Abstract: The history of adaptive control systems dates
back to early 50-s, when the aeronautical community was struggling to advance
aircraft speeds to higher Mach numbers. In November of 1967, X-15 launched on
what was planned to be a routine research flight to evaluate a boost guidance
system, but it went into a spin and eventually broke up at 65,000 feet, killing
the pilot Michael Adams. It was later found that the onboard adaptive control
system was to be blamed for this incident. Exactly thirty years later, fueled
by advances in the theory of nonlinear control, Air Force successfully flight
tested the unmanned unstable tailless X-36 aircraft with an onboard adaptive
flight control system. This was a landmark achievement that dispelled some of
the misgivings that had arisen from the X-15 crash in 1967. Since then, numerous
flight tests of Joint Direct Attack Munitions (JDAM) weapon retrofitted with
adaptive element have met with great success and have proven the benefits of
the adaptation in the presence of component failures and aerodynamic
uncertainties. However, the major challenge related to stability/robustness
assessment of adaptive systems is still being resolved based on testing the
closed-loop system for all possible variations of uncertainties in Monte Carlo
simulations, the cost of which increases with the growing complexity of the
systems. This talk will give an overview of the limitations inherent to the
conventional adaptive controllers and will introduce the audience to the L1 adaptive control theory,
the architectures of which have guaranteed
robustness in the presence of fast adaptation. Various applications,
including flight tests of a subscale commercial jet, will be discussed during
the presentation to demonstrate the tools and the concepts. With its key feature of decoupling adaptation from
robustness L1 adaptive control theory has facilitated new
developments in the areas of event-driven adaptation and networked control
systems. A brief overview of initial results and potential directions will
conclude the presentation.
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