The Performance of a Novel Latching-Type Electromagnetic Actuator for Single-Port Laparoscopic Surgery

Abstract

This paper reports on the performance evaluation of a novel latching-type electromagnetic actuator which is designed to be embedded at selected joints along single-port laparoscopic surgical instruments (SLS). The aim of this actuator is to allow these instruments to become articulated with a push of a button in order to provide the optimum angulation required during SLS operations. This new actuator is comprised of electromagnetic coil elements, soft magnetic frames and a permanent magnet. Unlike conventional electromagnetic actuators, latching-type electromagnetic actuators could maintain their positions at either end of the actuation stroke without any power application requirement. In the current design, magnetic attraction forces initiated between the permanent magnet and the magnetic frame are utilised to lock the position of the actuator whilst a certain angulation position of the actuator is achieved as a result of the magnetic repulsion forces established between the permanent magnet and the coil elements. The performance of the new actuator in terms of the output force, maximum angulation and patient's safety, was evaluated experimentally and the results were found to compare well with those acquired numerically using finite element methods. This actuator was seen to exhibit sufficient actuation forces and hence, it was capable of providing adaptable angulation characteristics for SLS tools. Finally, thermal evaluation of the actuator's operation was conducted, which was found to be within safety limits specified by clinicians.

Development of a Novel Latching-Type Electromagnetic Actuator for Applications in Minimally Invasive Surgery

“…It is worth mentioning that none of the currently available actuation technologies allow for the construction of a modular and back-drivable articulated system with a high force output and a small footprint capability, which is suitable for SLS applications [15,26,27]. In addition, the new actuator, which was thermally proven to be safe [28], weighs about 25 g and therefore, it is expected that any gravity effects would almost have no impact on the position control of the actuator. Furthermore, this actuator is capable of generating torques larger than 45 mNm, which is based on a 9 N driving force in association with a 5 mm offset that was allowed between the hinges of the side sliding link and the top swivelling component.…”

A Novel Hydraulic Actuation System Utilizing Magnetorheological Fluids for Single-Port Laparoscopic Surgery Applications

“…These forces, in association with the 5 mm offset, which was allowed between the rack and pinion hinge of the top swivelling component, enabled the developed smart actuation system to resist input torques of up to 500 mNm. This torque level appears to be higher than those produced by recently reported actuating systems for SLS applications [9], and therefore the developed smart actuation system should be capable of maintaining the posture of SLS instruments against input loads that are expected under such surgical protocols. This was achieved when the developed smart actuation system, with its miniaturised MR actuator and its low excitation current feed, was capable of producing angulations of about 90 • .…”

“…These issues have made it difficult for current systems to find their successful deployment in most SLS theatres. Consequently, novel, compact and lightweight actuation systems with adequate mechanical simplicity and robustness must be developed in order to revolutionise the function of current SLS tools [9].…”