For prevent infections; surgical instruments on medical robot should be sterilized after invasive operations. Recently, steam sterilization is a standard method applied to sterilize surgical instruments. Thus any sensors on instruments would be destroyed during sterile process. Nevertheless, surgeon needs to be acknowledged for the grasping force to prevent unexpected damage of sensitive structures such as arteries. To give the surgeon the force feedback, this study suggests the control method of grasping force of surgical robotic instruments without measuring grasping force.
In order to estimate the grasping force on instruments, we will use the measured value which is the driving motor which is operates instrument joint current and develop the grasping force measure systems using pressure sensors. The relation between the motor current and grasping force could be analyzed by the grasping force measure systems and measured motor current. Through this relationship, it is possible to control grasping force without force sensor. When the Jaws on the instruments are moving forward any direction with grasping something such as needle, the one jaw’s moving direction and forcing direction are same. But another jaw’s moving direction and forcing direction are definitely opposite direction. So this study suggests the following control method: there are two jaws. The one jaw which has same two directions is controlled desired trajectory like cubic spline. Another jaw is controlled for maintain the grasping force between two jaws by force estimate system.