Control Theory

Control theory studies input-state-output systems: how external signals drive state evolution, which states we can reach (controllability) and observe (observability), and whether the system remains bounded under perturbation (stability). These questions have definitive algebraic answers, independent of the domain. We apply control-theoretic machinery to pharmacological compartmental models, recognising that compartments are states, drug inputs are control signals, and measurements are outputs; the theory then tells us what is possible and what is unidentifiable at arbitrary scale.