Hybrid digital/analogue servomechanisms

The paper is an introduction to hybrid digital/analogue servo systems utilizing the application of digital techniques to conventional closed-loop servo systems. The term hybrid is used to describe systems where the error signal is derived digitally and then converted into an analogue signal for the operation of the power source. This results in an improved system accuracy compared with that obtainable using conventional analogue methods, and avoids many of the difficulties associated with the pure digital approach. An introduction consisting of a comparison of the salient features of analogue and hybrid servo systems provides a background against which the underlying principles and design features of both velocity and position servo systems are discussed. The constituent elements of each system are derived in block diagram form with parallel references to their analogue counterparts. The paper concludes with an assessment of the advantages of hybrid servomechanisms and a brief review of the various fields of application of such systems.