Table of Contents

Equilibrium-Point Control

Autors Pohl Steffen & Manglkammer Philipp
Betreuer Marc Jacob
Bearbeitungsdauer ca. 25 Stunden
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Introduction/Motivation

Basic EP-concept (EP = Equilibrium point)

- The EP-Control System states, that a set of two actuators can act like a human muscles Agonist/Antagonist principle.

- The applied force depends on muscle length and stimulation: The longer the artificial muscle, the more effective the stimulation in translated into force

- The system is heading towards a certain joint angle depending on the realation of force and length of both actuators

- Once the angle is reached, the joint stiffness can be modified by equally increasing or decreasing the applied forces in the actuators.

- In our experiment, the used software defines sitffness and angle of the models joints which are automatically are translated in poses. Each of these poses define an Equilibrium Point

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Movement approaches via poses:

- The first set of poses was designed to be as detailed as possible and utilized every possibly relevant angle

- The second set only used simple movement patterns. The more complex movements then resulted from the passive mechanics of the muscle system

Resulting movement:

- the first set of poses result in failure due to loss of balance

- the second set shows a good result even without specific modelling

Summary

At the end, three conclusions were reached:

1. The system is able to head towards a target position without the need for an inverted model

2. Using rough and simple movement patterns looks more natural and is more stable

3. A comparison between both approaches rises the question whether biological movement is also just a product of simple, prototypical poses instead of detailed motions

References

  1. Bayer, A., Schmitt, S., Günther, M., Haeufle, D.F.B. (2017): The influence of biophysical muscle properties on simulating fast human arm movements. Computer Methods in Biomechanics and Biomedical Engineering 20(8), 11-24. https://dx.doi.org/10.1080/10255842.2017.1293663
  2. Christensen, K. B., Günther, M., Schmitt, S., Siebert, T. (2017): Strain in shock-loaded skeletal muscle and the time scale of muscular wobbling mass dynamics. Scientific Reports 7(1), 13266. https://dx.doi.org/10.1038/s41598-017-13630-7