Control Modes of Step Motors

The problem of maximizing the output torque of a step motor while satisfying power dissipation constraints is considered. Also, the optimal current which maximizes the output torque is derived. Several suboptimal controls are compared to the optimal one and their relative efficiency is evaluated. It is shown that the most common control mode is the least efficient from this viewpoint.     

Eliminating False Lock in Phase-Locked Loops

A model is developed for phase-locked loops incorporating phasefrequency detectors. This model facilitates analysis of the loop and enables us to derive the conditions for false lock. It is shown by analysis that phase-locked loops with phase-frequency detectors are indeed capable of false lock; this theoretical result is verified by experimental results. A method for eliminating false lock is then proposed. This method was implemented in a simple circuit; we present the results of this experiment and show that the method we propose is capable of eliminating false lock.