Two-tier feedback control system and related method

A feedback control system, comprising:

• a plant, configured to produce an output according to a control signal;
• a first summing block, configured to produce a first difference between an input signal and a measured output signal;
• a first controller, configured to generate the control signal, such that the first difference decreases to be less than a first threshold or is less than the first threshold;
• a second controller, coupled to a memory;
• and
• a second summing block, coupled to the second controller and configured to produce a second difference;
• wherein the first controller comprises the memory configured to store a table, and the table contains information of a plurality of transfer functions corresponding to a plurality of operating conditions;
• wherein the first controller determines an operating condition under which the plant operates, and chooses to utilize a transfer function corresponding to the operating condition to generate the control signal according to the transfer function and the first differences;
• wherein the second controller is configured to update the information contained in the table according to the second difference, such that the second difference decreases to be less than a second threshold or is less than the second threshold.