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

Abstract

Single-port laparoscopic surgery (SLS), which utilizes one major incision, can deliver favorable cosmetic outcomes with fewer patient hospitalization stays and less postoperative pain. However, current SLS instruments, which are rigid and slender, have been suffering from several drawbacks, including their inability to provide the optimum articulation required to complete certain SLS tasks. This paper reports on the development of a lightweight smart hydraulic actuation system that is proposed to be embedded at selected joints along current SLS instruments, in order to enhance their adaptability with a higher level of stiffness and degrees-of-freedom. The developed smart actuation system utilizes both conventional hydraulic and magnetorheological (MR) fluid actuation technologies. Electromagnetic finite element analyses were conducted to design the electromagnetic circuit of the smart actuator. A prototype of the developed actuation system was manufactured, and its performance was assessed using a dedicated experimental arrangement, which was found to agree well with the results obtained using a Bingham plastic theoretical model. Finally, the present design of the developed smart actuation system permits an angulation of about 90° and a maximum force output in excess of 100 N, generated under a magnetic excitation of about 1.2 Tesla, which should be sufficient to resist torques of up to 500 mNm.

Keywords: magnetic-responsive materials; magnetorheological fluids; single-port laparoscopic surgery (SLS); smart hydraulic actuator; smart material actuator; smart materials.

Figure 1

Schematic diagram of the proposed smart actuation system with its three MR actuators, single hydraulic actuator and single fluid delivery tube.

Figure 2

MR fluid actuator with its rack and pinion mechanism shown in its straight (left) and bent positions (right).

Figure 3

Half-section views of the MR actuator showing contour plots of the magnetic flux lines (a) and the magnetic flux density distribution (b) in the actuator body (current density = 16,000 kA/m²).

Figure 4

Magnetic flux density variation along a median path inside the MR fluid gap between the piston and the shell of the actuator (current density = 16,000 kA/m²).

Figure 5

Magnetic flux density versus magnetic field intensity for Lord MRF241-ES fluid.

Figure 6

Schematic diagram of the experimental setup for testing the smart hydraulic actuation system.

Figure 7

SMC CDJ2D10-30-B linear hydraulic actuator [34] shown next to a 1p coin.

Figure 8

Variation of average magnetic field density simulated along the axial pole length inside the fluid gap of the MR actuator as a function of actuator’s coil-energising current.

Figure 9

Resistance force of the smart hydraulic actuation system with deactivated MR actuator versus input speed.

Figure 10

Total force of the smart hydraulic actuation system as a function of the magnetic flux density for a driving speed of 0.5 mm/s.