Analysis Techniques For Man-Machine Systems Design

NATO UNCLASSIFIED- 125 AC/243(Panel-8)TR/7Volume 26.3 LINK ANALYSISWhat the technique doesLink analysis is a technique for evaluating and improving the layout of equipment and the operator-machine interfaceby minimizing the "costs" associated with transitions between different items of equipment, or different componentsof the interface. It is concerned with the relative positions. frequencies, and importance of use of the differentcomponents, and how their use can be arranged most effectively. It can be applied to the layout of a specific humanmachineinterface (Shackel, 1961), or to the layout of a crew compartment for several operators and items ofequipment (US DoD, 1987).A link is any connection between two elements of an interface or crew compartment, either visual, aural, or bymovement of a limb or person. An element is any item of the interface or crew compartment which is used during theoperations being analysed. Costs are associated with each link based factor such as frequency, importance. time,strength, sequence, and distance. Link analysis attempts to reduce associated costs by minimizing the length of thelinks associated with highest cost.Initially, a task analysis, or an activity analysis ofan actual system, is completed, identifying thelinks between operator and equipment. Conventionuses numbers for humans and letters for equipment.8 The links are charted as a to-from matrix, notingthe frequency and/or strength or importance of the -n- links.The links are superimposed on the proposed orexisting layouL If a new design is being developed.the higher cost links are drawn first, then the lowercost links are added. Sequence of the links is alsoused to determine layout. Convention uses circlesto identify humans, squares to identify equipment.The layout is refined by modifications which reducethe lengths of the higher cost links, and avoidcrossing links wherever possible.Link analysis can be used to reduce the likelihood of operator error by simplifying the sequences required to usecontrols and displays. The examples reported by Comell (1968) and Shackel (1961) are based on single sequences oflinks used in setting up and operating equipment.There have been several attempts to improve the analysis of the cost function data, particularly for complicatedproblems (see Laughery & Laughery, 1987). Freund & Sadosky (1967) applied linear programming to the solution ofthe cost problem. Siegel, Wolf & Pilitis, (1982) applied multi-dimensional scaling to the treatment of the link data.Wierwille (1981) reported the use of optimization procedures for the instrument layout problem. Hendy (1989)extended link analysis to include the angular relationship between links as well as link length, through the use of avariety of cost functions and the application of mathematical optimization techniques.NATO UNCLASSIFIED1 II;