Wrist Point Research Articles

Design, optimization, and analysis of a human-machine compatibility upper extremity exoskeleton rehabilitation robot

For rehabilitation therapy robots, the movement range, and comfort of rehabilitation are crucial to the patient’s training and recovery and are also key factors in the design and performance evaluation of rehabilitation robots. In this paper, a highly harmonized upper extremity rehabilitation robot was proposed based on the human-machine coupling system model. Meanwhile, the shoulder joint structure of the rehabilitation robot was optimized to study the workspace range of this robot, the workspace of the upper extremity rehabilitation robot was fitted based on kinematic equations and the workspace volume size for different shoulder joint angles was analyzed. Finally, the upper extremity exoskeleton rehabilitation robot prototype was used to conduct the movement range tracking experiment and human-machine compatibility experiment in healthy volunteers to verify the rehabilitation training range and movement comfort of the rehabilitation robot. The experimental results show that when the optimized upper extremity exoskeleton rehabilitation robot was used to move in the coronal plane and sagittal plane of the human body, the overlaps of the movement range of the upper extremity wrist point W and the movement range of the healthy person was 97.23% and 97.66%, respectively, while the human-machine interaction force generated during the movement was mainly concentrated in the range of 0–10 kPa, which belongs to the low-pressure range of human-machine interaction. Therefore, this upper extremity rehabilitation robot can increase the movement range of patients’ upper extremities and improve the comfort of rehabilitation training.

A Robust Hand Silhouette Orientation Detection Method for Hand Gesture Recognition

The computer vision approach is most widely used for research related to hand gesture recognition. The detection of the image orientation has been discovered to be one of the keys to determine its success. The degree of freedom for a hand determines the shape and orientation of a gesture, which further causes a problem in the recognition methods. This article proposed evaluating orientation detection for silhouette static hand gestures with different poses and orientations without considering the forearm. The longest chord and ellipse were the two popular methods compared. The angles formed from two wrist points were selected as ground truth data and calculated from the horizontal axis. The performance was analyzed using the error values obtained from the difference in ground truth data angles compared to the method's results. The method has errors closer to zero that were rated better. Moreover, the method was evaluated using 1187 images, divided into four groups based on the forearm presence, and the results showed its effect on orientation detection. It was also discovered that the ellipse method was better than the longest chord. This study's results are used to select hand gesture orientation detection to increase accuracy in the hand gesture recognition process.

Excitability Properties of Distal Motor Axons in the Human Ulnar Nerve

Excitability properties at the motor point of the abductor digiti minimi (ADM) muscle were measured using an accelerometer placed on the little finger tip in 31 healthy subjects, and the results were compared with those at the wrist level of the ulnar nerve. ADM motor point stimulation allowed us to demonstrate a significantly shorter strength-duration time constant and smaller threshold changes in deporalizing and hyperpolarizing threshold electrotonus than those at wrist stimulation. At the wrist, hyperpolarizing threshold electrotonus correlated with age (smaller threshold changes), while other excitability indices did not show age-dependent changes at both sites. There were no significant gender differences at these sites. The differences between the wrist and ADM motor point suggest that there are smaller persistent sodium currents and greater inward and outward rectification at the ADM point compared with the wrist. Motor point excitability testing can provide new insights into the pathophysiology of distal motor axons in various peripheral neuropathies and motor disorders.

Upper Limb Deweighting Using Underactuated End-Effector-Based Backdrivable Manipulanda

In rehabilitation for neurological injuries, gravity compensation or deweighting of the upper limb is often performed, as it allows patients with limited muscle activities to realize movements. Deweighting cancels the gravitational effect of the human arm allowing the available muscle forces to produce acceleration, and thus movement of the arm. In robotic devices designed for rehabilitation, deweighting is performed by applying forces to the arm, either joint-by-joint (e.g., with exoskeletons) or at a single point (e.g., with end-effector-based manipulanda). This paper formulates the gravity compensation strategy for spatial (three-dimensional) manipulanda, considers the effect of the force applied by the robotic device on the generalized dynamics of the upper limb and critically evaluates the advantages and limitations of this approach. Additionally, the proposed strategy is validated on the EMU robot, designed with the emphasis on its dynamically transparent mechanical transmission to allow an impedance control approach. The configuration of the EMU robot used in this letter only has 3 degrees of actuation, making it underactuated with respect to the task of regulating a human arm up to the wrist modeled with 4 degrees of freedom. The underactuation resulted in an uncompensated gravity induced moment about the swivel angle axis, which is a line connecting the shoulder and wrist points of the human arm. The experimental validation demonstrates the effectiveness of the proposed gravity compensation technique in cancelling the effect of gravity on the user's arm.

Wrist detection based on a minimum bounding box and geometric features

Wrist detection is a crucial element in the hand-pose estimation and hand-gesture recognition processes in Human-Computer Interaction applications. Most methods use horizontal parallel lines to scan for the location of a wrist line. The challenging problems in wrist detection are determining the orientation and localising the horizontal parallel lines that scan for various hand poses. The proposed method automatically detects a wrist, based on a minimum bounding box and geometric features. It also determines the start and stop points to localise the scanning. The evaluation used a set of 1240 hand images with ground-truth data taken from three sets of data. The hand images contained several gestures and individuals to prove that the method is robust against various gestures. The evaluation shows that the method successfully detects the image orientation and the wrist points with high accuracy.

A robust wrist point detection algorithm using geometric features

In this work, we propose a robust wrist point detection algorithm based on geometric features of the binary hand mask. Circular and elliptical shapes are used to approximate the palm region. Next, a wrist point detection method is proposed. The proposed algorithms are tested on HGR1 database wherein 899 hand gesture images are provided. The experimental results prove that the proposed elliptical method is accurate and effective as compared to the other existing methods. Almost 84% (753 out of 899) of the wrist points are detected accurately with an acceptable error (e < 0.5) for ground truth skin mask of HGR1 database. Out of these 753 accurately detected wrist point 480 belong to error bin e < 0.2. Performance of the proposed method is also tested on real-life scenario wherein skin masks are obtained from different skin detection algorithms. The outcomes are compared with the ground truth skin mask of HGR1 database and comparable results are obtained with multi-seed propagation in multi-layer graph method.

112 THE EFFECT OF TRANSCUTANEOUS LASER BLOOD IRRADIATION UPON CMV/EBV INFECTION AND CHRONIC FATIGUE SYNDROME DEVELOPMENT

The present study examines the effects of auricular transcutaneous electrical nerve stimulation (TENS) on electrical pain threshold measured at the ipsilateral wrist and autonomie functions including skin temperature, blood pressure and pulse rate in 24 healthy subjects. TENS was administered as low frequency trains of pulses delivered at a ‘strong but comfortable’ intensity to 1 of 3 auricular points to be examined: 1.(i) autonomic effects (autonomie point),2.(ii) pain threshold effects (wrist point),3.(iii) placebo effects at an unrelated point (face point). A fourth untreated group was designated as a situation control. The main finding of the study was that auricular TENS produced no significant overall effects on experimental pain threshold or autonomic functions recorded under the present conditions. However, pain threshold was found to increase by over 50% of its pretreatment baseline in 4 subjects and by 30% in 6 subjects. This rise was not dependent upon the site of auricular TENS. The possible mechanisms of such changes are discussed.

The Examination of the Propagation Characteristics of Artery Wave at One Measuring Point

The pulse propagation characteristics of an artery was examined at the both ends of a detouring route. This method uses the parallel structure of arteries, and the characteristics are found using a couple of pulse signals measured at two sides of a suppressed point where the blood flow is stopped. Owing to the closeness of measuring points, this method has the merit of easiness of measurement and the similarity of tissue structure between an artery and skin at measuring points. We made a measuring unit which consists of a couple of pulse wave pickups and a suppressor board between them. Considering the fact that a radial artery and an ulnar artery join at a palmer arch, we set the measuring unit at the wrist point of a radial artery. A delay between two pulse waves measured by the unit because of detour through palmer arch was detected. The result of analyzing two pulse waves shows the effect of aging and blood pressure on delay time as conventional PWV method does. Consequently it is possible that this method can be used for simple measurement of artery conditions.

A kinematic structure-based classification and compact kinematic equations for six-dof industrial robotic manipulators

A kinematic structure-based classification of six degree-of-freedom industrial robotic manipulators is introduced, and a complete set of compact kinematic equations is given according to this classification. For the classification, 100 industrial robots are surveyed. These robots are first classified into main groups and then into subgroups under each main group, and nine kinematic main groups, each having 1–10 subgroups are obtained. The main groups are based on the end-effector rotation matrices and characterized by the twist angles. On the other hand, the subgroups are based on the wrist point positions and characterized by the link lengths and offsets. Compact kinematic equations are derived for all main groups and subgroups by utilizing the properties of exponential rotation matrices, and simplification tools derived by using these properties. Most of these simplified compact equations can be solved analytically and the remaining few of them can be solved semi-analytically through a single univariate equation. In these solutions, the singularities and the multiple configurations of the manipulators can be determined easily. Using these solutions, the inverse kinematics can also be computerized by means of short and fast algorithms.

Simplified dynamics model of planar two-joint arm movements

A theoretical framework is presented that describes a way in which the inverse dynamics equations of motion of planar two-joint arm movements (EX-model) are reformulated in a simple form. A single point was assumed to define both the wrist and elbow joint centers, and thus the motion of two points in extrinsic space was represented by second-order differential equations to provide the variables in the reformulation (RE-) model. Through an analytical processes, it was shown that the RE-model for reproducing the shoulder joint torque consists of the linearly scaled moment per unit mass responsible for accelerating the wrist and elbow points about the shoulder joint, while that for reproducing the elbow joint torque consists of the linearly scaled moment per unit mass responsible for accelerating the wrist point about the elbow. The scaling factors for variables in the RE-model were based solely on the values for segment lengths, while in the EX-model the inertial parameter data for the segments are involved in its representation. The inertial parameter data of six-arm specimens from the cadaver experiment of Chandler et al. (1975, AMRL Technical Report, Wright-Patterson Air Force Base, OH) were used to develop and verify the numeric solutions of the RE-model. The adequacy of the model varied somewhat among subjects, but minor changes of the physical parameters of the arm segments enabled perfect reformulation, regardless of the specimens. The potential abilities of the RE-model to deal with the complexities in motor control with more simple control schemes are discussed.

A method of inverse kinematics solution including singular and multiple configurations for a class of robotic manipulators

A semi-analytical method and an associated computer program are developed for inverse kinematics solution of a class of robotic manipulators, in which four joint variables are contained in the wrist point equations. For this case, it becomes possible to express all the other joint variables in terms of a selected one, and this reduces the inverse kinematics problem to solving a non-linear scalar equation having the selected joint variable as the only unknown. The solution can be obtained by iterative methods and the remaining joint variables can easily be computed by using the solved joint variable. Since the method is manipulator dependent, the equations will be different for kinematically different classes of manipulators, and should be obtained analytically in a similar way as done here, using the suggested algebra based on exponential rotation matrices. A significant benefit of the method is that the singular configurations and multiple solutions indicated by sign ambiguities can be determined while deriving the inverse kinematic expressions. The developed method is applied to a six-revolute-joint industrial robot, FANUC Arc Mate Sr.

Measurement of forearm rotation: The technique, and its reproducibility and validity

Forearm rotation is a point of interest in the study of human movement. For the most part, earlier methods for determining this joint rotation could be applied only in restricted situations. In this paper, a new technique is described, which involves the use of a three-dimensional opto-electronic motion registration system. With only two cameras, the supination angle in almost every position can be determined. A bracelet is attached to the subject’s forearm and fixed to the radius. Wrist points are defined in relation to this bracelet (in its local coordinate system). The properties of the bracelet allow the motion-registration system to calculate its position in the global coordinate system. Given the position of the bracelet, the shoulder, and the elbow, the rotation angle can be determined. The reproducibility (error less than 2o) of and validity of the technique are also discussed.

The effects of auricular transcutaneous electrical nerve stimulation (TENS) on experimental pain threshold and autonomic function in healthy subjects

The present study examines the effects of auricular transcutaneous electrical nerve stimulation (TENS) on electrical pain threshold measured at the ipsilateral wrist and autonomie functions including skin temperature, blood pressure and pulse rate in 24 healthy subjects. TENS was administered as low frequency trains of pulses delivered at a ‘strong but comfortable’ intensity to 1 of 3 auricular points to be examined: 1. (i) autonomic effects (autonomie point), 2. (ii) pain threshold effects (wrist point), 3. (iii) placebo effects at an unrelated point (face point). A fourth untreated group was designated as a situation control. The main finding of the study was that auricular TENS produced no significant overall effects on experimental pain threshold or autonomic functions recorded under the present conditions. However, pain threshold was found to increase by over 50% of its pretreatment baseline in 4 subjects and by 30% in 6 subjects. This rise was not dependent upon the site of auricular TENS. The possible mechanisms of such changes are discussed.