Nonlinear H/sub /spl infin// control: practicality of implementing the cheap sensor case

We previously (J.W. Helton and M.R. James, 1999) introduced a recipe for nonlinear H/sub /spl infin// controllers which takes advantage of extra perfect measurements and stated a theorem to the effect that this controller yielded the best possible "H/sub /spl infin//" performance. Pure state feedback is an extreme situation and we treated cases where all but a few states are measured perfectly. In this article we analyze the computational complexity of the online part of the H/sub /spl infin// controller described previously. This has important practical implications. Our conclusion is that under reasonable circumstances when the number of unknown states is less than or equal to 2 and the total number of states is less than or equal to 12 the online portion of the recipe with a 1 GHz PC produces about 100 controller updates per second.