Design of an ergonomic control lever for wheel loader attachments

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1 2 3 4 Table 3.1.List of recommendations 1 Göran Hägg, Professor, KTH, verbal contact (mail) 27 th of September 2011 2 Ralf Rosenberg, Designer Msd, Chalmers, verbal contact 27 th September 2011 30 Expressed recommendations References Design of a buttons’ positions, shape and surface must be performed in such way that the tactile sense and positioning sense automatically sense and interpret a pattern. Multiple references of tactility are recommended when button don’t follow the lever/joystick The four most important buttons should be placed corresponding to the relaxed hands finger placement. An angle of 100 -‐110° for the elbow angle is recommended during lever work. The angle from the transversal plane to the hand should be around 10-‐20°. Adolfsson, Öberg och Torén (2004 p. 10-‐12) Adolfsson, Öberg och Torén (2004 p. 10-‐12) Adolfsson, Öberg och Torén (2004 p. 10-‐12) Adolfsson, Öberg och Torén (2004 p. 10-‐12) 5 The angle from horizontal to a pistol grip should be 70°. Gilbert, Hahn & Gilmore (1988) 6 A joystick or lever should keep the wrist in angles as close to neutral plane as possible. Göran Hägg 1 , Ralf Rosenberg 2 , AFS 1998,Adolfsson, Öberg och Torén (2004 p. 10-‐12) 7 Exert force in a 90-‐degree angle against an axis rather than along it. Haslegrave & Pheasant (2006) 8 Sharp edges on pressure surfaces should be avoided to eliminate force hotspots (finger grooves, handle shapes etc.). 9 Handles should give good grip and adhesion for precision. AFS (1998) 10 The thumb can maneuver two buttons or one toggle switch 11 Avoid extended postures of the wrist if designing mini-‐joysticks. 12 Avoid joysticks for just two hydraulic functions Haslegrave & Pheasant, (2006). AFS (1998) Adolfsson, Öberg och Torén (2004 p. 10-‐12) Adolfsson, Öberg och Torén (2004 p. 10-‐12) Adolfsson, Öberg och Torén (2004 p. 10-‐12) 13 Handles for gripping should have a diameter of 30 – 50 mm Haslegrave & Pheasant (2006) 14 Precision handles should be between 8 – 16 mm in diameter Haslegrave & Pheasant (2006) 15 16 The levers on the control unit should be adjustable for different hand sizes or fit a wide spread of hand sizes Activate many muscles for one movement, but the arm should not move at all, and the forearm to a minimum Gellerstedt (2000), AFS (1998) Ralf Rosenberg 17 Arm and shoulder should be fully supported to avoid static workload. Ralf Rosenberg 18 Job rotation. Other tasks that differs from each other. AFS (1998) 19 Small beaks in the work, so called “Micro-‐brakes” would be preferred. Gellerstedt (2000) 20 21 Handles used in gripping should have a slight curvature (but not create hotspots) to follow the shape of the hand.25. The cross section of a handle should be somewhat egg-‐shaped to set the direction of the handle. Haslegrave & Pheasant (2006) Haslegrave & Pheasant (2006). 22 The angle from transverse plane to pistol grip should be 70°. Gilbert, Hahn & Gilmore (1988)
4 Methods This chapter consists of descriptions of the methods used in the project. More detailed descriptions of the execution of the methods are presented in the report in the respective chapters where they are used. The methods are grouped depending on their purpose or outcome from the methods: data colleting, analysis methods for ergonomic issues, idea generation and concept evaluation methods. 4.1 Data collecting methods These methods are used for collecting information of the human-machine system and the work situation. They regard people’s thoughts and interaction with the system. 4.1.1 Observations To study phenomenon or events, different technical aids can be used in addition to the human senses when observing the situation. Observations can be performed with different levels of participation, and the subjects can more or less be aware of the fact they are being observed (Höst et al, 2006). Observations made in this project were executed as participating observations with aids such as video recorders and additional questionnaires and semi-structured interviews. This means that the observers had low interaction, and the observed subjects were fully aware of the observers In this project the first observation session was made to study hand postures of the operators (Chapter 6.2.3), the second observation session was made to understand the operators’ mental model (Chapter 6.4.2) and the last observation session was made to study hand postures of the reference group when evaluating the first prototype (Chapter 11.2.2). 4.1.2 Questionnaire A method for collecting data for a large number of people with most common predefined and set question is by using questionnaires. These questions are answered by the interviewee himself/herself. Questions, or statements, must be short, simple, precise, straightforward and not leading, among other aspects. A common way to collect data on opinions is let the interviewee take side to a statement, by using a so-called Likert-scale; the user can agree, or not agree (to some extent) to the statement. This scale is often discretizes into intervals of five or seven degrees, from fully-agree to not-agree (Höst et al, 2006). Questionnaires were in this project used as a compliment to the observations and as a support for the semi-structured interviews. Questionnaires were used to gather subjective input of the operator’s perceived discomforts (Chapter 6.3.3). Questionnaires were also used during the concept generation phase when the reference group evaluated the concepts (Chapter 8.3 and 9.3) and during the concept evaluation phase when the reference group evaluated the functional prototype (Chapter 11.2.4). 31
Page 1 and 2: Design of an ergonomic control leve
Page 3: Acknowledgements This thesis work h
Page 7 and 8: Content 1 Introduction ............
Page 9 and 10: 1 Introduction The underlying reaso
Page 11 and 12: 1.3 Question formulation The studie
Page 13 and 14: 2 Current situation To get a deeper
Page 15 and 16: Figure.2.3. Control lever unit with
Page 17 and 18: Figure 2.4.Lifting and tilting the
Page 19 and 20: 2.2.2 Technical terms related to jo
Page 21 and 22: 3 Theory The theory research gather
Page 23 and 24: Angles of movement The hand has the
Page 25 and 26: 3.1.4 Ergonomic issues related to t
Page 27 and 28: 3.2 Cognitive ergonomics It seems t
Page 29: 3.3 Standards and recommendations T
Page 33 and 34: Simulation interview gives users vi
Page 35 and 36: 4.3.3 Morphological matrix Morpholo
Page 37 and 38: 5 Project implementation This chapt
Page 39: Concept generation Idea generation
Page 42 and 43: Figure 6.1 the system description.
Page 44 and 45: machine operator. Because of this,
Page 46 and 47: 6.2.2 Analysis of wheel loader task
Page 48 and 49: 6.2.3 Observation study The purpose
Page 50 and 51: Working postures of L90F The operat
Page 52 and 53: Discussion observation study The fi
Page 54 and 55: Figure 6.11 Jack simulation - Good
Page 56 and 57: Result anthropometric analysis The
Page 58 and 59: 6.4 Cognitive ergonomics in wheel l
Page 60 and 61: Discussion operators’ perception
Page 62 and 63: Result of operators’ mental model
Page 64 and 65: Discussion on operators mental mode
Page 67 and 68: 7 Problem definition This is the sy
Page 69 and 70: Table 7.1 Stated needs for handle A
Page 71 and 72: 7.3 Design Heuristics Depending on
Page 73 and 74: 8 Concept generation 1 The first co
Page 76 and 77: 8.2 Concepts The ideas from the ide
Page 78 and 79: 8.3 Concept selection 8.3.1 Concept
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9 Concept generation 2 The second c
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Sketches wrist and arm support and
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Figure 9.5 Classic joystick Figure
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10 Concept generation 3 When the ba
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Table 10.3 Elaboration of physical
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Finished functional prototype When
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easier to control the functions sim
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Housing The housing is as have been
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11 Concept evaluation This chapter
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Subjective analysis The participant
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Figure 11.4 Participant E This is a
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11.2.3 Rapid Upper Limb Assessment
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General comments from the evaluatio
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11.3 Conclusion of the evaluation T
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12 Final concept With the input fro
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Table 12.3 Elaboration of physical
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Housing To meet the technical limit
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Finished prototype The prototype re
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Figure 12.5 Angle of handle First p
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Control panel One of the reasons th
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12.5 Final remarks on the concept I
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13 Discussion Different aspects of
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method without reflections on the p
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The choice of consider the 5 th to
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14 Conclusion Discussions about the
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References Literature Adolfsson, Ni
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Figures Figure 1.1, figure 1.2, fig
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Appendix I - HTA HTA of excavating
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HTA of loading logs onto a truck: b
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VI !"#$%&'(()&*#+,-'./'*%,)(0,0&$-'
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VIII Present and Future Yes, but no
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Appendix V - Protocol !"#$#%#&&'()*
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Appendix VI - Questions 14.1.1 Over
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14.1.3 Placement In the fourth and
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14.1.4 Function In the questionnair
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Appendix VII - Result questionnaire
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