Adaptive control through sinusoidal response

An investigation has been made in the application of sinusoidal techniques to adaptive feedback control systems. The adaptive feature of this approach is an automatic gain control. These systems contain two loops: a basic or primary control loop and an adaptive control loop. The forward-path gain of the basic loop is adjusted by the adaptive loop. A sine wave test signal is added continuously to the basic loop input and to a model. The phase shift or the amplitude of the basic loop output is measured by an adaptive computer which adjusts the forward-path gain in an attempt to hold the measured amplitude or phase-shift constant. This paper contains derivations of the adaptive loop response to changes in the process gain factor for several cases. Some of the considerations pertaining to the design of the adaptive control loop are also given.