CN103731077B - The checkout gear of motor rotor position and rotating speed and method - Google Patents

Abstract

The invention provides the checkout gear of a kind of motor rotor position and rotating speed, comprise the position transducer rotor be fixedly installed in the rotating shaft of rotor, described position transducer rotor comprises the permanent magnet that can produce sine space magnetic field, described checkout gear also comprises 3 linear hall elements for detecting described sine space magnetic field be arranged on motor stator, each described linear hall element with the mode of mutual deviation 120 degree of electrical degrees be distributed in the plane vertical with described rotating shaft with described rotating shaft for the center of circle circumferentially.Present invention also offers the detection method of a kind of motor rotor position and rotating speed, the magnitude relationship of the magnitude of voltage exported according to 3 linear hall elements judges current which the electrical degree interval be in the electrical degree cycle, then according to described magnitude of voltage and described electrical degree interval computation the position of rotor.The present invention can low cost and high accuracy, the position realizing rotor with high reliability and velocity measuring.

Description

Device and method for detecting position and rotating speed of motor rotor

Technical Field

The invention relates to the field of motor detection, in particular to a device and a method for detecting the position and the rotating speed of a motor rotor.

Background

At present, electric bicycles, self-balancing electric bicycles, unicycles with a balancing function, electric automobiles and the like all use motors as main power output devices, and the cost of the application fields is low, but the requirements on the precision and the reliability of a motor rotor position sensor are high.

In the prior art, a position detection device of a permanent magnet brushless dc motor includes: discrete hall sensors, photoelectric encoders, and rotary transformers. The discrete Hall sensor provides six positions in one electrical angle period, the position precision is low, and by adopting the position detection device, the motor has large torque pulsation and low speed calculation precision. Although the photoelectric encoder has high position precision, the photoelectric encoder is expensive and greatly influenced by application environment, and is not suitable for the field of electric vehicles with high reliability requirements and low cost. The reliability and the position detection precision of the rotary transformer are high, but the rotary transformer is expensive, the decoding algorithm is complex, a hardware chip is required to be adopted for decoding, and although the circuit is simple, the decoding chip is expensive.

Disclosure of Invention

The invention aims to provide a device and a method for detecting the position and the rotating speed of a motor rotor, which have low cost, high precision and high reliability.

The invention provides a detection device for the position and the rotating speed of a motor rotor, which comprises a position sensor rotor fixedly arranged on a rotating shaft of the motor rotor, wherein the position sensor rotor comprises a permanent magnet capable of generating a sinusoidal space magnetic field, the detection device also comprises 3 linear Hall elements arranged on a motor stator and used for detecting the sinusoidal space magnetic field, and the linear Hall elements are distributed on a circumference which takes the rotating shaft as a circle center on a plane vertical to the rotating shaft in a mode of mutually differing 120-degree electrical angles.

Further, the radius of the circumference is a value that enables the magnetic field strength detected by the linear hall element to be less than the maximum magnetic field strength that it can sense and greater than a predetermined value.

Preferably, the permanent magnet has two opposite poles.

Preferably, the permanent magnet is four tile type neodymium iron boron magnetic steels with alternately distributed magnetic poles.

The invention also provides a detection method of the position and the rotating speed of the motor rotor based on the detection device of the position and the rotating speed of the motor rotor, which is characterized in that which electric angle interval is currently positioned in the electric angle cycle is judged according to the magnitude relation among a first voltage value, a second voltage value and a third voltage value respectively output by a first linear Hall element, a second linear Hall element and a third linear Hall element which are sequentially and adjacently arranged in the 3 linear Hall elements, and then the position of the motor rotor is calculated according to the voltage values and the electric angle intervals.

Further, the determining which electrical angle interval in the electrical angle cycle currently includes: when the second voltage value is smaller than or equal to the first voltage value and the first voltage value is smaller than the third voltage value, the electrical angle interval is a first interval; when the second voltage value is smaller than or equal to the third voltage value and the third voltage value is smaller than the first voltage value, the electrical angle interval is a second interval; when the third voltage value is less than or equal to the second voltage value and the second voltage value is less than the first voltage value, the electrical angle interval is a third interval; when the third voltage value is less than or equal to the first voltage value and the first voltage value is less than the second voltage value, the electrical angle interval is a fourth interval; when the first voltage value is smaller than or equal to the third voltage value and the third voltage value is smaller than the second voltage value, the electrical angle interval is a fifth interval; and when the first voltage value is smaller than or equal to the second voltage value and the second voltage value is smaller than the third voltage value, the electrical angle interval is a sixth interval.

Preferably, the position θ of the rotor of the motor is calculated according to the following formula_e：

θ_e=θ_x+K·V_eWherein, theta_xIs the electric angle intervalThe initial position of (a) is as follows:

k is the reciprocal of the voltage value corresponding to the maximum magnetic field intensity detected by the linear Hall element, V_eThe effective voltage value in the electrical angle interval is as follows:

preferably, the position θ of the rotor of the motor is calculated according to the following formula_e：

θ_e=θ_x+arcsin(K·V_e) Wherein, theta_xThe values of the initial position of the electrical angle interval are as follows:

k is the reciprocal of the voltage value corresponding to the maximum magnetic field intensity detected by the linear Hall element, V_eThe effective voltage value in the electrical angle interval is as follows:

further, the method also comprises the step of calculating the rotating speed of the motor rotor according to the positions of more than two motor rotors.

Preferably, the rotor position θ at time k-1 is calculated_e,k-1And rotor position θ at time k_e,kThe time difference between the k-1 moment and the k moment is T, and the rotating speed n of the motor rotor is calculated according to the following formula_k：

Wherein p is the number of pole pairs of the permanent magnet of the position sensor rotor.

The detection device for the position and the rotating speed of the motor rotor adopts the linear Hall element as a detection device, so that the device cost is reduced, the manufacturing process is simplified and the reliability is improved compared with the detection device in the prior art; the detection method based on the device decodes the voltage output by the linear Hall element through software, and greatly improves the detection precision of the position and the speed of the rotor.

Drawings

FIG. 1 is a schematic view of a preferred embodiment of the apparatus for detecting rotor position and rotational speed of an electric machine of the present invention;

FIG. 2 is a schematic view of the permanent magnets of the position sensor rotor of the preferred embodiment of the apparatus for detecting position and rotational speed of a motor rotor of the present invention;

FIG. 3 is a schematic view of the base of the position sensor rotor of the preferred embodiment of the apparatus for detecting the position and rotational speed of a motor rotor of the present invention;

FIG. 4 is a graph of voltage waveforms output by linear Hall elements of a preferred embodiment of the apparatus for detecting position and rotational speed of a motor rotor of the present invention;

FIG. 5 is a flow chart of a preferred embodiment of the method of detecting the position and rotational speed of a rotor of an electric machine of the present invention;

FIG. 6 is a schematic electrical angle range diagram of a preferred embodiment of the method for detecting the position and rotational speed of a rotor of an electric machine according to the present invention;

fig. 7 is a schematic view of a curve approximation of a preferred embodiment of the method of detecting the position and the rotation speed of the rotor of the electric machine of the present invention.

Description of reference numerals:

1 position sensor rotor 2 motor stator

31 first linear hall element 32 second linear hall element

33 third linear hall element 4 base

Detailed Description

The following describes the device and method for detecting the position and the rotation speed of the rotor of the motor in further detail with reference to the accompanying drawings and the detailed description, but the invention is not limited thereto.

Referring to fig. 1, a schematic diagram of a preferred embodiment of the device for detecting the position and the rotation speed of the rotor of the motor is shown. In this embodiment, the motor is a two-pole brushless dc motor. The detection device comprises a position sensor rotor 1 fixedly arranged on a rotating shaft of the motor rotor, and 3 linear Hall elements 31, 32 and 33 arranged on a motor stator 2 and used for detecting a sinusoidal space magnetic field of the position sensor rotor 1.

The position sensor rotor 1 comprises a permanent magnet capable of generating a sinusoidal spatial magnetic field, which, with reference to fig. 2, has two opposite poles, preferably four pieces of tile-like neodymium-iron-boron-steel magnets with alternating magnetic poles. The permanent magnet adopts a radial parallel magnetizing mode shown by an arrow in figure 2, the magnetizing mode is simple, and the structural design and the magnetizing mode of the permanent magnet ensure that the magnetic field space of the position sensor rotor 1 is in sinusoidal distribution. The position sensor rotor 1 further comprises a base 4 fixedly arranged on the rotating shaft of the motor rotor, as shown in fig. 3. The permanent magnet and the base 4 are fixed in a bonding mode and the like, and are matched with each other through the wedge-shaped groove, as shown in figure 1, the permanent magnet and the base 4 are firmly fixed when the motor runs at a high speed.

As shown in fig. 1, in this embodiment, 3 linear hall elements 31, 32, 33 are distributed on a circle centered on the rotation shaft on a plane perpendicular to the rotation shaft with a mutual difference of 120 degrees in electrical angle. Preferably, the linear hall element is a SS495A element from Honiwell corporation. The 3 linear hall elements are a first linear hall element 31, a second linear hall element 32, and a third linear hall element 33 which are adjacently arranged in this order. In the preferred embodiment, with continued reference to fig. 1, the angle between the line connecting the center and the center of the first linear hall element 31 and the line connecting the center and the center of the second linear hall element 32 is 60 degrees mechanical angle, and the angle between the line connecting the center and the center of the third linear hall element 33 and the line connecting the center and the center of the second linear hall element 32 is also 60 degrees mechanical angle.

Since the position sensor rotor 1 in this embodiment has two opposite poles, and the electrical angle thereof when rotated one cycle is 720 degrees, the electrical angles between the first linear hall element 31 and the second linear hall element 32, and between the second linear hall element 32 and the third linear hall element 33, which differ by a mechanical angle of 60 degrees, differ by 120 degrees. Meanwhile, since the mechanical angle between the first and third linear hall elements 31 and 33 is different by 180+60 degrees, the electrical angle thereof is different by 360+120 degrees, i.e., the electrical angle between the first and third linear hall elements 31 and 33 is different by 120 degrees. Therefore, in this embodiment, 3 linear hall elements are different from each other by 120 degrees in electrical angle.

When the motor is rotated, the waveforms of the output voltages of the 3 linear hall elements 31, 32, 33 are as shown in fig. 4, where V is_maxIs the voltage value output when the maximum magnetic field intensity is detected. Wherein V₁、V₂、V₃The output voltages of the first linear hall element 31, the second linear hall element 32, and the third linear hall element 33 are respectively.

The amplitude of the voltage signal is determined by the magnetism of the permanent magnet and the spatial position of the linear hall element. The distance from the linear Hall element to the circle center is the selection of the radius of the circumference, so that the magnetic field is ensured to induce a voltage which is large enough at the linear Hall element to ensure the sampling precision of the voltage, and the magnetic field at the position is ensured to be smaller than the maximum magnetic field value which can be induced by the linear Hall element to avoid saturation. This embodiment modeThe maximum magnetic field intensity sensed by the linear Hall element SS495A is +/-800 gauss, the corresponding output voltage is +/-2V, and the placement position, namely the circumference radius, of the linear Hall element is preferably selected so that the voltage corresponding to the maximum magnetic field sensed by the linear Hall element is 1.8V, namely V_max=1.8V。

From the waveform shown in fig. 4, a 360 degree electrical angle cycle can be divided into 6 intervals I-VI, as shown in fig. 6, each interval and its specific division criteria are shown in the first and second columns of table 1:

TABLE 1 Electrical Angle Range and characteristics thereof

First interval I	V2≤V1<V3	V1=Vmaxsinθ
			Second interval II	V2≤V3<V1	V3=-Vmaxsinθ
Third interval III	V3≤V2<V1	V2=Vmaxsinθ
			Fourth interval IV	V3≤V1<V2	V1=-Vmaxsinθ
Fifth interval V	V1≤V3<V2	V3=Vmaxsinθ
			Sixth interval VI	V1≤V2<V3	V2=-Vmaxsinθ

The third column in table 1 represents the voltage value centered in each interval, where θ e [ -30 °,30 °).

According to the characteristics, the output voltage of the 3 linear Hall elements is decoded, and the position of the motor rotor can be obtained. The specific method is, as shown in fig. 5, firstly determining which electrical angle interval in the electrical angle cycle is currently located according to the interval division criteria described in the first column and the second column of table 1 based on the magnitude relationship of the voltage values output by the 3 linear hall elements, then calculating the position of the motor rotor according to the voltage values and the electrical angle intervals, and then calculating the rotation speed of the motor rotor according to the positions of more than two motor rotors.

Specifically, after the current electrical angle interval is judged, the position theta of the motor rotor is calculated according to the following formula_e：

$\begin{array}{c}{\mathrm{\θ}}_e={\mathrm{\θ}}_x+\arcsin (K\·V_e)\\ ={\mathrm{\θ}}_x+\arcsin (\frac{1}{V_{\max }}\·V_e)\end{array},$ Wherein, theta_xThe values of the initial position of the electrical angle interval are shown in table 2:

TABLE 2 initial position of the electric Angle section

Interval of electric angle	Initial position thetax(unit: degree)
		First interval I	0
Second interval II	60
		Third interval III	120
Fourth interval IV	180
		Fifth interval V	240
Sixth interval VI	300

V_eThe voltage value with the middle size among the output voltage values of 3 linear Hall elements in the electrical angle interval is shown in a table 3:

TABLE 3 intermediate Voltage values in the Electrical Angle Range

Interval of electric angle	Intermediate voltage value Ve
		First interval I	V1
Second interval II	-V3
		Third interval III	V2
Fourth interval IV	-V1
		Fifth interval V	V3
Sixth interval VI	-V2

As shown in FIG. 7, θ ≈ sin θ is approximated when θ is a small angle, and in the above method, θ ∈ [ -30 °,30 °) is a small angle, and thus sin θ can be approximated by θ_e=V₁=V_maxsinθ≈V_maxTheta, intermediate voltage value V in the second interval II_e=-V₃=-V_maxsinθ≈-V_maxθ, other electrical angle intervals are similar.

Approximating sin θ by θ can simplify the computation of arcsin () function in position computation, thereby greatly reducing the amount of computation. Therefore, preferably, the position θ of the motor rotor is calculated according to the following formula_e：

$\begin{array}{c}{\mathrm{\θ}}_e={\mathrm{\θ}}_x+K\·V_e\\ ={\mathrm{\θ}}_x+\frac{1}{V_{\max }}\·V_e\end{array},$ Wherein, theta_xIs shown in Table 2, V_eThe values of (a) are shown in Table 3.

Further, the method includes calculating a rotational speed of the motor rotor based on the positions of the two or more motor rotors. Preferably, the output voltage of the linear Hall element is sampled by a sampling period T, the position of the motor rotor at each sampling time is calculated according to the voltage sampling value, and the rotor position theta at the moment k-1 is utilized_e,k-1And rotor position θ at time k_e,kThe rotating speed n of the motor rotor can be calculated according to the following formula_k：

Wherein p is the pole pair number of the position sensor rotor.

The above embodiments are merely exemplary embodiments of the present invention, which should not be construed as limiting the scope of the present invention, which is defined by the following claims. Various modifications and equivalents may be made by those skilled in the art within the spirit and scope of the present invention, and these modifications and equivalents should also be construed as falling within the scope of the present invention.

Claims (5)

1. A detection method of motor rotor position and rotation speed is based on a detection device of motor rotor position and rotation speed, the detection device of motor rotor position and rotation speed includes a position sensor rotor fixedly arranged on a rotating shaft of the motor rotor, the position sensor rotor includes a permanent magnet capable of generating a sinusoidal space magnetic field, the detection device also includes 3 linear Hall elements arranged on a motor stator and used for detecting the sinusoidal space magnetic field, each linear Hall element is distributed on a circumference which takes the rotating shaft as a circle center on a plane vertical to the rotating shaft in a mode of mutually differentiating 120 electrical angles, and the detection method is characterized in that,

judging which electric angle section is currently in an electric angle cycle according to the magnitude relation among a first voltage value, a second voltage value and a third voltage value respectively output by a first linear Hall element, a second linear Hall element and a third linear Hall element which are sequentially and adjacently arranged in the 3 linear Hall elements, and then calculating the position of the motor rotor according to the voltage values and the electric angle sections, wherein the judging of which electric angle section is currently in the electric angle cycle specifically comprises:

when the second voltage value is smaller than or equal to the first voltage value and the first voltage value is smaller than the third voltage value, the electrical angle interval is a first interval;

when the second voltage value is smaller than or equal to the third voltage value and the third voltage value is smaller than the first voltage value, the electrical angle interval is a second interval;

when the third voltage value is less than or equal to the second voltage value and the second voltage value is less than the first voltage value, the electrical angle interval is a third interval;

when the third voltage value is less than or equal to the first voltage value and the first voltage value is less than the second voltage value, the electrical angle interval is a fourth interval;

when the first voltage value is smaller than or equal to the third voltage value and the third voltage value is smaller than the second voltage value, the electrical angle interval is a fifth interval;

and when the first voltage value is smaller than or equal to the second voltage value and the second voltage value is smaller than the third voltage value, the electrical angle interval is a sixth interval.

2. The method of claim 1, wherein the position θ of the rotor is calculated according to the following formula_e：

θ_e＝θ_x+K·V_e，

Wherein,

θ_xthe values of the initial position of the electrical angle interval are as follows:

k is the reciprocal of the voltage value corresponding to the maximum magnetic field strength detected by the linear Hall element,

V_ethe effective voltage value in the electrical angle interval is as follows:

3. the method of claim 1, wherein the position θ of the rotor is calculated according to the following formula_e：

θ_e＝θ_x+arcsin(K·V_e)，

Wherein,

θ_xthe values of the initial position of the electrical angle interval are as follows:

k is the reciprocal of the voltage value corresponding to the maximum magnetic field strength detected by the linear Hall element,

V_ethe effective voltage value in the electrical angle interval is as follows:

4. the method of claim 1, further comprising calculating the rotational speed of the motor rotor based on the positions of two or more of the motor rotors.

5. The method as claimed in claim 4, wherein the rotor position θ at the time of k-1 is calculated_e,k-1And rotor position θ at time k_e,kThe time difference between the k-1 moment and the k moment is T, and the rotating speed n of the motor rotor is calculated according to the following formula_k：

$n_k=\frac{60\×({\mathrm{\θ}}_{e,k}-{\mathrm{\θ}}_{e,k-1})}{2p\mathrm{\π}T},$

Wherein p is the number of pole pairs of the permanent magnet of the position sensor rotor.