|4573 - How Robots Work||05/06/2005 - 15:09:51|
Of course, we also have some intangible attributes, such as intelligence and morality, but on the sheer physical level, the list above about covers it.
A robot is made up of the very same components. A typical robot has a movable physical structure, a motor of some sort, a sensor system, a power supply and a computer "brain" that controls all of these elements. Essentially, robots are man-made versions of animal life -- they are machines that replicate human and animal behavior.
In this article, we'll explore the basic concept of robotics and find out how robots do what they do.
What is a Robot?
You've probably heard of several of these famous robots:
All of these things are considered robots, at least by some people. The broadest definition around defines a robot as anything that a lot of people recognize as a robot. Most roboticists (people who build robots) use a more precise definition. They specify that robots have a reprogrammable brain (a computer) that moves a body.
By this definition, robots are distinct from other movable machines, such as cars, because of their computer element. Many new cars do have an onboard computer, but it's only there to make small adjustments. You control most elements in the car directly by way of various mechanical devices. Robots are distinct from ordinary computers in their physical nature -- normal computers don't have a physical body attached to them.
In the next section, we'll look at the major elements found in most robots today.
A robot needs a power source to drive these actuators. Most robots either have a battery or they plug into the wall. Hydraulic robots also need a pump to pressurize the hydraulic fluid, and pneumatic robots need an air compressor or compressed air tanks.
The actuators are all wired to an electrical circuit. The circuit powers electrical motors and solenoids directly, and it activates the hydraulic system by manipulating electrical valves. The valves determine the pressurized fluid's path through the machine. To move a hydraulic leg, for example, the robot's controller would open the valve leading from the fluid pump to a piston cylinder attached to that leg. The pressurized fluid would extend the piston, swiveling the leg forward. Typically, in order to move their segments in two directions, robots use pistons that can push both ways.
The robot's computer controls everything attached to the circuit. To move the robot, the computer switches on all the necessary motors and valves. Most robots are reprogrammable -- to change the robot's behavior, you simply write a new program to its computer.
Not all robots have sensory systems, and few have the ability to see, hear, smell or taste. The most common robotic sense is the sense of movement -- the robot's ability to monitor its own motion. A standard design uses slotted wheels attached to the robot's joints. An LED on one side of the wheel shines a beam of light through the slots to a light sensor on the other side of the wheel. When the robot moves a particular joint, the slotted wheel turns. The slots break the light beam as the wheel spins. The light sensor reads the pattern of the flashing light and transmits the data to the computer. The computer can tell exactly how far the joint has swiveled based on this pattern. This is the same basic system used in computer mice.
These are the basic nuts and bolts of robotics. Roboticists can combine these elements in an infinite number of ways to create robots of unlimited complexity. In the next section, we'll look at one of the most popular designs, the robotic arm.
The Robotic Arm
The most common manufacturing robot is the robotic arm. A typical robotic arm is made up of seven metal segments, joined by six joints. The computer controls the robot by rotating individual step motors connected to each joint (some larger arms use hydraulics or pneumatics). Unlike ordinary motors, step motors move in exact increments (check out Anaheim Automation to find out how). This allows the computer to move the arm very precisely, repeating exactly the same movement over and over again. The robot uses motion sensors to make sure it moves just the right amount.
An industrial robot with six joints closely resembles a human arm -- it has the equivalent of a shoulder, an elbow and a wrist. Typically, the shoulder is mounted to a stationary base structure rather than to a movable body. This type of robot has six degrees of freedom, meaning it can pivot in six different ways. A human arm, by comparison, has seven degrees of freedom.
The first obstacle 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 terrain 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 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, for example) that tells the computer when it needs to correct its movements.
Bipedal locomotion (walking on two legs) is inherently 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.
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 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.
This sort of robot has a bumper sensor to detect obstacles. When you turn the robot on, it zips 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 elaborate versions of this same idea. Roboticists create new programs and sensor systems to make robots smarter and more perceptive. 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.
Some autonomous robots can only work in a familiar, constrained 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 in order to maneuver from point to point.
More advanced robots can analyze 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 exploratory robots that operate on other planets (check out JPL Robotics to learn more).
An alternative robot design takes a less structured approach -- randomness. When this type of robot gets stuck, it moves its appendages every which 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.
Homebrew robotics is a rapidly expanding subculture with a sizable Web presence. Amateur roboticists cobble together their creations using commercial robot kits, mail order components, toys and even old VCRs.
Homebrew robots are as varied as professional robots. Some weekend roboticists tinker with elaborate walking machines, some design their own service bots and others create competitive robots. The most familiar competitive robots are remote control fighters like you might see on "BattleBots." These machines aren't considered "true robots" because they don't have reprogrammable computer brains. They're basically souped-up remote control cars.
More advanced competitive robots are controlled by computer. Soccer robots, for example, play miniaturized soccer with no human input at all. A standard soccer bot team includes several individual robots that communicate with a central computer. The computer "sees" the entire soccer field with a video camera and picks out its own team members, the opponent's members, the ball and the goal based on their color. The computer processes this information at every second and decides how to direct its own team.
Check out the official RoboCup Web site for more information on Soccer robots, and Google > Computers > Robotics > Competitions for information on other robot competitions. Google > Computers > Robotics > Building will give you more information on building your own robots.
Adaptable and Universal
Most robots to date have been more like kitchen appliances. Roboticists build them from the ground up for a fairly specific purpose. They don't adapt well to radically new applications.
This situation may be changing. A company called Evolution Robotics is pioneering the world of adaptable robotics hardware and software. The company hopes to carve out a niche for itself with easy-to-use "robot developer kits."
The kits come with an open software platform tailored to a range of common robotic functions. For example, roboticists can easily give their creations the ability to follow a target, listen to voice commands and maneuver around obstacles. None of these capabilities are revolutionary from a technology standpoint, but it's unusual that you would find them in one simple package.
The kits also come with common robotics hardware that connects easily with the software. The standard kit comes with infrared sensors, motors, a microphone and a video camera. Roboticists put all these pieces together with a souped-up erector set -- a collection of aluminum body pieces and sturdy wheels.
These kits aren't your run-of-the-mill construction sets, of course. At upwards of $700, they're not cheap toys. But they are a big step toward a new sort of robotics. In the near future, creating a new robot to clean your house or take care of your pets while you're away might be as simple as writing a BASIC program to balance your checkbook.
The Future: AI
Computers can already solve problems in limited realms. The basic idea of AI problem-solving is very simple, though its execution is complicated. First, the AI robot or computer gathers facts about a situation through sensors or human input. The computer compares this information to stored data and decides what the information signifies. The computer runs through various possible actions and predicts which action will be most successful based on the collected information. Of course, the computer can only solve problems it's programmed to solve -- it doesn't have any generalized analytical ability. Chess computers are one example of this sort of machine.
Some modern robots also have the ability to learn in a limited capacity. Learning robots recognize if a certain action (moving its legs in a certain way, for instance) achieved a desired result (navigating an obstacle). The robot stores this information and attempts the successful action the next time it encounters the same situation. Again, modern computers can only do this in very limited situations. They can't absorb any sort of information like a human can. Some robots can learn by mimicking human actions. In Japan, roboticists have taught a robot to dance by demonstrating the moves themselves.
Some robots can interact socially. Kismet, a robot at M.I.T's Artificial Intelligence Lab, recognizes human body language and voice inflection and responds appropriately. Kismet's creators are interested in how humans and babies interact, based only on tone of speech and visual cue. This low-level interaction could be the foundation of a human-like learning system.
Kismet and other humanoid robots at the M.I.T. AI Lab operate using an unconventional control structure. Instead of directing every action using a central computer, the robots control lower-level actions with lower-level computers. The program's director, Rodney Brooks, believes this is a more accurate model of human intelligence. We do most things automatically; we don't decide to do them at the highest level of consciousness.
Because of this, AI research is largely theoretical. Scientists hypothesize on how and why we learn and think, and they experiment with their ideas using robots. Brooks and his team focus on humanoid robots because they feel that being able to experience the world like a human is essential to developing human-like intelligence. It also makes it easier for people to interact with the robots, which potentially makes it easier for the robot to learn.
Just as physical robotic design is a handy tool for understanding animal and human anatomy, AI research is useful for understanding how natural intelligence works. For some roboticists, this insight is the ultimate goal of designing robots. Others envision a world where we live side by side with intelligent machines and use a variety of lesser robots for manual labor, health care and communication. A number of robotics experts predict that robotic evolution will ultimately turn us into cyborgs -- humans integrated with machines. Conceivably, people in the future could load their minds into a sturdy robot and live for thousands of years!
In any case, robots will certainly play a larger role in our daily lives in the future. In the coming decades, robots will gradually move out of the industrial and scientific worlds and into daily life, in the same way that computers spread to the home in the 1980s.
The best way to understand robots is to look at specific designs. The links on the next page will show you a variety of robot projects around the world.
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