Troubleshooting Robotic Systems - A Professional Paper


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Troubleshooting Robotic Systems - A Professional Paper

  1. 1. ROBOTS 13Conference ProceedingsMay 7-11, 1989Gaithersburg, MarylandArticle ReprintDocumentation and Training – Troubleshooting ComplexRobotic Systems – “The Performance Aid Information flowApproach”Sponsored by:Society of Manufacturing EngineersRobotics International of SMEOne SME Drive, P.O. Box 930Dearborn, Michigan 48121
  2. 2. 15-2Documentation and Training – TroubleshootingComplex Robotic Systems – “The Performance AidInformation Flow Approach”CHARLES H. PAULThis paper details a proven method of training workers to troubleshoot, repair, and adjustcomplex integrated systems. The approach is based on the premise that technologyeducation is expensive, not cost beneficial, and ineffective when making workerscompetent. The key is providing performance-based training and effective documentationthat enable users to complete complex tasks quickly and accurately.
  3. 3. 15-3INTRODUCTIONOver the past year, we have heard much about the need for new technologyand the retooling of American industry in order to be competitive in todaysworld. Retooling is occurring and new technology is certainly being appliedas is evidenced by this conference. There is another side to this issue,however, that clearly is not being adequately addressed. This issue dealswith the basic and technical skills deficiencies of our current work force. As anation, we simply have not sufficiently invested in the people that build,operate and maintain our new equipment.A Hudson Institute study has uncovered some ominous facts about the workforce (Business Week, September 19, 1988). More than 75% of our nationsnew work force, ages 21 to 25, has limited verbal and writing skills. Basedupon the Labor Department’s scale for measuring reading, writing, andvocabulary, this group is not able to adequately interpret and apply safetyrules and equipment instructions from written documentation and writesimple reports. By the year 2000, as many as 50 million workers will fall intothis category and will need to be trained or retrained to meet the needs ofAmerican Industry.What is the impact of this lack of skill and ability at the plant level? Simply,this inability to comprehend and interact with new technology results inexcessive downtime and numerous catastrophic failures, nullifying thebenefits that the technology was expected to achieve in the first place andmany times plunging the operation into greater chaos than before it was everintroduced. What this clearly tells us is that you, as manufacturers, mustassume the responsibility for training the technicians, mechanics, andoperators that work for you. Gone are the days when competent skilledworkers could be found by simply placing a want ad in a local newspaper.Traditional education as provided by secondary schools, technical/vocationalschools, and community colleges is simply not sufficient to do the job. Thetraining provided is too generic, not specific to your equipment, notsupported by high-quality documentation, and takes too long to achievesome level of competence. It is simply the wrong approach. Traditionaleducation of a work force that needs skills right now – today is amisapplication of education.What we need to do for this group in order to address the technological literacyquestion on the shop floor, while at the same time meeting our obligations ofproduction and quality, is to provide workers with the job tools to help themtroubleshoot, operate, and maintain specific systems and equipment properly ina minimum amount of time.
  4. 4. 15-4It is critical at this time, that the distinction be made between technical manualsand the documents and training approach we will be discussing in this paper. Iam sure that every engineer has had more than one bad experience with thecontent and credibility of the information contained in technical manuals and if asengineers difficulty is experienced, it is only to think about the skill andtechnologically deficient worker to understand the importance of addressingworker competence.It is also critical at this time, to make the distinction between robotic equipmentand other machine systems. The iron and steel monsters of yesterday weremachines that were 95% mechanical, driven by an electric motor or belt drivenoff of a main plant shaft, and totally under the control of human beings. Today,machines are integrated systems of electronics, pneumatics, mechanicalsystems, and hydraulics. These machines are also computer-controlled andflexible in that they are capable of performing many tasks and functions. Theseattributes interestingly enough, apply in varying degrees to both industrial robotsand the new high-speed manufacturing equipment currently being installed andoperated in our nations most advanced manufacturing plants. From a trainingand technology transfer standpoint, industrial robots and many of the new highspeed manufacturing machines on the scene today, are one-in-the same.This brings us to the core subject of this paper. The Performance Aid InformationFlow Approach is one answer to the low technical skill levels of workers who areand will be troubleshooting and maintaining robotic as well as other complexelectronic, mechanical, and pneumatic manufacturing equipment and systems.This human engineered training and documentation approach, pioneered by theautomotive and machine tool industries, has been successful in itsimplementation and has been consequently applied to general manufacturingoperations throughout the United States.The premise of this approach is that the time and resources are not available toeducate individuals in robotics or any other complex manufacturing technologies.Traditional education as we have discussed is expensive and generally not themost cost beneficial method of making the workers in our profile job capable.Traditional educational approaches take months if not years to accomplish andwhen completed, the student is expected to transfer this generic knowledge to anactual work situation. This approach will not work with our worker group for threereasons. First, individuals within this group may not have had successfultraditional educational experiences in the past. Second, transferring genericknowledge to an actual work situation is a higher order mental skill that cannot beexpected from this group without many years of education and personaldevelopment. Third, the technology is already on your production floors. Yousimply do not have the time to wait for workers to be educated. You desperatelyneed trained mechanics and technicians today.
  5. 5. 15-5The Performance Aid Information Flow Approach is designed for this group. Itis designed to make workers job function competent, on specific equipment, to aguaranteed performance level, in a very short period of time.To provide some idea of its impact, the approach applied at one pharmaceuticalplant, has reduced the time required to troubleshoot complex control systems byas much as 50% when compared to more traditional approaches totroubleshooting.THE PERFORMANCE AID INFORMATION FLOW APPROACHThe Performance Aid Information Flow Approach is a proven method oftraining workers/technicians to troubleshoot, repair, and adjust complexintegrated systems (mechanical, hydraulic, electronic, pneumatic, etc.) to thefloor replaceable component level in approximately one-third the time whencompared to conventional methods of education. The approach, because of itsintegrated elements, guarantees trainee success to a 90/90 level of performance.This means that immediately after training, 90% of all trainees trained throughthe approach will be able to successfully troubleshoot and correct 90% of allrecurring problems on a specific piece of equipment, system, or process, withinboth time and job quality standards, when tested using an objective performancetest.The key to this approach and to effective and efficient documentation andtraining in general, is to provide users with training that quickly orients the workerto the new technology, provides a measure of system simulation, trains theworker to use the documentation tools developed to perform critical complextasks, enables workers to practice skills in an actual work environment, and thatcertifies workers as competent at the completion of training.The Performance Aid Information Flow Approach consists of four criticalelements:� Interactive Training� Information Flow Documentation� Actual Job Practice� Worker Certification
  6. 6. 15-6INTERACTIVE TRAININGThe interactive training portion of the process has two distinct functions:1. To orient the trainee to the equipment, system or process2. To provide an element of system simulationThe purpose of the first function is to orient the worker to the new equipment orprocess in terms of how the system functions, how it is controlled, and the floorreplaceable components that comprise it.A floor replaceable component is the smallest machine part orsubsystem that can be removed, replaced and adjusted on the shopfloor by a qualified technician or mechanic in an operating environment.An electric motor, for example, would be considered a floor replaceablecomponent while its windings would not. Replacing motor windingsrequires a time-consuming rebuild process.This function is inexpensively accomplished using interactive multimediatraining.When it is not practical for the trainee to interact with an existing machine,process, or system "hands-on" during training, it is necessary to build acomputer-based simulation using interactive computer-based (elearning)technology to provide a measure of "real world experience". Thistechnology provides the trainee with an opportunity to solve problems andsimulate job tasks while using the documentation provided as a componentof the approach. The touch screen and feedback capability provide criticaljob task training that is essential to the learning of any complex skill.INFORMATION FLOW DOCUMENTATIONInformation Flow Documentation GeneralThe information flow documentation is the most important element of theapproach. Information flow documentation falls under the generalumbrella of Job Performance Aid technology.
  7. 7. 15-7Job performance aids or JPAs are diagrams, checklists, and procedures,which document and standardize essential job tasks to include operation,maintenance, repair, and diagnostics. JPAs are essential to a trainees quickinternalization of learned skills and critical job knowledge.Job performance aids in the broader sense are user support "tools" whichincorporate the decision making and procedural thought processes of anexpert user. JPAs place expert user skills and knowledge in the hands of thenovice or inexperienced worker.A hand-held calculator is an example of a performance aid andalthough it is not a printed document, it is from a functionalviewpoint, quite similar.Job performance aids physically, are printed documents, diagnostic tools,expert computer-based systems, or on-line documentation. As a JPA isused, the learner mentally internalizes the information finally reaching a pointwhere the reference tool may no longer be needed (infrequently performedor critical tasks or system diagnostics will always require the use of theappropriate JPA to insure successful task accomplishment). JPAs aredesigned to be used during training as well as “on-the-job” as a guide to theperformance of a given task.Most how-to-do-it manuals are organized as step-by-step procedures,assume that the user has “some to much” prerequisite technical knowledgeof the subject, and are not sufficiently detailed to enable a user tosuccessfully complete a procedure without difficulty. When a manual or aprocedure is organized strictly as a step-by-step procedure, it does notaccount for the possibility that there may be one or more decisions, whichthe user must make before selecting that particular procedure, and thatdifferent decisions may in fact, lead to other procedures!The well-designed performance aid accounts for the varied requirements ofdifferent users in terms of training/learning, interpretation, application, andexecution. A generous application of graphics and minimal printed text arethe ingredients for user acceptance and success.The primary goal of training using this approach is to provide trainees withthe skills needed to use these primary reference tools. JPAs form the bridgebetween training and work that is missing from most learning experiences.
  8. 8. 15-8Information Flow Document TypesThere are six different types of information flow documents that form theheart of this approach. These documents or job performance aids include:� Information Flow Diagram� Signal List� Timing Diagrams� Field Replaceable Parts Locaters� Troubleshooting Instruments� Operational and Maintenance ProceduresInformation Flow DiagramsThe Information Flow Diagram is a schematic-like document that depictsall of the floor replaceable components comprising a machine or adevice to include all of the components’inputs and outputs.The format of the diagram allows a machine repair technician to trace anoutput back through the electromechanical system to the input or inputsthat caused it. This document is primarily a troubleshooting tool that theremaining information flow documents support.All of energy and force movements through the components of amachine or a device are considered signals. The types of signalsdisplayed on an information flow document would include; electricalsignals - AC power, DC power, and digital logic levels, pneumatic signals- high pressure air, low pressure air, and negative air pressure(vacuum), mechanical displacement - movement of mechanical partssuch as levers, linkages, and pistons, magnetic signals - fields thattrigger sensors, and operator actions - key presses, movement ofswitches, push buttons, etc.The drawing on the following page is an example of an information flowfor a component of a flexible manufacturing system.
  9. 9. 15-9HABCHSTART(NO)SW‘E’STOR(NC)SWINDPOWER ONGREENCBT1F1OPERATOR START CONVEYOROPERATOR EMERGENCY STOPOPERATORMAIN POWERL1L2L3L1L2L39899X1X2101102101 102104104106MPOWER ONDF2EF3F GIJKLAll floor replaceable components are shown on the diagram as boxes orrectangles. Each component is labeled for identification. The critical floorreplaceable components in this example include:� (A) CB - Circuit Breaker Switch� (B) F1 - Fuse 1� (C) T1 - Transformer 1� (D) F2 - Fuse 2� (E) F3 - Fuse3� (F) IND "POWER ON" GREEN - Green Indicator light� (G) "E" STOP (NC) SW - Emergency stop switch� (H) START (NO) SW - Start switchElectrical signals (I) are shown as thin solid lines. The arrows show thedirection of signal flow. Wire numbers are also provided for identificationpurposes. Wire or terminal connections (J) are shown as dots while ground(K) is shown using the ground symbol. Terminal numbers (L) are placednext to each terminal symbol and also where applicable along wire lines.Operator or human (M) actions as well as indicator light signals are shownas thick arrows.
  10. 10. 15-10The example information flow diagram uses the following flow symbols:This document is vastly different from common electrical schematics because itdisplays all of the inputs and outputs throughout the system. Although ourexample is electrical, it could have just as easily been a hydraulic, pneumatic, ora mechanical action problem that was being depicted.Field Replaceable Parts LocatersThe Signal List is a supporting document to the information flow diagram. Theinformation on the signal list is used by the technician when makingmeasurements at the terminals shown on the previous diagram. A samplesignal list is shown on the following page.ELECTRICALOPERATOR ACTIONMECHANICAL DISPLACEMENTPNEUMATICOPTICS / MAGNETICS
  11. 11. 15-11WIRE # SIGNAL NAME TYPE ENERGIZED DEENERG TIMENAOPERATORMAIN POWERMANUAL UP DOWNNAOPERATORSTARTMANUAL PRESS RELEASENAOPERATOREMERG.STOPMANUAL PRESS RELEASEL1 LINE 1 ELECTRICAL 01/204VAC OVACL2 LINE 2 ELECTRICAL 02/204VAC OVACL3 LINE 3 ELECTRICAL 03/204VAC OVACL1 LINE 1 ELECTRICAL 01/204VAC OVAC98 98 ELECTRICAL 011204VAC OVAC99 99 ELECTRICAL 031204VAC OVACXl Xl ELECTRICAL 1l0VAC OVACX2 GROUND ELECTRICAL OVAC OVAC101 . 101 ELECTRICAL 1l0VAC OVAC102 GROUND ELECTRICAL OVAC OVAC104 SEALING ELECTRICAL 1l0VAC OVAC106 START ELECTRICAL 1l0VAC OVACNA POWER ON OPTICAL GREEN DARKThe signal list identifies and describes all of the signals shown on theinformation flow diagram in terms of the wire number (if applicable), signalname, type of signal, the reading when energized and deenergized, and thetime if the signal is time dependent.WIRE NUMBER - Most of the signals shown in the example areelectrical and travel through system wiring. Manufacturers usuallyassign wire numbers to all of their system wiring. When they do not,wires must be traced, wire numbers assigned, and wires physicallynumbered. NA (not applicable) is entered in this column for all non-electrical signals.SIGNAL NAME - The signal name (if assigned), is the description of thesignal function (e.g. OPERATOR MAIN POWER is the physicalmovement required to turn on the main power switch).
  12. 12. 15-12TYPE - The types of signals listed include - electrical, operator (action),mechanical (displacement), pneumatic, optical, and magnetic.ENERGIZED - The value of the signal when it is ENERGIZED - "ON",TRUE, ACTIVATED (psi, volts, etc.)DEENERGIZED - The value of the signal when it is NOT ENERGIZED -"OFF", “FALSE”, DEACTIVATED, etc.TIME - If the signal is time dependent, a timing diagram is referenced.Timing diagrams are components of the signal list. The following illustrationis an example of a timing diagram.On the timing diagram, time (A) starting at to, is marked along the horizontal axis.Each increment of time, which in this example is one second, is marked as t1, t2,etc. The upper level of the signal is the energized level while the lower level ofthe signal is the deenergized level. A computer logic signal (C), for example,would have a true level of +5 VDC and a false level of ground or 0 VDC while anI/Os signals (D) would have levels of +24 VDC and ground respectively. Signalson this diagram can be positive or negative. Most of the signals on a timingdiagram are pulse signals (G) or binary logic (F) levels.Field Replaceable Parts LocatersField replaceable parts locators are simple line drawings that show the location ofeach floor replaceable component listed on the information flow diagram. Thediagrams assist the technician in locating the malfunctioning component after ithas been identified.A+5 VDCGROUNDt0+24 VDCGROUNDGROUND-15 VDCt1t2t3t4t5t6t7t8t9t = 1 secondBCDG FTiming DiagramsE
  13. 13. 15-13The field replaceable parts (A) in the drawing above are shown assimple boxes to indicate location within the enclosure. IR51 is an I/OModule for example, while wire runs (B) are shown as solid lines.IR51IR52IR53IR54 TB60TB57TB56TB55TB54TB53TB52TB51TB58CH51 CH52PS51PS52PS53DU51DS54 DS55 DS56 DS57DH54 DH55 DH56 DH57TB66TB65TB64TB63DS51 DS52 DS53DH51 DH52 DH53TB62TB61TB60TB59 XR51 LF51 DL51AB
  15. 15. 15-15Troubleshooting ProceduresAt times, depending upon system complexity, information flow diagramsare not sufficient to assist the inexperienced technician in determiningsystem malfunctions. When this occurs, it is necessary to refer to a moredefinitive troubleshooting instrument to determine the solution to systemproblems. The instruments include both computer-based and paper-basedexpert systemsExpert systems, in general, replicate the knowledge base of one orseveral expert users into a user-friendly, randomly accessed instrumentthat enables the user, without a vast amount of system knowledge, totroubleshoot complex problems quickly and accurately.Operational and Maintenance ProceduresThe written remove, replace and adjust maintenance procedures are thefinal documents comprising the information flow documentation. Theprocedures are used by technicians to repair equipment oncemalfunctioning components have been identified and located. Withoutthese standardized written or on-line procedures, the results ofdocumentation supported troubleshooting activities are limited at best.Non-standard remove, replace, and adjust procedures performed bytechnicians, often result in excessive parts usage, extended downtimebecause of a lack of an optimum repair approach, and future failuresbecause of procedures performed incorrectly. The maintenancedocuments are highly illustrated step-by-step procedures that guide thetechnician through every step of the repair from start to finish. All of theessential information needed to perform the task is provided, eliminatingany and all "guess work."ACTUAL JOB PRACTICEJob practice permits trainees to practice their newly learned skills in an actualor simulated work environment under the supervision of an instructor.Practice is absolutely essential to the success of the training conducted andthe documentation produced. During this practice opportunity, informationflow documents are used in the troubleshooting and repair of commonsystem malfunctions.
  16. 16. 15-16CERTIFICATIONCertification is the process of performance testing trainees as to their abilityto perform learned skills after the completion of job practice. Certification isconducted by instructional administrators on the job in the actual workenvironment. Trainees that are not certified are returned to training controluntil a successful certification is accomplished. Trainees are permitted to useall of the information flow documentation provided them during thecertification process.It is not the aim of this training approach to test memory because that iswhere most training methods fail. Rather, it is the aim of the approach toprovide basic knowledge of a system or process, provide documentation tosupport the worker in the troubleshooting and repair of that system orprocess, provide an opportunity to practice skills learned, and testperformance after an appropriate learning and practice period has elapsed.CONCLUSIONThe training approach discussed is based upon a five step instructionalmethod that has its roots deeply imbedded in adult learning theory. Thesesteps include:� STEP 1 - TEACH THE CONCEPT� STEP 2 - TEACH THE USE OF A JOB PERFORMANCE AID� STEP 3 - TEACH THE CRITICAL AND FREQUENT TASKS� STEP 4 - PROVIDE APPROPRIATE PRACTICE� STEP 5 - CERTIFY AND RELEASETroubleshooting complex robotic or manufacturing systems is not a "one-step" process. It can be clearly seen from the list above, that the materialsand activities provided as components of the information flow approachclosely follow the steps of this learning process. System/process/equipmentconcepts are taught using highly interactive audiovisual programs. Steps twoand three center upon the use of the information flow documentation.Appropriate practice, an essential element of learning, follows after a soundfoundation of job and system specific knowledge has been provided andobtained. The final step of this methodology, certification, insures that theexpected results have, in fact, occurred - trainee mastery of all essential jobskills to a 90/90 performance criteria.
  17. 17. 15-17What can be expected by implementing a program such as this when facedwith the need to train workers in complex system troubleshooting andmaintenance? Many benefits can be obtained by using this approach whenaddressing both new and existing technology, the most dramatic of which arelisted below:� Reduction of training times of up to 75% - training time is thetime required of a trainee to reach the same competency level of themost competent worker (learning curve) - NOT just the time requiredto complete the training program.� Elimination of repeat repair calls - the job is done right the firsttime.� Improved machine and system efficiencies - reducedtroubleshooting time and eliminated repeat calls translate into more“run” timeThe "bottom-linellof this approach is more effective operating time. A robot isthe most important element of a work cell. The capital investment in dollars topurchase this technology is only overshadowed by its impact upon theproduction process it serves. The weak link in any production process is theunknown element over which we have little control. That unknown element isthe technician that operates and maintains this equipment. A competency-based approach such as “The Performance Aid Information Flow Approach"gains control over which before was the most uncontrollable element inindustry - The performance of critical job tasks by the work force!