Remote Center Of Motion Mechanism Research Articles

Development of a 2-DOF Singularity-Free Spherical Parallel Remote Center of Motion Mechanism With Extensive Range of Motion

Development of a 2-DOF Singularity-Free Spherical Parallel Remote Center of Motion Mechanism With Extensive Range of Motion

Implementation and Evaluation of a Uterine Manipulation System Incorporated with an Existing Tiltable-Tip Uterine Manipulator for Gynecological Laparoscopy

In gynecologic surgery, a uterine manipulator is one of the instruments used to perform the laparoscopy. Throughout the past decade, a number of robotic technology applications used for uterine manipulation during surgery have been designed with the aim of increasing the efficiency, improving the precision, and reducing the workload of medical assistants. Although the RCM (Remote Center of Motion) mechanism is one of the key features in a Minimally Invasive Surgical (MIS) robot, the preliminary result in this study, in which the RCM mechanism was applied in a uterine manipulation robot, proved that this may cause unpleasant sensations such as irritation or harm to the nearby area during such manipulation. Therefore, a design of a non-RCM 2-DoF (Degree of Freedom) Robotic Uterine Manipulation System, in cooperation with an existing, reusable and tiltable-tip uterine manipulator, for laparoscopic gynecologic surgery has been proposed and evaluated via a mathematical model along with numerical analysis, a 3D uterus model, and a 1:1 uterus manikin model in order to demonstrate the use of the essential functions. According to the experimental results, the maximum load of 500 g has been handled well by the prototype, with the movement ranges of ±150° in the roll panel and ±90° in the pitch panel (0∼90° for anteversion and 0∼−90° for retroversion, if needed, which can be achieved by rotating the instrument to the other side). Furthermore, to verify this new design prior to its use on patients, and also in consideration of the ethics of human experimentation, through extensive testing on five donated soft-tissue cadavers, the proposed robot received positive feedback from all five surgeons performing the experiments and could offer effective uterine manipulation at the angular velocity of 4 °/s (0.67 RPM) with steady delineation of the vaginal fornices to create necessary motions in the pitch and roll panels of 30∼80° and ±15°, respectively, providing efficient visualization of the uterus. These features make this robot a valuable addition to the surgical instruments available to gynecologic surgeons.

Design and Analysis of a Spatial 2R1T Remote Center of Motion Mechanism for a Subretinal Surgical Robot

With advances in minimally invasive ophthalmic surgery (MIOS), novel vitreoretinal surgeries have been proposed to treat retinal diseases. Due to the limitations of manual techniques, surgical robots have been introduced for such surgeries. Among ophthalmic surgical robots, the remote center of motion (RCM) mechanism is widely used due to its unique advantages. In this paper, a novel RCM is proposed. Based on the configuration, the kinematics and singularity are analyzed. Subsequently, the planar workspace is analyzed based on ocular anatomy and the requirements of MIOS. The optimal configuration is selected according to the workspace coverage analysis, and the three-dimensional workspace is obtained. Finally, a prototype is built, and the motion is validated. When compared with the related prior RCM mechanisms, the resulting design has qualified workspace coverage, more concise kinematics, and reduced motion coupling with all actuators placed at the distal end of the base. The proposed RCM mechanism is suitable for common MIOS. Future research will further optimize the mechanical structure and control algorithm to improve the accuracy of the prototype.

Search for Optimal Parameters in the Control Structure of a Surgical System for Soft Tissue Operations Based on In Vitro Experiments on Cardiovascular Tissue

The surgical robots currently used in cardiac surgery are equipped with a remote center of motion (RCM) mechanism that enables the required spherical workspace. The dynamics model of the surgical robot’s RCM mechanism presented in this work includes a direct current (DC) motor, an optimal proportional–integral–derivative (PID) controller, and a LuGre friction model that takes into account the Stribeck effect and surface deformation. A finite element method (FEM) analysis of transients was carried out using the energy hypothesis of von Mises with an optimal input signal from the mechatronic system with a PID controller obtained using the Runge–Kutta differentiation method in the Dormand–Prince ordinary differential equations variant (ODE45). Five criteria were adopted for the objective function: the safety factor related to the stress function in the time-varying strength problem, the first natural frequency related to stiffness and the resonance phenomenon, the buckling coefficient in the statics problem related to stability, the static factor of safety, and the displacement of the operating tip. The force inputs to the dynamics model were derived from in vitro force measurements on cardiovascular tissue using a force sensor. The normality of the statistical distribution of the experimental data was confirmed using the Kolmogorov–Smirnov statistical test. The problem of multi-criteria optimization was solved using the non-sorter genetic algorithm (NSGA-II), the finite element method, and the von Mises distortion energy hypothesis. Velocity input signals for the transient dynamics model were obtained from a second in vitro experiment on cardiovascular tissue using the minimally robotic invasive surgery (MIRS) technique. An experienced cardiac surgeon conducted the experiment in a modern method using the Robin Heart Vision surgical robot, and a system of four complementary metal–oxide–semiconductor (CMOS) optical sensors and ariel performance analysis system (APAS-XP 2002) software were used to obtain the endoscopic tool trajectory signal. The trajectory signal was accurate to ±2 [mm] in relation to the adopted standard, and it was smoothed using the Savitzky–Golay (SG) polynomial smoothing, whose parameters were optimally selected using the Durbin–Watson (DW) statistical test.

OCT-based intra-cochlear imaging and 3D reconstruction: ex vivo validation of a robotic platform.

The small size of the cochlea, and its location deeply embedded in thick temporal bone, poses a challenge for intra-cochlear guidance and diagnostics. Current radiological imaging techniques are not able to visualize the cochlear microstructures in detail. Rotational optical coherence tomography (OCT) fibers show great potential for intra-cochlear guidance. The generated images could be used to map, and study, the tiny cochlear microstructures relevant for hearing. This work describes the design of a rotational OCT probe with an outer diameter of 0.9 mm. It further discusses a robotic system, which features a remote center of motion mechanism, dedicated to the probe's positioning, fine manipulation and stable insertion into the cochlear micro-spaces. Furthermore, the necessary calibration steps for 3D reconstruction are described, followed by a detailed quantitative analysis, comparing the 3D reconstructions using a synthetic, 2:1 scaled scala tympani model with a reconstruction from micro-CT, serving as the ground truth. Finally, the potential of the system is demonstrated by scanning a single ex vivo cadaveric human cochlea. The study investigates five insertions in the same 2:1 scaled tympani model, along with their corresponding 3D reconstruction. The comparison with micro-CT results in an average root-mean-square error of 74.2 µm, a signed distance error of 38.1 µm and a standard deviation of 63.6 µm. The average F-score of the reconstructions, using a distance threshold of 100 and 74.2 µm, resulted in 83.0% and 71.8%, respectively. Insertion in the cadaveric human cochlea showed the challenges for straight insertion, i.e., navigating the hook region. Overall, the system shows great potential for intra-cochlear guidance and diagnostics, due to the system's capability for precise and stable insertion into the basal turn in the scala tympani. The system, combined with the calibration procedure, results in detailed and precise 3D reconstructions.

Realization and Control of Robotic Injection Prototype With Instantaneous Remote Center of Motion Mechanism.

Although there have been studies conducted on the instantaneous remote center of motion (RCM) mechanism, the general closed-loop control method has not been studied. Thus, this article fills that gap and employs the advantages of this mechanism to develop a novel injection system. The injection prototype involves the instantaneous RCM mechanism, insertion unit and injection unit. The RCM system is investigated in the presence of time-varying axial stiffness of the screw drive and underactuated case. For safe interaction, compliance control is designed in the insertion system. The stability of all separate systems is investigated with the bounded parameter variation rate. The injection prototype and a robot end-effector were then combined to perform injection. Our RCM prototype can achieve a large workspace, and its control effectiveness was verified by multiple frameworks and comparison with previous studies. Compliance-controlled insertion can achieve accurate depth regulation and zero-impedance control for manually operating the needle. With the help of three-dimensional reconstruction and hand/eye calibration, the manipulator can guide the injection prototype to a proper pose for injection of a face model. The injection prototype was successfully designed. The effectiveness of the whole control system was verified by simulations and experiments. The particular robotic injection task can be performed by the prototype. This article provides alternative schemes for developing an instantaneous RCM system, screw drive-based surgical tool, and robotic insertion with small needles.

Robotic system for nasopharyngeal swab sampling based on remote center of motion mechanism.

In this study, a robotic system is proposed for nasopharyngeal (NP) swab sampling with high safety and efficiency. Most existing swab-sampling robots have more than six degrees of freedom (DOFs). However, not all six DOFs are necessarily required for NP swab sampling. A high number of DOFs can cause safety problems, such as collisions between the robot and patient. We developed a new type of robot with four DOFs for NP swab sampling that consists of a two DOFs remote center of motion (RCM) mechanism, a two DOFs insertion mechanism, and a nostril support unit. With the nostril support unit, the robot no longer needs to adjust the insertion position of the swab. The proposed robot enables the insertion orientation and depth to be adjusted according to different postures or facial shapes of the subject. For intuitive and precise remote control of the robot, a dedicated master device for the RCM and a visual feedback system were developed. The effectiveness of the robotic system was demonstrated by repeatability, RCM accuracy, tracking accuracy, and in vitro phantom experiments. The average tracking error between the master device and the robot was less than 2mm. The contact force exerted on the swab prior to reaching the nasopharynx was less than 0.04 N, irrespective of the phantom's pose. This study confirmed that the RCM-based robotic system is effective and safe for NP swab sampling while using minimal DOFs.

RCM adjustment for a double-parallelogram based RCM mechanism used for MIS robots

The inevitable errors in the manufacturing, assembly, and testing of a remote center-of-motion (RCM) mechanism lead to the erroneous link parameters which deviate its geometry. Consequently, the motion, as well as the force, become non-zero at the entry port to the patient’s body which is undesirable. To address this issue, the current work first presents the accurate kinematic model of the RCM of an exemplary double-parallelogram-based RCM mechanism. Thereafter, it introduces the RCM adjustment concept and a flexure-based compliant mechanism to nullify/minimize the said deviation. For the analytical design of the flexure element, this paper makes the required design calculations and performs the finite element analysis. It is followed by the disclosure of the RCM Adjustment System and a systematized method of RCM adjustment for a mechanically constrained RCM device. The devised system is based on the prescribed compliant mechanism design and is advantageous, over the traditional RCM adjustments. The potential of the proposed concept lies in the fact that it is not limited to the adopted mechanism only rather, it is extendable to other mechanisms as well which was missing in the prior art. In addition, it offers a more simplified and economical design. Further, an initial prototype of the exemplary mechanism is manufactured using laser micromachining and rapid prototyping techniques. Both analytical as well as physical validations have been performed which proved the efficacy of the proposed kinematic modeling concept. Furthermore, the prototype of the introduced RCM Adjustment System is manufactured as a single-piece design which demonstrated its effectiveness. The preferred embodiment of the same is the said double-parallelogram-based RCM mechanism which is most widely used for robot-assisted minimally invasive surgery (RAMIS). It is designed in a SolidWorks environment and manufactured using Al6101-T6 and SS304 as link material, and a variety of standard elements.

Development of a Base-Actuated Three-Rhombus Configured Remote Center of Motion Mechanism for Lumbar Puncture

Abstract Owing to the advantages of safety and reproducibility, remote center of motion (RCM) mechanisms are widely adopted in lumbar puncture (LP) procedures to guide the insertion angle and depth of the end effector. However, the proximal-actuated pattern in existing RCM mechanisms occupies a large space near the end effector, which obstructs the visual field and increases the system inertia. In this work, a base-actuated three-rhombus configured RCM mechanism for LP operation is first proposed, where the symmetric three-rhombus scheme is designed for motion transmission. As a result, the rotational and translational motions of the needle are respectively realized through the homodromous and heterodromous actuation of the two base-mounted motors. Kinematic models are established to analyze the manipulability, singularity, and workspace of the RCM mechanism theoretically. The parameter optimization procedure is provided to minimize the footprint of the RCM mechanism. Experimental results show that the mechanism reaches an insertion angle from −29.2 deg to 29.2 deg, a maximum insertion depth of 60.02 mm, and a footprint of 4.98 × 104 mm2. The relative error of the RCM point is 1.1 mm.

Design, Control, and Experiments of A Novel Robotic Uterine Manipulator with the Motorized 3-DoF Manipulation Rod.

To address the issue of declining performance over time with manual uterine manipulation during minimally invasive gynecologic surgery, we propose a novel uterine manipulation robot that offers tireless, stable, and safer manipulation. This proposed robot consists of a 3-DoF remote center of motion (RCM) mechanism and a 3-DoF manipulation rod. The RCM mechanism uses a single-motor bilinear-guided design that allows for a wide range of pitch motion (-50 to 34 degrees) while maintaining a compact structure. The manipulation rod has a tip diameter of only 6 mm, allowing it to accommodate almost any patient's cervix. The 30-degree distal pitch motion and ± 45-degree distal roll motion of the instrument further improve uterine visualization. The tip of the rod can be opened into a T-shape to minimize damage to the uterus. Laboratory tests have revealed that our device has a highly precise mechanical RCM accuracy of 0.373mm and is capable of handling a maximum load of 500g. Furthermore, through clinical testing, the robot has been proven to offer improved manipulation and visualization of the uterus, making it a valuable addition to the surgical tools available to gynecologists.

Design, Dimensional Synthesis and Evaluation of a Novel Two-Degrees-of-Freedom Spherical Remote Center of Motion Mechanism for Minimally Invasive Surgery

Abstract With the development of minimally invasive surgery (MIS) technology, higher requirements are put forward for the performance of remote center of motion (RCM) manipulator. This paper presents the conceptual design of a novel two-degrees-of-freedom (2-DOF) spherical RCM mechanism, whose axes of all revote joints share the same RCM. Compared with the existing design, the proposed mechanism indicates a compact design and high structure stability, and the same scissor-like linkage makes it easy to realize modular design. It also has the advantages of singularity-free and motion decoupling in its workspace, which simplifies the implementation and control of the manipulator. In addition, compared with the traditional spherical scissor linkage mechanism, the proposed mechanism adds a rotation constraint on the output shaft to provide better operating performance. In this paper, the kinematics and singularities of different cases are deduced and compared, and the kinematic model of the best case is established. According to the workspace and constraints in MIS, the optimal structural parameters of the mechanism are determined by dimensional synthesis with the goal of optimal global operation performance. Furthermore, a prototype is assembled to verify the performance of the proposed mechanism. The experimental results show that the two-degrees-of-freedom prototype can provide a reliable RCM point. The compact design makes the manipulator have potential application prospects in MIS.

최소침습 골절정복 수술에서 나사못 삽입 경로를 유도하는 시스템

In this paper, we propose a system to detect the location and direction of locking screw insertion using only a fluoroscopic image and guide screw insertion path, with a device that combines a SCARA robot arm and a conical remote center-of-motion (RCM) mechanism. In the proposed system, the target location and direction for screw insertion were derived from the fluoroscopic image of an intramedullary nail. The insertion guidance device comprise the SCARA robot arm and the RCM mechanism. The insertion guidance device calculated the current indicated path through forward kinematics analysis, and the target path and the current path were transmitted to the orthopedic surgeon through the control program. Moreover, the insertion guidance device set the insertion position and direction independently. The orthopedic surgeon first adjusted the SCARA robot arm to match the insertion position value to the target value and then sequentially adjusted the RCM mechanism so that the insertion direction matched the target value. After determining the insertion position and direction, the orthopedic surgeon inserted the surgical instrument through the path guided by the insertion guidance device and fastened the screw to the bone fragments and the intramedullary nail. When the proposed screw insertion guidance system was applied to fracture surgery, the locking screw was fastened with a minimum number fluoroscopic image, thus reducing surgery time and radiation exposure. The validity of the proposed method was confirmed through simulations and experiments using a fracture model.

Sensitivity analysis of a double-parallelogram based RCM mechanism used for MIS robots

Parallelogram-based remote center-of-motion (RCM) mechanisms are extensively used to design robots for minimally invasive surgery (MIS). For their kinematic modeling, classically, it is assumed that link parameters of the opposite sides of constituting parallelograms are equal which made the RCM an invariant point and simplified the prescribed modeling process. However, link parameter equality does not exist in actual practice due to the inevitable constraints of manufacturing, assembly and testing/measurement, etc. Consequently, the RCM and surgical end-effector deviate from their theoretically designed positions. This paper introduces a novel approach to model the kinematics of parallelogram-based mechanisms by accounting for the error in manufactured link parameters. Additionally, it works out the types, possible ways, order, and nature of the said deviation. Further, a double-parallelogram-based RCM mechanism is adopted to demonstrate the proposed concept, and a prototype of the same is manufactured using laser micromachining and rapid prototyping techniques. Thereafter, the developed kinematic models are validated both analytically and physically. In contrast to the results given by the conventional kinematic modeling approach, the results obtained through the proposed approach and performed experiment showed better agreement with each other. The sensitivity of RCM and surgical end-effector to the inequalities, involved in the manufactured prototype, is revealed through several plots in the Matlab environment. A significant improvement in positional accuracy of the RCM and surgical end-effector have been achieved. It proves the efficacy of the presented method and it is believed that it applies to other parallelogram-based mechanisms as well.

Development of five-axis robot with Remote Center of Motion mechanism for non-destructive testing

Development of five-axis robot with Remote Center of Motion mechanism for non-destructive testing

Development of a Novel Low-profile Robotic Exoskeleton Glove for Patients with Brachial Plexus Injuries.

This paper presents the design and development of a novel, low-profile, exoskeleton robotic glove aimed for people who suffer from brachial plexus injuries to restore their lost grasping functionality. The key idea of this new glove lies in its new finger mechanism that takes advantage of the rigid coupling hybrid mechanism (RCHM) concept. This mechanism concept couples the motions of the adjacent human finger links using rigid coupling mechanisms so that the overall mechanism motion (e.g., bending, extension, etc.) could be achieved using fewer actuators. The finger mechanism utilizes the single degree of freedom case of the RCHM that uses a rack-and-pinion mechanism as the rigid coupling mechanism. This special arrangement enables to design each finger mechanism of the glove as thin as possible while maintaining mechanical robustness simultaneously. Based on this novel finger mechanism, a two-finger low-profile robotic glove was developed. Remote center of motion mechanisms were used for the metacarpophalangeal (MCP) joints. Kinematic analysis and optimization-based kinematic synthesis were conducted to determine the design parameters of the new glove. Passive abduction/adduction joints were considered to improve the grasping flexibility. A proof-of-concept prototype was built and pinch grasping experiments of various objects were conducted. The results validated the mechanism and the mechanical design of the new robotic glove and demonstrated its functionalities and capabilities in grasping objects with various shapes and weights that are used in activities of daily living (ADLs).

A family of RCM mechanisms: Type synthesis and kinematics analysis

• Propose a novel family of 2-DOF remote center-of-motion parallel mechanism. • The RCM points can be located at variable positions by deforming linkages. • Propose a type synthesis method for RCM and 2T mechanisms. • Propose a combined Jacobian matrix to analyze the complex kinematics. • The non-constrained RCM points contribute to more adaptable MIS manipulators. The remote center-of-motion (RCM) mechanism plays an important role in surgery robotics, exoskeleton robots, haptic devices, pointing mechanisms and so on because of the movements of their end-effector through a fixed point. However, the positions of RCM points are always constrained by the joints. In this paper, a family of two-degree-of-freedom (2-DOF) RCM mechanisms are proposed based on the two translational DOFs (2T) parallel mechanism and the redundant constraint linkage. The RCM points of the proposed mechanisms can be located at any position without constraints, which highlights the remote feature of RCM and contributes to more adaptable manipulators. The redundant constraint linkage of the mechanisms is bestowed a new function as an end-effector. A type synthesis method for the family of RCM mechanisms is proposed by the screw theory. As a subprocedure, 2T parallel mechanisms with a spherical surface shaped workspace can be generated innovatively and classified by the overconstrained dimensions. Finally, different RCM mechanisms are constructed to prove the type synthesis method and discussed by kinematics analysis.

Development of an Inherently Safe Nasopharyngeal Swab Sampling Robot Using a Force Restriction Mechanism

The demand for autonomous nasopharyngeal swab sampling robot systems is increasing owing to the recent outbreak of the respiratory virus pandemic. To protect the medical staff from infection, automatic upper respiratory sample collecting robotic systems are needed. The nasopharyngeal swab sampling robot proposed in this study is composed of a unique force restriction mechanism, a precise 3-axis force sensor, and a compact remote center of motion (RCM) mechanism, which are designed to enhance safety and efficiency. The proposed force restriction mechanism has a constant repulsive force finely adjustable using specially designed leaf spring structures. The force sensor is a capacitance-type 3-axis force sensor based on flexure mechanisms. Owing to the RCM mechanism, the distal end of the swab remains stationary. The effectiveness of the proposed robot was verified by various experiments, including restriction force measurement and a sampling success rate test.

A class of spatial remote center-of-motion mechanisms and its forward kinematics

AbstractRobot-assisted minimally invasive surgery (MIS) has shown tremendous advances over the traditional technique. A crucial challenge for developing a MIS robot is the kinematic design of the remote center-of-motion (RCM) mechanism. In this paper, a class of spatial RCM mechanism is analyzed. They are obtained by generating virtual parallelograms. The main process is to construct a line that passes through a fixed point under the mechanical constraint. The axis of the surgical tool is then constrained to parallel with that line. Hence, due to the geometrical feature of the parallel lines, the axis of the surgical tool will always pass through a fixed point, i.e., the RCM point. Due to the specially designed structure, the fixed point does not need to be physically belonging to the mechanism. The geometrical analysis method is employed to obtain the closed-form solution of the forward kinematics of the proposed mechanisms. Due to the high load capacity of parallel mechanism, the robots based on the proposed RCM mechanisms have promising applications as an external positioner to be used in robotic single-port surgeries.

Design and analysis of a novel metamorphic remote-centre-of-motion mechanism with parallelogram joints

Owing to their movements through a fixed point, remote-centre-of-motion (RCM) mechanisms can be widely used in applications such as surgery robotics, exoskeleton robots, haptic devices, pointing mechanisms. Most existing RCM mechanisms only have a constant mobility and RCM point. To adapt to more situations with variable motion requirements, a novel metamorphic RCM mechanism is proposed in this paper based on an analysis of the fundamental methods for metamorphic and RCM mechanisms. The mechanism is composed of two limbs with parallelogram joints and has three motion branches with different RCMs and two furcation points. The screw constraint multisets of the end-effector are utilized to analyse the mobilities and motions of reconfigurations by spanning different screw constraint systems. For the two furcation points and three motion branches, kinematic models and branch transformations are established. In addition, one actuation arrangement and its combined Jacobian are proposed and analysed. The workspace with no singularities except for the furcation points is shown at the end. The mechanism can move with three types of RCMs, which expands the design method of both RCM and metamorphic mechanisms.

Mechanism for tension adjustment in tendon driven remote center-of-motion mechanism for minimally invasive surgery

Tendon drive is used for transmission design in applications ranging from wearable rehabilitation and surgical robots to industrial robots. For their efficient operation, one of the principal design requirements is to have adequate tension in the tendon element. This paper introduces a novel mechanism for tension adjustment using a secondary cable-pulley arrangement via a lever mechanism. An adjustment in a tension spring applies a force in the tendon element meant for the transmission of remote centre-of-motion (RCM) mechanism for medical robotic application. Thereafter, the current work presents the kinematic and force analyses of the proposed concept along with a series of plots of various mechanism parameters. The variation of these parameters is in good agreement with the physical motion of the devised mechanism. As compared to the conventional methods of tension adjustment, the proposed concept is a better solution for problems that arise due to low manufacturing tolerances and the need for independent tension adjustment in a multi degrees-of-freedom tendon driven RCM mechanism. In the preferred embodiment, it is proposed to use cables (wire-ropes) as tendon elements to drive a mechanically constrained double-parallelogram-based RCM mechanism which is extensively used for Minimally Invasive Surgery. From this implementation, it is learnt that the presented mechanism can be implemented in several configurations. However, this paper presents the preferred embodiment only which meets the demand, of invariant tendon length, of the RCM mechanism under consideration. An initial prototype is made from acrylic sheets, PLA material, and standard elements (like bearings, pulleys, aluminum pins, 0.5 mm stainless-steel wire-rope, etc.) using laser micromachining and 3D printing.