Ergonomic Evaluation of Commercially Available Operator Lifts for by tao16360

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									Ergonomic Evaluation of
Commercially Available Operator
Lifts for Farmers with Disabilities
                    Aaron M. Yoder, Ph.D.
                    Penn State University,
                    Purdue University &
                    Breaking New Ground
                    Resource Center
Background
 692-1,697 persons in agriculturally related
  occupations or industries with a spinal
  cord injury.
 An estimated 4,500 persons with spinal
  cord injuries presently in the agricultural
  population.
 Innumerable others (~19%) with mobility
  restrictions. (e.g. strokes, arthritis,
  amputations, back injuries, and others)
Background (cont.)
   Assistive technology
    allows them to return
    to work
    • motor vehicles
    • agricultural
      equipment
    • agricultural
      workplaces
Background (cont.)
   Many will, however,
    return to work without
    the appropriate
    technology
Background (cont.)
Background (cont.)
Background (cont.)
Background (cont.)
Background (cont.)
Background (cont.)
Background (cont.)
Background (cont.)
Background (cont.)
   Purdue University’s
    Breaking New Ground
    Resource Center has
    taken a leadership
    role in assisting
    farmers and ranchers
    with disabilities
    continue farming
    safely.
Background (cont.)
Background (cont.)
Background (cont.)
Background (cont.)
Purpose
 To develop and administer a systems
 approach for evaluating ergonomic and
 safety issues related to the application of
 commercially available operator lifts used
 on agricultural and other off-road
 machinery to provide a means for
 operators with restricted mobility to gain
 access to the operator’s station.
Objective 1
 Develop and administer a standardized
 approach to conduct 11 on-site visits to
 collect observational and interview data
 from individuals who currently own and
 use both locally made and commercially
 available operator lifts to access and
 operate their agricultural equipment.
Objective 2
 Conduct a formal ergonomic analysis, with
 an emphasis on safety and usability, of two
 configurations of commercially available
 LifeEssentials operator lifts designed for
 accessing agricultural equipment.
Objective 3
 Develop a standardized user survey
 instrument for obtaining user
 demographics and feedback on operator
 lifts being used on self-propelled
 agricultural equipment and to test the
 following hypotheses:
  • Ho1: A majority of the lift users have spinal cord injuries.
  • Ho2: A majority of the lift users have use of their upper body.
  • Ho3: Owning a lift allows the lift users to continue to be productive
    in an agricultural operation.
  • Ho4: Commercially manufactured lifts are safer than home built
    models.
Objective 4
 Validate the analysis strategies and survey
  instrument by utilizing a panel of experts in
  the field of assistive technology to conduct
  an independent ergonomic evaluation of
  the operator lifts.
Objective 5
 Collect ergonomic and demographic data
 from agricultural operator lift users using
 the survey instrument previously
 mentioned in Objective 3.
Related Literature
 Secondary Injury
 Systems Approach
 Machinery Ergonomics in Agriculture
 Related Standards
 Expert Panels
 Lift Design Characteristics
Secondary Injury
 17% of farm operators had physical
  disabilities that prevented them from
  completing essential farm tasks.
 Increasing mean age of farm operators has
  led to a higher prevalence of disabling
  conditions.
 Secondary injury risk is more severe for
  individuals with SCI.
The Systems Approach
 To ensure completeness in the ergonomic
  evaluation of operator lifts.
 Hagel – “The whole is more than the sum of
  its parts”
 Gestalt psychologists recognized the
  importance of “objectiveness” or
  wholeness to human perception.
The Systems Approach (cont.)
 Explosion in use during WW II in Human
  Factors
 In 1973, Meredith et al. emphasized that the
  systems approach warranted attention and
  respect as a stand alone philosophy,
  worthy of study, separate from the
  engineering discipline.
 Used by scientists, engineers and
  agricultural safety specialists.
The Systems Approach (cont.)


                                   TOOLS
                                   EQUIPMENT
                                   WORKSTATION
                                   INFORMATION

                    PERFORMANCE
       PERSON           GAP        ESSENTIAL
         WITH                        TASK
      DISABILITY                   FUNCTIONS




                   ACCOMMODATION


                                     SYSTEM          SYSTEM
                                     INPUTS      +   OUTPUTS

                    ENVIRONMENT
Machinery Ergonomics in
Agriculture
 ASAE Publication- Human Factors (1991)
 An Ergonomic Checklist for Tractors and
  Agricultural Machinery. (Hansson, 1991)
 Cab Accessibility: How important is it?
  (Latif and Christianson, 1988)
 Safe access to farm tractors and trailers.
  (Hammer, 1991)
Machinery Ergonomics in
Agriculture (cont.)

 Risks in using modified tractors by
  operators with SCI and their co-workers
  (Willkomm, 1997)
 Assessment of work-related injury risk for
  farmers and ranchers with physical
  disabilities (Allen et al., 1995)
Related SAE Standards
• SAE J2092 – Testing of Wheelchair Lifts for Entry to or
  Exit from a Personally Licensed Vehicle
• SAE J2093 – Design Considerations for Wheelchair
  Lifts for Entry and Exit from a Personally Licensed
  Vehicle
• SAE J1725 – Structural Modifications for Personally
  Licensed Vehicles to Meet the Transportation Needs
  of Persons with Disabilities
• SAE J185 – Access Systems for Off-Road Machines
Expert Panels
Lift Design Characteristics
                     Advantages                          Disadvantages
      Mounting
       Individual    -access to and from machine at    -access to only one machine
       Machine       any location
       Independent   -access to an unlimited number of -machinery can only be accessed
                     machines                          from the location of the lift
      Type
       Standing      -least expensive option             -operator must be able to stand
       Platform
       Wheelchair    -access to wheel chair at all times -large and bulky
       Platform                                          -long transfer distances
       Parallel      -simple to design and construct     -minimal reach and lifting
       Linkage                                           distances

       Chair Lift
        rail/slide   -inexpensive to design and          -relies on winch for power
                     construct
        swing arm    -greater reach (horizontal and      -cost
                     vertical)
                     -greater range of motion in all
                     directions
      Power
       Hydraulic     -escape capacity                    -requires additional modifications
                                                         to attach
                     -more durable in harsh              -more expensive components
                     environments
       Electric
        winch        -least expensive option             -safety (see safety section)
        linear       -made to order                      -limited range of motion
        actuator
        chain        -easy to repair                   -larger power requirement
        screw        -generates large amounts of force -cost
                     -prevents freewheeling or falls
Methodology
 Objective 1 – Observational and Interview
  Analysis
 Objective 2 – Initial Ergonomic Analysis by
  the Researcher
 Objective 3 – Preliminary Questionnaire
  Development
 Objective 4 – Panel of Experts
 Objective 5 – Questionnaire Administration
Observational and Interview
Analysis
   Telephone
    Conversations
    • Informal survey
   11 Site Visits
    • Photographs
    • Informal survey
Initial Ergonomic Analysis by the
Researcher

 Heuristic Analysis and
  EMEA conducted on
  LifeEssentials
  operator lift system.
 Results used for the
  initial development of
  the lift user’s
  questionnaire.
Heuristic Analysis
    Rule                                        Description
    1.Know thy user, and YOU are not thy        The design should begin with a thorough
    user.                                       understanding of the user and the user's task.
    2.Consistency, consistency,                 Things that look the same should act the same.
    consistency.
    3.Everyone makes mistakes, so every     The user should have feedback on what they
    mistake should be fixable.              did, they should have help in finding errors and
                                            knowing how to correct them, and they should
                                            easily be able to correct the errors.
    4.When the tool is needed, it should be Information for decisions, about options, and so
    at hand.                                on needs to be there when needed; and if not
                                            visible, users should know where and when to
                                            find it.
    5.Make error messages useful to the     Error messages should be written in the user's
    user.                                   language, and tell the user how to fix the
                                            problem.
    6.Every action should have a reaction. Part of this rule implies subjectively fast and
                                            recognizable feedback.
    7.Don't overload the user's buffers.    Minimize the need to maintain information in
                                            memory (esp. short term/working memory) in
                                            order to complete a task.
    8.Keep it simple.                       Don't include things users don't need. Make it
                                            easy to find the things they do need. Don't
                                            clutter the design with features or attributes a
                                            given user doesn't want. In general, one simple
                                            useful thing is going to have more value than
                                            when it is buried in enhancements.
    9.Make it easy to be fast.              The more you do something, the easier it should
                                            be to do.
    10.Treat the user as manager.           The user should feel like they are in control.
                                            The user should always know what is
                                            happening, in terms that are useful to them.
    Table 2. Ameritech Top 10 Rules of Thumb for Usability. (Ameritech, 2000)
Error Modes and Effects Analysis
(EMEA)
Task Stage        Inappropriate or Missing         Effect                  Behavioral Basis (error mode)     Countermeasure (potential or
                  Response (errors and violations)                                                           implemented)
purchase

set-up and        installed in wrong location        damage to machine     k nowledge-based:                 step-by-step instructions
installation      freq : low                         severity : moderate   (user did not know where to       telling user where to mount lift
                                                                           mount)                            effectiveness : high
                                                                           freq : moderate

                                                                           judgement-based:                  provide easy to use instructions
                                                                           (user decided in a hurry)         effectiveness : high
                                                                           freq : moderate

ordinary use      using lift for inappropriate use   damage to machine     judgement-based:                  provide warings (lift capacities)
                  (pulling fence posts)              severity : moderate   (inappropriate use)               in user's manual and on lift
                  freq : moderate                                          freq : moderate                   effectiveness: low

                  running lift into tractor          damage to machine     sk ill-based:                     modify product
                  freq : low                         severity : moderate   (user lacks skill in operating)   use limit switches to prevent
                                                                           freq : low                        contact
                                                     personal injury                                         effectiveness: high
                                                     severity : low
                                                                                                             modify product
                                                                                                             decrease speed of lift movement
                                                                                                             effectiveness: moderate

troubleshooting

maintenance
and repair

emergency         attempt to use lift when system potential injury         judgment-based :                  warning label
procedures        looses power in emergency       severity : high          (user knew better, but decided    (do not use in emergency)
                  freq: high                                                to try anyway)                   effectiveness : low
                                                                           freq : high

disposal
Preliminary Questionnaire
Development

 Based on key areas identified from the
  preliminary observations, interviews and
  ergonomic analyses
  • Demographics
  • Ergonomic Information
     – controller usability
     – transfers
  • Mail
Panel of Experts
 Four Members
 Mailed Information
 Met for Two Days
 Heuristic Analysis
  and EMEA
 Validation of
  Questionnaire
Findings
 Observational and Interview Analysis
 Ergonomic Analysis by the Researcher
 Questionnaire Development
 Panel of Experts
 Questionnaire Administration
Panel of Experts
Heuristic Analysis

Heuristic #1: Know thy user. Is the lift/control designed logically based on the
              user?

Comments:        The lift appears to be designed for a person with "normal"
                  upper body strength.
                 Awkward placement of controller and cable routing.
                 Sling is uncomfortable.
                 Handholds would be useful for transferring.
                 The swivel seat is a good idea, but it is hard to operate.
                 The seat shape is hindering.
                 The controller needs better labeling.
                 It would be hard to use for someone with visual limitations.
                 Could it be used for more than ingress and egress?
                 Awkward placement of controller storage.
 Panel of Experts
 Heuristic Analysis (cont.)


Heuristic #2: Consistency. Does everything that looks the same act the same?

Comments:        All the controls on the controller look the same.
                 Use pictorials on the controller.
                 The control orientation could be improved.
                 When the operator is in different locations, their perspective of
                  the controller changes.
Panel of Experts
Heuristic Analysis (cont.)

Heuristic #3: Everyone makes mistakes, so every mistake should be fixable.
              Are they?

Comments:       Use redundancy for the wiring.
                Location visibility is difficult at times.
                What can be done in case of power failure?
                A learning curve is needed.
                Many pinch and crush points are present.
                Can the random rotation on the sling lift be reduced?
Panel of Experts
Heuristic Analysis (cont.)

Heuristic #4: When the tool is needed, it should be at hand. Are they?
              (remote, seatbelt, etc.)

Comments:        The controller is hard to reach and store.
                 An intermittent location for the controller would be useful.
                 Handholds are needed for transfers.
                 It would be useful if the lift could be used for maintenance.
                 A different restraint system may be useful (bar).
                 Could a circuit breaker be used in place of the main fuse?
                 It would be useful to be able to access the electronics box
                  without tools.
Panel of Experts
Heuristic Analysis (cont.)

Heuristic #5: Make error messages useful to the user. Are they?

Comments:       Trouble shooting instructions may be useful.
                A failsafe backup should be used.
                General directions would help.
                Are error messages needed?
                There is no positioning feedback.
                Interference warnings could be used.
                Audible signals could be used.
                Limits would be helpful.
Panel of Experts
Heuristic Analysis (cont.)

Heuristic #6: Every action should have a reaction. Is there feedback?

Comments:        All O.K.
                 No!
                 Bumping and dragging may not be notice.
                 Controls are not intuitive.
                 Dampen the swing in the sling.
Panel of Experts
Heuristic Analysis (cont.)


Heuristic #7: Don’t overload the user’s buffers. Is the user’s memory load
              high?

Comments:        Leg positioning depends on the user.
                 Controls are not intuitive.
                 It is mainly a simple system.
 Panel of Experts
 Heuristic Analysis (cont.)

Heuristic #8: Keep it Simple. Are any of the controls or is any part of the lift
              complex?

Comments:         The seat is too simple.
                  Controller is too complex.
                  There are no simple emergency procedures.
Panel of Experts
Heuristic Analysis (cont.)

Heuristic #9: Make it easy to be fast. Are there any points where speed could
              be improved?

Comments:        Variable lift speeds would help.
                 Improve controller design.
                 Use smart logic to program the lift to go up and in.
                 Use transfer aids to speed up transfers.
                 Fast is sometimes bad (Injuries, Sensation of poor control).
Panel of Experts
Heuristic Analysis (cont.)

Heuristic #10:Treat the user as manager. Is there any point where the user
              doesn’t feel in control?

Comments:        Swinging high in the air is very uncomfortable.
                 Lack of positioning sensations.
                 Use a joystick control.
Panel of Experts
EMEA
Task Stage   Inappropriate or             Effect                        Behavioral Basis         Countermeasure (potential
                  Missing                                                   (error mode)             or implemented)
                  Response
                  (errors and
                  violations)
purchase     error: select the wrong      effect: lift won't get used   knowledge                countermeasure: consult
                   style of lift (chair                                                               with manufacturer
                   or platform)
             freq: low                    severity: high                freq: high               effectiveness: high
             error: fit to clients        effect: lift won't get used   knowledge /              countermeasure: educate
                   needs, tractor,                                          judgment based            consumers with a
                   storage                                                                            brochure with
                   limitations                                                                        specifications
             freq: moderate               severity: high                freq: moderate           effectiveness: moderate

             error: wrong features        effect: won't use             knowledge /              countermeasure: inform
                                                                            judgment / skill          consumer
                                                                            based
             freq: low / moderate /       severity: low / moderate /    freq: low / moderate /   effectiveness: low /
                    high                       high                            high                    moderate / high
             error: installing the lift   effect: exposure to more      judgment based           countermeasure: clearer
                   on a less                    hazards                                               recommendations
                   accessible tractor                                                                 through personal
                                                                                                      contacts
             freq: low                    severity: moderate            freq: low                effectiveness: low
Panel of Experts
EMEA (cont.)
set-up and           error: install the unit in   effect: difficulty in        knowledge / skill        countermeasure: provide
      installation         the wrong                    transfers                  based                     clear instructions /
                           location                                                                          provide standardized
                                                                                                             mounting

                     freq: low / moderate /       severity: low / moderate /   freq: low / moderate /   effectiveness: low /
                            high                       high                           high                    moderate / high


                     error: improper wiring       effect: fire hazard          skill based              countermeasure: clear
                                                                                                             instructions

                     freq: moderate               severity: moderate           freq: moderate           effectiveness: moderate


                     error: improper              effect: damage to the        judgment                 countermeasure: modify
                           modifications to             tractor                                              with caution
                           the tractor


                     freq: moderate               severity: moderate           freq: moderate           effectiveness: high
Panel of Experts
EMEA (cont.)
Task Stage           Inappropriate or             Effect                        Behavioral Basis (error   Countermeasure
                          Missing                                                   mode)                     (potential or
                          Response                                                                            implemented)
                          (errors and
                          violations)
set-up and           error: select the wrong      effect: lift won't get used   knowledge / judgment /    countermeasure: consult
      installation         style of lift (chair                                     skill based                with manufacturer
                           or platform)
                     freq: moderate               severity: moderate            freq: moderate            effectiveness: high
                     error: controller wiring     effect: end pulls off         judgment                  countermeasure: better
                                                                                                               wiring techniques

                     freq: high                   severity: high                freq: high                effectiveness: high
ordinary use         error: difficulty            effect: fall                  skill based               countermeasure:
                           transferring                                                                        experience
                     freq: moderate               severity: high                freq: low                 effectiveness: moderate

                     error: activating wrong      effect: move wrong            skill based               countermeasure: better
                           switch                       direction                                              labels
                     freq: high                   severity: moderate            freq: high                effectiveness: moderate

                     error: failure to wear       effect: fall                  judgment                  countermeasure: warning
                           seatbelt                                                                            label
                     freq: moderate               severity: high                freq: moderate            effectiveness: low
Panel of Experts
EMEA (cont.)
trouble-shooting   error: fusing in control   effect: failure to operate   knowledge based          countermeasure: better
                         panel                                                                           wiring
                   freq: low                  severity: moderate           freq: moderate           effectiveness: moderate

                   error: improper dealing    effect: damage to unit       knowledge / judgment /   countermeasure:
                         with failure                                          skill based               troubleshooting
                                                                                                         manual

                   freq: moderate             severity: moderate           freq: moderate           effectiveness: moderate


maintenance        error: no instructions     effect:                      knowledge / judgment /   countermeasure: manual
     and repair          for maintenance                                       skill based

                   freq:                      severity:                    freq:                    effectiveness:
emergency          error: power failure /     effect: stranded / death     knowledge based          countermeasure: backup
     procedures          fire                                                                            system

                   freq: low                  severity: high               freq: low                effectiveness: high


                   error: poor planning       effect: entrapment           knowledge based          countermeasure: develop
                                                                                                         plan
                   freq:                      severity:                    freq:                    effectiveness:
Questionnaire
Administration

 Initial mailing sent to 127 potential lift
  users
 40 returned due to incomplete or invalid
  addresses
 60 (69%) of the remaining 87 were
  completed and returned
 4 did not qualify, leaving 56 to analyze
Questionnaire
Administration (cont.)

   Survey Comments
           Question 13 – Were you able to use the same piece of machinery after your injury

    without a lift? If yes, how did you access it?

          Pull myself up on tractor with my wife helping me, also with leg braces.

          Yes, but it requires someone (usually) to lift my legs for me. I can usually pull

           myself up and down, but it is safer with another person.

          Bought both after accident

          Had to park close to a bank and walk a plank.

          Prior to intallation of the lift I was only able to use this tractor with assistance

           from someone else.
Questionnaire
Administration (cont.)

   Survey Comments (cont.)
        Dangerously used end loader to lift me up on a platform then transfer. Not

         recommended.

        I pulled myself up on the tractor (broke leg doing it).

        It would have been hard.

        I had an electric winch hooked to the rafters in my pole barn. I used that a long

         with a hoyer seat pad to connect to the lift. Once on the tractor you had to pull the

         tractor back in the same spot to get off.

        Until 50, I was able to get on my tractors using brute strength However, I should

         have used a lift as I injured both shoulders. I have arthritis and rotator cuff tears.
Questionnaire
Administration (cont.)

   Survey Comments (cont.)
           Question 37 – Have you ever had to use the lift in an emergency situation, such as

    a fire or accident?

          I broke my femur (left) after bracing – removed myself from the tractor

          Caught combine on fire, could smell it burning, called for help save combine.

          In the event of a fire, I would not be able to get off the tractor quickly enough to

           save myself. I would have to fall off and take my chances.
Questionnaire
Administration (cont.)

   Survey Comments (cont.)
            Question 38 – Have you ever been injured or almost injured while you were using

    the lift?

           The nut that holds the seat on became loose and the seat slid and I almost fell off.

           Was bush hogging and lift arm on tractor broke while I was making a turn to the

            left on a 20-25% incline. The bush hog climbed up on wheel, but lift stopped it

            from coming up on me, but roll bar may also have stopped it, too.

           Always try to be careful to watch feet, legs, fingers, body parts when using

            (manlift).

           Not me, but there was a sheer point on one of the lifts we built and my brother

            broke a toe when using it improperly once. The sheer point has been eliminated.

           The screw broke when I was about half way up.
Questionnaire
Administration (cont.)

   Survey Comments (cont.)
        The screw broke when I was about half way up.

        I don’t dairy farm anymore. The two tractors are sold and the lifts are in my

         machine shed. I can't operate tractors anymore because of recurrent pressure sores

         problems. Everything is hired done.

        I was on the lift and it started going down itself. If my leg had been in the way I'm

         not sure what I would have done. The only happened once in five years. No

         injuries, though. Not complaining just answering the question.

        The lift broke and fell on the tractor wheel. That is why you have to brace the lift

         to the tractor to make it solid. There is to much vibration on a tractor and not have

         it braced.
Questionnaire
Administration (cont.)

   Survey Comments (cont.)
        Question 39 – Have you ever used the lift for any other purpose than lifting the

 operator into the operator’s station?

       Yes, lifting out

       My brother uses the lift to lift heavy boulders out of the field to place on the rear

        axel of the 4wd. When convenient.

       Pull fence posts, carry stuff, works great.

       I had to sell out 99 so I don't farm any more.

       It lifts a lot of stuff in my shop.

       Getting from tractor cab to van seat.

       I fell off of wheelchair. I used the lift to get back on wheelchair.
Questionnaire
Administration (cont.)

   Survey Comments (cont.)
        I fell off of wheelchair. I used the lift to get back on wheelchair.

        Used it to lift quick hitch on tractor and other implements

        Putting fuel in tractor, checking water.

        I now use it to stand up.

        For adjusting mirrors and reaching equipment.

        I used the lift to reach the side of my pole barn.

        To get into truck or tractors

        I transfer from wheelchair to lift and swing into my wood front deck mower.

        For access to pecan trees to graft the tree
Conclusions
 Observational and Interview Analysis
  •   Introduction to users and types of lifts
  •   Collected user data
  •   Initiated ideas of problems with lifts
  •   Aided in the development of the Questionnaire
Conclusions
 Ergonomic Analysis by Researcher
  • Heuristic and EMEA
  • Identified additional areas of concern
  • Aided in the development of the Questionnaire
Conclusions
 Panel of Experts
  • Heuristic and EMEA
     – Identified areas of concern
  • Validated analysis strategies
  • Validated questionnaire
Conclusions
 Questionnaire Administration
  •   H01: 75% of the lift users had SCI
  •   H02: 76% of the lift users had full use of arms
  •   H03: 17% could use same machinery before
  •   H04: Low response by locally fabricated
       – 8(16%) of 49 commercially manufactured
       – 1 (14%) of 7 locally fabricated
Recommendations
   An adaptation of the questionnaire and
    ergonomic analyses used in this study could be
    used to assess other assistive technology
    devices used in the agricultural population.
   A standard aimed at the testing and use of
    operator lifts to access agricultural and other
    off-road equipment by operators with physical
    disabilities should be submitted to the Adaptive
    Standards Committee of the Society of
    Automotive Engineers. An initial draft has been
    developed based on the review of ASAE and SAE
    standards and the findings of this study.
Recommendations (cont.)
   The information gained from this study should
    be used to justify the safety and applicability of
    operator lifts in agriculture to organizations
    that supply funding for the use of and research
    pertaining to assistive technology.
   Additional studies in the area of secondary
    injuries involving assistive technology should
    be conducted to gain a clearer perspective on
    the issue.

								
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