Landing Motion of a Legged Robot with Impact Force Reduction and Joint Torque Minimization

Author(s):  
Xianglong Wan ◽  
Takateru Urakubo ◽  
Yukio Tada
2015 ◽  
Vol 27 (1) ◽  
pp. 32-40 ◽  
Author(s):  
Xianglong Wan ◽  
◽  
Takateru Urakubo ◽  
Yukio Tada

<div class=""abs_img""><img src=""[disp_template_path]/JRM/abst-image/00270001/04.jpg"" width=""300"" />Optimal motion of a legged robot</div> This paper deals with an optimal landing motion of a four-link legged robot that minimizes the impact force at the contact point and the joint torques necessary during the motion. The cost function for optimization is given as the weighted sum of the impact force and the joint torques. The configuration of the robot that is close to a singular configuration is advantageous in minimizing the joint torques for a heavy torso, while the configuration where the leg is bent is advantageous in reducing the impact force. This is shown by numerical optimization results with different weights for the cost function and a theoretical analysis of a simplified model of the robot. </span>


Author(s):  
Ulrich Leuthäusser

In sport climbing, a common method of belaying is to use a static rope brake attached to the belayer’s harness, but the belayer can move freely. This paper investigates the dynamics of a climbing fall with such a belayer. The dynamics are nontrivial because of the belayer’s constraint to be always at or above his initial position. An exact solution for a linear elastic rope is presented. Compared to a fix-point belay, one obtains a considerable force reduction on the belay-chain. However, there is a trade-off of a longer stopping distance of both climber and belayer. In order to calculate the stopping distance, friction between rope and the top carabiner has been taken into account. Closed-form formulas allow for calculating the maximum impact force, as well as the minimum mass of the belayer which is necessary to hold a fall from a certain height.


2018 ◽  
Vol 4 (1) ◽  
pp. e000361 ◽  
Author(s):  
Erin R A Frizzell ◽  
Graham P Arnold ◽  
Weijie Wang ◽  
Rami J Abboud ◽  
Tim S Drew

AimTo compare the available brands of rugby headguards and evaluate their impact attenuation properties at various locations on the cranium, with regard to concussion prevention.MethodsSeven different branded headguards were fitted onto a rigid headform and drop-tested in three different positions. An accelerometer measured the linear acceleration the headform experienced on impact with the ground. Each test involved dropping the headform from a height that generated 103.8 g on average when bare, which is the closest acceleration to the upper limit of the concussion threshold of 100 g. A mean peak acceleration for each drop position was calculated and compared with the bare baseline measurement.ResultsEach headguard demonstrated a significant decrease in the mean peak acceleration from the baseline value (all p≤0.01). Overall the Canterbury Ventilator was the most effective headguard, decreasing the impact force on average by 47%. The least effective was the XBlades Elite headguard, averaging a force reduction of 27%. In five of the seven headguards, the right side of the headwear was the most effective at reducing impact force.ConclusionOverall, the results indicate that it would be beneficial to wear a headguard during rugby in order to reduce the impact forces involved in head collisions. There was also a clear difference in performance between the tested brands, establishing the Canterbury headguard as the most effective. However, only one model of headguard from each brand was tested, so further research evaluating all other models should be considered.


Author(s):  
Juan Calderon ◽  
Gustavo A. Cardona ◽  
Martin Llofriu ◽  
Muhaimen Shamsi ◽  
Fallon Williams ◽  
...  

2012 ◽  
Vol 2012.18 (0) ◽  
pp. 27-28
Author(s):  
Yuuki KIMOTSU ◽  
Junpei HATAYAMA ◽  
Shinnya KOTOSAKA ◽  
Ryuuichi HODOSHIMA

2021 ◽  
Vol 915 ◽  
Author(s):  
Rafsan Rabbi ◽  
Nathan B. Speirs ◽  
Akihito Kiyama ◽  
Jesse Belden ◽  
Tadd T. Truscott

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