Report of the Second Piloted Aircraft Flight Control System - Acgsc.org

SYNTHESIS OF FLIGHT CONTROL SYSTEMS
by DR. JOHN G. TRUXAL
of
Purdue University
Lafayetfe, Indiana
During the past year Purdue University has been privileged to have
a contract from the Office of liaval Research to investigate design techniques
for power boost systems for aircraft control. We at Purdue feel
that the university research groups can not, and should not, be in direct
or indirect competition with industrial research. Rather we feel that the
primary job of university research should be the development of basic
synthesis techniques.
In line with these aims, our prima~g interest has been in the investigation
of the basic general problem of the stabilization and design of power
boost qystems. He have attempted to clarify and delineate the problems
involved in this design and to develop and determine those design technique8
which will be generally applicable in this problem. We have not worried
particularly about specialized methods of stabilization which might be
applicable to one aircraft, not to another. Rather, our main concern has
been with methods which we hope will be generally: applicable; in the absence
of any one specific problem, we leave the more specialized techniques to the
industrial research groups.
What is the fundamental problem? As we see it, the problem arises from
a basic conflict between speed of response and stability. On the one nand,
we have the speed of response of our control system; on the other, the
stability of the overall aircraft. The relative location of these two
conflicting requirements depends on a number of factors--e.g., the aircraft
speed. As long as we are dealing with low-speed aircraft, there is essentially
no problem. At low-speeds, a relatively sluggish aircraft response is permissible.
In addition, the aerodynanlical characteristics of the plane itself
may be relatively stable. however, as the required aircraft speed increases,
two things start to happen: the speed of response must be increased; the
relative stability of the aircraft decreases. Inevitably, as we demand better
and better perforlance frdm our aircraft, the problems involved in realizing
a system which is sufficiently stable and at the same time responds with
adequate spee4 becomes more difficult . 'tie feel that we are now at the point
where design has become difficult, particularu in those cases in which we
deal with the aircraft as a gun platform. Essentially, the situation here
is no different t t u that in ~nany fields of engineering. TPis is a universal
phenoniena--this development of tauter and tauter specifications, as the years
go by; this demand, as these specifications become more taut, for a more
complete understanding of the basic system--and in particukr a fuller understanding
of what factors influence the system performance.
Chw first concern then has been with a deten~unation of those factors
which do determine the stability and the speed of response of the aircrafts