2 research outputs found
Design of Controllers and Observer-Based Controllers for Time-Delay Singularly Perturbed Systems via Composite Control
This paper presents a novel and general approach, which is based on the composite control method, to synthesize the controller and observer-based state feedback to stabilize the singularly perturbed time-delay systems. First, the equivalent models of the original systems and the subsystems reduced via singular perturbation techniques are derived. Through these equivalent models, approximation of the stabilization and observer design for the original systems can be achieved through separate analyses for the slow and fast subsystems via a transformation of block diagonalization
Full-State and Output Feedback Control of Uncertain Nonlinear Nonstandard Multiple-Time-Scale Systems
Nonlinear systems with dynamics evolving in distinct slow and fast time-scales are common
in science and engineering. Geometric singular perturbation theory is a powerful tool for controller
design for such systems over multiple-time-scales. Aerospace vehicles such as aircraft and spacecraft
are examples of nonstandard multiple-time-scale systems, for which the control synthesis is more
challenging than for standard systems. Most control methods for nonstandard systems assume
deterministic model and full-state feedback. This dissertation extends the current capabilities of
multiple-time-scale control for nonstandard systems by developing novel theories of control design
for uncertain systems and using output feedback. Both of slow state tracking and simultaneous
slow and fast state tracking for nonstandard systems are considered as control objectives. Using
the time-scales of the slow states, slow actuators, fast states and fast actuators, the control laws
developed over four-time-scales can account for multiplicative and additive uncertainties. The
controller uses estimates of the unknown parameters and the unmeasured states, and ensures
Lyapunov-stability of the lower-order reduced subsystems. The estimates are updated by an online
parameter estimator and a nonlinear state observer respectively. They are designed using the
composite Lyapunov analysis. This analysis also proves the boundedness of errors and establishes
bounds of time-scale separation to accomplish the same. The theory is applied to perform attitude
tracking for a generic spacecraft with uncertain inertias, and large-amplitude combined longitudinal
and lateral/directional maneuvers of a nonlinear six-degree-of-freedom aircraft with uncertain
inertias, control derivatives and engine time-constant