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Lumbar spine injuries caused by repetitive lifting rank as the most prevalent workplace injury in the United States. While these injuries are caused by both symmetric and asymmetric lifting, asymmetric is often more damaging. Many back devices do not address asymmetry, so we present a new system called the Asymmetric Back Exosuit (ABX). The ABX addresses this important gap through unique design geometry and active cable-driven actuation. The suit allows the user to move in a wide range of lumbar trajectories while the “X” pattern cable routing allows variable assistance application for these trajectories. We also conducted a biomechanical analysis in OpenSim to map assistive cable force to effective lumbar torque assistance for a given trajectory, allowing for intuitive controller design in the lumbar joint space over the complex kinematic chain for varying lifting techniques. Human subject experiments illustrated that the ABX reduced lumbar erector spinae muscle activation during symmetric and asymmetric lifting by an average of 37.8% and 16.0%, respectively, compared to lifting without the exosuit. This result indicates the potential for our device to reduce lumbar injury risk.

Anytime a robot manipulator is controlled via visual feedback, the transformation between the robot and camera frame must be known. However, in the case where cameras can only capture a portion of the robot manipulator in order to better perceive the environment being interacted with, there is greater sensitivity to errors in calibration of the base-to-camera transform. A secondary source of uncertainty during robotic control are inaccuracies in joint angle measurements which can be caused by biases in positioning and complex transmission effects such as backlash and cable stretch. In this work, we bring together these two sets of unknown parameters into a unified problem formulation when the kinematic chain is partially visible in the camera view. We prove that these parameters are non-identifiable implying that explicit estimation of them is infeasible. To overcome this, we derive a smaller set of parameters we call Lumped Error since it lumps together the errors of calibration and joint angle measurements. A particle filter method is presented and tested in simulation and on two real world robots to estimate the Lumped Error and show the efficiency of this parameter reduction., 18 pages, 13 figures, and 3 tables

Context: Volleyball players have shown to be at an increased risk of developing scapular dyskinesis. The kinetic chain exercise approach has gained a lot of attention because of its claims to provide an improved motor control and scapular kinematics. A form of cross exercise, known as mirror therapy, may enhance the effects of a kinetic chain exercise approach in throwing performance. Objective: To examine the effects of mirror cross exercise (MCE), based on a kinetic chain exercise approach in the throwing performance of volleyball athletes with scapular dyskinesis. Design: Randomized controlled trial. Setting: Biomechanics laboratory. Methods: 39 volleyball players with scapular dyskinesis were randomly allocated into 3 groups. The first group completed a 6-week kinetic chain approach (KCA group), the second group completed a kinetic chain exercise approach program in addition to MCE group, and the control group followed only their regular training program. Before and after delivering both interventions, throwing accuracy, speed, and force were determined while measuring the ground reaction forces of the drive leg during throwing. Two-way mixed analysis of variance investigated the effects of intervention and time and their interaction. Results: The results showed intervention × time statistically significant interactions for throwing accuracy, speed, and force for the MCE and the KCA groups. Over the 6-week training period, the MCE and the KCA groups showed significant improvements in throwing accuracy (P P P > .05). Throwing force increased significantly in the MCE group (P = .01). Between-group comparison showed statistically significant improvements in the throwing accuracy for the MCE and KCA groups against the control group (P Conclusions: This study suggests that the addition of MCE in a KCA program enhances energy transfer throughout the distal and proximal segments, thus improving kinetic chain recruitment and potentially preventing shoulder pathology.

Cerebral palsy is one of the main factors leading to children’s disability. A large number of such children have hand motor dysfunction, such as limited range of motion, abnormal gestures, etc. Our goal is to design a prototype of wearable gesture training equipment for such children. For this purpose, this paper presents the development of a wireless smart glove to facilitate the accurate measurement of finger movement through the integration of multiple IMU sensors. Commercially available gaming gloves are not fitted with sufficient sensors for this particular application and most of them can only provide one degree of freedom for finger flexion and extension. In this paper, a data glove integrated with nine degree of freedom inertial sensors in conjunction with complex multi-sensor data fusion is developed. In our method, a single/dual state measurement update switching extended Kalman filter is proposed to estimate the spatial attitude of each finger segment. Through traversing the kinematic chain, a tree type hand dynamic model based on joint constraints is established to realize the real-time gesture tracking. Furthermore, a visual interface is developed to display the tracking effect of gestures, and the reliability of our algorithm is verified by optical contrast experiments, the repeatability of joint angle is also evaluated by kinematic analysis. In general, all the experimental results demonstrated that our proposed framework can accurately track the 3-D hand motion. This glove will help quantify joint stiffness and monitor patient progression during the rehabilitation training process.

Background: Over the past decade, research has attempted to elucidate the cause of throwing-related injuries in the baseball athlete. However, when considering the entire kinetic chain, full body mechanics, and pitching cycle sequencing, there are hundreds of variables that could influence throwing arm health, and there is a lack of quality investigations evaluating the relationship and influence of multiple variables on arm stress. Purpose: To identify which variables have the most influence on elbow valgus torque and shoulder distraction force using a statistical model and a machine learning approach. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A retrospective review was performed on baseball pitchers who underwent biomechanical evaluation at the university biomechanics laboratory. Regression models and 4 machine learning models were created for both elbow valgus torque and shoulder distraction force. All models utilized the same predictor variables, which included pitch velocity and 17 pitching mechanics. Results: The analysis included a total of 168 high school and collegiate pitchers with a mean age of 16.7 years (SD, 3.2 years) and BMI of 24.4 (SD, 1.2). For both elbow valgus torque and shoulder distraction force, the gradient boosting machine models demonstrated the smallest root mean square errors and the most precise calibrations compared with all other models. The gradient boosting model for elbow valgus torque reported the highest influence for pitch velocity (relative influence, 28.4), with 5 mechanical variables also having significant influence. The gradient boosting model for shoulder distraction force reported the highest influence for pitch velocity (relative influence, 20.4), with 6 mechanical variables also having significant influence. Conclusion: The gradient boosting machine learning model demonstrated the best overall predictive performance for both elbow valgus torque and shoulder distraction force. Pitch velocity was the most influential variable in both models. However, both models also revealed that pitching mechanics, including maximum humeral rotation velocity, shoulder abduction at foot strike, and maximum shoulder external rotation, significantly influenced both elbow and shoulder stress. Clinical Relevance: The results of this study can be used to inform players, coaches, and clinicians on specific mechanical variables that may be optimized to mitigate elbow or shoulder stress that could lead to throwing-related injury.

A method to compensate the influence of geometric deviations on tool center point (TCP) for a multi-tasking machine tool is proposed in this paper. Some methods to compensate geometric deviations of a rotary axis in five-axis machining centers have been proposed. However, due to the special topological structure of multi-tasking machine tools, the identification and compensation methods for geometric deviations are different from those of the five-axis machining centers, which have been seldom researched until now. In this paper, the main attention is paid to analyze the eccentricities of the trajectories measured by a ball bar under simultaneous three-axis motions and to reduce the influence of the identified geometric deviations on the position error of TCP by the compensation method. It is divided into two sequential subtasks. At first, the geometric deviations are identified by using the eccentricities of measured trajectories. A simple and practical measuring procedure is proposed to identify geometric deviations of rotary axes existing in a multi-tasking machine tool. For the second step, a method is proposed by modifying the original NC code according to the kinematic chain model of the targeted machine tool to compensate the influence of the existing geometric deviations on TCP. An experiment is conducted on a multi-tasking machine tool with a swivel tool spindle head in the horizontal position. The repeatability of the measured eccentricities based on three experimental results is also investigated to reduce the influence of measuring error on the identified results. As a result, the corresponding values of geometric deviations after the compensation are less than 2.2 arcseconds or 2.4 μm. It is concluded that the influence of geometric deviations on TCP is compensated effectively, and the position error of TCP is reduced significantly.

Background and Study Aim. Students are often injured while playing sports. The main condition for preventing injuries is the correct technique of movements. In the literature, rock climbing has not been analyzed in terms of prevention of student injuries. Therefore, the development of programs to prevent injuries of students-rock climbers is relevant. Aim: to determine the impact of the use of exercises in a closed kinematic chain on the technical skill and the number of injuries to the elbows of student-rock climbers based on the analysis of the one-arm hang technique. Material and methods. First, to substantiate the correct technique in rock climbing, the technique of performing one-arm hang was analyzed by 20 leading male climbers of Ukraine and 20 students - novice male climbers. Then a randomized control study was conducted. The participants in the randomized control study were 40 male students-climbers in the intervention group and 44 male students-climbers in the control group aged 18-19 years. The one-arm hang technique was determined based on the angles between the shoulder and the collarbone during the movement. The experiment lasted 1 year. At the beginning and at the end of the experiment, the analysis of the one-arm hang technique was carried out. The number of elbow injuries in both groups was also recorded. Results. The main parameters of the one-arm hang technique for qualified and unskilled climbers have been substantiated. For qualified climbers, one-arm hang involves the muscles of the shoulder girdle, torso, and legs. In unskilled climbers, one-arm hang is provided only by the muscles of the arm. In a control randomized study, there was a significant improvement in the results of biomechanical analysis of the hang technique in athletes in the intervention group (p, Обґрунтування і мета. Студенти при заняттях спортом часто отримують травми. Основна умова профілактики травм - правильна техніка рухів. В літературі не аналізувалися скелелазіння з точки зору профілактики травм студентів. Тому розробка програм запобігання травм студентів - скелелазів є актуальною. Мета: визначити вплив застосування вправ в закритих кінематичних ланцюгах на технічну майстерність і кількість травм ліктів студентів-скелелазів на основі аналізу техніки виконання вису на одній руці. Матеріал і методи. Спочатку для обґрунтування правильної техніки в скелелазінні була проаналізована техніка виконання вису на одній руці 20-ти провідних скелелазів України та 20-ти студентів - початківців скелелазів чоловічої статі. Потім було проведено рандомізоване контрольне дослідження. Учасниками рандомізованого контрольного дослідження були 40 студентів-скелелазів групи втручання і 44 студенти контрольної групи чоловічої статі у віці 18-19 років. Техніка вису на одній руці визначалася на основі величини кутів між плечем і ключицею при виконанні руху. Експеримент тривав 1 рік. На початку і в кінці експерименту було проведено аналіз техніки виконання вису на одній руці. Також фіксувалася кількість травм ліктів в обох групах. Результати. Обґрунтовано основні параметри техніки вису на одній руці у кваліфікованих і некваліфікованих скелелазів. У кваліфікованих скелелазів при виконанні вису на одній руці включаються м'язи плечового пояса, тулуба, ніг. У некваліфікованих скелелазів вис на одній руці забезпечується тільки м'язами руки. У контрольному рандомізованому дослідженні спостерігалося достовірне поліпшення результатів біомеханічного аналізу техніки вису у спортсменів групи втручання (p

Background: Inefficient energy transfer from the pelvis and trunk has been shown to increase compensation at the level of the shoulder. Kinetic chain sequencing of the core segments is underexamined in professional baseball pitchers, especially as it relates to changes in upper extremity kinetics. Purpose: To evaluate elbow and shoulder kinetics in a cohort of professional pitchers differentiated by instances of discordant pelvic to upper torso sequencing during the pitch. Study Design: Descriptive laboratory study. Methods: 285 professional baseball pitchers were evaluated using 3D motion capture (480 Hz). Pitchers were divided into “chronological” and “discordant” groups based on whether maximum pelvic rotation velocity occurred before (chronological) or after (discordant) maximum upper torso rotation velocity during the pitch motion. Pelvic, upper torso, and shoulder kinematic parameters, shoulder distraction force, shoulder internal rotation torque, and pitch efficiency (PE) were compared between groups. Results: Pitchers with discordant torso sequencing (n = 30; 110 pitches) had greater shoulder horizontal adduction at maximum external rotation (mean difference, 3.6°; 95% CI, −5.2° to −2.0°; t = −4.5; P < .001) and greater maximum shoulder external rotation (mean difference, 3.7°; 95% CI, 5.7° to 1.5°; t = −3.5; P < .001) than chronological pitchers (n = 255; 2974 pitches). PE did not differ between groups ( P = .856), whereas ball velocity was significantly faster in the discordant group (mean difference, 0.6 m/s; 95% CI, −1.1 to −0.3 m/s; t = −3.3; P = .0012). Chronological pitchers had significantly reduced shoulder distraction force (mean difference, −4.7% body weight (BW); 95% CI, −7.9% to −1.5% BW; t = −2.9; P = .004) with no difference in shoulder internal rotation torque ( P = .160). These kinematic and kinetic differences were not observed when accounting for interpitcher variability. Conclusion: Between pitchers, those who had a discordant pelvic to upper torso sequence experienced significantly greater shoulder distraction forces, potentially compensating by increasing maximum shoulder external rotation and horizontal abduction. Achieving maximal pelvic rotation velocity before maximal rotation velocity may be advantageous in preventing compensation at the upper extremity and excessive throwing arm loading. Clinical Relevance: Identifying risk factors for increased upper extremity forces has potential implications in injury prevention. Specifically, mitigating shoulder distraction forces may be beneficial in reducing risk of injury.

Background: The optoelectronic camera source and data interpolation serve as the foundation for navigational integrity in the robotic-assisted surgical platform. The objective of the current systematic review serves to provide a basis for the numerical disparity that exists when comparing the intrinsic accuracy of optoelectronic cameras: accuracy observed in the laboratory setting versus accuracy in the clinical operative environment. It is postulated that there exists a greater number of connections in the optoelectronic kinematic chain when analyzing the clinical operative environment to the laboratory setting. This increase in data interpolation, coupled with intraoperative workflow challenges, reduces the degree of accuracy based on surgical application and to that observed in controlled musculoskeletal kinematic laboratory investigations. Methods: Review of the PubMed and Cochrane Library research databases was performed. The exhaustive literature compilation obtained was then vetted to reduce redundancies and categorized into topics of intrinsic optoelectronic accuracy, registration accuracy, musculoskeletal kinematic platforms, and clinical operative platforms. Results: A total of 147 references make up the basis for the current analysis. Regardless of application, the common denominators affecting overall optoelectronic accuracy are intrinsic accuracy, registration accuracy, and application accuracy. Intrinsic accuracy of optoelectronic tracking equaled or was less than 0.1 mm of translation and 0.1° of rotation per fiducial. Controlled laboratory platforms reported 0.1 to 0.5 mm of translation and 0.1°–1.0° of rotation per array. There is a huge falloff in clinical applications: accuracy in robotic-assisted spinal surgery reported 1.5 to 6.0 mm of translation and 1.5° to 5.0° of rotation when comparing planned to final implant position. Total Joint Robotics and da Vinci urologic robotics computed accuracy, as predicted, lies between these two extremes—1.02 mm for da Vinci and 2 mm for MAKO. Conclusions: Navigational integrity and maintenance of fidelity of optoelectronic data is the cornerstone of robotic-assisted spinal surgery. Transitioning from controlled laboratory to clinical operative environments requires an increased number of steps in the optoelectronic kinematic chain and error potential. Diligence in planning, fiducial positioning, system registration, and intraoperative workflow have the potential to improve accuracy and decrease disparity between planned and final implant position. The key determining factors limiting navigation resolution accuracy are highlighted by this Cochrane research analysis.

The aims of this study were to i) evaluate proximal-to-distal sequencing (PDS) in pianists’ attack and release movements during pressed-staccato keystrokes, and ii) investigate if trunk motion facilitates PDS of upper-limb movements. Nine expert pianists performed a series of loud pressed-staccato keystrokes. Kinematic data was recorded with a 3 D motion capture system. PDS was assessed by comparing temporal organization of peak velocities from the pelvis to the wrist. Evidence of PDS was found across the kinematic chain. Pianists’ use of PDS differed mainly between scapula and shoulder movements. Trunk motion facilitated PDS by increasing anticipatory shoulder movements and by preceding shoulder-girdle attack and release movements. Implications might relate to research on performance optimization and injury prevention strategies.

Geometric errors are important factors that affect the accuracy of multi-axis CNC machine tools. In this paper, three aspects of research work are carried out. First, two kinds of error modeling methods are proposed, i.e., tool tip coordinates error modeling (TTC) and kinematic chain transmission error modeling (KCT). This work resolves the theoretical confusion existing in the error modeling process in the past. Second, left matrix multiplication and right matrix multiplication have different meanings for geometric error modeling; this paper makes a detailed analysis and summarizes four identification algorithms for geometric errors based on the above theory. Third, a new R-test device is developed. For the traditional commercial R-test, it is usually difficult to adjust the position and orientation, so it is hard to directly obtain the vectors of the sensor axes and to ensure that the intersection of the sensor axes and the center of precision ball coincide accurately. However, this new R-test with the addition of positioning datums and a sliding table overcomes these problems. The calibration of the R-test is described in detail. Finally, a four-point measurement experiment for identifying the geometric errors of a rotary axis has been conducted, and the effectiveness of the measurement method is verified by a prediction experiment and a comparative experiment of double ball bar (DBB).

In order to raise the low efficiency of traditional screening machine, a new parallel mechanism (PM) with two translation and one rotation is proposed. Analyze the composition of each kinematic chain based on topological characteristics of mechanism The analytical method is utilized to simplify three constraint equations of PM respectively and the correctness is verified by Matlab. On the basis of kinematic analysis, the Jacobian matrix of mechanism is solved, and decoupling characteristics of mechanism input-output control modes are evaluated. The mechanism is coupled between translational input Y and translational output x, and three input-output control modes are decoupling. In addition, the singular configuration of PM is also analyzed. The discrete element method was used to simulate material screening, and the influence of DOF on screening efficiency was analyzed by EDEM software and experiment, which result is met with the theoretical analysis

The displacement graphs (d-graphs) are the final form of planetary gear trains (PGTs) synthesis. The existing configuration synthesis methods for the d-graphs of PGTs need rotation graphs (r-graphs) as the intermediate step and produce a large amount of isomorphic KCs. This paper proposes a method to obtain d-graphs directly from the geared graph. Meanwhile, a uniform isomorphism identification method suitable for parent graphs, geared graphs, and d-graphs is presented. Finally, a fully automatic method based on parent graphs is tested on synthesizing 1-DOF PGTs with up to nine links. Our synthesis results and those in the literature are comparatively analyzed, and the reasons for contradictory synthesis results are analyzed.

This paper presents a three Degrees of Freedom (DOFs) parallel manipulator with no rotational capacity. Planar kinematic pairs (revolute joint and prismatic joint) are exclusively employed in this parallel structure. The parallelogram joint in each kinematic chain assists to ensure the moving platform’s orientation is constant throughout the reachable workspace. Unlike the general parallel mechanisms, three identical kinematic limbs are degenerated to two kinematic limbs through merging two passive prismatic joints with same movement. Three active sliding joints are still required to drive this special parallel structure. Its mobility characteristic is firstly studied in detail and all possible singularity configurations are discussed by means of screw theory. The Lagrangian formulation is employed to compute the mathematical model of the inverse dynamic problem. The reachable workspace is obtained based on the inverse kinematic solutions. The distributions of the maximum joint force effect and maximum joint velocity effect are conducted. An example is provided to illustrate their trends under preset motion of the mobile platform.

A method of robust control of a specialized manipulator designed to work as part of a robotic complex for servicing vertical surfaces is proposed and studied. The complex consists of a wheeled platform, a wheeled vertical motion robot with a vacuum contact device and a manipulator. In the transport position, the robot is attached to the operating element (gripper) of the manipulator and is located on the platform so that its contact plane is almost parallel to the plane of the platform. After the platform approaches the wall, the manipulator brings the robot into the working position, bringing its contact plane to the surface of the wall. Then the vacuum pump of the robot is switched on, the robot is sucked against the wall, disconnects from the grasp of the manipulator, and then moves along the wall in autonomous mode. This article describes the operation of the manipulator at the stage of bringing the robot into the working position.

The kinematic and dynamic constraints of a closed kinematic chain as well as the motion equations of a cooperative robotic chain are derived in the present article. In its structure, this system employs friction to bring the end effector of cooperative arm with the common load into contact. This results in complex and time-varying constraints on the load and the end effector of cooperative arm as slip can occur on the object surface. On the contrary, one can easily change the connection loop of arms in face of obstacles. To this end, the specified objective is considered in the design of robot path and solution algorithms are defined based on the possibility of slip. The results are then used to implement the optimization algorithm of load distribution and calculate the dynamic load-carrying capacity. Hence, not only is the inverse dynamics studied in detail, the robot performance is evaluated in various conditions. For this purpose, the results of a cooperative robotic chain carrying a common load are compared for different values of surface friction coefficient and maximum permissible internal force. This is followed by a comparison with appropriate simulations in ANSYS. Moreover, the dynamic load-carrying capacity of the system in terms of the changes in maximum permissible internal force and the surface friction coefficient between the arm's end effector and the load is obtained. The results indicate that when appropriate conditions for the friction between end effector and load in addition to an internal force proportionate to the path are provided, the dynamic load-carrying capacity of any system can be improved. For instance, on a certain path and for the friction coefficient of 0.8 and internal force of 0.2, the dynamic load-carrying capacity of a single-arm system with grasp contact in end effector, after adding the auxiliary arm with frictional contact in end effector, reached 9.34 kg which shows an increase of 5.09 kg.

SUMMARYThis paper presents a novel method for modeling a 3-degree of freedom open kinematic chain using quaternions algebra and neural network to solve the inverse kinematic problem. The structure of the network was composed of 3 hidden layers with 25 neurons per layer and 1 output layer. The network was trained using the Bayesian regularization backpropagation. The inverse kinematic problem was modeled as a system of six nonlinear equations and six unknowns. Finally, both models were tested using a straight path to compare the results between the Newton–Raphson method and the network training.

In the type synthesis of kinematic chains, identification of distinct mechanisms of a kinematic chain is an important step. The links which are having same functional behavior are grouped as same inversion. In the present paper, an additive approach based on connectivities of the links is proposed. The functional behavior of any link as a part of k-chain can be found by means of topological analysis. In general, adjacency of a link with other links is a primary tool for the topological analysis. In the present paper, the extent of adjacency consideration is the main criteria by which similar functional behavior leading to same inversion is identified. A new parameter ‘Additive Adjacency’ is defined in the algorithm. A new computation table ‘Remote Adjacency Influence Table’ (RAIT) is introduced to control the progress of the adjacency calculations. The proposed method is tested on various linkages (8, 9, 10) with different Degree of Freedom (DoF).

Context: The deep squat (DS) test is a component of the functional movement screen, which is used to assess the quality of fundamental movement patterns; however, the accuracy of the DS has not been studied. The DS is a complex, total body movement pattern with evaluation required at several points along the kinematic chain. Objective: To assess the accuracy of DS scoring by an athletic trainer, physical therapist, and exercise science professional via a comparative analysis with kinematic data (KD) and to identify scoring criteria that would improve agreement between raters and KD scores. Design: Cross-sectional study. Setting: Motion analysis laboratory. Participants: A rater from each of 3 movement science disciplines rated the DS of 23 male college athletes (20.3 [1.2] y; 70.5 [3.5] kg). Interventions: Subjects were outfitted with reflective markers and asked to perform the DS. The DS performance was scored by 3 raters and kinematic analysis. Subsequently, the optimal set of criteria that minimized the difference between mode rater score and KD was determined via a Nelder–Mead simplex optimization routine. Main Outcome Measures: Intraclass correlation coefficients (ICCs) were calculated using SPSS (version 23; IBM, Armonk, NY) to determine tester agreement with the KD score and between the mode score and KD score. Results: Agreement was poor for the athletic trainer (ICC = .387), physical therapist (ICC = .298), exercise science professional (ICC = .378), and raters’ DS scores when compared with the KD. Agreement was poor for the mode score when compared with KD prior to optimization and good following optimization (ICC = .830), thereby allowing identification of specific scoring errors. Conclusions: Agreement for DS scores is poor when compared with KD; however, it may be improved with optimization of DS scoring criteria.

This study aimed to evaluate the influence of measuring the length of the medial collateral ligament (MCL) to compare the MCL burden when the knee joint is placed under valgus stress in the open and closed and closed kinetic chain. Two examiners conducted the examination. The MCL length was measured using ultrasonography. Two subjects were measured in unload bearing and load-bearing positions, with and without valgus stress test at the knee joint extension and 30° flexion, under eight different measurement conditions. The MCL of the subject was delineated in the longitudinal direction using an ultrasound system. The attachment points of the medial femoral and tibial condyle of the MCL were identified, and the ligament length was measured. The MCL rate before and after the valgus stress test in the loading and unloading positions was calculated. The MCL length increased by an average of 8.9% when the external stress test was performed in the non-weight bearing and knee extension positions and by an average of 17.0% when external stress was applied in the non-weight bearing and knee flexion positions. The MCL length increased by an average of 12.2% when the external stress test was performed in the load-bearing and knee extension positions and an average of 8.9% when the valgus stress test was applied in load-bearing and knee flexion positions. In conclusion, the effect of valgus stress on the MCL differs between load-bearing and non-load-bearing positions. It is considered that the dynamic stabilization mechanism works in the knee joint flexion position in the load position and works simultaneously as the static stabilization mechanism, which limits the knee joint valgus and reduces the extension rate of MCL. Therefore, this study reconsiders the shifting of traditional therapy from open kinetic chain to close kinetic chain.

In this paper, an original mathematical model and experimental results for the vibration generator and the magnetic spring prototype that converts mechanical energy to electrical energy are proposed. The magnetic spring model is developed by a robotic approach based on Denavit–Hartenberg’s notation and designed by the 2-degrees of freedom kinematic chain for determination of its motion and estimation of several resonance frequencies useful in many energy harvesting applications. The vibration generator that moves the magnetic spring is modeled by neural networks and the magnetic spring potential energy is calculated by the finite elements method (FEM). Furthermore, the magnetic spring and the vibration generator are designed by the Simulink block diagram. Testing results of the magnetic spring and vibration generator displacement conducted in laboratory have shown good agreement with simulation results.

The objective of this case study is to observe the existence of an anticipation mechanism at the muscle groups level of the upper limbs. We tried to highlighted this anticipation process by measuring the potential of surface electric for some muscle groups representing the kinematic chain on the right side, involved in the motor action of catching a basketball and a 3kg medicine ball with two hands to the chest. We conducted a case study of a 13-year-old child, female gender. As a measurement method, we used surface electromyography signals of the EMG Trigno Delsys wireless system with 16 electrodes. We determined the moment when the muscles come into action by increasing the potential of surface electric and the moment when the action of catching the ball takes place, using the information provided by the accelerometers incorporated in the sensors of the Delsys equipment used. Therefore, we obtained information about how different muscle groups come into action which helped us to get an idea of how the child's movement is structured. Based on results of accelerations and EMG signals acquired we have formulated conclusions regarding the neuromuscular control of the tested subject. We also planned for the future to test a larger group of participants in the study research of anticipation mechanism in children who do not practice any performance sports.

This paper presents a five degree of freedom (5-DOF) redundantly actuated parallel mechanism (PM) for the parallel machining head of a machine tool. A 5-DOF single kinematic chain is evolved into a secondary kinematic chain based on Lie group theory and a configuration evolution method. The evolutional chain and four 6-DOF kinematic chain SPS (S represents spherical joint and P represents prismatic joint) or UPS (U represents universal joint) can be combined into four classes of 5-DOF redundantly actuated parallel mechanisms. That SPS-(2UPR)R (R represents revolute joint) redundantly actuated parallel mechanism is selected and is applied to the parallel machining head of the machine tool. All formulas of the 4SPS-(2UPR)R mechanism are deduced. The dynamic model of the mechanism is shown to be correct by Matlab and automatic dynamic analysis of mechanical systems (ADAMS) under no-load conditions. The dynamic performance evaluation indexes including energy transmission efficiency and acceleration performance evaluation are analyzed. The results show that the 4SPS-(2UPR)R mechanism can be applied to a parallel machining head and have good dynamic performance.

Hirsch, SM, Chapman, CJ, Frost, DM, and Beach, TAC. Mechanical energy expenditure at lumbar spine and lower extremity joints during the single-leg squat is affected by the nonstance foot position. J Strength Cond Res 36(9): 2417-2426, 2022-Previous research has shown that discrete kinematic and kinetic quantities during bodyweight single-leg squat (SLS) movements are affected by elevated foot positioning and sex of the performer, but generalizations are limited by the high-dimensional data structure reported. Using a 3D inverse dynamical linked-segment model, we quantified mechanical energy expenditure (MEE) at each joint in the kinetic chain, the total MEE (sum of MEE across aforesaid joints), and the relative contribution of each joint to total MEE during SLSs performed with elevated foot positioned beside stance leg (SLS-Side), and in-front of (SLS-Front) and behind (SLS-Back) the body. Total MEE differed between SLS variations ( p = 0.002), with the least amount observed in the SLS-Back (effect size [ES] = 0.066-0.069). Approximately 50% of total MEE was contributed by the knee joint in each SLS variation, whereas MEE at the ankle, hip, and lumbar spine (in absolute and relative terms) varied complexly as a function of the elevated foot position. Total MEE ( p = 0.0192, ES = 0.852) and the absolute MEE at the knee and spine was greater in men across the SLS variations performed ( p = 0.025-0.036, ES = 0.715-0.766), but only the lumbar spine contribution to total MEE was larger in men across all SLS variations ( p = 0.045, ES = 0.607). Otherwise, there were no other sex-specific responses observed. Biomechanically, SLS movements are generally "knee-dominant," but changing elevated foot position effectively redistributes MEE among other joints in the linkage. Consistent with the previous conclusions reached based on discrete kinematic and kinetic data, not all SLSs are equal.

Robotics has undergone a profound revolution in the past 50 years, moving from the laboratory and research institute to the factory and home. Kinematics and dynamics theories have been developed as the foundation for robot design and control, based on the conventional definition of robots: a kinematic chain of rigid links.

Background: The hip muscle plays various roles. Several types of functional performance tests are used for the assessment of patients with various lower extremity injuries. Hip muscle functions are important to test the performance of maintaining the spine, pelvic, and leg during bridging exercise. We designed a novel functional performance test tool, which we named close kinetic chain dynamic lower extremity stability (CKCLE) test to assess hip muscle functions. Objects: The purpose of this study was to determine the relationship between CKCLE test and hip extensor, external rotator, and abductor strengths. Methods: Twenty-two subjects were recruited in the present study (13 males and 9 females). The hip extensor, external rotator, and abductor muscle strengths were measured using a Smart KEMA strength sensor. When the examiner said “Go”, the subject performed the CKCLE test by moving one leg from the floor and touching the opposite knee and then return to the floor while maintaining the bridging position. The subjects attempted as many “touches” as possible in the allotted time (20 seconds) during the maximal tests. The correlation between the hip muscle (extensor, external rotator, and abductor) strength of the supporting leg and the number of CKCLE tests performed in 20 seconds was determined using the Pearson correlation. Results: Hip extensor (r = 0.626, p < 0.05), hip external rotator (r = 0.616, p < 0.05), and hip abductor muscle strengths (r = 0.475, p < 0.05) positively correlated with the number of CKCLE tests performed. Conclusion: We designed a CKCLE test and found that performance in the test correlated with hip extensor, external rotator, and abductor muscle strengths. The result suggests that the CKCLE test can be applied as a performance test to assess the functions of the hip extensor, external rotator, and hip abductor muscles.

There are several in vivo and in vitro control performances with artificial micro-swimmers; however, control of a biohybrid micro-swimmer using an open kinematic chain remains fairly untouched to this date. In this work, non-contact maneuvering control of a single magnetotactic bacterium cell is simulated under in vivo conditions of a synovial joint with associated physical properties of the respective synovial cavity. A very detailed mathematical model representing in vivo swimming conditions of an actual bacterium cell is built followed by a PID control scheme with adaptive integral gains. The performance of the control law is presented with the help of time-dependent errors to different yaw-angle references accompanied by the time-dependent states of the coupled system. The results show that the proposed control law is capable of adjusting the heading, i.e., yaw-angle, of the simulated magnetotactic bacterium species, i.e., Magnetospirillum Gryphiswaldense, moving at proximity to a curved surface, i.e., the inner surface of the synovial joint in a Homo sapiens. The results further demonstrate that it is possible to achieve set-point tracking against both constant and time-dependent references.

Werin, MB, Maenhout, AG, Icket, J, Jacxsens, N, Kempkes, E, and Cools, AM. Does the activity in scapular muscles during plyometric exercises change when the kinetic chain is challenged?-An EMG study. J Strength Cond Res XX(X): 000-000, 2020-Plyometric exercises for the shoulder are used in rehabilitation and in workout regime when the sport demands high speed power training. The aim of this clinical laboratory electromyography (EMG) study was to determine whether scapular muscle performance differs during plyometric shoulder exercises when changing the demand on the kinetic chain. Thirty healthy overhead athletes, with a mean age of 22.7 years (±2.2), performed 6 exercises, with both a low and a high demand on the kinetic chain, in prone, side and standing in positions. The EMG activity of the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) on the tested side and bilateral of gluteus maximus (GM) and abdominal oblique externus (OE) was registered with wireless surface EMG. Intermuscular muscle ratios UT/SA, UT/MT, and UT/LT were also calculated. The level of significance set for the study was alpha = 0.05. The muscle ratio UT/SA was significantly lower (p < 0.05) when high demand on the kinetic chain compared with low. SA muscle activity showed significantly (

This paper focuses on optimization of kinematic chain to reduce force-induced error in the scheme design phase of a five-axis machine tool. After conducting process planning on the machining target, local deformation of motion units in cutting positions is considered using a geometric way. A mathematical model is then established describing the influence of local deformation error on the general machining error through homogeneous transformation matrices. Conceptual model of the machine tool is constructed to obtain deformation distribution using static FEA. Error sensitivity coefficients are then calculated and compared among all alternative kinematic chains to select the optimized scheme. The proposed method is verified through a designing example of a five-axis vertical machining center. The optimized kinematic chain could lower the magnitude of deformation sensitivities by 9.69% and increase error equalization variance by 71.25% compared to the conventional method.

The aim of this article is to chronicle a novel methodology for measuring and estimating rotary joint axes of an articulated robot. The key contribution of the proposed methodology is a practical way of estimating rotary joint axes of an articulated robot by taking static position measurements of every rotary joint, so that the estimated rotary joint axes reflect the real characteristics of the actual robot. Furthermore, the proposed methodology enables an advanced calibration of robot kinematic parameters for a better motion performance. The metrology requires a laser tracker for taking static position measurements. The proposed methodology is intended for articulated robots with serially linked rotary joints. To make the basic concepts easier to understand, the study uses a lower-pair kinematic chain with three serially linked rotary joints. The basic concepts can be extended and applied to higher degree-of-freedom articulated robots. To validate the research outcomes, this article proceeds with a validation experiment that demonstrates the use of the proposed methodology with empirical data produced by a metrology simulation experiment. The results of the validation experiment indicate that the proposed methodology is capable of measuring and estimating rotary joint axes of an articulated manipulator even in the presence of typical sensor noises.

We address the problem of controlling a partially constrained trajectory of the manipulation frame–an arbitrary frame of reference rigidly attached to the object–as the desired motion about this frame is often underdefined. This may be apparent, for example, when the task requires control only about the translational dimensions of the manipulation frame, with disregard to the rotational dimensions. This scenario complicates the computation of the grasp frame trajectory, as the mobility of the mechanism is likely limited due to the constraints imposed by the closed kinematic chain. In this letter, we address this problem by combining a learned, object-agnostic manipulation model of the gripper with Model Predictive Control (MPC). This combination facilitates an approach to simple vision-based control of robotic hands with generalized models, enabling a single manipulation model to extend to different task requirements. By tracking the hand-object configuration through vision, the proposed framework is able to accurately control the trajectory of the manipulation frame along translational, rotational, or mixed trajectories. We provide experiments quantifying the utility of this framework, analyzing its ability to control different objects over varied horizon lengths and optimization iterations, and finally, we implement the controller on a physical system.

Intermittent motion mechanisms are widely used in semiautomatic and automatic machinery. Currently, the most common are mechanisms with a one-way coupling or mechanisms of variable structure. The intermittent movement in these mechanisms is provided by breaking the kinematic chain, so their use is undesirable in high-speed machines. The paper presents and analyzes kinematics of planetary transmission with elliptical gears, which performs intermittent motion of output link without interruption of kinematic chain. A kinematic model of the mechanism is constructed, and there are obtained equations for determining the velocity analogue of the output link of the planetary gear. An experimental verification of the adequacy of the developed mathematical model was carried out on the example of studying the position function of the mechanism. The measurement errors were estimated using statistical methods. Using the chi-squared test, the hypothesis of a normal distribution of measurement errors was verified, and confidence interval was determined.

Development of compact and easy to use mathematical models of articulated vehicles for the motion planning, control, and localization purposes becomes more and more important in the era of intelligent transportation systems, especially when there exists a need of reliable predictions of motion for multi-body (semi-)automated freight and public transportation vehicles of various kinematic structures. We propose a modular algorithmic approach to kinematic modelling of nonholonomic (multi-)articulated buses, including the N-trailer vehicles as a special case, comprising a car-like prime-mover passively interconnected with arbitrary number of segments (wagons/trailers) equipped with fixed or steerable wheels, and with various locus of a driving axle in a kinematic chain. Kinematic models are valid under an assumption of a pure rolling of all the vehicle wheels (no skid/slip motion), which is practically justified for the low-speed maneuvering conditions. The proposed approach leads to compact nonlinear models which, thanks to their modular construction, preserve clear geometrical interpretation of velocity couplings between the vehicle segments. Derivations of kinematic models for popular structures of articulated and bi-articulated urban buses are presented for various driving-axle locus and steering capabilities. Experimental model validation, conducted with a full-scale wagon-driven articulated bus, illustrates utility of the approach.

Purpose2D laser rangefinders (LRFs) are commonly used sensors in the field of robotics, as they provide accurate range measurements with high angular resolution. These sensors can be coupled with mechanical units which, by granting an additional degree of freedom to the movement of the LRF, enable the 3D perception of a scene. To be successful, this reconstruction procedure requires to evaluate with high accuracy the extrinsic transformation between the LRF and the motorized system.Design/methodology/approachIn this work, a calibration procedure is proposed to evaluate this transformation. The method does not require a predefined marker (commonly used despite its numerous disadvantages), as it uses planar features in the point acquired clouds.FindingsQualitative inspections show that the proposed method reduces artifacts significantly, which typically appear in point clouds because of inaccurate calibrations. Furthermore, quantitative results and comparisons with a high-resolution 3D scanner demonstrate that the calibrated point cloud represents the geometries present in the scene with much higher accuracy than with the un-calibrated point cloud.Practical implicationsThe last key point of this work is the comparison of two laser scanners: the lemonbot (authors’) and a commercial FARO scanner. Despite being almost ten times cheaper, the laser scanner was able to achieve similar results in terms of geometric accuracy.Originality/valueThis work describes a novel calibration technique that is easy to implement and is able to achieve accurate results. One of its key features is the use of planes to calibrate the extrinsic transformation.

Collapse of masonry structures under the influence of seismic action typically takes place via specific failure mechanisms, which have been well-documented. Assuming these mechanisms can be modelled as a kinematic chain, equations of motion can be derived and solved to predict dynamic rocking response. Previous derivations typically assume that the kinematic chain is comprised of rigid bodies with rigid interfaces, which are assumptions that can be both unrealistic and un-conservative. In this paper, rocking equations of motion are re-derived considering the presence of flexible interfaces and crushing effects. Specifically, new derivations are presented for single, two and multiple block mechanisms, while two different formulations for modelling non-rigid interfaces are also proposed. These formulations are compared, and the importance of interface flexibility is evaluated through comparison of the new models with previous formulations that assume purely rigid interfaces. The new equations of motion are also practically evaluated through comparison with advanced numerical modelling simulations.

Context Scapular rehabilitation exercises should focus on selective activation of weaker muscles and minimal activation of hyperactive muscles. For rehabilitation of overhead athletes, single-plane open chain exercises below 90° of shoulder elevation are often recommended. Moreover, incorporating the kinetic chain in shoulder rehabilitation exercises is advised and has been suggested to influence scapular muscle activity levels. Objective To study the influence of kinetic chain incorporation during 5 variations of a shoulder-elevation exercise on scapular muscle activity. Design Cross-sectional study. Setting University laboratory. Patients or Other Participants Thirty-one asymptomatic participants (15 men, 16 women). Main Outcome Measure(s) The electromyographic activity of the upper (UT), middle (MT), and lower (LT) trapezius, and serratus anterior was determined during 5 variations of bilateral elevation with external rotation: (1) open-hand position (reference exercise), (2) closed-hand position, (3) dynamic bipedal squat, (4) static unipedal squat, and (5) dynamic unipedal squat on the contralateral leg. All data were normalized as a percentage of maximal voluntary isometric contraction (MVIC). Results A closed-hand position (exercise 2) instead of an open-hand position (exercise 1) resulted in lower MT (mean difference = 3.44% MVIC) and LT (mean difference = 7.76% MVIC) activity. Incorporating the lower limb (exercises 3–5) increased UT activity when compared with exercise 1 (mean differences = 3.67, 2.68, 5.02% MVIC, respectively), which in general resulted in increased UT : MT ratios. Additionally, LT activity decreased when a dynamic unipedal squat was added (mean difference: 4.90% MVIC). For the serratus anterior, the greatest activity occurred during elevation in a static unipedal squat position (exercise 4, 22.90% MVIC). Conclusions Incorporating the kinetic chain during shoulder-elevation exercises influenced scapular muscle activity and ratios. In particular, incorporating the lower limb resulted in more UT activity, whereas the open-hand position increased MT and LT activity.

PURPOSE OF REVIEW: The purpose of this review will be to provide both a historical and recent review of the role of the kinetic chain for the overhead athlete. The kinetic chain concept will then be applied to clinical exercise modifications and integrations for prevention and treatment of shoulder injury. RECENT FINDINGS: The primary conclusion reached through this review is the important role the lower extremity, trunk, and scapular region play in the development of optimal terminal segment acceleration in the overhead throwing and serving motion. Failure of any links in the kinetic chain has implications for shoulder and elbow injury in the overhead athlete. Modifications of traditional shoulder exercises emphasizing activation of the scapular stabilizers and core musculature alongside concomitant rotator cuff activation are recommended and supported in EMG research. SUMMARY: Future research is needed to further identify risk factors and rehabilitation and prevention strategies and key clinical tests for the overhead athlete. The goal is to elucidate the important role the kinetic chain plays in both performance enhancement and injury prevention for the overhead athlete. Understanding the key role all segments of the kinetic chain play in the complex biomechanical segmental rotations required for high-level throwing and serving will assist clinicians who work with overhead athletes.

In this paper, an approach for the evaluation of human-robot collaboration towards high performance is introduced and implemented. The human arm and the manipulator are modelled as a closed kinematic chain and the proposed task performance criterion is used based on the manipulability index of this chain. The selected task is a straight motion in which the robot end-effector is guided by the human operator via an admittance controller. The best location of the selected task is determined by the maximization of the minimal manipulability along the path. Evaluation criteria for the performance are adopted considering the ergonomics literature. In the experimental set-up with a KUKA LWR manipulator, multiple subjects repeat the specified motion to evaluate the introduced approach experimentally.

Dragline excavators are closed-loop mining manipulators that operate using a rigid multilink framework and rope and rigging system, which constitute its front-end assembly. The arrangements of dragline front-end assembly provide the necessary motion of the dragline bucket within its operating radius. The assembly resembles a five-link closed kinematic chain that has two independent generalized coordinates of drag and hoist ropes and one dependent generalized coordinate of dump rope. Previous models failed to represent the actual closed loop of dragline front-end assembly, nor did they describe the maneuverability of dragline ropes under imposed geometric constraints. Therefore, a three degrees of freedom kinematic model of the dragline front-end is developed using the concept of generalized speeds. It contains all relevant configuration and kinematic constraint conditions to perform complete digging and swinging cycles. The model also uses three inputs of hoist and drag ropes linear and a rotational displacement of swinging along their trajectories. The inverse kinematics is resolved using a feedforward displacement algorithm coupled with the Newton-Raphson method to accurately estimate the trajectories of the ropes. The trajectories are solved only during the digging phase and the singularity was eliminated using Baumgarte′s stabilization technique (BST), with appropriate inequality constraint equations. It is shown that the feedforward displacement algorithm can produce accurate trajectories without the need to manually solve the inverse kinematics from the geometry. The research findings are well in agreement with the dragline real operational limits and they contribute to the efficiency and the reduction in machine downtime due to better control strategies of the dragline cycles.

Konfiguracija O-X glide hibridnog mehanizma, originalnog, mehanizma razvijenog na FTN-u za potrebe gradnje mašina alatki i manipulacionih sistema, podrazumjeva implementaciju nelinearnog kinematskog lanca u upravljački sistem. Hibridni mehanizmi, u koje ovaj mehanizam spada, predstavljaju kombinaciju serijskih i paralelnih mehanizmam formiranu sa ciljem ostvarivanja što boljeg iskorištenja mehaničkih karakteristika. Odabrani upravljački softver, LinuxCNC, je otvorene arhitekture, što znači da se mogu izvršiti promjene u jezgru, u zavisnosti od potrebe, da bi se definisala konfiguracija i na taj način primenom besplatnog softvera realizovati ekpserimentalni prototip mašine alatke.

The aim of the work is to study the myofacsical cinematic chains of the lower limb and their effect on thenature of the violation of the vaulted vault apparatus by electromigraphy in children 7–14 years old engaged in taekwondo. Methods. A total of 50 children aged 7 to 14 studied in the taekwondo section. 30 children with signs of functional impairment of the articulation of the foot and flatness of the I–II degree of severity were the main group. The other 20 children without a violation of the arch of the foot formed a control group. The plotographic analysis was carried out on the computer complex “DIERS FAMUS” (Germany). Anthropometric study is supplemented with electromyographic research using the "Neuro-EMG-Micro" apparatus (Russia). The muscles that were included in the three miofascial cinematic chain of the leg were studied. To establish the objective signs of pain, a questionnaire using YAS protocol was used. Quality of life was studied using acne SF-36. Statistical processing of data was carried out using methods of parametric and nonparametric statistics. Results It is established that the muscles of the corresponding group on the shin when comparing the longitudinal axes are part of the anterior, posterior, and lateral myofascial kinematic chain, which ends on different foot surfaces. All of them take part in thesupport of the vaulted foot apparatus. The conducted study of electrophysiological activity revealed its decrease and imbalance of tone of individual muscles of the shin, indicating an important role of the violation of the frequency-amplitude characteristics of individual muscles in the composition of myofacsical kinematic chains in creating conditions for functional disorders of the arch of the foot and flat feet. The comparative analysis of the anthropometric indices of the foot of children of different ages and their comparison with electromigraphy data fully confirms modern scientific ideas about the determining role of the myofascial kinematic chains of the leg in ensuring the normal functioning of the foot as an important organ of the locomotor apparatus of the person. Conclusion. The tonic balance of the muscles of the leg is a stabilizing biomechanical force for maintaining the normal position of the arch of the foot, and their imbalance may be the cause of the development of flatness, which is well manifested in electroneuromyographic examination, the results of which can be used as an objective methodfor monitoring the foot, for selection methods of correction and prediction of the effectiveness of the results of the applying of appropriate physical therapy in people with flat feet.Keywords: flatfoot, myofascial chains, electromyography, children.

A planar kinematic chain consists of $n$ links connected by joints. In this work we investigate the space of configurations, described in terms of joint angles, that guarantee that the kinematic chain is closed. We give explicit formulas expressing the joint angles that guarantee closedness by a new set of parameters, the diagonal lengths (the distances of the joints from the origin) of the closed kinematic chain. Moreover, it turns out that these diagonals are contained in a domain that possesses a simple structure. We expect that the new insight can be applied for several issues such as motion planning for closed kinematic chains or singularity analysis of their configuration spaces. In order to demonstrate practicality of the new method we present numerical examples., 18 pages, 10 figures

This paper proposes a method for tracing key geometric errors of vertical machining centers based on global sensitivity analysis in order to address inconsistent dimensions associated with sensitivity coefficients, random analytical variables, and geometric errors across different positions. The kinematic chain forward solution and the volumetric error model of vertical machining centers based on a global coordinate system is constructed by means of screw theory; the identification model is constructed based on the double bar ball measurement principle. The identification model is transformed into an optimization-design problem, which is solved by a simulated annealing–genetic algorithm. The idea of orthogonal experimental design is used for reference, and 25 test points are selected for the machine tool workspace. By taking the volumetric error model as a sensitivity calculation model, and by taking geometric errors as analytical factors, multi-factor orthogonal experiments and single-factor parametric tests are designed, respectively. The F-values of the significance test results of the orthogonal experiments and the Euclidean norms, ∆P and ∆O, of the parametric test results are used as global sensitivity coefficients. The analysis results suggest that the traceability results of the key geometric errors are essentially the same across the two tests and the 13 key geometric errors of the J1VMC400B vertical machining center are traced.