Servo motor and servo motor position detection method

Abstract

The present invention relates to the technical field of servo motor position detection, and in particular to a servo motor and a servo motor position detection method. The method comprises: installing a choke ring, a multi-pole magnetic ring, and a circular magnetic sensor detection unit in the motor; applying an AC sinusoidal voltage excitation to the circular magnetic sensor detection unit; sensing the sinusoidal change of the magnetic field through the circular magnetic sensor detection unit, and outputting a standing wave signal; superimposing the standing wave signals output by each circular magnetic sensor detection unit to obtain a traveling wave signal; and detecting the traveling wave signal through a time-grid signal processing system to determine the position of the motor. The present invention can increase the output signal, improve the position detection accuracy and measurement sensitivity of the servo motor; reduce the harmonic components of the output signal, and improve the measurement accuracy; directly add the output electrical signals of each magnetic sensor, thereby avoiding the problem that a multiplier is required in the previous motor position detection method based on the time-grid technology, and the more probes there are, the more complicated the multiplication circuit will be.

Description

Technical Field

[0001] The present invention relates to the technical field of servo motor position detection, and in particular to a servo motor and a servo motor position detection method. Background Art

[0002] At present, due to the compact structure of servo motors and the relatively harsh working environment inside and outside the motors, there is no precision displacement sensor that can be directly embedded in the motors to directly detect the angular position of the motor rotors. Most of them are external position detection sensors installed coaxially with the motors or installed beside the motors, such as gratings. This external installation not only destroys the original compact structure of the motor and makes installation and debugging difficult, but also affects the running performance of the motor. In recent years, the "sensorless detection technology" that has emerged at home and abroad is complex and heavily dependent on the accuracy of the motor's own parameters. After the motor runs for a long time, the parameters will change nonlinearly, resulting in this solution can only be used as an auxiliary means of motor detection.

[0003] In view of the above problems, there is an embedded motor position detection method based on time-grid technology in the prior art. The motor rotor position is detected by winding a coil on the motor rotor as a sensor head. However, the coil winding is inconvenient, and the signal transmission efficiency is low, the frequency response is low, and the accuracy is low. Therefore, a permanent magnet servo motor position detection technology based on time-grid technology and magnetic sensing has been developed. However, due to the small number of pole pairs of the servo motor permanent magnet array and the number of magnetic sensor heads, as well as the cross-effect of the magnetic field, the measurement interference is large, the accuracy is low, and the resolution is low. In order to improve the resolution, multi-probe phase frequency doubling is used to achieve this. However, according to the time-grid measurement principle, the interpolation pulse clock frequency needs to be increased, which makes this method meaningless. In addition, this method requires a multiplier. The more probes there are, the more complex the multiplier will be.

[0004] In order to address the deficiencies of the servo motor position detection technology based on the time-grid technology, the present invention proposes a new servo motor and a position detection method thereof. Summary of the invention

[0005] The purpose of the present invention is to provide a servo motor and a servo motor position detection method, which are used to solve the problem of insufficient servo motor position detection technology based on time-grid technology mentioned in the background technology. The method of the present invention improves the servo electromechanical position measurement accuracy by increasing the number of poles of the permanent magnet array and a traveling wave formation method based on a multi-sensor head.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a servo motor position detection method, comprising the following steps:

[0008] A choke ring 3 and a multi-pole magnetic ring 4 are fixedly installed outside the rotating shaft 1 of the motor and at one side of the permanent magnetic array 2, and a regularly arranged annular magnetic sensing detection unit 5 is installed at the motor end cover 6 of the motor;

[0009] Applying an AC sinusoidal voltage excitation to the annular magnetic sensing detection unit 5;

[0010] When the motor rotates, the multi-pole magnetic ring 4 rotates with the motor shaft 1, and the magnetic field generated by the multi-pole magnetic ring 4 rotates accordingly. The annular magnetic sensor detection unit senses the sinusoidal change of the magnetic field and outputs a standing wave signal.

[0011] The standing wave signals output by each annular magnetic sensing detection unit are superimposed to obtain a traveling wave signal;

[0012] The motor position can be determined by detecting the traveling wave signal through the time-grid signal processing system.

[0013] Furthermore, the standing wave signals output by the respective annular magnetic sensing detection units are superimposed to obtain a traveling wave signal, which mainly includes:

[0014] Assume that the pole pitch of a pair of NS magnetic poles of the multi-pole magnetic ring is W, and 4n pairs of magnetic sensor probes are arranged in a pair of NS magnetic poles, which are denoted as G 1i , G 2i , G 3i With G 4i ,i=1,2,3,...,n; and G 1i With G 2i Corresponding to the orthogonal placement of space, G 3i With G 4i The corresponding space is placed orthogonally; G 1i With G 2i Apply cosine and sine excitation respectively to G 3i With G 4i Apply negative cosine and sine excitation;

[0015] The 4n standing wave signals output by the 4n magnetic sensors are:

[0016]

[0017]

[0018]

[0019]

[0020] i=1,2,3,......,n

[0021] will u 1i 、u 2i 、u3i 、u 4i The signals are superimposed to obtain four standing wave signals u1, u2, u3, and u4, expressed as follows:

[0022]

[0023]

[0024] By adding the u1 and u2 signals, we can get a traveling wave signal u N :

[0025]

[0026] At the same time, directly superimposing the u3 and u4 signals can obtain another traveling wave signal u S :

[0027]

[0028] Add the two traveling wave signals to get the final traveling wave signal u:

[0029]

[0030] The present invention also provides a servo motor for convenient position detection, comprising a motor shaft and a permanent magnet array fixedly mounted on the motor shaft, and a motor end cover, wherein a choke magnetic ring and a multi-pole magnetic ring are fixedly mounted on the motor shaft;

[0031] The choke magnetic ring and the multi-pole magnetic ring are located between the permanent magnetic array and the motor end cover, and the choke magnetic ring is fixed close to the permanent magnetic array;

[0032] A circular magnetic sensor detection unit is also installed on one side of the motor end cover.

[0033] Furthermore, the choke ring is made of magnetic conductive material, and its width is greater than the thickness of the permanent magnet array of the motor.

[0034] Furthermore, the multi-pole magnetic ring is a permanent magnet sheet with NS alternating arrangement, and the magnetic ring is magnetized along the thickness direction of the magnet.

[0035] Furthermore, the annular magnetic sensor detection unit is composed of a plurality of GMR magnetic sensor arrays and is integrally manufactured using microelectronic printing technology.

[0036] The present invention has at least the following beneficial effects:

[0037] The present invention can increase the output signal and improve the position detection accuracy and measurement sensitivity of the servo motor by increasing the number of pole pairs of the permanent magnet array and the number of sensing detection unit probes within a pair of poles; at the same time, by controlling the processing accuracy of the installed multi-pole magnetic ring permanent magnet array and the probe, that is, controlling the spatial position accuracy, the harmonic components of the output signal are reduced and the measurement accuracy is improved.

[0038] In addition, the present invention enhances the magnetic field strength felt by the magnetic sensor installed on the motor end cover through the axial magnetization direction of the permanent magnet array, and at the same time avoids the cross-action of the motor permanent magnet and the motor stator winding magnetic field, making the acting magnetic field more single, improving the signal quality and thus improving the measurement accuracy.

[0039] The method of the present invention not only improves the detection accuracy of the servo motor, but also provides a new method for forming a time-grating wave signal. This traveling wave forming method directly adds the output electrical signals of each magnetic sensor, avoiding the need to use a multiplier in the early motor position detection method based on the time-grating technology, and the disadvantage that the more the number of probes, the more complex the multiplication circuit will be. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0041] Figure 1 This is the exploded diagram of the servo motor position detection device;

[0042] Figure 2 It is the corresponding relationship diagram between the magnetic field intensity and the spatial position of the permanent magnetic array;

[0043] Figure 3 This is a schematic diagram of the position detection principle of a pair of probe servo motors based on permanent magnet array and time-grating technology;

[0044] Figure 4 This is the principle diagram of N pairs of probe servo motor position detection based on permanent magnet array and time grating technology;

[0045] Figure 5 It is the relationship diagram between the number of sensor heads and the amplitude of the traveling wave signal;

[0046] Figure 6 This is the installation diagram of the servo motor position detection device;

[0047] Figure 7 Schematic diagram of the position detection principle of 6 pairs of probe servo motors based on permanent magnet array and time grating technology

[0048] Figure 8The corresponding relationship diagram between the permanent magnet array of the rotating motor and the sensor head (24 pairs of sensor heads with 4 pairs of poles in one circle); among them, (a) is a schematic diagram of the permanent magnet array; (b) is an enlarged diagram of the excitation and output of the sensor head within a pair of poles; (c) is the layout of the sensor head and the excitation and output lead diagram.

[0049] In the figure: 1. Motor shaft; 2. Permanent magnet array; 3. Choke magnetic ring; 4. Multi-pole magnetic ring; 5. Circular magnetic sensor detection unit; 6. Motor end cover. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0051] Aiming at the technical bottleneck that the position sensing technology commonly used in servo motors cannot break through the efficient integration, the present invention proposes a new high-precision and easy-to-integrate position sensing method based on time-grating technology and magnetic sensing on the basis of previous time-grating technology research. The time-grating displacement sensor arranges a pair of sensing heads in a pair of poles. The more pole pairs there are, the more probes there are, and the higher the accuracy. However, in some occasions where the number of pole pairs is limited, such as permanent magnet servo motors, which are generally in the single digit, the signal sensed by the limited number of probes is weak, which puts higher requirements on the spatial position of the installation, such as the installation gap, parallelism, and the flatness of the installation surface. To this end, a method is proposed to improve the measurement accuracy by increasing the number of permanent magnet arrays to increase the number of poles, and by increasing the number of sensing heads to increase the amplitude and quality of the measurement signal. These two methods can be used simultaneously or separately according to actual conditions.

[0052] In order to increase the number of arrays and avoid the cross-effect of the magnetic field of the motor stator coil and the magnetic field of the permanent magnet, and improve the measurement accuracy, a choke ring 3 and a multi-pole magnetic ring 4 structure are designed on the end face of the motor. By increasing the number of probes within a pair of permanent magnets (i.e., a pair of poles), a new wave signal formation method is proposed, which can be used to improve the output signal strength when the number of array poles is small.

[0053] like Figure 1 As shown, the rotary servo motor position detection device includes a choke ring 3, a multi-pole magnetic ring 4, a circular magnetic sensor detection unit 5, and the motor's own shaft 1, a permanent magnet array 2, and an end cover 6. The choke ring 3 is a magnetic conductive material, and its width is greater than the thickness of the motor's permanent magnet array 2; the multi-pole magnetic ring 4 is a permanent magnet sheet with NS alternately arranged, and the magnetic ring is magnetized along the thickness direction of the magnet, that is, axial magnetization. The choke ring 3 and the multi-pole magnetic ring 4 are bonded together and rigidly connected to the motor shaft 1, and rotate with the rotation of the shaft, as shown in FIG. Figure 6The annular magnetic sensing detection unit 5 is composed of a GMR magnetic sensing array, and in order to ensure the spatial position accuracy of each sensor, it is integrated by using microelectronic printing technology to improve the measurement accuracy.

[0054] A choke ring 3 and a multi-pole magnetic ring 4 are rigidly installed coaxially with the motor shaft on the axial end face of the motor. The choke ring 3 confines the magnetic field generated by the servo motor permanent magnet array 2 within the choke ring 3. The multi-pole magnetic ring 4 is installed close to the choke ring 3. A circular magnetic sensor detection unit 5 arranged according to a certain pattern is installed at the motor end cover 6, and an AC sinusoidal voltage excitation is applied to it.

[0055] The multi-pole magnetic ring 4 generates Figure 2 As shown in the figure, the magnetic field changes according to the sinusoidal law. When the motor rotates, the multi-pole magnetic ring 4 rotates with the motor shaft 1, and a magnetic field is generated between the motor and the end cover. Figure 2 The alternating magnetic field shown in the figure also rotates accordingly, and the annular magnetic sensor detection unit 5 installed at the end cover senses the sinusoidal change of the magnetic field and outputs a standing wave signal that changes with the magnetic field. The standing wave signals output by each annular magnetic sensor detection unit 5 are superimposed to obtain a traveling wave signal output, and the phase information of the traveling wave signal is then detected by the existing time-grating signal processing system to determine the position of the motor.

[0056] The specific principles are as follows:

[0057] The traveling wave signal formation method based on permanent magnet array is as follows Figure 3 As shown, a pair of NS magnetic poles has a pole pitch W, and two magnetic sensors G1 and G2 are arranged at positions 90° apart in space, that is, at a distance of W / 4. An alternating magnetic field is generated around the magnetic poles as shown in Figure 2 As shown. Apply AC excitation voltages cosωt and sinωt to G1 and G2. As the permanent magnet array moves left and right, i.e. the motor rotates or the linear motor moves, the magnetic sensor senses the magnetic field that changes alternately according to the sinusoidal law. G1 and G2 output u respectively. 11 、u 21 The modulated standing wave signal, u 11 、u 21 After superposition, the electric traveling wave signal can be obtained

[0058]

[0059] Where K is the magnetic induction coefficient and x is the displacement.

[0060] According to the time-grating measurement principle, the traveling wave signal is amplified, filtered, shaped, phase-compared, and high-frequency clock pulse interpolated to achieve motor position detection.

[0061] Since the number of permanent magnet arrays of the servo motor is relatively small, in order to improve the measurement signal strength, it is proposed to arrange 4n pairs of sensor heads within a pair of NS permanent magnets. The principle of traveling wave formation is as follows: Figure 4 shown.

[0062] 4n magnetic sensors are arranged at equal intervals within a pair of permanent magnets, i.e. within a pole pitch, and the positions are as follows: Figure 4 As shown, the magnetic sensor G 1i With G 2i (i=1,2,3,......,n) is orthogonal placement in the corresponding space, G 3i With G 4i (i=1,2,3,......,n) is orthogonal placement in the corresponding space, G 1i With G 2i Apply cosine and sine excitation respectively to G 3i With G 4i Apply negative cosine and sine excitation. 4n magnetic sensors G 1i With G 2i , G 3i With G 4i The corresponding second subscripts are the same as the spatial orthogonal relationship, such as G 12 With G 22 , G 33 With G 43 The spaces are orthogonal.

[0063] When the rotary motor rotates or the linear motor moves, the 4n standing wave signals output by the 4n magnetic sensors are:

[0064]

[0065]

[0066]

[0067]

[0068] i=1,2,3,......,n

[0069] will u 1i 、u 2i 、u 3i 、u 4i The signals are superimposed to obtain four standing wave signals u1, u2, u3, and u4, expressed as follows:

[0070]

[0071]

[0072] By adding the u1 and u2 signals, we can get a traveling wave signal u N :

[0073]

[0074] At the same time, directly superimposing the u3 and u4 signals can obtain another traveling wave signal u S :

[0075]

[0076] Finally, the two traveling wave signals are added to obtain the final traveling wave signal u:

[0077]

[0078] By fitting the traveling wave signal amplitude of the multi-sensor head using Matlab Get as Figure 5 The corresponding relationship between the number of sensing heads and the signal amplitude is shown in the figure. As can be seen from the figure, the more the number of sensing heads, the larger the signal amplitude, the stronger the traveling wave signal, and the more conducive to signal processing. According to the principle of traveling wave signal generation, correspondingly, if the number of permanent magnetic array poles is more, the signal strength is also stronger, and the signal amplitude has a direct multiple corresponding relationship with the number of permanent magnetic array poles.

[0079] Embodiment 1:

[0080] This example takes 6 pairs of 12 GMR sensor heads installed within the range of a pair of NS permanent magnets, that is, within a pole distance W, as an example for specific description:

[0081] The distribution of the 12 sensor heads is as follows: Figure 7 As shown, they are applied as Figure 7 The AC sinusoidal voltage excitation shown in the figure makes the motor rotate, and the multi-pole magnetic ring rotates with the motor shaft, generating a magnetic field that changes alternately according to the sine law in the gap between the motor and the end cover. The magnetic sensor installed at the end cover senses the change of the magnetic field and outputs a standing wave signal that changes with the change of the magnetic field. The standing wave signals output by each sensor are added together to obtain the traveling wave signal output, and then the motor position can be determined by processing it through the time grid signal processing system. The traveling wave formation process is further explained as follows:

[0082] like Figure 7 As shown, the 12 sensor heads are divided into 4 groups, 3 in each group, namely G 11 , G 12 , G 13 , G 21 , G 22 , G 23 , G 31 , G 32 , G 33 , G 41 , G 42 , G 43 , where the sensor head G 1i With G 3i(i=1,2,3) is the sinusoidal signal sensor head, G 2i With G 4i (i=1, 2, 3) is the cosine signal sensor head. 11 With G 21 Place them orthogonally in space as a pair, i.e., with a spacing of W / 4, G 1i (i=1, 2, 3) are equally spaced, and the interval between adjacent sensor probes is W / 4÷3, that is, W / 12, G 2i (i=1,2,3) distribution mode and G 1i Same. 1i With G 2i By adding cosine and sine excitation, we can get 6 standing wave signals:

[0083]

[0084]

[0085]

[0086]

[0087]

[0088]

[0089] will u 1i Adding all the signals together, we can get the standing wave signal u1, that is:

[0090]

[0091] will u 2i By adding all the signals, we can get another standing wave signal u2, namely:

[0092]

[0093] Add the two standing wave signals to get a line wave signal u N :

[0094]

[0095]

[0096] G 3i With G 4i (i=1,2,3) The distribution of probes and G 1i With G 2i Same, G 11 With G 31 Interval W / 2, G 31 With G 41Orthogonal placement, interval W / 4, G 3i Equally spaced, the spacing between adjacent sensor heads is W / 4÷3, which is W / 12, G 4i Distribution and G 3i Same, then go to G 3i With G 4i By adding negative cosine and sine excitation, we can get the same 6 standing wave signals:

[0097]

[0098]

[0099]

[0100]

[0101]

[0102]

[0103] Similarly:

[0104] will u 3i By adding all the signals together, a new standing wave signal u3 can be obtained, namely:

[0105]

[0106] will u 4i By adding all the signals together, we can get a new standing wave signal u4:

[0107]

[0108] Add the two standing wave signals to get a line wave signal u S :

[0109]

[0110] Finally, the two traveling wave signals are added to obtain the final traveling wave signal u:

[0111]

[0112] This example is extended to a circle of 4 pairs of permanent magnet arrays. Figure 8 As shown in (a), a pair of permanent magnetic arrays, that is, 6 pairs of probes are arranged within a pole pitch range. The spatially uniform distribution position relationship of the magnetic sensor heads and the input and output of the signals are shown in Figure 8 (b) shows the spatial position relationship of 24 pairs of probes in one circle, as well as the excitation signal input and the generated traveling wave signal output. Figure 8As shown in (c), the same number of sensor heads are arranged within each pair of NS permanent magnet arrays, and the positions are the same. The output of the four pairs of permanent magnet arrays is repeated four times relative to the output of one pair, and the signal amplitude is four times that of one pair. The output traveling wave signal expression is:

[0113]

[0114] In practical applications, the number of probe pairs arranged within a pair of permanent magnets is not limited to 6 pairs in this example, and 1 pair, 2 pairs, ... n pairs may be arranged according to the number of pairs of permanent magnet arrays, spatial positions and actual needs.

[0115] This method is not only applicable to rotary permanent magnet servo motors, but also to the implementation of position detection schemes for linear permanent magnet servo motors and other motors.

[0116] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A servo motor position detection method, characterized in that: The following steps are involved: A choke magnetic ring and a multi-pole magnetic ring are fixedly installed at the end surface position of the permanent magnetic array of the motor, and the choke magnetic ring is close to the permanent magnetic array, and a regularly arranged circular magnetic sensor detection unit is installed at the motor end cover of the motor; Applying an AC sinusoidal voltage excitation to the annular magnetic sensing detection unit; When the motor rotates, the multi-pole magnetic ring rotates with the motor shaft, and the magnetic field generated by the multi-pole magnetic ring rotates accordingly. The circular magnetic sensor detection unit senses the sinusoidal change of the magnetic field and outputs a standing wave signal. The standing wave signals output by each annular magnetic sensing detection unit are superimposed to obtain a traveling wave signal; The motor position can be determined by detecting the traveling wave signal through the time-grid signal processing system; Among them, the standing wave signals output by each annular magnetic sensor detection unit are superimposed to obtain a traveling wave signal, which mainly includes: Assume that the pole pitch of a pair of NS magnetic poles of the multi-pole magnetic ring is W, and 4n pairs of magnetic sensor probes are arranged in a pair of NS magnetic poles, which are denoted as G 1i , G 2i , G 3i With G 4i , i=1,2,3,...,n; and G 1i With G 2i Corresponding to the orthogonal placement of space, G 3i With G 4i The corresponding space is placed orthogonally; G 1i With G 2i Apply cosine and sine excitation respectively to G 3i With G 4i Apply negative cosine and sine excitation; The 4n standing wave signals output by the 4n magnetic sensors are: will u 1i 、u 2i 、u 3i 、u 4i The signals are superimposed to obtain four standing wave signals u1, u2, u3, and u4, expressed as follows: By adding the u1 and u2 signals, we can get a traveling wave signal u N : At the same time, directly superimposing the u3 and u4 signals can obtain another traveling wave signal u S : Add the two traveling wave signals to get the final traveling wave signal u:

2. A servo motor having a servo motor position detection method as claimed in claim 1, comprising a motor shaft and a permanent magnet array fixedly mounted on the motor shaft, and also comprising a motor end cover, characterized in that: A choke magnetic ring and a multi-pole magnetic ring are fixedly mounted on the motor shaft; The choke magnetic ring and the multi-pole magnetic ring are located between the permanent magnetic array and the motor end cover, and the choke magnetic ring is fixed close to the permanent magnetic array; A circular magnetic sensor detection unit is also installed on one side of the motor end cover.

3. The servo motor according to claim 2, characterized in that: The choke ring is made of magnetic conductive material, and its width is greater than the thickness of the permanent magnet array of the motor.

4. The servo motor according to claim 2, characterized in that: The multi-pole magnetic ring is a permanent magnet sheet with NS alternately arranged, and the magnetic ring is magnetized along the thickness direction of the magnet.

5. The servo motor according to claim 2, characterized in that: The annular magnetic sensor detection unit is composed of a plurality of GMR magnetic sensor arrays and is integrally manufactured using microelectronic printing technology.

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