Method of controlling the rotation of a rotary body and apparatus thereof

An apparatus for controlling the speed of a mechanically driven rotary body, said body being the rotor of an electromagnetic measuring and control drive controllable as a function of the magnitude and the direction of the difference between the actual signal and the desired signal of the rotary body, said apparatus including:

• sweep oscillator means for providing a variable second signal F.sub.2 which is synchronized with a first set desired signal F.sub.1 in normal condition, capable of being fed to the rotary body,
• coincidence detector means for detecting the coincidence of the second signal F.sub.2 with an actual thrd signal F.sub.3 generated from said rotary body in proportion to the revolution speed of said rotary body,
• comparator means for comparing the first signal F.sub.1 with the actual third signal F.sub.3,
• sweep-voltage controller means for determining the direction and amplitude of the voltage of the sweep oscillator means, said controller means being connected to the comparator means and to the coincidence detector means, and
• phase comparator means for comparing the first signal F.sub.1 with the second signal F.sub.2,
• in which when the third signal F.sub.3 is not synchronized with the second signal F.sub.2, said oscillator means being adapted to sweep the second signal F.sub.2 till a coincidence exists with the third signal F.sub.3 through the sweep-voltage controller means in response to the output voltage of the comparator means, based on the deviation between said first and third signals on occurrence of a difference lying within the predetermined tolerance range, after which said sweep oscillator means sweeps the second signal F.sub.2 till coincidence exists with the first signal F.sub.1 in response to the output voltage of the coincidence detector means, and thereafter the second signal F.sub.2 being fixed to the first signal F.sub.1 by the phase comparator means and the sweep oscillator means, so that the speed of rotation of the rotary body is locked constantly to the first desired signal F.sub.1.