Master–slave manipulator for laparoscopic surgery using a 6-axis vertical articulated robot

Laparoscopic surgery is a minimally invasive surgery that accelerates postoperative recovery, but it can only be performed by surgeons with advanced surgical skills. One of the main difficulties in laparoscopic surgery is restriction of free motion of the forceps because of limited degrees of freedom by the trocar. Recently, many master–slave manipulators with a remote center-of-motion mechanism have been used in laparoscopic surgery to solve this problem. The master–slave manipulator for laparoscopic surgery using a 6-axis vertical articulated robot has some advantages as a scalable and versatile system. However, to achieve smooth insertion and removal motion of the forceps from the trocar, the problem of restriction of motion by the trocar must be addressed. This paper describes a master–slave manipulator system for laparoscopic surgery using a 6-axis vertical articulated robot with a slave arm containing forceps. A manipulating mode of the slave arm, consisting of four basic motion modes and three control modes, is proposed in order to perform smooth operations when the motion of the trocar is restricted. The three control modes include a non-trocar mode, a trocar mode, and a transitional mode between the two modes in order to ensure smooth insertion and removal motions of the forceps. Furthermore, the transitional mode consists of a posture adjustment motion and insertion-removal motions. The posture adjustment motion before an insertion motion of the forceps under the transitional mode is achieved by the motions of only the 4th axis and 5th axis of the slave arm. The posture adjustment motion and insertion motion under the transitional mode and the master–slave motion under the trocar mode are shown through evaluations of the master–slave manipulator system, including a 6-axis vertical articulated robot, in order to verify the effectiveness of the proposed methods.