SU993125A2 - Shaft rotation angular speed pickup - Google Patents

Description

. (S) ANGULAR SPEED ROTATION SHAFT SENSOR

The invention relates to automation and measurement technology and can be used to determine the speed of shafts of mechanisms and machines. By axis auth. JP 6071 is well known for an angular velocity sensor for shaft rotation, which contains a serrated conductive disk and an inductor included in a measuring circuit. In order to increase the modulation depth of the output signal, the grooves of the conductive disk are filled with a ferromagnet SP closed around the circumference. The disadvantage of this sensor is low noise immunity to industrial noise and pulsed electromagnetic fields, which makes it difficult to use in a number of mechanisms and machines. The high sensitivity of this sensor to interference is caused by the fact that when it is operated, the stator inductance varies within certain limits, its sign does not change, and the inductance always remains greater than zero, therefore when exposed to the stator coil and conductors connecting it to the autogenerator circuit, external electromagnetic fields, the generator excitation conditions change (phase balance and amplitude balance), the latter leads to parasitic amplitude and frequency modulation of the output signal. The imposition of parasitic modulation on the modulation caused by the rotation of the rotor reduces the accuracy of the measurement of the angular velocity and leads to the appearance of failures in the readings of the recording device connected to the output of the sensor. The purpose of the invention is to improve the noise immunity of the sensor of the angular velocity of rotation of the shaft. The goal is achieved by the fact that a second inductance coil is inserted into the angular velocity sensor of rotation, and the first and second inductors are tooth-shaped with a pitch equal to the pitch of the rotor teeth, and are shifted one relative to the other by half their tooth division, while both inductance coils are connected to the circuit of the generator. FIG. 1 shows the design of an angular velocity sensor for a shaft; in fig. 2 is a schematic of the stator inductors; in fig. timing charts of sensor signals with continuous rotation of the rotor. The angular velocity sensor of the shaft (Fig. 1) contains an input shaft 1 centered in rotating supports 2 installed in a detachable core 3. On the shaft 1 is a rotor rigidly fixed, made of a diamagnetic material such as aluminum alloy D-16) with radial ones. slots filled with a ferromagnet closed in a circle. In the housing 3 is fixed the stator 5 with the first 6 and second 7 coils inductance (figure 2). The stator is a dielectric disc with radial slots evenly spaced around the circumference in which the first 6 and second 7 inductors are laid, having an angular pitch T equal to the pitch of the rotor teeth k. At the same time, the induction coils are displaced one relative to another by an angle by half of their tooth division. The intrinsic electromagnetic coupling M between the first and second inductors (with the rotor removed) is zero due to the fact that the emf induced in each section of one coil from the symmetrically located sections of the second coil is equal in magnitude and opposite in sign. Datmic works as follows. When the rotor rotates, its teeth successively overlap the poles of the first and second stator inductors, thereby changing the effective screen area of the coils and, therefore, their sinusoidal ratio H sinusoidally (Fig. 3). The value of M varies from the maximum positive value (zero) to the maximum negative value. The passage of the rotor teeth over the poles of the coils leads to a breakdown of 9 54 oscillations of the oscillator (not only the amplitude balance condition is violated but also the phase balance condition), since the electromagnetic coupling coefficient of the coils takes a negative value. When the coil poles overlap with sections of the rotor grooves filled with a ferromagnet, M becomes positive and the autogenerator is excited - (the condition of amplitude and phase balance is satisfied). Thus, at the output of the oscillator, a voltage U is formed, which is a bundle of high-frequency oscillations (Fig. 3). The use of two inductors in the sensor with an alternating electromagnetic coupling factor M as a function of the rotation angle of the rotor ensures that the sensor is insensitive to pulsed electromagnetic interference and improves the stability of the moments of excitation and breakdown of oscillations of the oscillator, as the latter changes at the moment of change the sign of the communication of the coils (at the transition of M through zero). A change in the sign of the electromagnetic coupling can occur either when the rotor is turned or when the current is changed in only one of the coils. When exposed to electromagnetic interference, the direction of the induced current is the same in both closely-spaced coils evenly distributed on the stator. Consequently, the electromagnetic coupling between the coils does not change sign due to interference and does not change the conditions for the excitation or breakdown of oscillations of the oscillator. When the rotor positions correspond to the positive half-wave of the electromagnetic coupling of the M coils, the generator is in the excitation mode regardless of the magnitude and form of pick-up, and when the rotor positions correspond to the negative half-wave, the generator is rigidly locked and the sensor is insensitive to external electromagnetic effects that eliminates false alarms at the sensor output. The stability of the moments of excitation and the breakdown of oscillations is increased by establishing the maximum degree of coupling between the active element of the oscillator and the inductors. In the famous sensor it sde59

It is impossible because the inductance of the coil does not change sign and when a certain amount of coupling between the active element and the coil is exceeded, the oscillation stalling stops and the sensor becomes inoperative.

Bundles of high-frequency oscillations from the output of the autogenerator are fed to an amplitude detector, at the output of which rectangular pulses form and, (Fig. 3), are fed to a recording device. Since the frequency of excitations and disruptions of oscillations of the oscillator is proportional to the angular velocity of the rotor, the readings of the recording device correspond to the measured angular velocity of rotation.

The output signal of the sensor is square-wave pulses with a large steepness of the fronts, thereby improving the accuracy of measuring small angular velocities in the presence of intense interference.

When an electronically counted frequency meter is used as a recording instrument, it is possible to obtain an indication on a digital display board directly in units of rotation speed (rpm). For this, the rotor of the sensor is performed with the number of slots equal to 60, and the counting time of the frequency meter is set to 1 The lower limit of the range of measured speeds is 1 rpm, and the upper limit reaches 30 thousand rpm. and. limited by mechanical strength of structural elements.

The presence of the second additional stator winding, offset from the first by half of their teeth

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division, allows you to accurately record the moments of excitation and disruption of oscillations of the oscillator, regardless of external disturbing factors. This makes it possible to increase the noise immunity and accuracy of the sensor when it is used under conditions of intense electromagnetic interference (as part of electric welding equipment, high-frequency heating installations, in electromagnetic detector equipment).

The proposed sensor is advantageously different from the known possibility of simplifying the measuring circuit and increasing the length of the connecting cables, which eliminates the need to develop a number of sensors having close ranges of measured rotational speeds.

Claims (1)

1. USSR author's certificate No. 6071, cl. G 01 P, 1978. 7l // rji I I I (PU9.3 ( I