Study on bending forceps manipulator with electric-cautery function for laparoscopic surgery

摘要

We have developed a wire driven Multi-DOF forceps manipulator, which has two DOF of bending on the tip of forceps. The purpose of this study is to realize position feedback control of the forceps realizing the smooth motion of the forceps. We also investigated cautery system installed on forceps manipulators that can occlude large vessels such as bile duct securely. The basic data for design of electrodes were corrected. In the previous system, large friction between rigid bodies at rolling parts led to poor dynamic characteristics [1]. To overcome this, we used a new bending mechanism where force's point of action was positioned closer to the center of bending motion. In addition, a pre-tension mechanism with springs was introduced. We also studied a bending angle measurement system consisting of a light emitting diode (LED) and a phototransistor (PT) placed on both ends of bending parts of forceps. By measuring change in the electric current in PT, we could estimate the bending of forceps. We evaluated the characteristic of the bending mechanism and the measurement system. As for electric cautery system, we investigated condition for secure occlusion of bile duct by electric cautery by changing parameters as follows: method of holding bile duct, patterns of electrode plates, applied voltage and cauterizing time. Porcine bile ducts were used as specimens. To measure strength of occlusion, pressure was applied by injecting air into the occluded bile duct and measured the maximum pressure tolerated before its burst.