CN116298369A

CN116298369A - Motor rotating speed measuring device and method based on non-contact type magnetic rotation position sensor

Info

Publication number: CN116298369A
Application number: CN202310369208.XA
Authority: CN
Inventors: 王威; 方挺; 刘帅; 刘强庆
Original assignee: Anhui University of Technology AHUT
Current assignee: Anhui University of Technology AHUT
Priority date: 2023-04-04
Filing date: 2023-04-04
Publication date: 2023-06-23

Abstract

The invention discloses a motor rotating speed measuring device and method based on a non-contact magnetic rotating position sensor, and belongs to the field of motor rotating speed measurement. The method comprises the following steps: 1. collecting pulse signals of the motor rotating for one circle, and roughly calculating a motor rotating speed value; 2. combining the rough speed value to obtain a pulse frequency and selecting a sampling frequency; 3. based on the sampling frequency, collecting the voltage value of the pulse signal output by the A/B pin of the sensor, and processing the sampled data in real time; 4. performing FFT (fast Fourier transform) on the processed data, performing complex modular value operation on the conversion result, obtaining the amplitude of each point, and selecting a sequence n of the point with the maximum amplitude to obtain the frequency F of the pulse signal; 5. and (3) carrying out speed conversion according to the frequency F to obtain a motor rotation speed value. The invention uses an analog quantity acquisition method, converts a time domain signal into a frequency domain signal through an FFT (fast Fourier transform) algorithm, and then converts a frequency value of a pulse into the rotating speed of the motor, thereby improving the precision of rotating speed calculation and the speed measuring range.

Description

Motor rotating speed measuring device and method based on non-contact type magnetic rotation position sensor

Technical Field

The invention relates to the technical field of motor rotation speed measurement, in particular to a motor rotation speed measurement device and method based on a non-contact magnetic rotation position sensor.

Background

With the rapid development of industrial automation and artificial intelligence, motors are widely used and developed in present industrial automation devices or household appliances. The rotational speed is a state parameter of great importance for the motor, and its measurement accuracy will directly affect the accuracy of the testing of other relevant parameters and characteristics of the motor and fault detection and diagnosis.

The main measuring methods currently include a centrifugal tachometer testing method, a tachometer generator velocimetry, a flash velocimetry, a photoelectric encoder velocimetry, a Hall element velocimetry and the like. In the above-mentioned method, the sensor is required to be coaxially installed in many cases, the coaxiality requirement is high, and the installation difficulty is relatively high. Slightly skewed, the final reading is affected. And are hard-wired, not only are mechanical wear present, but also reduce the useful life of the encoder and system. Although the Hall element speed measuring method does not need hard connection, a special speed measuring turntable needs to be processed, and the spindle is provided with a hole for fixing, so that the installation process is complex, the precision is low, and the method is only suitable for occasions with general precision requirements.

The common digital rotating speed acquisition and calculation method mainly comprises the following 3 types: m method (frequency method), T method (period method), M/T method (frequency/period method). The M method has higher measurement precision when the measured rotating speed is higher or the number of rotating speed pulse signals sent by the motor rotating for one circle is larger, so that the M method is suitable for high-speed measurement; the T method has higher measurement precision when the measured rotating speed is lower (the time of two adjacent rotating speed pulse signals is longer), so the T method is suitable for low-speed measurement; the M/T method is to measure the detection time and the number of the rotation speed pulse signals generated by the photoelectric pulse generator in the detection time to determine the rotation speed. Because the two pulse signals are counted at the same time, the M/T method can only have higher speed measurement precision if the 'simultaneity' processing is proper.

After searching, patent publication number CN 104426439A, the invention creates the name: a method and apparatus for monitoring the rotational position of an electric motor, which application monitors the signal output from the pulsed rotational position sensor and a reference signal associated with a control signal for the electric motor. A position of the rotor of the motor coincident with the reference signal is determined based on a nominal rotor position, a nominal rotational speed of the rotor, and a time between the reference signal and a falling edge of a signal output from the pulsed rotational position sensor. The signal acquisition method used in the application captures the number of sensor pulse signals in a time interval, and the speed calculation method is an M/T method. Therefore, the application has the problems that the measuring precision is not high, the measuring range is small, the application is not suitable for high-speed measurement, and the measuring inaccuracy is caused by the ringing effect of the pulse signal at high speed.

Disclosure of Invention

1. Technical problem to be solved by the invention

Aiming at the problems of poor speed measurement precision, small speed measurement range, strict synchronization requirement of a controller system and high installation requirement existing in the motor speed measurement scheme in the prior art, the invention provides a motor speed measurement device and method based on a non-contact magnetic rotation position sensor. The invention uses an analog quantity acquisition method, namely, the signal voltage is acquired, the time domain signal is converted into the frequency domain signal through a Fast Fourier Transform (FFT) algorithm, and then the frequency value of the pulse is converted into the rotating speed of the motor, so that the precision of the rotating speed calculation is improved.

2. Technical proposal

In order to achieve the above purpose, the technical scheme provided by the invention is as follows:

the invention relates to a motor rotating speed measuring method based on a non-contact magnetic rotating position sensor, which comprises the following steps:

step one, collecting a pulse signal output by one turn of motor rotation, and roughly calculating a motor rotation speed value based on the pulse signal;

step two, combining the rough speed value of the motor to obtain the pulse frequency output by the A/B pin of the sensor, and selecting the sampling frequency based on the pulse frequency;

step three, based on sampling frequency, collecting pulse signal voltage values output by an A/B pin of the non-contact magnetic rotation position sensor, and processing sampled data in real time;

performing FFT (fast Fourier transform) on the data processed in the step three, performing complex modular value operation on the conversion result, obtaining the amplitude of each point, selecting a sequence n of points with the maximum amplitude, and obtaining the frequency F of a pulse signal output by an A/B pin of the sensor based on the sequence number;

and fifthly, performing speed conversion according to the pulse signal frequency F output by the A/B pin of the sensor to obtain a motor rotating speed value.

Further, in the first step, a radial magnetized circular magnet of the magnetic rotation position sensor is arranged in a non-magnetic circular bushing, and the bushing is fixed on a motor shaft and keeps the axis consistent; the magnet is arranged on the motor shaft, a pulse signal is output every time the magnet rotates for one circle, the Index pin of the magnetic rotation position sensor acquires the pulse signal, the interrupt function of the singlechip pin is used for acquiring the pulse signal of the Index pin of the sensor, the time interval delta T of two adjacent pulses is recorded, and then the rough speed value of the motor is obtained

In the second step, the resolution PPR of the magnetic rotation position sensor is first determined, and the pulse frequency f=ppr×v outputted from the a/B pin of the sensor is obtained by combining the rough motor speed value, and the pulse frequency f greater than 2 times is selected as the sampling frequency f _s 。

And thirdly, sequentially storing the pulse signal voltage values output by the A/B pins of the acquired sensor into a sampling buffer area according to the sampling time sequence, and selecting 2048 sampling point values forward from the sampling buffer area in real time by taking the position storing the current sampling point value as a starting point, and performing amplitude limiting filtering.

And step five, dividing the pulse signal frequency F output by the A/B pin of the sensor by the resolution of the sensor, and converting the divided signal frequency F into a motor rotating speed value.

Further, after FFT conversion is carried out on the sampled data, a real part and an imaginary part of the amplitude of the corresponding frequency point are obtained, the phase angle of the corresponding A/B phase is obtained based on the real part and the imaginary part, and the rotation direction of the motor is judged according to the phase angle.

Further, step four uses a time-decimated radix-2 FFT algorithm to convert the signal from the time domain to the frequency domain.

The invention relates to a motor rotating speed measuring device based on a non-contact magnetic rotating position sensor, which comprises a power supply module, a main control chip, the magnetic rotating position sensor, a display screen and a communication module, wherein the magnetic rotating position sensor adopts a non-contact rotary encoder SC60104 and uses an orthogonal A/B output mode; the main control chip adopts an AT32F403ACGT7 singlechip, an ADC module in the singlechip collects the voltage value of a pulse signal output by an A/B pin of the sensor chip; the rotating speed and the rotating direction of the motor are displayed on a display screen in real time, the singlechip is communicated with the upper computer or the specific terminal through the RS-485 communication interface, and the power supply module supplies power by using an external power supply or a lithium battery.

3. Advantageous effects

Compared with the prior art, the technical scheme provided by the invention has the following remarkable effects:

(1) According to the motor rotating speed measuring method based on the non-contact magnetic rotation position sensor, a traditional method for collecting the number of pulses is abandoned on pulse signal collection, and pulse signal voltage is collected instead. The traditional method for collecting the number of pulse signals is suitable for a low-resolution sensor, has low precision and cannot carry out software filtering. The invention collects pulse signal voltage, belongs to an analog quantity collection mode, can use high sampling rate, is applicable to a high-resolution sensor, and has high precision.

(2) In view of the fact that the sampling precision is low when the motor is at a low rotating speed, the variable sampling frequency method is adopted, namely the number of pulse signals of the Index pins of the sensor is calculated in real time, the rotating speed value of the motor is calculated roughly, and the proper sampling frequency is selected according to the rough value, so that the low sampling frequency is automatically selected when the motor is at a low rotating speed, and the high sampling frequency is automatically selected when the motor is at a high rotating speed. Therefore, on the premise of ensuring the signal integrity, the proper sampling point number can be selected to participate in the subsequent FFT operation, so that the memory overhead is saved and the running speed of the system is increased.

(3) The motor rotating speed measuring device based on the non-contact magnetic rotating position sensor is convenient to install by adopting a non-contact rotary encoder, improves the measuring efficiency, acquires analog voltage values of pulse signals output by an A/B pin of a sensor chip by using an ADC module in a singlechip, improves the sampling speed and the precision, and improves the rotating speed calculation precision by using an FFT (fast Fourier transform) algorithm.

Drawings

FIG. 1 is a schematic hardware structure of a motor speed measuring device based on a non-contact magnetic rotation position sensor according to the present invention;

fig. 2 is a flow chart of a motor speed measurement method based on a non-contact magnetic rotation position sensor according to the present invention.

Detailed Description

For a further understanding of the present invention, the present invention will be described in detail with reference to the drawings and examples.

Example 1

Referring to fig. 1, a motor rotation speed measuring device based on a non-contact magnetic rotation position sensor in this embodiment includes a power module, a main control chip, a magnetic rotation position sensor, a display screen, and a communication module. The magnetic rotary position sensor adopts a contactless rotary encoder SC60104, which is a system-on-chip integrated with integrated Hall element, analog front end and data processing functions inside a single chip. The chip provides 3 available incremental output modes including quadrature a/B output (quadrature a/B mode), LSB output (step/direction mode), pulse width modulated output, quadrature a/B being its default mode. The device uses the orthogonal A/B output mode, and does not need to be configured.

With respect to the installation of the magnetic rotational position sensor, the present embodiment installs a radially magnetized circular magnet having a diameter of 6mm in a non-magnetic circular bushing, and then fixes the bushing on the motor shaft while keeping the shaft center uniform. The center of the magnetic rotation position sensor and the center of the magnet are kept coaxial, and the error is within 0.485 mm. The distance between the surface of the magnet and the surface of the sensor is 2mm, and the distance can be properly adjusted according to the magnetic field intensity of the magnet.

The embodiment can use an external power supply or a lithium battery to supply power, and the power conversion chip is an RT6150AGQW. The power supply chip is a high-efficiency and fixed-frequency Buck-Boost DC/DC converter and can work under the condition that the input voltage is higher than, lower than or equal to the output voltage. The circuit topology integrated in the circuit can perform continuous voltage conversion work in various working modes, so that the circuit topology is very suitable for occasions of power supply of single lithium ion batteries, multiple alkaline batteries or nickel-hydrogen batteries, and the problem of voltage conversion of output voltage in a battery voltage interval is solved.

The main control chip adopts an AT32F403ACGT7 singlechip, and a single-precision floating point arithmetic unit (FPU) and a Digital Signal Processor (DSP) are integrated in the chip, so that the chip has abundant on-chip peripheral equipment and flexible clock control mechanism.

In order to complete long-distance data communication with an upper computer, the requirements of stability and reliability of an application site are met. The invention adopts RS485 communication and adopts an optical coupler isolation circuit to realize the function. The RS485 chip is MAX13487E, and the serial chips internally comprise a state machine and a receiving comparator. The driver and the receiver can be automatically enabled or disabled by configuring external hardware to keep the bus in a correct working state, so that the I/O pins of the singlechip are saved.

In the embodiment, the traditional method for collecting the pulse number is abandoned on the pulse signal collection, and the pulse signal voltage is collected instead. The traditional method for collecting the number of pulse signals is suitable for a low-resolution sensor (encoder), has low precision and cannot carry out software filtering. The embodiment collects pulse signal voltage, belongs to an analog quantity collection mode, can use high sampling rate, is applicable to a high-resolution sensor (encoder), and is high in precision.

In the embodiment, an ADC module in the AT32F403ACGT7 singlechip is used for collecting the voltage value of a pulse signal output by an A/B pin of a sensor chip. Meanwhile, in order to improve the precision, the original signal can be better recovered by using a high-resolution sensor and a high sampling frequency. And to better analyze the signal characteristics, the signal is time-domain to frequency-domain converted. The Fast Fourier Transform (FFT) algorithm has small calculated amount, can realize real-time processing of signals by combining high-speed hardware, has optimal performance, and the embodiment converts time domain signals into frequency domain signals and then converts the frequency value of pulses into the rotating speed of the motor through the Fast Fourier Transform (FFT) algorithm. The direction of motor rotation is distinguished by judging the A/B phase difference. The rotating speed and the rotating direction of the motor are displayed on a local OLED display screen in real time. And the communication can also be uploaded to an upper computer or a specific terminal through an RS-485 communication interface, and a Modbus-RTU protocol is adopted in communication.

Example 2

Referring to fig. 2, in the motor rotation speed measuring method based on the non-contact magnetic rotation position sensor of this embodiment, the pulse signal of the a-phase pin of the non-contact magnetic rotation position sensor is taken as an example, and the B-phase principle is the same. Firstly, a 10K word memory unit is defined in a RAM of the singlechip, and the 10K word memory unit is called a sampling buffer zone and is used for storing sampling point data of a voltage value of a pulse signal after AD conversion. The measurement procedure of this embodiment is as follows:

step one, an interrupt function of a singlechip pin is used for collecting pulse signals of an Index pin of a sensor (the pulse signals output by the Index pin are generated by one pulse signal generated by one rotation of a magnet arranged on a motor shaft, namely, one rotation of the motor), and recording a time interval delta T of two adjacent pulses, namely, the time spent by one rotation of the motor, namely, a rough speed value of the motor

And step two, according to the characteristics of the non-contact magnetic rotation position sensor, the magnet rotates for one circle, and the A-phase pin of the sensor outputs 256 pulse signals, namely the resolution ratio PPR of the sensor is 256. And (3) combining the rough motor speed value obtained in the step one, and further calculating to obtain the pulse frequency f=ppr×v output by the phase a pin of the sensor. Selecting an appropriate sampling frequency f _s ，f _s The phase a pin of the sensor outputs a pulse frequency f greater than 2 times. According to selectionSampling frequency f of choice _s The pulse signal output by the A-phase pin of the sensor is sampled with the analog voltage value, and the values of the sampling points are sequentially stored in a sampling buffer area according to the sampling time sequence.

It should be noted that, in view of the fact that the sampling accuracy is low at a low rotation speed of the motor, the variable sampling frequency method is adopted in the embodiment. Namely, when the motor rotates at a low speed, the low sampling frequency is automatically selected, and when the motor rotates at a high speed, the high sampling frequency is automatically selected. Therefore, on the premise of ensuring the signal integrity, the proper sampling point number can be selected to participate in the subsequent FFT operation, so that the memory overhead is saved, the running speed of the system is increased, and the precision at low speed can be improved. The implementation principle of the embodiment is that the number of pulse signals output by an Index pin of the sensor is calculated in real time, the motor rotation speed value is roughly calculated, and the proper sampling frequency is selected according to the rough value.

The Index pin of the sensor outputs a pulse signal every time the magnet is installed on the motor shaft. The Index pulse signal is acquired by utilizing the interrupt function of the AT32F403ACGT7 singlechip, and then the time interval of two adjacent pulse signals, namely the time used by one turn of motor rotation, can be simply and roughly calculated, and the method is simple but has practicability.

Step three, processing the sampled data of the pulse signal output by the A-phase pin of the sensor in real time, wherein the data is f _s The pulse signal voltage value output by the A-phase pin of the sensor, which is acquired by the sampling frequency, namely 2048 sampling point values are selected from the position of storing new sampling point values in the sampling buffer area, and the values stored in the buffer area are subjected to amplitude limiting filtering, so that some unreliable sampling point data are removed, the signal can be better restored, and the continuity and the integrity of the signal are ensured.

And fourthly, carrying out FFT conversion on the values of the 2048 sampling points, and converting the signals from the time domain to the frequency domain. The fast fourier transform is another method of solving the Discrete Fourier Transform (DFT), and the FFT algorithm classification includes: time extraction (DIT) and frequency extraction (DIF). The present embodiment selects the basis-2 FFT algorithm that is decimated by time.

And carrying out complex modular value operation on the FFT result, obtaining the amplitude of each point, and selecting a sequence n of points with the maximum amplitude. The pulse signal is a rectangular wave, also called a square wave, and is formed by superposing infinite sine waves for the square wave, wherein the first amplitude is the frequency of the square wave, namely the pulse signal frequency F of the phase A pin of the sensor. The calculation formula of the pulse signal frequency F of the phase A pin of the sensor is as follows:

wherein f _s Is the known sampling frequency, N is the number of sequences of maximum amplitude points, and N is the number of sampling points selected by the known participating transformation operation.

Fifthly, performing speed conversion according to the calculated pulse signal frequency F of the phase A pin of the sensor, wherein the conversion formula is as follows

Where the unit of velocity V' is RPS (revolutions per second), F is the pulse signal frequency of the a phase pin of the sensor, PPR is the resolution of the sensor, which in this embodiment is 256.

If the speed unit is to be converted to RPM, v=60×v', i.e.

The speed value is a motor rotation speed value with higher precision.

After FFT conversion, the sampling points can obtain the real part and the imaginary part of the amplitude of the corresponding frequency point. The phase is calculated as follows:

P _n ＝atan 2(b,a)

wherein: p (P) _n Is the phase radian value, rad; a is the real part of the frequency point; b is the imaginary part of the frequency point. And bringing the real part and the imaginary part of the maximum amplitude point into the formula to obtain the phase angle of the corresponding A/B phase.

The unit of the phase value calculated by the formula is radian rad, and the unit of the phase value needs to be converted into an angle value, and the conversion formula is as follows:

wherein: θ _n Is the phase angle value, °; p (P) _n Is the phase radian value, rad.

The motor rotation direction judging formula is as follows:

Δθ＝θ _A -θ _B

wherein: delta theta is the phase difference, °; θ _A Is the phase angle value, °; θ _B Is the phase angle value, °.

When Δθ=90°, i.e., the phase of the a-channel leads the phase of the B-channel by 90 °, the motor (magnet) rotates clockwise; when Δθ= -90 °, i.e. the phase of the B-channel leads the phase of the a-channel by 90 °, the motor rotates in the counter-clockwise direction.

The invention and its embodiments have been described above by way of illustration and not limitation, and the invention is illustrated in the accompanying drawings and described in the drawings in which the actual structure is not limited thereto. Therefore, if one of ordinary skill in the art is informed by this disclosure, the structural mode and the embodiments similar to the technical scheme are not creatively designed without departing from the gist of the present invention.

Claims

1. A motor rotating speed measuring method based on a non-contact magnetic rotation position sensor is characterized by comprising the following steps:

step two, combining the rough speed value of the motor to obtain pulse frequency, and selecting sampling frequency based on the pulse frequency;

performing FFT (fast Fourier transform) on the data processed in the step three, performing complex modular value operation on the transformation result, obtaining the amplitude of each point, selecting a sequence n of points with the maximum amplitude, and obtaining the frequency F of the pulse signal based on the sequence number;

and fifthly, performing speed conversion according to the pulse signal frequency F to obtain a motor rotation speed value.

2. The method for measuring the motor rotation speed based on the non-contact magnetic rotation position sensor according to claim 1, wherein the method comprises the following steps: in the first step, radial magnetized circular magnets of a magnetic rotary position sensor are arranged in a non-magnetic circular bushing, and the bushing is fixed on a motor shaft and keeps the axle center consistent; the magnet is arranged on the motor shaft, a pulse signal is output every time the magnet rotates for one circle, the Index pin of the magnetic rotation position sensor acquires the pulse signal, the interrupt function of the singlechip pin is used for acquiring the pulse signal of the Index pin of the sensor, the time interval delta T of two adjacent pulses is recorded, and then the rough speed value of the motor is obtained

3. A method for measuring the rotational speed of a motor based on a non-contact magnetic rotational position sensor as claimed in claim 2, wherein: in the second step, firstly, determining the resolution PPR of the magnetic rotation position sensor, combining the rough speed value of the motor to obtain the pulse frequency f=ppr×v, and selecting the pulse frequency f which is more than 2 times as the sampling frequency f _s 。

4. A method of measuring motor speed based on a non-contact magnetic rotational position sensor as defined in claim 3, wherein: and thirdly, sequentially storing the acquired pulse signal voltage values into a sampling buffer area according to a sampling time sequence, and selecting 2048 sampling point values forwards from the sampling buffer area in real time by taking the position storing the current sampling point value as a starting point, and performing amplitude limiting filtering.

5. The method for measuring the motor rotation speed based on the non-contact magnetic rotation position sensor according to claim 4, wherein the method comprises the following steps: in the fourth step, the calculation formula of the pulse signal frequency F is:

wherein f _s For sampling frequency, N is the number of sequences of the maximum points of amplitude, and N is the number of sampling points selected by the known conversion operation.

6. The method for measuring the motor rotation speed based on the non-contact magnetic rotation position sensor according to claim 5, wherein the method comprises the following steps: and fifthly, dividing the pulse signal frequency F by the resolution of the sensor, and converting to obtain a motor rotating speed value.

7. The method for measuring the motor rotation speed based on the non-contact magnetic rotation position sensor according to claim 6, wherein the method comprises the following steps: after FFT conversion, the sampling data obtain real and imaginary parts of corresponding frequency point amplitude, and based on the real and imaginary parts, the phase angle of corresponding A/B phase is obtained, and the rotation direction of the motor is judged according to the phase angle.

8. The method for measuring the motor rotation speed based on the non-contact magnetic rotation position sensor according to claim 7, wherein the method comprises the following steps: and step four, converting the signal from the time domain to the frequency domain by using a time-decimated base-2 FFT algorithm.

9. A motor rotation speed measuring device based on non-contact magnetic rotation position sensor is characterized in that: the apparatus performs the motor rotation speed measurement method according to any one of claims 1 to 8.

10. A motor speed measurement device based on a non-contact magnetic rotational position sensor as claimed in claim 9, wherein: the magnetic rotation position sensor adopts a non-contact rotary encoder SC60104 and uses an orthogonal A/B output mode thereof; the main control chip adopts an AT32F403ACGT7 singlechip, an ADC module in the singlechip collects the voltage value of a pulse signal output by an A/B pin of the sensor chip; the rotating speed and the rotating direction of the motor are displayed on a display screen in real time, the singlechip is communicated with the upper computer or the specific terminal through the RS-485 communication interface, and the power supply module supplies power by using an external power supply or a lithium battery.