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 (computed tomography) machine based on a magnetic ring and Hall sensors. The method comprises the following steps that: when the hub motor of the CT machine operates, linear Hall sensors detect a position detection ring driven by a rotor of the hub motor of the CT machine, and electromagnetic induction is generated between the linear Hall sensors and the position detection ring so as to generate a Hall potential, wherein the linear Hall sensors comprise an absolute position sensor and a relative position sensor; the measured Hall potential and a normalized value are compared in a comparator, then a comparison result is outputted, and whether the hub motor of the CT machine runs to an accurate position is judged according to the comparison result; and when the hub motor of the CT machine starts up, the absolute position sensor enters into a detection state after carrying out positioning and rotating speed control on the initial position of the motor, and the relative position sensor controls the current phase change of the motor. By using the method provided by the invention, the influence of position errors caused by magnetic asymmetry and magnetic field intensity problems generated in the manufacturing and operating processes of a magnetic steel of the hub motor of the CT machine is greatly weakened, thereby improving the position precision of the motor.

Description

The method for detecting position of the CT wheel hub motor based on magnet ring and Hall element

Technical field

The present invention relates to motor position and detect applied technical field, particularly relate to a kind of method for detecting position of the CT wheel hub motor based on magnet ring and Hall element.

Background technology

Along with industrial develop rapidly, more and more higher to the position detection accuracy requirement of machine operation.At present, on position probing, application is wider coding type transducer, grating sensor, a magnetic induction sensor etc., but because Costco Wholesale is high, the external interference impact is large, manufacture, mounting process require high factor, simultaneously, and in motor operation course, due to motor manufacture and work in the magnetic field intensity that exists excessive or too small, magnetic is asymmetric etc. cause motor position inaccurate, sensitivity is low etc., detects to the motor exact position and rotating speed control has brought great challenge.

The CT machine in running to the On-line Control of its motor speed and position, be guarantee the CT machine can imaging clearly when doing diagnosis to the patient, accurately, avoid occurring the mistaken diagnosis phenomenon.

In the CT machine course of work, rotary speed is extremely important and must a consider technological parameter, the precision of rotating speed and the stable correctness of CT machine imaging and the accuracy of judgement pathology of being directly connected to, therefore when the CT machine is worked, to accurate measurement and the control of wheel hub motor rotating speed on the CT machine, seem particularly important.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of method for detecting position of the CT wheel hub motor based on magnet ring and Hall element, can be more accurately, more delicately CT machine motor position and rotating speed thereof are detected.

The technical solution adopted for the present invention to solve the technical problems is: the method for detecting position that a kind of CT wheel hub motor based on magnet ring and Hall element is provided, comprise Hall element and position probing ring, described Hall element is linear hall sensor, and described position probing ring and CT wheel hub rotor fix; Described method for detecting position comprises the following steps: CT wheel hub motor is in service, the position probing ring that linear hall sensor drives CT wheel hub rotor is detected, be divided into absolute position transducer and relative position sensor, and electromagnetic induction occurs with it, 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, and relative position sensor is controlled the current of electric commutation.

Described Hall element is linear hall sensor, is divided into absolute position transducer and relative position sensor, and the relative position sensor of three commutator effects is separated by 120 ° and is placed, and absolute position transducer aligns with initial position.

Described position probing ring is absolute position detection ring and relative position detection ring, and relative position detection ring positional precision as requested magnetizes as corresponding number of pole-pairs, and wherein the absolute position detection ring only has a pair of magnetic pole.

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, be loaded in advance in the comparator of corresponding standard value, 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.

Described absolute position transducer, by the detection to the absolute position detection ring, changes and causes the change of 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.

beneficial effect

The present invention, owing to having adopted above-mentioned technical scheme, compared with prior art has following advantage and good effect: the present invention relatively locates and detects motor speed by the numerical value of linear hall sensor and position probing ring electromagnetic induction generation Hall voltage with standard value.By the standard value recorded in advance and the comparison of surveying the Hall voltage value, guaranteed that position signalling is consistent with absolute fix, weakened greatly motor manufacture and work in the magnetic field intensity that exists excessive or too small, magnetic is asymmetric etc. cause motor position inaccurate, sensitivity is low etc.After motor operates in detected state, Motor Rotating Speed Control System will be revised by each rotating speed turned motor, in order to avoid the CT machine rotating speed deviation occurs when operation, causes imaging inaccurate.Therefore, there is control precision by the CT wheel hub motor high precision position detection method based on magnet ring and Hall element high, fast response time, the characteristics such as stability is strong.

The accompanying drawing explanation

Fig. 1 is that motor position of the present invention detects schematic diagram;

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

Embodiment

Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiment only are not used in and limit the scope of the invention for the present invention is described.Should be understood that in addition those skilled in the art can make various changes or modifications the present invention after the content of having read the present invention's instruction, these equivalent form of values fall within the application's appended claims limited range equally.

As shown in Figure 1-2, the present invention relates to a kind of method for detecting position of the CT wheel hub motor based on magnet ring and Hall element, the method is realized by the high precision position detection device of position probing ring and Hall element.Comprise Hall element and position probing ring, described Hall element is linear hall sensor, and described position probing ring and CT wheel hub rotor fix; Comprise the following steps: CT wheel hub motor is in service, and the position probing ring that linear hall sensor drives CT wheel hub rotor is detected, and is divided into absolute position transducer and relative position sensor, and electromagnetic induction occurs with it, produces 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, and relative position sensor is controlled the current of electric commutation.After the present invention adopts the method to detect, weakened greatly the impact of the site error that magnetic is asymmetric, the magnetic field intensity problem causes produced due to the dynamo-electric machine magnet steel of CT in manufacturing and working, improve the positional precision of motor, but need to carry out the Hall voltage detection to the position detection ring in advance.

Its concrete steps comprise:

(1) mounted motor position probing ring on the rotor of wheel hub motor, and corresponding position transducer is installed on frame;

(2) by the measuring of motor position detection ring accurate location Hall voltage, be stored in the memory data storehouse of digital signal processor (DSP);

(3) start the CT machine, load appropriate numerical value in comparator, control the motor simple operation;

(4) position transducer detects electromagnetic signal, and the absolute position detection ring is detected, and changes and causes the change of 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 the CT machine rotor, whether reaches initial position; If reach position location, according to the position of rotor in motor operation course in advance standard value be loaded into corresponding standard value and accurately move to controlling motor in comparator; If reach position location and rotating speed requirement start to enter next step, the CT machine starts to enter detected state, otherwise CT wheel hub motor continues to move and keep detected state to wait for;

(5) Hall voltage that the relative position sensor of control electric current commutation obtains by detection and standard value are relatively, calculate the mechanical angle that CT machine rotor relative positioning position turns over, and judge in the error range whether CT machine rotating speed and angular displacement allow at the CT machine, if would enter next step, otherwise keep detected state;

(6) Motor Rotating Speed Control System is controlled motor speed, in the speed error scope that its stabilization of speed is allowed at the CT machine.

Take angular displacement absolute measurement precision as ± 1 ' CT wheel hub motor be example, according to the electromechanics angular displacement, meet:

$\mathrm{\ψ}=\frac{\mathrm{\θ}}{6}=\frac{\mathrm{\α}}{6\·p}$

ε＝ψ·ρ

ε′＝K·ε

Wherein, ψ is that the corresponding comparator signal of relative position sensor changes corresponding mechanical angle displacement, θ is the mechanical angle displacement that the corresponding comparator of relative position sensor signal changes one-period, α is electrical degree, p is relative position detection ring number of pole-pairs, and ρ is the linear hall sensor control precision, and ε is the theoretical position precision, ε ' is the physical location precision, and K is coefficient of safety.

Linear hall sensor meets:

U＝KIB

$K=\frac{R}{d}$

Wherein, U is Hall voltage, the sensitivity that K is the Hall material, and B is that institute's location is put magnet ring magnetic flux density, and I is current strength, and R is Hall coefficient, the thickness that d is the Hall material.

To ask for K=2 according to Practical Project, ρ=1%, in ε '=1 ' time, calculating and answering power taking machine number of pole-pairs is 72 pairs.Visible, on the basis do not promoted in the transducer control precision, relative position detection ring number of pole-pairs is more, and the angular displacement precision of motor is also just higher; The Hall voltage that now adopts the linear hall sensor detection to obtain and standard value relatively, have improved the control precision of linear hall sensor, therefore the angular displacement precision of motor significantly improves.After rotor rotates a circle, can utilize the relation between CT wheel hub motor absolute position detection ring and absolute position transducer to adjust angular displacement and the speed of motor by closed-loop control, improved greatly the positional precision of CT wheel hub motor.

Be not difficult to find, with existing detection method, compare, the maximum characteristics of the present invention are the standard values and the comparison of surveying the Hall voltage value by recording in advance, guaranteed that position signalling is consistent with absolute fix, weakened greatly motor manufacture and work in the magnetic field intensity that exists excessive or too small, magnetic is asymmetric etc. cause motor position inaccurate, sensitivity is low etc.; Can detect each rotating speed turned of wheel hub motor on the CT machine, and the rotating speed in time each turned by Motor Rotating Speed Control System is revised, guarantee that each rotating speed turned of wheel hub motor can be in the error range of predetermined set, thereby guaranteed the accuracy of CT machine imaging, therefore, being used on CT wheel hub motor outer shroud the detection method that absolute position transducer is installed, to have control precision high, fast response time, the characteristics such as stability is strong.

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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