Remote Center Of Motion Mechanism Research Articles

受動関節を有する空気圧駆動手術支援マニピュレータの開発

Recently robotic laparoscopic surgery has been widely performed. Most of surgical manipulator has RCM (Remote Center of Motion) mechanism, so operator must precisely adjust the center of motion to the insert port before the operation. If there is misalignment between the center point and the port, undesirable loads act on in active joints. The loads cause the friction negatively affecting position tracking and force estimation. In this research, we develop a manipulator that doesn’t require corresponding the center of motion and insert port precisely. Here we present the design of a pneumatically-driven surgical manipulator with a passive joint.

Type Synthesis of 1R1T Remote Center of Motion Mechanisms Based on Pantograph Mechanisms

The remote center of motion (RCM) mechanism is an important component of a minimally invasive surgery (MIS) robot. The feature of the RCM mechanism is that the output link can rotate around a fixed point and translate along an axis which passes the point; however, there is no revolute joint at the fixed point. The 3R1T RCM mechanism, which meets all the degrees-of-freedom (DOF) requirements of arbitrary MIS tools, can be assembled through many methods. An effective method is combining a planar closed-loop 1R1T RCM mechanism and two revolute joints. In this paper, we present an approach to construct 1R1T RCM mechanisms from pantograph mechanisms. First, pantograph mechanisms are divided into seven classifications according to the geometric transformations they represent. The concept of rigid motion tracking mechanism (RMTM) is proposed by combining two equivalent pantograph mechanisms. Then, a novel type synthesis method for 1R1T RCM mechanisms is discussed in detail, and it shows that a 1R1T RCM mechanism can be constructed by assembling an RMTM and a 1R1T mechanism. By this method, several examples are constructed.

Computer-aided pelvic reduction frame for anatomical closed reduction of unstable pelvic fractures.

Traditional closed reductions of unstable pelvic fractures are mainly performed by surgeons using manual manipulation and subjective verification based on intra-operative roentgenography. It is difficult to perform an accurate closed reduction because of a lack of adequate knowledge of the displacement patterns and an inability to apply the reduction in correct direction. Using the concept of the remote center of motion mechanism and computer-aided design software, we developed a pelvic reduction frame for use in anatomical closed reductions of unstable pelvic fractures. With three-dimensional reconstruction technique and the matrix algorithm, the spatial orientation of the displaced hemipelvis can be calculated and deconstructed into several rotational and translational movements that can be completed with the frame. To verify the accuracy of this system, the rotations were repeated 10 times in arbitrary degrees and directions. After the matrix is calculated, the displaced hemipelvis can be reduced to the anatomical position using our frame. The maximum residual translational and rotational displacements were less than 5 mm and 4 degrees, which indicated the accuracy of this system. The maximum average residual translation and rotation were 1.87 mm in Z-axis (ranging: 4.63-0.1 mm) and 1.1 degrees around Y-axis (ranging: 3.81-0.13 degrees), respectively. Only the Z-axial translation showed a statistically significant difference (p < 0.05). In conclusion, the proposed pelvic reduction frame could be a useful tool for the anatomical reduction of unstable pelvic fractures.

Development of the SAIT single-port surgical access robot--slave arm based on RCM mechanism.

An innovative single-port surgical robot has recently been developed by the Samsung Advanced Institute of Technology (SAIT). The robot can reach various surgical sites inside the abdominal cavity from a single incision on the body. It has two 7-DOF surgical tools, a 3-DOF endoscope, a flexible hyper-redundant 6-DOF guide tube, and a 6-DOF manipulator. This paper primarily focuses on the manipulator, called a slave arm, which is capable of setting the location of a Remote Center Motion (RCM) point. Because the surgical tools can explore the abdominal area through a small incision point when the RCM point is aligned with the incision area, the RCM mechanism is an integral part of the manipulator for single-port surgery. The mechanical feature, operational principle, control method, and the system architecture of the slave arm are introduced in this paper. In addition, manipulation experiments conducted validate its efficacy.

Optimization and preoperative adjustment design of remote center motion mechanism for minimally invasive surgical robot

Abstract In this paper, a new remote center motion (RCM) mechanism called triangle is proposed; this mechanism is simple and with high stiffness. A complete kinematic analysis and optimization algorithm implying AHP which is a combination of quantitative and qualitative analysis method incorporating the requirements for minimally invasive surgery (MIS) are performed to find the optimal link lengths of the manipulator. The results show that for the serial triangle two-link manipulator used to guide the surgical tool, the optimization link angles are 74° and 51°. Prior preoperative adjustment is usually realized by electromagnetic clutch. However, the disadvantage of this method is that the joint is complex, big, and heavy because of gravity balance mechanism. A new preoperative adjustment method realized by resistance compensation is proposed without electromagnetic clutch; the joint is simpler and lighter than the conventional joint.

Kinematic Design of a Novel Spatial Remote Center-of-Motion Mechanism for Minimally Invasive Surgical Robot

To deliver more value to the healthcare industry, a specialized surgical robot is needed in the minimally invasive surgery (MIS) field. To fill this need, a compact hybrid robotic wrist with four degrees of freedom (DOFs) is developed for assisting physicians to perform MIS. The main body of the wrist is a 2DOF parallel mechanism with a remote center-of-motion (RCM), which is located outside the mechanism. From the mechanical point of view, it is different from existing 2DOF spherical mechanisms, since there is no physical constraint on the RCM. Other DOFs of the wrist are realized by a revolute joint and a prismatic joint, which are serially mounted on the movable platform of the parallel mechanism. The function of these DOFs is to realize the roll motion and the in-out translation of the surgical tool. Special attention is paid to the parallel RCM mechanism. The detailed design is provided and the kinematic equations are obtained in the paper. Further, the Jacobian matrix is derived based on the kinematic equations. Finally, the paper examines the singularity configurations and implements the condition number analysis to identify the kinematic performance of the mechanism.

Remote Center of Motion (RCM) Mechanisms for Surgical Operations

Nowadays, surgical applications, entering the body through a small incision with laparoscopic procedures are performed and are expanding the use of robots for these operations. In existing systems, conventional robots are used for the body. Surgical procedure is carried out by a separate mechanism which is attached to the end of the robot and robot is used to positioning this mechanism. These mechanisms are called Remote Center of Motion (RCM) mechanism. In this paper, the literature on studies performed about the parallel, spherical and hybrid RCM mechanisms are examined and classified.

Type Synthesis of 1R1T Remote Center of Motion Mechanisms

Type Synthesis of 1R1T Remote Center of Motion Mechanisms

A parallelogram-based compliant remote-center-of-motion stage for active parallel alignment.

Parallel alignment stage with remote-center-of-motion (RCM) is of key importance in precision out-of-plane aligning since it can eliminate the harmful lateral displacement generated at the output platform. This paper presents the development of a parallelogram-based compliant RCM stage for active parallel alignment. Different from conventional parallelogram-based RCM mechanism, the proposed stage is designed with compliant mechanisms, which endows the stage with many attractive merits when used in precision micro-/nanomanipulations. A symmetric double-parallelogram mechanism (SDPM) based on flexure hinges is developed as the rotary guiding component to realize desired RCM function. Due to the geometrical constraint of the SDPM, the operating space of the stage can be easily adjusted by bending the input links without loss of rotational precision. The stage is driven by a piezoelectric actuator and its output motion is measured by non-contact displacement sensors. Based on pseudo-rigid-body simplification method, the analytical models predicting kinematics, statics, and dynamics of the RCM stage have been established. Besides, the dimensional optimization is conducted in order to maximize the first resonance frequency of the stage. After that, finite element analysis is conducted to validate the established models and the prototype of the stage is fabricated for performance tests. The experimental results show that the developed RCM stage has a rotational range of 1.45 mrad while the maximum center shift of the RCM point is as low as 1 μm, which validate the effectiveness of the proposed scheme.

A Class of 2-Degree-of-Freedom Planar Remote Center-of-Motion Mechanisms Based on Virtual Parallelograms

Robot-assisted minimally invasive surgery (MIS) has shown tremendous advances over the traditional technique. The remote center-of-motion (RCM) mechanism is one of the main components of a MIS robot. However, the widely used planar RCM mechanism, with double parallelogram structure, requires an active prismatic joint to drive the surgical tool move in–out of the patient’s body cavity, which restricts the dexterity and the back-drivability of the robot to some extent. To solve this problem, a two degree-of-freedom (DOF) planar RCM mechanism type synthesis method is proposed. The basic principle is to construct virtual double parallelogram structure at any instant during the mechanism movements. Different with the existing ones, both of the actuated joints of the obtained RCM mechanism are revolute joints. Combining the proposed mechanism with a revolute joint whose axis passes through the RCM point to drive the whole mechanism out of the plane, the spatial RCM mechanisms to manipulate surgical tool in three-dimension (3D) space can be obtained; and the 3D RCM mechanism can be used for manipulating multi-DOF instruments in a robot-assisted MIS or can be used as an external positioner in robotic single-port surgeries.

Surgical robot for single-incision laparoscopic surgery.

This paper introduces a novel surgical robot for single-incision laparoscopic surgeries. The robot system includes the cone-type remote center-of-motion (RCM) mechanism and two articulated instruments having a flexible linkage-driven elbow. The RCM mechanism, which has two revolute joints and one prismatic joint, is designed to maintain a stationary point at the apex of the cone shape. By placing the stationary point on the incision area, the mechanism allows a surgical instrument to explore the abdominal area through a small incision point. The instruments have six articulated joints, including an elbow pitch joint, which make the triangulation position for the surgery possible inside of the abdominal area. The presented elbow pitch structure is similar to the slider-crank mechanism but the connecting rod is composed of a flexible leaf spring for high payload and small looseness error. We verified the payload of the robot is more than 10 N and described preliminary experiments on peg transfer and suture motion by using the proposed surgical robot.

Kinematics and synthesis of a type of mechanisms with multiple remote centers of motion

Remote center of motion (RCM) mechanism, widely used as a wrist of minimally invasive surgery robot, is a kind of minor-mobility mechanism with part of it rotating around a fixed point distal from it. However, there is no physical revolute joint at that point. In this paper, kinematics of mechanisms with two remote centers of motion or multiple remote centers of motion (multi-RCM) are researched. The relationship between geometrics and kinetic characteristics of RCM mechanisms is found. Mechanisms with multi-loop kinematic chain are developed and are used to synthesize multiple RCM mechanisms. This type of dimension synthesis method proposed to design multi-RCM mechanisms just needs the initial condition of fixed positions of the frame and remote centers. A synthesis example and a potential application are presented. The synthesis method of multi-RCM mechanisms is effective in constructing new type of mechanisms.

A Family of Remote Center of Motion Mechanisms Based on Intersecting Motion Planes

If a part of a mechanism is restrained to rotate about a point not physically belonging to it, the mechanism is called a remote center-of-motion (RCM) mechanism. The RCM mechanisms are generally designed especially for robot-assisted minimally invasive surgery (MIS) systems, for which great progress has been made in recent years. An RCM mechanism type synthesis method is proposed in this paper by generalizing the intersection of motion planes. The existence of such motion planes is the fundamental feature of the classic Sarrus mechanism, for instance. The basic principle of the type synthesis method is to combine some typical planar mechanisms where their respective motion planes are free to tilt. Hence, the intersection line varies as the planes tilt. There is one invariant point on this intersection line, however, and this is the RCM point. The proposed method is used to design a class of spatial RCM mechanisms. And the kinematic characteristics of them are presented in this paper. In particular, several fully parallel two degree-of-freedom (DOF) RCM mechanisms and a 1-DOF RCM mechanism are considered in detail. Two spatial 3-DOF overconstrained RCM mechanisms are also obtained by the proposed method.

A novel remote center of motion mechanism for the force‐reflective master robot of haptic tele‐surgery systems

An effective master robot for haptic tele-surgery applications needs to provide a solution for the inversed movements of the surgical tool, in addition to sufficient workspace and manipulability, with minimal moving inertia. A novel 4 + 1-DOF mechanism was proposed, based on a triple parallelogram linkage, which provided a Remote Center of Motion (RCM) at the back of the user's hand. The kinematics of the robot was analyzed and a prototype was fabricated and evaluated by experimental tests. With a RCM at the back of the user's hand the actuators far from the end effector, the robot could produce the sensation of hand-inside surgery with minimal moving inertia. The target workspace was achieved with an acceptable manipulability. The trajectory tracking experiments revealed small errors, due to backlash at the joints. The proposed mechanism meets the basic requirements of an effective master robot for haptic tele-surgery applications.

2A1-L06 心筋シート移植のための心表面運動同期機能を有したロボットシステムの開発(手術支援ロボティクス・メカトロニクス(1))

Myoblast cell sheets are taking into the clinical treatment of heart disorders. In our study, we proposed a surgical robot system, includes a robot system with the characteristics of Double RCM (remote center of motion) mechanism, which can cancel and compensation the beating heart surface movement for the myoblast cell sheet transplantation and two endoscopic cameras to capture heart surface motion without obstruct the transplantation of the sheets. The linear and rotation motion of the robot system are totally isolated, realized by employed a Double RCM mechanism. An experiment is conducted to evaluate the tracking accuracy of our robot system in tracking an approximate -period moving target. The tracking data is updating by Polaris system in 30Hz. From the experiment, we got the results that the linear and error is 4.67±3.73 mm and the rotation tracking error is 2.86±5.50 degree.

Kinematic design considerations for minimally invasive surgical robots: an overview

Kinematic design is a predominant phase in the design of robotic manipulators for minimally invasive surgery (MIS). However, an extensive overview of the kinematic design issues for MIS robots is not yet available to both mechanisms and robotics communities. Hundreds of archival reports and articles on robotic systems for MIS are reviewed and studied. In particular, the kinematic design considerations and mechanism development described in the literature for existing robots are focused on. The general kinematic design goals, design requirements, and design preferences for MIS robots are defined. An MIS-specialized mechanism, namely the remote center-of-motion (RCM) mechanism, is revisited and studied. Accordingly, based on the RCM mechanism types, a classification for MIS robots is provided. A comparison between eight different RCM types is given. Finally, several open challenges for the kinematic design of MIS robotic manipulators are discussed. This work provides a detailed survey of the kinematic design of MIS robots, addresses the research opportunity in MIS robots for kinematicians, and clarifies the kinematic point of view to MIS robots as a reference for the medical community.

Classification and type synthesis of 1-DOF remote center of motion mechanisms

Abstract Type synthesis of 1-DOF remote center of motion (RCM) mechanisms is the preliminary for research on many multi-DOF RCM mechanisms. Since types of existing RCM mechanisms are few, it is necessary to find an efficient way to create more new RCM mechanisms. In this paper, existing 1-DOF RCM mechanisms are first classified, then base on a proposed concept of the planar virtual center (VC) mechanism, which is a more generalized concept than a RCM mechanism, two approaches of type synthesis for 1-DOF RCM mechanisms are addressed. One case is that a 1-DOF parallel or serial–parallel RCM mechanism can be constructed by assembling two planar VC mechanisms; the other case, a VC mechanism can be expanded to a serial–parallel RCM mechanism. Concrete samples are provided accordingly, some of which are new types.

Design of double parallelogram remote-center-of-motion mechanisms

The double parallelogram type of remote center of motion (RCM) mechanisms is generally used as wrist module in minimally invasive surgery (MIS) assisted robots, which can provide a fixed entry point during operation process, enhance safety and quality of the surgery, and give facilities for surgeons. With type synthesis, 10 types of double parallelogram RCM mechanisms are enumerated. By making some links crooked, the virtual center can be arranged properly, which also makes the arrangements of end-effector and motor more convenient. In order to design a double parallelogram RCM mechanism, six independent parameters are needed. The forces and structure stiffness of linkage are analyzed to assist in determining sectional sizes of links. The driven moment is estimated to select a right motor. The analysis shows that a double parallelogram RCM mechanism can be balanced by one counterweight. At last, an example is given to illuminate the mechanism's feasibility and validity.