  Based on a series of two experimental campaigns testing advanced controllers
on a scaled wind turbine operating in a wind tunnel, this contribution
describes the overall experimental method, challenges faced, lessons learned,
and opportunities for future work. The two campaigns, run in Fall 2018 and Fall
2019, tested unconstrained and constrained optimal blade pitch controllers,
respectively, using preview disturbance measurements of the oncoming wind.
Specifically, the first study considered an extension to the linear-quadratic
regulator to include feedforward action, while the second deployed model
predictive control to incorporate actuator constraints into the optimal control
problem. The results of the campaigns have already been published in technical
conference and journal papers on control systems; however, detail on how the
controllers were implemented was not included in those works. We aim to fill
that gap with this contribution, which is targeted at the wind energy
community. We describe several aspects of the experimental setup, in particular
providing details of the software and hardware used for the controller; share
insight on several aspects of the procedure that were difficult and how we
overcame those challenges; and summarize the key differences between
simulation-based studies and physical testing. By doing so, we hope to share
what we learned during our experimental campaigns and provide a point of
reference for others looking to carry out experiments on scaled wind turbines
operating in wind tunnel facilities.
