scholarly journals Analysis of Upper-Limb and Trunk Kinematic Variability: Accuracy and Reliability of an RGB-D Sensor

2020 ◽  
Vol 4 (2) ◽  
pp. 14
Author(s):  
Alessandro Scano ◽  
Robert Mihai Mira ◽  
Pietro Cerveri ◽  
Lorenzo Molinari Tosatti ◽  
Marco Sacco
Keyword(s):  
Upper Limb ◽  
Gold Standard ◽  
Degrees Of Freedom ◽  
Cost Effective ◽  
Human Motion ◽  
Working Environments ◽  
Wide Range ◽  
Upper Limb Movements ◽  
Clinical Environments ◽  
Point To Point

In the field of motion analysis, the gold standard devices are marker-based tracking systems. Despite being very accurate, their cost, stringent working environments, and long preparation time make them unsuitable for small clinics as well as for other scenarios such as industrial application. Since human-centered approaches have been promoted even outside clinical environments, the need for easy-to-use solutions to track human motion is topical. In this context, cost-effective devices, such as RGB-Depth (RBG-D) cameras have been proposed, aiming at a user-centered evaluation in rehabilitation or of workers in industry environment. In this paper, we aimed at comparing marker-based systems and RGB-D cameras for tracking human motion. We used a Vicon system (Vicon Motion Systems, Oxford, UK) as a gold standard for the analysis of accuracy and reliability of the Kinect V2 (Microsoft, Redmond, WA, USA) in a variety of gestures in the upper limb workspace—targeting rehabilitation and working applications. The comparison was performed on a group of 15 adult healthy subjects. Each subject had to perform two types of upper-limb movements (point-to-point and exploration) in three workspace sectors (central, right, and left) that might be explored in rehabilitation and industrial working scenarios. The protocol was conceived to test a wide range of the field of view of the RGB-D device. Our results, detailed in the paper, suggest that RGB-D sensors are adequate to track the upper limb for biomechanical assessments, even though relevant limitations can be found in the assessment and reliability of some specific degrees of freedom and gestures with respect to marker-based systems.

scholarly journals Clinical Validation of Kinematic Assessments of Post-Stroke Upper Limb Movements with a Multi-Joint Arm Exoskeleton

2020 ◽  
Author(s):  
Florian Grimm ◽  
Jelena Kraugmann ◽  
Georgios Naros ◽  
Alireza Gharabaghi
Keyword(s):  
Clinical Outcome ◽  
Upper Limb ◽  
Convergent Validity ◽  
Degrees Of Freedom ◽  
Clinical Status ◽  
Multiple Regression Model ◽  
Fine Grained ◽  
Starting Position ◽  
Upper Limb Function ◽  
Upper Limb Movements

Abstract Background: Robotic and gravity-balancing exoskeletons, originally designed for the rehabilitation training of neurological patients, are now being increasingly applied in objective and fine-grained sensor-based assessments of upper limb function. However, gravity compensation, inertia and damping properties of the exoskeleton interfere with the natural sensorimotor interaction, proprioceptive and visual feedback during movement execution. This may endanger the validity of the kinematic assessments in relation to the clinical outcome measures that they were supposed to reflect. Here, we appliedMethods: In a proof of concept study involving nineteen severely impaired chronic stroke patients, we assessed sensor-based kinematic data acquired with a multi-joint arm exoskeleton and compared it to the clinical outcome measure Upper Extremity Fugl-Meyer Assessment (UE-FMA) scale. During this assessment, real-time movement feedback of the system’s seven degrees of freedom was provided with a biomorphic 3D virtual representation of the upper limb, including the proximal component of the arm. To align posture and to minimize the exoskeleton-patient interaction, the same position (neutral zero) with a distance of 90 degrees between forearm and upper arm was taken as the starting position for all assessments. Within self-contained tasks, we assessed separately and subsequently the range of motion/spatial posture of four single joints (i.e., joint angles of wrist, elbow, arm, and shoulder movement) and the closing and opening of the hand with a pressure sensor placed in the handle.Results: A strong correlation was observed between wrist and elbow movements within the kinematic parameters (r > 0.7, p<0.003; Bonferroni corrected). A multiple regression model predicted the UE-FMA significantly (F (5, 13) = 12.22, p < 0.0005, adj. R2 = 0.83). Both shoulder rotation and grip pressure added significantly (p < 0.05) to the prediction with the standardized coefficients β of 0.55 and 0.38, respectively.Conclusions: Exoskeleton-based evaluation of single-joint movements and grip force facilitates the assessment of upper limb kinematics after stroke with high structural and convergent validity. Proximal and distal measures may contribute independently to the prediction of the clinical status.

scholarly journals Design and Implementation of a Multi-Function Gripper for Grasping General Objects

2019 ◽  
Vol 9 (24) ◽  
pp. 5266 ◽  
Author(s):  
Long Kang ◽  
Jong-Tae Seo ◽  
Sang-Hwa Kim ◽  
Wan-Ju Kim ◽  
Byung-Ju Yi
Keyword(s):  
Degrees Of Freedom ◽  
Manual Labor ◽  
Cluttered Environments ◽  
Industrial Robotics ◽  
Design And Implementation ◽  
Suction Cup ◽  
Working Environments ◽  
Wide Range ◽  
Pick And Place ◽  
Three Degrees Of Freedom

The development of a reliable pick-and-place system for industrial robotics is facing an urgent demand because many manual-labor works, such as piece-picking in warehouses and fulfillment centers tend toward automation. This paper presents an integrated gripper that combines a linkage-driven underactuated gripper with a suction gripping system for picking up a variety of objects in different working environments. The underactuated gripper consists of two fingers, and each finger has three degrees of freedom that are obtained by stacking one five-bar mechanism over one double parallelogram. Furthermore, each finger is actuated by two motors, both of which can be installed at the base owing to the special architecture of the proposed robotic finger. A suction cup is used to grasp objects in narrow spaces and cluttered environments. The combination of the suction and traditional linkage-driven grippers allows stable and reliable grasping under different working environments. Finally, practical experiments using a wide range of objects and under different grasping scenarios are performed to demonstrate the grasping capability of the integrated gripper.

scholarly journals Wearable upper limb motion assist robot for eating activity

2020 ◽  
Vol 1 (1) ◽  
pp. 1-10
Author(s):  
Uzair Kashtwari ◽  
Norsinnira Zainul Azlan ◽  
Ifrah Shahdad
Keyword(s):  
Upper Limb ◽  
Daily Living ◽  
Degrees Of Freedom ◽  
Low Cost ◽  
Elbow Flexion ◽  
Disabled People ◽  
Flexion Extension ◽  
Feeding Cycle ◽  
The Disabled ◽  
Upper Limb Movements

Many people all around the world are suffering from various types of disabilities and need to depend on others to perform activities of daily living. One of the essential daily living activities is eating. The disabled people should be able to eat their food independently at any time and place, without relying on the caregivers. This paper presents the development of a new wearable upper limb motion assist robot for helping the disabled to eat by themselves. The motion assists robot consists of two degrees of freedom (DOF) movement, focusing on the two most crucial upper limb movements in eating activity, which is the elbow flexion/extension and forearm pronation/supination. A light-weight material was used for the fabrication of the wearable motion assist robot, and Arduino was utilized as the microcontroller. The originality of the study was in terms of the design, operational sequence setting, and kinematic analysis of the wearable upper limb motion assist robot that was explicitly focusing on eating activity. The resulted prototype was portable, compact, light in weight, simple and low cost. The experimental results have proven that the proposed wearable upper limb motion assist robot for eating activity was successful in helping the users to perform the main upper extremity motions in eating. The success rate of the proposed system was 80%, and it took 6 seconds for the system to complete one feeding cycle.

2D Color-Intensity Representation of Ultrasonic Thickness Gauge Measurements

2020 ◽  
pp. 1192-1198
Author(s):  
M.S. Mohammad ◽  
Tibebe Tesfaye ◽  
Kim Ki-Seong
Keyword(s):  
Cost Effective ◽  
The Other ◽  
Thickness Gauge ◽  
Color Intensity ◽  
Digital Readout ◽  
Flat Surfaces ◽  
Video Cameras ◽  
Wide Range ◽  
Cost Effective Alternative ◽  
Ultrasonic Thickness

Ultrasonic thickness gauges are easy to operate and reliable, and can be used to measure a wide range of thicknesses and inspect all engineering materials. Supplementing the simple ultrasonic thickness gauges that present results in either a digital readout or as an A-scan with systems that enable correlating the measured values to their positions on the inspected surface to produce a two-dimensional (2D) thickness representation can extend their benefits and provide a cost-effective alternative to expensive advanced C-scan machines. In previous work, the authors introduced a system for the positioning and mapping of the values measured by the ultrasonic thickness gauges and flaw detectors (Tesfaye et al. 2019). The system is an alternative to the systems that use mechanical scanners, encoders, and sophisticated UT machines. It used a camera to record the probe’s movement and a projected laser grid obtained by a laser pattern generator to locate the probe on the inspected surface. In this paper, a novel system is proposed to be applied to flat surfaces, in addition to overcoming the other limitations posed due to the use of the laser projection. The proposed system uses two video cameras, one to monitor the probe’s movement on the inspected surface and the other to capture the corresponding digital readout of the thickness gauge. The acquired images of the probe’s position and thickness gauge readout are processed to plot the measured data in a 2D color-coded map. The system is meant to be simpler and more effective than the previous development.

Understanding Conformational Entropy in Small Molecules

2020 ◽  
Author(s):  
Lucian Chan ◽  
Garrett Morris ◽  
Geoffrey Hutchison
Keyword(s):  
Small Molecules ◽  
Degrees Of Freedom ◽  
Absolute Error ◽  
Low Energy ◽  
Standard Entropy ◽  
Free Energies ◽  
Conformational Entropy ◽  
Wide Range ◽  
High Degree ◽  
Empirical Corrections

The calculation of the entropy of flexible molecules can be challenging, since the number of possible conformers grows exponentially with molecule size and many low-energy conformers may be thermally accessible. Different methods have been proposed to approximate the contribution of conformational entropy to the molecular standard entropy, including performing thermochemistry calculations with all possible stable conformations, and developing empirical corrections from experimental data. We have performed conformer sampling on over 120,000 small molecules generating some 12 million conformers, to develop models to predict conformational entropy across a wide range of molecules. Using insight into the nature of conformational disorder, our cross-validated physically-motivated statistical model can outperform common machine learning and deep learning methods, with a mean absolute error ≈4.8 J/mol•K, or under 0.4 kcal/mol at 300 K. Beyond predicting molecular entropies and free energies, the model implies a high degree of correlation between torsions in most molecules, often as- sumed to be independent. While individual dihedral rotations may have low energetic barriers, the shape and chemical functionality of most molecules necessarily correlate their torsional degrees of freedom, and hence restrict the number of low-energy conformations immensely. Our simple models capture these correlations, and advance our understanding of small molecule conformational entropy.

The Future of Plasma-Based Surface Engineering Techniques in Tribology (Keynote)

2005 ◽  
Author(s):  
Allan Matthews ◽  
Adrian Leyland
Keyword(s):  
Surface Engineering ◽  
Performance Enhancement ◽  
Bulk Material ◽  
Cost Savings ◽  
Cost Effective ◽  
Ceramic Coatings ◽  
Performance Improvements ◽  
Treatment Techniques ◽  
Wide Range ◽  
Macro Scale

Over the past twenty years or so, there have been major steps forward both in the understanding of tribological mechanisms and in the development of new coating and treatment techniques to better “engineer” surfaces to achieve reductions in wear and friction. Particularly in the coatings tribology field, improved techniques and theories which enable us to study and understand the mechanisms occurring at the “nano”, “micro” and “macro” scale have allowed considerable progress to be made in (for example) understanding contact mechanisms and the influence of “third bodies” [1–5]. Over the same period, we have seen the emergence of the discipline which we now call “Surface Engineering”, by which, ideally, a bulk material (the ‘substrate’) and a coating are combined in a way that provides a cost-effective performance enhancement of which neither would be capable without the presence of the other. It is probably fair to say that the emergence and recognition of Surface Engineering as a field in its own right has been driven largely by the availability of “plasma”-based coating and treatment processes, which can provide surface properties which were previously unachievable. In particular, plasma-assisted (PA) physical vapour deposition (PVD) techniques, allowing wear-resistant ceramic thin films such as titanium nitride (TiN) to be deposited on a wide range of industrial tooling, gave a step-change in industrial productivity and manufactured product quality, and caught the attention of engineers due to the remarkable cost savings and performance improvements obtained. Subsequently, so-called 2nd- and 3rd-generation ceramic coatings (with multilayered or nanocomposite structures) have recently been developed [6–9], to further extend tool performance — the objective typically being to increase coating hardness further, or extend hardness capabilities to higher temperatures.

scholarly journals Gamma models for estimating the odds ratio for a skewed biomarker measured in pools and subject to errors

Biostatistics ◽  
2019 ◽  
Author(s):  
Dane R Van Domelen ◽  
Emily M Mitchell ◽  
Neil J Perkins ◽  
Enrique F Schisterman ◽  
Amita K Manatunga ◽  
...  
Keyword(s):  
Odds Ratio ◽  
Adjusted Odds Ratio ◽  
Lower Cost ◽  
Cost Effective ◽  
Ratio Estimation ◽  
Statistical Efficiency ◽  
Function Model ◽  
Processing Error ◽  
Wide Range ◽  
Pooled Samples

SUMMARYMeasuring a biomarker in pooled samples from multiple cases or controls can lead to cost-effective estimation of a covariate-adjusted odds ratio, particularly for expensive assays. But pooled measurements may be affected by assay-related measurement error (ME) and/or pooling-related processing error (PE), which can induce bias if ignored. Building on recently developed methods for a normal biomarker subject to additive errors, we present two related estimators for a right-skewed biomarker subject to multiplicative errors: one based on logistic regression and the other based on a Gamma discriminant function model. Applied to a reproductive health dataset with a right-skewed cytokine measured in pools of size 1 and 2, both methods suggest no association with spontaneous abortion. The fitted models indicate little ME but fairly severe PE, the latter of which is much too large to ignore. Simulations mimicking these data with a non-unity odds ratio confirm validity of the estimators and illustrate how PE can detract from pooling-related gains in statistical efficiency. These methods address a key issue associated with the homogeneous pools study design and should facilitate valid odds ratio estimation at a lower cost in a wide range of scenarios.

scholarly journals A 4-DOF Upper Limb Exoskeleton for Physical Assistance: Design, Modeling, Control and Performance Evaluation

2021 ◽  
Vol 11 (13) ◽  
pp. 5865
Author(s):  
Muhammad Ahsan Gull ◽  
Mikkel Thoegersen ◽  
Stefan Hein Bengtson ◽  
Mostafa Mohammadi ◽  
Lotte N. S. Andreasen Struijk ◽  
...  
Keyword(s):  
Upper Limb ◽  
Tracking Control ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Mechanical Design ◽  
Trajectory Tracking Control ◽  
Upper Limb Exoskeleton ◽  
And Performance ◽  
Physically Disabled People ◽  
Human Upper Limb

Wheelchair mounted upper limb exoskeletons offer an alternative way to support disabled individuals in their activities of daily living (ADL). Key challenges in exoskeleton technology include innovative mechanical design and implementation of a control method that can assure a safe and comfortable interaction between the human upper limb and exoskeleton. In this article, we present a mechanical design of a four degrees of freedom (DOF) wheelchair mounted upper limb exoskeleton. The design takes advantage of non-backdrivable mechanism that can hold the output position without energy consumption and provide assistance to the completely paralyzed users. Moreover, a PD-based trajectory tracking control is implemented to enhance the performance of human exoskeleton system for two different tasks. Preliminary results are provided to show the effectiveness and reliability of using the proposed design for physically disabled people.

scholarly journals Quantum information probes of charge fractionalization in large-N gauge theories

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Brandon S. DiNunno ◽  
Niko Jokela ◽  
Juan F. Pedraza ◽  
Arttu Pönni
Keyword(s):  
Degrees Of Freedom ◽  
Gauge Theories ◽  
Entanglement Entropy ◽  
Coarse Grained ◽  
Strongly Coupled ◽  
Information Theoretic ◽  
Large N ◽  
Wide Range ◽  
Charge Fractionalization ◽  
Electric Flux

Abstract We study in detail various information theoretic quantities with the intent of distinguishing between different charged sectors in fractionalized states of large-N gauge theories. For concreteness, we focus on a simple holographic (2 + 1)-dimensional strongly coupled electron fluid whose charged states organize themselves into fractionalized and coherent patterns at sufficiently low temperatures. However, we expect that our results are quite generic and applicable to a wide range of systems, including non-holographic. The probes we consider include the entanglement entropy, mutual information, entanglement of purification and the butterfly velocity. The latter turns out to be particularly useful, given the universal connection between momentum and charge diffusion in the vicinity of a black hole horizon. The RT surfaces used to compute the above quantities, though, are largely insensitive to the electric flux in the bulk. To address this deficiency, we propose a generalized entanglement functional that is motivated through the Iyer-Wald formalism, applied to a gravity theory coupled to a U(1) gauge field. We argue that this functional gives rise to a coarse grained measure of entanglement in the boundary theory which is obtained by tracing over (part) of the fractionalized and cohesive charge degrees of freedom. Based on the above, we construct a candidate for an entropic c-function that accounts for the existence of bulk charges. We explore some of its general properties and their significance, and discuss how it can be used to efficiently account for charged degrees of freedom across different energy scales.

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