Joint Angle Curves Research Articles

Lower limb joint contact forces and ground reaction forces analysis based on Azure Kinect motion capture

Traditional gait analysis systems are typically complex to operate, lack portability, and involve high equipment costs. This study aims to establish a musculoskeletal dynamics calculation process driven by Azure Kinect. Building upon the full-body model of the Anybody musculoskeletal simulation software and incorporating a foot-ground contact model, the study utilized Azure Kinect-driven skeletal data from depth videos of 10 participants. The in-depth videos were prepossessed to extract keypoint of the participants, which were then adopted as inputs for the musculoskeletal model to compute lower limb joint angles, joint contact forces, and ground reaction forces. To validate the Azure Kinect computational model, the calculated results were compared with kinematic and kinetic data obtained using the traditional Vicon system. The forces in the lower limb joints and the ground reaction forces were normalized by dividing them by the body weight. The lower limb joint angle curves showed a strong correlation with Vicon results (mean ρ values: 0.78 ~ 0.92) but with root mean square errors as high as 5.66°. For lower limb joint force prediction, the model exhibited root mean square errors ranging from 0.44 to 0.68, while ground reaction force root mean square errors ranged from 0.01 to 0.09. The established musculoskeletal dynamics model based on Azure Kinect shows good prediction capabilities for lower limb joint forces and vertical ground reaction forces, but some errors remain in predicting lower limb joint angles.

Research on Excavator Trajectory Control Based on Hybrid Interpolation

In this study, to address the issues of tooth tip operation discontinuity and jitter during autonomous excavator operation, a multi-segment mixed interpolation method utilizing different higher-order polynomials has been proposed. This approach is designed to optimize the tooth tip trajectory of the excavator under multiple constraints, resulting in a smoother trajectory. Specifically, the single-bucket excavator was chosen as the research object, and three different high-order mixed polynomials were utilized to interpolate the trajectory of the digging discrete points. Through a comparative analysis under multiple constraints, this study explored and analyzed the joint angle, angular velocity, and angular acceleration curves of each excavator’s joint. An experimental platform was established to investigate the hydraulic system of an excavator, and the optimal trajectory was controlled using a high-order mixed polynomial interpolation. The results of this study demonstrate that the tracking accuracy of the excavator’s actuator under the optimal interpolation strategy is high, with a maximum displacement deviation of ±3 mm. Additionally, during operation, the excavator manipulator runs smoothly and continuously with minimal flexible impact and vibration.

Exploring the effects of body weight support systems on lower limb kinematics and muscle characteristics

Bipedal gait is one of the most important forms of human movement. However, every year many people lose their ability to walk due to disease. Weight support systems that reduce or even eliminate the effect of upper body mass loading on the lower limbs are among the most commonly used devices in gait rehabilitation. The designed weight support system provides body support while innovatively proposing a torso motion assist function. In this paper, walking experiments were performed on normal healthy subjects under five different weight-supported conditions, and motor and surface electromyography (sEMG) signals of the lower limb muscles were collected and analyzed. The results showed a slight decrease in joint motion of the lower extremities in the reference (free walking) and weight-supported-only assisted conditions, while there was no change in the joint angle curve waveform. In contrast, there was a significant change in the joint angle waveform between weight support plus trunk transfer and free walking. Different muscles differ in the significance of feature changes under different auxiliary conditions. By studying the changes in motor and muscle activation levels in the human lower extremity under the weight support system, it can be used as an indicator to assess specific gait indicators and muscle activity during the rehabilitation of the lower extremity in rehabilitated patients.

Real-Time and Automatic System for Performance Evaluation of Karate Skills Using Motion Capture Sensors and Continuous Wavelet Transform

In sports science, the automation of performance analysis and assessment is urgently required to increase the evaluation accuracy and decrease the performance analysis time of a subject. Existing methods of performance analysis and assessment are either performed manually based on human experts’ opinions or using motion analysis software, i.e., biomechanical analysis software, to assess only one side of a subject. Therefore, we propose an automated system for performance analysis and assessment that can be used for any human movement. The performance of any skill can be described by a curve depicting the joint angle over the time required to perform a skill. In this study, we focus on only 14 body joints, and each joint comprises three angles. The proposed system comprises three main stages. In the first stage, data are obtained using motion capture inertial measurement unit sensors from top professional fighters/players while they are performing a certain skill. In the second stage, the collected sensor data obtained are input to the biomechanical software to extract the player’s joint angle curve. Finally, each joint angle curve is processed using a continuous wavelet transform to extract the main curve points (i.e., peaks and valleys). Finally, after extracting the joint curves from several top players, we summarize the players’ curves based on five statistical indicators, i.e., the minimum, maximum, mean, and mean ± standard deviation. These five summarized curves are regarded as standard performance curves for the joint angle. When a player’s joint curve is surrounded by the five summarized curves, the performance is considered acceptable. Otherwise, the performance is considered unsatisfactory. The proposed system is evaluated based on four different karate skills. The results of the proposed system are identical to the decisions of the expert panels and are thus suitable for real-time decisions.

Control strategy for intraspinal microstimulation based on central pattern generator

Intraspinal microstimulation (ISMS) is considered as a special functional electrical stimulation (FES) method. This method can restore the movement of paralyzed limbs in patients with spinal cord injury (SCI) using electrical stimulation of spinal cord. There is a special site for central pattern generator (CPG) in the spinal cord. The ISMS acts on the CPG site, and single electrode stimulation produces alternating motion in the hindlimbs of SCI rats. Based on the long short-term memory network (LSTM), a mapping model was established between the stimulation intensity of specific CPG sites and the angle of the knee joint to reflect the motor characteristics of the rat hindlimb. We proposed an LSTM-iterative learning control (ILC) strategy to form a closed-loop control to accurately control hindlimb movement. The proposed LSTM model fits the actual joint angle curve well, and the LSTM-ILC strategy can accurately regulate the hindlimb movement, allowing rats to perform rehabilitation training based on pre-set knee trajectories.

Development of a Lower Extremity Exoskeleton as an Individualized Auxiliary Tool for Sit-to-Stand-to-Sit Movements

This paper presents a lower extremity exoskeleton as a rehabilitation tool that involves electronics, biomedicine and mechanism design. Using the rehabilitation tool, the paralyzed lower limb muscles and impaired neurons of a stroke patient can be well revitalized during repeated stand-to-sit-to-stand movements. The body of an exoskeleton user can be well stabilized using a zero-torque theory. As compared with a “without” exoskeleton counterpart, an average of 66.98% reduction was observed in the RMS value of electromyography signals across the vastus intermedius muscle among a group of 5 healthy subjects with the exoskeleton (p <;.05), and a 47.248% reduction in the case of a female with an impaired lower limb. Ideally, the exoskeleton was designed to make a disabled user move in the same way as a healthy one, and the sit-to-stand-to-sit movement pattern of the female was improved, as evidenced by joint angle curves captured using a Kinect. Hence, the exoskeleton serves as an effective auxiliary sit-to-stand-to-sit tool not only for the elderly but also for those with mild lower limb motor impairment.

Crouch gait or flexed-knee gait in cerebral palsy – Is there a difference? A systematic review

Flexed knee gait is a common gait dysfunction in individuals with bilateral spastic cerebral palsy (BSCP) and is often addressed with single event multilevel surgery (SEMLS). SEMLS has been shown to have positive short-term effects especially on sagittal knee joint kinematics with less knee flexion during stance phase. However, mid- and long-term observations are rare, and results are reported in discrete parameters or summary statistics where temporal aspects are not considered.Does the improved knee joint kinematics after patellar tendon shortening (PTS) as part of SEMLS persist in the long-term in individuals with BSCP?Data of instrumented gait analysis of twelve participants (females/males: 5/7, mean age: 15.3 ± 3.4 years) with BSCP treated with PTS as part of SEMLS were retrospectively analyzed. Participants had had follow-up gait analysis 1, 5 and 7 years or more after surgery. Three-dimensional lower extremity kinematics of walking at a self-selected speed were collected using a 12-camera motion capture system and 4 embedded force plates. One-dimensional statistical parametric mapping (SPM) was used for data analysis, permitting time point comparisons of continuous data.Time point comparison revealed no significant differences in the sagittal plane for knee joint kinematics (p > 0.05) over the tree measurement time points. Hip and ankle joint kinematics as well as normalised walking speed remained stable over the observation period.This is the first study investigating lower extremity kinematics in patients with BSCP and flexed knee gait after SEMLS with SPM. Results demonstrate that positive effects on sagittal knee joint kinematics of PTS as part of SEMLS persist up to 9 years after surgery and progressivity does not reoccur. Thus, if clinical examination indicates an operation in individuals with BSCP, improved kinematics through SEMLS persist into adulthood. With the relatively new statistical procedure SPM gait can be displayed and analysed in established joint angle curves making them easier to understand (e.g. physiotherapists, movement scientists, physicians).

Long-term follow-up after patellar tendon shortening for flexed knee gait in bilateral spastic cerebral palsy

BackgroundFlexed knee gait is a common gait dysfunction in individuals with bilateral spastic cerebral palsy (BSCP) and is often addressed with single event multilevel surgery (SEMLS). SEMLS has been shown to have positive short-term effects especially on sagittal knee joint kinematics with less knee flexion during stance phase. However, mid- and long-term observations are rare, and results are reported in discrete parameters or summary statistics where temporal aspects are not considered. Research questionDoes the improved knee joint kinematics after patellar tendon shortening (PTS) as part of SEMLS persist in the long-term in individuals with BSCP? MethodsData of instrumented gait analysis of twelve participants (females/males: 5/7, mean age: 15.3 ± 3.4 years) with BSCP treated with PTS as part of SEMLS were retrospectively analyzed. Participants had had follow-up gait analysis 1, 5 and 7 years or more after surgery. Three-dimensional lower extremity kinematics of walking at a self-selected speed were collected using a 12-camera motion capture system and 4 embedded force plates. One-dimensional statistical parametric mapping (SPM) was used for data analysis, permitting time point comparisons of continuous data. ResultsTime point comparison revealed no significant differences in the sagittal plane for knee joint kinematics (p > 0.05) over the tree measurement time points. Hip and ankle joint kinematics as well as normalised walking speed remained stable over the observation period. SignificanceThis is the first study investigating lower extremity kinematics in patients with BSCP and flexed knee gait after SEMLS with SPM. Results demonstrate that positive effects on sagittal knee joint kinematics of PTS as part of SEMLS persist up to 9 years after surgery and progressivity does not reoccur. Thus, if clinical examination indicates an operation in individuals with BSCP, improved kinematics through SEMLS persist into adulthood. With the relatively new statistical procedure SPM gait can be displayed and analysed in established joint angle curves making them easier to understand (e.g. physiotherapists, movement scientists, physicians).

Extension Mechanism of the Proximal Interphalangeal Joint of the Human Phalanx: A Cadaveric Biomechanical Study.

Our purpose was to compare the contributions of these two systems to assess PIP joint extension in fresh cadaver models. Nine middle fingers of fresh cadavers were used. The PIP joint angle was measured while an extension load was applied on the extensor tendons. Specimens on which extension load was applied on the extrinsic extensors were classified as the extrinsic group, and those on which extension load was applied on the intrinsic extensors were classified as the intrinsic group. Linear regression analyses were performed to obtain regression equation and the extension load-PIP joint angle curve. The mean of slope of the curve was compared between the two groups using paired t-test. The same experiments were done for the metacarpophalangeal (MP) joint in 0° and 60° flexion to evaluate the effect of MP joint flexion on PIP joint extension. The mean slope of the extension load-PIP joint angle curve of the extrinsic group was significantly greater than that of the intrinsic group. With the MP joint in 0° flexion, the mean slope of the extrinsic and intrinsic groups was -0.148 and -0.117, respectively (greater absolute value means greater slope, p = 0.01). With the MP joint in 60° flexion, the mean slopes were -0.147 and -0.104, respectively (p = 0.015). The contribution of the intrinsic extensor for PIP joint extension shows decreasing trends with MP joint flexion. The extrinsic extensors have greater contribution for PIP joint extension compared with the intrinsic extensors.

Motion Planning Algorithm of a Multi-Joint Snake-Like Robot Based on Improved Serpenoid Curve

In order to study the winding motion of a multi-joint snake-like robot with multi-degree of redundancy in plane, a motion planning algorithm of a multi-joint snake-like robot based on improved Serpenoid curve equation is proposed in this paper. Firstly, the kinematics and dynamics models of a multi-joint snake-like robot are established, and the joint angle curve equation and the thrust expression of each joint of the robot relative to time are obtained. Next, the existing Serpenoid curve equation is improved to calculate the axial bending moment function with joint angle amplitude adjustment factor and turn angle adjustment factor. By analyzing the relationship between the forward thrust of the robot and the improved Serpenoid curve equation, a simple, efficient and reliable closed-loop control system was designed. Then, MATLAB and SimWise4D were used for simulation to obtain the motion trajectory of the robot based on the improved Serpenoid curve motion planning algorithm, and the influence of different parameters on the forward velocity of the multi-joint snake robot was analyzed. Finally, the validity of the motion planning algorithm of a multi-joint snake-like robot based on improved Serpenoid curve equation is verified by the actual experiment.

Validation of a low-cost inertial motion capture system for whole-body motion analysis

While some low-cost inertial motion capture (IMC) systems are now commercially available, generally, they have not been evaluated against gold standard optical motion capture (OMC). The objective was to validate the low-cost Neuron IMC system with OMC. Whole-body kinematics were recorded on five healthy subjects during manual handling of boxes for about 32 min while wearing 17 magnetic and inertial measurement units with Optotrak clusters serving as a reference. The kinematical model was calibrated anatomically for OMC and with poses for IMC. Local coordinate systems were aligned with angular velocities to dissociate differences due to technology or kinematical model. Descriptive statistics including the root mean square error (RMSE), coefficient of multiple correlation (CMC) and limits of agreement (LoA) were applied to the joint angle curves. The average technological error yielded 5.8° and 4.9° for RMSE, 0.87 and 0.96 for CMC and 0.4 ± 8.6° and −0.3 ± 6.0° for LoA about the frontal and transverse axes respectively, whereas the longitudinal axis yielded 10.5° for RMSE, 0.78 for CMC and 3.3 ± 13.1° for LoA. Differences due to technology and to the model contributed similarly to the total difference between IMC and OMC. For many joints and axes, RMSE stayed under 5°, CMC over 0.9 and LoA under 10°, especially for the transverse axis and lower limb. The Neuron low-cost IMC system showed potential for tracking complex human movements of long duration in a normal laboratory environment with a certain error level that may be suitable for many applications involving large IMC distribution.

Human knee joint walking pattern generation using computational intelligence techniques

Computational intelligence techniques (CITs) can be used to generate the human knee joint angle walking pattern in the sagittal plane, useful in medical rehabilitation as a specific reference of normal pattern depending on the subject’s age, mass, height and stride duration. In this paper, the knee joint angle reference curves in the sagittal plane were generated by using three different CITs: artificial neural network, extreme learning machine (ELM) and multi-output support vector regression. The gait pattern of a woman is different of the gait pattern of a man, and consequently, their knee joint angle curves are also different. Thus, it was necessary to train and test each of the three CITs for each gender. The data used by the CIT were obtained from volunteers with healthy gait and with different characteristics (gender, age, height and weight). The volunteers’ knee joint angle curves were collected by a system mainly constituted by a treadmill, two web cameras and passive marks positioned at volunteers’ joints. These gait analyses were made for five different walking speeds. It was observed that the best curves for each gender were generated using the ELM. Therefore, the ELM can be used to generate the normal knee joint angle curves expected for any person with specific characteristics (age, mass, height, stride duration), and physicians can use these specific normal curves for comparison purposes instead of using the standard knee joint angle curves of the literature which do not take into consideration the specific characteristics of the joint angle source.

Cluster-based upper body marker models for three-dimensional kinematic analysis: Comparison with an anatomical model and reliability analysis

Quantifying angular joint kinematics of the upper body is a useful method for assessing upper limb function. Joint angles are commonly obtained via motion capture, tracking markers placed on anatomical landmarks. This method is associated with limitations including administrative burden, soft tissue artifacts, and intra- and inter-tester variability. An alternative method involves the tracking of rigid marker clusters affixed to body segments, calibrated relative to anatomical landmarks or known joint angles. The accuracy and reliability of applying this cluster method to the upper body has, however, not been comprehensively explored. Our objective was to compare three different upper body cluster models with an anatomical model, with respect to joint angles and reliability. Non-disabled participants performed two standardized functional upper limb tasks with anatomical and cluster markers applied concurrently. Joint angle curves obtained via the marker clusters with three different calibration methods were compared to those from an anatomical model, and between-session reliability was assessed for all models. The cluster models produced joint angle curves which were comparable to and highly correlated with those from the anatomical model, but exhibited notable offsets and differences in sensitivity for some degrees of freedom. Between-session reliability was comparable between all models, and good for most degrees of freedom. Overall, the cluster models produced reliable joint angles that, however, cannot be used interchangeably with anatomical model outputs to calculate kinematic metrics. Cluster models appear to be an adequate, and possibly advantageous alternative to anatomical models when the objective is to assess trends in movement behavior.

Research on Trajectory Planning of 6-DOF Cutting-robot in Machining Complex Surface

It is important and difficult for the complicated surface processing in mechanical industry. In this paper, an improved algorithm for trajectory planning is proposed in impeller surface processing by using 6-DOF cutting-robot. Taking a single finished path of the impeller blade as an example, the feedrate of the cutter, bow height error, cutter-orientation and position are planned by the B-spline interpolation algorithm, the best cutting trajectory is obtained. On the basis of trajectory planning, the optimal movement scheme of 6-DOF cutting-robot joints is obtained, the 6-DOF cutting-robot feedrate and trajectory smooth transition is achieved and the joints movement adaptive adjustment is completed. Finally, the angles, the angular velocitys of the joints and their interrelated properties are analyzed. The research works indicate that the robot joint angle curves are continuous and stable, which has met the requirements of smooth movement of the robot, and the results show that the trajectory planning is effective and practical.

A NOVEL CABLE-PULLEY UNDERACTUATED LOWER LIMB EXOSKELETON FOR HUMAN LOAD-CARRYING WALKING

Wearable lower limb exoskeleton has comprehensive applications such as load-carrying augmentation, walking assistance, and rehabilitation training by using many active actuators in the joints to reduce the metabolic cost generally. The traditional fully actuated exoskeleton is bulky and requires large energy consumption, and the passive exoskeleton is difficult to provide effective power assistance. To achieve both small number of actuators and good assisting performance, this paper proposes a cable-pulley underactuated principle-based lower limb exoskeleton. The exoskeleton dynamics was modeled and the human-exoskeleton hybrid model was analyzed via ADAMS and LifeMOD to provide an evaluation method for power assistance. By exploiting the control strategy and utilizing the synergies of torque and power assistance, the hip joint and the knee joint can be actuated by a single cable simultaneously. Moreover, the human-exoskeleton co-simulation method was utilized to verify the assisting performance and control effect. In this simulation, the upper toque peak and power required by human are obviously reduced by power assistance and the joint angle curves without exoskeleton are in accordance with the joint angle curves with exoskeleton almost. In conclusion, the designed exoskeleton is compatible with human motion and feasible to provide effective power assistance in load-carrying walking.

Wrist salvage procedures alter moment arms of the primary wrist muscles

BackgroundProximal row carpectomy and scaphoid-excision four-corner fusion are salvage procedures that relieve pain by removing arthritic joint surfaces. While numerous studies have examined how these procedures affect joint motion, few have examined how they influence muscle mechanical actions. This study examines whether muscle moment arms change after these procedures. MethodsMoment arms of primary wrist muscles were measured in 8 cadaveric specimens using the tendon excursion method. In each specimen, moment arms were measured for two degrees of freedom (flexion–extension and radial–ulnar deviation) and three conditions (nonimpaired, scaphoid-excision four-corner fusion, and proximal row carpectomy). For each muscle and degree of freedom, moment arm versus joint angle curves for the three conditions were statistically compared. FindingsWrist salvage procedures significantly alter moment arms of the primary wrist muscles. Proximal row carpectomy primarily alters flexion–extension moment arms, while scaphoid-excision four-corner fusion primarily alters radial–ulnar deviation moment arms. Both procedures also alter the balance between agonist and antagonist wrist muscles. Following proximal row carpectomy, wrist extensors have smaller moment arms in extended postures. Following scaphoid-excision four-corner fusion, radial deviators have larger moment arms throughout radial–ulnar deviation. InterpretationDifferent moment arms indicate that different forces are required to complete the same tasks in nonimpaired and surgically altered wrists. The altered muscle moment arms likely contribute to post-operative impairments. Understanding how salvage procedures alter muscle mechanical actions is a critical first step toward identifying the cause of post-operative impairments and is necessary to develop effective interventions to augment deficient muscles and improve overall function.

Automatic Detection, Extraction, and Analysis of Landing During a Training Session, Using a Wearable Sensor System

We demonstrate an end-to-end wearable inertial sensor-based system for use in a natural sports training environment, which can automatically extract different movement actions and their individual movement cycles to generate and statistically analyse representative joint angle and impact acceleration data. The Discrete Wavelet Transform in conjunction with a Random Forest classifier was able to successfully distinguish between the six training activities (98% accurate). Accurate sensor orientation in 3D space were estimated using a computationally efficient gradient decent algorithm and were utilized to calculate joint angles, which were temporally aligned using curve registration to facilitate inter-participant comparisons. An Analysis of Characterizing Phases was applied to the whole joint angle curve and showed a statistically significant difference in knee joint flexion-extension landing strategy between a participant with low back pain and nine uninjured participants. The presented end-to-end system has the potential to be used in the automatic extraction and analysis of movement technique and loading in various unconstrained environments for musculoskeletal injury management.

A simple method to choose the most representative stride and detect outliers

Kinematic data for gait analysis consists of joint angle curves plotted against percentages of the gait cycle. A typical gait analysis entails repeated measurement of the kinematic data. We present an automatic and computationally inexpensive method to choose the most representative curve and detect outliers amongst repeated curves. The method is based on the notion of depth, where the deepest curve is the equivalent to the median for univariate data. The method applies to single kinematic variable or multi-kinematic variables such as the gait profile. It is sensitive to both shape and position of the curves. A comparison with an existing statistical method is presented as well as an example on one patient's data.

Automatic selection of a representative trial from multiple measurements using Principle Component Analysis

Experimental data in human movement science commonly consist of repeated measurements under comparable conditions. One can face the question how to identify a single trial, a set of trials, or erroneous trials from the entire data set. This study presents and evaluates a Selection Method for a Representative Trial (SMaRT) based on the Principal Component Analysis. SMaRT was tested on 1841 data sets containing 11 joint angle curves of gait analysis. The automatically detected characteristic trials were compared with the choice of three independent experts. SMaRT required 1.4s to analyse 100 data sets consisting of 8±3 trials each. The robustness against outliers reached 98.8% (standard visual control). We conclude that SMaRT is a powerful tool to determine a representative, uncontaminated trial in movement analysis data sets with multiple parameters.

Assessment of anatomical frame variation effect on joint angles: A linear perturbation approach

Although the interpretability and reliability of joint kinematics depends strongly on the accuracy and precision of determining the anatomical frame (AF) orientation, the exact dependency of joint angle error on AF misalignment is still not clear. To fully understand the behavior, this study uses linear perturbations to quantify joint angle error due to known modifications of the AFs, where the joint angles are calculated according to the Cardanic convention. The result is a functional representation of joint angle error with dependence on nominal joint angles and on the orientations of the alternative AFs relative to the nominal AFs. The results are validated using numerical analysis on knee joint angle data during walking. The derived relationship elucidates results from previous work studying this effect and allows AF differences to be inferred by joint angle curves when multiple sets of joint angle curves are collected simultaneously.