scholarly journals Transmission Comparison for Cooperative Robotic Applications

Actuators ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 203
Author(s):  
Mark J. Nandor ◽  
Maryellen Heebner ◽  
Roger Quinn ◽  
Ronald J. Triolo ◽  
Nathaniel S. Makowski
Keyword(s):  
Muscle Activation ◽  
Mechanical Efficiency ◽  
Assistive Devices ◽  
Joint Torque ◽  
Harmonic Drive ◽  
Electromechanical Actuators ◽  
Passive Resistance ◽  
Isometric Torque ◽  
Planetary Transmission ◽  
Robotic Applications

The development of powered assistive devices that integrate exoskeletal motors and muscle activation for gait restoration benefits from actuators with low backdrive torque. Such an approach enables motors to assist as needed while maximizing the joint torque muscles, contributing to movement, and facilitating ballistic motions instead of overcoming passive dynamics. Two electromechanical actuators were developed to determine the effect of two candidate transmission implementations for an exoskeletal joint. To differentiate the transmission effects, the devices utilized the same motor and similar gearing. One actuator included a commercially available harmonic drive transmission while the other incorporated a custom designed two-stage planetary transmission. Passive resistance and mechanical efficiency were determined based on isometric torque and passive resistance. The planetary-based actuator outperformed the harmonic-based actuator in all tests and would be more suitable for hybrid exoskeletons.

THE EFFECT OF LEG PREFERENCE ON MECHANICAL EFFICIENCY DURING SINGLE-LEG EXTENSION EXERCISE

2021 ◽  
Author(s):  
Massimo Venturelli ◽  
Cantor Tarperi ◽  
Chiara Milanese ◽  
Luca Festa ◽  
Luana Toniolo ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Near Infrared ◽  
Isometric Force ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Critical Role ◽  
Inverse Correlation ◽  
Mechanical Efficiency ◽  
Peak Power Output ◽  
Leg Extension

To investigate how leg preference affects net efficiency (ηnet), we examined central and peripheral hemodynamics, muscle fiber type, activation and force of preferred (PL) and non-preferred (NPL) leg. Our hypothesis was that PL greater efficiency could be explained by adaptations and interactions between central, peripheral factors and force. Fifteen young participants performed single-leg extension exercise at absolute (35W) and relative (50%peak power-output (Wpeak)) workloads with PL and NPL. Oxygen uptake, photoplethysmography, Doppler ultrasound, near-infrared-spectroscopy deoxy-hemoglobin [HHb], integrated electromyography (iEMG), maximal isometric force (MVC), rate of force development (RFD50-100) and muscle biopsies of both vastus lateralis, were studied to assess central and peripheral determinants of ηnet. During exercise executed at 35W, ηnet was 17.5±5.1% and 11.9±2.1% (p<0.01) in NP and NPL respectively, while during exercise at the 50% of Wpeak, was in PL = 18.1±5.1% and in NPL = 12.5±1.9 (p<0.01). The only parameter correlated with ηnet was iEMG which showed an inverse correlation for absolute (r=-0.83 and -0.69 for PL and NPL) and relative workloads (r=-0.92 and -0.79 for PL and NPL). MVC and RFD50-100 were higher in PL than in NPL but not correlated to ηnet. This study identified a critical role of leg preference in the efficiency during single-leg extension exercise. The whole spectrum of the central and peripheral, circulatory and muscular determinants of ηnet did not explain the difference between PL and NPL efficiency. Therefore, the lower muscle activation exhibited by the PL is likely the primary determinant of this physiological phenomenon.

Electrically evoked isokinetic plantar flexor torque in males

1987 ◽  
Vol 63 (4) ◽  
pp. 1499-1503 ◽  
Author(s):  
D. O. Thomas ◽  
M. J. White ◽  
G. Sagar ◽  
C. T. Davies
Keyword(s):  
Angular Velocity ◽  
Muscle Activation ◽  
Triceps Surae ◽  
Plantar Flexor ◽  
Velocity Data ◽  
Exponential Equation ◽  
Isometric Torque ◽  
The Mean ◽  
Electrical Stimuli ◽  
Male Subjects

The involuntary angle-specific isokinetic plantar flexor torques of seven male subjects aged 18–21 yr were measured using a Cybex II dynamometer (Lumex) modified by the addition of a strain-gauge load cell to improve the dynamic response of the instrument. Supramaximal electrical stimuli were used to evoke a maximal tetanic response from the triceps surae and ensure constant muscle activation at each angular velocity studied. Angle-specific torques were measured over a range (0.5–5.0 rad/s) of preset velocities, torque decreasing in a nonlinear manner with increasing angular velocity. The torque-velocity data was adequately described by an exponential equation of the form: V = a(e-1/b - e-Po/b) where V = velocity (rad/s), P = torque (N.m), Po = isometric torque (N.m), and a and b are constants. The mean intrasubject coefficient of variation of torque over the range of velocities studies was 7.9 +/- 1.88% (SD).

Experimental knee pain impairs joint torque and rate of force development in isometric and isokinetic muscle activation

2019 ◽  
Vol 119 (9) ◽  
pp. 2065-2073 ◽  
Author(s):  
David A. Rice ◽  
Jamie Mannion ◽  
Gwyn N. Lewis ◽  
Peter J. McNair ◽  
Lana Fort
Keyword(s):  
Knee Pain ◽  
Muscle Activation ◽  
Rate Of Force Development ◽  
Joint Torque ◽  
Force Development

Cycloidal Geartrain In-Use Efficiency Study

2018 ◽  
Author(s):  
Logan C. Farrell ◽  
James Holley ◽  
William Bluethmann ◽  
Marcia K. O’Malley
Keyword(s):  
Space Application ◽  
Harmonic Drive ◽  
Actual Performance ◽  
Speed Reducer ◽  
Efficiency Performance ◽  
Use Efficiency ◽  
High Reduction ◽  
Robotic Applications ◽  
Over Time ◽  
Steady State Performance

Currently, harmonic drives are the primary speed reducer for robotic applications where a high reduction in a small package is required. Cycloidal drives are an alternative option for high reduction, small package, use-cases with the advantage of a higher specific torque and the ability to customize and integrate the drive for the application. These compact style cycloidal drives have been well studied in theory and simulation for their performance, but very little data is available on their actual performance over time. This paper presents experimental data on performance of a cycloidal drive designed for a Lunar or Martian rover application. Burn-in time efficiency curves and torque/speed efficiency profiles are computed after running the drive through 129k output cycles (7.6M input cycles) over the course of 300+ hours of testing. The study finds that substantial burn-in time may be required for steady-state performance, but peak efficiencies of 81% can be achieved. Also, the efficiency is shown to be dependent on the torque through the actuator. This work demonstrates a customized cycloidal drive in a space application that is comparable to a harmonic drive in efficiency performance, with a 2x increase in specific torque, suggesting the application of cycloidal drives could grow tremendously in robotic designs.

scholarly journals Residual force enhancement after lengthening is present during submaximal plantar flexion and dorsiflexion actions in humans

2007 ◽  
Vol 102 (1) ◽  
pp. 18-25 ◽  
Author(s):  
Gavin J. Pinniger ◽  
Andrew G. Cresswell
Keyword(s):  
Plantar Flexion ◽  
Joint Torque ◽  
Voluntary Activation ◽  
Force Enhancement ◽  
Leg Muscles ◽  
Isometric Torque ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
Underlying Mechanisms ◽  
Activation Conditions

Stretch of an activated muscle causes a transient increase in force during the stretch and a sustained, residual force enhancement (RFE) after the stretch. The purpose of this study was to determine whether RFE is present in human muscles under physiologically relevant conditions (i.e., when stretches were applied within the working range of large postural leg muscles and under submaximal voluntary activation). Submaximal voluntary plantar flexion (PFv) and dorsiflexion (DFv) activation was maintained by providing direct visual feedback of the EMG from soleus or tibialis anterior, respectively. RFE was also examined during electrical stimulation of the plantar flexion muscles (PFs). Constant-velocity stretches (15°/s) were applied through a range of motion of 15° using a custom-built ankle torque motor. The muscles remained active throughout the stretch and for at least 10 s after the stretch. In all three activation conditions, the stable joint torque measured 9–10 s after the stretch was greater than the isometric joint torque at the final joint angle. When expressed as a percentage of the isometric torque, RFE values were 7, 13, and 12% for PFv, PFs, DFv, respectively. These findings indicate that RFE is a characteristic of human skeletal muscle and can be observed during submaximal (25%) voluntary activation when stretches are applied on the ascending limb of the force-length curve. Although the underlying mechanisms are unclear, it appears that sarcomere popping and passive force enhancement are insufficient to explain the presence of RFE in these experiments.

Design of Lead Screw Actuators for Wearable Robotic Applications

2005 ◽  
Author(s):  
Kevin W. Hollander ◽  
Thomas G. Sugar
Keyword(s):  
High Weight ◽  
Weight Ratio ◽  
Design Procedure ◽  
Mechanical Efficiency ◽  
Human Muscle ◽  
Wearable Robot ◽  
Screw Design ◽  
Lead Screw ◽  
Standard Lead ◽  
Robotic Applications

A wearable robot is a controlled and actuated device that is in direct contact with its user. As such, the implied requirements of this device are that it must be portable, lightweight and most importantly safe. To achieve these goals an actuator with a good ‘power to weight’ ratio, good mechanical efficiency, good ‘strength to weight’ ratio and that is safe is desired. The design of the standard lead screw does not normally perform well in any of these categories. The typical lead screw has low pitch angles and large radii, thereby yielding low mechanical efficiencies and high weight. However, using the design procedure outlined in this text both efficiency and weight are improved, thus yielding a lead screw system with performances that rival human muscle. The result of an example problem reveals a feasible lead screw design that has a ‘power to weight’ ratio of 277W/kg, approaching that of the DC motor driving it, at 312W/kg, as well as a mechanical efficiency of 0.74, and a maximum ‘strength to weight’ ratio of 11.3kN/kg(1154kgf/kg).

Neuromuscular Adaptation During Skill Acquisition on a Two Degree-of-Freedom Target-Acquisition Task: Isometric Torque Production

2005 ◽  
Vol 94 (5) ◽  
pp. 3046-3057 ◽  
Author(s):  
Jonathan Shemmell ◽  
Matthew Forner ◽  
James R. Tresilian ◽  
Stephan Riek ◽  
Benjamin K. Barry ◽  
...  
Keyword(s):  
Skill Acquisition ◽  
Neural Control ◽  
Muscle Activation ◽  
Joint Torque ◽  
Acquisition Time ◽  
Neutral Position ◽  
Target Acquisition ◽  
Joint Torques ◽  
Flexion Extension ◽  
Torque Development

In this study we attempted to identify the principles that govern the changes in neural control that occur during repeated performance of a multiarticular coordination task. Eight participants produced isometric flexion/extension and pronation/supination torques at the radiohumeral joint, either in isolation (e.g., flexion) or in combination (e.g., flexion–supination), to acquire targets presented by a visual display. A cursor superimposed on the display provided feedback of the applied torques. During pre- and postpractice tests, the participants acquired targets in eight directions located either 3.6 cm (20% maximal voluntary contraction [MVC]) or 7.2 cm (40% MVC) from a neutral cursor position. On each of five consecutive days of practice the participants acquired targets located 5.4 cm (30% MVC) from the neutral position. EMG was recorded from eight muscles contributing to torque production about the radiohumeral joint during the pre- and posttests. Target-acquisition time decreased significantly with practice in most target directions and at both target torque levels. These performance improvements were primarily associated with increases in the peak rate of torque development after practice. At a muscular level, these changes were brought about by increases in the rates of recruitment of all agonist muscles. The spatiotemporal organization of muscle synergies was not significantly altered after practice. The observed adaptations appear to lead to performances that are generalizable to actions that require both greater and smaller joint torques than that practiced, and may be successfully recalled after a substantial period without practice. These results suggest that tasks in which performance is improved by increasing the rate of muscle activation, and thus the rate of joint torque development, may benefit in terms of the extent to which acquired levels of performance are maintained over time.

scholarly journals Do neuromuscular adaptations occur in endurance-trained boys and men?

2010 ◽  
Vol 35 (4) ◽  
pp. 471-479 ◽  
Author(s):  
Rotem Cohen ◽  
Cam Mitchell ◽  
Raffy Dotan ◽  
David Gabriel ◽  
Panagiota Klentrou ◽  
...  
Keyword(s):  
Muscle Strength ◽  
Endurance Training ◽  
Muscle Activation ◽  
Peak Torque ◽  
Metabolic Effects ◽  
Electromechanical Delay ◽  
Time To Peak ◽  
Neuromuscular Adaptations ◽  
Health Related ◽  
Isometric Torque

Most research on the effects of endurance training has focused on endurance training's health-related benefits and metabolic effects in both children and adults. The purpose of this study was to examine the neuromuscular effects of endurance training and to investigate whether they differ in children (9.0–12.9 years) and adults (18.4–35.6 years). Maximal isometric torque, rate of torque development (RTD), rate of muscle activation (Q30), electromechanical delay (EMD), and time to peak torque and peak RTD were determined by isokinetic dynamometry and surface electromyography (EMG) in elbow and knee flexion and extension. The subjects were 12 endurance-trained and 16 untrained boys, and 15 endurance-trained and 20 untrained men. The adults displayed consistently higher peak torque, RTD, and Q30, in both absolute and normalized values, whereas the boys had longer EMD (64.7 ± 17.1 vs. 56.6 ± 15.4 ms) and time to peak RTD (98.5 ± 32.1 vs. 80.4 ± 15.0 ms for boys and men, respectively). Q30, normalized for peak EMG amplitude, was the only observed training effect (1.95 ± 1.16 vs. 1.10 ± 0.67 ms for trained and untrained men, respectively). This effect could not be shown in the boys. The findings show normalized muscle strength and rate of activation to be lower in children compared with adults, regardless of training status. Because the observed higher Q30 values were not matched by corresponding higher performance measures in the trained men, the functional and discriminatory significance of Q30 remains unclear. Endurance training does not appear to affect muscle strength or rate of force development in either men or boys.

Joint Equivalence Design and Analysis of a Tensegrity Joint

2021 ◽  
pp. 1-12
Author(s):  
Bingxing Chen ◽  
Hongzhou Jiang ◽  
Jingxuan Liu ◽  
Shuaibo Lu
Keyword(s):  
Mechanical Efficiency ◽  
Design Criterion ◽  
Elastic Response ◽  
Rotational Degree ◽  
Robotic Arms ◽  
Large Size ◽  
Compliant Joint ◽  
Deviation Degree ◽  
Rigid Joints ◽  
Robotic Applications

Abstract We propose a method to design a tensegrity joint, making its elastic deformation an accurate joint-like motion, such as a rotation around the designed rotational center. The tensegrity joint can be a three rotational degree-of-freedom (DOF) joint through this method. Axis drift is presented as a design criterion to describe the rotational center's deviation degree concerning the compliance center since the rotational center is not fixed to one point for different positions of the tensegrity joint. The axis drift is designed to be in a prescribed range so that the tensegrity joint is approximately equivalent to a rigid joint. In other words, the tensegrity joint's elastic response under external torque and force becomes precise rigid-joint-like kinematics and can replace rigid joints to transfer motion, force, and energy. A large-size tensegrity joint is developed to verify the joint equivalence experimentally. The experimental results show that the tensegrity joint achieved maximum dimensionless axis drift less than 2%, and indicate an excellent joint equivalence. The tensegrity joints' ability to replace rigid joints as modular joints to construct a hyper redundant serial structure is demonstrated using a tensegrity robotic arm. The proposed tensegrity compliant joint has notable benefits of tensegrity structure such as high mechanical efficiency, modularity, and scalability, and can be extended to many robotic applications, such as large-size serial robotic arms and snake-like robots.

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