Motion Control and External Force Estimation of a Pneumatically Driven Multi-DOF Robotic Forceps

Dongbo Zhou,Daisuke Haraguchi,Kotaro Tadano

doi:10.3390/app10113679

Abstract

Robotic forceps with a rigid-link joint mechanism is orthodox for current robotic-assisted surgery systems. However, external force estimation without force sensors during operations is difficult for such electrically driven forceps. This work introduces a pneumatically driven multi-DOF (DOF: degree of freedom) forceps using a rigid-link mechanism with less interference of the wire drive between joints and realizes external force estimation by utilizing high back-drivability of pneumatic cylinders. We developed a position controller with dynamic compensation of the mechanical friction, in which the rotational angles of the three movable joints of the forceps are independently controlled. Moreover, we designed an external force observer in the position controller by applying the disturbance observer scheme. The results of the performance evaluation experiments are as follows. First, in the joint position control experiments, smooth and stable controllability is confirmed for sinusoidal reference inputs with the mean absolute errors of less than 2°. The resolution of the joint position control is approximately 1° for the response of step increasing reference inputs, which is acceptable for laparoscopic surgery. Second, the external force observer can correctly estimate the translational and the grasping forces with less than 20% errors of the maximum output forces. The practical sensitivities of the external force estimation are better than 0.5 N for translational forces and 0.2 N for grasping forces. The achieved performance of the developed forceps can be applicable for interactive force control in some particular surgical tasks such as suturing, ligation, organ traction and exclusion.

Highlights

IntroductionRobotic-assisted minimally invasive surgery has been significantly developed owing to its many benefits, including the reduction of the surgeon’s tremble and increase in the operational accuracy [1,2]
Robotic-assisted minimally invasive surgery has been significantly developed owing to its many benefits, including the reduction of the surgeon’s tremble and increase in the operational accuracy [1,2].As the end effector of a robotic-assisted surgery system, the robotic forceps are inserted into the patient’s abdominal cavity through a trocar
Regarding the performance of external force estimation, the maximum errors between the estimated and measured forces in all directions were less than 20% of the maximum output forces

Summary

Introduction

Robotic-assisted minimally invasive surgery has been significantly developed owing to its many benefits, including the reduction of the surgeon’s tremble and increase in the operational accuracy [1,2]. As the end effector of a robotic-assisted surgery system, the robotic forceps are inserted into the patient’s abdominal cavity through a trocar. The size of the working part is firmly restricted. Several groups used the rigid-link mechanism to meet such requirements, wherein multiple rigid joint links independently rotate in a direction that is orthometric with the others, and the actuators are located at the proximal end outside the patient’s body. Song et al developed a forceps with four. Andreas et al proposed a snakelike instrument that consists of seven rigid joints for minimally invasive surgery [4]

Methods

Discussion

Conclusion