An Inverted Straight Line Mechanism for Augmenting Joint Range of Motion in a Humanoid Robot

Many robotic joints powered by linear actuators suffer from a loss of torque towards the limits of the range of motion. This paper presents the design of a fully backdriveable, force controllable rotary actuator package employed on the Tactical Hazardous Operations Robot (THOR). The assembly pairs a ball screw-driven linear Series Elastic Actuator (SEA) with a planar straight line mechanism. The mechanism is a novel inversion of a Hoeken’s four-bar linkage, using the ball screw as a linear input to actuate the rotary joint. Link length ratios of the straight line mechanism have been chosen to optimize constant angular velocity, resulting in a nearly constant mechanical advantage and peak torque of 115 [Nm] throughout the 150° range of motion. Robust force control is accomplished through means of a lookup table, which is accurate to within ±0.62% of the nominal torque profile for any load case.

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KNEE ISOKINETIC TORQUE IMBALANCE IN FEMALE FUTSAL PLAYERS

Revista Brasileira de Medicina do Esporte ◽

10.1590/1517-869220172305170768 ◽

2017 ◽

Vol 23 (5) ◽

pp. 352-356

Author(s):

Ana Carolina de Mello Alves Rodrigues ◽

Nathália Arnosti Vieira ◽

Ana Lorena Marche ◽

Juliana Exel Santana ◽

Marco Aurélio Vaz ◽

...

Keyword(s):

Range Of Motion ◽

Repeated Measures ◽

Knee Flexion ◽

Peak Torque ◽

Joint Angles ◽

Muscle Imbalance ◽

Flexion Extension ◽

Isokinetic Torque ◽

Extensor Torque ◽

Joint Range

ABSTRACT Introduction: The specificity of sports training can lead to muscle specialization with a possible change in the natural hamstring/quadriceps torque ratio (HQ ratio), constituting a risk factor for muscle injury at the joint angles in which muscle imbalance may impair dynamic stability. Objective: The aim was to evaluate the torque distribution of the hamstrings and quadriceps and the HQ ratio throughout the range of motion in order to identify possible muscle imbalances at the knee of female futsal athletes. Methods: Nineteen amateur female futsal athletes had their dominant limb HQ ratio evaluated in a series of five maximum repetitions of flexion/extension of the knee at 180°/second in the total joint range of motion (30° to 80°). The peak flexor and extensor torque and the HQ ratio (%) were compared each 5° of knee motion using one-way repeated measures ANOVA and Tukey’s post hoc test (p<0.05) to determine the joint angles that present muscular imbalance. Results: Quadriceps torque was higher than 50° to 60° of knee flexion, while hamstrings torque was higher than 55° to 65°. The HQ ratio presented lower values than 30° to 45° of knee flexion and four athletes presented values lower than 60%, which may represent a risk of injury. However, the HQ ratio calculated by the peak torque showed only one athlete with less than 60%. Conclusion: The HQ ratio analyzed throughout the knee range of motion allowed identifying muscle imbalance at specific joint angles in female futsal players.

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Chronic Stretching During 2 Weeks of Immobilization Decreases Loss of Girth, Peak Torque, and Dorsiflexion Range of Motion

Journal of Sport Rehabilitation ◽

10.1123/jsr.2017-0101 ◽

2019 ◽

Vol 28 (1) ◽

pp. 67-71 ◽

Cited By ~ 1

Author(s):

Samantha J. Wilson ◽

Bryan Christensen ◽

Kara Gange ◽

Christopher Todden ◽

Harlene Hatterman-Valenti ◽

...

Keyword(s):

Range Of Motion ◽

Athletic Training ◽

Peak Torque ◽

Muscle Size ◽

Control Group ◽

Controlled Clinical Trial ◽

Static Stretching ◽

Significant Difference ◽

Familiarization Period ◽

Joint Range

Context: Chronic plantarflexor (PF) stretching during ankle immobilization helps preserve calf girth, plantarflexion peak torque, and ankle dorsiflexion (DF) motion. Immobilization can lead to decreases in muscle peak torque, muscle size, and joint range of motion (ROM). Recurrent static stretching during a period of immobilization may reduce the extent of these losses. Objective: To investigate the effects of chronic static stretching on PF peak torque, calf girth, and DF ROM after 2 weeks of ankle immobilization. Design: Randomized controlled clinical trial. Setting: Athletic training facility. Participants: A total of 36 healthy college-aged (19.81 [2.48]) females. Interventions: Subjects were randomly assigned to one of 3 groups: control group, immobilized group (IM), and immobilized plus stretching (IM+S) group. Each group participated in a familiarization period, a pretest, and, 2 weeks later, a posttest. The IM group and IM+S group wore the Aircast Foam Pneumatic Walker for 2 weeks on the left leg. During this time, the IM+S group participated in a stretching program, which consisted of two 10-minute stretching procedures each day for the 14 days. Main Outcome Measures: One-way analysis of variance was used to determine differences in the change of ankle girth, PF peak torque, and DF ROM between groups with an α level of <.05. Results: A significant difference was noted between groups in girth (F2,31 = 5.64, P = .01), DF ROM (F2,31 = 26.13, P < .001), and PF peak torque (F2,31 = 7.74, P = .002). Post hoc testing also showed a significance difference between change in calf girth of the control group compared with the IM group (P = .01) and a significant difference in change of peak torque in the IM+S group and the IM group (P = .001). Also, a significant difference was shown in DF ROM between the control group and IM+S group (P = .01), the control group and the IM group (P < .001), and the IM+S group and the IM group (P < .001). Conclusion: Chronic static stretching during 2 weeks of immobilization may decrease the loss of calf girth, ankle PF peak torque, and ankle DF ROM.

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Synthesis Theory and Optimum Design of Four-bar Linkage with Given Angle Parameters

Mechanical Sciences ◽

10.5194/ms-10-545-2019 ◽

2019 ◽

Vol 10 (2) ◽

pp. 545-552 ◽

Cited By ~ 1

Author(s):

Lairong Yin ◽

Long Huang ◽

Juan Huang ◽

Peng Xu ◽

Xuejun Peng ◽

...

Keyword(s):

High Efficiency ◽

Synthesis Method ◽

Point Contact ◽

Straight Line ◽

Synthesis Of Mechanisms ◽

Solution Region ◽

Straight Line Mechanism ◽

Four Bar Linkage ◽

The Given ◽

Ball Point

Abstract. In this paper, a synthesis method is proposed for the 5-point-contact four-bar linkage that approximates a straight line with given angle parameters. The given parameters were the angles and the location of the Ball point. Synthesis equations were derived for a general Ball–Burmester point case, the Ball–Burmester point at an inflection pole, and the Ball point that coincided with two Burmester points, resulting in three respective groups of bar linkages. Next, taking Ball–Burmester point as the coupler point, two out of the three bar-linkage combinations were used to generate three four-bar mechanisms that shared the same portion of a rectilinear trajectory. Computation examples were presented, and nine cognate straight-line mechanisms were obtained based on the Roberts-Chebyshev theory. Considering that the given parameters were angles which was arbitrarily chosen, with the other two serving as the horizontal and vertical axes, so the solution region graphs of the solutions for three mechanism configurations were plotted. Based on these graphs, the distribution of the mechanism attributes was obtained with high efficiency. By imposing constraints, the optimum mechanism solution was straightforwardly identified by the designers. For the angular parameters prescribed in this paper, the solutions for three straight-line mechanism configurations were obtained, along with nine cognate straight-line mechanisms that shared the same portion of the rectilinear trajectory. All the fixed pivot installation locations and motion performances differed, thus providing multiple solutions to the trajectory of the synthesis of mechanisms.

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Study on Synthesis of Hinged Four-Bar Linkage Straight-Line Mechanism Using Three Symmetric Points

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.426-427.330 ◽

2010 ◽

Vol 426-427 ◽

pp. 330-333

Author(s):

A.P. Hu ◽

De Jun Kong ◽

W. Zhu

Keyword(s):

Straight Line ◽

Symmetric Points ◽

Straight Line Mechanism ◽

Four Bar Linkage

Based on the fact that symmetric coupler curve can have three different tangent points with given straight-line, the three symmetric points of coupler locus was specified, and they was made into symmetric tangent points to determine the position of instant centre method. The size of the hinged four-bar linkage straight-line mechanism is determined using the position of instant centre method. The results were shown that coupler locus curve is obtained with this approach that is approximated with the intended straight-line precisely, and the basis of this approach is simpler than other analytic approaches.

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