Robots

Robots

The traditional romantic portrayal of the robot is as an anthropomorphic , autonomous entity that possesses intelligence and walks and talks in a way that mimics human behavior. The truth is not quite so glamorous. Robots are electromechanical machines that rarely resemble the human form. Instead, the overwhelming majority of robots are often anchored to one point and consist of a single flexible arm.

The purpose of robotics technology is essentially to carry out repetitive, physically demanding and potentially dangerous manual activities so that humans are relieved from these tasks. Examples of these chores include working on a factory production line assembly, handling hazardous materials, and dealing with hostile environments like underground mines, underwater construction sites, and explosives plants. Industrial robots can also be scheduled to work twenty-four hours a day to maximize productivity in manufacturing environments—something that human workers have never been able to do.

Conventional robots possess a base which is usually anchored to the floor, but may also be attached to a rail or gantry (platform) that permits sliding movement. An arm called a manipulator, which is flexible and is one of the main features of the robot, is connected to the base. On the tip of the arm is an attachment called the end-effector —this is the mounting point for interchangeable grippers or tools. The arm is moved about by using either hydraulic or pneumatic actuators, or by gears, linkages, and cables driven by electric motors. The motors used are usually of the servo or stepper type. Servo motors rotate at a required speed under command, whereas stepper motors rotate through a given angular displacement (in steps of a certain number of degrees) before stopping. In this way, controlled movement of the arm can be affected within a region known as the workspace or workcell.

Depending on the number of limbs and the type and number of joints that the arm possesses, the robot will be described as having a certain number of degrees of freedom of movement. This indicates the dexterity with which the robot can work using tools and workpieces. A typical robot of moderate complexity will have three degrees of freedom including translational movement and a rotating wrist at the end-effector. The term "payload" is used to refer to the mass that the robot is capable of lifting at the end-effector—a payload of more than 100 kilograms (220.5 pounds) is not uncommon, and loads that would be beyond the capabilities of most human laborers are no trouble for a suitably structured robot. In addition to handling massive payloads, some specialized robots are able to work with a high degree of precision—many guarantee accuracy of placement to within a fraction of a millimeter.

Another type of robot is the mobile robot. These offer features that are uncommon to standard industrial robots used on production lines. Instead, mobile robots often propel themselves on wheels or tracks and carry telemetry equipment like video cameras, microphones, and sensors of other types. The information they collect is then encoded and transmitted to a remote receiving station where human operators interpret the information and guide the mobile robot. Mobile robots are often used to handle dangerous goods like explosives, but perhaps the finest example of this type of robot was the Sojourner rover from the Mars Pathfinder Mission of 1997. This small robot demonstrated that it was possible to guide reliably and accurately a small robotic vehicle over the vast distance between Earth and Mars.

Beyond the source of power that is needed to animate the robot, a computer system of some sort is generally employed to control its actions. This system acts in real-time to both command the robot's movements and to monitor its actions to ensure that it is complying with instructions. Command signals are sent to the motors to initiate a movement, and special sensing devices called transducers are used to measure the amount of actual movement. If the actual movement does not correspond to the requested movement, then the computer system is notified and can make further adjustments. This continual measurement of the robot's activities is called feedback and is of the utmost importance in guaranteeing precise control over its movements. Three-dimensional geometry is the primary mathematical approach that is used to specify the dynamics of robots. Matrix representations of rotational and translational motion are the favored way of programming the required movements of the manipulator and the end-effector.

Frequently, one reasonably small computer is responsible for managing the movements of one robot. However, in large installations that contain many robots, it is also necessary to coordinate their collective operations effectively. This means that other computers need to be used in a supervisory role. The supervisory computer system works at a more abstract level, ensuring that overall production processes can be carried out efficiently. It passes down commands to the individual computers linked to the robots, leaving them to carry out the details of each allotted job. As an example, the supervisory computer might take a computer-aided design (CAD) drawing of a complex assembly and separate out various parts from the drawing, for fabrication by a collection of individual robots. The robots can be retooled for these new tasks and then the supervisory computer can dispatch to their computers coordinates and commands for grasping, moving, cutting, milling or whatever else is required—directly from the CAD drawings.

The future offers a great deal for robotics technology. Established areas of research are slowly making significant strides toward becoming mainstream. Artificial intelligence and robot vision become closer to being standard features each year. It is also proposed that microscopic robots could be developed using the results of advances in nanotechnology , expanding their current role in medical science, where they already assist in performing surgery.

see also Artificial Intelligence; Digital Logic Design; Nanocomputing; Robotics.

Stephen Murray

Bibliography

Malcolm, Douglas R. Jr. Robotics—An Introduction. Belmont, CA: Wadsworth, 1985.

Shahinpoor, Mohsen. A Robot Engineering Textbook. New York: Harper and Row, 1987.

Snyder, Wesley E. Industrial Robots: Computer Interfacing and Control. Englewood Cliffs, NJ: Prentice Hall, 1985.

Internet Resources

Mars Pathfinder. National Aeronautics and Space Administration Jet Propulsion Laboratory. <http://www.jpl.nasa.gov/>