Intro to Industrial Robots
An industrial robot is defined as a programmable, multipurpose manipulator that can rotate or translate in three or more axes. The field of industrial robotics may be more practically defined as the study, design and use of robot systems for manufacturing.
Typical applications of industrial robots include welding, painting, ironing, assembly, pick and place, palletizing, product inspection, and testing, all accomplished with high endurance, speed, and precision.
The most commonly used robot configurations for industrial automation, include articulated robots, SCARA robots, and gantry robots. In the context of general robotics, most types of industrial robots would fall into the category of robot arms.
Industrial robot types and features
- Gantry robots: Used for pick and place work, application of sealant, assembly operations, handling machine tools and arc welding. It's a robot whose arm has three prismatic joints, whose axes are coincident with a Cartesian coordinator.
- Cylindrical robot: Used for assembly operations, handling at machine tools, spot welding, and handling at diecasting machines. It's a robot whose axes form a cylindrical coordinate system.
- Spherical/Polar robot: Used for handling at machine tools, spot welding, diecasting, fettling machines, gas welding and arc welding. It's a robot whose axes form a polar coordinate system.
- SCARA robot: Used for pick and place work, application of sealant, assembly operations and handling machine tools. It's a robot which has two parallel rotary joints to provide compliance in a plane.
- Articulated robot: Used for assembly operations, diecasting, fettling machines, gas welding, arc welding and spray painting. It's a robot whose arm has at least three rotary joints.
- Parallel robot: One use is a mobile platform handling cockpit flight simulators. It's a robot whose arms have concurrent prismatic or rotary joints.
Flexibility of Industrial Robots
Industrial robots exhibit varying degrees of autonomy. Robots are programmed to faithfully do specific actions over and over again without variation and with a high degree of accuracy. These actions are determined by programmed routines that specify the direction, acceleration, velocity, deceleration, and distance of a series of coordinated motions.
Other industrial robots are much more flexible as to the orientation of the object on which they are operating or even the task that has to be performed. The robot may even need to apply sensor readings and logic to determine which task should be performed. For example, robots often contain machine vision subsystems acting as eyes, linked to powerful computers or controllers. For these sophisticated applications, artificial intelligence is becoming an increasingly important factor in the industrial robot design.
Pricing of Industrial Robots
Prices of industrial robots will vary with the features, but are usually about 20,000 USD for an entry level model, and as much as 100,000 or more for a heavy-duty, long range robot. In recent years, declining prices and increasing sophistication have led to robots being considered by smaller companies, as the price/functionality ratios begin to rival those of skilled human workers.
Technical description
Defining parameters
- number of axes: two axes are required to reach any point in a plane; three axes are required to reach any point in space. To fully control the orientation of the end of the arm (i.e. the wrist) three more axes (roll, pitch and yaw) are required. Some designs (e.g. the SCARA robot) trade limitations in motion possibilities for cost, speed, and accuracy.
- kinematics: the actual arrangement of rigid members and joints in the robot, which determines the robot's possible motions. Classes of robot kinematics include articulated, cartesian, parallel and SCARA.
- working envelope: the region of space a robot can reach.
- carrying capacity: how much weight a robot can lift.
- speed: how fast the robot can position the end of its arm.
- accuracy: how closely a robot can reach a commanded position. Accuracy can vary with speed and position within the working envelope. It can be improved by Robot calibration.
- motion control: for some applications, such as simple pick-and-place assembly, the robot need merely return repeatably to a limited number of pre-taught positions. For more sophisticated applications, such as arc welding, motion must be continuously controlled to follow a path in space, with controlled orientation and velocity.
- power source: some robots use electric motors, others use hydraulic actuators. The former are faster, the later are stronger and advantageous in applications such as spray painting, where a spark could set off an explosion.
- drive: some robots connect electric motors to the joints via gears; others connect the motor to the joint directly (direct drive).
Robot programming
The programming of motions and sequences for an industrial robot is done by connecting it to a notebook computer or computer network (using serial, USB, or Ethernet connections). The computer is installed with corresponding interface software. The use of a computer greatly simplifies the programming process.
Robots can also be taught using a teach pendant, a handheld control and programming unit. The teach pendant or PC is usually disconnected after programming and the robot then runs on the program that has been installed in its controller.
In addition, machine operators often use "HMI" human-machine-interface devices, typically touch screen units, which serve as the operator control panel. The operator can switch from program to program, make adjustments within a program and also operate a host of peripheral devices that may be integrated within the same robotic system.
These peripheral devices include robot end effectors which are devices that can grasp an object, usually by vacuum, electromechanical or pneumatic devices. Also emergency stop controls, machine vision systems, safety interlock systems, bar code printers and an almost infinite array of other industrial devices are accessed and controlled via the operator control panel.
History of industrial robotics
The first company to produce an industrial robot was Unimation, founded by Joseph F. Engelberger in 1962, with the basic inventions of George Devol.
Unimation robots were also called programmable transfer machines since their main use at first was to transfer objects from one point to another, less than a dozen feet or so apart. They used hydraulic actuators and were programmed in joint coordinates, i.e. the angles of the various joints were stored during a teaching phase and replayed in operation.
Japanese Industrial Robots
For some time Unimation's only competitor was Cincinnati Milacron Inc. of Ohio. This changed radically in the late 1970s when several big Japanese conglomerates began producing similar industrial robots. Unimation had obtained patents in the United States but not in Japan, so their designs were copied and then improved upon in that country. Manufacturers include:
Further Advances
In 1969, Victor Scheinman at Stanford University invented the Stanford arm: an all-electric, 6-axis articulated robot designed to permit an arm solution. This allowed the robot to accurately follow arbitrary paths in space and widened the potential use of the robot in complex applications such as assembly and arc welding. Sheinman sold his design to Unimation, who further developed it with support from General Motors and later sold it as the Programmable Universal Machine for Assembly (PUMA).
In 1973 KUKA Robotics built its first industrial robot, known as FAMULUS. This was the first articulated industrial robot to have six electromechanically driven axes.
Interest in industrial robotics swelled in the late 1970s and many companies entered the field, including large firms like General Electric, and General Motors (which formed joint venture FANUC Robotics with FANUC LTD of Japan).
US start-ups included Automatix and Adept Technology, Inc. At the height of the robot boom in 1984, Unimation was acquired by Westinghouse Electric Corporation for 107 million US dollars. Westinghouse sold Unimation to St ¤ubli Faverges SCA of France in 1988.
Eventually the deeper long term financial resources and strong domestic market enjoyed by the Japanese companies prevailed, their robots spread all over the globe. Only a few non-Japanese companies managed to survive in this market, including Adept Technology, St ¤ubli-Unimation, the Swedish-Swiss company ABB (ASEA Brown-Boveri), the Austrian manufacturer igm Robotersysteme AG and the German company KUKA Robotics.
Future Development In Industrial Robotics
The robotic arm business now mature, with products that provide enough speed, accuracy and ease of use for most of the applications. Vision guidance (aka machine vision) is bringing a lot of flexibility to robotic cells.
With arm and eye developmen at an advanced state, hand development is still progressing steadily. Currently, the end effector attached to a robot is often a simple pneumatic, 2-position wrench. This doesn't allow the robotic cell to easily handle different parts, in different orientations.
Hand in hand with increasing off-line programmed applications, Robot calibration is becoming more and more important in order to guarantee a good positioning accuracy.
Other developments include downsizing industrial arms for consumer applications and using industrial arms in combination with more intelligent Automated Guided Vehicles (AGVs) to make the automation chain more flexible between pick-up and drop-off.
Industrial robot manufacturers
- ABB
- Adept
- Cloos GmbH
- Comau
- Denso
- Epson Robots
- FANUC Robotics
- igm Robotersysteme
- Intelligent Actuator
- Kawasaki
- KUKA Robotics
- Nachi
- Nidec Sankyo
- OTC
- Reis
- St ¤ubli Robotics
- Yaskawa-Motoman
References
- Nof, Shimon Y. (editor) (1999). Handbook of Industrial Robotics, 2nd ed. John Wiley & Sons. 1378 pp. ISBN 0471177830.
A comprehensive reference on the categories and applications of industrial robotics.
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