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.