2.6. Simulation

In evaluation research, the variants of a system or a product are often most practicably realised in or through a simulator (Meister & Rabideau 1965, Sanders & McCormick 1993). Simulation consists of a physical representation of equipment, events and task performances (Meister 1995). For a true test of the “goodness“ of a product, the test should be conducted under conditions representative of those under which the thing being tested will ultimately be used. The evaluation of human factors should be done in actual operational situations or in circumstances that approximate the operational conditions (Meister & Rabideau 1965, Sanders & McCormick 1993).

The real-world simulations in which ergonomic research is conducted combine the benefits of both laboratory and field research (Sanders & McCormick 1993). Simulation in the laboratory usually means that 3-dimensional physical models are used. Simulation models of this kind represent part of a real system. Physical simulations represent, i.e. look like or act like, a system, a procedure or an environment. Physical simulations can range from very simple to extremely complex configurations. The laboratory setting has the principal advantage of allowing experimental control; extraneous variables can be controlled, the experiment can be replicated almost at will, and data collection can be made with greater precision. For this advantage, however, the research may have to sacrifice some realism and generalisability.

A user-centred design approach calls for envisioning concrete representations, i.e. user-centred representations, which are models and prototypes of the design ideas, to be used as tools of communication and evaluation (Preece et al. 1994). Products can be successfully tested at different stages of development, and the form in which a product is presented depends upon the development stage, the product type and the aspect that requires investigation (McClelland 1995). In the early stages, users can be involved in the evaluation of scenarios, simple paper mock-ups or partial prototypes (ISO 13407 1999). 2D and 3D sketches can support the exploration of possibilities and the generation of ideas in the search for a product concept. Visual reasoning about physical aspects utilises the loop of seeing things, imagining things, and creating things by drawing and building sketches. With concrete models, the ideas can be easily compared to each other, and new starting points can be found (Säde 1996). As the design solutions become more elaborate, the evaluations involving users are based on progressively more complete and concrete versions of the system (ISO 13407 1999). McClelland (1995) points out that the forms commonly tested include: (1) paper-based descriptions of product concepts, (2) partial prototypes or simulations, (3) full prototypes and (4) complete products.

The whole population is difficult to employ in a design process. A designer can use a human model, which is a representation or imitation of the ergonomically relevant features of population. The most important human models used in anthropometric ergonomics are: (1) tables and layout drawings (of workspaces), (2) two-dimensional manikins, (3) computer models of human beings and (4) test subjects. A product model plus a human model provide a behavioural model of the ergonomic functioning of the product. One example of computer software that enables one to design the machinery and the environment to be suitable to the user is ergoSHAPE program developed in Finland (Launis & Lehtelä 1990). The first three types of human models are especially well able to tell us what humans can and cannot physically do, but not (or to a lesser extent) what humans actually do in real conditions of use, which user errors they make, etc. Cognition usually plays at least an equally important role as anthropometric parameters. The effect of cognition (including knowledge about and experience with a product) can only be simulated well by experimenting with the test subjects and an iconic model (dummy, scale model, mock-up) of the product (Roozenburg & Eekels 1995). For example, a full-scale mock-up can be used to evaluate the functional aspects of a workstation appropriately by involving different people to test the workstation by simulating tasks (Helander 1995). Nowadays, solutions can be also tested by applying virtual reality.