Some of the more commonly occurring drive systems are presented using linear transfer functions within each and every block of these diagrams. In real designs, nonlinear elements frequently occur. However, such nonlinear components cannot be approximated by linear differential equations with constant coefficients (e. g., Laplace solution technique) and, therefore, this introductory text limits the analysis to mostly linear systems.
The most commonly used electromechanical system is that of Fig. 2.15 operating at about constant speed without feedback control. The speed regulation is defined as