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

Abstract

Single-port laparoscopic surgery (SLS), which utilises one major incision, has become increasingly popular in the healthcare sector in recent years. However, this technique suffers from several problems particularly the inability of current SLS instruments to provide the optimum angulation that is required during SLS operations. In this paper, the development of a novel latching-type electromagnetic actuator is reported, which is aimed to enhance the function of SLS instruments. This new actuator is designed to be embedded at selected joints along SLS instruments to enable the surgeon to transform them from their straight and slender shape to an articulated posture. The developed electromagnetic actuator is comprised of electromagnetic coil elements, a solid magnetic shell, and a permanent magnet used to enhance the magnetic field interaction along the force generation path and also to provide the latching effect. In this investigation, electromagnetic finite element analyses were conducted to design and optimise the actuator’s electromagnetic circuit. In addition, the performance of the new actuator was numerically and experimentally determined when output magnetic forces and torques in excess of 9 N and 45 mNm, respectively together with an angulation of 30° were achieved under a short pulse of current supply to the magnetic circuit of the actuator.

A Hybrid Electromagnetic and Tendon-Driven Actuator for Minimally Invasive Surgery

“…Because the stiffness of each actuator could be set individually, only one pair of tendons was required to control the bending of all the flexible joints, which significantly reduces the overall space requirement for the tendon-driven structure. The proposed electromagnetic structure was previously developed and optimized by the author for MIS applications [14]. However, unlike the previous design that could only provide an angulation of 30 • , the hybrid actuator could offer an angulation from −90 • to 90 • with a step angle of 22.5 • (the spur gear structure has eight teeth in 180 • ) for each joint, while the achievable positions of the joint could be further increased with the intensification on the number of gear teeth.…”

“…To visualize the functional workspace of the developed hybrid electromagnetic and tendon-driven actuator whilst compare it with the conventional MIS instruments and previous design [14], MATLAB software (MathWorks, Inc. Natick, Massachusetts, USA) was utilized to produce forward kinematics of these systems in this study.…”

“…In particular, when θ 0 was fixed to be 0 • , the surgical devices are allowed to be inserted only as straight tools through the trocar ports, without subjecting them to any tilting about the entrance of the insertion, which is ideal for the MIS with less flexibility such as natural orifice transluminal endoscopic surgery (NOTES) and single-incision laparoscopic surgery (SILS). Figure 4a shows the novel developed actuator that provides various angulations (−90 • to 90 • ), which was compared to the previous design [14] that could only offer a single angulation of 30 • . Since the permanent magnet no longer needed to provide the actuation movements for the articulation, the structure of the actuators was slightly changed, where the slot and side link on the soft magnetic shell was dismissed.…”

“…Accordingly, numerical and experimental approaches were utilized to evaluate the performance of the developed hybrid actuator. Figure 4a shows the novel developed actuator that provides various angulations (−90° to 90°), which was compared to the previous design [14] that could only offer a single angulation of 30. Since the permanent magnet no longer needed to provide the actuation movements for the articulation, the structure of the actuators was slightly changed, where the slot and side link on the soft magnetic shell was dismissed.…”

“…Furthermore, the shape of the proposed instruments will be locked after the adjustment, which enable the device to be manipulated by a single hand of the surgeon. The performance of the developed actuator was summarized in Table 4, which is benchmarked against other actuators (developed for SILS) already reported in the literature [12,14,24]. Even though the proposed hybrid electromagnetic and tendon-driven actuator could enhance the dexterity of the MIS instrument to a great extent, it has few drawbacks as well.…”