The current trend of the contemporary medicine is less invasiveness and local therapy. One of the most common procedures employed in modern clinical practice involve percutaneous insertion of needles and catheters for biopsy and drug delivery. Percutaneous procedures involving needle insertions include vaccinations, blood/ fluid sampling, regional anesthesia, tissue biopsy, catheter insertion, cryogenic ablation, electrolytic ablation, brachytherapy, neurosurgery, deep brain stimulation, minimally invasive surgeries and more.

These problems can be solved by introducing thin and flexible needles. Moreover, it is known that thinner needles cause less pain to the patient. On the other hand, flexible needle navigation deep inside the tissue is very complicated. The system has non-minimum phase behavior and is not intuitive to control. Path planning for flexible needle insertion and obstacles avoidance inside the body tissue is a challenging problem in mechanics and robotics. Creating an automated system that can plan and perform thin, flexible needle insertion will minimize misplacements, reduce risks, and reduce patient suffering.

Flexible needle insertion into viscoelastic tissue is formulated by a linear beam supported by virtual springs. Using this simplified model, the forward and inverse kinematics of the needle is solved analytically, providing a way for simulation and path planning in real-time. Using the inverse kinematics, the required needle basis trajectory can be computed for any desired needle tip path.

Localization and navigation of an endoscope within a patient body is usually based on anatomical landmarks recognized by the surgeon. This technique might be more complicated, however, when a long a flexible endoscope is used. The proposed investigation presents a system that provides an image with a stabilized orientation using a miniature magnetic sensor located at the tip of a flexible endoscope. As a result, the surgeon perception of the anatomical features is enhanced enabling accurate localization of the endoscope. The system was tested in-vitro and experimental results are presented.

This investigation proposes an efficient registration method for robotic-assisted surgery. Current registration techniques often need implantation of artificial fiducial markers or digitizing devices such as optic or magnetic sensors or laser scanners, which complicate the registration procedure.
The registration process described here uses a surface matching technique, and thus does not require any marker implant. The following three ideas simplify the registration process. First, the robot itself is used as a digitizer eliminating the need for an extra localizer. Second, bone modeling is based on the multi-resolution technique for adaptive registration. Third, an algorithm to determine the minimal number and location of sampled points needed for registration was developed, thus easing the intra-operatively sampling process.
The proposed method was applied to Total Knee Arthroplasty (TKA) procedure, and special care was taken in adapting the method to the surgical application in hand.

Methods:
Since we plan to use a robot in the surgical procedures, it can also be used as a digitizer, thus considerably reducing the potential inaccuracies in reference frame registration. The registration is then performed directly between the bone and the robot, which in turn guides the surgical tools. For speeding up the computation we introduce the hierarchical multi-resolution approach and use a level of detail data model.
To ensure the required accuracy of 1deg rotation and 1mm translation, we explore the subject of optimal number of sampling points and their location. The search for the best sampling points is viewed from the grasping theory point of view [3]. Mathematically, it is possible to view the problem of choosing optimal sampling points for registration as that of grasping the bone with a multi-fingered hand. The contacts between the fingertips and the grasped object are modeled as frictionless point contacts. Each contact is modeled as a virtual linear spring directed normal to the surface passing through the point of contact. In order to determine the optimal set of sampling points for each set of points, a worst case transformation is calculated. That is, we look for the bone motion which is minimally detected by the sensor. Among these motions, we choose the set of contact points that are maximally dislocated by the minimal motion. This configuration of the grasp gives the best stiffness properties; hence, the points of contact are the best candidates for sampling during registration.

This manipulator consists of three identical kinematic chains connecting the base and the moving platform. Each chain contains a lower link rotating around a pivot perpendicular to the base platform and offset-placed from the center of the base. At the other end of the lower link, a prismatic actuator is attached by a spherical joint. The upper end of the prismatic actuator is connected to the moving platform by a revolute joint. The axes of the revolute joints constitute an equilateral triangle in the plane of the moving platform

The design process included singularity analysis of the architecture. This yielded a robot with a minimal number of singularities inside its workspace. One of the features of this robot is its capabilities to perform 90 degrees rotation about the vertical axis and to align one of the linear actuators with the plane of the moving platform without having parallel singularity, in which, the moving platform loses constraint (gains uncontrollable degrees of freedom). 

 

Kinematic and dynamic analysis of a parallel robot consisting of three planarly-actuated links, is presented in this paper. Coordinated motion of three planar motors, connected to three fixed-length links, produces a six-degrees-of-freedom motion of an output link. Its extremely simple design along with much larger work volume than the commonly used parallel robots make this high performance-to-simplicity ratio robot very attractive. Experimental model verifies the unique combination of large work volume and high accuracy of this robot.