Failure of linear control in noisy coupled map lattices

We study a one-dimensional ring of diffusively coupled logistic maps in the vicinity of an unstable, spatially homogeneous fixed point. The failure of linear controllers due to additive noise is discussed with the aim of clarifying the failure mechanism. A criterion is suggested for estimating the noise level that can be tolerated by the given controller. The criterion implies the loss of control for surprisingly low noise levels in certain cases of interest, and accurately accounts for the results of numerical experiments over a broad range of parameter values. Previous results of Grigoriev et nl. [Phys. Rev. Lett. 79, 2795 (1997)] are reviewed and compared with our numerical and analytic results.