Method and apparatus for controlling the rotational speed and phase of synchronous motors

DETAILED DESCRIPTION Briefly stated and according to an aspect of this invention, this aim is achieved by sensing the motion of the poles with respect to the stator by means of an inductive sensor coil.
The sensor signals are converted into corresponding, essentially rectangular sensor pulses.
The constant pulses (of a pulse generator) are compared with the sensor pulses regarding their width and phase.
Driving pulses are generated synchronously with the sensor pulses, with their width proportional to the phase shift.
Their phase, with respect to the poles, is chosen so that, if the pole leads, a braking moment is generated, and, if the pole lags, an accelerating moment is generated.
The pulse generator, for example a quartz oscillator, therefore does not deliver the actual driving pulses, but only controls pulses which form the basis of a comparison.
Using these control pulses, the sensor pulses are measured as regards their width and phase.
It turns out that an increasing pulse width also signals an increasing phase shift.
The reason is that the motion of the poles of the rotor, which is proportional to the rotational speed, depending on the number of poles, either lags behind or leads the pulse frequency.
The width of a driving pulse is proportional to the extent of phase shift.
Since the width of the driving pulses also corresponds to the power consumption of the motor, the motor power is immediately matched to the power demand at the beginning of a phase shift.
In this way, unreasonable phase shifts are immediately equalized.
Furthermore, the process of sensing the phase shift of the sensor pulse with respect to the generator pulses furthermore determines which sign the phase shift has, or respectively whether the rotor is leading or trailing.
The moment of generating the driving pulses is chosen with respect to the respective pole position in such a manner that either a braking or an accelerating action is exerted on the rotor.
The measures specified above achieve a quasi-continuous proportional control, which partically has no dead time