Multi-Channel Coherent Detection for Delay-Insensitive Model-Free Adaptive Control

A mixed-signal architecture for continuous-time multidimensional model-free optimization is presented. It is based on multi-channel coherent modulation and detection that reliably estimates the objective function´s gradient, with respect to the system parameters, in the presence of time delays. The narrowband nature of the excitation signals reduces the unknown dynamics of the objective function to a single parameter per control channel, the phase delay. An efficient implementation of the adaptive control architecture is presented; it incorporates parallel control channels with individually selectable 6-level phase delay adjustment. Initial experimental results indicate wide operating range covering almost 7 decades of excitation frequencies.