Optimization of Stiffness and Damping in Modeling of Voluntary Elbow Flexions

2011 ◽  
Author(s):  
Kai Chen ◽  
Richard Foulds
Keyword(s):  
Arm Movement ◽  
Random Order ◽  
Influential Factors ◽  
Emg Activity ◽  
Control Parameters ◽  
Skeletal System ◽  
Time Duration ◽  
Control Signals ◽  
Stiffness And Damping ◽  
Virtual Trajectory

A subsequent study of obstructed voluntary arm movement extended the relative damping concept, and incorporated the influential factors of the mechanical behavior of the neural, muscular and skeletal system in the control and coordination of arm posture and movement. A significant problem of the study is how this information should be used to modify control signals to achieve desired performance. This study used an Equilibrium Point Hypothesis (EPH) model to examine changes of controlling signals for arm movements in the context of adding perturbation/load in the form of forces/torques. The mechanical properties and reflex actions of muscles of the elbow joint were examined. Brief unexpected torque/force pulses of identical magnitude and time duration were introduced at different stages of the movement in a random order by a pre-programmed 3 degree of freedom (DOF) robotic arm (MOOG FCS HapticMaster). Key to this research is the optimization of B and K for each subject based on their HM only experimental data. The results shown in each of sections confirm that those parameters. Along with an EMG determined VT can be used successfully to model the perturbed trials. The results also show that the subjects may maintain the same control parameters (virtual trajectory, stiffness and damping) regardless of added perturbations that cause substantial changes in EMG activity and kinematics.

The Mechanics of Perturbed Upper Limb Movement Control

2010 ◽  
Author(s):  
Kai Chen ◽  
Richard A. Foulds
Keyword(s):  
Upper Limb ◽  
Muscle Length ◽  
Movement Control ◽  
Elbow Flexion ◽  
Influential Factors ◽  
Least Square ◽  
Movement Trajectory ◽  
Time Duration ◽  
Inverse Dynamic ◽  
Control Signals

The dependence of muscle force on muscle length gives rise to a “spring - like” behavior which has been shown to play an important role during movement. This study extended this concept and incorporated the influential factors of the mechanical behavior of the neural, muscular and skeletal system on the control of elbow movement. A significant question in motor control is determining how information about movement is used to modify control signals to achieve desired performance. One theory proposed and supported by Feldman et. is the equilibrium point hypothesis (EPH). In it the central nervous system (CNS) reacts to movement as a shift of the limb’s equilibrium posture. The EPH drastically simplified the requisite computations for multi-joint movements and mechanical interactions with complex dynamic objects in the context. Because the neuromuscular system is spring-like, the instantaneous difference between the arm’s actual position and the equilibrium position specified by the neural activity can generate the requisite torques, avoiding the complex “inverse dynamic” of computing the torques at the joints. Moreover, this instantaneous difference serves as a potential source of movement control related to limb dynamics and associated movement-dependent torques when perturbations are added. In this paper, we have used an EPH model to examine changes to control signals for arm movements in the context of adding perturbations in format of forces or torques. The mechanical properties and reflex actions of muscles crossing the elbow joint were examined during a planned 1 radian voluntary elbow flexion movement. Brief unexpected torque/force pulses of identical magnitude and time duration (4.5 N flexion switching to 50 N extension within 120ms) were introduced at various points of a movement in randomly selected trials. Single perturbation was implemented in different trials during early, mid, stages of the movement by pre-programmed 6DOF robotic arm (MOOG FCS HapticMaster). Changes in movement trajectory induced by a torque/ force perturbation determined over the first 120 ms by a position prediction formulation, and then a modified and optimization K-B-I (stiffness-damping-inertia) model was fit to the responses for predicting both non-perturbed and perturbed movement of elbow. The stiffness and damping coefficients estimate during voluntary movements were compared to values recorded of different subjects during trials. A least square nonlinear optimization model was designed to help determine the optimized impedance a subject could generate, and the identified of adapted of K-B-I in perturbed upper limb movements confirmed our assumption.

scholarly journals Determination of emergency roads to emergency accommodation using loss analysis results

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Sajad Ganjehi ◽  
Khadijeh Norouzi Khatiri
Keyword(s):  
Estimation Method ◽  
Emergency Evacuation ◽  
Influential Factors ◽  
Urban Crisis ◽  
Time Duration ◽  
Loss Analysis ◽  
Expert Choice ◽  
Data Layers ◽  
Temporary Accommodation

AbstractTeh present study aims to identify proper places to build temporary accommodation for people and accessible roads using damage analysis results during a probable earthquake. Teh HAZUS damage estimation method, which is one of teh most common ones currently used in teh world, was used in dis study. Teh influential factors in locating teh temporary accommodation in Shiraz were studied by using damage results, AHP model, and Expert Choice software. Then, map for temporary accommodation was prepared. By integrating layers, teh ultimate map of optimal locating for temporary accommodation was presented. Subsequently, all teh parameters influencing teh safety of emergency evacuation and relief network were identified and teh impact rate of each one was determined based on experts’ opinions through AHP. Based on teh importance of each index, roads were weighed and coded. Then, teh optimal safe road for relief and emergency evacuation was proposed. Teh results suggested dat relief roads are different based on different indices and teh optimal road was obtained through overlapping teh data layers according to teh importance of each parameter. dis optimal road could provide maximum services in teh minimum time duration and subsequently create capacity building in urban crisis management.

scholarly journals Compensation for Interaction Torques During Single- and Multijoint Limb Movement

1999 ◽  
Vol 82 (5) ◽  
pp. 2310-2326 ◽  
Author(s):  
Paul L. Gribble ◽  
David J. Ostry
Keyword(s):  
Human Subjects ◽  
Emg Activity ◽  
Interaction Torque ◽  
Control Signals ◽  
Shoulder Muscles ◽  
Multijoint Movements ◽  
Movement Parameters ◽  
Shoulder Kinematics ◽  
Interaction Torques ◽  
Elbow Motion

During multijoint limb movements such as reaching, rotational forces arise at one joint due to the motions of limb segments about other joints. We report the results of three experiments in which we assessed the extent to which control signals to muscles are adjusted to counteract these “interaction torques.” Human subjects performed single- and multijoint pointing movements involving shoulder and elbow motion, and movement parameters related to the magnitude and direction of interaction torques were manipulated systematically. We examined electromyographic (EMG) activity of shoulder and elbow muscles and, specifically, the relationship between EMG activity and joint interaction torque. A first set of experiments examined single-joint movements. During both single-joint elbow ( experiment 1) and shoulder ( experiment 2) movements, phasic EMG activity was observed in muscles spanning the stationary joint (shoulder muscles in experiment 1 and elbow muscles in experiment 2). This muscle activity preceded movement and varied in amplitude with the magnitude of upcoming interaction torque (the load resulting from motion of the nonstationary limb segment). In a third experiment, subjects performed multijoint movements involving simultaneous motion at the shoulder and elbow. Movement amplitude and velocity at one joint were held constant, while the direction of movement about the other joint was varied. When the direction of elbow motion was varied (flexion vs. extension) and shoulder kinematics were held constant, EMG activity in shoulder muscles varied depending on the direction of elbow motion (and hence the sign of the interaction torque arising at the shoulder). Similarly, EMG activity in elbow muscles varied depending on the direction of shoulder motion for movements in which elbow kinematics were held constant. The results from all three experiments support the idea that central control signals to muscles are adjusted, in a predictive manner, to compensate for interaction torques—loads arising at one joint that depend on motion about other joints.

Development of an Apparatus for Bilateral Rhythmical Training of Arm Movement Via Linear and Elliptical Trajectories of Various Directions

2014 ◽  
Vol 8 (3) ◽  
Author(s):  
Zlatko Matjačić ◽  
Matjaž Zadravec ◽  
Jakob Oblak
Keyword(s):  
Muscle Activation ◽  
Arm Movement ◽  
Emg Activity ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Arm Cycling ◽  
Arm Reaching ◽  
Direction Of Movement ◽  
Muscle Groups ◽  
Neurologically Intact

Clinical rehabilitation of individuals with various neurological disorders requires a significant number of movement repetitions in order to improve coordination and restoration of appropriate muscle activation patterns. Arm reaching movement is frequently practiced via motorized arm cycling ergometers where the trajectory of movement is circular thus providing means for practicing a single and rather nonfunctional set of muscle activation patterns, which is a significant limitation. We have developed a novel mechanism that in the combination with an existing arm ergometer device enables nine different movement modalities/trajectories ranging from purely circular trajectory to four elliptical and four linear trajectories where the direction of movement may be varied. The main objective of this study was to test a hypothesis stating that different movement modalities facilitate differences in muscle activation patterns as a result of varying shape and direction of movement. Muscle activation patterns in all movement modalities were assessed in a group of neurologically intact individuals in the form of recording the electromyographic (EMG) activity of four selected muscle groups of the shoulder and the elbow. Statistical analysis of the root mean square (RMS) values of resulting EMG signals have shown that muscle activation patterns corresponding to each of the nine movement modalities significantly differ in order to accommodate to variation of the trajectories shape and direction. Further, we assessed muscle activation patterns following the same protocol in a selected clinical case of hemiparesis. These results have shown the ability of the selected case subject to produce different muscle activation patterns as a response to different movement modalities which show some resemblance to those assessed in the group of neurologically intact individuals. The results of the study indicate that the developed device may significantly extend the scope of strength and coordination training in stroke rehabilitation which is in current clinical rehabilitation practice done through arm cycling.

The Role of Robotic Path Assistance and Weight Support in Facilitating 3D Movements in Individuals With Poststroke Hemiparesis

2020 ◽  
Vol 34 (2) ◽  
pp. 134-147
Author(s):  
Preeti Raghavan ◽  
Seda Bilaloglu ◽  
Syed Zain Ali ◽  
Xin Jin ◽  
Viswanath Aluru ◽  
...  
Keyword(s):  
Scale Score ◽  
Motor Impairment ◽  
Movement Control ◽  
Arm Movement ◽  
Random Order ◽  
Healthy Controls ◽  
High Functioning ◽  
Weight Support ◽  
Speed Error ◽  
Low Functioning

Background. High-intensity repetitive training is challenging to provide poststroke. Robotic approaches can facilitate such training by unweighting the limb and/or by improving trajectory control, but the extent to which these types of assistance are necessary is not known. Objective. The purpose of this study was to examine the extent to which robotic path assistance and/or weight support facilitate repetitive 3D movements in high functioning and low functioning subjects with poststroke arm motor impairment relative to healthy controls. Methods. Seven healthy controls and 18 subjects with chronic poststroke right-sided hemiparesis performed 300 repetitions of a 3D circle-drawing task using a 3D Cable-driven Arm Exoskeleton (CAREX) robot. Subjects performed 100 repetitions each with path assistance alone, weight support alone, and path assistance plus weight support in a random order over a single session. Kinematic data from the task were used to compute the normalized error and speed as well as the speed-error relationship. Results. Low functioning stroke subjects (Fugl-Meyer Scale score = 16.6 ± 6.5) showed the lowest error with path assistance plus weight support, whereas high functioning stroke subjects (Fugl-Meyer Scale score = 59.6 ± 6.8) moved faster with path assistance alone. When both speed and error were considered together, low functioning subjects significantly reduced their error and increased their speed but showed no difference across the robotic conditions. Conclusions. Robotic assistance can facilitate repetitive task performance in individuals with severe arm motor impairment, but path assistance provides little advantage over weight support alone. Future studies focusing on antigravity arm movement control are warranted poststroke.

Are Complex Control Signals Required for Human Arm Movement?

1998 ◽  
Vol 79 (3) ◽  
pp. 1409-1424 ◽  
Author(s):  
Paul L. Gribble ◽  
David J. Ostry ◽  
Vittorio Sanguineti ◽  
Rafael Laboissière
Keyword(s):  
Joint Stiffness ◽  
Arm Movement ◽  
Movement Speed ◽  
Muscle Properties ◽  
Complex Control ◽  
Equilibrium Trajectory ◽  
Control Signals ◽  
Human Arm ◽  
Constant Rate ◽  
Arm Motion

Gribble, Paul L., David J. Ostry, Vittorio Sanguineti, and Rafael Laboissière. Are complex control signals required for human arm movement? J. Neurophysiol. 79: 1409–1424, 1998. It has been proposed that the control signals underlying voluntary human arm movement have a “complex” nonmonotonic time-varying form, and a number of empirical findings have been offered in support of this idea. In this paper, we address three such findings using a model of two-joint arm motion based on the λ version of the equilibrium-point hypothesis. The model includes six one- and two-joint muscles, reflexes, modeled control signals, muscle properties, and limb dynamics. First, we address the claim that “complex” equilibrium trajectories are required to account for nonmonotonic joint impedance patterns observed during multijoint movement. Using constant-rate shifts in the neurally specified equilibrium of the limb and constant cocontraction commands, we obtain patterns of predicted joint stiffness during simulated multijoint movements that match the nonmonotonic patterns reported empirically. We then use the algorithm proposed by Gomi and Kawato to compute a hypothetical equilibrium trajectory from simulated stiffness, viscosity, and limb kinematics. Like that reported by Gomi and Kawato, the resulting trajectory was nonmonotonic, first leading then lagging the position of the limb. Second, we address the claim that high levels of stiffness are required to generate rapid single-joint movements when simple equilibrium shifts are used. We compare empirical measurements of stiffness during rapid single-joint movements with the predicted stiffness of movements generated using constant-rate equilibrium shifts and constant cocontraction commands. Single-joint movements are simulated at a number of speeds, and the procedure used by Bennett to estimate stiffness is followed. We show that when the magnitude of the cocontraction command is scaled in proportion to movement speed, simulated joint stiffness varies with movement speed in a manner comparable with that reported by Bennett. Third, we address the related claim that nonmonotonic equilibrium shifts are required to generate rapid single-joint movements. Using constant-rate equilibrium shifts and constant cocontraction commands, rapid single-joint movements are simulated in the presence of external torques. We use the procedure reported by Latash and Gottlieb to compute hypothetical equilibrium trajectories from simulated torque and angle measurements during movement. As in Latash and Gottlieb, a nonmonotonic function is obtained even though the control signals used in the simulations are constant-rate changes in the equilibrium position of the limb. Differences between the “simple” equilibrium trajectory proposed in the present paper and those that are derived from the procedures used by Gomi and Kawato and Latash and Gottlieb arise from their use of simplified models of force generation.

Hip Rotations’ Influence of Electromyographic Activity of Gluteus Medius Muscle During Pelvic-Drop Exercise

2017 ◽  
Vol 26 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Renan Lima Monteiro ◽  
Joana Hoverter Facchini ◽  
Diego Galace de Freitas ◽  
Bianca Callegari ◽  
Sílvia Maria Amado João
Keyword(s):  
Outcome Measures ◽  
Random Order ◽  
Gluteus Medius ◽  
Emg Activity ◽  
Neutral Position ◽  
Electromyographic Activity ◽  
Medial Rotation ◽  
Lateral Rotation ◽  
Tensor Fasciae Latae ◽  
Hip Rotation

Context:Pelvic-drop exercises are often used to strengthen the gluteus medius (GM) muscle with the aim of increasing or prioritizing its recruitment. However, the effect of hip rotation on the performance of the action of the GM is unknown.Objective:To evaluate the effect of hip rotation on the recruitment of the GM, tensor fasciae latae (TFL), and quadratus lumborum (QL).Method:Seventeen healthy subjects performed 2 sets of 4 repetitions of pelvic-drop exercise in random order with pelvic-drop lateral, medial, and neutral rotation of the hip.Main Outcome Measures:The electromyographic (EMG) activity of the GM, TFL, and QL was evaluated using surface electromyography.Results:There were significant increases in the activation of the GM with medial and neutral rotation compared with lateral rotation (P = .03, P = .01, respectively), and there was no difference between medial and neutral rotation (P = 1.00). There was no difference in EMG activity of the TFL and QL in any of the positions. The GM:TFL ratio was the same in all analyzed positions. Regarding the GM:QL ratio, there was a significant increase with medial rotation compared with lateral rotation (P = .02).Conclusions:Pelvic-drop exercises are more efficient for activating the GM when the hip is in medial rotation and neutral position.

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