Researchers at the University of Arizona's department of electrical and computer engineering have developed a pair of robotic legs that walk with a biomechanically accurate gait. Modeled after human walking mechanisms, the legs and an attached pelvis are part of an effort to create human-like service robots.
The robot's movements emulate the neuromuscular architecture of human walking, which results from interactions among the musculoskeletal system, the nervous system, and the environment. The movements are made possible by emulating those three elements with mechanics, a complex central pattern generator (CPG) that constitutes the neural network, and feedback from sensors.
The researchers, Anthony Lewis and Theresa Klein, say that combining all three elements makes up a complete physical model of the human walking system, making it much more accurate. In an article published in the Journal of Neural Engineering, they claim: "We believe that this is the first robot which fully models walking in a biologically accurate manner." Another walking robot, Boston Dynamics' Petman, has learned how to walk up stairs.
The robot uses artificial leg muscles attached to Kevlar straps that move up and down as actuators, mimicing the natural agonist/antagonist muscle action of human legs. Each muscle consists of a servo motor attached to a bracket. The motor rotates to pull on the strap to mimic muscle contraction. The Golgi tendon organs of human legs are modeled by load sensors in the straps, while load sensors in the feet help a computer adjust the half-size legs' motion according to the surface they are walking on. The CPG is made up of a half-center oscillator plus phase-modulated reflexes that are simulated with a spiking neural network. The robot incorporates "positive force feedback from load sensors as well as other afferent signals to entrain the CPG and drive the step cycle." The robot's neural architecture is enough to produce a propulsive, stabilized walking pattern.
The purposes of this research are both using biology as an inspiration for robotics, and also a method for investigating biological systems. This type of robotics research is sometimes called "soft" robotics. It aims at developing humanoid service robots for use with people such as the elderly, instead of robots that are used in an industrial context. For example, the legs developed by Lewis and Klein are constructed so that they give somewhat when pushed, like organic legs, instead of being rigid and inflexible like an industrial robot.
Although the research is basic and aimed at robotics, it could also be applied to helping people with spinal cord injuries learn to walk again by assisting medical professionals in understanding the biomechanics of how people walk.
What I'm thinking, Ann, is that out in the real world, you would want to avoid the all of the wires connected to this device. I would think wireless connectivity could free up the device for greater flexibility. I know that can be an issue, as with the fire fighting robot on the ship, where you needed the power tether even though the wire could inhibit movement.
I wasn't visualizing the robot walking in the real world just yet, since this is still very much an R&D project. But remote control makes a lot of sense. Most mobile robots are either remote controlled or autonomous, so no wires either way. I was surprised the firefighting ship robot had wires, but maybe that had to do with its size. Maybe the Navy should talk to the Arm or DARPA, which have both solved the wires problem already.
That makes sense, Ann. On the Navy robot, there was a comment about the wire. It had to do with the distance the robot could travel (and the obstacles it would move through) while still receiving power. The person who commented suggested that even with the power cord, the robot would have greater ability to move than with a wireless system.
Rob, the problem I'm having with that explanation is that the Army's BEAR is autonomous and can lift 500 lbs and, I believe, go a lot farther than a shipboard robot. So why can't the Navy's 'bot work by remote control?
Ann, I found the comment about the power cord. It was from GlennA:
Rob Spiegel; I agree that a tether could be a serious restriction. But if the battery pack is only good for 1/2 hour or so, and it only carried 25 to 50 lbs or so of fire extinguisher, it is really worth the cost to develop ? If this robot can drag a fire hose behind it, it should be able to drag a tether also. Someone is doing the cost justification between an autonomous unit vs. a tethered tele-operated unit. And they may decide to build both types for further evaluation, or for different applications. Or they may continue with a tethered unit (as it is now) until the battery pack version is viable.
I guess in a confined space like onboard a ship the tether isn't such a big deal, compared to the BEAR which has to roam all over a messy post-disaster scene. But, as I noted, BEAR can lift and carry 500 lbs without a tether, so it must have some awesome hardware, including batteries.
Yes, it sounds like a much different robot from the Navy firefighter. GlennA has a good point about the Navy robot in that it has to carry a fire hose. As long as it's carrying the fire hose, a power cord is not an additional hindrance.
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