Joint Coordinates Research Articles

The Effect of Crank Resistance on Arm Configuration and Muscle Activation Variances in Arm Cycling Movements.

Arm cycling on an ergometer is common in sports training and rehabilitation protocols. The hand movement is constrained along a circular path, and the user is working against a resistance, maintaining a cadence. Even if the desired hand trajectory is given, there is the flexibility to choose patterns of joint coordination and muscle activation, given the kinematic redundancy of the upper limb. With changing external load, motor noise and changing joint stiffness may affect the pose of the arm even though the endpoint trajectory is unchanged. The objective of this study was to examine how the crank resistance influences the variances of joint configuration and muscle activation. Fifteen healthy participants performed arm cranking on an arm-cycle ergometer both unimanually and bimanually with a cadence of 60 rpm against three crank resistances. Joint configuration was represented in a 3-dimensional joint space defined by inter-segmental joint angles, while muscle activation in a 4-dimensional "muscle activation space" defined by EMGs of 4 arm muscles. Joint configuration variance in the course of arm cranking was not affected by crank resistance, whereas muscle activation variance was proportional to the square of muscle activation. The shape of the variance time profiles for both joint configuration and muscle activation was not affected by crank resistance. Contrary to the prevailing assumption that an increased motor noise would affect the variance of auxiliary movements, the influence of noise doesn’t appear at the joint configuration level even when the system is redundant. Our results suggest the separation of kinematic- and force-control, via mechanisms that are compensating for dynamic nonlinearities. Arm cranking may be suitable when the aim is to perform training under different load conditions, preserving stable and secure control of joint movements and muscle activations.

Inverse Kinematics Data Adaptation to Non-Standard Modular Robotic Arm Consisting of Unique Rotational Modules

The paper describes the original robotic arm designed by our team kinematic design consisting of universal rotational modules (URM). The philosophy of modularity plays quite an important role when it comes to this mechanism since the individual modules will be the building blocks of the entire robotic arm. This is a serial kinematic chain with six degrees of freedom of unlimited rotation. It was modeled in three different environments to obtain the necessary visualizations, data, measurements, structural changes measurements and structural changes. In the environment of the CoppeliaSim Edu, it was constructed mainly to obtain the joints coordinates matching the description of a certain spatial trajectory with an option to test the software potential in future inverse task calculations. In Matlab, the model was constructed to check the mathematical equations in the area of kinematics, the model’s simulations of movements, and to test the numerical calculations of the inverse kinematics. Since the equipment at hand is subject to constant development, its model can also be found in SolidWorks. Thus, the model’s existence in those three environments has enabled us to compare the data and check the models’ structural designs. In Matlab and SolidWorks, we worked with the data imported on joints coordinates, necessitating overcoming certain problems related to calculations of the inverse kinematics. The objective was to compare the results, especially in terms of the position kinematics in Matlab and SolidWorks, provided the initial joint coordinate vector was the same.

Velocity and acceleration level inverse kinematic calculation alternatives for redundant manipulators

For both non-redundant and redundant systems, the inverse kinematics (IK) calculation is a fundamental step in the control algorithm of fully actuated serial manipulators. The tool-center-point (TCP) position is given and the joint coordinates are determined by the IK. Depending on the task, robotic manipulators can be kinematically redundant. That is when the desired task possesses lower dimensions than the degrees-of-freedom of a redundant manipulator. The IK calculation can be implemented numerically in several alternative ways not only in case of the redundant but also in the non-redundant case. We study the stability properties and the feasibility of a tracking error feedback and a direct tracking error elimination approach of the numerical implementation of IK calculation both on velocity and acceleration levels. The feedback approach expresses the joint position increment stepwise based on the local velocity or acceleration of the desired TCP trajectory and linear feedback terms. In the direct error elimination concept, the increment of the joint position is directly given by the approximate error between the desired and the realized TCP position, by assuming constant TCP velocity or acceleration. We investigate the possibility of the implementation of the direct method on acceleration level. The investigated IK methods are unified in a framework that utilizes the idea of the auxiliary input. Our closed form results and numerical case study examples show the stability properties, benefits and disadvantages of the assessed IK implementations.

Joint Coordination and Stiffness During Landing in Individuals With Chronic Ankle Instability.

The purpose of the present study was to examine the effect of chronic ankle instability (CAI) on lower-extremity joint coordination and stiffness during landing. A total of 21 female participants with CAI and 21 pair-matched healthy controls participated in the study. Lower-extremity joint kinematics were collected using a 7-camera motion capture system, and ground reaction forces were collected using 2 force plates during drop landings. Coupling angles were computed based on the vector coding method to assess joint coordination. Coupling angles were compared between the CAI and control groups using circular Watson-Williams tests. Joint stiffness was compared between the groups using independent t tests. Participants with CAI exhibited strategies involving altered joint coordination including a knee flexion dominant pattern during 30% and 70% of their landing phase and a more in-phase motion pattern between the knee and hip joints during 30% and 40% and 90% and 100% of the landing phase. In addition, increased ankle inversion and knee flexion stiffness were observed in the CAI group. These altered joint coordination and stiffness could be considered as a protective strategy utilized to effectively absorb energy, stabilize the body and ankle, and prevent excessive ankle inversion. However, this strategy could result in greater mechanical demands on the knee joint.

Error Compensation Heatmap Decoding for Human Pose Estimation

As a fundamental component of heatmap-based human pose estimation methods, heatmap decoding is to transform heatmaps into joint coordinates. We found that previous heatmap decoding methods generally ignored the effect of systematic errors introduced by the resolution increaseing operations in the network decoder. This work fills the gap by taking the systematic errors in heatmap decoding into consideration. We proposed a fast method to reduces the systematic and random errors in one shot by error compensation. The proposed method outperforms the previous best method on the COCO and the MPII datasets while being over 2 times faster. Extensive experiments with different networks, resolutions, metrics and datasets have proved the rationality of the proposed idea.

Computer Vision Based Robotic Arm Controlled Using Interactive GUI

This paper presents the design and implementation of a robotic vision system operated using an interactive Graphical User Interface (GUI) application. As robotics continue to become a more integral part of the industrial complex, there is a need for automated systems that require minimal to no user training to operate. With this motivation in mind, the system is designed so that a beginner user can operate the device with very little instruction. The application allows users to determine their desired object, which will be picked up and placed by a robotic arm into the target location. The application allows users to filter objects based on color, shape, and size. The filtering along the three parameters is done by employing a Hue-Saturation-Value (HSV) mode color detection algorithm, shape detection algorithm, size determining algorithm. Once the target object is identified, a centroid detection algorithm is employed to find the object’s center coordinates. An inverse kinematic algorithm is used to ascertain the robotic arm’s joint positions for picking the object. The arm then goes through a set of preset positions to pick up the object, place the object, and then return the arm to the initial position. The joint coordinates are forwarded to a microcontroller that sets the arm’s joint angle at each position.

Controlling mechanical arms using 3D coordinates gotten from the AR technology

How to control the movement of the mechanical arm is a challenging topic recently. It requires much time and energy to program every joint. This paper proposes a new method based on 3D coordinates of the human arm joints, which helps the mechanical arm to imitate the movement of human arms and only needs to calculate angles of human arms’ joints according to the 3D coordinates. Here in this process the key is to get the information of 3D coordinates of human arms. This paper applies an AR (Augmented Reality) application of body detection with LiDAR on iPad Pro 2020 to get 3D coordinates. Then the calculated angle information is transferred from the host computer to the Arduino board controlling the movement of the mechanical arm. Eventually the same movements will be made by the mechanical arm and the human arm.

The Effects of Gaze Direction on the Stability and Coordination of the Lower Limb Joint during Drop-Landing

The Effects of Gaze Direction on the Stability and Coordination of the Lower Limb Joint during Drop-Landing

Physical Fatigue Detection From Gait Cycles via a Multi-Task Recurrent Neural Network

This paper describes a deep learning approach to classify physically fatigued and non-fatigued gait cycles via a recurrent neural network (RNN), where each gait cycle is represented as a time series of three-dimensional coordinates of body joints. Gait cycles inherently have large intra-class variations caused by gait stance differences (e.g., which foot is supporting/swinging) at the beginning of each gait cycle, which makes it difficult to identify subtle differences induced by fatigue. To overcome these difficulties, we introduce a supporting foot-aware RNN model in a multi-task learning framework for better fatigue detection. More specifically, the RNN model has two branches of layers: one is assigned to the main task of fatigue classification and the other is assigned to the auxiliary task of estimating the first supporting foot in the gait cycles. We collected physically fatigued and non-fatigued gait cycles from eight subjects and conducted experiments to evaluate the accuracies of the proposed multi-task model in comparison to a single-task model. As a result, the proposed method achieved an overall area under curve (AUC) of 0.860 for fatigue classification in a leave-one-subject-out cross-validation, and an AUC of 0.915 in a leave-one-day-out evaluation. It can be concluded from the experimental results that a fatigue detection system for daily use, especially for screening purposes, is very feasible on the basis of the proposed approach.

ВІЙСЬКОВИЙ ПОТЕНЦІАЛ РЕГІОНАЛЬНИХ ОБ’ЄДНАНЬ

At the beginning of the third decade of the 21st century, large-scale interna-tional conflicts and wars between groups of individuals, unrecognized international actors and countries continue to unfold. In the context of globalization, the issue of forming and strengthening the military potential of the country largely depends on its international integration policy and participation in regional alliances. Relations between the members of regional organizations are formed in the spheres of trade, finance, technical and political cooperation, among which the most important issue is military cooperation, which strengthens their military potential on the world stage. The study found that in existing regional organizations, the degree of military interaction between countries differs significantly. The authors grouped regional organizations according to the power of military cooperation into three groups. The first group is regional integration organizations that do not have joint military forces, military programs and coordination structures. This group includes the vast majority of regional organizations. The second group is regional integration organizations, which have a small amount of military cooperation, conduct joint military exercises, carry out force programs and are able to solve problems with a consolidated military force. This group includes and studied: Union of South American Nations (UNASUR), Association of Southeast Asian Nations (ASEAN), Shanghai Cooperation Organization (SCO), Economic Community of West Africa (ECOWAS), Southern African Development Community (SADC), African Union (AU). The third group is regional alliances, which have a strong military potential. These integration organizations have: an extensive system of international agreements; unified standards; joint military units; joint development programs; coordinating structures; carry out joint exercises and military operations. This group includes: North Atlantic Treaty Organization (NATO), Commonwealth of Independent States (CIS), European Union (EU). Based on the author's analysis of the military potential of regional organizations, recommendations for countries have been developed. For the countries of the first group it is necessary to determine the expediency of strengthening the military potential of the country by strengthening the integration process: within the membership of existing integration organizations; joining other integration organizations; creation of new integration organizations. For the countries of the second group, it is advisable to continue to support military formations, increase spending on the protection and defense of life and health of their citizens from terrorist groups and other illegal actions that may endanger the government and civilians. For the countries of the third group it is recommended to maintain cooperation in the military sphere, to increase the costs of improving military equipment and weapons. Conduct more joint exercises to gain new experience and skills in different conditions of use of military resources in civilian and military spheres. These most powerful regional alliances have an advantage in the military field precisely because of the number of troops, the number of weapons, military equipment, and joint military bases. And the main goal of these regional organizations is to create security for their citizens and the world as a whole, through the development of new effective mechanisms for global interaction.

A Brief History of the American National Standards Institute (ANSI) C63.4 Standard

In the early days of radio broadcasting, there were interference problems with radio reception due to “radio noise.” Several coordinating committees were formed to address the problems. The most prominent one was formed in 1931 and it was called the EEI-NEMA-RMA Joint Coordination Committee on Radio Reception. (Note: EEI is the Edison Electric Institute, NEMA is the National Electrical Manufacturer's Association, and RMA is the Radio Manufacturers Association.)

3D Hand Pose Estimation via Graph-Based Reasoning

Hand pose estimation from a single depth image has recently received significant attention owing to its importance in many applications requiring human–computer interaction. The rapid progress of convolutional neural networks (CNNs) and technological advances in low-cost depth cameras have greatly improved the performance of the hand pose estimation method. Nevertheless, regressing joint coordinates is still a challenging task due to joint flexibility and self-occlusion. Previous hand pose estimation methods have limitations in relying on a deep and complex network structure without fully utilizing hand joint connections. A hand is an articulated object and consists of six parts that represent the palm and five fingers. The kinematic constraints can be obtained by modeling the dependency between adjacent joints. This paper proposes a novel CNN-based approach incorporating hand joint connections to features through both a global relation inference for the entire hand and local relation inference for each finger. Modeling the relations between the hand joints can alleviate critical problems for occlusion and self-similarity. We also present a hierarchical structure with six branches that independently estimate the position of the palm and five fingers by adding hand connections of each joint using graph reasoning based on graph convolutional networks. Experimental results on public hand pose datasets show that the proposed method outperforms previous state-of-the-art methods. Specifically, our method achieves the best accuracy compared to state-of-the-art methods on public datasets. In addition, the proposed method can be utilized for real-time applications with an execution speed of 103 fps in a single GPU environment.

Political prospects of the EAEU as a union of states within the framework of the concept of «Greater Eurasia»

The focus of this article is on the problem of political integration of the EAEU member States. The need for joint coordination of the political efforts of the members of the Union is due to the challenges of modern economic and political development of states in the context of the formation of a multipolar world. The article highlights possible ways to expand membership in the EAEU. The prospect of the development of the Eurasian Economic Union from a purely economic to a political one, that is, into a Eurasian Union, is outlined.

Naučnici i kulturna diplomatija Srbije

Based on a research study (Questionnaire Scientists and Cultural (Scientific) Diplomacy of Serbia, conducted among employees in research, scientific and teaching positions at faculties and institutes in the Republic of Serbia from November 1-15, 2021), analysis of available documents of the Ministry of Education, Science and Technological Development of the Republic of Serbia, as well as literature, the paper analyzes the place and the role of scientists (scholars) in the cultural (scientific) diplomacy of Serbia. Recalling the historical significance of scientists in the political and social development of Serbia since the beginning of building a modern Serbian statehood, the place of scientists in society is emphasized and the possibilities to apply good examples in the present are analyzed as well. Based on data on the participation of Serbian scientists in international projects and networking with scientists in Europe and the world, the paper will provide recommendations for better use of these ties in (re)positioning Serbia in bilateral and multilateral relations. The paper presents current attitude of scientists in Serbia on the need and importance of cultural (scientific) diplomacy to answer the following questions: How many of them participated in cultural-diplomatic actions? Do they perceive themselves as actors of cultural (scientific) diplomacy? In what ways Serbian cultural diplomacy can be organized? Finally, this paper, in addition to analyzing the possibilities and scope of engaging scientists to promote Serbia and its interests in international relations, also gives specific recommendations for strengthening and developing cultural diplomacy of Serbia. International projects, conferences, guest appearances and study stays are an excellent training ground for improving and presenting results, as well for establishing contacts and connections, but they also can and must be developed into a powerful tool of Serbian public diplomacy. The results of this research showed that a significant part of Serbian scientists have a clear awareness of their role in scientific and cultural exchange, as well as that they have a desire to participate in it. This, along with the scientific elite of this country in the diaspora, is a huge untapped potential of Serbia. This potential has to be systematically organized and shaped in accordance with the goals of Serbian diplomacy. It is very important that actors of cultural (scientific) diplomacy and useful individuals be recognized and financially supported, which should be followed by better coordination design of activities of the Ministry of Foreign Affairs, the Ministry of Culture and the Ministry of Education, Science and Technological Development. Cross-sectoral cooperation can be strengthened through joint coordination bodies or by building a system of institutions that would deal with: (additional) education of new staff (master studies, specialized courses in cultural and scientific diplomacy), lifelong learning of existing staff in diplomacy or recruitment of experts in certain fields, with a single list (base) of potential experts, who would create proposals for the development of diplomatic strategies and / or, if necessary, be sent abroad for longer or shorter missions.

Differentiable Spatial Regression: A Novel Method for 3D Hand Pose Estimation

3D Hand pose estimation from a single depth image is an essential topic in computer vision and human-computer interaction. Although the rising of deep learning method boosts the accuracy a lot, the problem is still hard to solve due to the complex structure of the human hand. Existing methods with deep learning either lose spatial information of hand structure or lack a direct supervision of joint coordinates. In this paper, we propose a novel Pixel-wise Regression method, which use spatial-form representation (SFR) and differentiable decoder (DD) to solve the two problems. To use our method, we build a model, in which we design a particular SFR and its correlative DD which divided the 3D joint coordinates into two parts, plane coordinates and depth coordinates and use two modules named Plane Regression (PR) and Depth Regression (DR) to deal with them respectively. We conduct an ablation experiment to show the method we proposed achieve better results than the former methods. We also make an exploration on how different training strategies influence the learned SFRs and results. The experiment on three public datasets demonstrates that our model is comparable with the existing state-of-the-art models and in one of them our model can reduce mean 3D joint error by 25%.

Effects of acute wearable resistance loading on overground running lower body kinematics.

Field-based sports require athletes to run sub-maximally over significant distances, often while contending with dynamic perturbations to preferred coordination patterns. The ability to adapt movement to maintain performance under such perturbations appears to be trainable through exposure to task variability, which encourages movement variability. The aim of the present study was to investigate the extent to which various wearable resistance loading magnitudes alter coordination and induce movement variability during running. To investigate this, 14 participants (three female and 11 male) performed 10 sub-maximal velocity shuttle runs with either no weight, 1%, 3%, or 5% of body weight attached to the lower limbs. Sagittal plane lower limb joint kinematics from one complete stride cycle in each run were assessed using functional data analysis techniques, both across the participant group and within-individuals. At the group-level, decreases in ankle plantarflexion following toe-off were evident in the 3% and 5% conditions, while increased knee flexion occurred during weight acceptance in the 5% condition compared with unloaded running. At the individual-level, between-run joint angle profiles varied, with six participants exhibiting increased joint angle variability in one or more loading conditions compared with unloaded running. Loading of 5% decreased between-run ankle joint variability among two individuals, likely in accordance with the need to manage increased system load or the novelty of the task. In terms of joint coordination, the most considerable alterations to coordination occurred in the 5% loading condition at the hip-knee joint pair, however, only a minority of participants exhibited this tendency. Coaches should prescribe wearable resistance individually to perturb preferred coordination patterns and encourage movement variability without loading to the extent that movement options become limited.

Augmented Lagrangian index-3 semi-recursive formulations with projections

MBSLIM (Multibody Systems at Laboratorio de Ingenieria Mecanica) multibody library includes some global formulations for the dynamics and sensitivity analysis of multibody systems. The extension of the library to accommodate topological formulations in relative (joint) coordinates and their implementation are going to be described in two separate works, this one being devoted to dynamics and the second one to a sensitivity analysis. With this extension in the scope, some topological semi-recursive formulations derived in the past are revisited, generalized and reformulated. The need for generalization of the previously published formulations was detected because the equations proposed were not general enough to be integrated in an all-purpose multibody library in natural coordinates like MBSLIM, especially because both set of coordinates need to coexist, the definition of the mechanisms has to be the original one and the library has to be automatic and all the existing models have to work with the new approach. Moreover the new solver takes advantage of some problems solved in natural coordinates, like the initial position and initial velocity problems for closed-loop systems. Finally, to test the new equations, two benchmark problems are presented and their results compared: a spatial slider–crank mechanism and a buggy vehicle model.

ASSESSING THE POTENTIAL INFLUENCE OF DIFFERENT WALKING STRATEGIES ON PLANTAR PRESSURE DISTRIBUTION TRIGGERED BY A PORTABLE BIOFEEDBACK-BASED GAIT TRAINING DEVICE

Plantar pressure refers to the interfacial contact pressure between the foot and the supporting surface during daily locomotor activities. Information derived from plantar pressure measures is essential in gait and posture research for diagnosing patho-mechanics associated with the musculoskeletal diseases. In particular, it is compulsory to reduce the abnormally high plantar pressure in people with diabetes for the prevention and treatment of foot ulcerations in this population. In this study, a portable biofeedback-based gait training device is developed to advocate able-bodied subjects to adopt different movement patterns in walking to manipulate the plantar pressure distribution under the foot. Through the simultaneous detection of the plantar pressure pattern and the kinematics of the lower extremity joints, it was revealed that the unloading effects for the plantar site in particular to the lateral forefoot subareas were more abundant through biofeedback-assisted gait alterations than the self-awareness control for gait adjustment. In addition, the corresponding relationship between joint coordination and pressure redistribution pattern was obtained, which could potentially be used in gait retraining interventions to correct abnormal plantar pressure patterns in people with diabetes.

David Hume, economic rationality, and policy: Symposium introduction

Abstract This is an introduction to the symposium, David Hume, Economic Rationality, and Policy. Topics treated in the symposium include the idea of true preferences; Hume's theory of preferences in relation to his economic philosophy; justice and markets as a joint coordination regime; the instability of general, inflexible rules; conservatism and liberalism; the ethics of policy innovation; Hume and classical economics; group analytics and contemporary political sociology.

Gateway Configuration for Rapid Pick-and-Place Operations of 2-Degrees-of-Freedom Parallel Robots

Abstract This article presents a new assembling for 2 degrees-of-freedom (DOFs) parallel robots for executing rapid pick-and-place operations with low energy consumption. A conventional design of 2-DOF parallel robots is based on five-bar mechanisms. Collisions between links are highly possible, restricting the end-effector workspace and/or increasing the trajectory time to avoid collisions. In this article, an alternative assembling for preventing collisions is presented. This novel assembling allows exploring the difference between the four five-bar mechanism configurations for the same position of the end-effector. Some of these configurations yield to lower time and/or lower energy consumption for the same motorization. First, a dynamic model of the robot has been developed using matlab® and simulink® and validated by comparison with the results obtained by adams® software. A robust cascade PD regulator for controlling joint coordinates has been tuned providing a high accurate end-effector positioning. Finally, simulation results of four configurations are presented for executing controlled maneuvers. The obtained results demonstrate that the conventional configuration is the worst one in terms of trajectory time or energy consumption and, conversely, the best one corresponds to an uncommonly used configuration. A workspace map where all configurations provide faster maneuvers has been obtained in terms of Jacobian matrix and mechanism elbows distance. The results presented here allow designing a rapid manipulator for pick-and-place operations.