12 July 2007


The BBC has an interesting article about getting a robot to walk more like a human. But in at least one respect, they're still doing it the hard way. As Don likes to say, "Most people walk by falling forward and hoping that their other foot will catch them." This is not an efficient way to walk, for several reasons. First, a description from the article: "The robot's momentum causes the robot to rise on its standing leg and a motor moves the swinging leg into position"

Rise on its standing leg. Why? Why rise? For humans, the answer is "so that I don't have to activate and work the quad." In essence, we waste energy that could be used to propel us forward by standing up to avoid using the quads. And this method only works even remotely well on flat terrain. Try it on a rocky slope, and you're just asking for trouble. What's the alternative? Bend the legs! Activate those quads! Sink into the standing leg! This allows you to set the other foot down unweighted. Then if there is a change in terrain, or an obstacle, you can sense it and adjust, and even move the foot again if necessary. It also avoids crashing the weight onto that foot and leg (and knee).

Try walking down a hill sometime with your usual gait. After a while, it starts to hurt. Then try keeping the legs bent and placing the foot unweighted. At first it will slow you down, but it will not jar your leg with every step. This would be a better model for a robot, I think. Leave the bend in the weighted leg the same, move the other leg forward, start placing it on the ground. Sensors in the foot can determine when the unweighted foot has hit the ground, and start to transfer the weight. Sensors can also note any instabilities during the weight shift and adjust as needed (even to picking up the foot again and setting it down in a more stable location).

Because I walk this way out of habit, walking has been helping my knee rather than hurting it. It especially likes going up and down the hills around my dad's house. If I were falling forward onto my front foot, no chance. I'd probably be screaming in pain before I made it one block. Admittedly, it will take time to adjust to walking this way; if nothing else, most people's quadriceps aren't up to it. But the benefits are huge! You're less likely to slip on ice or on gravel; you're less likely to damage your knees; you're less likely to trip over unseen/unnoticed obstacles.

On another note, I read a rather bizarre book some years back. I believe the title was "Everything You Know is Wrong." It posited that humans are the result of cross-breeding apes with aliens, and adopted a lot of the usual creationist canards about why we couldn't have just evolved on this planet without interference. I didn't know much about the "debate" at that point, but one single passage told me that the guy hadn't done much research on walking. He was talking about the preserved primate footprints in volcanic ash (Olduvai? Can't remember now), and how they showed a "bizarre bent-legged gait." Now, if he'd done even a little bit of cross-cultural research, he would have found the taiji walk, the ninja walk, the native-American stalking walk, and probably others that I haven't heard of, which keep the legs bent.


John said...

The 'Inquire Further' hyperlink seems to be broken.

Qalmlea said...

*sighs* It's been working on and off today. I think it's a Blogger issue, since I haven't changed anything. But clicking on the title should take you to the full text.

(If it's still mucked up tomorrow, I'll check the html code)

Qalmlea said...

Yeah, looks like an overall Blogger issue. The expand link at Pooflinger's Anonymous isn't working either.