The inhuman working conditions of the early industrialization and the confidence in the mechanical view of the world of the 19th century in the possibility of planning and creating „good“ conditions provoked the founding of a separate science discipline. Already in 1857, Mr Jastrzebowski from Poland proposed in the journal „Nature and Industry“ to „…take care of the scientific approach regarding the problems that are imposed by „work“ and to create a separate science in order to obtain from this science the best with the least efforts with the highest satisfaction for the own and public welfare and by acting fair with regard to the own conscience and others“. He called this new scientifc branch „Human Engineering“ or „Ergonomics“ respectively. This name, however, was forgotten later.

Starting in the middle of the last century, many activities happened in the various countries that dealt with a scientific view of human work. The predominant scientific view of the world considered it feasible to transfer the rules of traditional physics to all phenomenons in nature and therefore also to human life (also refer to different works of Releaux and Fechner’s psychophysics). In the different European countries as well as in the USA, a science was established, which in the German-speaking area is called „Human Engineering“ (in the Anglo-American language also referred to as „human factors“, or also called „ergonomics“ in the European countries).

In Germany, the „Kaiser-Wilhelm-Institut für Arbeitsphysiologie“ was founded in 1912 in Berlin headed by Atzler and in 1926 the „Institut für forstliche Arbeitswissenschaft“ (Institute of Human Engineering in Forests) headed by Hilf. The original goal of the „Reichsausschuß für Arbeitszeitermittlung“ (committee for investigations on working times; REFA, as of 1936 „Reichsausschuß für Arbeitsstudien“; as of 1948 „Verband für ‚Arbeitsstudien REFA e.V.“) was to adapt Taylor’s scientific management (studies of time and movement, differential payment system) to German conditions and implement those in Germany.

In 1949, Murrell in England „re-invented“ the coined word „Ergonomics“ that had been compounded from ergon = Work and nomos = rule, legitimacy. In the following, various scientific organizations with the same denomination were founded in the European as well as outer-European countries (in Germany in 1953: „Gesellschaft für Arbeitswissenschaft, GfA). In 1959, they were grouped under the roof of the „International Ergonomic Association (IEA)“. The „Kaiser-Wilhelm-Institut für Arbeitsphysiologie“ later moved to Dortmund and after the 2nd World War was called „Max-Plank-Institut für Arbeitsphysiologie“. It was a main source for the human engeneering institutes that were founded at many technical universities in the 1960s. In 1962, the technical university Munich founded the Institut für Ergonomie (chaired by Prof. Dr. H Schmidtke) together with the Institut für Arbeitsphysiologie. Both Institutes were merged in 1990 and the re-named „Lehrstuhl für Ergonomie“ was then re-located to the „Institut für Produktionstechnik“ in the „Fakultät für Maschinenwesen“ of the Technische Universität München (TUM). In 1993, Prof. Dr. H. Bubb assumed the institute.

There are different viewpoints regarding the subject of this special field. In the introduction to his major work, W.E. Woodson wrote in 1981: „Human Factors Engineering is the practice of designing products so that the user can perform required use, operation, service, and suppotive tasks with a minimum of stress and a maximum of efficiency”. He also mentions the term „Ergonomics“, which according to his viewpoint is generally used as a synonym of „Human Factor Engineering“. The only tangible difference is the fact that „Human Factor Engineering“ is more common in the USA than in other countries. In 1981, M. Helander, who had been the President of the IEA for a long period, wrote: „Human factors engineering aims at modifying work procedures and machinery by taking into account the phsical and psychological capabilities and limitations of human beings”. He did mention different denominations for this discipline, such as „Engineering Psychology“, „Technical Psychology“ and „Ergonomics“ (the latter mainly used in Europe).

In 1987, in a Study for the „Gesellschaft für Arbeitswissenschaft“ (GfA), Luczak and Volpert et al. (1987) stated regarding the common practice in the German-speaking area that the „Human Engineering“ does comprise all disciplines that deal with the working human being, ranging from medicine, psychology, sociology, technology to law. Human Engineering was therefore defined as the systematics of analysis, order, and design of technical, organizational, and social conditions of work processes aiming at offering human beings productive and efficient work processes with harmless, manageable and un-disturbed working conditions as well as standards regarding content of work, work analysis, working environment, and remuneration and cooperation so that they felt motivated to expand their scope of activity, acquire competence and to develop and preserve their personality in cooperation with others.

Fig.1: Ergonomics and their disciplines

„Ergonomics“ is a multi-disciplinary science which uses basic knowledge from Human Science, Engineering Science, and Economic and Social Science. It does comprise occupational medcine, industrial psychology, industrial pedagogics, working-technique and industrial law as well as industrial sociology. All of these sciences, from their different points of views, deal with human work and therefore represent an aspect of this science. With regard to feasibility, this basic knowledge is summarized in so-called praxeologies. The one which is more oriented towards sociology, is called „macro ergonomics“. Its goal is to provide rules for the technical design of work places and work tools (see also fig. 1). For both, however, research focuses on the individual and its experiencing the workplace.

Regarding the term „work“ there are two different point of views: the original one, i.e. subject-related work as „effort“, and another one which sees work as object-related in the sense of production of goods and services (Luzcak, 1998). The latter one could also be regarded as a generation of information by individual performance (Bubb, 1987), which corresponds to the economic-scientific terminology of added value. Therefore, Ergonomics strives for reducing the subject-oriented workload and at the same time improving the object-related performance whilst carrying out the work. The individual performance of a human being carrying out his work is often influenced by external performance shaping factors, i.e. the factual performance prerequisites, as well as internal performance shaping factors, i.e. the respective human performance prerequisites (see fig 2). Management’s mission is to provide the external conditions in order to allow for an optimum of human performance efforts.

Fig. 2: Performance shaping factors

The main goal of Micro Ergonomics (in the German language usually referred to as Ergonomics) is to improve the performance of the whole work system as well as to reduce the stress imposed on the working human being by means of analyzing the task, the working environment and the man-machine-interaction (Schmidtke, 1993). The stress-strain-concept is the traditional approach to assess work systems. The basic concept is that each workplace is characterized by external factors, which are the same for all individuals working there (stress), whereas the individual reacts differently to those depending on the individual characteristics and abilities (strain). If one looks into detail, the stress can be distinguished between stress-parameters (that can generally be quantified in numbers), stress-factors (can generally only be described) and stress-exposure-time. To get a picture of the factors influencing work, the structure of the man-machine-system has to be examined by looking at the human work in relation to the therein contained information and the respective flow of information (also see fig 3). This comprises the task setting or the task and its translation into action respectively, the task fulfillment or the result respectively. The feedback arrow closes the control-loop created by the man-machine-system (MMS) and shows that the operator generally is able to compare task and result. All inflows to this process (as far as they are process- or system-inherent) are called environmental impacts.

Fig. 3: Structural system of human work

The stress-strain-concept described above can be applied on the stress caused by task setting as well as environmental stress. For the analysis of the task setting, one distinguishes between:

• tasks with predominantly physical load (so-called „physical work“); one differentiates here between static and dynamic physical work. For both, the stress can be quantified by the giving physical work requirements
• tasks with predominantly mental load (so-called „intellectual work“); an overall concept to define this stress in numbers does not exist; intellectual work is therefore generally seen as stress-factor
• tasks with mixed requirements (so-called „mixed work“)

For the analysis of environmental impacts (so-called „environmental ergonomics”), one distinguishes between:

• physical environmental impacts, which can be measured as well as their impacts on human beings which can be assessed quantitatively. These are mainly light, noise, mechanical vibrations, climate, poisoning gas and smoke, radiation, dust, dirt, and moisture.
• social environmental impacts which cannot be measured physically and therefore have to be analysed differently (taken care of by the so-called work sociology, partly by the industrial psychology; also see paragraph 4.2).

Another field of Macro Ergonomics is the analysis of the aspects within the man-machine-system (MMS). This analysis can be done, on the one hand, by taking into account the geometrical situation of the workplace and –tools (so-called anthropometrical workplace design) or, on the other hand, by considering the information flow in the Man-Machine-System (so-called „Systems Ergonomics“, see below).

The anthropometrical workplace design concentrates on the layout of the vision area, the grasping area and the motion area of the feet, on the layout of body supports (e.g. seats) as well as on the design of displays and controls. Besides the knowledge of the respective sensory perception barriers and conditions (e.g. resolution capacity of the eye, moving accuracy of the extremities), which are important for displays and controls, the design of the area that one can touch and reach with his foot as well as body supports, mainly the various height of human beings, play a major role. By percentiling the different body measures one attempts to deal with this problem systematically. Moreover, to simplify the often complex geometrical design problems, computer-generated human models (3D-models) were developed which allowed for the possibility of designing workplaces by CAD.

Systems Analysis allows to examine the basic structure of human beings within a complex MMS. Its goal is to obtain requirements for the layout of the man-machine-interaction within the framework of the specification of the MMS or ideas for possible improvements. As systems ergonomics strives for an optimizing this interaction, it contributes at the same time to reduce the number of mistakes made by human beings at work (so-called active security) and to increase the reliability of the overall performance of the MMS. A main procedure of systems ergonomics is to define the systems‘ elements and their interaction (Bubb and Schmidtke, 1993). Two basic principles should be highlighted:

• Information is always transmitted on very specific channels from the exit of one element to the entry of the other
• Elements are defined by their characteristic to alter information in a specific manner determined by the element

The fundamental characteristic of the systems analysis, and therefore of systems ergonomics, is to disregard the physical nature of the elements and their interaction and merely to examine the formal structure of this interaction and they means of the elements‘ information transmission. In systems ergonomics, the system components „human being“ and „machine“ are the main subjects of research. As the viewpoint is, as mentioned above, independent from the physical nature of the respective element, the results of systems ergonomics can be transferred to different MMS.

Deterministic View
Describing the characteristics of elements within a system by means of functions and on the basis of a given input, this leads to a prognosis of a clear starting- and end-function. This way of thinking corresponds to the usual cause-consequence way of thinking. While in most of the times it is difficult, whereas not impossible, to describe the reaction of human beings in mathematical functions (in special cases this is done in the form of so-called cognitive methods, e.g. „paper pilot“), the cause-consequence principle is nevertheless underlying here as well. So-called cognitive models of human beings are being developed to allow to predict human reaction in a situation imposed by the MMS. At least in this way, the specific impact of actions (e.g. changes in displays or controls respectively) on the performance of work can be predicted. Moreover, this viewpoint allows to get to know about a system structure which might be more favorable to human characteristics and abilities. This deterministic side of systems economy therefore allows to make constructive proposals to improve the man-machine-interaction. A specialized field of systems ergonomics is the so-called software ergonomics, which deals with adapting computer programs to the characteristics of human beings. The major part of the software-ergonomic recommendations was developed for the layout of the so-called user-interface (which means essentially the information and tools on the screen). In addition, the software-ergonomic research and recommendations deal with the design of processes that are given by the program structure and tries to adapt them to the needs and possibilities of human beings.

Probabilistic view
The system-ergonomic view of the MMS can be linked to a reliability analysis and -assessment in order to better measure the effectiveness of measurements for optimization of the MMS, which had been put into place due to system-ergonomic analysis. The prerequisite of the reliability analysis as well as the systems analysis is a partition of the MMS into elements and their interaction. By assessing the reliability and failure probability of the elements, linking them to the rules of the Boolean Algebra and considering the system structure and calculating the expected total failure probability, it is possible to not only locate elements that strongly affect the total failure probability but also by re-allocating the system structure, which of course has to be done in the way that the overall function is maintained, to improve the failure probability. Amongst others, this procedure, incorporating human beings, can provoke changes in organization and organizational rules. The probabilistic viewpoint (so-called probabilistic method) that is mentioned here only in rough outlines cannot be understood as an alternative to the traditional cause-consequence approach. The latter one is the only way to assess and methodologically design the functioning of a system. In contrast, the probabilistic approach has a more assessing function. This assessment might also be vital in the designing phase, as thereby more-important design functions are distinguished from less-important ones. This influences especially the assessment of how economic an ergonomic measurement might be.

Very often, Ergonomics is differentiated dependent upon their fields of application. Thereby, mainly product design and production ergonomics are distinguished.

The main goal in product desgin ergonomics is to offer a product adapted to the customer to the best extent possible while the customer base is more-or-less unknown. For the development of such products, for the design, it is also important to know about the variability of human beings regarding anthropometrical as well as cognitive features. A current area of research of product design ergonomics is the scientific recording of everything related to the feeling and experiencing of comfort.

The goal of production ergonomics, however, is to provide working environments in manufacturing and service companies that are adapted to human beings. The objective hereby is to reduce the stress of the worker and optimize his performance ratio at the same time. This means, that in the majority of the cases, this is about reasonability and tolerability. Contrary to the objective of production ergonomics, the targeted human being (worker) is well-known, which enables to better address his needs. As for both product design as well as production ergonomics the above mentioned methods of ergonomics are used and as often the „product“ of one producer is the „tool“ of the other, it is virtually not possible to draw an exact between both.

Main fields of application, where today systematical ergonomic development is used, are aviation (mainly cockpit design in airplanes; anthropometrical design of interior; so-called packaging; design of new means of communication to improve security, comfort, and individual mobility), maintenance (chemical plants, nuclear power stations; fields where the aspects of human reliability play a major role), and office (design of computer screens, office chairs, layout of everything that surrounds the computer work place, software ergonomics). Another specialized field of ergonomics is the research on threshold values for work in extreme conditions as narrowness, cold, heat, overpressure, extreme acceleration, weightlessness, catastrophic situations, etc.

According to a definition of REFA (1987), Macro Ergonomics (labor organization in particular) deals with the systematic structure and organization of a workflow regarding task-, content- and time factors. It can be differentiated into an organizational structure and work process organization. The target of Macro Ergonomics is not the single workplace (as in Micro Ergonomics) but the interaction between several workplaces (Zülch, 1992). Its goal is to check the ergonomic requirements on this level. In this context, also the term macro work systems is employed. The single areas of the macro organization can be derived if the single work system (fig. 3) is transferred into the larger work task context of a group (see fig. 4).

Fig. 4: Reference framework of the work organization (according to Zülch, 1992)

• An analysis of the workflow provides information on the time needed for the tasks which have to be fulfilled within the organizational unit and on their inter-dependencies. This allows to specify the capacity requirement of human beings and means of production as well as their time utilization. Especially communication ways and possible loss of information are to be determined in order to optimize the interaction between workers and working funds. The development in innovative telecommunication- and computer technologies do present new challenges to the work organization.
• Similar to Micro Ergonomics, but more comprehensive, the environment conditions are defined as those impacts that do not directly affect work- and communication processes but do moderate them indirectly. It is important to distinguish between impacts that cannot be varied by the work organization and impacts which can be optimized by appropriate design of the workflow and organizational structure of the cooperation.
• On the output side of the work process, an improvement in performance can be obtained by organizational measures, whereby on the one hand person-related verification methods of the quality of work objects and –results respectively are developed and, on the other hand, the worker is influenced by motivating actions.

Many of the above described issues simply cannot be proved by experiments as, due to the legitimate economic prosperity demands comparative studies are generally not allowed. Therefore, often partly very detailed simulation methods are employed, which by means of cumulative key numbers describe the personnel utilization, personnel qualification, waiting times, overlapping by simultaneously-incoming orders, etc., do provide an estimation on organizational changes and new structures. It should be seen as a major task to develop valuation systems for macro ergonomics as moreover, contrary to micro ergonomics, those do not yet exist, whereby both aspects of feasibility as well as aspects of personality development for employees should be taken into account (Zülch, 1992). Management measures, such as job enrichment (adding tasks to avoid monotony), job enlargement (add more responsibilities to the task), job rotation (switch tasks following a pre-determined structure or based on direct communication with the collaborators), whereby the prerequisite of all is team work, is designed to develop the personnel’s personality besides increasing flexibility, which is desired from an economic point of view.

It is only possible to observe and judge the impact of macro ergonomic measures regarding their impact with the background of the respective company organization and the social environment. Therefore, the observation and assessment of the respective interactions is another macro ergonomic field of activity. Fig. 5 shows a summary of interactions which have been developed on the basis of IEA’s topic selection. In the sense of the above mentioned terminology, it shows at least the environment impacts which cannot be manipulated directly.

Fig. 5: The business and social aspects influencing the organization of work

Of major interest from a macro ergonomic point of view, i.e. taking into account the individual requirements and needs of the employee, is the study of the effects which derive from modern business organizational developments as „the learning plant“ or „the fractal plant“. Its main feature is the dynamic change, whereby the employee must be able to foresee and understand the logic in order to accept it. In addition, relevant general social developments are of course subject to macro economic studies. This means that the shift of employed work from work in the production to the service field and the flexibility expected from the employee regarding contract as well as his willingness of life-time learning (also see Rifkin, 1997, and Giarini and Liedtke, 1998) are of major importance on the issue of future organization of work. Nevertheless, the overall orientation of all macro and micro ergonomic efforts should not be forgotten: „the human being does not live to work but works to live“.

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