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| Sunday,13 November 2005 |
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Junior Observer |  |
| News Business Features Editorial
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Different types of robots ( Continued from October 30 ) The first obstacle in designing robots is to give the robot a working locomotion system. If the robot will only need to move over smooth ground, wheels or tracks are the best option. Wheels and tracks can also work on rougher ground if they are big enough. But robot designers often look to legs instead, because they are more adaptable. Building legged robots also helps researchers understand natural locomotion - it's a useful exercise in biological research. Typically, hydraulic or pneumatic pistons move robot legs back and forth. The pistons attach to different leg segments just like muscles that attach to different bones. It's a real trick getting all these pistons to work together properly. As a baby, your brain had to figure out exactly the right combination of muscle contractions to walk upright without falling over. Similarly, a robot designer has to figure out the right combination of piston movements involved in walking and program this information into the robot's computer. Many mobile robots have a built-in balance system (a collection of gyroscopes/rotating device used to keep navigation instruments steady), for example that tells the computer when it needs to correct its movements. Bipedal locomotion (walking on two legs) is naturally unstable, which makes it very difficult to implement in robots. To create more stable robot walkers, designers commonly look to the animal world, specifically insects. Six-legged insects have exceptionally good balance, and they adapt well to a wide variety of terrain (land). Some mobile robots are controlled by remote - a human tells them what to do and when to do it. The remote control might communicate with the robot through an attached wire, or using radio or infrared signals. Remote robots, often called puppet robots, are useful for exploring dangerous or inaccessible environments, such as the deep sea or inside a volcano. Some robots are only partially (in part) controlled by remote. For example, the operator might direct the robot to go to a certain spot, but not steer it there - the robot would find its own way. Autonomous robots can act on their own, independent of any controller. The basic idea is to program the robot to respond in a certain way to outside stimuli (something that activates a person or thing). The very simple bump-and-go robot is a good illustration of how this works. This sort of robot has a bumper sensor to detect obstacles (barriers). When you turn the robot on, it moves along in a straight line. When it finally hits an obstacle, the impact pushes in its bumper sensor. The robot's programming tells it to back up, turn to the right and move forward again, in response to every bump. In this way, the robot changes direction any time it encounters an obstacle. Advanced robots use more complex versions of this same idea. Roboticists create new programs and sensor systems to make robots smarter and more understanding. Today, robots can effectively navigate a variety of environments. Simpler mobile robots use infrared or ultrasound sensors to see obstacles. These sensors work the same way as animal echolocation: the robot sends out a sound signal or a beam of infrared light and detects the signal's reflection. The robot locates the distance to obstacles based on how long it takes the signal to bounce back. More advanced robots use stereo vision to see the world around them. Two cameras give these robots an understanding of depth and image-recognition software gives them the ability to locate and classify various objects. Robots might also use microphones and smell sensors to analyse the world around them. Some autonomous robots can only work in a familiar, constrained (restricted) environment. Lawn-mowing robots, for example, depend on buried border markers to define the limits of their yard. An office-cleaning robot might need a map of the building to move from point to point. More advanced robots can analyse and adapt to unfamiliar environments, even to areas with rough terrain. These robots may associate certain terrain patterns with certain actions. A rover robot, for example, might construct a map of the land in front of it based on its visual sensors. If the map shows a very bumpy terrain pattern, the robot knows to travel another way. This sort of system is very useful for robots that explore or operate on other planets. An alternative robot design takes a less structured approach - randomness. When this type of robot gets stuck, it moves its parts every way until something works. Force sensors work very closely with the actuators, instead of the computer directing everything based on a program. This is something like an ant trying to get over an obstacle - it doesn't seem to make a decision when it needs to get over an obstacle, it just keeps trying things until it gets over it. For decades, a small but passionate band of hobbyists (involved in a hobby) has been creating robots in garages and basements all over the world. Homebrew robotics is a rapidly expanding subculture with a sizable Web presence. Amateur roboticists put together their creations using commercial robot kits, mail order components, toys and even old VCRs. Homebrew robots are as varied as professional robots. Some part-time roboticists tinker with elaborate walking machines, some design their own service robots and others create competitive robots. The most familiar competitive robots are remote control fighters like the ones you might see on TV. These machines aren't considered "true robots" because they don't have reprogrammable computer brains. They're basically more powerful remote control cars. |
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