Page 210 - Flexible Robotics in Medicine

Compliant bending tubular mechanisms with variable groove patterns 197

8.2.1 Robotic system

With more than 20 years of development, the usage of robots in surgery has continuously been
on the rise as new and improved technology enable operator to carry out complex procedures
with much more precision, flexibility, and control as compared to conventional techniques [5].
Miniaturization, feedback sensing, visualization, and precise manipulation of the robot during
surgery would not only improve the success rate of the surgery but also reduce the patients’
recovery process. The Da Vinci Surgical System [6],Zeus system [7], and the Medrobotic
FLEX system [8] are the representative recent robotic systems that are currently being used
during an operation. These systems for MIS give the operator a real-time visual image of the
operation area. Operators retain visual feedback from the controllers during operation.

8.2.2 Joint types for bending

There are many different types of configuration of joints [9] that can give rise to the bending
action of the manipulator. Each joint has its advantages and disadvantages, and we introduce
and briefly discuss each of the joints that can be used in the following segment.
• Rolling joint: This joint consists of two interfacing segments aligned perpendicularly
to each other that share a moving point of contact. Cables are employed to hold the
individual segments together. This type of joint has two degrees of freedom (DOF) in
three dimensions.
• Sliding joint: Sliding joints are commonly used in MIS instruments, rotating in a single
plane.
• Bending joint: This bending joint, unlike the previous two types, is formed from a
single unit. The geometry of the piece, such as wall thickness, plays a part in the
bending motion: too thick and bending force would be high, too thin, and material
rupture occurs. Cut-out patterns on the tube further facilitate bending motion.

8.2.3 Related works of manipulators

The manipulator is a robotic arm that can be controlled. It is designed to be able to move
into position and firmly lock its position in place. Having more DOFs and being able to
miniaturize would be advantageous. In the following sections, we will be going through the
representative manipulators that are being researched or being employed for MIS operation.

8.2.3.1 Snake-like slave-side robots

Multiple disks that are in parallel configuration relate to each other via actuators (shape
memory alloy), and bending motion is controlled by actuators made of Ni-Ti wire [10].
Warming up the wire to its transition temperature would contract the wire to its programmed
shape. This contraction results in the bending of the entire configuration.