Robot-assisted minimally invasive surgery (MIS) has shown tremendous advances over the traditional techniques. To improve dexterity and back-drivability of the existing planar remote center-of-motion (RCM) mechanism, on which an active prismatic joint is required to drive the surgical tool move in–out of the patient's body, a two degrees-of-freedom (DOFs) planar RCM mechanism is proposed by constructing virtual parallelograms in this paper. The mechanism can be considered as a generalized double parallelogram; both of the actuated joints are revolute joints. This feature enhances the intrinsic back-drivability of the mechanism. The mathematical framework is introduced first to prove that the mechanism could execute RCM. Then, the inverse kinematics of the planar mechanism is solved, and the Jacobian matrix is derived in this paper. Further, the singularity and the kinematic performance based on the kinematic equations are investigated, and the workspace of the mechanism is verified. Finally, a prototype was built to test the function of the proposed RCM mechanism. The results show that the mechanism can fulfill the constraint of MIS, and it can be used as the basic element of the active manipulator in an MIS robot.

Natural orifice transluminal endoscopic surgery (NOTES) has attracted continuous attention in recent decades, but its confined workspace restricts the dexterity and manipulability of instruments. Instruments with multiple degrees of freedom (DOF) and variable stiffness are desired to achieve flexible operation with sufficient load capacity. This article presents a novel robotic instrument, which can assist NOTES. The instrument is 6.5 mm in diameter with 7 DOFs. The three continuum elastic joints are made of helical springs with high torsional rigidity, whose wires have a rectangular cross section. Patterned concentric tubes are designed to change the stiffness of the force transmission structure of the passive arm so that the stability and rigidity of the instrument can be improved. Analytical solutions of inverse kinematics are obtained based on the arrangement of coupled joints designed for creating triangulation. The disk-elastomer model is established to simplify the derivation of kinematics, and the relationship between the slack of the driving cable and the joint parameters is derived. The trajectory tracking accuracy, bending accuracy, and the ability of variable stiffness of the proposed instrument are verified with experiments.

Robotic grippers, which act as the end effector and contact the objects directly, play a crucial role in the performance of the robots. In this paper, we design and analyze a new robotic gripper based on the braided tube. Apart from deployability, a self-forcing mechanism, i.e., the holding force increases with load/object weight, facilitates the braided tube as a robotic gripper to grasp objects with different shapes, weights, and rigidities. First, taking a cylindrical object as an example, the self-forcing mechanism is theoretically analyzed, and explicit formulas are derived to estimate the holding force. Second, experimental and numerical analyses are also conducted for a more detailed understanding of the mechanism. The results show that a holding force increment by 120% is achieved due to self-forcing, and the effects of design parameters on the holding force are obtained. Finally, a braided gripper is fabricated and operated on a KUKA robot arm, which successfully grasps a family of objects with varying shapes, weights, and rigidities. To summarize, the new device shows great potentials for a wide range of engineering applications where properties of the objects are varied and unpredictable.

Current surgical instruments with fewer degrees-of-freedom (DOF) for minimally invasive surgery (MIS) have limited capability to perform complicated and precise procedures, such as suturing and knot-tying. To address such a problem, a modular dexterous hand-held surgical robot with an ergonomic handle and 4DOF interchangeable instruments was developed. The kinematic arrangement of the instrument and that of the handle were designed to be the same. A compact roll-yaw-roll transmission was proposed applying cable-driven mechanism. Performance experiments were carried out to evaluate the effectiveness of the overall system. The measured grip forces of the robot ranged from 8.63 N to 19.18 N. The suturing performance score of the robot was significantly higher than that of the conventional instrument (28.8 ± 5.02 versus 17.2 ± 7.43, p = 0.041). The trajectory tracking test and animal experiment verified the accuracy and feasibility of the robot. The proposed robot could improve the surgical performance of MIS, providing various end-effectors and having an intuitive interface in the meantime.

Increased demand for minimally invasive surgery has accelerated the adoption of natural orifice transluminal endoscopic surgery. Meanwhile, the increasing complexity of endoscopic procedures has raised the demand for endoscopist competence. In this paper, we present a novel endoscopic system to perform robotic intervention with a flexible endoscope to enhance the safety and efficiency of endoscopy. The system is composed of an endoscopic manipulation module (EMM) for control of endoscopic interventions, a 6 DOFs robotic arm for adjusting the pose of EMM, and a haptic interface for telecontrol. The compact system enables endoscopists to remotely and stably operate flexible endoscopes with one hand. Leader-follower control strategy with active constraint is proposed to guide the motion of the flexible endoscope within the safe working space. The proposed system is validated by recruiting subjects to perform target area localization and endoscopic examinations through highly realistic upper digestive tract phantom. The system can reduce the time of target area localization by at least 10% compared to manual control. The mean angle error can be reduced by 75% with the help of the constraint force. Results demonstrate the potential clinical value of the system in efficient operation and safety control.