Joint Degrees Of Freedom Research Articles

Detection method of limb movement in competitive sports training based on deep learning

Human posture detection is easily affected by the external environment, resulting in blurred results of limb feature extraction. In order to improve the accuracy and speed of human motion detection, this paper proposes a deep learning-based motion detection method in competitive sports training. The double parallel convolution network algorithm in the depth learning algorithm is used to process the collected action information, extract the body action features, and greatly reduce the operation scale; With the help of the theory of motion mechanics, the mechanical parameters in the motion process are calculated to eliminate outliers and reduce feature dimensions; With the help of motion inertial sensors and joint degrees of freedom, the limb motion detection results are obtained. The experimental results show that the average recognition rate of the method for different motion actions is 99.5%, and the average detection time is 148 ms, with good application performance.

Directional Force Feedback for a 3 DOF Pneumatic Haptic Finger

This paper presents the design, kinematic, and nonlinear control algorithm of a 3 degrees of freedom (DOF) pneumatic haptic finger developed for elastographic imaging virtual palpation. This haptic interface allows for precise tracking of the index finger position and can provide directional force perception at the fingertip. Of the 4 DOF of the human finger, two are kinematically coupled (distal and proximal interphalangeal joints), one DOF of the metacarpophalangeal (MCP) joint is controlled independently, while the remaining MCP joint DOF is only measured. Relationships between the joint angles and actuator positions, as well as fingertip to actuator forces are derived in closed form. A sliding mode nonlinear pneumatic controller is implemented and experimental results are presented.

Impact of Joint Fixation on Postural Dynamics during Single-Leg Stance

We investigated the relationship between the mechanical degrees of freedom (DoF) and its postural dynamics. The joint DoF was fixed to constrain the mechanical DoF. Nine participants were required to perform a single-leg stance task. The center of pressure trajectory data was analyzed. Ankle fixation induced a larger amount of variability in the anteroposterior direction, and less dimensionality and complexity in the mediolateral direction. These results suggest that the ankle joint fixation caused limited postural sway in the mediolateral direction; therefore, functional DoF and complexity decreased. In contrast, it increased the amount of postural sway variability in the anteroposterior direction. Our findings imply a direct relationship between the mechanical DoF of the human movement system and its postural dynamics.

Readout of Parafermionic States by Transport Measurements

Recent experiments have demonstrated the possibility of inducing superconducting pairing into counterpropagating fractional quantum Hall edge modes. This paves the way for the realization of localized parafermionic modes, non-Abelian anyons that share fractional charges in a nonlocal way. We show that, for a pair of isolated parafermions, this joint degree of freedom can be read by conductance measurements across standard metallic electrodes. We propose two complementary setups. We investigate first the transport through a grounded superconductor hosting two interacting parafermions. In the low-energy limit, its conductance peaks reveal their shared fractional charge yielding a three-state telegraph noise for weak quasiparticle poisoning. We then examine the two-terminal electron conductance of a blockaded fractional topological superconductor, which displays a characteristic e/3 periodicity of its zero-bias peaks in the deep topological regime, thus signaling the presence of parafermionic modes.

Constraining Morphologies of Soft Tissues in Extinct Vertebrates Using Multibody Dynamic Simulations: A Case Study on Articular Cartilage of the Sauropod Dreadnoughtus

Rarity of soft tissue preservation, including of articular cartilage, in the fossil record hinders creation of biologically-realistic mechanical models. Previous studies of articular cartilage in extant taxa have documented important aspects of cartilage shapes and thicknesses, but these insights remain generalized and have yet to see systematic implementation in biomechanical modeling. Herein, we present a new method for modeling joints that allows for testing of hypotheses about articular cartilage morphology in extinct taxa. Our case study examines the left elbow joint of the sauropod dinosaurDreadnoughtus schraniusing articular cartilage reconstructions constrained by extant phylogenetic bracketing (EPB). EPB investigations of alligator and chicken articular cartilage revealed the presence of a spherical anterior projection of cartilage on the distal humerus which articulates with the radius during flexion. Importantly, this shape does not directly mirror the underlying bone. Using multibody dynamic models created in Adams™ withouta priorirestrictions on joint degrees of freedom, we simulated the effects of three alternative cartilage reconstructions based on these EPB findings which differ in mediolateral placement of a cartilage sphere and its anteroposterior thickness, encompassing a range of possibilities for the condition inDreadnoughtus. Bone kinematics and contact area (calculated in Geomagic®) were tracked. Additionally, we modeled the elbow of an alligator and turkey using the same methodology and compared the results to XROMM (X-ray Reconstruction of Moving Morphology) analysis of the same limbs. Each model produced distinct results but were generally similar supporting our modeling methodology. Based on these findings, we predict thatDreadnoughtus, and presumably other extinct archosaurs, had a spherical projection of cartilage on the anterior face of the distal end of the humerus for articulation with the radius. Though many valuable insights have been gained by existing modeling methodologies, we chose a different approach that focused on joint contact surfaces. Moreover, applying our methods within a quantitative hypothesis-testing framework can advance the field of paleobiology by testing hypotheses relating shape and kinematics that are not possible with prescribed joint motions.

Biomechanical Assessment of Mobile-Bearing Total Knee Endoprostheses Using Musculoskeletal Simulation

The purpose of this computational study was to analyze the effects of different mobile-bearing (MB) total knee replacement (TKR) designs on knee joint biomechanics. A validated musculoskeletal model of the lower right extremity implanted with a cruciate-retaining fixed-bearing TKR undergoing a squat motion was adapted for three different MB TKR design variants: (I) a commercially available TKR design allowing for tibial insert rotation about the tibial tray with end stops to limit the range of rotation, (II) the same design without end stops, and (III) a multidirectional design with an additional translational degree-of-freedom (DoF) and end stops. When modeling the MB interface, two modeling strategies of different joint topologies were deployed: (1) a six DoF joint as a baseline and (2) a combined revolute-prismatic joint (two DoF joint) with end stops in both DoF. Altered knee joint kinematics for the three MB design variants were observed. The commercially available TKR design variant I yielded a deviation in internal-external rotation of the tibial insert relative to the tray up to 5° during knee flexion. Compared to the multidirectional design variant III, the other two variants revealed less femoral anterior-posterior translation by as much as 5 mm. Concerning the modeling strategies, the two DoF joint showed less computation time by 68%, 80%, and 82% for design variants I, II, and III, respectively. However, only slight differences in the knee joint kinematics of the two modeling strategies were recorded. In conclusion, knee joint biomechanics during a squat motion differed for each of the simulated MB design variants. Specific implant design elements, such as the presence of end stops, can impact the postoperative range of knee motion with regard to modeling strategy, and the two DoF joint option tested accurately replicated the results for the simulated designs with a considerably lower computation time than the six DoF joint. The proposed musculoskeletal multibody simulation framework is capable of virtually characterizing the knee joint dynamics for different TKR designs.

Development of a Shoulder Disarticulation Prosthesis System Intuitively Controlled With the Trunk Surface Electromyogram.

We developed an intuitively operational shoulder disarticulation prosthesis system that can be used without long-term training. The developed system consisted of four degrees of freedom joints, as well as a user adapting control system based on a machine learning technique and surface electromyogram (EMG) of the trunk. We measured the surface EMG of the trunk of healthy subjects at multiple points and analyzed through principal component analysis to identify the proper EMG measurement portion of the trunk, which was determined to be distributed in the chest and back. Additionally, evaluation experiments demonstrated the capability of four healthy subjects to grasp and move objects in the horizontal as well as the vertical directions, using our developed system controlled via the EMG of the chest and back. Moreover, we also quantitatively confirmed the ability of a bilateral shoulder disarticulation amputee to complete the evaluation experiment similar to healthy subjects.

An approach to predict lower-order dynamic behaviors of a 5-DOF hybrid robot using a minimum set of generalized coordinates

• A semi-analytical elastodynamic modeling method of hybrid robots is proposed. • A general stiffness model of multiple DOF passive joints is derived. • The full set of lower-order modes can be predicted with sufficient accuracy. • The effectiveness of the model is validated by FE model and experiment. This paper presents an effective semi-analytical approach for predicting lower-order dynamics of a five degrees-of-freedom (DOF) hybrid robot named TriMule, which is composed of a 3-DOF parallel mechanism plus a 2-DOF A/C wrist. In this method, the governing equations of motion of limbs within the parallel mechanism are first formulated by finite element analysis (FEA) and then reduced to super-element models. This is followed by exploiting a general stiffness model of multiple DOF joints connecting the super-elements. These two threads lead to the reduced dynamic model of the parallel mechanism while keeping the full set of lower-order modes retained. Finally, the dynamic model of entire system is established by merging the models of parallel mechanism and wrist. The computational results show that the lower-order natural frequencies, mode shapes of the entire system, and the frequency response functions (FRFs) of the robot tool center point (TCP) estimated by the proposed approach have very good agreement with those obtained by a full order FE model and experimental modal tests. The merits of this approach lie in that the established model allows the full set of lower-order dynamics of the entire system to be predicted effectively and accurately by only using fourteen generalized coordinates.

Interlimb Parallel-Link Powered Orthosis (IPPO): Compact Wearable Robot With Lateral Weight Bearing Mechanisms for Gait Assistance

Most wearable robots require the additional use of a walking aid for maintenance of balance and bearing the body weight. Although joint degrees of freedom (DOF) in the frontal plane are important for lateral balance, the number of active joint DOFs is also responsible for increase in robot size and weight. The Interlimb Parallel-link Powered Orthosis (IPPO), a newly developed wearable robot with a compact drive mechanism based on the medial system, forms the subject of this paper. IPPO has 9 active DOFs including a mechanism allowing the simultaneous movement of the stance hip adduction and swing hip abduction using one actuator. Two experiments were conducted for a preliminary proof-of-concept study wherein the standing posture center of pressure was evaluated amidst the lateral sway induced by IPPO. We confirmed that our prototype could assist the lateral movement of the user’s body center of mass. In the performance experiment of walking on a treadmill, the results showed that the arm loading forces and arm muscle activities were reduced when the lateral weight bearing was assisted by IPPO. We conclude that the lateral weight bearing mechanism is feasible and effective for reducing arm loading by assisting the lateral weight bearing during walking.

Forward and inverse dynamics modeling of human shoulder-arm musculoskeletal system with scapulothoracic constraint

In this work, we extend the modeling techniques of human shoulder-arm musculoskeletal dynamics by 1) proposing an extended model with 12 joint degrees of freedom and 27 muscles (modeled as 42 musculotendinous actuators) that is capable of most physiologically and anatomically possible movements, 2) proposing a forward dynamics model driven by muscle activation, where the scapulothoracic constraint is formulated as an anatomically consistent force field, and 3) applying the state-of-the-art inverse dynamics solution on this model. We experimentally validate it against electromyograms for 10 activities of daily living. This validated shoulder-arm musculoskeletal model may e.g., serve as a reference plant model in studying human motor control or as part of a human simulator in the future.

Giraffes and hominins: reductionist model predictions of compressive loads at the spine base for erect exponents of the animal kingdom.

ABSTRACTIn humans, compressive stress on intervertebral discs is commonly deployed as a measurand for assessing the loads that act within the spine. Examining this physical quantity is crucially beneficial: the intradiscal pressure can be directly measured in vivo in humans, and is immediately related to compressive stress. Hence, measured intradiscal pressure data are very useful for validating such biomechanical animal models that have the spine incorporated, and can, thus, compute compressive stress values. Here, we use human intradiscal pressure data to verify the predictions of a reductionist spine model, which has in fact only one joint degree of freedom. We calculate the pulling force of one lumped anatomical structure that acts past this (intervertebral) joint at the base of the spine, lumbar in hominins, cervical in giraffes, to compensate the torque that is induced by the weight of all masses located cranially to the base. Given morphometric estimates of the human and australopith trunks, respectively, and the giraffe's neck, as well as the respective structures’ lever arms and disc areas, we predict, for all three species, the compressive stress on the intervertebral disc at the spine base, while systematically varying the angular orientation of the species’ spinal columns with respect to gravity. The comparison between these species demonstrates that hominin everyday compressive disc stresses are lower than those in big quadrupedal animals. Within each species, erecting the spine from being bent forward by, for example, thirty degrees to fully upright posture reduces the compressive disc stress roughly to a third. We conclude that erecting the spine immediately allows the carrying of extra loads of the order of body weight, and yet the compressive disc stress is lower than in a moderately forward-bent posture with no extra load.

Effects of fixation of joint degrees of freedom on the complexity of postural dynamics

Effects of fixation of joint degrees of freedom on the complexity of postural dynamics

A preliminary study on the effects of fixation of joint degrees of freedom on postural fluctuation

A preliminary study on the effects of fixation of joint degrees of freedom on postural fluctuation

Upper Limb Coordination in Individuals With Stroke: Poorly Defined and Poorly Quantified

Background. The identification of deficits in interjoint coordination is important in order to better focus upper limb rehabilitative treatment after stroke. The majority of standardized clinical measures characterize endpoint performance, such as accuracy, speed, and smoothness, based on the assumption that endpoint performance reflects interjoint coordination, without measuring the underlying temporal and spatial sequences of joint recruitment directly. However, this assumption is questioned since improvements of endpoint performance can be achieved through different degrees of restitution or compensation of upper limb motor impairments based on the available kinematic redundancy of the system. Confusion about adequate measurement may stem from a lack a definition of interjoint coordination during reaching. Methods and Results. We suggest an operational definition of interjoint coordination during reaching as a goal-oriented process in which joint degrees of freedom are organized in both spatial and temporal domains such that the endpoint reaches a desired location in a context-dependent manner. Conclusions. In this point-of-view article, we consider how current approaches to laboratory and clinical measures of coordination comply with our definition. We propose future study directions and specific research strategies to develop clinical measures of interjoint coordination with better construct and content validity than those currently in use.

Contribution of interaction torques during dart throwing: Differences between novices and experts

We examined if experts and novices show different utilization of the torque components impulses during dart throwing. Participants threw darts continuously at a dartboard aiming for the centre (target bull’s eye). The upper-limb joint torque impulses were obtained through inverse dynamics with anthropometric and motion capture data as input. Depending on the joint degree of freedom (DOF) and movement phase (acceleration and follow-through), three main strategies of net torque (NET) impulse generation through joint muscle (MUS) and interaction (INT) torque impulses were highlighted. Firstly, our results showed that the elbow flexion–extension DOF leads the movement according to the joint leading hypothesis. Then, considering the acceleration phase, the analysis revealed differences in torque impulse decomposition between expert and novices. For the glenohumeral (GH) joint abduction–adduction and for wrist flexion, the INT torque impulse contributed positively to NET joint torque impulse in the group of experts unlike novices. This allowed to lower the necessary MUS torque impulse at these DOFs. Also, GH axial rotation was actively controlled by muscle torque impulse in the group of experts. During the follow-through, the experts used the INT torque impulse more proficiently than novices to break the elbow extension. The comparison between experts and novices through inverse dynamics document the link between the exploitation of interaction torques impulses and expertise in dart throwing for which the main objective is precision rather than velocity.

Robust Real-Time Musculoskeletal Modeling Driven by Electromyograms.

Current clinical biomechanics involves lengthy data acquisition and time-consuming offline analyses with biomechanical models not operating in real-time for man-machine interfacing. We developed a method that enables online analysis of neuromusculoskeletal function in vivo in the intact human. We used electromyography (EMG)-driven musculoskeletal modeling to simulate all transformations from muscle excitation onset (EMGs) to mechanical moment production around multiple lower-limb degrees of freedom (DOFs). We developed a calibration algorithm that enables adjusting musculoskeletal model parameters specifically to an individual's anthropometry and force-generating capacity. We incorporated the modeling paradigm into a computationally efficient, generic framework that can be interfaced in real-time with any movement data collection system. The framework demonstrated the ability of computing forces in 13 lower-limb muscle-tendon units and resulting moments about three joint DOFs simultaneously in real-time. Remarkably, it was capable of extrapolating beyond calibration conditions, i.e., predicting accurate joint moments during six unseen tasks and one unseen DOF. The proposed framework can dramatically reduce evaluation latency in current clinical biomechanics and open up new avenues for establishing prompt and personalized treatments, as well as for establishing natural interfaces between patients and rehabilitation systems. The integration of EMG with numerical modeling will enable simulating realistic neuromuscular strategies in conditions including muscular/orthopedic deficit, which could not be robustly simulated via pure modeling formulations. This will enable translation to clinical settings and development of healthcare technologies including real-time bio-feedback of internal mechanical forces and direct patient-machine interfacing.

Changes in relative work of the lower extremity joints and distal foot with walking speed

The modulation of walking speed results in adaptations to the lower limbs which can be quantified using mechanical work. A 6 degree-of-freedom (DOF) power analysis, which includes additional translations as compared to the 3 DOF (all rotational) approach, is a comprehensive approach for quantifying lower limb work during gait. The purpose of this study was to quantify the speed-related 6 DOF joint and distal foot work adaptations of all the lower extremity limb constituents (hip, knee, ankle, and distal foot) in healthy individuals. Relative constituent 6 DOF work, the amount of constituent work relative to absolute limb work, was calculated during the stance and swing phases of gait. Eight unimpaired adults walked on an instrumented split-belt treadmill at slow, moderate, and typical walking speeds (0.4, 0.6, and 0.8 statures/s, respectively). Using motion capture and force data, 6 DOF powers were calculated for each constituent. Contrary to previously published results, 6 DOF positive relative ankle work and negative relative distal foot work increased significantly with increased speed during stance phase (p<0.05). Similar to previous rotational DOF results in the sagittal plane, negative relative ankle work decreased significantly with increased speed during stance phase (p<0.05). Scientifically, these findings provide new insight into how healthy individuals adapt to increased walking speed and suggest limitations of the rotational DOF approach for quantifying limb work. Clinically, the data presented here for unimpaired limbs can be used to compare with speed-matched data from limbs with impairments.

On the integration of SIC and MIMO DoF for interference cancellation in wireless networks

Recent advances in MIMO degree-of-freedom (DoF) models allowed MIMO research to penetrate the networking community. Independent from MIMO, successive interference cancellation (SIC) is a powerful physical layer technique used in multi-user detection. Based on the understanding of the strengths and weaknesses of MIMO DoF and SIC, we propose to have DoF-based interference cancellation (IC) and SIC help each other so that (i) precious DoF resources can be conserved through the use of SIC and (ii) the stringent SINR threshold criteria can be met through the use of DoF-based IC. In this paper, we develop the necessary mathematical models to realize the two ideas in a multi-hop wireless network. Together with scheduling and routing constraints, we develop a cross-layer optimization framework with joint DoF IC and SIC. By applying the framework on a throughput maximization problem, we find that SIC and DoF IC can indeed work in harmony and achieve the two ideas that we propose.

DESIGN, FABRICATION, AND TEST OF A NOVEL CLAMPER FOR AORTIC CROSS-CLAMPING IN MINIMALLY INVASIVE CARDIAC SURGERY

One of the main procedures in the most minimally invasive cardiothoracic surgery is clamping the ascending aorta to disconnect the heart from circulation. In this paper, a new aortic clamping instrument which is applicable in minimally invasive cardiac surgery has been presented. The instrument consists of a parallelogram mechanism for opening and closing the jaws, a detachable holder with a two degree of freedom joint that makes the precise position and orientation of the jaws and leaves the clamping component in the patient’s body to make the inserting port free, and a handle for easy manipulation. In vitro test has been performed to evaluate the performance of the clamper compared to the conventional clampers. For this purpose, the force required for aortic cross-clamping and the maximum aortic displacement have been studied in four groups including parallel clamper and conventional clamper with angles of 1[Formula: see text], 2[Formula: see text], and 3[Formula: see text] between jaws, with 10 bovine aorta specimens in each group. These experiments show that the amount of required force for cross-clamping by using the parallel clamper, is statistically significant ([Formula: see text]) compared with the conventional clampers. Also, the increase of angle between jaws makes a significant increase in the percentage of aortic displacement.

DERIVATION AND VALIDATION OF A SPATIAL MULTI-LINK HUMAN POSTURAL STABILITY MODEL

In naval engineering and related disciplines, it is common for dynamic models of the human body to be used in conjunction with quantitative records of body and ship motions, in order to study human balance behaviour while performing various shipboard activities. Research in this area can lead to improvements in ship operations and designs that improve crew safety and efficiency. This paper presents the development of a new spatial 18 degree-of-freedom (DOF)1 ship-inverted pendulum model that incorporates 6 DOF ship motion and 3 DOF joints representing ankle, knee, hip, and neck motions. The derived model is then validated by comparing it to similar models derived using alternative methods but simulated under equivalent input conditions.