Introduction The field of robotics has its origins in science fiction. The term ‘robot’ was derived from the English translation of a fantasy play written in Czechoslovakia around 1920. It took another 40 years before the modern technology of industrial robotics began. Early robots were confined to industrial applications, doing repetitive tasks like loading-unloading machines, welding, spray painting, etc. In the last two decades, robots have stepped out of industrial applications and ventured right into our homes as pets, service robots, helpers, rehabilitation devises, etc. Today, we have both hard (physical) robots like manipulator arms, mobile robots, etc., and also soft (simulated) robots like virtual characters, virtual reality, etc., sometimes simply called ‘bots’. In this chapter, we will survey some of the science fiction stories about robots and trace the historical development of robotics technology. Let us begin our chapter by defining the term robotics and establishing its place in relation to other types of industrial automation. 1.1 AUTOMATION AND ROBOTICS Automation and robotics are two closely related technologies. In an industrial context, we can define automation as a technology that is concerned with the use of mechanical, electronic and computer-based systems in the operation and control of production. Examples of this technology include transfer lines, mechanized assembly machines, feedback control systems (applied to industrial processes), numerically controlled machine tools and robots. Accordingly, robotics is a form of industrial automation. There are three broad classes of industrial automation: fixed automation, programmable automation and flexible automation. Fixed automation is used when the volume of production is very high and it is, therefore, appropriate to design specialized equipment to process the product (or a component of a product) very efficiently and at high production rates. A good example of fixed automation can be found in the automobile industry, where highly integrated transfer lines consistingeave Rbtes ess are edt perform machining operations on engin of see daze wits mis of fixed automation are such that he rans componsTs ye dvidd over a large number of units and te oa ee lo new aemaive methods of ption, Te esting wt ots a ation ita since te inital investment cost is high, eae il ttn plover ticipate, ten the unit ese 2 a a cipated Another problem with fixed automation is thatthe Secu aent eeed to roduce the one product and after that produc’ oe esate equipment is likely to become obsolete, For products with ae a af ued suomaton represents big gamble or Tu the wea vane f products fo be made, In this ease, the production ks eurmets dened o be adepable to variations in product configuration. This ‘capabiy feat is accomplished by operating the equipment under the control of = yrogran” of mstuctns which as been prepared especially forthe given produc. The pe ams ead ino the production equipment, and the equipment performs the lar quence of processing” (or assembly) operations to make that product, ltems of economics the cst ofthe programmable equipment can be spread over « age number of products eventhough the produets are different. Because of the ‘Programming feature andthe resuing adaptability ofthe equipment, many different ungue products canbe made economically in small batches. ‘Ts slatonship ofthe fst two types of automation, as @ function of product SRS sé oducton volume i iusoated in Fig. 1.1. There is a third category ‘crsec fed auomion an programmable automation, which is ealled “feb Programmable pan 1 Tr ibe ot : roc site PEL Relation fed ay ial pa acon fpr Petrone Pe pnten an enna alomation and fie automaton Obert sorts sane om ed forte “ YS" (or FMS) an ibe Of flexible ma 2d pete itlude “exible manufacturne vp tel ig aman TNE Wah tis type gfe hice within the past 15 of 20 on suggests that it is most CE ! 3 (0) of Fig. 2.1. 1 uses a telese nal pivot. The pivot is mous Be Fundamentals of Robot Technology, Programming, and Applications 24 © @ Fig. 24 The four basic robot anatomies: (a) Polar, (b) Cylindrical. (c) Cartesian, (d) Joined arm. (Reprinted from Reference (7) These various joints provide the robot with the capability to move its arm within ' spherical space, and hence the name “spherical coordinate” robot is sometimes applied to this type. ‘The cylindrical configuration as shown in Fig. 2.1(6), uses a vertical column and 4 slide that can be moved up or down along the column. The robot arm is attached to the slide so that it can be moved radially with respect wo the column. By rotating the Column, the robot is capable of achieving a work space that approximates a cylinder [The cartesian coordinate robot illustrated in Fig. 2.1(c), uses three perpendicular slides to construct the x, y, and = axes. Other names are sometimes applied to this ‘configuration, including xyz robot and rectilinear robot. By moving the three slides relative to one another, the robot is capable of operating within a rectangular work envelope. The jointed-arm robot as shown in Fi robot configuration is also sometimes similar to the human-arm, ‘There are relative advantages and disadvantages to the four basic robot anatomies {imply because of thet geometries. In terms of repeatability of motion the capability to move to a taught point in space with minimum error), the box-trame eurecien robot probably possesses the advantage because of its inherently rigid structure Ie {erms of reach (the ability of the robot to extend its arm significantly berend its base), the polar and jointed ann configurations have the advantage The WA capacity of the robot is important in many applicstione. The eylindricel '8.2.1(d) is made up of rotating joints. This called anthropomorphic as its anatomy’ is——___ i canbe designed for high rigidity and log, Fundamentals of Robt Technology. Programming andAgplcatons 23 she gat 2 ations, the ability OF the FOOL to rege == mt Techntegy Programming. and Apptcetons 23 ) wie e ion possess @ natural opening wiht lina configuration posses 8 natal Beomeyi is capability soon a toto a small ‘Te pla oa ions: ae <1 perf productive work such as pick and place, ir och isk by the robot to perform a specific work task pees arco with the performance of a task are referred | oe assembly te Th vreodom (DOF), and atypical industrial robot is equipped «of dom The opening and closing of a gripper is not dom, : “ss wth th aston ofthe arm and body, and two oF tree joins «Connecting the various manipulator joins tht a calle inks, The links can be connected to forma “rs sts oe pari’ chin. Major f industrial manipulator are serial chains * jot se! the design of industrial robots typically involve a relative ng lnks that is ether linear of rotational. Linear joints ‘oven of the connecting links. This motion 2) (eg. by a piston eylinder mechanism, ‘elau've motion along a rack and pinion). Our arial details ofthe joint, but rather with the Supe Pan fast tks, We shall eer to he linea joint or prismati¢ blo * * Prismatic). A prismatic joint is shown in (@) Linear rota () Rovational Lune oF Fevolute joints that can be distin {it types ae illustrated in Fig. 2.2(b.c4) Revolving v J etaon takes place about an axis per a “00 tanta ga DeWEED the two adjacent links The tesoute jag 4 8 pure rotational (R), Twisting ins Mostly referred to as a type R joi the pris Joe ee ea he eve te va te bot tt 4 rot Joe ee he tal cal SY in 1 shown in Fig. 2-2(e), note! "508 oft ate Us Mt very common in biological tWwee bop" FB. 22(/), This joint has he[Twisting T Fea yy th 22 deg Pee rng Wed in robo, Fundamentals of Robo! Technology, Programming, and Applications 25 ‘The arm and body joints are designed to enable the robot to move its end effector to a desired position within the limits of the robot’s size and joint movements. For robots of polar, cylindrical, or jointed-arm configuration, the three degrees of freedom associated with the arm and body motions are: 1. Vertical traverse: This is the capability to move the wrist up or down to provide the desired vertical attitude. 2. Radial traverse: This involves the extension or retraction (in or out movement) of the arm from the vertical center of the robot. 43. Rotational traverse: This is the rotation of the arm about the vertical axis. ‘The degrees of freedom associated withthe arm and body of the robot are shown in Fig. 2.3 fora polar configuration robot. Similar degrees of freedom are associated with the cylindrical configuration and jointed-arm robot. For a cartesian coordinate robot, the three degrees of freedom are vertical movement (z-axis motion), in-and-out movement (-axts motion), and rightof-left movement (x-axis motion), These are achieved by corresponding movements ofthe three orthogonal slides of the robot arm. Rotational traverse Radial | Vertical Fig.2.3. Three degrees of freedom associated with arm and body of apolar coordinate robot. ‘The wrist movement is designed to enable the robot to orient the end effector properly with respect to the task being performed. For example, the hand must be properly oriented to the work being performed such as welding, grasping, etc. To solve this orientation problem, the wrist is normally provided with up to three degrees of freedom (the following is a typical configuration): 1. Wrist roll: Also called wrist swivel, this involves rotation of the wrist mech- anism about the arm axis. 2, Wrist piteh: Given that the wrist roll is in its center position, the pitch would involve the up or down rotation of the wrist. Wrist pitch is also sometimes called vwrist bend. 3. Wrist yaw: Again, given that the wrist swivel is in the center position of its range, wrist yaw would involve the right or left rotation of the wristsates & stare illustrated in Fig. 2.4. The hee degrees of feed” a ‘center postion in the definition for specifying that the on athe wrist about the arm axis Will alter 4 pecause rot inch and yaw 1S ,w movements. renin ofthe pie nd 9 Robot ra Faceplate + a“ oath | code Ns vst pitch AN (bend) Joe want CL ved Waa Fie 24 Toe dares of fed associated wih the robot wrist. «few rbotsthat are commonly used in industry are the PUMA (Programmable Umena! Machne for Assembly, or Programmable Universal Manipulaicn ‘mm developed by Unimation as shown in Fig. 2.5. Although this robot wis eveloped for assembly its structure consists of six revolute joints and can te Used ase general purpose robot. The acronym SCARA stands for Select Compl: at Assembly Robot Arm or Selective Compliant Articulated Robot Am tha: as develope in 198) mainly for assembly operation jointly by Sank Seki, Pentel and NEC in Japan as shown in Fig, 2.6. An articulated robots = which uses rotary joints to access its work space and usually the joints at janged ip ¢ “cha so that one joint supports another further in the chit ‘vet toot are smi wo the human hand and can be used to perform a vate? va caren ana ver toe on ) : J oa \ aia ‘ene shown) Fens ng ‘Keres of freedom, Fundamentals of Robot Technology. Programming, and Applcatons 27 Fig. 2.6 4 SCARA Robot designed for assembly Fig. 2.7. Articulated robots used in machining. spray painting. welding ee 2.1.3. Joint Notation Scheme ‘The physical configuration of the robot manipulator can be described by means ‘of a joint notation scheme, using the joint types defined earlier in this section (LR, T, and ¥), Considering the arm and body joints frst, the letters can be used to ‘designate the particular robot configuration starting with the joint closest the base and proceeding to the joint that connects to the wrist. Accordingly, a jointed-arm. robot (excluding the wrist assembly) would have three rotational joints and would bea yotcs 5 28s pa oats or the Four asi conga, ie less than the tthe designation of more ot the rman ene reine ite ble Tan a be asic types, sp if i cniguring 00s beVONG I=L explore other pass : amie21_ouion scheme fr desea rohorcongwravions “The notation stem can be expanded to include wrist motions by designating woo thre or more yes of wrist joint. The notation starts withthe joint closesin ‘he arm terface. and proceeds tothe mounting plate forthe end effector. Wrist joins are predominant rating joints of type Rand T: Hence, a typical wrist mechanisn with tree roatonl joins would be indicated by TRR (Fig, 2). This notation s simply ade te the notation forthe arm and body configuration, For example? pols coordinate oh with tree-axis wrist might be designated as TRL: TRT. nee oe ae for the possibility of robots that move on 2 — wor or along ao overhead rl system inthe factory. As an illustration, a ‘TRT robot fastened oa platform on wheels that can revel along a track betwee? aa ae a took would be designated by the following notation: L- TRL: TR ae ‘es hough he wheels of the platform rotate, the motion of the 2.2 WORK VOLUME Work solu isthe ‘manipulate ts wrist eat tise refers to the space within which the robot Tork solume is adoped o avon ef Using the wrist end to define the rb robo COMPlcation of different sizes of end eff fe end effectors an addition tothe tari the tobot's working space. Also he lane becaune of gPeble of reaching certain points Wi" ‘of the particular ‘combination of joint i aes robot etemined by te fay, oft * Te hath lowing physical characterises 5 Toba ial cong 1 eA of e HF ofjoins, structure of inks) tte omnes ‘ot mn ; mens Fundamentals of Rabt Technology. Programming, and Applications 29) ‘The influence of the physical configuration on the shape of the work volume is iusra in Fg 28 plot hs work hme tats pal cylindrical robot has a cylindrical work volume. A Cartesian robot has a work volume that is made of a rectangular shaped space. An anthropomorphic robot has « work volume made up oftwo or more spheres on the inside and one sphere onthe outeide Fig.2.8 Work volumes for differen types of robots: (a) Polar 78) Cylindrical, e) Cartesian. (Reprinted from Reference [7]) 2.3 ROBOT DRIVE SYSTEMS ‘The robots capacity to move its body, arm, and wrist is provided by the drive system used to power the robot. The drive system determines its speed of operation, load carrying capacity, and its dynamic performance. To some extent, the drive system determines the kinds of applications thatthe robot can accomplish. In this and the following sections, we will discuss some of these technical features. 2.3.1 Types of Drive Systems Commercially available industrial robots are powered by one of three rypes of rive systems. These three systems are 1. Hydraulic drive 2. Blectrie drive 3. Pneumatic drive 4. Advanced actuators Hydraulic drive and electric drive are the to main types of drives used on more sophisticated robots, while pneumatic drive is used for low load carrying capacity robots and in cases where cil and electricity cannot be used (fire hazard) Hydraulic drive is generally associated with larger robots. The usual advantages ‘of the hydraulic drive system are that it provides the robot with greater speed and strength, The disadvantages of the hydraulic drive system are that it repically adds to the floor space required by the robot, aad that a hydraulic system is inclined to teak oil which is « nuisance, Hydraulic drive systems can be designed t9 actuate ether rotational joints ot linear joints. Rolary vane actuators can be utilized to provide rotary motion, and hydraulic pistons can be used to accomplish linear motion,(30 Industrial Robotics Electric drive systems do not generally provide as much speed or power a hydraulic systems. However, the accuracy and repeatability of electric drive robot; are usually better. Consequently, electric robots tend to be smaller, requiring less floor space, and their applications tend toward more precise work such as assembly. Electric drive robots are actuated by de stepping motors or de servomotors. These motors are ideally suited to the actuation of rotational joints through appropriate drive train and gear systems. Electric motors can also be used to actuate linear joints (e.g., telescoping arms) by means of pulley systems or other translational mechanisms. The economics of the two types of drive systems are also a factor in the decision to utilize hydraulic drive on large robots and electric drive on smaller robots. It tums out that the cost of an electric motor is much more proportional to its size, whereas the cost of a hydraulic drive system is somewhat less dependent on its size. It should be noted that there is a trend in the design of industrial robots toward all electric drives, and away from hydraulic robots because of the disadvantages discussed above. Pneumatic drive is generally reserved for smaller robots that possess fewer degrees of freedom (two- to four-joint motions). These robots are often limited to simple pick-and-place operations with fast cycles. These drives have the added advantage of having compliance or ability to absorb some shock during contact with the environment. Pneumatic power can be readily adapted to the actuation of piston devices to provide translational movement of sliding joints. It can also be used to operate rotary actuators for rotational joints.2.6 END EFFECTORS For industrial applications, the capabilities of the basic robot must be augmented by means of additional devices. We might refer to these devices as the robot’s peripherals. They include the tooling which attaches to the robot’s wrist and the sensor systems which allow the robot to interact with its environment. We provide a more comprehensive treatment of these robot technology areas in Chaps. 5, 6, and 7. In robotics, the term ‘end effector’ is used to describe the hand or tool that is attached to the wrist. The end effector represents the special tooling that permits the general-purpose robot to perform a particular application. This special tooling must usually be designed specifically for the application. End effectors can be divided into two categories: grippers and tools. Grippers would be utilized to grasp an object, usually the workpart, and hold it during the robot work cycle. There are a variety of holding methods that can be used in addition to the obvious mechanical means of grasping the part between two or more additional methods include the use of suction cups, magnets, hooks, and scoo} P tool would be used as an end effector in applications where the robot is required(38 inaustrial Robotics perform some operation on the workpart. These applications include spot welding, are welding. spray painting, and drilling. In each case, the particular tool is attached to the robot's wrist to accomplish the application. With the recent need for holding micro and nano size parts for assembly, several new devices have been developed using smart actuators. PZT and ionic polymers, etc.2.9 ROBOT APPLICATIONS Robots are employed in a wide assortment of, applications in industry. Today, most of the applications are in manufacturing to move materials, parts, and tools of various types. Nonmanufacturing tasks include exploration of space, defense, and medical care. At some time in the near future, a household robot may become a mass produced item, perhaps as commonplace as the automobile is today. Simple toy robot that can perform simple reprogrammable functions are already commonplace. For the present, most industrial applications of robots can be divided into the following categories: 1. Material-handling and machine-loading and -unloading applications In these applications, the robot's function is to move materials or parts from one location in the work cell to some other location. 2. Processing applications This category includes spot welding, arc welding, spray painting, and other operations in which the function of the robot is to manipulate a tool to accomplish some manufacturing process in the work cell. Spot welding represents a particularly important application in the processing category.Fundamentals of Robot Technology, Programming, and Applications 4) 3. Assembly and inspection These are two separate operations which we include together in this category. Robotic assembly is a field in which the industry is showing great interest because of its economic potential. 4. Advanced applications Rehabilitation, outer space, defense, pets, security, etc. We examine these applications of robots, as well as the general problems associated with their installation, in more detail in later chapters of the book. Qroblems 2.1 The notation scheme described in Sec. 2.1 provides a shorthand method of identifying robot configurations. For the following arm and body designations, describe the particular robot system, using sketches where possible to illustrate the robot. (a) LLR (b) RLR (c) LRR (d) LVR (e) LL- TRL 2.2. Sketch the two configurations for the jointed arm robot given in Table 2.1 2.3 For the following robot wrist notations, describe the particular wrist configuration, using sketches similar to Fig. 2.11 to illustrate the wrist. (a) :7R (b) :RT (c) :TRT ‘Analyze the differences in the capability of the three wrist configurations to position and orient an end effector. 2.4 If your school or company operates a robotics laboratory, prepare a catalog of all of the robots in the lab in terms of their respective anatomy notations. That is, write the notation scheme codes for all the robots in the lab. 2.5 One of the axes of robot is a telescoping arm with a total range of 0.50 m (slightly less than 20 in.). The robot's control memory has an 8-bit storage capacity for this axis. Determine the control resolution for the axis. 2.6 Solve Prob. 2.5 except that the robot has the following bit storage capacity in its control memory: (a) A 10-bit storage memory. (b) A 12-bit storage memory. 2.7 A large cartesian coordinate robot has one orthogonal slide with a total range of 30 in, One of the specifications on the robot is that it have a maximum control resolution of 0.010 in. On this particular axis, Determine the number of bits of storage capacity which the robot's control memory must possess to provide this level of precision.(42 industrial Robotics 2.8 One of the axes of a RRL robot is a Sliding mechanien hee oa m (about 27.5 in.). The robot's control memory hasa 10- it capacity. ina ition, it has been observed that the mechanical inaccuracies associated with movin, the arm to any given programmed point form a normally distributed random variable with the mean at the taught point and the standard deviation equal to 0.10 mm (about 0.004 in.)()4. Assume that the standard deviation is isotropic (it is equal in all directions). By definition, three standard deviations include “all” of the mechanical errors in the arm movement. With these definitions and assumptions, determine the following: (a) The control resolution for this axis. (b) The spatial resolution for this axis. (©) The defined accuracy of the robot for this axis. (@) The repeatability of the robot. 2.9 The telescoping arm of a certain industrial robot obtains its vertical motion by rotating (type R Joint) about a horizontal axis. The total range of rotation is 90°. The robot possesses a 10-bit storage capacity for this axis. When fully extended, the robot's telescoping arm measures 50 in. from the pivot point When fully retracted the arm measures 30 in. from the pivot point. (a) Determine the robot's control resolution for this axis in degrees of rotation, (®) Determine the robot's control resolution on a linear scale in both the fully extended and fully retracted Position. (©) Sketch the side view Pivoting axis, 2.10 The mechanism connecting the wrist assembly is a type T (twisting joint which can be rotated through eight full revolutions from one extreme Position to the other. It is desired to have a control resolution of plus or minus 0.2 degrees of Totation (or better). What is the required bit storage Capacity in order to achieve this resolution? 2.11 You are required to design a robot that can pick up an object of arbitrary shape from a table and place it inside a box. (a) What is the minimum number of degrees of freedom it sl () List all the possible arm configurations. () Draw their Corresponding work volumes. 2.12 Explain the relative meri drive systems, 2.13 In most assembly applications in which a Part in j robots used has at least one Prismatic (linear) axis, He in assembly? , Of the robot's work volume as determined by this hould have? nserted into another, thé ‘Ow does a linear axis help and cartesian anatomy configurati lengths. Which configuration has theReferences oe . Ss. Dickenson, Report o1 - M. P. Groover, “Indu: - R.N. Nagel . L. V. Ottinger, “Robotics for the IE: - L. L. Toepperwein, M, T. Blackman, et al., “IC, Fundamentals Of Robot Technology, Programming, and Applications 43) © 8, : ” Robot Joint Notation Scheme, Course Report fe IE 393 Lehigh University, 1984, “e JF. Engelberger, Robotics in =r Practice, AMACOM (American Management Association), New York, 1980, chaps. | and 2. strial Robots: A Primer Industrial Engineering, 54-61 (November 1980). M. P. Groover and E. W. Zimmers, Manufacturing, Prentice-Hell, Engl on the Present Technology,” Jt, CAD/CAM: Computer-Aided Design and lewood Cliffs, NJ, 1984, chap. 10. 1, “Robots: Not Yet Smart Enough,” JEEE Spectrum, 78-83 (May 1983). Terminology, Types of Robots,” /ndustrial Engineering, 28-35 (November 1981). ‘AM Robotics Application Guide,” Technical Report AFWAL-TR-80-4042, ‘Vol. I, Materials Laboratory, Air Force Wright Aeronautical Laboratories, Ohio, April, 1980.