CN102355182B - Method for detecting position of hub motor of CT (computed tomography) machine based on magnetic ring and Hall sensors - Google Patents

Abstract

The invention relates to a method for detecting the position of a hub motor of a CT machine based on a magnetic ring and a Hall sensor. , divided into absolute position sensor and relative position sensor, and electromagnetic induction occurs with it to generate Hall potential; the measured Hall potential is compared with the standard value in the comparator, and the comparison result is output, and the CT is judged by the comparison result Whether the wheel hub motor of the CT machine runs to an accurate position; when the hub motor of the CT machine starts, the absolute position sensor locates the initial position of the motor and enters the detection state after controlling the speed, and the relative position sensor controls the motor current commutation. The invention greatly weakens the influence of the position error caused by the magnetic asymmetry and magnetic field strength problems of the magnet steel of the CT motor during manufacture and operation, and improves the position accuracy of the motor.

Description

Position detection method of hub motor of CT machine based on magnetic ring and Hall sensor

technical field

The invention relates to the technical field of motor position detection applications, in particular to a method for detecting the position of a hub motor of a CT machine based on a magnetic ring and a Hall sensor.

Background technique

With the rapid development of industrial production, the requirements for the position detection accuracy of motor work are getting higher and higher. At present, encoder sensors, grating sensors, magnetic grid sensors, etc. are widely used in position detection. However, due to the high price and cost, the influence of external interference, and the high requirements for manufacturing and installation processes, at the same time, during the operation of the motor, Due to the inaccurate position and low sensitivity of the motor caused by the excessive or small magnetic field strength and magnetic asymmetry in the manufacture and operation of the motor, it has brought great challenges to the precise position detection and speed control of the motor.

The on-line control of the motor speed and position of the CT machine during operation is to ensure that the CT machine can image clearly and accurately when diagnosing patients, and avoid misdiagnosis.

During the working process of the CT machine, the rotational speed is a very important process parameter that must be considered. The accuracy and stability of the rotational speed are directly related to the correctness of the imaging of the CT machine and the accuracy of judging the pathology. Therefore, when the CT machine is working, the CT The precise measurement and control of the speed of the wheel hub motor on the machine is particularly important.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for detecting the position of the hub motor of a CT machine based on a magnetic ring and a Hall sensor, which can detect the position and speed of the CT machine motor more accurately and sensitively.

The technical solution adopted by the present invention to solve the technical problem is: to provide a position detection method of a CT hub motor based on a magnetic ring and a Hall sensor, including a Hall sensor and a position detection ring, and the Hall sensor is a linear Hall sensor. Hall sensor, the position detection ring is fixed with the rotor of the hub motor of the CT machine; the position detection method includes the following steps: during the operation of the hub motor of the CT machine, the linear Hall sensor detects the position of the position detection ring driven by the rotor of the hub motor of the CT machine Detection is divided into absolute position sensor and relative position sensor, and electromagnetic induction occurs with it to generate Hall potential; the measured Hall potential is compared with the standard value in the comparator, and the comparison result is output, and the comparison result is judged Whether the hub motor of the CT machine runs to the correct position; when the hub motor of the CT machine starts, the absolute position sensor locates the initial position of the motor and enters the detection state after controlling the speed, and the relative position sensor controls the motor current commutation.

The Hall sensor is a linear Hall sensor, which is divided into an absolute position sensor and a relative position sensor. The relative position sensors acting on the three commutators are placed 120° apart, and the absolute position sensors are aligned with the initial position.

The position detection ring is an absolute position detection ring and a relative position detection ring. The relative position detection ring is magnetized to correspond to the number of pole pairs according to the required position accuracy, and the absolute position detection ring has only one pair of magnetic poles.

The standard value is obtained by measuring the Hall potential of the accurate position of the motor position detection ring, stored in the memory database of the digital signal processor DSP, and preloaded to the corresponding standard value according to the position of the motor rotor during the operation of the motor. In the comparator, it is compared with the Hall potential measured by the position detection ring, and the digital signal processor DSP judges whether the motor has reached the accurate position through the signal output by the comparator.

The absolute position sensor detects the absolute position detection ring, and changes the hall potential through the transition from magnetic pole N to S, thereby causing a jump in the output value of the comparator to determine the initial position of the rotor of the CT machine.

Beneficial effect

Compared with the prior art, the present invention has the following advantages and positive effects due to the adoption of the above-mentioned technical scheme: the present invention locates by comparing the numerical value of the Hall potential generated by the linear Hall sensor and the position detection ring electromagnetic induction with the standard value and detect the motor speed. By comparing the pre-measured standard value with the measured Hall potential value, it is ensured that the position signal is consistent with the measured position, which greatly weakens the excessive or too small magnetic field strength, magnetic asymmetry, etc. Cause inaccurate motor position, low sensitivity, etc. After the motor runs in the detection state, the motor speed control system will correct the speed of each revolution of the motor, so as to avoid the deviation of the speed of the CT machine during operation, resulting in inaccurate imaging. Therefore, the high-precision position detection method of the hub motor of the CT machine based on the magnetic ring and the Hall sensor has the characteristics of high control precision, fast response speed, and strong stability.

Description of drawings

Fig. 1 is a schematic diagram of motor position detection of the present invention;

Fig. 2 is a layout diagram of the motor position of the present invention.

Detailed ways

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

As shown in Figures 1-2, the present invention relates to a position detection method of a hub motor of a CT machine based on a magnetic ring and a Hall sensor. The method is realized by a high-precision position detection device of a position detection ring and a Hall sensor. It includes a Hall sensor and a position detection ring, the Hall sensor is a linear Hall sensor, and the position detection ring is fixed to the rotor of the hub motor of the CT machine; it includes the following steps: when the hub motor of the CT machine is running, the linear Hall sensor The position detection ring driven by the rotor of the hub motor of the CT machine is detected, which is divided into an absolute position sensor and a relative position sensor, and electromagnetic induction occurs with it to generate a Hall potential; the measured Hall potential and the standard value are compared in a comparator Compare, output the comparison result, and judge whether the hub motor of the CT machine runs to the correct position through the comparison result; when the hub motor of the CT machine starts, the absolute position sensor will locate the initial position of the motor and enter the detection state after the speed control, and the relative position sensor will control Motor current commutation. After the present invention adopts this method to detect, it greatly weakens the influence of the position error caused by the magnetic asymmetry and magnetic field strength problems caused by the magnetic steel of the CT machine motor during manufacture and work, and improves the position accuracy of the motor. Hall potential detection is performed on the position detection loop.

Its specific steps include:

(1) Install the motor position detection ring on the rotor of the hub motor, and install the corresponding position sensor on the frame;

(2) Obtained by measuring the Hall potential of the accurate position of the motor position detection ring, and stored in the memory database of the digital signal processor (DSP);

(3) Start the CT machine, load the appropriate value in the comparator, and control the simple operation of the motor;

(4) The position sensor detects the electromagnetic signal, detects the absolute position detection ring, and changes the Hall potential through the transition from the N pole to the S pole, thereby causing a jump in the output value of the comparator to determine whether the rotor of the CT machine has reached the initial state. position; if the positioning position is reached, load the corresponding standard value into the comparator according to the pre-standard value of the position of the motor rotor during the operation of the motor to control the motor to run accurately; if the positioning position and speed requirements are reached, then enter the next step, CT The machine starts to enter the detection state, otherwise the hub motor of the CT machine continues to run and remains in the detection state to wait;

(5) The relative position sensor that controls the current commutation compares the detected Hall potential with the standard value, calculates the mechanical angle that the rotor of the CT machine rotates relative to the positioning position, and judges whether the rotation speed and angular displacement of the CT machine are within the range of the CT machine. Within the allowable error range, if it is, enter the next step, otherwise keep the detection state;

(6) The motor speed control system controls the motor speed so that its speed is stable within the allowable speed error range of the CT machine.

Taking the hub motor of a CT machine with an absolute measurement accuracy of ±1′ as an example, the mechanical angular displacement of the motor satisfies:

$\mathrm{<span\; class="notranslate">\; \&psi;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; p</span>}}$

ε=ψ·ρ

ε'=K·ε

Among them, ψ is the mechanical angular displacement corresponding to the signal change of the relative position sensor corresponding to the comparator, θ is the mechanical angular displacement of the relative position sensor signal corresponding to one cycle of the comparator change, α is the electrical angle, and p is the number of pole pairs of the relative position detection ring, ρ is the control accuracy of the linear Hall sensor, ε is the theoretical position accuracy, ε' is the actual position accuracy, and K is the safety factor.

Linear Hall sensors meet:

U=KIB

$\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; R</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}$

Among them, U is the Hall potential, K is the sensitivity of the Hall material, B is the magnetic induction intensity of the magnetic ring at the measured position, I is the current intensity, R is the Hall coefficient, and d is the thickness of the Hall material.

According to the actual engineering requirements, when K=2, ρ=1%, and ε'=1', the calculated number of motor pole pairs should be 72 pairs. It can be seen that, on the basis of not improving the control accuracy of the sensor, the more pole pairs of the relative position detection ring, the higher the angular displacement accuracy of the motor; the Hall potential obtained by the linear Hall sensor is compared with the standard value, and the improvement The control accuracy of the linear Hall sensor is improved, so the angular displacement accuracy of the motor is significantly improved. After the rotor of the motor rotates once, the angular displacement and speed of the motor can be adjusted through closed-loop control by using the relationship between the absolute position detection ring and the absolute position sensor of the hub motor of the CT machine, which greatly improves the position accuracy of the hub motor of the CT machine.

It is not difficult to find that compared with the existing detection methods, the biggest feature of the present invention is that the comparison between the pre-measured standard value and the measured Hall potential value ensures that the position signal is consistent with the measured position, which greatly weakens the motor's In manufacturing and working, the magnetic field strength is too large or too small, magnetic asymmetry, etc. cause inaccurate motor position, low sensitivity, etc.; can detect the rotation speed of the wheel hub motor on the CT machine, and timely monitor each rotation speed through the motor speed control system. The speed of one revolution is corrected to ensure that the speed of each revolution of the hub motor can be within the predetermined error range, thereby ensuring the accuracy of CT imaging. Therefore, it is used to install an absolute position sensor on the outer ring of the hub motor of the CT machine The detection method has the characteristics of high control precision, fast response speed and strong stability.

Claims (3)

1. the method for detecting position of the CT wheel hub motor based on magnet ring and Hall element, comprise Hall element and position probing ring, described Hall element is linear hall sensor, be divided into absolute position transducer and relative position sensor, described position probing ring and CT wheel hub rotor fix, described position probing ring is divided into absolute position detection ring and relative position detection ring, and wherein, the absolute position detection ring only has a pair of magnetic pole; It is characterized in that, described method for detecting position comprises the following steps: CT wheel hub motor is in service, linear hall sensor is detected the position probing ring on CT wheel hub rotor, and described position probing ring and linear hall sensor generation electromagnetic induction produce Hall voltage; Measured Hall voltage and standard value compare in comparator, and the output comparative result, judge CT wheel hub motor by comparative result and whether run to accurate location; During CT wheel hub electric motor starting, absolute position transducer positions the initial position of motor and rotating speed enters detected state after controlling, relative position sensor is controlled the current of electric commutation, wherein three relative position sensors that play the commutator effect are separated by 120 ° and are placed, and described absolute position transducer aligns with initial position.

2. the method for detecting position of the CT wheel hub motor based on magnet ring and Hall element according to claim 1, it is characterized in that, described standard value is by measuring motor position detection ring accurate location Hall voltage, be stored in the memory data storehouse of digital signal processor DSP, according to the position of rotor in motor operation course, in advance corresponding standard value is loaded in comparator, then with position probing ring actual measurement Hall voltage, compare, the signal that digital signal processor DSP is exported by comparator judges whether motor arrives accurate location.

3. the method for detecting position of the CT wheel hub motor based on magnet ring and Hall element according to claim 1, it is characterized in that, described absolute position transducer is by the detection to the absolute position detection ring, change the change that causes Hall voltage to the S utmost point by the magnetic pole N utmost point, thereby cause the saltus step of comparator output valve, to determine CT machine rotor initial position.

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