Design of an ergonomic control lever for wheel loader attachments

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1.1.1 Technical background Hydraulics is the system that produces the force and movement of an attachment, e.g. a bucket. Basic functions are lift and tilt, and, in many cases, one or two additional functions are made available. The operator uses the control levers placed on the right side of the driver’s seat (figure 1.2), to control the hydraulics. The control unit currently in use includes two to four linear levers (figure 1.3). Previous research related to the control levers’ design has not included deeper ergonomic studies or methodology and the market demand other solutions than now available. The work environment is tough on the body and the operator performs repetitive work movements and at the same time is exposed to static working postures (Nilsson & Rose, 2003, p. 9). Statistic research and medical research have revealed relationships with occupational injuries and the work in off-road machines. Musculoskeletal disorders seem to arise from long working sessions, static and/or awkward working postures in combination with inappropriate control levers or placements of control levers, according to Adolfsson, Öberg and Torén (2002 p. 7). Figure.1.2 Cab interior (Volvo CE, 2011 a) Figure.1.3 Control levers (Volvo CE, 2011 a) 1.2 Purpose and Goal The master thesis’ purpose is to design an ergonomically optimized single lever concept that fulfills the market demands. The project therefore contains work that is research on this problem area, and development of a conceptual design to solve that. This means that the result is not intended to be a definite part of any company’s product plans. It is a prerogative of the product developer to decide whether this work may contribute to a concrete product development plan. Two to four main hydraulic functions are to be integrated into one single lever. Any additional function needed, must be designed for in the final overall solution. The work environment for a wheel loader operator will be investigated, and guidelines for improved physical- and cognitive ergonomics will be presented. The final solution is a physical prototype with highest functional capability as possible, as basis for further construction development. The final concept shall: 10 • Be as original as possible and not be a conscious replication of existing products. • Be designed for wheel loader environment. • Improve the physical ergonomic conditions for the machine operator. • Improve the learning curve for novice users. • Meet the market’s demands.
1.3 Question formulation The studies and analysis are aimed to answer to a set of questions in order to also improve the situation. These are defined and centered on the user to understand the user’s needs. The questions are: • Who is the user? • What is the task? • How is the user affected by the task? • What are the physical and cognitive ergonomic needs? • How can these ergonomically needs be fulfilled? 1.4 Delimitations As any project, this thesis work is delimited to be feasible and manageable. Also, the stakeholders of the project, CPAC and Volvo CE, have requirements on the thesis work to be coherent with their strategy objectives. The delimitations for the thesis work and project output are defined as: • The physical ergonomic load from the control lever/single lever will be related to the armrest and the transition between the armrest and the control lever unit. However, the armrest’s issues lay outside of this project’s scoop. Suggestions for design changes for the armrest might be given but will not be included in the final design. • The final concept will keep the current interface between the control lever unit and the armrest using the same metal bracket. • It is important that the final concept is technically feasible consisting of existing components, to shorten the implementation time if an implementation of the final concept would be in question. • The final concept should have the same functionality as the current control lever unit. • The interface to the electro-hydraulic system is not to be compromised although software changes are possible to some extent. • Volvo sells their wheel loaders on a global market, which makes the whole world population possible primary users. To narrow it down, interviews, observations and evaluations have only been performed with Swedish machine operators. 11
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: 1 Introduction The underlying reaso
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 and 30: 3.3 Standards and recommendations T
Page 31 and 32: 4 Methods This chapter consists of
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
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Discussion operators’ perception
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Result of operators’ mental model
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Discussion on operators mental mode
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7 Problem definition This is the sy
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Table 7.1 Stated needs for handle A
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7.3 Design Heuristics Depending on
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8 Concept generation 1 The first co
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8.2 Concepts The ideas from the ide
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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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