Introduction
In the mid-l970s, American automotive
manufacturers introduced microprocessor- based engine control systems to meet the conflicting demands of high fuel economy and low emissions. Present-day engine con- trol systems contain many inputs (e.g., pres-
sures, temperatures, rotational speeds, ex-
haust gas characteristics) and outputs (e.g., spark timing, exhaust gas recirculation, fuel- injector pulse widths). The unique aspect of the automotive control problem is the re- quirement to develop systems that are rela- tively low in cost, will be applied to several hundred thousand systems in the field, must
work on relatively low cost automobiles with
the inherent manufacturing variability, will
not have scheduled maintenance, and will be
used by a spectrum of human operators. (Note that the aircraftispacecraft control
problem, for which most sophisticated con-
trol techniques have been developed, has
nearly an opposite set of conditions.)
The software structure of the controllers
that have been developed to date is much like
that in other areas (i.e., aircraft controllers
and process controllers) in that there exists
an "outer-loop'' operational-mode structure