Page 28 - Flexible Robotics in Medicine

10 Chapter 1

electromagnetic markers. Besides, registration of the position and configuration of the robot to
the preoperative 3D organ model is essential for surgeons during an operation. Shi et al. [56]
summarized the measurement methods of continuum surgical robots’ position and
configuration. Up to date, there are mainly two kinds of methods to track the snake robot inside
the human body, one is curve-based shape reconstruction, and the other is extended Kalman
filter (EKF)-based shape estimation combining the kinematics. For the first type, Song et al.
[57 59] proposed a tip tracking and shape sensing method for tendon-driven snake robot
without relying on a mechanical model, in which the robot shape was reconstructed by a three-
order Bezier curve fitting of the data collected through electromagnetic markers on the robot’s
critical segments and tip. For the filtering method, Tully et al. [60 62] and Srivatsan et al. [63]
proposed EKF-based prediction of the pose, position, and configuration of a “follow-the-leader”
style snake surgical robot, with the information of kinematic model and one 5-DOF
electromagnetic tracking sensor. In the subsequent work, Tully and Choset [64] built a
constrained Kalman filtering algorithm to localize the robot and registration it to the predefined
organ surface model following the requirements of contact detection in the surgery.

Force sensing appears to be more challenging because force sensors need power, communication,
and occupy specific spaces if they are fixed on the snake robot’s segments and tips. There are
mainly two ways on the force sensing of snake-like continuum surgical robots, one is to measure
the forces through force sensors fixed on the robot such as fiber Bragg grating (FBG) sensor, and
the other is a deduction of for robot’s tip force through the static and kinematic model. For force
sensingwithsensors,Shi et al. [56] have summarized the usage of FBG sensor and fiber optical
sensor on force sensing and shape estimation of continuum surgical robots. Separated from
sensor-based force sensing, the deduction of the robot tip force is called intrinsic force sensing,
which can be divided into categories of deflection-based force sensing and actuation-based force
sensing. For deflection-based force sensing, Rucker and Webster [65] built a force estimation
algorithm based on EKF using the robot’s statics and kinematics and the measurements of the
uncertain poses. For actuation-based force sensing, Xu and Simaan [66] proposed an intrinsic
force sensing method, in which the tip force was solved based on singular value decomposition)
of Jacobian mapping from configuration space to twist space. Black et al. [67] proposed a force
sensing method based on the generalized Cosserat-rod-based kinetostatic model of a parallel
continuum robot. Yuan et al. [68] proposed a force sensing method using pose and cable tension
of the robot based on the kinematic-static model. For a pneumatic driven flexible distal joint,
Haraguchi et al. [31] proposed sensing of the three-axis external force on a snake-like forceps tip
by estimation with a translational deduction based on the dynamic and inverse kinematic models.

1.4.2 Motion planning

Mechanical designs of snake-like surgical robots determine their workspace, which is one
of the criteria of the robot’s dexterity. A snake surgical robot’s workspace can be derived