Why isn't passive dynamic walking used more?

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Discussion Overview

The discussion revolves around the topic of passive dynamic walking and its limited application in robotics and exoskeleton design. Participants explore the reasons behind the lack of widespread adoption of passive dynamic models compared to other approaches, particularly in the context of bipedal locomotion and active orthoses.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes a lack of recent literature on passive dynamic walking, questioning if there is a "fatal flaw" that has hindered its use.
  • Another participant counters by highlighting the abundance of search results related to passive dynamic walking designs, suggesting that the absence of a fatal flaw may not be the issue.
  • A different participant raises the question of why there are fewer quasi passive dynamic exoskeletons compared to fully actuated versions, seeking to understand the barriers to passive dynamic design.
  • One contributor suggests that advancements in computational power may have shifted research focus towards active control methods rather than passive dynamics, indicating a blend of both approaches in current research.
  • A participant shares their experience working on a mathematical model for bipedal running, expressing disappointment in the lack of research in biomechanics that integrates physics and mathematical modeling, and referencing historical work in the field.

Areas of Agreement / Disagreement

Participants express differing views on the reasons for the limited use of passive dynamic walking, with some suggesting a lack of flaws in the model itself while others propose that advancements in technology and research focus may be influencing its adoption. The discussion remains unresolved regarding the primary factors affecting the prevalence of passive dynamic designs.

Contextual Notes

Participants mention various models and research efforts, but there is uncertainty regarding the current state of research and the integration of mathematical modeling in biomechanics. The discussion highlights potential limitations in understanding the dynamics of passive walking and its applications.

chi-young
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I was researching movement models for bidpedal locomotion and when I stumbled across this amazing video of passive dynamic walking from 1990. But all the papers now I find are about neural oscillation. I do not find a mention of passive dynamic walking anywhere. Was there some kind of fatal flaw that prevented this model from extensive use?
 
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Do you have access to Google Search? I do. When I used these search terms: “knee design for a bipedal walking robot based on a passive-dynamic walker” about 73,000 results appeared. I did not find any mention of a “fatal flaw” among the designs, but maybe you could.
 
ouch.

Okay. Why are there not more quasi passive dynamic lower extremity active orthosis' or exoskeletons in comparison to fully actuated versions?

What is holding passive dynamic exoskeleton design back?
 
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Perhaps as computational power progressed from the 90's it became able to simulate, in real time, the walking motion through methods of electrical excitation. Do realize that walking is a combination of forced and passive oscillation, so perhaps both are being researched as one towards the same goal.
 
I have been working on a physics based mathematical model of a bipedal runner, not a walker, for several years. It uses two models; a spring mass model first developed by Blickhan in ‘89 and a similar swing leg model. Both models use RK4 algorithms controlled by Newton-Raphson drivers to solve Newton’s and Euler’s equations . I was interested in using the combined model to understand how a runner's specific power expenditure (w/kg) depends on their velocity (speed).

I thought that there would be some research in the biomechanics groups (Biomch-L) in this area, but I have been disappointed. I don't know why this is so, but I think it may be because most biomechanics people are well founded in biology and human physiology, and not math/physics and mathematical modeling

There are a few who work in this area. McGeer's work was produced in 1990. As far as I can tell, it has not been built upon. Regarding PDR you might take a look at the PDR400 on Yourtube.com by Owaki. There are several interesting videos that may be of values.

Please post here if you find anyone who is working on a similar math/physics based approach to understanding the PDR model.
 

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