How do you design a combined feedforward-feedback control system?

Combined FF-FB system: feedforward handles measured disturbances quickly; feedback corrects for modeling errors and unmeasured disturbances. Design steps: identify major disturbances that can be measured, develop feedforward model (gain and dynamics matching process response), implement feedforward signal summed with feedback output, tune feedback for unmeasured disturbances (can be less aggressive since FF handles primary disturbances). Lead-lag compensation in FF path may be needed to match process dynamics. FF improves disturbance rejection; FB provides accuracy.