An estimation method of grasping force for laparoscope surgical robot based on the model of a cable-pulley system

Considering the urgent need of force feedback and control for laparoscope surgical robot, it is important to predict and estimate the grasping force of end-effector during the surgical procedure. There are many problems to design and install the force sensors in the narrow space of surgical robot, such as insuitable dimensions, electromagnetic interference and biocompatibility problems. Therefore, it is difficult to measure the grasping force of the end-effector. This paper presents an estimation method of grasping force for laparoscope surgical robot based on the model of cable-pulley system. The model considers the tension transmission characteristics of cable-pulley system, couple characteristic of end-effecter and friction loss characteristic caused by adjacent pulleys. Three experiments validate the couple relationship, tension transmission characteristics and estimation of grasping force, respectively. The results of experiments show that, the pitch and yaw angles of graspers are inversely proportional to their corresponding radius of pulley; the ratio of incoming and outgoing tension depends on the parameters of cable-pulley system; the estimation of grasping force is compared with real force measured by force sensor to verify the validity.