Industrial Robotics
Short Description
introductory report on robotics...
Description
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áp p The word ³robot´ was introduced by the Czech playright Karel ß Capek in his 1920 play Rossum¶sc niversal Robots c The word ³robota´ in Czech means simply ³work.´ In spite of such practical beginnings,science fiction writers and early Hollywood movies have given us a romantic notion of robots. Thus, in the 1960s robots held out great promises for miraculously revolutionizing industry overnight. In fact, many of the more far-fetched expectations from robots have failed to materialize. For instance,in underwater assembly and oil mining, teleoperated robots are very difficult to manipulate and have largely been replaced or augmented by ³smart´ quick-fit couplings that simplify the assembly task. However, through good design practices and painstaking attention to detail, engineers have succeeded in applying robotic systems to a wide variety of industrial and manufacturing situations where the environment is structured or predictable. Today, through developments in computers and artificial intelligence techniques and often motivated by the space program, we are on the verge of another breakthrough in robotics that will afford some levels of autonomy in unstructured environments. c lc cc cc cccc cc reprogrammable, multifunctionalmanipulator designed to move material, parts,tools, or specialized devices through various programmed motions for the performance of a variety of tasks . -Robot Institute of merica, 1979 OR which performs automated physical tasks, either according to direct human supervision, a pre-defined program, or a set of general guidelines using artificial intelligence techniques. - WikiPedia à cc ü cautomatic device c c c c c c c cc ccc c cc c ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c
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V ncient Greek poet Homer described mechanical helpers built by Hephaistos, the Greek god of metalsmiths. V The golems of medieval Jewish legend were robot-like servants made of clay, brought to life by a spoken charm. V In 1495, Leonardo da Vinci drew plans for a mechanical man. V Real robots were only possible in the 1950s and 1960s with the introduction of transistors and integrated circuits V fter the 1950¶s the first commercial robot nicknamed the 'nimateµ, was created. V The first nimate was installed at a General Motors plant to work with heated die-casting machines. Vc ccc c c c cc
GEORGE DEVOL George Devol applied for the first robotics patents in 1954 (granted in 1961). The first company to produce a robot was nimation, founded by Devol and Joseph F. Engelberger in 1956, and was based on Devol's original patents.c Vc c ccc c c c c ccc c c cc!"c#$c Vc %c cc c c c c cc ccc cc c Vc &'c c$(c c c)*+ccc , c -c , c c c c c c , c c c c cc c c c. c c/c!0cc c c c cc c c c c cc c, c c1-c cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c
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play a key role in automation and have helped improve manufacturing and assembly operations around the world. sing , machines and tools can be mounted onto robotic wrists, for example, that perform functions precisely and quickly. offer numerous advantages over manual industrial labor or fixed automation including increased speed and the ability to function in harsh environments. dded flexibility and dexterity offered by help manufacturers get jobs done faster, while cutting costs. In the future, technological advancements are expected to further increase the intelligence of robots that will be able to learn, see and sense things - and complete even more tasks. "
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ISO 8373:1994: ´ manipulating industrial robot is an automatically controlled, reprogrammable, multipurpose manipulator programmable in three or more axes which may be either fixed in place or mobile for use in industrial applications´. à*c general-purpose, programmable machine possessing certain anthropomorphic (human-like) characteristics.
JIR (now J R ) attributes this success to three characteristics of industrial robots: - Industrial robots are programmable automation devices and are, as a consequence, flexible and versatile (unlike special-purpose automated machines). - Industrial robots exceed the physical and mechanical abilities of humans during extended work periods and in uncomfortable or hazardous environments. - Industrial robots perform with high fidelity and accuracy and in compliance with their programmed instructions c cc c
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), c 12c 213c &34 5 4 ( c 555c 6435 c 571c 1 15 c c 4 2c c1 5 15c12c c1c1c 3c There are several definitions used to describe the degrees of freedom (dof) in a robot arm. Defining the dof by the number of joints on the robot arm is incorrect; a seven joint robot arm will hardly have seven dof, only six are available in our definition of six dimensional space. It is also possible to have a robot with six joints and only three degrees of freedom. The number of dof available influences a robots ability to orientate the endeffector in six dimensional space. Most robots are constructed in a fashion to using a single chain of links and joints. These links and joints are described as a series of prismatic and revolute joints, counting from the base out. Each joint, moveable axis, on the arm is considered a degree of freedom. (DOF)± the number of different ways in which a robot arm can move.
Layout of a robotic arm with 7 degree of freedom
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V Prismatic joints (sliding joints) *P: a) Linear joint (L)- sliding movement with the axis of the two links being parallel. b) Orthogonal joint (O)- sliding movement, but the input and output links are perpendicular to each other. V Rotary joints *R:
c) Rotational joint ( R) ± the axis of rotation is perpendicular to both in and output links. d) Twisting joint ( T)- the axis of rotation is parallel to the axes of the two links. e) Revolving joint ( V)- the rotation joint is parallel to the input link and perpendicular to the output link.
These are the following types of robot configurations :jc The robot consists of three orthogonal slides or prismatic joints. the kinematic designation of which is . Extra joints may be required at the wrist. The work volume describes the region within which the robot can position the end-effector. The work volume depends on the robot geometry and the payload capacity. For c cc c
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instance a robot may not be able to support large weights at the extremities of the work volume, and therefore may have two work volume definitions. Movement is obtained by displacing the arm in each axis, x, y and z. Movement in a single axis or a straight line requires displacement in only one axis. circular motion is more difficult to obtain, requiring a complex set of combined motions. . The geometry of the robot requires a large floor area, which is greater than the work volume. Typical applications for this geometry include: j ssembly, using smaller robot types, j Palletising and unloading machine tools, using larger machines, and j Handling, using the gantry configuration.
jc The cylindrical arm has a revolving waist, on which is mounted a pillar from which the arm slides up and down and in and out on prismatic joints. The kinematic designation for this geometry is . s the name of the robot suggests the work envelope is cylindrical in form. Individual axes can obtain rectilinear motion in a vertical or horizontal direction and rotary motion about the base. However a rectilinear motion from left to right would require a complex set of
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motions. Cylindrical robots are very robust and have a good work area to floor area ratio. Typical operations include: j Loading and unloading machine tools j Palletising j Material transfer within a lab situation
jc The polar or spherical configuration of robot was one of the earliest machine configurations, although few are now designed in this manner. The polar robot has a revolute waist and shoulder with an extending arm. The kinematic designation is given as . dditional joints at the machine wrist are required to ensure the correct orientation of the parts. The work envelope is partially spherical in form. The limitations of shoulder rotation and arm reach limit the design from full spherical motion. These robots are robust and the large work volume enables the machine to pick up objects from the floor, however they still require complex control for rectilinear motion. Typical applications for this robot include: j Handling, of heavy loads e.g. casting and forgings, and j Palletising
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jc m This configuration is also known as µrevolute¶, µjointed arm spherical¶ or µanthropomorphic¶. The arm consists of three revolute joints, the waist utilising a vertical rotation the shoulder and elbow using a horizontal rotation. The kinematic designation for this configuration is . For the correct alignment of the endeffector another three revolute joints are required. The work volume is also spherical in nature with a more comprehensive coverage when compared to the polar configuration. The base of the robot occupies little space in comparison to the work volume, however the use of three revolute joints requires complex control for rectilinear motion. nd although the robot arm can reach over and under objects it is not very rigid at full extension. The dexterity of this robot configuration makes it suitable for: j Spot welding, j rc welding, and j Surface coating, including painting and application of adhesive.
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jc The Selective Compliance ssembly Robot rm or SC R is the most common configuration of assembly robot. The arm consists of two horizontal revolute joints at the waist and elbow, and a final prismatic joint. The kinematic designation of the arm is . n additional revolute joint is normally required ensuring the correct alignment of the end-effector. Note that the kinematic designation is identical to the polar configuration yet the work volumes are very different. When describing the robot it is important to provide as much information as possible to avoid confusion over the machines ability. The work volume is cylindrical in nature, however the restrictions on joint rotation produce the work volume .The floor area occupied by the robot base is small in comparison to the work area, however the rectilinear motion requires complex control of the revolute joints. The key point to remember about this robot configuration is compliance. In order to assemble push fit parts, for example, a chip into a holder, some sideways movement (compliance) should be tolerated to allow the part to line up. The SC R does this without introducing any change in orientation of the
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part that would cause a part to jam. Therefore this robot configuration is often used for: j µtable-top¶ assembly tasks, j Inspection and measurement, and j Transfer of components, Forging and castings using larger machines.
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" is the study of the motion (kinematics) of robots. In a kinematic analysis the position, velocity and acceleration of all the links are calculated without considering the forces that cause this motion. The relationship between motion, and the associated forces and torques is studied in robot dynamics. One of the most active areas within robot kinematics is the screw theory. Robot kinematics are mainly of the following two types: c c and c .Forward kinematics is also known as direct kinematics. In forward kinematics, the length of each linkand the angle of each joint is given and we have to calculate the position of any point in the workvolume of the robot. In inverse kinematics, the length of each link and position of the point in workvolume is given and we have to calculate the angle of each joint. Robot kinematics can be divided in serial manipulator kinematics, parallel manipulator kinematics, mobile robot kinematics and humanoid kinematics. Often robot kinematics are described in reference to a simplified kinematic diagram that applies to a large category of physical robots.
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ï # The different types of robot system components :$ % n industrial robot is comprised of a robot manipulator, power supply, and controllers. The robot manipulator can be divided into two sections, each with a different function: rm and Body - The arm and body of a robot are used to move and position parts or tools within a work envelope. They are formed from three joints connected by large links. Wrist - The wrist is used to orient the parts or tools at the work location. It consists of two or three compact joints. The robot manipulator is created from a sequence of link and joint combinations. The links are the rigid members connecting the joints, or axes. The axes are the movable components of the robot that cause relative motion between adjoining links. The mechanical joints used to construct the manipulator consist of five principal types. Two of the joints are linear, in which the relative motion between adjacent links is non-rotational, and three are rotary types, in which the relative motion involves rotation between links. $ n actuator is a mechanism for activating process control equipment by use of pneumatic, hydraulic, or electronic signals. There are several types of actuators in robotic arms. & & & & &
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$ End-effectors are attached to the end of the robot arm and function much like robotic hands. Robotic end effectors perform multiple applications. variety of robotic end effectors exist, each suited for a specific task. Some examples include: grippers, welding guns, vacuum pumps, blowtorches, and drills. End effectors are also known as: jc jc jc jc
Robotic accessories Robotic peripherals Robotic tools End of arm tooling
$ The controller is the processing interface between the robot and its environment. It provides intelligence and feedback to the robot through the compilation of the sensor measurements. It also acts as a storage device, retaining the sensory information and inputted programs. The computation engine is generally able to process many tasks at one time and seamlessly changes calculations to account for sensory information. The controller includes the hardware that interfaces with the outside world. It stores the user interface, which is used to input various commands.
$ Sensors are divided into two main categories: physical and logical. Physical sensors handle the raw processing of data. Logical sensors then extract data for modules to interpret. jc jc
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Physical Sensors Logical Sensors
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Sensor data may be gathered from several sensor devices in parallel and processed in a multitude of ways. complex hierarchy of processing is possible. Varying characteristics of sensors include accuracy and repeatability. Robots utilized sensors in one of three ways: jc jc jc
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Proprioceptive Sensors Exteroceptive Sensors Exproprioceptive Sensors
The earliest industrial robots were simple sequential machines controlled by a combination of servo motors, adjustable mechanical stops, limit switches, and programmable logic controllers. These machines were generally programmed by a record and play-back method with the operator using a teach pendant to move the robot through the desired path. , the first robot programming language, was developed at MIT during the early 1960s. It was an interpreted language which ran on a (& computer. ), developed at Stanford during the early 1970s, was a general-purpose language which ran as an assembler on a DEC PDP-10 minicomputer. MINI, developed at MIT during the mid-1970s, was an expandable language based on . It allowed programming in Cartesian coordinates with independent control of multiple joints. L (Mujtaba, 1982), developed at Stanford, included some programming features of and Pascal. ) and ) (Shimano et al., 1984), developed by nimation, Inc., was an interpreted language designed to support the PM series of industrial robots c ( Manufacturing Language) (Taylor et al., 1982) was a completely new programming language developed by IBM to support the R/S 1 assembly robot. It was a subroutine-oriented, interpreted language which ran on the Series/1 minicomputer. Later versions were compiled to run on IBM-compatible personal computers to support the 7535 series of SC R robots. MCL, developed by McDonnell Douglas, was an extension of the c language ( utomatic Programming of Tools) originally written for numerically controlled machine
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tools. , developed by TOM TIX, Inc., was an extension of Pascal designed to control robot welding and vision systems. Several additional languages (Gruver et al., 1984; Lozano-Perez, 1983) were introduced during the late 1980s to support a wide range of new robot applications which were developed during this period. )*, developed by dept Technologies, Inc., is a representative modern robot programming language. It has several hundred program instructions and reserved keywords. V+ will be used in the following sections to demonstrate important features of robot programming.
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Replacing humans with robots to perform processes has often led to failure. The reason is that the robots are often mechanically capable of the manipulation while being incapable of process planning and control. Thousands of robot installations have failed because replacing the manual method with the automatic method lacked adaptability to process related variation. The human operators had been using their cognitive abilities to do the job. vast majority of successful robot implementations past and present have a very important common aspect: repeated execution of fixed programs with little or no on-line modification of path or position. - %- Many products are packaged in boxes of regular shape and stacked on standard pallets for shipping. Robots are commonly used to palletize and depalletize boxes because they can be programmed to move through the array of box positions layer after layer. lthough palletizing is more common than depalletizing, there is no major functional difference in the manipulation requirements. Transport distances of several feet are common. Stack heights usually do not exceed 5 ft. Payload weight can be in excess of 100 lb. " Packaging is often a combination of palletizing and assembly-type actions. collection of objects which may not be identical are inserted into a box or other container. The robot may also be required to assemble, place dunnage, seal, or c cc c
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mark the package. Insertion may simply require positioning the pack item over the opening of the package and dropping it. Boxes most often are supplied partially assembled, printed, and folded flat. sually human operators or a special machine will open and prepare the box for packing; rarely will the robot be used for this purpose. . Forges, stamping process, some machine tools, and molding machines are now commonly tended by robots. Historically these types of machines have been loaded by human operators. Now these jobs are considered to be too arduous and hazardous. n important benefit of robotic machine loading is improved product quality resulting from consistent machine cycles. Robots eliminate the inconsistencies of humanpaced loading and as a result the cycle can be precisely repeated. % Robotic spot welding is the most pervasive robot application in the automotive industry. Resistance spot welds are formed by tightly clamping steel pieces together with opposing contact electrodes and then passing a large amount of current through the joint, welding the metal while producing a spray of molten sparks along with loud noise. Then the joint is held momentarily until the weld solidifies. Welds are made at discrete positions by moving the robot-mounted gun to pretaught poses. The spot welding process parameters, pressure and temperature, are controlled with the separate gun controller. Weld location and therefore positioning of the gun are critical. % % Paint spraying is a major application in the automotive industry. Painting booths are hazardous because the paint material is often toxic, carcinogenic, and flammable. Human painters often wear required protective clothing and breathing equipment. The paint fan projecting from the arm-mounted spray gun must be manipulated smoothly along paths that are often curved and complex. Many engineering materials are produced and supplied as stacked or rolled flat plates or sheets. Further fabrication can require forming and/or cutting these materials into precise shapes. Robots are frequently used to manipulate a variety of
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cutting tools along paths that are often complex and curved. Many cutting processes are also used to produce fine features such as holes and slots. % Robot inspection involves relative part/sensor manipulation to compare, measure, or detect a physical characteristic of the objective workpiece. Sensors used in robotic inspection include chemical detectors, computer vision systems, infrared detectors, sonar, laser radar, radiation detectors, capacitive proximity sensors, touch probes, X-ray cameras, particle/photon detectors, thread probes, and go-no go gauges. Robot inspection applications cover the range of manipulation from end effector position-and-hold to continues in-contact path motion .
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The term ³workcell´ refers to a grouping of the robot and its peripheral equipment to assemble any of a large variety of products with little or no human intervention, driven by electronicallydesigned data. It is often desirable to group equipment units together into workcells that can, in composite, perform an entire family of related operations on the product. The work-in-progress enters the workcell, c cc c
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remains while several functions are performed, and then leaves the workcell. The individual equipment units that are used in the workcell (for both processing and materials handling) can consist of combinations of manual, semiautomatic, and fully automated equipment . âc % /& 0 1 % 0" 0 % 0"
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