Micro torque measurements for a prototype turbine

Many applications for microengineered devices can be envisaged for actuators capable of doing work or transferring power. Millimetre order turbines are considered in this study for the development of torque and the possibilities for the delivery of work. A prototype microturbine, with overall thickness of less than a millimetre, was studied for its torque capabilities. The initial prototype was realized using precision mechanics although implementation of the turbine is planned using microengineering techniques. A viscous braking method was developed to measure the shaft torque of the turbine, demonstrating shaft coupling and the possibilities for power transfer. In order to validate the viscous braking method for torque measurement, a mechanical friction brake (dynamometer) was developed to compare the measurements obtained for a miniature electric motor of known characteristics. The results from this series of calibration experiments were then used to evaluate the performance of a microturbine prototype. The dynamometer torque measurements were found to closely agree with the manufacture's stated stall torque for the miniature motor of 1.8*10-4 N m. The viscous brake torque measurements were found to underestimate the motor torque by around 20% with slight variation related to the angular velocity of the shaft. Shaft torque measurements for the prototype microturbine were possible using the viscous brake but not the dynamometer. It was felt that 10-5 N m represented the lower limit for the dynamometer torque measurement while the viscous brake could address torques down to 10-8 N m. The fluid brake produced measurements of torque in the range of 10-7 N m for the microturbine. At this level only an order of magnitude accuracy is claimed because of some uncertainties with the fluid model used for the viscous brake torque calculation. The shaft torque range for the viscous brake was from 10-4 N m down to 10-8 N m; this might be extended by optimizing the fluid model.

[1]  F. T. Moore,et al.  Viscosity and its measurement , 1962 .

[2]  S. Jeanneret,et al.  Micro-torque sensor based on differential force measurement , 1994, Proceedings IEEE Micro Electro Mechanical Systems An Investigation of Micro Structures, Sensors, Actuators, Machines and Robotic Systems.

[3]  Robert L. Mullen,et al.  Electric and fluid field analysis of side-drive micromotors , 1992 .

[4]  Yutaka Nonomura,et al.  Real time measurement of instantaneous torque by magnetostrictive sensor , 1991, TRANSDUCERS '91: 1991 International Conference on Solid-State Sensors and Actuators. Digest of Technical Papers.

[5]  C. Phillips,et al.  Feasibility of using micromachines for cataract surgery , 1990, IEEE Proceedings on Micro Electro Mechanical Systems, An Investigation of Micro Structures, Sensors, Actuators, Machines and Robots..

[6]  K. J. Gabriel,et al.  In situ friction and wear measurements in integrated polysilicon mechanisms , 1990 .

[7]  J. Schweitz,et al.  Truly three dimensional structures microfabricated by laser chemical processing , 1991, TRANSDUCERS '91: 1991 International Conference on Solid-State Sensors and Actuators. Digest of Technical Papers.

[8]  Stephen C. Jacobsen,et al.  A design overview of an eccentric-motion electrostatic microactuator (the wobble motor) , 1989 .

[9]  T. Christenson,et al.  Metal micromechanisms via deep X-ray lithography, electroplating and assembly , 1992 .

[10]  R. Clavel,et al.  Miniature gear reduction unit driven by a silicon electrostatic wobble motor , 1994, Proceedings IEEE Micro Electro Mechanical Systems An Investigation of Micro Structures, Sensors, Actuators, Machines and Robotic Systems.

[11]  V. A. Repin,et al.  Research and design studies on medical microturbines , 1983 .

[12]  W. Ehrfeld,et al.  Application of the LIGA technique for the development of microactuators based on electromagnetic principles , 1992 .

[13]  G. Arthur,et al.  Deep UV optics for excimer laser systems , 1990 .