Fl. Lewis et al., DIGITAL TRACKER WITH OUTPUT-FEEDBACK - APPLICATION TO AIRCRAFT CONTROLS, International Journal of Systems Science, 25(12), 1994, pp. 2065-2077
Citations number
21
Categorie Soggetti
System Science","Computer Science Theory & Methods","Operatione Research & Management Science
A linear-quadratic output-feedback approach is given for designing dig
ital servocontrol systems of specified structure. The result is digita
l controllers that have a sensible structure based on classical contro
l theory, in contrast to standard LQR design using state feedback plus
an observer. The correct initial conditions for determining the LQ tr
acker output-feedback gains are not uniformly distributed as is tradit
ionally assumed, but are shown to be explicitly given in terms of the
step command magnitude. Both pole and zero placement are used to optim
ize the performance index. Arbitrary systems are treated, not only tho
se with integrators in the forward paths, by adding a term to the perf
ormance index that weights the steady-state error. The approach works
even if the system is non-minimum-phase. Necessary conditions are deri
ved that may be used in a gradient-based routine to determine the opti
mal digital control gains. The approach does not rely on redesign of a
continuous control system using techniques like the bilinear transfor
mation, but uses direct discrete-time design. An aircraft digital comm
and augmentation system is included as a sample design.