Industrial robot

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An industrial robot is officially defined by ISO[1] as an automatically controlled, reprogrammable, multipurpose manipulator programmable 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 (a top-level definition relying on the prior definition of robot).

Industrial robots doing vehicle underbody assembly (KUKA).
Industrial robots doing vehicle underbody assembly (KUKA).

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.

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[edit] Industrial robot types, features

The most commonly used robot configurations for industrial automation, include articulated robots (The first and most common) SCARA robots and gantry robots (aka Cartesian Coordinate robots, or x-y-z robots). In the context of general robotics, most types of industrial robots would fall into the category of robot arms (iherent in the use of the word manipulator in the above-mentioned ISO standard).

Industrial robotics exhibit varying degrees of autonomy. Robots are programmed to faithfully carry out 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 on the object itself, which the robot may even need to identify. For example, for more precise guidance, robots often contain machine vision sub-systems acting as their "eyes", linked to powerful computers or controllers. Artificial intelligence, or what passes for it, is becoming an increasingly important factor in the modern industrial robot.

[edit] History of industrial robotics

George Devol received the first patents for robotics in 1954. The first company to produce an industrial robot was Unimation, founded by George Devol and Joseph F. Engelberger in 1956, and was based on Devol's original patents. 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. 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 who refused to abide by international patent laws, so their designs were copied.

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 to more sophisticated applications such as assembly and arc welding. Scheinman then designed a second arm for the MIT AI Lab, called the "MIT arm." Sheinman sold his designs 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 is 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 Stäubli Faverges SCA of France in 1988. Stäubli was still making articulated robots for general industrial and clean room applications as of 2004 and even bought the robotic division of Bosch in late 2004.

Eventually the myopic vision of American industry was superseded by the financial resources and strong domestic market enjoyed by the Japanese manufacturers. Only a few non-Japanese companies managed to survive in this market, including Adept Technology, Stäubli-Unimation, the Swedish-Swiss company ABB (ASEA Brown-Boveri), the Austrian manufacturer igm Robotersysteme AG and the German company KUKA Robotics.

[edit] Technical description

[edit] 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 latter 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).

[edit] Robot programming

Offline programming by ROBCAD
Offline programming by ROBCAD

The setup or programming of motions and sequences for an industrial robot is typically taught by linking the robot controller via communication cable to the Ethernet, FireWire, USB or serial port of a laptop computer. The computer is installed with corresponding interface software. The use of a computer greatly simplifies the programming process. Robots can also be taught via teach pendant, a handheld control and programming unit. Specialized robot software is run either in the robot controller or in the computer or both depending on the system design. 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 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.

[edit] Movement and singularities

Most articulated robots perform by storing a series of positions in memory, and moving to them at various times in their programming. For example, a robot which is moving items from one place to another might have a simple program like this (commonly called a 'pick and place' program):

Define points P1–P5:

  1. Safely above workpiece
  2. 10 cm Above bin A
  3. At position to take part from bin A.
  4. 10 cm Above bin B
  5. At position to take part from bin B.

Define program:

  1. Move to P1
  2. Move to P2
  3. Move to P3
  4. Close gripper
  5. Move to P4
  6. Move to P5
  7. Open gripper
  8. Move to P1 and finish

For a given robot the only parameters necessary to locate the end effector (gripper, welding torch, etc.) of the robot completely are the angles of each of the joints or displacements of the linear axes (or combinations of the two for robot formats such as SCARA). However there are many different ways to define the points. The most common and most convenient way of defining a point is to specify a Cartesian coordinate for it, i.e. the position of the 'end effector' in mm in the X, Y and Z directions. In addition the angles of the end effector in pitch, roll and yaw and the length of the tool must also be specified, depending on the types of joints a particular robot may have. For a jointed arm these coordinates must be converted to joint angles by the robot controller and such conversions are known as Cartesian Transformations which may need to be performed iteratively or recursively for a multiple axis robot. The mathematics of the relationship between joint angles and actual spatial coordinates is called kinematics. Positioning by Cartesian coordinates may be done by entering the coordinates into the system or by using a teach pendant which moves the robot in X-Y-Z directions. It is much easier for a human operator to visualize motions up/down, left right etc. than to move each joint one at a time. When the desired position is reached it is then defined in some way peculiar to the robot software in use, e.g. P1 - P5 above.

[edit] Recent and future developments

As of 2005, the robotic arm business is getting to a mature state, where they can 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. So we have the arm and the eye, but the part that still has poor flexibility is the hand: 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.

Prices of industrial robots will vary with the features, but are usually from 12,000 USD for an entry level model, and as much as 100,000 or more for a heavy-duty, long reach robot.

[edit] Industrial robot manufacturers

[edit] Notes

  1. ^ ISO Standard 8373:1994, Manipulating Industrial Robots – Vocabulary

[edit] See also

Portal:Robotics
 Robotics Portal

[edit] References

  • Nof, Shimon Y. (editor) (1999). Handbook of Industrial Robotics, 2nd ed. John Wiley & Sons. 1378 pp. ISBN 0-471-17783-0.
    A comprehensive reference on the categories and applications of industrial robotics.


[edit] Other External Links

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