United States Patent [19J
`Kostas et al.
`
`[11]
`
`[45]
`
`4,360,886
`Nov. 23, 1982
`
`[75]
`
`[54] METHOD AND APPARATUS FOR
`ANALYZING THE FEASIBILITY OF
`PERFORMING A PROGRAMMED
`SEQUENCE OF MOTIONS WITH A ROBOT
`Inventors: Evans Kostas, Bay Village; Gerald
`W. Crum, Elyria; Jerome F. Walker,
`Shaker Heights, all of Ohio
`Assignee: Nordson Corporation, Amherst, Ohio
`Appl. No.: 201,221
`Filed:
`Oct. 27, 1980
`
`[73]
`[21]
`[22]
`
`[58]
`
`[56]
`
`[63]
`
`[51]
`
`. [52]
`
`Related U.S. Application Data
`Continuation-in-part of Ser. No. 137,234, Apr. 4, 1980,
`Pat. No. 4,305,028.
`Int. CI.3 ......................... G05B 19/42; B25J 9/00;
`G06F 11/30
`U.S. CI ..................................... 364/551; 318/568;
`364/513; 414/1
`Field of Search ............... 364/578, 513, 174, 190,
`364/193; 318/565, 568
`References Cited
`U.S. PATENT DOCUMENTS
`4,300,198 11/1981 Davini ................................. 364/513
`4,305,028 12/1981 Kostas et al. ....................... 318/565
`4,338,672 7/1982 Perzley et al. ...................... 364/513
`Primary Examiner-Felix D. Gruber
`Attorney, Agent, or Firm-Wood, Herron & Evans
`ABSTRACT
`[57]
`An apparatus and method for determining the feasibility
`of performing a programmed sequence of motions with
`a robot. Included is a work robot at a first location
`having a plurality of power-driven, signal-controlled,
`relatively massive links interconnected to permit rela-
`
`tive motion in plural degrees of freedom, the work
`robot having a given mechanical response characteris(cid:173)
`tic. Associated with each link of the work robot is a
`position transducer which generates a signal representa(cid:173)
`tive of the actual position of its associated work robot
`link. Also included is a portable, relatively lightweight,
`manually manipulable simulator robot located remote
`from the work robot. The simulator robot has a plural(cid:173)
`ity of different interconnected links adapted for manual
`movement in different degrees of freedom for setting a
`program of desired mechanical responses, with the links
`and degrees of freedom of the simulator robot simulat(cid:173)
`ing those of the work robot. Associated with each link
`of the simulator robot is a position transducer for gener(cid:173)
`ating a signal representative of the position of its associ(cid:173)
`ated simulator robot link. A signal recorder is provided
`at the location of the simulator robot for storing the
`position signals representative of the program of desired
`mechanical responses imparted to it by the operator. A
`work robot controller is provided at the site of the work
`robot which is responsive to the stored position signals
`for manipulating the work robot Jinks to perform the
`movements corresponding to the program of desired
`mechanical responses limited only by the given me(cid:173)
`chanical response characteristic of the work robot. An
`analyzer responsive to the actual and desired position
`signals of the work robot links is provided for generat(cid:173)
`ing error signals correlated to the extent to which the
`work robot is capable of performing the program of
`desired mechanical responses manually imparted to the
`simulator robot. An indicator responsive to the analyzer
`provides a humanly perceptible indication of the feasi(cid:173)
`bility.
`
`14 Claims; 9 Drawing Figures
`
`..<IJJ
`'-;i!tJ5
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`,r,i'/,i'
`
`INDICATOR
`
`~oo
`'--
`
`ROBOT
`CONTROLLER
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`RN
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`PROCESSOR
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`INTERFACE
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`MEMORY
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`-.C/6
`
`1
`
`IROBOT 2013
`Shenzhen Zhiyi Technology v. iRobot
`IPR2017-02061
`
`

`

`U.S. Patent Nov. 23, 1982
`
`Sheet 1 of 5
`
`4,360,886
`
`1.58
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`

`

`U.S. Patent Nov. 23, 1982
`
`Sheet 3 of 5
`
`4,360,886
`
`RECORD SIMULATOR ROBOT
`LINK POSITIONS a ON/OFF
`SWITCH CONDITIONS
`
`SIMULATOR ROBOT
`DATA COLLECTION
`PHASE ONE
`
`.--~~-'-~~~-~
`AID CONVERSION OF
`DESIRED WORK ROBOT
`LINK POSITION
`
`NO
`
`.JIJ4
`/
`
`A/D CONVERSION OF
`DESIRED ON/OFF SW.
`CONDITION
`
`FORMAT a BUFFER
`STORE DESIRED
`POSITIONS a ON/OFF
`SW. CONDITIONS
`IN
`M.P. RAM
`
`WRITE DESIRED
`POSIT IONS a ON/OFF
`SW. CONDITIONS IN
`DISC
`
`NO
`
`SIMULATOR ROBOT
`DATA CONVERSION
`PHASE TWO
`~,44
`
`4
`
`

`

`U.S. Patent Nov. 23, 1982
`
`Sheet 4 of 5
`
`4,360,886
`
`J'z. FETCH DESIRED POSITION
`
`OF ROBOT LINK FROM
`ROBOT CONTROLLER RAM
`
`.J/3
`~ ..... IN_PU_T_A:-CT_U..1.A_L_P_O_S_IT-IO_N_OF_
`ROBOT LINK FROM LINK
`POSITION TRANSDUCER TO
`ROBOT CONTROLLER
`J'/4- .------..1.-----(cid:173)
`J COMPUTE ERROR IN ROBOT
`'-+- CONTROLLER BETWEEN
`DESIRED a ACTUAL
`LINK POSITIONS
`
`.Jf:!_ OUTPUT ERROR FROM
`ROBOT CONTROLLER TO
`ROBOT LINK ACTUATOR
`
`.f~. STORE ACTUAL ROBOT
`._.. LINK POSITION IN
`ROBOT CONTROLLER RAM
`
`3{!'. UTPUT DESIRED ON/OFF
`SW. CONDITION TO ROBO
`ON/OFF SW. FROM ROBOT
`CONTROLLER
`
`NO
`
`.J()6
`~ ~EAD DESIRED
`OSITIONS a ON/OFF
`SW. CONDITIONS
`FROM DISC
`.JIJ71
`BUFFER STORE DESIRE
`POSITIONS a ON/OFF
`SW. CONDITION
`IN
`M. P. RAM
`.31J8~
`TRANSFER DESIRED
`POSITIONS a ON/OFF
`SW. CONDITION TO
`ROBOT CONTROLLER
`
`.f&.9~
`EXECUTE ROBOT
`CONTROLLER PROGRAM
`
`.J/()~
`TRANSFER ACTUAL
`POSITIONS FROM ROBO
`CONTROLLER RAM
`TO M.P. RAM
`
`JI/~ ..----------
`
`TRANSFER ACTUAL
`POSITIONS TO DISC
`FROM M. P. RAM
`
`WORK ROBOT DRIVE
`PHASE THREE
`
`5
`
`

`

`U.S. Patent Nov. 23, 1982
`
`Sheet 5 of 5
`
`4,360,886
`
`.)£0
`L,
`
`.J.21
`L--
`
`TRANSFER DESIRED POSITIONS
`a ON/OFF SW. CONDITION
`FROM DISC TO M.P. RAM
`
`TRANSFER ACTUAL POSITIONS
`FROM DISC TO M. P. RAM
`
`ANALYSIS S
`INDICATION
`PHASE FIVE
`
`~1~e
`
`32Z
`'----*'"
`
`C~PUTE POSITION Bi
`V OC ITY ERRORS
`
`NO
`
`J,C3
`L.
`
`PRINT POSITrON a VELOCITY
`ERRORS IN CONJUNCTION WITH
`ON/OFF SW. CONDITION
`
`NO
`
`.1124
`L.
`PLOT POSITION a VELOCITY
`ERRORS IN CONJUNCTION WITH
`ON/OFF SW. CONDITION
`
`a::
`0
`a::
`a::
`I.LI
`
`I
`
`6
`
`

`

`METHOD AND APPARATUS FOR ANALYZING
`THE FEASIBILITY OF PERFORMING A
`PROGRAMMED SEQUENCE OF MOTIONS WITH
`A ROBOT
`
`This is a continuation-in-part of Ser. No. 137 ,234 filed
`Apr. 4, 1980 now U.S. Pat. No. 4,305,028, entitled "Sys(cid:173)
`tem for Evaluating the Capability of a Work-Perform(cid:173)
`ing Robot to Reproduce a Programmed Series of Mo- IO
`tions".
`This invention relates to work-performing robots,
`and more particularly to an apparatus and method for
`determining the feasibility of performing a programmed
`sequence of motions with a work-performing robot 15
`having a limited mechanical response characteristic.
`A work-performing robot typically includes a plural-
`ity of links, at least some of which are rela~ively mas(cid:173)
`sive, interconnected to provide relative motion in a
`plurality of degrees of freedom. The links are each 20
`provided with a signal-controlled actuator for power(cid:173)
`ing the respective links, as well as a position transducer
`for providing a real-time signal correlated to the actual
`position of the respective robot links. Each work-per(cid:173)
`forming robot has a particular mechanical response 25
`characteristic which has certain inherent limitations. As
`a consequence, a work-performing robot may be inca(cid:173)
`pable of performing a desired sequence of programmed
`motions.
`For example, it is possible that the programmed mo- 30
`tion sequence requires the work robot links to move
`with velocities which the link actuators are incapable of
`producing by reason of certain inherent limitations in
`their size and/or capacity. Independent of whether the
`programmed motions will overload the link actuators, 35
`the work robot may be incapable of performing the
`desired sequence because its power source is over(cid:173)
`loaded. More specifically, the power source for the
`actuators, such as an hydraulic pump if actuators of the
`electrohydraulic type are used, may have its power 40
`limit, or capacity, exceeded, that is, the pump may be
`incapable of providing pressurized fluid simultaneously
`to all the actuators at rates sufficient to simultaneously
`drive their respective links at the desired programmed
`velocities. Independent of limitations of the system 45
`pump and/or link actuators, the work-performing robot
`may be unable to execute a series of programmed mo(cid:173)
`tions due to limitations inherent in the electronic con(cid:173)
`troller which processes the programmed sequence of
`link command signals which ultimately control the link 50
`actuators.
`It is often desirable to know in advance whether or
`not a particular programmed sequence of motions can
`be performed by a given work robot having specified
`controller, actuator, and/or pump limitations. For ex- 55
`ample, if a prospective robot user is contemplating use
`of a work-performing robot for a specific task, such as
`spray coating a specific article, the prospective user
`may wish to determine at the outset, that is, before
`actual purchase and installation of the work-performing 60
`robot, whether the specific robot under consideration
`can perform the task which the prospective user con(cid:173)
`templates. Without such advance information, it is en(cid:173)
`tirely possible that the prospective robot user could
`purchase and install a work robot to perform a specific 65
`task which the robot, by reason of inherent physical
`limitations in its actuators, controller, and/or power
`supply, is incapable of performing.
`
`1
`
`4,360,886
`
`2
`A partial solution to this problem is available in situa(cid:173)
`tions where the specific article which the prospective
`robot user wishes to spray coat is sufficiently small in
`size and weight to be transported to the site of the robot
`5 manufacturer. In such cases an effort can be made at the
`site of the robot manufacturer to spray coat the article
`using an actual work-performing robot of the general
`type the prospective robot user is contemplating using.
`If the work-performing robot is unable to satisfactorily
`spray coat the specific article under consideration due
`to its inherent limitations, the prospective robot user is
`advised and installation at the prospeetive user's facility
`of a robot incapable of doing the desired task is avoided.
`Of course, if the article which the prospective work
`robot user proposes to spray coat is too massive and
`bulky to be transported to the site of the work robot, the
`capability of the work robot for spray coating the arti(cid:173)
`cle in question cannot be evaluated in the foregoing
`manner. Similarly, and even ifthe proposed article itself
`is sufficiently small and lightweight to facilitate conve(cid:173)
`nient transport to the site of the work robot, it may be.
`impossible to evaluate the capability of the work robot
`for spray coating the article in question for a further
`reason. Specifically, it may not be possible to produce at
`the site of the work robot the environment of the article
`which is to be spray coated. For example, the article to
`be spray coated may be moving along a unique and
`unusual path on an automated conveyor, which con-
`veyor cannot be conveniently and/or economically
`duplicated at the site of the work robot. As a conse(cid:173)
`quence, even though the article itself can be transported
`to the work robot, its environment cannot, and hence it
`is impossible to evaluate the feasibility of spray coating
`the article in question by bringing it to the work robot
`site.
`Accordingly, when either the article itself cannot be
`transported to the site of the work robot and/or the
`specific environment of the article cannot be simulated
`at the work robot site, it has heretofore been difficult to
`accurately and reliably predict whether the robot can
`satisfactorily be used to spray coat the article. It has
`been, therefore, an objective of this invention to pro(cid:173)
`vide a method and apparatus for determining the feasi(cid:173)
`bility of performing a programmed sequence of motions
`with a work robot having an inherently limited mechan-
`ical response characteristic, which apparatus and
`method can be utilized in situations where it is not possi(cid:173)
`ble to duplicate the workpiece and/or the environment
`of the workpiece at the site of the work robot, and it is,
`therefore, not possible to actually attempt to perform
`the desired sequence of motions with respect to the
`desired workpiece in its real environment with an actual
`work robot.
`The foregoing objective has been accomplished in
`accordance with certain principles of this invention by
`providing a portable, relatively lightweight, manually
`manipulable simulator robot at the site of the workpiece
`whereat there exists no work robot. The simulator
`robot has plural links and degrees of freedom simulating
`those of the work robot and a position transducer asso(cid:173)
`ciated with each simulator robot link for generating
`position signals representative of the position of the
`associated simulator robot link. The simulator robot is
`manually manipulated at the site of the workpiece for
`setting a program of desired mechanical responses
`which it is ultimately desired to have the work robot
`perform on the workpiece. The position signals output
`
`7
`
`

`

`4,360,886
`
`3
`from the simulator robot link transducers are recorded
`on a signal recorder, preferably of the wideband type.
`The work robot, which is located remote from the
`site of the workpiece whereat the simulator robot is
`located, is driven with the recorded position signals 5
`generated when the simulator robot was manually ma(cid:173)
`nipulated through the desired programmed sequence of
`motions at the workpiece site, for performing work
`robot link movements corresponding to the program of
`desired mechanical responses limited only by the me- 10
`chanical response characteristic of the work robot.
`While the work robot is being driven at its situs by the
`recorded signals generated at the time the simulator
`robot was manipulated
`through
`the desired pro(cid:173)
`grammed sequence of motions at the workpiece site, 15
`actual position signals are provided by transducers asso(cid:173)
`ciated with the work robot links which represent the
`actual position of the various work robot links. Utilizing
`an analyzer input with both the actual work robot link
`position signals and the desired work robot link position 20
`signals provided by the recorder, error signals corre(cid:173)
`lated to the extent to which the work robot is capable of
`performing the program of desired mechanical re(cid:173)
`sponses manually imparted to the simulator robot are
`derived. The error signals are input to a suitable indicat- 25
`ing device which provides a humanly perceptible indi(cid:173)
`cation of the feasibility of the work robot for perform(cid:173)
`ing the program of desired mechanical responses im(cid:173)
`parted to the simulator robot at the workpiece site.
`In a preferred embodiment of the invention the error 30
`derivation includes generating error signals correlated
`to the difference between the actual position of the
`work robot links and the desired position imparted to
`the simulator robot links at the workpiece site as re(cid:173)
`corded in the recorder. These positional error signals 35
`are then input to the indicating device which displays
`information correlated to the positional differences be(cid:173)
`tween the actual and desired work robot link positions.
`In accordance with a further aspect of the invention,
`a switch element associated with the simulator robot is 40
`provided which is manually operable between OFF and
`ON conditions of the utilization device movable by the
`work robot. The ON/OFF switch may, for example,
`constitute the control switch on a spray coating gun.
`Means are also provided to monitor and record the 45
`condition of the switch when the simulator robot is
`manipulated through the different desired programmed
`sequence of motions at the workpiece site. The indica(cid:173)
`tor device is responsive to the recorded switch condi.(cid:173)
`tion signals for displaying the condition of the switch in 50
`association with the displayed information correlated to
`the positional difference between the actual and desired
`work robot positions. In this way the feasibility of the
`work robot for performing the program of desired me(cid:173)
`chanical responses is analyzed in dependence upon the 55
`condition of the switch. Differences between actual and
`desired work robot position which exist when the
`switch is OFF, for example, representative of when a
`spray coating gun is not actuated, may possibly be ig(cid:173)
`nored, in which event the work robot is deemed capable 60
`of performing a programmed series of motions satisfac(cid:173)
`torily even though there are positional discrepancies
`between the desired and actual work robot link mo(cid:173)
`tions.
`In accordance with a still further aspect of the inven(cid:173)
`tion, the analyzer generates error signals correlated to
`the difference between the actual velocity of the work
`robot links and the desired velocity imparted to the
`
`4
`simulator robot links during manual programming of
`the desired sequence of motions. The indicator displays
`information correlated to the velocity differences be-
`tween the actual and desired work robot link velocities
`in association with the displayed information represent(cid:173)
`ing the condition of the ON/OFF switch and the posi-
`tional differences between the desired and actual work
`robot link positions. The coordinated display of posi(cid:173)
`tional and velocity errors along with the ON/OFF
`condition of the switch further enhances the determi~a­
`tion of work robot utility for a given task.
`For example, if no significant position or velocity
`errors exist, the work robot is clearly capable of per(cid:173)
`forming the required task. If errors exist, for example, in
`a spray coating operation, but they occur when the
`spray coating gun is not actuated, the errors likely can
`be ignored since coating material is not being applied to
`the article at the time the error(s) are present. If errors
`exist when the spray coating gun is activated and coat(cid:173)
`ing material is being applied to the article, the nature of
`the spray coating task may be such that the errors can
`still be ignored. For example, experience has demon(cid:173)
`strated that positional errors of ~ inch or more can be
`tolerated when rust inhibitor is being applied to an auto(cid:173)
`mobile underbody. Of course, positional errors of this
`magnitude or even less are totally unsatisfactory if the
`spray coating task involves applying decorative pin(cid:173)
`stripes to the exterior of an automobile. Similarly, ve(cid:173)
`locity errors which manifest themselves as variations in
`paint thickness, may or may not be tolerable depending
`on the nature of the article being coated. Errors of this
`type in spray coating a tractor engine can be ignored,
`while they cannot be when applying reflective coating
`to glass in the manufacture of a mirror. Thus, with this
`invention it is possible to evaluate the feasibility of exe(cid:173)
`cuting a desired motion sequence, such as, spray coating
`a workpiece, with a work robot having an inherently
`limited mechanical response characteristic in situations
`where the workpiece and/or its environment cannot be
`duplicated at the site of the work robot and an actual
`attempt made to perform the desired spray coating or
`other operation on the workpiece itself.
`These and other features, objectives, and advantages
`of the invention will become more readily apparent
`from a detailed description thereof taken in conjunction
`with the drawings in which:
`FIG. 1 is a perspective view, in schematic form, of a
`typical work-performing robot showing the general
`relationship of the relatively massive robot links and
`their respectively assor;;iated actuators and position
`transducers.
`FIG. 2 is a perspective view, in schematic form, of a
`lightweight, hand manipulable simulator robot showing
`the general relationship of the simulator links and asso(cid:173)
`ciated position transducers.
`FIG. 3 is a circuit diagram in block format of a pre(cid:173)
`ferred embodiment of the invention.
`.FIGS. 4a to 4e show flow charts of the preferred
`embodiment of the invention.
`FIG. 5 is a typical graphical plot of work robot link
`velocity and positional errors corrdinated with the de(cid:173)
`sired condition of the ON/OFF work robot output
`device switch.
`With reference to FIG. 1, a typical work-performing
`65 robot, with respect to which this invention is useful in
`assessing feasibility to perform a series of motions on a
`specific workpiece, is seen to include a base 10 which
`rests on the floor or other appropriate surface for sup-
`
`8
`
`

`

`4,360,886
`
`5
`porting the robot. Extending from the base 10 are plu(cid:173)
`ral, series-connected, elongated, articulated members or
`links 12, 14, 16, 18, 20, and 22 which, in the preferred
`embodiment, provide the robot with several, in this
`instance six, degrees of freedom. In practice, the links 5
`12, 14, 16, 18, 20, and 22 collectively constitute a rela(cid:173)
`tively large mass. For example, the links 12, 14, and 16
`are each approximately 1-4 feet in length, and typically
`weigh in the range of 10-400 pounds each. The links 18,
`20, and 22 which, in the work-performing robot shown IO
`in FIG. 1 constitute a wrist, typically are significantly
`less massive than the links 12, 14, and 16, although this
`is not necessarily the case.
`The link 12 is vertically disposed and mounted to the
`base 10 by a suitable joint which permits the link to 15
`rotate about its longitudinal axis which is coincident
`with the X axis. An actuator 23 is associated with the
`link 12, and is responsive to a position error ~ignal pro(cid:173)
`vided by a conventional robot controller (not shown in
`FIG. 1) to facilitate selective, bidirectional, angular 20
`motion of the link 12 in an azimuthal direction about its
`longitudinal axis to the desired link position. Also asso(cid:173)
`ciated with the link 12 is a position transducer 24 which
`provides an electrical signal correlated to the actual
`angular, or azimuthal, position of the link 12 relative to 25
`the base 10.
`The link 14 at its lower end is connected to the upper
`end of the link 12 by a suitable joint for permitting
`pivotal, elevational movement of the link 14 in a verti(cid:173)
`cal plane about a horizontal axis 26 which is perpendic- 30
`ular to the X axis and parallel to the Y-Z plane. Associ(cid:173)
`ated with the link 14 is an actuator 28 which is respon(cid:173)
`sive to a position error signal from the robot controller
`and facilitates selective, bidirectional, elevational, piv(cid:173)
`otal movement of the link 14 about horizontal axis 26 to 35
`the desired link position. Also associated with the link
`14 is a position transducer 30 which provides an electri(cid:173)
`cal signal correlated to the actual elevational position of
`the link 14 relative to the link 12.
`The link 16 at its inner end is connected to the upper 40
`end of the link 14 by a suitable joint for permitting the
`link 16 to move in a vertical plane about horizontal axis
`32 which is parallel to axis 26. A suitable transducer 34
`is associated with the link 16 for providing an electrical
`signal correlated to the actual angular elevational posi- 45
`tion of the link 16 with respect to the link 14. An actua(cid:173)
`tor 33, associated with the link 16, is responsive to a
`position error signal from the robot controller and facil(cid:173)
`itates selective, bidirectional, elevational, pivotal move(cid:173)
`ment of the link 14 about horizontal axis 32 to the de- 50
`sired link position.
`The actuator 23 which bidirectionally drives the link
`12 about the X axis provides the work-performing robot
`with one degree of freedom, namely, azimuthal· posi(cid:173)
`tioning motion, while the actuators 28 and 33 which 55
`bidirectionally drive the link 14 and link 16, respec(cid:173)
`tively, provide the robot with two degrees of freedom,
`each in an elevational direction.
`The articulated links 18, 20, and 22 collectively con(cid:173)
`stitute a wrist. Link 18 at its inner end is connected via 60
`a suitable joint to the outer end of the link 16. An actua(cid:173)
`tor 44 is associated with the wrist member 18 for bidi(cid:173)
`rectionally rotating, when input with suitable position
`error signals from the robot controller, the wrist mem(cid:173)
`ber 18 to the desired link position about its longitudinal 65
`axis which is coincident with the longitudinal axis of the
`link 16. A suitable position transducer 46 is associated
`with the link 18 for providing an electrical signal corre-
`
`6
`lated to the actual relative rotational position of the link
`18 with respect to the link 16.
`The link 20 is connected at its inner end via a suitable
`joint to the outer end of the link 18 for providing rota(cid:173)
`tional movement of link 20 about its longitudinal axis
`which is perpendicular to the longitudinal axis of link
`18. An actuator 48 is associated with link 20, and when
`input with suitable position error signals from the robot
`controller, bidirectionally rotates link 20 about its longi(cid:173)
`tudinal axis perpendicular to the longitudinal axis oflink
`18 to the desired link position. A suitable position trans(cid:173)
`ducer 50 is also associated with link 20 for providing an
`electrical output correlated to the actual rotational posi(cid:173)
`tion of this link relative to link 18.
`Link 22 is connected via a suitable joint to the outer
`end of link 20 to facilitate rotation of link 22 about its
`longitudinal axis which is disposed perpendicularly to
`the longitudinal axis of link 20. An actuator 52 associ(cid:173)
`ated with link 22, when inpµt with suitable position
`error signals from the robot controller, facilitates bidi(cid:173)
`rectional motion of link 22 about its longitudinal axis to
`the desired link position. A transducer 54, also associ(cid:173)
`ated with link 22, provides ari electrical signal output
`correlated to the actual relative rotational position of
`link 22 relative to link 20.
`Link 22 constitutes the mechanical output element of
`the work-performing robot. While the mechanical out(cid:173)
`put of the robot can be utilized for positioning a wide
`variety of devices, in the preferred form of the inven(cid:173)
`tion the work-performing robot is utilized to position a
`spray coating gun 58 having a barrel 58a with a nozzle
`58b which emits coating particles. The gun handle 58c is
`mounted to the upper end of the wrist link 22. The gun
`handle 58c mounts a suitable trigger mechanism 58d
`which, when actuated by a suitable signal-operated
`device (not shown), functions to control the emission of
`coating particles from the nozzle 58b of the spray gun
`58.
`The longitudinal rotational axes of wrist links 18, 20,
`and 22 are mutually perpendicular, and accordingly
`constitute three degrees of freedom for the robot. These
`three degrees of freedom, coupled with the three de(cid:173)
`grees of freedom of the links 12, 14, and 16, provide a
`total of six degrees of freedom for the work-performing
`robot.
`In the operation of the work-performing robot shown
`in FIG. 1, a series of programmed, i.e., desired, link
`position signals stored in a suitable memory device of
`the robot controller are periodically retrieved and com(cid:173)
`pared against the actual link position signals provided
`by the link position transducers 24, 30, 34, 46, 50, and
`54, and in response thereto the link positional error
`signals are generated for each of the links 12, 14, 16, 18,
`20, and 22. The positional error signals for the various
`links 12, 14, 16, 18, 20, and 22 are then input to the
`various link actuators, 23, 28, 33, 44, 48, and 52, which
`typically are of the servo-controlled electrohydraulic
`type, for moving the links to the desired, or pro(cid:173)
`grammed, positions which in tum reduce the positional
`error signals to zero. Thus, the links of the work-per(cid:173)
`forming robot of FIG. 1 are driven through the pro(cid:173)
`grammed sequence of desired motions, utilizing closed(cid:173)
`loop servo techniques, by periodically comparing de(cid:173)
`sired position signals retrieved from the memory of the
`robot controller with actual link position signals from
`their associated position transducers, and using the re·
`suiting positional error signals associated with the dif-
`
`9
`
`

`

`4,360,886
`
`7
`ferent links to drive the various link actuators to the
`desired, or programmed, positions.
`Since the robot controller, actuators, position trans(cid:173)
`ducers, closed-loop servo controls, and the like of the
`work-performing robot of FIG. 1 are well known and 5
`form no part of this invention, they are not further
`discussed in detail herein, except to the extent necessary
`to an understanding of the flow charts of FIGS. 4a-4e.
`The robot simulator, shown in FIG. 2, which is useful
`in the work robot feasibility analysis system of this IO
`invention, includes a tripod base 110 from which ex(cid:173)
`tends vertically a link 112 which is connected to the
`base for rotational movement about a vertical axis by a
`rotary joint 123. A position transducer 124 associated
`with the link 112 and base 110 provides an electrical 15
`signal correlated to the actual angular position of the
`link 112 relative to the stationary base. Pivotally con(cid:173)
`nected to the upper end of the link 112 by a rotary joint
`128 is a link 114 which pivots about axis 126. An angular
`position transducer 130 associated with the joint 128 20
`and the link 114 provides an electrical signal correlated
`to the actual angular position of the link 114 with re(cid:173)
`spect to the link 112. A link 116 connects to the link 114
`via a rotary joint 133 for pivotal movement about axis
`132. An angular position transducer 134 associated with 25
`the joint 133 and the link 116 provides an electrical
`signal correlated to the actual angular position of the
`link 116 with respect to the link 114.
`Also included in the robot simulator depicted in FIG.
`2 are links 118, 120, and 122 which are pivotally con- 30
`nected to links 116, 118, and 120, respectively, via ro(cid:173)
`tary joints 144, 148, and 152, respectively. Angular
`position transducers 146, 150, and 154 associated with
`the rotary joints 144, 148, and 152, respectively, and the
`links 118, 120, and 122, respectively, provide electrical 35
`signals correlated to the actual angular position of the
`links 118, 120, and 122 with respect to the links 116, 118,
`and 120, respectively.
`Mounted to the link 122 is a spray gun 158 having a
`barrel 158a, a nozzle 158b, and a handle 158c which 40
`mounts an ON/OFF switch 158d.
`The length of the links 112, 114, 116, 118, 120, and
`122 of the simulator robot of FIG. 2 are identical to the
`lengths of the links 12, 14, 16, 18, 20, and 22, respec(cid:173)
`tively, of the work-performing robot shown in FIG. 1. 45
`Of course, the mass of the links 112, 114, 116, 118, 120,
`and 122 of the simulator robot of FIG. 2 are a mere
`fraction of that of their counterpart links 12, 14, 16, 18,
`20, and 22 of the considerably more massive work-per(cid:173)
`forming robot shown in FIG. 1. Similarly, the joints 50
`123, 128, 133, 144, 148, and 152 of the simulator robot
`permit the same type of pivotal motion between their
`respectively associated links 112, 114, 116, 118, 120, and
`122 as their counterpart rotary actuators 23, 28, 33, 44,
`48, and 52 provide for their respectively associated links 55
`12, 14, 16, 18, 20, and 22 of the work-performing robot.
`When the spray gun 158 is moved manually by an
`operator grasping the handle 158c thereof through a
`sequence of motions necessary to spray coat an object,
`which is possible due to its lightweight construction, 60
`the various links 112, 114, 116, 118, 120, and 122 of the
`simulator robot move through a sequence of motions.
`Simultaneously, the transducers 124, 130, 134, 146, 150,
`and 154 of the simulator robot associated with the vari(cid:173)
`ous simulator robot links 112, 114, 116, 118, 120, and 122