Virtual tool for bilaterally controlled forceps robot-for minimally invasive surgery

Background: Bilateral control enables an operator to be placed away from the working environment. A slave manipulator usually works at a remote site or in a hazardous environment while the master operator senses the environment through the slave manipulator. Bilateral control can be used in surgeries. Usually doctors are very sensitive to the tactile sensation they feel through medical tools. If bilateral control is used in a surgery, ideally the doctor should perceive the sensation of both the body tissue and the reaction force from the specialized tool. Many surgical instruments are essentially similar at the tool tip while showing some structural differences at the gripping end. Therefore, it is advantageous for an expensive tool to be replaced by a virtual tool together with a simple tool. With the virtual tool, the surgeon should be able to perceive the feeling of the actual tool together with the reaction force coming from the body tissue; this may also reduce the time taken for a tool change during the surgery. Methods: In this study, above ideas were implemented in a bilaterally controlled forceps robot and experiments were carried out to test the applicability of the concept. Bilateral control is used as the method of tactile feedback. Disturbance observer is used for robust control. Reaction force observer is used in place of a force sensor. Virtual model is used in place of the special tool properties. Results: A virtual spring acting at the end of the forceps, was implemented to a bilateral control system, so that the operator at the master side could perceive the feeling of the spring together with reaction forces from the surgical environment. Operator could feel the vivid sensation of the environment through the master manipulator. Conclusions: The virtual model adds a load to the system. The master and slave responses are slightly different, but the result is good enough for the application. This novel approach could be used in many master-slave applications.