Motion Capture Experiments Research Articles

Experimental identification of potential falls in older adult hospital patients

Patient falls within hospitals have been identified as serious but largely preventable incidents, particularly among older adult patients. Previous literature has explored intrinsic factors associated with patient falls, but literature identifying possible extrinsic or situational factors related to falls is lacking. This study seeks to identify patient motions and activities along with associated environmental design factors in a patient bathroom and clinician zone setting that may lead to falls. A motion capture experiment was conducted in a laboratory setting on 27 subjects over the age of seventy using scripted tasks and mockups of the bathroom and clinician zone of a patient room. Data were post-processed using Cortex and Visual3D software. A potential fall was characterized by a set of criteria based on the jerk of the upper body׳s center of mass (COM). Results suggest that only motion-related factors, particularly turning, pushing, pulling, and grabbing, contribute most significantly to potential falls in the patient bathroom, whereas only pushing and pulling contribute significantly in the clinician zone. Future work includes identifying and changing precise environmental design factors associated with these motions for an updated patient room and performing motion capture experiments using the new setup.

ダイビングフィンの性能評価を目的としたシミュレーションモデルの構築

Scuba diving is becoming popular as a leisure activity. Although manufacturers make various types of diving fin, these developments are based on qualitative methods because of the difficulty in estimating the fin efficiency quantitatively. In this research, a simulation model to assess the performance of diving fin was constructed by extending the swimming human simulation model SWUM. In this model, the fin was modeled as a series of five rigid plates. These plates were connected by virtual springs and dampers, and fin’s elasticity was represented by springs. The swimming motion with fins was obtained by motion capture experiment, and the fin parameters such as the shape, the rigidity, and the hydrodynamic coefficient, were determined by comparing the deformation and the drag measurement with the results of simulation. Finally, the diving swimming was simulated, and the swimming speed was found to be about 0.51 m/s. The fluctuations of swimming velocity were found to be 17.8% both in the simulation and the experiment. This consistency suggested the validity of the developed simulation model.

歩幅と進行方向の能動的支援を目的とした片側装着形歩行運動創成機構の開発

This paper discusses a development of an exoskeleton-type walking assist machine having essentially minimum number of joints in order to guarantee the intrinsic safety, simple and inexpensive structure, and can be divided into two pieces so that a part of the apparatus can be detached, when that part becomes unnecessary due to a recovery of body function. Since the obtained mechanism was designed to achieve target human gaits obtained by a number of motion capture experiments, including changings of step lengths and turnings of walking directions. In the determination of the mechanism composition, at first, a most practical composition was chosen among four candidates that were found by taking different selections of possible attachment locations between the device and a human's lower limb into account. Subsequently, the number of joints of the determined composition was synthesized by using only revolute joints so that the device could establish the required DOF for generating the motion of human gait. After that, dimensions of the obtained mechanism were determined through an optimization process considering a minimization of required driving torque which was calculated by a static analysis of the mechanism.

Moving to the Beat: Studying Entrainment to Micro-Rhythmic Changes in Pulse by Motion Capture

Pulse is a fundamental reference for the production and perception of rhythm. In this paper, we study entrainment to changes in the micro-rhythmic design of the basic pulse of the groove in ‘Left & Right’ by D’Angelo. In part 1 of the groove the beats have one specific position; in part 2, on the other hand, the different rhythmic layers specify two simultaneous but alternative beat positions that are approximately 50-80 ms apart. We first anticipate listeners’ perceptual response using the theories of entrainment and dynamic attending as points of departure. We then report on a motion capture experiment aimed at engaging listeners’ motion patterns in response to the two parts of the tune. The results show that when multiple onsets are introduced in part 2, the half note becomes a significant additional level of entrainment and the temporal locations of the perceived beats are drawn towards the added onsets.

Mobile follower robot as an assistive device for home oxygen therapy – evaluation of tether control algorithms

Abstract Home Oxygen Therapy (H.O.T.) is a medical treatment for severe lung diseases in which the patients are supplied concentrated oxygen. This paper investigates the use of a follower robot as a support device for H.O.T. patients, consisting of a two-wheeled differential drive robot connected to the user by tether. Two different control algorithms were studied using dynamic simulation and motion capture experiments with healthy subjects. In further experiments with H.O.T. patients, including a questionnaire survey, it was confirmed that Follow the Leader control was capable of following the user’s trajectory more accurately than Pseudo-Joystick control, and that overall H.O.T. patients showed a preference for Follow the Leader control.

J2340105 ダイビングフィンの性能評価を目的としたシミュレーションモデルの構築

Scuba diving is becoming popular as a leisure activity. Although manufacturers make various types of diving fin, these developments are based on qualitative methods because of the difficulty in estimating the fin effeciency quantitatively. In this research, a simulation model to assess the performance of diving fin was constructed by extending the swimming human simulation model SWUM. In this model, the fin was modeled as a series of five rigid plates. These plates were connected by virtual springs and dampers, and fin's elasticity was represented by springs. The swimming motion with fins was obtained by motion capture experiment, and the fin parameters such as the shape, the rigidity, and the hydrodynamic coefficent, were determined by comparing the deformation and the drag measurement with the result of simulation. Finally, the diving swimming was simulated, and the swimming speed was found to be about 0.85 m/s. The speed was 10% higher compared with the actual diver's speed.

Analysis of hip range of motion in everyday life: a pilot study.

Patients undergoing total hip arthroplasty are increasingly younger and have a higher demand concerning hip range of motion. To date, there is no clear consensus as to the amplitude of the "normal hip" in everyday life. It is also unknown if the physical examination is an accurate test for setting the values of true hip motion. The purpose of this study was: 1) to precisely determine the necessary hip joint mobility for everyday tasks in young active subjects to be used in computer simulations of prosthetic models in order to evaluate impingement and instability during their practice; 2) to assess the accuracy of passive hip range of motion measurements during clinical examination. A total of 4 healthy volunteers underwent Magnetic Resonance Imaging and 2 motion capture experiments. During experiment 1, routine activities were recorded and applied to prosthetic hip 3D models including nine cup configurations. During experiment 2, a clinical examination was performed, while the motion of the subjects was simultaneously captured. Important hip flexion (mean range 95°-107°) was measured during daily activities that could expose the prosthetic hip to impingement and instability. The error made by the clinicians during physical examination varied in the range of ±10°, except for flexion and abduction where the error was higher. This study provides useful information for the surgical planning to help restore hip mobility and stability, when dealing with young active patients. The physical examination seems to be a precise method for determining passive hip motion, if care is taken to stabilise the pelvis during hip flexion and abduction.

Concurrent Prediction of Muscle and Tibiofemoral Contact Forces During Treadmill Gait

Detailed knowledge of knee kinematics and dynamic loading is essential for improving the design and outcomes of surgical procedures, tissue engineering applications, prosthetics design, and rehabilitation. This study used publicly available data provided by the "Grand Challenge Competition to Predict in-vivo Knee Loads" for the 2013 American Society of Mechanical Engineers Summer Bioengineering Conference (Fregly et al., 2012, "Grand Challenge Competition to Predict in vivo Knee Loads," J. Orthop. Res., 30, pp. 503-513) to develop a full body, musculoskeletal model with subject specific right leg geometries that can concurrently predict muscle forces, ligament forces, and knee and ground contact forces. The model includes representation of foot/floor interactions and predicted tibiofemoral joint loads were compared to measured tibial loads for two different cycles of treadmill gait. The model used anthropometric data (height and weight) to scale the joint center locations and mass properties of a generic model and then used subject bone geometries to more accurately position the hip and ankle. The musculoskeletal model included 44 muscles on the right leg, and subject specific geometries were used to create a 12 degrees-of-freedom anatomical right knee that included both patellofemoral and tibiofemoral articulations. Tibiofemoral motion was constrained by deformable contacts defined between the tibial insert and femoral component geometries and by ligaments. Patellofemoral motion was constrained by contact between the patellar button and femoral component geometries and the patellar tendon. Shoe geometries were added to the feet, and shoe motion was constrained by contact between three shoe segments per foot and the treadmill surface. Six-axis springs constrained motion between the feet and shoe segments. Experimental motion capture data provided input to an inverse kinematics stage, and the final forward dynamics simulations tracked joint angle errors for the left leg and upper body and tracked muscle length errors for the right leg. The one cycle RMS errors between the predicted and measured tibia contact were 178 N and 168 N for the medial and lateral sides for the first gait cycle and 209 N and 228 N for the medial and lateral sides for the faster second gait cycle. One cycle RMS errors between predicted and measured ground reaction forces were 12 N, 13 N, and 65 N in the anterior-posterior, medial-lateral, and vertical directions for the first gait cycle and 43 N, 15 N, and 96 N in the anterior-posterior, medial-lateral, and vertical directions for the second gait cycle.

Stooped Postures Are Modified by Pretask Walking in a Simulated Weed-Pulling Task

ABSTRACT Seasonal agricultural workers are hired in some sectors for intermittent manual weed removal, a stoop and grasp harvesting task likely similar to those associated with the high prevalence of musculoskeletal disorders in agriculture. Evaluation of this task in an experimental situation would be useful for identifying and controlling musculoskeletal injury risks, presuming a valid experimental model of the task can be created. The purpose of the present study was to examine how a relevant work-related task, namely prolonged walking, altered the biomechanics of manual weed removal in a laboratory setting. Preliminary field assessments informed the development and analysis of a simulated manual weed removal with two separate conditions: not primed, where 11 participants (4 female, mean age 21.6 years) manually removed a simulated weed six times, and primed, where 23 participants (13 female, mean age 22.1 years) walked 1600 m prior to manually removing the same simulated weed six successive times. Segment end point markers and experimental motion capture were used to determine hip, knee, and ankle angles, as well as toe-target proximity, during weed removal. Significant differences between primed and not primed participants were found for angular displacement at the ankle (t(32) = 5.08, P < .001) and toe-target proximity (t(32) = 2.78, P = .008), where primed participants had increased ankle flexion and a greater distance to the weed, leading to decreased trunk flexion during the harvesting task. These findings suggest that priming can positively influence whole-body postures for manual weed removal.

Optimization-based posture reconstruction for digital human models

Digital human modeling provides a valuable tool for designers when implemented early in the design process. Motion capture experiments offer a means of validation of the digital human simulation models. However, there is a gap between the motion capture experiments and the simulation models, as the motion capture results are marker positions in Cartesian space and the simulation model is based on joint space. Therefore, it is necessary to map the motion capture data to simulation models by employing a posture reconstruction algorithm. Posture reconstruction is an inherently redundant problem where the collective distance error between experimental joint centers and simulation joint centers is minimized. This paper presents an optimization-based method for determining an accurate and efficient solution to the posture reconstruction problem. The procedure is used to recreate 120 experimental postures. For each posture, the algorithm minimizes the distance between the simulation model joint centers and the corresponding experimental subject joint centers which is called the mean measurement error.

Vertical Ground Reaction Forces for Given Human Standing Posture With Uneven Terrains: Prediction and Validation

Ground reaction forces (GRFs) on individual support vary with posture and motion for bipedal mechanisms or systems due to the redundancy in the system. In digital human modeling, specifically posture prediction, the GRFs are predicted, as they are unknown in a virtual environment. Traditionally, models in which the GRFs are predicted have been presented; however, they are always assumed to be on flat ground. Little work has been done to predict the GRFs on uneven or arbitrary terrain. This paper presents a generic method to calculate the vertical GRFs for given standing postures with uneven terrain. The vertical GRFs are predicted based on the generalized forces (torque in revolute joints; force in prismatic joints) calculated using the recursive Lagrangian formulation and a 3-D zero moment point. Motion capture experiments were used to obtain postures for common standing reaching tasks. Force plates were employed to record GRF information for each task. Experimental postures were reconstructed, and the GRF prediction algorithm was used to predict the associated vertical GRFs for each task. Experimental and predicted vertical GRFs are compared to validate the prediction model. The prediction method proved to be valid, with an overall error of 6%.

Effect of human link length determination on posture reconstruction

Motion capture experiment results are often used as a means of validation for digital human simulations. Motion capture results are marker positions and joint centers in Cartesian space. However, joint angles are more intuitive and easy to understand compared to marker or joint center positions. Posture reconstruction algorithms are used to map Cartesian space to joint space by re-creating experimental postures with simulation models. This allows for direct comparison between the experimental results and digital human simulations. Besides the inherent experimental errors from motion capture system, one source of simulation error is the determination of the link lengths to be used in the simulation model. The link length errors can propagate through all simulation results. Therefore, it is critical to eliminate the link length errors. The objective of this study is to determine the best method of determining link lengths for the simulation model to best match the model to the experiment results containing errors. Specifically, the way that the link lengths are calculated in the posture reconstruction process from motion capture data has a significant effect on the recreated posture for the simulation model. Three link length calculation methods (experimental-average method, trial-specific method, and T-pose method) are developed and compared to a benchmark method (frame-specific method) for calculating link lengths. The results indicate that using the trial-specific method is the most accurate method when referring to calculating frame-specific link lengths.

A Wavelet-Based Method to Predict Muscle Forces From Surface Electromyography Signals in Weightlifting

The purpose of this study was to develop a wavelet-based method to predict muscle forces from surface electromyography (EMG) signals in vivo. The weightlifting motor task was implemented as the case study. EMG signals of biceps brachii, triceps brachii and deltoid muscles were recorded when the subject carried out a standard weightlifting motor task. The wavelet-based algorithm was used to process raw EMG signals and extract features which could be input to the Hill-type muscle force models to predict muscle forces. At the same time, the musculoskeletal model of subject's weightlifting motor task was built and simulated using the Computed Muscle Control (CMC) method via a motion capture experiment. The results of CMC were compared with the muscle force predictions by the proposed method. The correlation coefficient between two results was 0.99 ( p<0.01). However, the proposed method was easier and more efficiency than the CMC method. It has potential to be used clinically to predict muscle forces in vivo.

Active tactile sampling by an insect in a step-climbing paradigm.

Many insects actively explore their near-range environment with their antennae. Stick insects (Carausius morosus) rhythmically move their antennae during walking and respond to antennal touch by repetitive tactile sampling of the object. Despite its relevance for spatial orientation, neither the spatial sampling patterns nor the kinematics of antennation behavior in insects are understood. Here we investigate unrestrained bilateral sampling movements during climbing of steps. The main objectives are: (1) How does the antennal contact pattern relate to particular object features? (2) How are the antennal joints coordinated during bilateral tactile sampling? We conducted motion capture experiments on freely climbing insects, using steps of different height. Tactile sampling was analyzed at the level of antennal joint angles. Moreover, we analyzed contact patterns on the surfaces of both the obstacle and the antenna itself. Before the first contact, both antennae move in a broad, mostly elliptical exploratory pattern. After touching the obstacle, the pattern switches to a narrower and faster movement, caused by higher cycle frequencies and lower cycle amplitudes in all joints. Contact events were divided into wall- and edge-contacts. Wall contacts occurred mostly with the distal third of the flagellum, which is flexible, whereas edge contacts often occurred proximally, where the flagellum is stiff. The movement of both antennae was found to be coordinated, exhibiting bilateral coupling of functionally analogous joints [e.g., left head-scape (HS) joint with right scape-pedicel (SP) joint] throughout tactile sampling. In comparison, bilateral coupling between homologous joints (e.g., both HS joints) was significantly weaker. Moreover, inter-joint coupling was significantly weaker during the contact episode than before. In summary, stick insects show contact-induced changes in frequency, amplitude and inter-joint coordination during tactile sampling of climbed obstacles.

Development of discomfort evaluation method for car ingress motion

Recent improvements in the quality of life have led to a consumer need for emotional quality. This need is regarded as extremely important, particularly for products that require a close interaction between products and users and thus that directly lead to product purchase. As a result, research on how to design user-friendly products has become an important task for corporations. Discomfort evaluation in product use has been extensively researched for this purpose. Most of the research concludes that the joint angles of the human body are the main cause of discomfort and propose a discomfort evaluation method based on joint angles. In general, when a person uses great force, they feel discomfort, and the level of discomfort varies depending on the size of the force. Accordingly, it can be inferred that the force acting on the muscle is one of the important causes of discomfort, and research on the correlation between discomfort and muscle forces is needed. In this study, the authors developed a method to evaluate discomfort during ingress into a vehicle to design a side panel for comfortable ingress into a vehicle. The correlation between the muscle forces and discomfort was investigated, and a discomfort evaluation method based on muscle forces was developed. To calculate the muscle forces during the ingress motion, an experimental mock-up of a vehicle was made, and a motion capture experiment during the ingress motion was conducted with various side panel design parameters. The biomechanical simulation tool was used to perform motion simulation based on the motion data obtained. The mathematical correlation between the calculated muscle forces and discomfort was obtained by means of fuzzy logic, and the discomfort evaluation method developed in this study was used to propose a method for designing a comfortable side panel for a vehicle.

Kinematic analysis of over-determinate biomechanical systems

In this paper, we introduce a new general method for kinematic analysis of rigid multi body systems subject to holonomic constraints. The method extends the standard analysis of kinematically determinate rigid multi body systems to the over-determinate case. This is accomplished by introducing a constrained optimisation problem with the objective function given as a function of the set of system equations that are allowed to be violated while the remaining equations define the feasible set. We show that exact velocity and acceleration analysis can also be performed by solving linear sets of equations, originating from differentiation of the Karush–Kuhn–Tucker optimality conditions. The method is applied to the analysis of an 18 degrees-of-freedom gait model where the kinematical drivers are prescribed with data from a motion capture experiment. The results show that significant differences are obtained between applying standard kinematic analysis or minimising the least-square errors on the two fully equivalent 3D gait models with only the way the experimental data is processed being different.

Robotics-based synthesis of human motion

The synthesis of human motion is a complex procedure that involves accurate reconstruction of movement sequences, modeling of musculoskeletal kinematics, dynamics and actuation, and characterization of reliable performance criteria. Many of these processes have much in common with the problems found in robotics research. Task-based methods used in robotics may be leveraged to provide novel musculoskeletal modeling methods and physiologically accurate performance predictions. In this paper, we present (i) a new method for the real-time reconstruction of human motion trajectories using direct marker tracking, (ii) a task-driven muscular effort minimization criterion and (iii) new human performance metrics for dynamic characterization of athletic skills. Dynamic motion reconstruction is achieved through the control of a simulated human model to follow the captured marker trajectories in real-time. The operational space control and real-time simulation provide human dynamics at any configuration of the performance. A new criteria of muscular effort minimization has been introduced to analyze human static postures. Extensive motion capture experiments were conducted to validate the new minimization criterion. Finally, new human performance metrics were introduced to study in details an athletic skill. These metrics include the effort expenditure and the feasible set of operational space accelerations during the performance of the skill. The dynamic characterization takes into account skeletal kinematics as well as muscle routing kinematics and force generating capacities. The developments draw upon an advanced musculoskeletal modeling platform and a task-oriented framework for the effective integration of biomechanics and robotics methods.

Memory-Based Human Motion Simulation for Computer-Aided Ergonomic Design

A novel memory-based motion simulation (MBMS) model was developed as a general framework for simulating natural human motions for computer-aided ergonomic design. The MBMS model utilizes real human motion samples recorded in motion capture experiments as templates for simulating novel motions. Such human motion samples are stored in a motion database. When a user submits an input simulation scenario to the model, a motion search engine termed the ldquoroot motion finderrdquo in the model searches the motion database and retrieves the motion samples that closely match the given scenario. The retrieved motions, referred to as root motions, may significantly differ from one another in the underlying movement technique. Such variability within the root motion set is analyzed and graphically summarized by a model component termed the motion variability analyzer. This analysis helps users rapidly identify alternative movement techniques for the given input simulation scenario and simulate human motions based on alternative movement techniques. Since root motions do not exactly satisfy but only closely match the input simulation scenario, a motion modification (MoM) algorithm adapts them to fit the scenario by systematically deforming them in the joint angle-time domain. The MoM algorithm retains the root motions' fundamental spatial-temporal structure and minimizes deviations from the root motions during such deformations. The MBMS model overcomes limitations of existing simulation models and achieves the following: 1) simulation of categorically different motions based on a single unified model; 2) simple and efficient learning of new motion behaviors; and 3) representation and simulation of human motion variability.

Legless Locomotion: A Novel Locomotion Technique for Legged Robots

We present a novel locomotion strategy called legless locomotion that allows a round-bodied legged robot to locomote approximately when it is high-centered. Typically, a high-centered robot is stuck since the robot's legs do not touch the ground. Legless locomotion uses the legs as a reaction mass to set up oscillatory body rotations which when coupled with ground contact gradually translate the robot. Legless locomotion's continuous dynamics differs from previously studied locomotion methods because of the simultaneous interaction of gravity-induced oscillations, a configuration-dependent system inertia, and non-holonomic contact constraints. This paper employs simple models to capture the complex dynamics and uses the intuition developed from the models to develop gaits that provide planar accessibility. We also present a quantification of leg less locomotion's properties using simulations and motion-capture experiments.

Pedestrian Reactive Navigation for Crowd Simulation: a Predictive Approach

Abstract This paper addresses the problem of virtual pedestrian autonomous navigation for crowd simulation. It describes a method for solving interactions between pedestrians and avoiding inter‐collisions. Our approach is agent‐based and predictive: each agent perceives surrounding agents and extrapolates their trajectory in order to react to potential collisions. We aim at obtaining realistic results, thus the proposed model is calibrated from experimental motion capture data. Our method is shown to be valid and solves major drawbacks compared to previous approaches such as oscillations due to a lack of anticipation. We first describe the mathematical representation used in our model, we then detail its implementation, and finally, its calibration and validation from real data.