Wave-shaped Notched Compliant Joint with High Rigidity

Notched compliant joints (NCJs) have been widely used in orthopedic surgeries requiring large curvatures for a minimally invasive approach to lesions and high rigidity for cutting hard tissues. With current NCJ designs, there is a trade-off between maximizing rigidity and maximizing curvature for a specified constrained size. Considering notch geometry, larger sizes of notch gaps lead to greater curvatures, however, smaller spacing between notches decreases rigidity. Herein, we propose an NCJ with a novel notch shape, such that the gap of the spacer can be increased without changing that of the notch. Furthermore, we determined the best design parameters for achieving the maximum rigidity for a given driving force. The higher rigidity of the proposed NCJ compared with that of general NCJs is shown through a simulation and experiments. The difference in rigidities between the proposed and general NCJs was 66% with the p-value of $5.68 \times {10}^{ - 9}$ in a 95% confidence interval which was found to be a statistically significant improvement. In a cutting test, while keeping the curvature, the proposed NCJ increased the cutting amount compared with general NCJs. We verified that the proposed NCJ can achieve both high rigidity and large curvature. The main feature of this study is the development of an NCJ in which both the gap of the spacer and the gap of the notch can be independently changed without affecting each other. The proposed NCJ achieves improved rigidity without loss of curvature. IEEEFALS

Analysis of Twist Deformation in Wire-driven Continuum Surgical Robot

Wire-driven continuum surgical robots are attracting significant interest in minimally invasive surgeries owing to their high dexterity level and miniaturization. However, twist deformation due to the external force at the end effector decreases the accuracy and controllability of these robots. In this study, we analyze the two factors responsible for twist deformation and propose models incorporating these factors. In our analyses, we first consider twist deformation due to the elastic deformation of the wire; when a tensioned wire is subjected to normal force, a sag effect occurs, which results in twist deformation in the robot. We analyze this sag effect statically considering the material properties of the wire. We also analyze the twist deformation due to the clearance between the wire and hole boundary in the spacer of the robot. Clearance is required in a wire-driven continuum robot to realize bending motion; however, this is considered one of the main causes of twist deformation and is referred to as the clearance effect. Subsequently, we propose sag and clearance effect models that quantitatively predict the twist deformation. The results of the experiments conducted to verify the accuracy of the proposed models, including a payload test using a conventional continuum robot comprising spherical joints, indicate that the accuracy of the proposed models is 95%. © 2019, ICROS, KIEE and Springer.FALS

Vision Guided Robotic System for Bone Drilling Based on Rolling Friction

Drilling procedures to the bone are frequently conducted with CT in the various surgical fields. The proposed vision guided robotic system provides orientation alignment of the drill-tip and automatic drilling to the target. The feasibility of the proposed robotic system was demonstrated by ex-vivo drilling tests on swine femur

Compact Bone Surgery Robot With a High-Resolution and High-Rigidity Remote Center of Motion Mechanism

Objective: Two important and difficult tasks during a bone drilling procedure are guiding the orientation of the drilling axis toward the target and maintaining the orientation against the drilling force. To accomplish these tasks, a remote center of motion (RCM) mechanism is adopted to align the orientation of the drilling axis without changing the entry point. However, existing RCM mechanisms do not provide sufficient resolution and rigidity to address hard tissue cases. Methods: We propose a new type of RCM mechanism that uses two sets of linear actuators and a gearless-arc guide to have a high resolution and rigidity. In addition, we designed a single motor-based drilling mechanism based on rolling friction. To achieve automatic control of the guiding and drilling process, we incorporated a computer-tomography-based navigation system that was equipped with an optical tracking system. Results: The effectiveness of the integrated robotic system was demonstrated through a series of experiments and ex vivo drilling tests on swine femurs. The proposed robotic system withstood a maximum external force of 51 N to maintain the joint angle, and the average drilling error was less than 1.2 mm. Conclusion: This study confirms the feasibility of the proposed bone drilling robotic system with a high-resolution and high-rigidity RCM mechanism. Significance: This drilling system is the first successful trial based on an RCM mechanism and a single motor-based drilling mechanism, reducing the footprint and required motors with respect to previous bone surgical robots. © 1964-2012 IEEE.1

Simultaneous Optimization of Patient-Image Registration and Hand-Eye Calibration for Accurate Augmented Reality in Surgery

Objective: Augmented reality (AR) navigation using a position sensor in endoscopic surgeries relies on the quality of patient-image registration and hand-eye calibration. Conventional methods collect the necessary data to compute two output transformation matrices separately. However, the AR display setting during surgery generally differs from that during preoperative processes. Although conventional methods can identify optimal solutions under initial conditions, AR display errors are unavoidable during surgery owing to the inherent computational complexity of AR processes, such as error accumulation over successive matrix multiplications, and tracking errors of position sensor. Methods: We propose the simultaneous optimization of patient-image registration and hand-eye calibration in an AR environment before surgery. The relationship between the endoscope and a virtual object to overlay is first calculated using an endoscopic image, which also functions as a reference during optimization. After including the tracking information from the position sensor, patient-image registration and hand-eye calibration are optimized in terms of least-squares. Results: Experiments with synthetic data verify that the proposed method is less sensitive to computation and tracking errors. A phantom experiment with a position sensor is also conducted. The accuracy of the proposed method is significantly higher than that of the conventional method. Conclusion: The AR accuracy of the proposed method is compared with those of the conventional ones, and the superiority of the proposed method is verified. Significance: This study demonstrates that the proposed method exhibits substantial potential for improving AR navigation accuracy. © 1964-2012 IEEE.1

Segment2Regress: Monocular 3D Vehicle Localization in Two Stages

High-quality depth information is required to perform 3D vehicle detection, consequently, there exists a large performance gap between camera and LiDAR-based approaches. In this paper, our monocular camera-based 3D vehicle localization method alleviates the dependency on high-quality depth maps by taking advantage of the commonly accepted assumption that the observed vehicles lie on the road surface. We propose a two-stage approach that consists of a segment network and a regression network, called Segment2Regress. For a given single RGB image and a prior 2D object detection bounding box, the two stages are as follows: 1) The segment network activates the pixels under the vehicle (modeled as four line segments and a quadrilateral representing the area beneath the vehicle projected on the image coordinate). These segments are trained to lie on the road plane such that our network does not require full depth estimation. Instead, the depth is directly approximated from the known ground plane parameters. 2) The regression network takes the segments fused with the plane depth to predict the 3D location of a car at the ground level. To stabilize the regression, we introduce a coupling loss that enforces structural constraints. The efficiency, accuracy, and robustness of the proposed technique are highlighted through a series of experiments and ablation assessments. These tests are conducted on the KITTI bird???s eye view dataset where Segment2Regress demonstrates state-of-the-art performance. Further results are available at https://github.com/LifeBeyondExpectations/Segment2Regres

Wire-driven flexible manipulator with constrained spherical joints for minimally invasive surgery

Purpose: One of the main factors that affect the rigidity of flexible robots is the twist deformation because of the external force exerted on the end effector. Another important factor that affects accuracy is the fact that such robots do not have a constant curvature. The conventional kinematic model assumes that the curvature is constant; however, in reality, it is not. To improve the rigidity and accuracy of flexible robots used in minimally invasive surgery via preventing the twist deformation while ensuring a constant curvature, we propose a novel flexible manipulator with ball-constrained spherical (BCS) joints and a spring. Methods: The BCS joints are used to prevent the twist deformation in the flexible robot. The joints have two degrees of freedom (DOFs), which limit the rotation about the axial direction. The rotation is limited because the ball that is inserted into a BCS joint can move only along the ball guide. To obtain a constant curvature, springs are installed among the BCS joints. The springs receive the uniform compression force generated among the joints, thus achieving a constant curvature. The proposed BCS joint is designed based on the diameter of the forceps, desired workspace, and desired bending angle. Results: To evaluate the proposed mechanism, three experiments were performed using a 20-mm-diameter prototype consisting of 13 BCS joints with a two-DOF motion. The experimental results showed that the prototype can realize a constant curvature with a mean error of 0.21°, which can support up to 5 N with no apparent twist deformation. Conclusions: We developed a flexible manipulator with BCS joints for minimally invasive surgery. The proposed mechanism is anticipated to help prevent the twist deformation of the robot and realize a constant curvature. Accordingly, it is expected that rigidity is improved to ensure accuracy. © 2019, CARS.1

An all-joint-control master device for single-port laparoscopic surgery robots

Purpose: Robots for single-port laparoscopic surgery (SPLS) typically have all of their joints located inside abdomen during surgery, whereas with the da Vinci system, only the tip part of the robot arm is inserted and manipulated. A typical master device that controls only the tip with six degrees of freedom (DOFs) is not suitable for use with SPLS robots because of safety concerns. Methods: We designed an ergonomic six-DOF master device that can control all of the joints of an SPLS robot. We matched each joint of the master, the slave, and the human arm to decouple all-joint motions of the slave robot. Counterbalance masses were used to reduce operator fatigue. Mapping factors were determined based on kinematic analysis and were used to achieve all-joint control with minimal error at the tip of the slave robot. Results: The proposed master device has two noteworthy features: efficient joint matching to the human arm to decouple each joint motion of the slave robot and accurate mapping factors, which can minimize the trajectory error of the tips between the master and the slave. Conclusions: We confirmed that the operator can manipulate the slave robot intuitively with the master device and that both tips have similar trajectories with minimal error. © 2016, CARS.