Review of snake robots in constrained environments

Recently, flexible robotic systems are developed to enhance minimally invasive interventions on internal organs located in confined areas of human body. These surgical devices are designed to navigate anatomical pathways via single-port access, such as natural orifices or minimal incisions and intraluminal interventions. With improved precision, spatial flexibility and dexterity, the robotic technology can enhance surgery such that minimally invasive flexible access would become a faster, safer, and more convenient method for intra-body interventions without multiple or wide incisions. However, a lot of works are still required for global acceptance of existing flexible robotic surgical platforms. This review provides extended insights on the design details of two types of flexible robotic systems used for endoscopic and endovascular procedures. As of today, several prototypes of both platforms have been proposed; however, their global acceptability and applicability remains very low. To address these, we present an extensive review on design constraints and control methods which are vital for safer, faster, and better operation of the flexible robotic systems in minimally invasive surgery (MIS). Finally, research trends of flexible robotic systems and their clinical application status in MIS are discussed along with some of the technical and technological challenges hindering their prominence. 

A Review on Flexible Robotic Systems for Minimally Invasive Surgery

This article presents the development of a new medical robot system comprising a spherical remote center motion (RCM) mechanism with modular design and two mechanical decoupling methods for Minimally Invasive Surgery (MIS). We achieved excellent comprehensive performance indices through a novel multi-objective optimization model comprising four optimization objective functions, three constrained conditions and two optimization variables. In order to enhance the manipulability, remove the coupling between motors, and reduce the control difficulty, two new decoupling mechanism means were proposed to remove coupling motion between the wrist and pincers, coupling motion between the translational joint of mobile platform and four interface disks of surgical instrument as a results of rear drive motor, respectively. The control system architecture is designed to include intuitive motion control, incremental motion control, and proportional motion control. Master-slave attitude registration and surgical instrument replacement strategies improve the master-slave control efficiency. We tested the spherical RCM mechanism performance indices and developed two mechanical decoupling methods and a master-slave control algorithm. Our experimental test results validated that fixing point accuracy, the coupling motions, the positioning and repeated positioning accuracy of the MIS robot, and master-slave control algorithm meet the requirements of MIS. Successful animal experiments confirmed effectiveness of the novel MIS robot system.

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Development of a New Medical Robot System for Minimally Invasive Surgery

In Robotic-Assisted Minimally Invasive Surgery a long and thin instrument attached to the robotic arm enters the human body through a tiny incision. To ensure that no injury occurs when the surgeon is manipulating the instrument, the incision point must be a remote center of motion (RCM) for the instrument. For this purpose, a novel target admittance model is designed in the joint space for hands-on procedures that can be applied in all commercially available general-purpose manipulators with six or more degrees of freedom. It is proved that the joint reference trajectories generated by the proposed target admittance model under the exertion of a human force are stable and satisfy the RCM constraint. The measurements of the human force and the robot’s forward kinematic model are only required. Its use spans all hands-on surgical procedures. The proposed model can be easily extended to achieve additional objectives. Simulation results validate the theoretical findings and experimental results utilizing a KUKA LWR4+ demonstrate that trocar displacements are less than 1mm.

A Controller to Impose a RCM for Hands-on Robotic-Assisted Minimally Invasive Surgery

The invention discloses an instrument for a robot-assisted micro-invasive surgery. The instrument comprises a driving device, a connecting guide pipe and a terminal executing device which are sequentially connected; the driving device comprises a base, three driving shafts are rotationally arranged on the base through a bearing, and each driving shaft is fixedly sleeved with a screw roller and a cohesion block; the terminal executing device comprises a clamp seat and an opening and closing clamp, wherein the clamp seat is fixed at the front end of the connecting guide pipe, the opening and closing clamp consists of a left opening and closing clamp body and a right opening and closing clamp body, and the wire rollers connected with the left opening and closing clamp body and the right opening and closing clamp body and the left opening and closing clamp body and the right opening and closing clamp body are arranged on a hinge pin of the clamp seat; the connecting guide pipe, the left opening and closing clamp body and the right opening and closing clamp body are respectively connected with a screw driving system. The instrument provided by the invention is compact in structure, light in weight and high in driving precision, and the quick-changing efficiency of the instrument can be improved.

Instrument for robot-assisted micro-invasive surgery

Robot-assisted minimally invasive surgery (RMIS) is promising for improving surgical accuracy and dexterity. As the end effector of the robotic arm, the remote centre of motion mechanism is one of the requisite terms for guaranteeing patient safety. The existing remote centre of motion mechanisms are complex and large in volume, as well as high assembly requirement and unsatisfactory precise. This paper aimed to present a new remote centre of motion mechanism for solving these problems. A new mechanism based on the RMIS requirements is proposed for holding the laparoscope and generating a remote centre of motion for the laparoscope. The mechanism kinematics is then analysed from the perspective of the structural function, and its inverse kinematics is determined with a small number of calculations. Finally, the position deviation of the laparoscope rotational point is chosen as the index to evaluate the mechanism performance. The experiments are performed to test the deviation. The position deviations of the laparoscope rotational point do not exceed 2 mm, which is lower than that of the existing remote centre of motion mechanism. The 2 mm positioning error of the laparoscope won’t affect surgeon observation of the surgical field, and the pressure caused by the positioning error was acceptable for the skin elasticity. The proposed mechanism meets the RMIS requirement. The proposed mechanism can achieve the remote centre of motion for the laparoscope. Its simple and compact structure is beneficial to avoid the collision of robotic arms, and it can be applied on other robots for providing the instrument necessary motion in minimally invasive surgery.

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New remote centre of motion mechanism for robot-assisted minimally invasive surgery

Background
Pose optimization and port placement are critical issues for preoperative preparation in robot-assisted minimally invasive surgery (RMIS), and affect the robot performance and surgery quality.

Methods
This paper proposes a method for pose optimization and port placement for RMIS in cholecystectomy that considers both the robot and surgery requirements. The robot pose optimization was divided into optimization of the positioning joint configuration and optimization of the end effector configuration. To determine the optimal location for the trocar port placement, the operational workspace was defined as the evaluation index. The port area was divided into many sub-areas, and that with the maximum operational workspace was selected as the location for the port placement.

Results
Considering the left robotic arm as an example, the location for the port placement and joints angles for robotic arm configuration were discussed and simulated using the proposed method.

Conclusion
This research can provide guidelines for surgeons in preoperative preparation.

Pose optimization and port placement for robot-assisted minimally invasive surgery in cholecystectomy

The invention discloses a decoupled quick change surgical device for a robot assisted minimally invasive surgery, and relates to a surgical device for the robot assisted minimally invasive surgery, and in particular relates to the decoupled quick change surgical device for the robot assisted minimally invasive surgery, aiming at solving the problems of high probability of snap break of driving left finger and right finger, complex structure and over-long replacement time of surgical instruments in a surgical process existing in the conventional minimally invasive surgical device. The decoupled quick change surgical device comprises an upper blade transmission mechanism, a wrist transmission mechanism, a casing transmission mechanism, a lower blade transmission mechanism, a first resetting mechanism, a second resetting mechanism, a first guide mechanism, a second guide mechanism, a front-end surgical scissor mechanism, an adapter shell, an adapter upper cover, a casing, a wrist connecting piece, an upper blade traction lower steel wire, an upper blade traction upper steel wire, a wrist traction lower steel wire, a wrist traction upper steel wire, a lower blade traction lower steel wire, a lower blade traction upper steel wire and seven screws. The decoupled quick change surge surgical device is used in the robot assisted minimally invasive surgery.

Decoupled quick change surgical device for robot assisted minimally invasive surgery

Background Surgical instruments greatly impact the performance of robot-assisted minimally invasive surgery (RMIS) because they operate on tissues. Methods A snake-like surgical instrument, designed with 4 degrees of freedom (DOFs), is proposed for RMIS. The DOFs are as follows: opening and closing motions of the forceps, rotation of the forceps and bi-directional bending of the instrument. The performance of the instrument was evaluated using a prototype in vitro. Results All DOFs of the instrument were experimentally evaluated and proven sufficient for RMIS. In vitro testing showed that the operations of the proposed model were powerful and steady. Conclusions The position and posture of the surgical instrument could be adjusted in the body of the patient by its bending and rotational movements. The proposed model could therefore work as a competent assistant in multi-port RMIS and allow surgeons to perform better.

Snake-like surgical forceps for robot-assisted minimally invasive surgery.

The invention discloses a minimally invasive surgery robot 7-degree freedom operation master manipulator, and relates to a minimally invasive surgery robot; the operation master manipulator is used for solving the problems of complex structure and bad flexibility and university of the manipulator of the minimally invasive surgery robot. The master manipulator comprises a substrate, a turntable arranged on the substrate and rotated around a z axis, a link rod connected with the turntable and rotated around the x axis, a 1# self-rotating link rod connected with the link rod an rotated around the x axis, a 2# self-rotating link rod connected with the 1# self-rotating link rod and rotated around the x axis, and a clamping mechanism connected with the 2# self-rotating link rod; the clamping mechanism comprises a thumb part and an index finger part which are rotated face to face.

Ji Zhao

Papers

New remote centre of motion mechanism for robot-assisted minimally invasive surgery

Pose optimization and port placement for robot-assisted minimally invasive surgery in cholecystectomy

Decoupled quick change surgical device for robot assisted minimally invasive surgery

Snake-like surgical forceps for robot-assisted minimally invasive surgery.

Minimally invasive surgery robot 7-degree freedom operation master manipulator