NONLINEAR CONTROLLER COMPARISON ON A BENCHMARK ...

Chapter 5
Experimental Results
5.1 Testbed and Open Loop Response
The experimental results obtained from the actual exible beam system are
similar to those obtained in simulation { a veri cation of the functionality of the
mathematical model used. In the actual hardware experiments, however, the nonlin-
ear control strategies clearly outperform the linearized controls: it is a validation of
the true robustness of these nonlinear algorithms and their design methodologies.
The experiments conducted on the FBS use the same testing method that
was introduced in the simulation: an initial voltage pulse begins an oscillation, and
at time = 2 seconds the control is switched on to dampen the disturbance. As
shown in the plot of the open loop response, there is substantial unmodelled damping
present in the system, therefore the plots only show the response through time =
6 seconds. Due to some software incompatibilities and some di culty in tuning
(the backstepping designs either went unstable or made the system's motor grind),
the backstepping control was not implemented and tested on the hardware system,
but the ve remaining control laws were each tuned to provide the best possible
performance in hardware. As before, the results of each of the control strategies will
be compared to each of the others as well as to the open-loop response of the plant.
5.2 Linearized Optimal and Robust Controls
The linearized controls, which appeared to be among the best feedback choices
in simulation, show lack-luster results when implemented in hardware. The linearized
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