RU2422767C1 - Roughness indicator to control electrical machine commutator micro geometry - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: proposed indicator comprises eddy current transducer mounted above commutator surface and consisting of differential amplifier and bridge. One arm of said bridge is formed by metering and compensating coils while another one is made up of pure resistors. Bridge central points are connected to differential amplifier inputs. Buffer amplifier is connected to differential amplifier output. Buffer amplifier is connected with first amplitude detector and circuit that coverts phase response into amplitude response. Circuit that converts phase response into amplitude response consists of zero detector, current limiting resistor, band pass filter and second differential amplifier, and is connected to second amplitude detector. First and second amplitude detectors are connected with first and second output differential amplifiers, respectively. Output differential amplifiers are connected with recorder and micro controller connected via communication links converter with personal computer. Micro controller is also connected with band pass filter with buffered and connected with eddy current transducer and aforesaid conversion circuit. ^ EFFECT: simplified measurement. ^ 5 dwg

Description

The invention relates to the field of measurement technology and can be used in various industries for dynamic control of microgeometry of rotating conductive cylindrical parts, in particular the working surface of the collectors of electrical machines.

A device for non-contact profilometer for monitoring the microgeometry of the collectors of electrical machines [USSR Author's Certificate No. 1260672, IPC G01B 7/12, publ. 09/30/1986]. A non-contact profilometer for monitoring the microgeometry of the collectors of electrical machines, comprising a displacement transducer, a measuring circuit connected to its output, a measuring signal processing unit associated with the output of the measuring circuit, a control unit connected to the second and third inputs of the measuring signal processing unit, a recorder associated with the output processing unit of the measuring signal. The second displacement transducer mounted above the working surface of the monitored collector is offset relative to the first transducer by half of the collector division in the tangential direction and is connected to the input of the control unit. The control unit contains a circuit from a series-connected measuring circuit, a comparator, a limiter, a reference signal source connected to the second input of the comparator, a reset circuit, the input of the measuring circuit is an input, and the outputs of the limiter and reset circuit are the outputs of the control unit.

The disadvantage of this device is the use of an additional displacement transducer. The known profilometer does not take into account differences in the specific electrical conductivities of the collectors of electrical machines, which affect the measurement result.

Also known is a non-contact profilometer for monitoring the microgeometry of the collectors of electrical machines [USSR Author's Certificate No. 1397714, IPC G01B 7/12, publ. 05/23/1988]. The non-contact profilometer for monitoring the microgeometry of the collectors of electric machines is equipped with a circuit of serially connected rectangular pulse shaper, a frequency-voltage converter and a controlled low-pass filter with a bipolar switch, two gates, an output of a controlled low-pass filter through bipolar switches and normally open contacts of a bipolar switch connected to the inputs memory elements, the input of the shaper of rectangular pulses and the second input of the control yaemogo low frequency filter connected to the output of the measuring circuit, and outputs the keys are connected to respective normally closed double pole switch.

The well-known profilometer also does not take into account the differences in the specific electrical conductivities of the collectors of electrical machines, which affect the measurement result.

The closest adopted for the prototype is a device for studying mechanical factors in collector electrical machines [A.I. Skorospeshkin, L.Ya. Zinner, A.I. Proshin // Bulletin of TPI. - 1966. - T. 160. - S.162-167]. The device consists of an independent excitation generator connected to the excitation windings of the measuring sensors. The inductive measuring sensor of small displacements and the compensation sensor are connected in such a way that the electromotive force (EMF) on the winding of the compensation sensor is out of phase with the EMF of the measuring sensor. The differential EMF of the windings is fed to the emitter follower. The emitter follower is connected to a resonant amplifier and a millivoltmeter. The millivoltmeter is connected to an independent excitation generator. The resonant amplifier is connected to a video amplifier.

The known device does not take into account differences in the specific electrical conductivities of the collectors of electric machines, which affect the measurement result, therefore, it is necessary to perform a preliminary calibration for various collectors of electric machines. To eliminate the effect of vibration on the measurements of the collector profile, it is necessary to install a second measuring sensor above the shaft surface of the electric machine.

The objective of the invention is to simplify the process of measuring microgeometry of the collectors of electrical machines.

The problem is solved due to the fact that the profilometer for monitoring the microgeometry of the collectors of electrical machines, as in the prototype, contains an eddy current transducer that contains the excitation windings of the measuring and compensating coils. The eddy current transducer is mounted above the working surface of the monitored collector.

According to the invention, the eddy current transducer consists of a differential amplifier and a bridge, with one arm of the bridge formed by a measuring and compensating coil, and the other by active resistances.

The midpoints of the shoulders of the bridge are connected to the inputs of the differential amplifier. A buffer amplifier is connected to the output of the differential amplifier, which is connected to the first amplitude detector and a circuit for converting the phase response to amplitude. The phase-to-amplitude response conversion circuit consists of a series-connected zero detector, a current-limiting resistor, a bandpass filter, and a second differential amplifier and is connected to a second amplitude detector. The first and second amplitude detectors are connected to the first and second output differential amplifiers, respectively. The output differential amplifiers are connected to a recorder and a microcontroller, which is connected to a personal computer through a level converter. The microcontroller is also connected to an output buffered second bandpass filter connected to an eddy current transducer and a phase to amplitude response circuit.

The proposed design of the profilometer makes it possible to distinguish two components from the signal of the eddy current transducer taken from the output - a change in the signal amplitude and a change in the phase shift between the output and input signals of the eddy current transducer under the influence of the collector of an electric machine. The presence of digital potentiometers in the switching circuit of the output differential amplifiers allows you to programmatically adjust the level of the output signals of the differential amplifiers to the optimum limits for the recorder and the analog-to-digital converter of the microcontroller.

The present invention allows the measurement of the distance between the eddy current transducer and the collector of an electric machine without preliminary graduation of the studied collector by taking into account the specific electrical conductivities of the collector plates of the electric machine.

Figure 1 presents the functional diagram of the inventive profilometer to control the microgeometry of the collectors of electrical machines.

Figure 2 shows the functional diagram of the eddy current transducer.

Figure 3 shows a functional diagram of the conversion of the phase response to the amplitude.

Figure 4 shows a functional diagram of the output differential amplifier.

Figure 5 shows a functional diagram of a band-pass filter.

The profilometer for monitoring the microgeometry of the collectors of electric machines contains an eddy current transducer 1 (VTP) (Fig. 1), which consists of a differential amplifier 2 and a bridge (Fig. 2). One shoulder of the bridge is formed by a measuring coil 3 and a compensating coil 4 with rod ferrite cores, and the other by active resistances 5 and 6, the values of which correspond to the complex resistances of the measuring and compensating coils, respectively. The arm of the bridge formed by the active resistances 5 and 6 is connected to the inverting input of the differential amplifier 2, and the arm formed by the coils 3 and 4 is connected to the non-inverting input of the differential amplifier 2.

To the eddy current transducer 1 (ECP) is connected to a buffer amplifier 7 (CU) (figure 1). The output of the differential amplifier 2 (figure 2) of the eddy current transducer 1 (ECP) is connected to the inverting input of the buffer amplifier 7 (CU) (figure 1). The common bus of the eddy current transducer 1 (VTP) is connected to the non-inverting input of the buffer amplifier 7 (CU). The eddy current transducer 1 (ECP) and the buffer amplifier 7 (CU) are connected using twisted pair. The first amplitude detector 8 (AD1) and the circuit for converting the phase response to amplitude 9 (FA) are connected to the buffer amplifier 7 (BU).

The scheme for converting the phase response to amplitude 9 (FA) (Fig. 3) consists of a serial connection of a zero detector 10, a current-limiting resistor 11, an LC strip filter 12, and a differential amplifier 13. The output of the buffer amplifier 7 (BU) is connected to the inverting input of the zero detector 10, the non-inverting input of the zero detector 10 is connected to a common bus. The band-pass LC filter 12 is connected to the inverting input of the differential amplifier 13.

The output of the circuit for converting the phase response to amplitude 9 (FA) is connected to the input of the second amplitude detector 14 (AD2) (Fig. 1). Amplitude detectors 8 (AD1) and 14 (AD2) are connected to the output differential amplifiers 15 (VDU1) and 16 (VDU2), respectively.

The output differential amplifiers 15 (VDU1) and 16 (VDU2) are identical and consist of a tool amplifier 17 (Fig. 4) with digital potentiometers 18 and 19 connected to it. The inverting output amplifiers 15 (VDU1) and 16 (VDU2) are inverting the inputs of the instrumentation amplifiers 17. The digital potentiometer 18 is connected by a voltage divider between the supply voltage and the common bus to the non-inverting input of the instrumentation amplifier 17. The digital potentiometer 19 is connected to the instrument gain variation circuit Nogo amplifier 17, respectively. [http://shtz.shadrinsk.net/library/doc/ad/prod/descript/ad622.pdf]

The outputs of the output differential amplifiers 15 (VDU1) and 16 (VDU2) (Fig. 1) are connected to the input of the analog-to-digital converter of microcontroller 20 (MK) [Evstigneev A.V. Mega AVR Microcontrollers: User Manual / A.V. Evstigneev. - M.: Dodeka-XXI Publishing House, 2007. - 592 p., P.401] and registrar 21 (P). The microcontroller 20 (MK) is connected to the digital potentiometers 18, 19 (not shown in FIG. 4) of the output differential amplifiers 15 (VDU1) and 16 (VDU2) by a serial interface. The microcontroller 20 (MK) has two-way communication with a personal computer 22 (PC) through a level converter 23 (PU) (figure 1). In addition, the microcontroller 20 (MK) is connected to a band-pass filter 24 (PF).

The band-pass filter 24 (PF) consists of a series connection of a current-limiting resistor 25, a band-pass LC filter 26 and a buffer amplifier 27 (Fig. 5).

The band-pass filter 24 (PF) is connected to the eddy current transducer 1 (ECP) and a phase-to-amplitude-to-amplitude conversion circuit 9 (FA) (FIG. 1). The output of the bandpass filter 24 (PF) is connected to the non-inverting input of the differential amplifier 13 of the circuit for converting the phase response to amplitude 9 (FA) (Fig. 3).

Eddy current transducer 1 (VTP) has an electromagnetic coupling with the collector of an electric machine 28 (KEM) (Fig. 1).

The buffer amplifier 7 (BU) can be performed on the operational amplifier LM318, included in the differential circuit, to the inputs of which a current-sensing resistor is connected. The first amplitude detector 8 (AD1) is assembled as a serial connection of a large-scale amplifier based on the LM318 operational amplifier, a current-limiting resistor, and an asymmetric voltage doubler of the first kind, assembled from ceramic capacitors and high-speed diodes [http://www.cqham.ru/uu1. htm]. The second amplitude detector 14 (AD2) can be performed as a series connection of a current-limiting resistor and an asymmetric voltage doubler of the first kind, assembled from ceramic capacitors and high-speed diodes [http://www.cqham.ru/uu1.htm]. The output differential amplifiers 15 (VDU1) and 16 (VDU2) can be performed on the instrument operational amplifier AD622. An Atmega8 microcontroller may be selected as the microcontroller 20 (MK). As the recorder 21 (P) can be an oscilloscope or a high-speed ADC for subsequent processing. The level converter 23 (PU) can be performed on the basis of the MAX232 chip.

As differential amplifiers 2 and 13 (figure 2, 3) can be selected precision high-speed operational amplifier OP37, included in the differential circuit.

The zero detector 10 (figure 3) can be performed on the basis of the operational AD8021 amplifier without feedback.

As digital potentiometers 18, 19 (figure 4) can be used microcircuit AD7376.

The buffer amplifier 27 (Fig. 5) can be made on the basis of the high-speed buffer BUF634.

The device operates as follows. In the initial state, the microcontroller 20 (MK) (figure 1) produces an alternating rectangular signal of the excitation frequency of the eddy current transducer 1 (ETC). This signal is fed to a band-pass filter 24 (PF), where its main harmonic, corresponding to the excitation frequency of the eddy current transducer 1 (ETC), is highlighted. Next, the filtered signal enters the eddy current transducer 1 (ECP). If the collector of the electric machine 28 (KEM) is absent in the range of the measuring coil 3 (Fig. 2), the arms of the bridge of the eddy current transducer 1 (ETC) will be balanced, and a signal close to zero will be output at the output due to the non-absolute identity of the arms of the bridge. When the eddy current transducer 1 (ETC) interacts (Fig. 1) with the collector of an electric machine 28 (CEM), the bridge arms are out of balance, and the output signal of the eddy current transducer 1 (ECP) changes in amplitude and phase shift relative to the input signal. The degree to which the shoulders go out of balance depends on the distance between the eddy current transducer 1 (ETC) and the collector of electric machine 28 (KEM), on the physical properties of the collector plates of electric machine 28 (KEM). The mismatch signal is amplified by the amplifier 2 (Fig. 2) of the eddy current transducer 1 (ECP) and enters the buffer amplifier 7 (CU) (Fig. 1). The current-amplified signal enters the first amplitude detector 8 (AD1) to determine the amplitude response and into the circuit for converting the phase response to amplitude 9 (FA) to determine the phase response. In the scheme for converting the phase response to amplitude 9 (FA) (Fig. 3), the input signal from the buffer amplifier 7 (BU) passes through a zero detector 10, where the signal is normalized in amplitude, while maintaining the magnitude of the phase shift. Then this signal passes through the current-limiting resistor 11 and the band-pass LC filter 12 with a resonant frequency equal to the excitation frequency of the eddy current transducer 1 (ETC) (Fig. 1). After passing through the band-pass LC filter 12 (Fig. 3), the main harmonic is extracted from the signal supplied to the inverting input of the differential amplifier 13. A signal from the band-pass filter 24 (PF) is received at the non-inverting input of the differential amplifier 13 (Fig. 1). Provided that the amplitudes of the output signals of the band-pass filter 24 (PF) and the band-pass LC filter 12 are equal, the amplitude of the output signal of the differential amplifier 13 will be determined only by the magnitude of the phase shift between the output signal of the eddy current transducer 1 (ECP) and the signal from the band-pass filter 24 (PF ), which is the input signal of the eddy current transducer 1 (ECP). After the conversion of the phase response to amplitude 9 (FA), the signal is fed to the second amplitude detector 14 (AD2). After the amplitude detectors 8 (AD1) and 14 (AD2), the AC signals passing through them are converted into DC signals. From the amplitude detectors 8 (AD1) and 14 (AD2), the signals are fed to the inverting inputs of the output differential amplifiers 15 (VDU1) and 16 (VDU2), respectively. Digital potentiometers 18, 19 (FIG. 4) of the output differential amplifiers 15 (VDU1) and 16 (VDU2) are controlled by a microcontroller 20 (MK) (FIG. 1). The inclusion of digital potentiometers allows you to change the gain of instrumental amplifiers and the value of the constant component of the output signal of the output differential amplifiers 15 (VDU1) and 16 (VDU2). The output signals from the output differential amplifiers 15 (VDU1) and 16 (VDU2) are fed to the recorder 21 (P). Through the level converter 23 (PU), the data digitized by the microcontroller 20 (MK) is transferred to a personal computer 22 (PC), by which the operator can assess the need to change the resistance of the digital potentiometers of the output differential amplifiers 15 (VDU1) and 16 (VDU2). It is possible to change the resistance of the digital potentiometers on command from a personal computer 22 (PC).

By the combination of the amplitude and phase response, one can judge the distance between the eddy current transducer 1 (ETC) and the collector of the electric machine 28 (KEM), as well as the physical properties of the collector plates, for example, such as electrical conductivity. Using digital potentiometers 18 and 19 (figure 4), you can set the required level of the constant component, symbolizing the absence of the collector of the electric machine 28 (KEM) in the control zone of the eddy current transducer 1 (VTP), the maximum output signal level of the output differential amplifiers 15 (VDU1) and 16 (VDU2), corresponding to the highest possible level for the registrar 21 (P). According to the previously taken dependences of the distance between the eddy current transducer 1 (ETC) and various collectors of electric machines 28 (KEM) with known properties, build correspondence tables, which are then used to determine the electrical conductivity of the collector plates and the distance between the eddy current transducer 1 (ECP) and the collector Machine 28 (CEM). The speed of the proposed device allows you to work out rapidly changing interactions between the profile of the collector of electric machines 28 (KEM) and eddy current transducer 1 (VTP).

Thus, the proposed facility allows the measurement of microgeometry of the collectors of electrical machines without their preliminary calibration.

Claims (1)

A profilometer for monitoring the microgeometry of the collectors of electrical machines, comprising an eddy current transducer mounted above the working surface of the monitored collector, which contains the field windings of the measuring and compensating coils, characterized in that the eddy current transducer consists of a differential amplifier and a bridge, while one bridge arm is formed by measuring and compensating coils and the other with active resistances, and the midpoints of the shoulders of the bridge are connected to the inputs of the different a potential amplifier, the output of which is connected to a buffer amplifier, which is connected to the first amplitude detector and a circuit for converting the phase response to amplitude, which consists of a series-connected zero detector, a current-limiting resistor, a bandpass filter, and a second differential amplifier, and the phase to amplitude converting circuit is connected to the second amplitude detector, and the first and second amplitude detectors are connected respectively to the first and second output differential amplifiers that are connected to a recorder and a microcontroller connected via a level converter to a personal computer, and to a second bandpass filter, which is buffered by the output, which is connected to an eddy current converter and a phase to amplitude conversion circuit.

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