Robot-assisted surgery has advanced dramatically over the past decade in almost every surgical sub-specialty. Robot-assisted surgery is usually performed using surgical robot systems that involve a master-slave configuration in which the “master” is a controller device that the surgeon manipulates to control a robotic arm. Such systems improve the dexterity and precision of surgeons by filtering out hand tremors and scaling their hand motions into smaller movements. They also reduce the risk of common surgical complications such as surgical site infection.

Gripping part of the master manipulator with the combined grip handle.

Robot-assisted surgery comes with its own disadvantages, especially for the person performing the surgery. Surgeons sometimes feel physical discomfort during surgery, with finger fatigue being common. This discomfort is associated with the way in which they grip the master controller. Two types of grips are usually used to control surgical robots: the “pinch grip” and “power grip.” The pinch grip has been used in conventional surgeries for centuries; it involves using the thumb, middle, and index fingers to achieve high-precision movements. On the other hand, the power grip involves grabbing a handle with the entire hand and is more suitable for forceful work and large movements.

Because the pinch grip puts tension on certain muscles of the hand and fingers, it is more likely to cause fatigue. And although the power grip does not seem to cause such discomfort, it offers less precise control. Therefore, there is a tradeoff between the discomfort caused by the pinch grip and the lack of fine control of the power grip.

Researchers have designed a master controller that can be adjusted to employ pinch, power, or combined gripping. The system was tested through a pointing experiment in which 15 participants had to control a robotic arm to bring the tip of a needle into target holes in the least amount of time without touching obstacles. Various conditions were tested for each gripping type such as the use of arm and palm rests, use of handle, gripping type, and pinch grip motion. The combined grip yielded better performance in the pointing experiment on various fronts including number of failures (touching an obstacle), time required, and overall length of the movements performed to reach the targets. Many participants also preferred the combined gripping method over the other two, owing to the ease and comfort in using this method.

This new master controller design exhibits intuitiveness, comfort, precision, and stability. In addition to enabling precise operation, a comfortable manipulating method could potentially benefit both the patient and the surgeon. Future work is needed to analyze other variables involved in robotic arm manipulation.

For more information, contact Associate Professor Kotaro Tadano, Institute of Innovative Research, Tokyo Institute of Technology, at This email address is being protected from spambots. You need JavaScript enabled to view it.; +81-45-924-5032.


Motion Design Magazine

This article first appeared in the April, 2020 issue of Motion Design Magazine.

Read more articles from this issue here.

Read more articles from the archives here.