Yoshihide Hakozaki

Measurement of force acting on surgical instrument for force-feedback to master robot console

Abstract For fine surgical operation by slave robot, master robot needs the information of the contact force loaded on the tip of the surgical instrument. One of major problems in sensing the force is frictional disturbance between the trocar and the instrument. One of authors proposed a new method named overcoat method where the whole instrument is supported by force sensors. This paper tried to construct a force measuring system with the trocar type of the overcoat method. It discussed about the compensations of gravity and acceleration force of the instrument in relation to the pose and motion of the instrument. The tried system measured the tip-loaded force in absolute accuracy about 0.3 N and in sensitivity about 0.05 N.

Development of a drive mechanism for a robot with a cyclo gear reducer, and its application to a semi-continuous variable transmission gear

Rapid prototyping is a technology using a CAD/CAM, and a molding machine, which manufactures a prototype model rapidly. Since it can make products with complex shapes of three dimensions, the cost and time for development is reduced. It is convenient in the production of a wide range of prototypes, particularly in a products development. The purpose of our research was to manufacture an effective motor reducer to develop a robot with high mobility. To achieve this, it was necessary both to reduce the weight of the robot using a 3D processing machine and a 3D molding machine, and to develop a robot with high rigidity. In this paper, a cyclo gear reducer was developed using the rapid prototyping. The cyclo gear reducer has a deceleration ratio of engagement that is two and three times higher than the usual involute gears. Also, the transmission efficiency of the cyclo gear reducer is usually designed to be high, which means that it is usually difficult to achieve precision in gear teeth, such as those of the spur wheel and involute gear of the planetary gear, using resin material. Since the curved shape of the teeth used in an epitrochoid gear are not sharp, the gear and gear box can be made using a simple 3D processing machine even if the material has low rigidity, as in the case of plastics. Furthermore, we are planning to develop the cyclo gear reducer that can semi-continuously change the deceleration ratio by installing the mechanism where the slide moves along the direction of the rotation axis in the epitrochoid gear, as one of the applications of the cyclo gear reducer.

Contact force measurement of instruments for force-feedback on a surgical robot: acceleration force cancellations based on acceleration sensor readings

For delicate operations conducted using surgical robot systems, surgeons need to receive information regarding the contact forces on the tips of surgical instruments. For the detection of this contact force, one of the authors previously proposed a new method, called the overcoat method, in which the instrument is supported by sensors positioned on the overcoat pipe. This method requires cancellation of the acceleration forces of the instrument/holder attached to the overcoat sensor. In the present report, the authors attempt to use acceleration sensors to obtain the acceleration forces of the instrument/holder. The new cancellation method provides a force-detection accuracy of approximately 0.05-0.1 N for a dynamic response range of up to approximately 20 Hz, compared to approximately 1 Hz, which was achieved by using acceleration forces based on the theoretical robot motion.