An Error Model maintains differences between desired state represented by Objective models and actual state represented by navigation models. Error Models representing these differences in a form allowing computation of Action Models, in turn to direct flight. The main functional role of comparator components is data categorization and reduction. There are numerous ways in which actual and desired state may differ. These differences must be reduced to an Error Model containing small number of attributes that are meaningful to flight director components.
Most existing algorithms for computing these quantities each specialize on only one error dimension (e.g., speed). Thus the Error model and guidance comparator system cannot be designed as a single monolithic entity. Comparators must be constructed as a small collection of problem-solving specialists, each reducing actual versus desired state differences to one, or perhaps a few Error Model attributes.
Maintain only those attributes useful in computing Action Model components. In existing ACS systems, these are typically represented by values representing deviations from desired state on the three dimensions of vertical (altitude) error, lateral (heading) error, and longitudinal (speed) error.
Especially when Action Models are themselves specialized along these dimensions, the error model may take the form of a bundle of tiny independent models, each maintaining representations along only one of these dimensions. Update error models using Guidance Comparator components.