WALKING ROBOTS EXO-SKELETONS TELECHAIRS
WALKING ROBOTS EXO-SKELETONS TELECHAIRS
GO STRAIGHT TO THE WALKING ROBOT DESIGN, AECOMR (a-summer) OR
GO STRAIGHT TO THE WALKING ROBOT DESIGN, AECOMR (a-summer) OR READ FirsT!
I have had had a long-standing interest in robotics and Protosynthetics. My reasons are I wish to construct better man machine environment interfaces. This is with a view to make extreme condition Mecha (exoskeletons) for use in rescue operations in the event of natural or other disasters. Also it is with a view to make artificial parts for people with disabilities, such as limbs etc. However, I am interested in noninvasive techniques, hence the focus on exoskeletons. Consider for a moment that a working exoskeleton, could offer a disabled person mobility as well as functioning as a normal autonomous robot when required. Further It would lend itself to training by a human. Further being able to make the prosthetic completely removable, i.e. no implants etc. is an advantage with respect to contamination of the host. If an implant scenario were to be followed I would rather do it in a biogenetic method, where possible, i.e. construction from with in by nanite, or cellular technologies.
To this end I have completed an honors degree in Mechanical Engineering. As my final project I designed and built a small waking (climbing) robot.
Exoskeletons and Telechairs.
These terms refer to electro/mechanical interfaces that humans use and control. You could say that a car is an exoskeleton or telechair. That is it is an interface for a human being that allows an amplified interaction with the environment. Currently there is still no computer that can drive a car as well as a human, or even remotely close. I believe that we should make robots to be human operated, or at least trained. Like the constructs of Mosher, the Hardiman or Walking Horse. While these have their drawbacks often related to fatigue of the user, the human brain is excellent in accommodating imperfect mechanical systems. Consider how primitive the actual control over a car is, in comparison to the control your own body offers you. After practice you can use a wide variety of cars and still drive it with competence after a very short time, and hold a conversation at the same time. A control systems could be added on as a layer over this. Indeed this is happening now in cars with the advent of air bags, reactive suspension etc.
Walking Robots.The main problems with most designs is that they usually try for a static stability by using an insect or octopod arrangements. There are notable exceptions such as MIT's effort with all types of hoppers and other multi pods which are most impressive.
As far as walking robots or almost any kind of classic animal or humanoid autonomous type robot designs so far, there a two areas that they usually deficient in.
The design the components are almost always ungainly. I'm sure the designers hope that the control system can overcome the inherent back lash, poor tolerances, poor weight to strength ratios and general blocki-ness of the robots, or site cost as the problem, (a very real one). Many bipedal robots simply have a big rectangular block for a torso, and then use and advanced inverted pendulum control system to hopefully compromise. Consider for a moment the complexity of the muscle arrangement and the subtlety of movement you see in the animal world in the torso region. A lower complexity is seen in arthropods, but look at the scale they exist on! The static major body mass assumption carries over into the gait and static / dynamic stability concepts of a robot. To solve this problem, a little, robots should be designed so that components have 'grace' and refinement’ in movement and integration. For example most robot should be hydraulic as this gives a good power to weight ratio. .The channels and or hoses for the fluid could actually be inlayed into the skeleton or exoskeleton of the robot and flow through joint seals. This eliminates much of the imbalance of motor drives etc. Further there should be no central power system, but a series of modular, interchangeable self contained motors, electric, and fuel type through out the robot, almost one per major movement group. This allow the robot or exoskeleton to continue functioning even if it loses limbs, muscle sections or body sections. Further it allows the replacement of parts very quickly. And the over all fluid systems becomes less complex, as their needs to be no major interface manifolds. Even the joint and 'bones/exoskeletons' need to be considered for their elastic and dampening properties. I realize the issue here is again cost. I am talking about possibly a very expensive Robotech design. Although after some consideration, $300000US should be enough to get the mechanics working. It depends largely if you have to design the actuator systems or you can by some of the shelf, However a modular and scalable actuator system may solve this problem
2) The implementation.
Why do so many walking robot designers become fixated on the aspect of ‘walking’ robots, I see that a robot needs to be able to deliver a payload from point A to point B in the quickest possible time while taking up the smallest envelope of space, and consuming small amount of energy. I think that wheels and tracks have a play in all land based locomotion. Consider for a moment the places in a human environment
where wheels may be used, there are enough to make them a viable option. Even
in a non human environment, the forest or bush, a trail bike can almost get any where, places even where animal cannot, they can hop from rock to rock, and almost go up shear walls, given a skilled rider. Wheels should be present in the robot system in some way, as small wheels on the leg tips maybe, as in the case of insect types, only move the limbs when you have to climb! This allows you to redesign the robot leg, rather more simply.
(3) STATIC CENTER OF MASS
I have yet to see a robot philosophy, that divers away (baring MIT, again) from, fixed body movable legs. I.e. the designers will create a body, like an arthropod, and then attach movable legs. The assumption is that insects are statically stable. It seems though as pointed out in Binnards' thesis, that cockroaches are actually dynamically stable at medium to high speed. It may be possible that there is no real distinction between a dynamically stable system and a statically stable system. The time frame only varies. For example even in the most statically stable system, there will be times when the legs that are in the air reduce the static stability even slightly due to the center of mass of the robot no longer being coincident with the desired geometric center for the most stable configuration. In a dynamically stable system it may be argued that in fact it is more statically stable that a statically stable design, as at all points in time the system is moving in such a way that the actual center of mass is very close the desired geometric center of mass. This said the body of the robot should be able to move relative to the legs of the robot.
The results of this although applied some what to an extreme may be seen in the COMR design.
I will hopefully include a short movie of the COMR that I made from technical Lego.
It was able to climb to a height of about 20 cm, which is about 1.5 times its total height. It would be possible to extend this to a factor of 1:5 without significant problems, thus a meter step may be made. To date few robot if any can achieve this ratio of step to body height (note the definition of body height is given as the normal running orientation, it may be argued that this is biased in the COMR's favor), again, MIT has a summer saulting biped and a monopod (I highly recommend you see the clip) that could probably out perform this if they desired. The one draw back with the MIT robots, is, I imagine the tether. It seems, although I am not certain that they require to be tethered, which is not really as bad as it seems in some circumstances.
Sothis said, I present to you, a different way of making a small “walking robot” I would rather call it though an all environmental center of mass robot.
Consider for a moment that it is:scale able, that you can build one car size if you want.
It is cheap to build! The one I made out of Lego, would cost about $500 USD
It can go any where in a human land can bar climbing a tree
It can go fast over flat stretches.
It can go around corners easily
The payload and motors become an asset to the function rather that a problem.
It is always balanced, and could with stand a fair amount of pushing by external forces.
It could run around your house, street, or country!
It does not need a tether, the on board power supply is quite adequate for large radius operation, think of how far a small petrol car can go, or a car!
Well I’ll put more on later please send me any feed back you have to email@example.com