver for these devices and was investigated in this thesis. In the soft gear motor, a central gear deforms to grip and transmit force to a shaft. A series of experiments were performed to obtain information on its speed/torque curve and translational displacement. The prototype motor was 200mm in diameter and the membrane mass weighted 1.02g. It had a specific power of 0.2 W/kg, specific torque was 0.6 Nm/kg. It had a holding torque of 2.07mNm and a radial translational displacement of 1mm. The motor's rotational characteristic was like that of a stepper motor with an in-built "rachet" that prevented back rotation. An implicit quasi-static finite element model of the motor with contact was created in ABAQUS. To demonstrate the utility of the model, two case studies were discussed: an in-depth investigation of the rotational mechanism of the motor, and a suggestion on how an additional out of plane translational degree of freedom can be incorporated. The model can be used in the future for rapid prototyping analysis of new motor designs. The soft gear motor shows promise as a manipulator. The next step in the development of flexible, active catheter and micro-manipulator would be the miniaturisation of the motor. The ABAQUS model can also be improved by moving to an explicit formulation.