It's interesting to look at the differences between the way Dexter's doing it and the way we do it. Dexter appears to be lifting his foot straight up off the ground and then falling forward to produce the forward motion.
The way humans walk is exactly the opposite. The toes are at a different angle from the foot (when walking), so that our feet effectively look something like ___/ , with the underscores being the foot and the / being the toes. We then transition from the ___ part of the foot to the / part of the foot and push forward, and land flat footed with the other foot. For whatever speed you are going, there is a proper ratio between landing on the ___ part of the foot and pushing off the / part of the foot, and that's where balance comes from. That is, the faster the acceleration of the fall, the faster you transition from ___ to / .
So in humans, balance comes from the way one step connects to the next step, whereas Dexter appears to be treating each step as a discrete unit, where it has to attain balance at the end of one step before going on to the next step.
If you actually have to balance yourself after each individual step instead of using the next step for balance, the problem seems in some ways to be much harder.
Also, the balance problem is greatly compounded by the small steps Dexter takes. Compare this to doing lunges. When you do a lunge, you basically take a long stride forward and then sink into it, all while keeping your torso perfectly upright. This gives you a much bigger platform for stability. As terrain gets steeper, the way humans walk becomes more like a lunge for this reason.
So my guess is that taking one tiny step and then balancing is the hardest part of this problem, because you have the least tools at your disposal. For example, you can't use the next step to balance you. However, once you can do the last step of the sequence, all the preceding steps working backward from the last one get progressively easier.
I don't know anything about robotics, but as an athlete and sports physiology geek I find the problem interesting.
Another reminder of how incredibly powerful our brains are. Walking and motor skills seem like such basic things because we start mastering them as toddlers. Meanwhile, teams of experts across the world are still trying to figure out how to get a robot to do it. For example, they're talking about finding out the location of where to toe-off based on some instantaneous capture point. None of that ever consciously came to my mind, but these crazy calculations are constantly running in the background.
> It's hard to get precise positioning moving your foot.
How long did you do your experiment? Obviously most of us are not typically used to point and move precisely with our feet. So to be efficient we would need to train for months but that doesn't mean we can't be precise with our feet if we were to dedicate enough time for it.
I once saw a documentary about a german woman who was born without arms. She would do everything with her feet, writing, drawing, smoking a cigarette or mounting a horse and holding the reins with one foot. We are much more adaptive than we think we are but we don't realize it when we have the luxury to not needing it.
Here is not a very good answer to your question, but think about how you know how to walk. It's something that is not entirely conscious. You legs just move between places that you desire to go without any thought to the angle of your knee or tension in your gluts. You feel unbalanced when you center of gravity is too far forward despite having no conscious understanding of where exactly your center of gravity is in the first place.
Spiders likely have a similar feeling but even further refined. They don't know how to build a truss, but they do end up building analogous structures because in their tiny bug brains it just feels right. This is the same way a human knows they are more stable with their legs spread apart and knees slightly bent. Part of that certainly comes from learning but a lot of it is built into our biology too.
Fascinating (if a little hard to stomach) video. This seems to imply that bipedal locomotion is learned, while quadrupeds have the skill hardwired into lower-level structures. (Certainly, having watched my eldest figure it out, it doesn't seem to be an innate ability in humans.)
Speaking of which, any good videos on how we balance ourselves when standing?
And beyond the muscle mechanics, do we understand what the brain is doing? For example, I find it fascinating that I cannot balance myself on one foot if I close my eyes. So obviously we use some visual cues to balance.
From the article it seems the hopping it what makes it tricky. Their model is that the distance to the animal is the same as the distance to where their feet touch the ground. When an animal is in the air the feet appear to touch the ground further away due to perspective.
Granted that their model for upright walking is very basic.
But if their basic premise is sound and valid and taking their claims at face value, it could potentially explain how more complex behaviors like walking may emerge from the simpler examples in their demo.
>the problem seems to be that their muscles cannot support weight or balance.
It does? Newborns can support their own weight when hanging. Most toddlers can support their own weight standing long before they develop the coordination required to walk. Babies lack fine motor control.
Our ancestors, with less complex brains, would have been able to walk shortly after birth, hence the walking reflex.
I suspect the issue is that the complexity of modern human brains delays the formation of the neural circuits required for walking because a whole bunch of complex features are developing at the same time.
> Human feet are a nightmare for bipedal locomotion ...
The ostrich had a quarter of a billion years to master bipedal locomotion. What you get is a foot that an engineer would argue is a much more optimal...
The human door can perform many operations an ostrich foot cannot. There’s a “just so” factor to that of course: ostrich has iterated to optimize for a specific set of operations (mainly linear running as far as I can tell, with turning manifested by the hip). And indeed that would probably be better for humans…if that’s all they wanted to do with their feet.
The just so property is that of course we do those things with our feet because we still can, and in a little while (say a million years or so, maybe half that) we could happily abandon, say, the ability to climb a hanging rope in exchange for less foot pain.
But maybe not? The ability to dance, do ballet, make certain combat maneuvers etc may be desirable and selective pressure may not apply to the foot in the same way it did to the Dino-ostrich.
* by which I mean there’s surely a lot more thought behind this quotation but it was appropriately chosen for a general-audience-article as a gloss on a complex thought
That's exactly right. And the article mentions that was the method (smooth locomotion) that they used in the study, but then the researcher made some kind of crazy claim that it shouldn't matter.
This may also be how it works for humans. The more conscious parts of the brain are involved in coming up with a general "movement plan", while fine-grained re-balancing and re-planning is taken care or subconciously.
The way humans walk is exactly the opposite. The toes are at a different angle from the foot (when walking), so that our feet effectively look something like ___/ , with the underscores being the foot and the / being the toes. We then transition from the ___ part of the foot to the / part of the foot and push forward, and land flat footed with the other foot. For whatever speed you are going, there is a proper ratio between landing on the ___ part of the foot and pushing off the / part of the foot, and that's where balance comes from. That is, the faster the acceleration of the fall, the faster you transition from ___ to / .
So in humans, balance comes from the way one step connects to the next step, whereas Dexter appears to be treating each step as a discrete unit, where it has to attain balance at the end of one step before going on to the next step.
If you actually have to balance yourself after each individual step instead of using the next step for balance, the problem seems in some ways to be much harder.
Also, the balance problem is greatly compounded by the small steps Dexter takes. Compare this to doing lunges. When you do a lunge, you basically take a long stride forward and then sink into it, all while keeping your torso perfectly upright. This gives you a much bigger platform for stability. As terrain gets steeper, the way humans walk becomes more like a lunge for this reason.
So my guess is that taking one tiny step and then balancing is the hardest part of this problem, because you have the least tools at your disposal. For example, you can't use the next step to balance you. However, once you can do the last step of the sequence, all the preceding steps working backward from the last one get progressively easier.
I don't know anything about robotics, but as an athlete and sports physiology geek I find the problem interesting.
reply