Understanding biology by reverse engineering the control

摘要

Faced with the problem of controlling a physical system, an engineer will identify a model for the system, and then use this model to design a process for automatically actuating some of the system's input signals in order that the behavior of the system follows a desired profile. The most common control processes use feedback. Consider the example of designing an autopilot function that controls an aircraft to fly at constant altitude (see Fig. 1). A mathematical model of the aircraft dynamics (the plant) is designed, which describes how the aircraft's altitude, pitch, and roll angles (the outputs) change when the elevators, ailerons, and throttle (the inputs) are manipulated. By using sensors to measure the outputs, the engineer uses the model to calculate how these measurements should be employed to automatically adjust the inputs, so that if the aircraft deviates off course, it is guided, quickly and smoothly, back to the desired altitude.