Principles of torque measurement for rotating microactuators

Different micromotors and other rotating microsystems like gearboxes with dimensions of a few millimeters have been developed during the last years. Applications of such micromotors can be found in sensors and actuators for example in medical equipment. These components offer the possibility of extreme miniaturization of mechanical systems with driven rotating parts. The characterization of rotating microsystems is necessary during the state of development as well as for quality control in production. The minimum requirement for the characterization of a motor is the measurement of torque and of rotational speed The measurement of rotational speed is a relative simple task, even for miniaturized systems, but the measurement of torque is much more complicated. Most of the well-known methods and sensors for measurement of torque are not suitable for micromotors. A sensor unit based on a spring-element using optoelectronic methods for measuring the small deformation of the spring has been developed to cover the requirements for torque measurement of rotating microsystems. Within the European project HAFAM (Handling and Assembly of Functionally Adapted Microcomponents) a complete testing stage for characterizing rotating microsystems using this sensor has been developed. The objective of this micro torque testing stage is to provide a flexible and modular means for assessing the performance and the quality of both active and passive microsystems, e.g. micromotors or micro ball bearings.