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Technical Note

University of Social Welfare and Reha-bilitation Sciences, Tehran, Iran

Correspondence to Reza Osqueizadeh, MSc, Department of Ergonomics, University of Social Welfare and Rehabilitation Sciences, Tehran 19857-13834, IranTel/Fax: +98-21-2218-0119E-mail: re.osqueizadeh @uswr.ac.irReceived: Jan 23, 2016Accepted: Jun 1, 2016

Cite this article as: Raeisi S, Osqueizadeh R, Maghsoudipour M, Jafarpisheh AS. Ergonomic redesign of an industrial control panel. Int J Occup Environ Med 2016;7:186-192. doi: 10.15171/ijoem.2016.756

Ergonomic Redesign of an Industrial Control PanelS Raeisi, R Osqueizadeh, M Maghsoudipour, AS Jafarpisheh

Abstract

Operator's role in industrial control centers takes place in time, which is one of the most important determinants of whether an expected action is going to be successful or not. In certain situations, due to the complex nature of the work, the existing interfaces and already prepared procedures do not meet the dynamic requirements of operator's cognitive demands, making the control tasks unnecessarily difficult. This study was conducted to identify ergo-nomic issues with a specific industrial control panel, and redesign its layout and elements to enhance its usability. Task and link analysis methodologies were implemented. All essential functions and supporting operations were identified at the required trivial levels. Next, the weight of any possible link between the elements of the panel was computed as a composite index of frequency and importance. Finally, all components were rearranged within a new layout, and a computerized mockup was generated. A total of 8 primary tasks was identified, including 4 system failure handling tasks, switching between manual and automated modes, and 3 types of routine vigilance and control tasks. These tasks were broken down into 28 functions and 145 supporting operations, accordingly. Higher link values were observed be-tween hand rest position and 2 elements. Also, 6 other components showed robust linkages. In conclusion, computer modeling can reduce the likelihood of accidents and near misses in industrial control rooms by considering the operators' misperception or mental burden and correcting poor design of the panels and inappropriate task allocation.

Keywords: Industry; Human engineering; Computer-aided design; Human factors and ergonomics; Man-machine systems

Introduction

Today's advancement of technology and access to enhanced job interfac-es, reduce working hours in hazard-

ous industrial environments on one hand, and signify the human role in directing and managing such complex systems, on the other hand. Reports and documents sug-gest that inappropriate allocation of cer-tain tasks to the human side might result in occupational near misses, accidents, or even disasters.1

Control rooms can be considered com-plex socio-technical systems, representing significant levels of human-machine inter-

actions.2 Operator's role in control centers takes place in time, which is one of the most important determinants of whether an expected action is going to be successful or not. The required tasks in such contexts are defined as either receiving the infor-mation through various types of displays or monitoring and adjusting the opera-tion process flow by means of designated controls.3 In certain situations, due to the complex nature of the work, the existing interfaces and already prepared proce-dures do not meet the dynamic require-ments of operator's cognition, making the control tasks unnecessarily difficult.4

Developing efficient and consistent

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human-machine systems is one of the fo-cal points in ergonomics.5,6 Being applied to many different areas, such as industry, health care, traffic, etc,7,8 ergonomics aims to guarantee the participation of a multi-disciplinary team in all phases of the de-sign process, so that task demands can be compatible with human capabilities, and unforeseen errors and subsequent inci-dents are moderated.9 Computer-based technology has been employed in ergo-nomic assessment and design of various industrial control-display interfaces.10,11 A typical design project of an industrial control room could be approached via two different methodologies: First, in regard to workstations' physical features and envi-ronmental parameters of the actual room, and second, in control-display arrange-ments and layout of the panels.2

International standard ISO 11064 de-fines an ergonomic design process for con-trol centers and specifies analyses and ver-ifications to be considered in each design phase.12 This standard consists of seven parts that has been applied in various aca-demic and industrial projects.13 Part four (ISO 11064-4, 2004)14 of the standard con-tains a workstation design procedure and related physical requirements. Part five (ISO 11064-5, 2008)15 provides a checklist to verify implementation of design princi-ples, a process description for display and control specification and high level alarm recommendations. Focusing on the above-mentioned divisions of the standard, the current study was carried out to ergonomi-cally redesign a production line control panel in an integrated steel industry.

Materials and Methods

Study Design

A sequential exploratory study was con-ducted, through which hierarchical task analysis and link analysis methodologies

were implemented. Participants were initially briefed on the purpose of the re-search, its voluntary nature and their right to withdraw at any time with prior notice. Ethical approval for the study was granted by the Ethics Board of University of Social Welfare and Rehabilitation Sciences.

Sampling

Twenty control room operators took part in the study. They were distributed across five comparable control desks, all located inside the main body of the selected indus-trial unit. The participants were approxi-mately 60th percentile males with mean height of 180 (SD 6) cm, mean age of 40 (SD 7) years, and fit for the duty over the study period. With a mean of 20 (SD 9.1) years of working in control room environ-ments specifically, the participants had also a very high level of industry experi-ence. All participants had more than one year of job experience in the same control room under analysis. The majority of them had a background in either production (55%) or other instruments (40%). A much smaller percentage derived from other op-erational trades (5%). Sixty percent occu-pied permanent control room positions, whilst 40% working on rotational sched-ules.

Hierarchical Task Analysis (HTA)

Hierarchical task analysis (HTA) is a meth-od of defining goals and tasks for a particu-lar job (using factors such as time, plan, sequence, and status) and dividing each goal into sub-goals, each one with its plans, in order to produce the most effective method of achieving the final aim.16 Opera-tors' interactions with a specified control panel (Fig 1) were assessed through de-tailed task analyses. Firstly, all tasks to be evaluated were carefully defined within various scenarios. Then, 15–20-minute video recordings were obtained and time framed. Finally, all essential functions and

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ments. The existing control panel layout was gridded and all 97 elements (including press-buttons, switch-buttons, joy-sticks, and indicator lights) were allocated to matching cells (Table 1). Processed infor-mation from task analyses was systemati-cally organized into a link table. Two types of operator hand movement (transitions) were considered—back-and-forth motions between the origin (the hand position in the rest posture, at the bottom-left corner of the control panel) and the target ele-ment, as well as motions form one element to another.

Layout Redesign

The weight of each transition was primar-ily considered a composite index of fre-quency and importance. For the frequen-cy, the total usage of each function over the specified 8-hour work shift was calculated as follows:

1

kk m

kk

fFf

=

=

∑

where, m is the total number of functions, and f

k is the relative frequency of usage for

function k. Considering the above mea-sures, the link value for each transition from element i to element j was calculated as follows:

E1

E2 E3

E4 E2 E5 E6 E7 E7

E8 E9 E2 E10 E11 E12 E13

E14 E15 E16 E17 E18 E19 E19 E20 E12 E13 E21 E22

E23 E24 E10 E17 E25 E26 E20 E27 E28 E22

E29 E30 E24 E16 E17 E25 E31 E31 E20 E32 E27 E33 E22

Table 1: Gridded layout of the actual panel

supporting operations were identified and separated at the required trivial levels.

Link Analysis

Link analysis is a quantitative and objec-tive method for examining the relation-ships between interface components, which can be used for optimizing their ar-rangements.17 It aims to improve the inter-face design by examining the task content, the characteristics of each individual item on the interface, and the relationships be-tween them. The cost of each operation in the task is quantified by a link value, which can be a function of importance, frequen-cy, difficulty, and other characteristics of the movements between two elements. The goal of link analysis is therefore to minimize the overall cost, by rearranging the layout while the operator uses the tar-get interface under certain task require-

Figure 1: The actual control panel studied

Industrial Control Panel Design

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, , ,1

m

i j k k i j kk

L I F C=

=∑where, I

k is a value reflecting the impor-

tance of function k (based on operators' opinions, values ‘1’ and ‘0’ were allocated to “important” and “unimportant” func-tions, respectively), and C

i,j,k is the number

of movements from any element i to ele-ment j in function k. Finally, based on the computed link values, all elements were rearranged within a new control panel lay-out.

Results

A total of eight primary tasks was identi-fied, including four system failure handling tasks, switching between manual and au-tomated modes, and three types of routine vigilance and control tasks. These tasks were broken down into 28 functions and 145 supporting operations, accordingly. Some of the operations comprised simple hand movement between the rest position and a specific element, while the majority involved combinational hand movements within the control panel, too.

Link values are summarized in Table 2 where meaningful linkages are highlighted in red. Each value represents the relative weight of the movement; the direction of the movement can be seen by the location of the cell that is filled. Higher link values were observed between hand rest position and elements E17 and E28. Likewise, E30-E16, E28-E13, and E17-E2 showed robust linkages.

In the improved layout (42×60 cm), un-usable components were omitted, and ele-ments with inter-related functions were combined and referred to as similar codes (Table 3). Moreover, indicator lights were integrated with the corresponding func-tional units. The modified arrangement also indicated all computed link values be- Table 2: The link table

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tween elements. Digital mockup of the control panel after the intervention is rep-resented in Figures 2 and 3. The IEC 60073 standard18 was considered in color coding the keys and switches.

Discussion

Control panel operation combines cogni-tive tasks, including visual search, recog-nition of items, and decision making, with bodily movements. Besides physical and physiological considerations, psychologi-cal characteristics of the operator influ-ence user experience and performance.19 Accidents and near misses in industrial control rooms reflect operators' misper-

ception or mental burden, indicating poor design of panels and inappropriate task al-location.

When the control interface is relatively large and physical movements are still re-quired for operating, the accessibility of the control elements with respect to the operator's position or initial posture may play a more important role than the prox-imity between them. In fact, such control interfaces are commonly used and being studied in many systems.2-4,7,10-13 In the current study, through an effortless step, a considerable number of unusable ele-ments were excluded, and the control pan-el shrunk in dimensions. Furthermore, in-dicator lights were simply combined with corresponding components. This, in turn, allowed the panel surface to be allocated more effectively and efficiently.

Link analysis considers functional prox-imity while optimizing physical distance and layout in order to achieve minimal mental and bodily effort in using control interfaces, frequently. Cheng, et al, pro-posed an improved link analysis approach to better understand the usability in de-signing control panel layout.8 Task and link analyses in this study provided a de-tailed local insight into the functions and operations involved in interacting with the

E1

E4 E18 E12 E12 E19 E19 E14 E9 E21 E11

E29 E2 E27 E27 E20 E20 E20 E15 E32 E33

E8 E2 E7 E7 E26 E10 E16 E24 E3 E22

E28 E2 E13 E13 E6 E10 E16 E24 E5 E22

E17 E17 E17 E31 E31 E30 E23 E25 E25 E22

Table 3: Gridded layout of the redesigned control panel

Figure 2: Digital mockup of the rede-signed control panel (isometric view)

Figure 3: 3D reconstruction of the redesigned control panel

TAKE-HOME MESSAGE

● Developing consistent human-machine systems is a focal point in ergonomics, being applied to many different areas such as industry, health care, traffic, etc.

● Control rooms can be considered complex socio-technical systems, representing significant levels of human-machine interactions.

● Besides physical and physiological considerations, psycho-logical characteristics of operators influence user experi-ence and performance in interacting with control panels.

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tween elements. Digital mockup of the control panel after the intervention is rep-resented in Figures 2 and 3. The IEC 60073 standard18 was considered in color coding the keys and switches.

Discussion

Control panel operation combines cogni-tive tasks, including visual search, recog-nition of items, and decision making, with bodily movements. Besides physical and physiological considerations, psychologi-cal characteristics of the operator influ-ence user experience and performance.19 Accidents and near misses in industrial control rooms reflect operators' misper-

E1

E4 E18 E12 E12 E19 E19 E14 E9 E21 E11

E29 E2 E27 E27 E20 E20 E20 E15 E32 E33

E8 E2 E7 E7 E26 E10 E16 E24 E3 E22

E28 E2 E13 E13 E6 E10 E16 E24 E5 E22

E17 E17 E17 E31 E31 E30 E23 E25 E25 E22

Table 3: Gridded layout of the redesigned control panel

Figure 2: Digital mockup of the rede-signed control panel (isometric view)

Figure 3: 3D reconstruction of the redesigned control panel

mentioned control panel. These approach-es thoroughly defined various operational combinations and optimal link values be-tween functional elements within them.

There are limitations in this study. Firstly, although the effectiveness of the intervention was proved theoretically, the definite outcome needs to be practically evaluated through detailed methodologi-cal approaches on a functional prototype. Secondly, the gathered data is rather con-text specific, and the redesigned control panel would not necessarily fit preferences and requirements in wide-ranging indus-trial settings.

Acknowledgements

The authors would like to thank all the experts and participants involved in this study, and appreciate the contribution of Kouhpaye Steel Company.

Conflicts of Interest: None declared.

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