| 摘要 |
1. Means for controlling the speed of an element (1) driven by a motor (2) and comprising : - a sensor (3) of the speed of the element (1), the sensor being adapted to output signals whose frequency depends upon the speed of the element (1) ; - a frequency-voltage converter (6) adapted to match to the frequency of the signals from the sensor (3) a voltage which depends upon such frequency and which comprises a mean d.c. component and an alternating component (a) ; - means (13) for comparing such voltage with a reference voltage corresponding to a predetermined speed set value, the comparison means being adapted to output a signal dependent upon the comparison result, and - driving means (19) which respond to the output signal of the comparison means (13) and which are adapted to act on an element (g) for adjusting the speed of the motor in a sense tending to restore the speed of the element to the required value, characterised in that the frequency-voltage converter (16) is adapted to output a voltage whose a.c. component (a) has the shape of a saw tooth having a curved portion (aI) ; in manner known per se the comparison means comprise two comparators (13a, 13b) associated with overshoot and undershoot respectively of the speed of the element (1), the flipflop thresholds (S1, S2) of the comparators being offset on either side of the voltage corresponding to the predetermined set value of the same or substantially the same absolute value (e), the difference between the two thresholds being substantially equal to the amplitude of the residual a.c. component ; the whole being such that the motor-controlling element is actuated more vigorously in one direction than in the other. |
