Development of orientation sensing technology for micro motor in ingestible medical capsule

Abstract

Capsule endoscopy increasingly used in medical field for diagnosis of gastrointestinal tract disease, such as gastric ulcers and colon cancers, in order to alleviate the suffering of patients, has yet not achieved complete and clear view of the digestive tract due to constraint from limited mobility of embedded camera. Therefore, a micro motor is proposed to overcome this limitation. In the previous project, a micro Ultra Sonic Motor with piezo-ceramics as driving component designed to serve as the actuating basement for the camera has a mobility to reach desired views in a hemispherical scope. Because of the configuration of the ultrasonic motor, which uses a wrist-joint like spherical rotor constrained in cavity, instantaneous and final orientation of the rotor is not known especially with friction as the primary driving force. A positioning sensing system, hence, is required to tackle with the unknown orientation in order to realize remote fine control and full automation. Investigations and research on the positioning sensing system for micro-scale ultrasonic motor by using piezo-ceramics suitable for ingestible medical capsule is conducted in this study as the second stage of the project collaborated with Data Storage Institute. Kinematics of the spherical rotor’s rotation with 3-Degree of Freedom is analysed and prototype simulating the rotor’s rotation is developed and manufactured based on the mathematical model. A positioning feedback sensing system by using dual orthogonal laser sensors of Avago LaserStream series measuring rotation with respect to principle axes is proposed together with the sensing algorithm based on instantaneous incremental rotation step.