This proposal describes a project to explore a new area of adaptive control and
to address open problems of urgent relevance to theory as well as
applications: adaptive control of systems consisting of a linear part and a
nonsmooth nonlinear input-output characteristic being in either an actuator
or a sensor. Typical examples of such nonlinear characteristics are dead-zone,
backlash and hysteresis. An adaptive inverse approach is proposed to control
such systems to meet desired performance specifications, which exploits an
adaptive inverse for an unknown nonlinearity and a linear controller structure
nonadaptive/adaptive for a known/unknown linear part. Choices of nonlinear
models, design of adaptive inverse control algorithms, stability, convergence
and robustness analysis, and applications will be investigated. The results of
this research will provide new tools to handle unknown nonsmooth nonlinearities
which are common in practical control systems.
This proposal describes a university-industry collaborative research project to
explore a new area of adaptive control: adaptive control of sandwich
nonlinear systems , and to solve some long-standing and wide-range control
problems of urgent relevance to theory as well as applications. The proposed
research will focus on adaptive control of sandwich systems with linear and
nonsmooth nonlinear dynamics and on adaptive control of two-layer systems with
smooth and nonsmooth nonlinear dynamics. Typical nonsmooth nonlinear
characteristics are dead-zone, backlash, hysteresis, other
piecewise-linearities as well as frictions which are the main sources of
component imperfections in control systems. The proposed adaptive inverse
control approach employs an adaptive inverse to cancel the nonlinearity effects
in order to achieve system performance improvements. This approach points to
a new direction to design control systems using a new algorithm-based
technology, which, after a period of learning or adaptation, can recognize
component imperfections and compensate for their harmful effects. With such
adaptive controllers, the component specifications could be greatly relaxed,
their cost reduced, and their reliability increased. The results of this
research will advance the knowledge of adaptive control significantly, provide
new tools to effectively handle practical nonlinearities which have haunted
the constructors of control systems for many years, and have many applications
in defense and civil industries in which high-precision control systems are
vital components.
This proposal describes a research project to develop new adaptive failure
compensation techniques for dynamic systems with uncertain failures.
The proposed research is focused on the development of a novel
systematic theoretical
framework for adaptive failure compensation and specific solutions for
several synergic topics, to provide guidelines for designing control systems
with guaranteed stability and tracking performance in the presence of system
parameter, dynamics and failure uncertainties, with applications to
performance-critical control systems. New theories of
nonlinear and multivariable adaptive control, new approaches for
system modeling in the presence of system failures, and new methods of
adaptive failure compensation will be explored for new advances in
this open area of research.
The first topic is the development of novel system modeling and
adaptive control approaches for systems with failures.
For many applications, models of systems with failure and without
failures are essentially different (for example,
aircraft flight dynamics in an engine differential mode).
We will develop novel system models which
capture the key features of dynamic
systems in the presence of failures, based which effective
failure compensation schemes can be designed.
The second topic is the development of adaptive failure
compensation schemes for multivariable systems with space
structure vibration reduction control applications. The third topic is
adaptive compensation of failures in cooperating multiple manipulator
systems. New controller parametrization and adaptive laws are needed for
intelligent autonomous robot control systems which can adaptively compensate
for uncertain failures. The fourth topic is control of systems with MEM
devices as actuators which may fail during system operation. Effective
compensation of failures of MEM devices is a key component of successful
MEMS technology and this research is to develop such techniques illustrated
by control of morphing actuators and synthetic jet actuators applied to
aircraft flight control. The unified theme of these topics is failure
compensation by direct adaptation of controller parameters without explicit
fault detection and diagnosis, aimed at achieving fast response and
effective compensation of uncertain failures. The unique feature of
adaptive failure compensation is that it ensures both stability and
asymptotic tracking, without the knowledge of when, how much and how
many failures appearing in the system. The importance of this research is
its potential for significantly improving control system performance in
the presence of uncertain failures for performance-critical applications.
Intellectual merit: The proposed activities has high
intellectual merit. Adaptive failure compensation has open issues such as
failure induced parameter/structure uncertainties, system failure
compensability, controller adaptivity to uncertain failures, system
stabilizability under multiple failure patterns, and advanced applications,
which are both important and challenging in theory and practice as well.
Those issues contribute to the unique features of the control problems
investigated in the project, and their solutions will lead to creative
concepts and effective methods for fields of systems and control. This
research will develop novel solutions to such issues, which will advance the
state-of-the-art in adaptive control theory and emerging applications such as
MEM technology, safe aircraft and intelligent robot systems. Preliminary
study has shown encouraging results of this promising adaptive compensation
approach.
Broader impacts: This research will have major impact on technology as
it will develop novel system modeling and adaptive control techniques
for aircraft flight systems, intelligent robot systems, active
vibration control systems, and for control
of systems with MEM devices such as morphing actuators and synthetic jet
actuators, with uncertainty adaptation and
failure compensation capacities to improve system reliability,
maintainability and survivability. Impact on education will be strong as the
research activities and results will bring new concepts and theory of
adaptive control into student training and knowledge
dissemination. Impact on outreach will be broad as the proposed adaptive
failure compensation techniques have attracted academic and
industrial/government researchers such as NASA and Air Force.