Force propagation models in laparoscopic tools and trainers

Most of the tools that are used in performing manipulation tasks in laparoscopic surgery are graspers and needle drivers. Although the operation of such basic tools is rather simple, their combination with remote access to the surgical site and an indirect field of view makes the usage of such mechanisms challenging. This means that surgeons have to undergo a series of training sessions in order to gain proper hand/eye coordination. In addition, due to the structure of these mechanisms, the sense of touch has been reduced to a minimum. One challenge of research and development has been to design a force-reflective grasper that can reflect the sense of touch back into the handle. In addition, considerable efforts are being focused on developing a virtual laparoscopic trainer where the sense of touch in manipulating virtual tissues and organs can be reflected back to the hand of the surgeon through the proper design of haptic interfaces. This paper presents force propagation models which can be used in the modelling, design and interpretation of the force sensing system and reflecting devices. The proposed models agree with the experimental observation previously published in the literature for describing the relationships between the magnitude of the grasping force and the applied force at the handle.