Virtual Joint Research Articles

Effectiveness, Patient Satisfaction, and Cost Reduction of Virtual Joint Replacement Clinic Follow-Up of Hip and Knee Arthroplasty

BackgroundTotal hip and knee arthroplasties are increasingly performed operations, and routine follow-up places huge demands on orthopedic services. This study investigates the effectiveness, patients’ satisfaction, and cost reduction of Virtual Joint Replacement Clinic (VJRC) follow-up of total hip arthroplasty and total knee arthroplasty patients in a university hospital. VJRC is especially valuable when in-person appointments are not advised or feasible such as during the COVID-19 pandemic. MethodsA total of 1749 patients who were invited for VJRC follow-up for knee or hip arthroplasty from January 2017 to December 2018 were included in this retrospective study. Patients were referred to VJRC after their 6-week postoperative review. Routine VJRC postoperative review was undertaken at 1 and 7 years and then 3-yearly thereafter. We evaluated the VJRC patient response rate, acceptability, and outcome. Patient satisfaction was measured in a subgroup of patients using a satisfaction survey. VJRC costs were calculated compared to face-to-face follow-up. ResultsThe VJRC had a 92.05% overall response rate. Only 7.22% required further in-person appointments with only 3% being reviewed by an orthopedic consultant. VJRC resulted in an estimated saving of £42,644 per year at our institution. The patients’ satisfaction survey showed that 89.29% of the patients were either satisfied or very satisfied with VJRC follow-up. ConclusionVJRC follow-up for hip and knee arthroplasty patients is an effective alternative to in-person clinic assessment which is accepted by patients, has high patient satisfaction, and can reduce the cost to both health services and patients.

Hybrid compliance compensation for path accuracy enhancement in robot machining

Robot machining processes with high material removal rates lack of high path accuracy mainly due to the low stiffness of industrial robots. The low stiffness leads to process forces caused deviations of the tool center point (TCP) from the planned position of more than 1 mm in industrial applications. To enhance the path accuracy a novel hybrid compliance compensation is developed. It combines a force sensor and model based online compensation with forces of an offline simulation to instantly react to predictable high force changes e.g. at a milling cutter exit from the work piece. The method is applied to a KUKA KR 300 robot. A compliance model based on a forward kinematic with virtual joints is implemented on an external controller. Cartesian or axis specific compensation values are calculated and transferred to the robot via a control circuit. A compliance measurement method is developed and a force torque sensor is mounted to the flange of the robot. The system is validated in with Cartesian and axis specific compensation values as well as with and without pilot control.

Geometrical error improvement of Aramid honeycomb workpieces in robot-based triangular knife ultrasonic cutting process

Due to the notable advantages of ultrasonic-assisted machining, this technology is being more and more adopted in different manufacturing processes. Aramid honeycomb structures are among materials for which ultrasonic-assisted machining has become an interesting alternative thanks to its effect in reduction of machining forces and less micro imperfections. A considerable number of research works have addressed micro machining defeats in ultrasonic application such as dust generation and fiber delamination in Aramid honeycomb workpieces. However, in this study, a great attention is dedicated to the geometrical errors observed in the workpieces in cutting process of Aramid honeycomb structures using ultrasonic technology. The effect of different elements involved in robotic-based ultrasonic-assisted cutting process of Aramid honeycomb structures on these error types has been studied. To proceed this goal, a machining force estimation model is experimentally developed using the machining forces captured during the execution of several cutting tests. An on-site measurement process for measuring the geometrical errors in resulted workpieces is presented. The compliance behavior of robot-tool system is simulated using an extended virtual joint method (VJM) approach. In this approach, the machining tool is considered an additional joint-link system attached to the 6-revolute joint industrial system. Simulation results based on this method applied on the case study showed that the portion of contribution of industrial robotic arm to the compliant errors of process is negligible compared with the one of ultrasonic cutting knife. An offline compensation algorithm is proposed based on the developed machining force and tool compliance behavior models. Experimental results supported the efficiency of the proposed compensation method in reducing the geometrical error by up to 95% based on the machining features.

A Hybrid Active and Passive Cable-Driven Segmented Redundant Manipulator: Design, Kinematics, and Planning

With a light-slender and superior dexterous body, the cable-driven segmented redundant manipulators (CSRMs) are excellent candidates for operations in narrow confined space. However, their application is still largely limited due to their weak stiffness, low load capacity, and complex modeling and planning. In this article, we design a new type of CSRM with high stiffness and load capacity using hybrid active and passive cables, and propose a simplified kinematics modeling and configuration planning method. The manipulator is composed of three active-linkage segments and one active tool end-effector. Each active segment, driven by three active driving cables, has two degrees of freedom (DOFs). By utilizing the passive linkage cables, the segment can be fully constrained with high stiffness, and move with equal joint angles in nearly continuous shape. Based on such structural features, the kinematics equations about the active segment-joint variables (i.e., the equalpitch and yaw angles of the whole segment) are derived. The direct, inverse kinematics and differential kinematics are greatly simplified. To find suitable solutions under environment constraints, extended virtual joint (EVJ) is introduced for quick regional solutions searching and equivalent kinematic constraint analysis. Furthermore, a configuration planning method based on the simplified kinematics and equivalent EVJs is proposed for single obstacle avoidance and continuous narrow space crossing tasks. Finally, a prototype system is developed and typical experiments are performed. The results show the high linkage accuracy, improved stiffness, and load capacity of the developed CSRM and verify the adaptability of the proposed configuration planning method.

Deformation analysis of a novel 3-DOF parallel spindle head in gravitational field

A novel 2R1T (two rotational and one translational degrees-of-freedom) parallel spindle head (PSH) without parasitic motion is proposed which is based on the specific 3-UPU (P and U stand for prismatic joint and universal joint, respectively) parallel mechanism (PM). A modified virtual joint method (VJM) is proposed to solve the deformation analysis of this special PM whose action points of constraint forces are not directly on the solid structure of the mechanism in the gravitational field. Meanwhile, to obtain the relationship between the compliance of the prismatic joint and its length, a Response-Surface-based automation method is proposed with ANSYS workbench software. The workspace of the mechanism is drawn, and the deformation of the mechanism in the gravitational field is obtained within the sub-workspace of full-circle-rotation. The improvement scheme of reducing the deformation of the PSH is proposed.

Elastostatic Stiffness Analysis for the US/UPS Parallel Manipulators

The virtual joint method (VJM) cannot calculate the strain energy stored in each rod. In order to solve the problem, a modeling method of the elastostatic stiffness was investigated for the UP/UPS parallel manipulators (PMs), taking the example of the 6-SPS PM. The modeling method was based on screw theory, Castigliano’s theorem, and strain energy (where U, P, and S, respectively, denote universal, prismatic, and spherical joints). First, the actuator and constraint wrenches of the mechanism were obtained by screw theory. Second, compact limb stiffness matrices were obtained in terms of strain energy and Castigliano’s second theorem. Finally, analytic expressions for the overall stiffness matrix of the mechanism and the amplitudes of the actuator force were obtained by adopting the virtual work principle and the balance equation for the mobile platform. All relative errors between the results of the analytical model and the finite element model are below 2%, which validates the effectiveness of the elastostatic stiffness model. The virtual work index was adopted to evaluate the stiffness performance of the mechanism, and the results show that the stiffness is not only related to position and orientation but also closely related to the directions of external loads. It is also demonstrated that the method has general adaptability for the stiffness analysis for the US/UPS PMs, laying the foundation for further reasonable dynamic design and optimization of such manipulators.

Development of a Shared Controller for Obstacle Avoidance in a Teleoperation System

Several methods have been investigated to increase the efficiency of the operator in teleoperation, but remote devices still cannot be operated efficiently in the presence of the obstacle. In this study, a virtual link and virtual joints were created within the end-effector of the slave robot, and a shared controller was designed to implement an effective obstacle avoidance algorithm for the remote control system. Teleoperation experiments were conducted to verify the algorithm. Completion time and the NASA Task Load Index (NASA-TLX) were measured to evaluate the improvement of teleoperator work efficiency. When the obstacle avoidance algorithm was used, completion time decreased by 8.64%, and the average NASA-TLX decreased by 30.33 % as compared without the algorithm. Our method effectively improved completion time and NASA-TLX scores for both skilled and nonskilled human-operators.

Stiffness modeling of n(3RRlS) reconfigurable series-parallel manipulators by combining virtual joint method and matrix structural analysis

Stiffness is one of the critical performance indexes for robotic manipulators. In this study, a method for establishing the stiffness models of n(3RRlS) reconfigurable series-parallel manipulators (RSPMs) is proposed by combining the virtual joint method and matrix structural analysis. First, the constraint wrench system of the 3RRlS reconfigurable parallel manipulator (RPM) is obtained based on the reciprocal screw theory. Second, the stiffness matrices of the limbs along the axes of the constraint wrenches are analyzed using matrix structural analysis, and the overall stiffness matrix of the limbs is then assembled. Third, the stiffness matrices of the 3RRlS RPM and the n(3RRlS) RSPM are successively derived using the principle of virtual work. Finally, the theoretical and the finite-element-analysis deformations of the 3RRlS RPM and 3(3RRlS) RSPM are solved, and their average relative error is within 3.78%. It can be concluded that increasing actuation constraints can effectively improve the stiffness of manipulators in the directions of six degrees of freedom (DOFs) while increasing structural constraints can effectively improve the stiffness of manipulators in the directions of constrained DOFs.

Estimated forces and moments experienced by osseointegrated endoprostheses for lower extremity amputees

BackgroundPercutaneous osseointegrated (OI) docking of prosthetic limbs returns loading directly to the residual bone of individuals with amputations. Lower limb diaphyseal biomechanics have not been studied during the wide range of daily activities performed by individuals with lower extremity amputations; therefore, little is known about the loads experienced at the bone-endoprosthetic interface of a percutaneous OI device. Research questionDoes residual limb length and/or gender influence loading magnitudes in the diaphysis of the femur or tibia during daily activities? MethodsThis observational study used motion capture data from 40 non-amputee volunteers performing nine activities ranging from low to high demand, to virtually simulate residual limbs of amputees. To simulate diaphyseal bone loading in individuals with lower limb amputations, virtual joints were defined during post-processing at 25, 50, and 75 % of residual limb length of both the femur and the tibia, representing six clinically relevant residual limb lengths for OI device placement. Peak axial distractive and compressive forces, torsional moments, and bending moments were calculated for each activity. Comparisons were made between genders and between different levels of the simulated residual limb. ResultsFor simulated above and below knee amputations, short residual limbs showed the highest average bending, torsion, and axial distractive loads, while axial compressive loads were highest for long residual limbs. Absolute maxima for all subjects showed this same trend, except in below knee torsion, where 75 % residual tibia length showed the maximum. The highest demand activities yielding peaks in all directions were cutting with right leg planted, jump, run, and fall. SignificanceOverall, individuals with shorter residual limbs experienced higher diaphyseal forces. This should be taken into consideration during surgical implantation of percutaneous OI devices where residual limb length can potentially be shortened, and during rehabilitation of percutaneous OI patients.

Jacobian approach to the kinestatic analysis of a full vehicle model with application to cornering motion analysis

The Jacobian approach to the kinestatic analysis of a planar suspension mechanism has been previously presented. In this paper, the theory is extended to three-dimensional kinestatic analysis by developing a full kinematic model and viewing it as a spatial parallel mechanism. The full kinematic model consists of two pairs of the front (double wishbone) and rear (multi-link) suspension mechanisms together with a newly developed ground-wheel contact model. The motion of each wheel of four suspension mechanisms is represented by the corresponding instantaneous screw at any instant. A vehicle is considered to be a 6-degrees-of-freedom spatial parallel mechanism whose vehicle body is supported by four serial kinematic chains. Each kinematic chain consists of a virtual instantaneous screw joint and a kinematic pair representing ground-wheel contact model. The kinestatic equation of the 6-degrees-of-freedom spatial parallel mechanism is derived in terms of the Jacobian. As an important application, a cornering motion of a vehicle is analysed under the assumption of steady-state cornering. A numerical example is presented to illustrate how to determine the optimal locations of strut springs for the least roll angle in cornering motion using the proposed method.

The learning curves of a validated virtual reality hip arthroscopy simulator

IntroductionDecreases in trainees’ working hours, coupled with evidence of worse outcomes when hip arthroscopies are performed by inexperienced surgeons, mandate an additional means of training. Though virtual reality simulation has been adopted by other surgical specialities, its slow uptake in arthroscopic training is due to a lack of evidence as to its benefits. These benefits can be demonstrated through learning curves associated with simulator training—with practice reflecting increases in validated performance metrics.MethodsTwenty-five medical students with no previous experience of hip arthroscopy completed seven weekly simulated arthroscopies of a healthy virtual hip joint using a 70° arthroscope in the supine position. Twelve targets were visualised within the central compartment, six via the anterior portal, three via the anterolateral portal and three via the posterolateral portal. Task duration, number of collisions (bone and soft-tissue), and distance travelled by arthroscope were measured by the simulator for every session of each student.ResultsLearning curves were demonstrated by the students, with improvements in time taken, number of collisions (bone and soft-tissue), collision length and efficiency of movement (all p < 0.01). Improvements in time taken, efficiency of movement and number of collisions with soft-tissue were first seen in session 3 and improvements in all other parameters were seen in session 4. No differences were found after session 5 for time taken and length of soft-tissue collision. No differences in number of collisions (bone and soft-tissue), length of collisions with bone, and efficiency of movement were found after session 6.ConclusionsThe results of this study demonstrate learning curves for a hip arthroscopy simulator, with significant improvements seen after three sessions. All performance metrics were found to improved, demonstrating sufficient visuo-haptic consistency within the virtual environment, enabling individuals to develop basic arthroscopic skills.

Dynamic analysis of the arbitrary position of a particle robot around an inclined pipe based on virtual joints

During the movement of a robot on the outside of a pipe, it either exhibits linear or rotating motion along the axis of the pipe. In this process, not only is there conversion between kinetic energy, potential energy, resistance power consumption, and external work, but there are also complex mechanical relationships that occur. To solve the dynamic problems of the out-pipe climbing robot in space, the axis and diameter of the pipe were simplified to the virtual joints of a robot with zero mass, and the virtual dynamic model of the robot in space has been established. According to the vector of the arbitrary position of a particle robot around an inclined pipe, combined with the improved Lagrange–Newton–Euler method, the system’s dynamic equation that includes friction has been established, and the required driving force for an arbitrary position of the robot in the process of circling an inclined pipe has been obtained.

Topology optimization method and lightweight design of anthropomorphic manipulator

The topology optimization method is adopted to realize the weight reduction of the mechanical arm under the rigidity condition. The typical configuration and load conditions of the manipulator are analyzed. The stiffness mass model of the part is established by the finite element analysis method, and the topology optimization of the part is carried out. On this basis, the optimization of the manipulator system is completed. The optimized art quality is reduced by 6.2% compared with the original model, and the stiffness meets the standard requirements. The method of combining virtual joint method with working space of the manipulator is proposed. The amount of end deformation after optimization of the manipulator is analyzed. The maximum deformation is 0.27mm, which meets the requirements. The optimization process provides a reference for the selection of the drive joint parts of the mechanical arm. According to this, the physical design of the mechanical arm is completed and the load test is carried out. The experiment shows that the mechanical arm can still achieve rapid response under the condition of a 2kg end load.

Virtual-joint based motion similarity criteria for human–robot kinematics mapping

Motion mapping is an important part in human–robot cooperation. In this paper, a novel concept of virtual-joint based similarity criteria is proposed for flexible and efficient kinematics mapping between dissimilar embodiments, including different degrees of freedom (DOFs), different body morphology, and so on. Virtual joints are defined respectively in both the demonstrator and the imitator, with the same number. In virtual joints, the neglecting, re-ordering and repetitive usage of DOFs could be realized through the virtual decomposing matrices. Each virtual joint of the demonstrator and the corresponding one of the imitator formed a virtual joint pair. The Total Metric of Motion Similarity is the weighted sum of the metrics defined for each virtual joint pairs. Unlike traditional joint-space or Cartesian-space based metrics describing motion similarity solely at the DOF kinematic mode level, virtual-joint-based metrics can be adopted to describe different aspects of motion similarity between dissimilar agents, both in joint space and in Cartesian space. Two experiments are conducted to illustrate the effectiveness of the proposed approach.

МОДЕЛЬ ДЛЯ ТЕПЛОВОГО РАСЧЁТА ФОРМИРОВАНИЯ ВИРТУАЛЬНОГО СВАРНОГО ШВА

МОДЕЛЬ ДЛЯ ТЕПЛОВОГО РАСЧЁТА ФОРМИРОВАНИЯ ВИРТУАЛЬНОГО СВАРНОГО ШВА

Fourier-shape-based reconstruction of rock joint profile with realistic unevenness and waviness features

Rock joint shape characteristics, waviness and unevenness play essential but distinct roles in shear mechanism of rock joints. This study presents a novel method to generate virtual rock joint profiles with realistic waviness and unevenness features. Firstly, joint profiles are obtained by 3D laser scanning device. Secondly, quantification of waviness and unevenness is conducted by traditional method, including digital filtering technique and roughness parameter RL. Thirdly, the discrete Fourier transform (DFT) method is employed to analyze the joint outlines. Two representative Fourier shape descriptors (D3, D8) for characterization of waviness and unevenness are suggested. Then, the inverse discrete Fourier transform (IDFT) is adopted to reconstruct the joint profiles with random values of phase angles but prescribed amplitudes controlled by D3 and D8. The traditional method is then applied to the reconstructed joint profiles to examine statistically the relationships between D3 and D8 and parameters RL of waviness and unevenness, respectively. The results show that larger D8 tends to result in larger waviness while higher D3 tends to increase unevenness. Reference charts for estimation of waviness and unevenness with different pairs of D3 and D8 are also provided to facilitate implementation of random joint reconstruction.

Time efficient stiffness model computation for a parallel haptic mechanism via the virtual joint method

Haptic devices are used for displaying a range of mechanical impedance values to the user. This impedance is regulated by a real-time control loop depending on the position information of the end-effector, which is usually acquired indirectly by using forward kinematics equations. Nevertheless, the kinematic model is insufficient to obtain accurate values if there are non-negligible compliant displacements. This gives a strong motivation for implementing a real-time stiffness model in the haptic control loop for improving its accuracy. Additionally, stiffness performance indices can be used at the design stage for enhancing the haptic devices impedance range within optimal design procedures. Fast solutions of a stiffness model are required for a real-time control as well as for decreasing the optimization time during a design process with a trade-off between accuracy and computational costs. In this study, we propose a computation time-efficient stiffness analysis of a parallel haptic device mechanism. The accuracy and computational costs of the proposed model are calculated and compared with a model that is obtained via a finite element method to demonstrate the effectiveness of the proposed approach with the desired real-time and accuracy performance.

Service Characteristics-Oriented Joint ACB, Cell Selection, and Resource Allocation Scheme for Heterogeneous M2M Communication Networks

Heterogeneous machine-to-machine communication networks (HMCNs) are expected to provide ubiquitous connectivity for machine type communication devices (MTCDs) with reduced human intervention. Although various types of services will be supported for MTCDs, diverse quality of service requirements and network characteristics pose challenges and difficulties to the resource allocation, cell selection, and random access schemes of the HMCNs. In this paper, we propose a joint access class barring (ACB), cell selection, and resource allocation algorithm for HMCNs. To achieve efficient utilization of the resource blocks (RBs) in heterogeneous cells, we first propose a virtual clustering-based joint ACB and RB allocation sub-algorithm. Partitioning the MTCDs into virtual clusters, we formulate the joint ACB and RB allocation problem of the virtual clusters as RB utilization maximization problem. Through solving the optimization problem, we obtain the optimal ACB factor and RB allocation strategy. Given the optimal strategy, we then formulate the joint cell selection and power allocation problem of the MTCDs as a utility function maximization problem. As the formulated problem is a mixed nonlinear optimization problem, which cannot be solved conveniently, we transform the problem using relaxation method and solve it through applying an iterative algorithm and the Lagrange dual method. Simulation results demonstrate the effectiveness of the proposed algorithm.

A novel parallel recursive dynamics modeling method for robot with flexible bar-groups

Based on Hamilton equation of motion and Lagrange principle, this paper proposes a novel parallel recursive dynamics modeling method for robot with flexible bar-groups that comprise flexible link, flexible joint and joint clearance. Using the virtual joint velocity, constraint force impulse and derivative of canonical momentum, the dynamics model of flexible link is established, and the dynamics model of flexible joint is built by the generalized force and energy of flexible joint. Then, based on kinematics constraints and dynamics constraints, the general comprehensive dynamics model of robot with flexible bar-groups is obtained. Finally, the proposed dynamics modeling method is applied to Delta parallel robot and KUKA serial robot, compared with the existing dynamics modeling methods by experiments, our approach is not only closer to the actual situation, but also has higher algorithm efficiency and better universality, which can lay foundation for the prediction of dynamic characteristics, and achieve the accurate and efficient control for different types of robots.

Navigation Simulation of a Mecanum Wheel Mobile Robot Based on an Improved A* Algorithm in Unity3D.

Computer simulation is an effective means for the research of robot navigation algorithms. In order to implement real-time, three-dimensional, and visual navigation algorithm simulation, a method of algorithm simulation based on secondary development of Unity3D is proposed. With this method, a virtual robot prototype can be created quickly with the imported 3D robot model, virtual joints, and virtual sensors, and then the navigation simulation can be carried out using the virtual prototype with the algorithm script in the virtual environment. Firstly, the scripts of the virtual revolute joint, virtual LiDAR sensors, and terrain environment are written. Secondly, the A* algorithm is improved for navigation in unknown 3D space. Thirdly, taking the Mecanum wheel mobile robot as an example, the 3D robot model is imported into Unity3D, and the virtual joint, sensor, and navigation algorithm scripts are added to the model. Then, the navigation is simulated in static and dynamic environments using a virtual prototype. Finally, the navigation tests of the physical robot are carried out in the physical environment, and the test trajectory is compared with the simulation trajectory. The simulation and test results validate the algorithm simulation method based on the redevelopment of Unity3d, showing that it is feasible, efficient, and flexible.