Compact and Lightweight Linear Actuator for Handheld Medical Robotic Devices

Handheld robotic devices for exact positioning and machining tasks in the medical field are expected to be ergonomic. They should be both, lightweight and compact. Size and weight of handheld robots are mainly determined by their actu-ators. The aim of the study was to design and build an application-specific linear synchronous motor (LSM) and to characterize its electromagnetic, mechanical and thermal behaviour. A LSM with overall weight of 0.55 kg, a total length of 207 mm and a stroke of 96 mm was realized. The applied magnet-to-coil-ratio of 4/3 improved the utilization of the electromagnetic field. The electrodynamic force measurement revealed a force constant between 7.8 N/A and 8.1 N/A. Considering the thermal design of the LSM a continuous force of 8.75 N and a peak performance of 16.75 N for 10 s was derived. In dynamic measurements accelerations of up to 15 m/s(exp 2) and a velocity limit of 0.225 m/s was observed. The LSM was successfully position controlled and monitored in dynamic, force and thermal experiments. It was developed with a double parallel long stator design resulting in less length and a low weight making it suitable for hand held robotic devices.