CN117411371A

CN117411371A - High-precision servo control system

Info

Publication number: CN117411371A
Application number: CN202311303116.8A
Authority: CN
Inventors: 岳小云; 郝斌; 范浩; 赵屹涛; 闫宪峰; 苏跃龙; 葛海婷; 吕迎玺; 张永平
Original assignee: Shanxi Mechanical And Electrical Design And Research Institute Co ltd
Current assignee: Shanxi Mechanical And Electrical Design And Research Institute Co ltd
Priority date: 2023-10-10
Filing date: 2023-10-10
Publication date: 2024-01-16

Abstract

The invention relates to the technical field of servo control, in particular to a high-precision servo control system. The high-precision servo control system comprises a servo motor, a plurality of pairs of pole magneto-electric encoders, a servo controller, a servo driver and an executing mechanism; the multi-pair pole magneto-electric encoder comprises a second multi-pair pole magnet, a first multi-pair pole magnet, a third multi-pair pole magnet and a circuit board, wherein a first group of Hall elements, a second group of Hall elements and a third group of Hall elements on the circuit board are respectively arranged adjacent to the first multi-pair pole magnet, the second multi-pair pole magnet and the third multi-pair pole magnet, and corresponding detection signals are output according to magnetic pole signals of the corresponding magnets. The multi-pair pole magneto-electric encoder of the high-precision servo control system provided by the invention can be used for calibrating the actual angle of the outermost ring magnet by acquiring the mechanical angle with certain precision, so that the measurement precision is greatly improved, and the multi-pair pole magneto-electric encoder is especially suitable for working condition scenes of angle detection and position detection of large and medium-sized servo systems.

Description

High-precision servo control system

Technical Field

The invention relates to the technical field of servo control, in particular to a high-precision servo control system.

Background

A servo control system is an automatic control system that is commonly used to control motors and other actuators. The sensor detects the change of physical quantity, and then the output signal and the input signal reach expected values through calculation and control, so that the precise control of the motion state of the actuating mechanism is realized. The servo control system can be classified into position control, speed control and torque control according to the control mode. Wherein, the position control means the process that the control system controls the executing mechanism to achieve reaching the target position; the speed control means that the control system controls the actuating mechanism to realize precise control of the movement speed; torque control refers to controlling the magnitude and direction of the torque output by the actuator by the control system. As manufacturing upgrades, the downstream industries are increasingly demanding lean manufacturing equipment. The lean equipment needs to precisely control the motion elements such as displacement, speed, moment and the like, and the motion elements are realized through a high-precision servo control system.

In a servo control system, the accuracy of the encoder directly affects the speed control and positioning accuracy of the system. Currently, photoelectric encoders are widely used, and are mounted on a rotating shaft, so that angle information can be transmitted to a controller through a cable. However, the photoelectric encoder has some defects that are difficult to overcome, for example, a code disc of the photoelectric encoder is made of glass, and a very thin scribing line is deposited on the glass, so that the photoelectric encoder has low vibration resistance and impact resistance, is not suitable for severe environments such as dust, condensation and the like, and has complex structure and positioning assembly although the thermal stability and the precision can meet the measurement requirements. In production, high assembly accuracy must be ensured, which directly affects the production efficiency and ultimately the cost of the product.

To overcome the above-described deficiencies of encoders, magneto-electric encoders for a single pair of poles or multiple pairs of poles of an inner and outer ring for a servo control system have been developed. Such an encoder includes a magnet, a magnetic induction element, and a signal processing circuit. The magnet rotates with the servo motor shaft, producing a varying magnetic field. The magnetic induction element senses the changed magnetic field, converts a magnetic signal into an electric signal and outputs the electric signal to the signal processing circuit. The signal processing circuit processes the electrical signal to an angled signal output.

Along with the improvement of lean equipment control precision, the requirements on the resolution of the magneto-electric encoder are also higher and higher. In order to increase the resolution of the encoder, the number of pole pairs is usually increased, but in the practical application process, when the number of pole pairs of the inner ring and outer ring multi-pair magneto-electric encoder is increased to a certain number, the detection signals collected by the magneto-sensitive elements are completely overlapped in a certain angle interval due to the influence of errors and noise, so that the absolute angle of the magneto-electric encoder cannot be obtained, and the requirement of precise control of a servo control system cannot be met.

Disclosure of Invention

In view of the above, the present invention aims to provide a high-precision servo control system, which aims to overcome the defect that the precision of the servo control system cannot be improved due to the fact that detection signals acquired by magnetic sensors are completely overlapped in a certain interval due to the increase of the pole pair number.

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

the high-precision servo control system provided by the invention comprises a servo motor;

a plurality of pairs of pole magneto-electric encoders coaxially arranged with the servo motor and outputting absolute angles corresponding to high precision and/or ultra-high precision at a rotational speed range of the servo motor according to the rotational speed range, wherein the plurality of pairs of pole magneto-electric encoders comprise a second plurality of pairs of pole magnets, a first plurality of pairs of pole magnets and a third plurality of pairs of pole magnets and a circuit board which are coaxially and radially annularly arranged, wherein the first plurality of pairs of pole magnets comprise m pairs of magnetic poles and 3.ltoreq.m < 23, the second plurality of pairs of pole magnets comprise n pairs of magnetic poles and 3.ltoreq.n < 23, m is greater than n and is a natural number which is mutually equal to or greater than 100, and the third plurality of pairs of pole magnets comprise p pairs of magnetic poles and p.ltoreq.100; in addition, the circuit board comprises:

a first group of hall elements including a first linear hall sensor and a second linear hall sensor, disposed adjacent to the first plurality of pairs of pole magnets, and outputting a first group of detection signals according to magnetic pole signals of the first plurality of pairs of pole magnets;

a second group of hall elements including a third linear hall sensor and a fourth linear hall sensor, disposed adjacent to the second plurality of pairs of pole magnets, and outputting a second group of detection signals according to the magnetic pole signals of the second plurality of pairs of pole magnets;

A third group of hall elements including a fifth linear hall sensor, a sixth linear hall sensor, and a seventh linear hall sensor, disposed adjacent to the third multi-pair pole magnet, and outputting a modified third group of detection signals according to the magnetic pole signals of the third multi-pair pole magnet;

the servo controller comprises a control unit and a current sensor, wherein the control unit receives the angle information of a servo motor shaft fed back by the plurality of pairs of polar magneto-electric encoders and receives current signals acquired by the current sensor, and the servo controller sends out working instructions for controlling the servo motor after processing the angle information;

the servo driver receives a control instruction sent by the servo controller and outputs a driving signal of the servo motor according to the load requirement of the servo motor;

and the actuating mechanism is connected with the servo motor, and the servo motor drives the actuating mechanism to realize precise control on the motion state of the actuating mechanism.

Further, the multi-pair-pole magnetoelectric encoder selects and outputs the absolute angle with high precision and/or ultra-high precision under the rotating speed range of the servo motor through the following formula:

in θ ₃ The final absolute angle output by the multi-pair-pole magneto-electric encoder; θ ₁ Determining a high precision absolute angle for the first and second pluralities of pole magnets; θ ₂ To utilize the obtained high-precision absolute angle theta ₁ Combining the ultra-high precision absolute angles determined by the third multi-pair pole magnet; omega is the current rotating speed of the servo motor; omega ₀ 0.8 times of the maximum rotation speed allowed when the ultra-high precision absolute angle is output for the multi-pair magneto-electric encoder; omega ₁ 1.2 times of the highest rotation speed allowed when the ultra-high precision absolute angle is output for the multi-pair magneto-electric encoder; t represents a control cycle of the control instruction, and k represents a kth control cycle.

Further, the servo motor is a permanent magnet synchronous servo motor.

Still further, m and n are prime numbers and mn < 23X 19.

Further, the first set of detection signals includes: the first linear Hall sensor and the second linear Hall sensor output a first detection signal and a second detection signal according to magnetic pole signals of the first multi-pair pole magnets; the phase difference between the first detection signal and the second detection signal is 90 degrees;

the second set of detection signals includes: the third linear Hall sensor and the fourth linear Hall sensor output a third detection signal and a fourth detection signal according to magnetic pole signals of the second multi-pair magnetic body; the third detection signal and the fourth detection signal are 90 degrees out of phase.

Further, the modified third set of detection signals includes: the fifth linear Hall sensor, the sixth linear Hall sensor and the seventh linear Hall sensor output detection signals of d axis and q axis according to the magnetic pole signals of the third multi-pair pole magnet; the method comprises the steps that a fifth linear Hall sensor, a sixth linear Hall sensor and a seventh linear Hall sensor acquire magnetic pole signals of a third multi-pair pole magnet to obtain an original three-phase Hall signal with 120-degree phase difference, wherein the original three-phase Hall signal is a fifth detection signal, a sixth detection signal and a seventh detection signal; and then, performing zero drift processing on the obtained original three-phase Hall signals, and outputting detection signals of d-axis and q-axis with 90-degree phase difference.

Preferably, the first linear hall sensor is aligned with the third linear hall sensor and the fifth linear hall sensor at one end.

Preferably, the third plurality of pairs of pole magnets are located on the outermost ring, the second plurality of pairs of pole magnets are located on the innermost ring, the first plurality of pairs of pole magnets are interposed between the third plurality of pairs of pole magnets and the second plurality of pairs of pole magnets, and there is an angular difference in the starting pole mounting positions of the first plurality of pairs of pole magnets and the second plurality of pairs of pole magnets.

Preferably, the magnetization directions of the first multi-pair pole magnets and the second multi-pair pole magnets are consistent with the radial direction or the axial direction of the rotating shaft of the servo motor; the magnetization direction of the third multi-pair pole magnet is consistent with the radial direction or the axial direction of the rotating shaft of the servo motor.

Preferably, the actuating mechanism is any one of a screw rod, a guide rail, a speed reducer, a two-dimensional turntable and a numerical control operation platform.

The invention has the beneficial effects that: the multi-pair pole magneto-electric encoder adopted in the high-precision servo control system provided by the invention is that a plurality of pairs of pole magnets with the pole pair number far larger than that of the inner and outer rings are additionally arranged on the radial outermost ring of the original inner and outer ring multi-pair pole magnets, and the actual rotation angle of the outermost ring multi-pair pole magnets is calibrated by utilizing the mechanical angle with certain precision obtained by the original inner and outer ring multi-pair pole magnets, so that the measurement precision of the magneto-electric encoder is greatly improved, and the positioning precision and the angle control precision of the servo control system are correspondingly and greatly improved. The high-precision servo control system provided by the invention is especially suitable for working condition scenes of angle detection and position detection of large and medium-sized servo systems.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained according to these drawings without inventive faculty for a person skilled in the art.

FIG. 1 shows a block diagram of the high-precision servo control system in an embodiment of the present application;

FIG. 2 illustrates a plan view of a multi-pair polar magneto-electric encoder in accordance with an embodiment of the present application;

FIG. 3 illustrates a perspective view of a multi-pair polar magneto-electric encoder in accordance with an embodiment of the present application;

FIG. 4 shows a flow chart of a method for absolute angle detection of a multi-pair magneto-electric encoder in an embodiment of the present application;

FIG. 5 shows a schematic diagram of two linear Hall sensor signal detection in an embodiment of the present application;

FIG. 6 shows a schematic diagram of two linear Hall element detection signals in an embodiment of the present application;

FIG. 7 shows a schematic diagram of three linear Hall sensor signal detection in an embodiment of the present application;

FIG. 8 shows a schematic diagram of three linear Hall sensor detection signals in an embodiment of the present application;

FIG. 9 shows a schematic diagram of zero drift cancellation using three Hall signals in an embodiment of the present application;

FIG. 10 shows a schematic diagram of synthesizing two-phase Hall signals in an embodiment of the present application;

FIG. 11 is a diagram showing the number of values of the magnetic pole position feature values according to the embodiment of the present application;

FIG. 12 is a linear schematic diagram showing the angular switching selection output relationship of absolute angles of multiple pairs of polar magneto-electric encoders in an embodiment of the present application;

FIG. 13 is a flowchart of a control method of a high-precision servo control system according to an embodiment of the present application;

FIG. 14 is a first sub-flowchart of a control method of a high-precision servo control system according to an embodiment of the present application;

FIG. 15 shows a second sub-flowchart of a control method of a high-precision servo control system in an embodiment of the present application.

Detailed Description

Example embodiments are described more fully below with reference to the accompanying drawings. However, the exemplary embodiments may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and thus a repetitive description thereof will be omitted.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the invention.

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are only used to distinguish one from another. As used herein, the term "and/or" includes all combinations of any and one or more of the associated listed items.

Those skilled in the art will appreciate that the drawings are schematic representations of example embodiments only. The modules or flow paths in the drawings are not necessarily required to practice the invention and therefore should not be taken to limit the scope of the invention.

In order to solve the above problems, the present application provides a high-precision servo control system. The multi-pair-pole magneto-electric encoder in the high-precision servo control system adopts three groups of multi-pair-pole magnets which are radially and annularly coaxially arranged. The invention has the core that a plurality of pairs of pole magnets with the magnetic pole pair number far larger than that of the inner ring and the outer ring are additionally arranged on the radial outermost ring of the original inner ring and outer ring multi-pair pole magnets, and the actual rotation angle of the outermost ring multi-pair pole magnets is calibrated by utilizing the mechanical angle with certain precision obtained by the original inner ring and outer ring multi-pair pole magnets, thereby greatly improving the measurement precision of the magnetoelectric encoder and correspondingly greatly improving the positioning precision and the angle control precision of a servo control system. The high-precision servo control system provided by the invention is especially suitable for working condition scenes of angle detection and position detection of large and medium-sized servo systems. The technical scheme of the present application will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a block diagram of the high-precision servo control system in an embodiment of the present application.

As shown in fig. 1, the high-precision servo control system includes: the device comprises a servo controller, a servo driver, a plurality of pairs of pole magneto-electric encoders, a servo motor, an actuating mechanism and an upper computer.

The multi-pair pole magneto-electric encoder is coaxially arranged with the servo motor and outputs an absolute angle corresponding to high precision and/or ultra-high precision in the rotating speed range of the servo motor according to the rotating speed range; the servo controller comprises a control unit and a current sensor, wherein the control unit in the example is an MCU control chip; the control unit receives the angle information of the servo motor shaft fed back by the plurality of pairs of pole magneto-electric encoders and receives the current signals acquired by the current sensors, and the servo controller sends out working instructions for controlling the servo motor after processing the angle information; the servo driver receives a control instruction sent by the servo controller and outputs a driving signal of the servo motor according to the load requirement of the servo motor; the actuating mechanism is connected with the servo motor, and the servo motor drives the actuating mechanism to realize precise control on the motion state of the actuating mechanism; the upper computer is communicated with the controller and sends an angle instruction of the servo motor to the servo controller.

According to an example embodiment of the present application, the multi-pair polar magneto-electric encoder includes an encoder magnet structure 100 and a circuit board. The encoder magnet structure 100 includes a second plurality of pairs of pole magnets 120, a first plurality of pairs of pole magnets 110, and a third plurality of pairs of pole magnets 130 arranged in a coaxial radial ring. The circuit board is provided with a first group of Hall elements, a second group of Hall elements and a third group of Hall elements. In this example, the circuit board is not shown.

According to an example embodiment of the present application, the servo motor is a permanent magnet synchronous servo motor, and includes a stator, a rotor, a rotating shaft, magnetic steel, windings, and a series of connectors. The first, second, third, and circuit board pairs 110, 120, 130 operate simultaneously. The first, second and third pluralities of pole magnets 110, 120, 130 rotate with the shaft of the servo motor. The three sets of hall elements on the circuit board remain stationary.

Fig. 2 shows a plan view of a multi-pair polar magneto-electric encoder in accordance with an embodiment of the present application.

Fig. 3 shows a perspective view of a multi-pair polar magneto-electric encoder in accordance with an embodiment of the present application.

As shown in fig. 2 and 3, the multi-pair magneto-electric encoder includes: a second plurality of pole magnets 120, a first plurality of pole magnets 110, and a third plurality of pole magnets 130 coaxially and radially annularly disposed in a first spatial plane. The first plurality of pairs of pole magnets 110 includes m pairs of poles and 3.ltoreq.m < 23, the second plurality of pairs of pole magnets 120 includes n pairs of poles and 3.ltoreq.n < 23, m is greater than n and mn < 23 x 19, and the third plurality of pairs of pole magnets 130 includes p pairs of poles and p.gtoreq.100. P may be 100, 200, 300, 400, 500, 600, 700, 800, or even more, the greater the number of P, the greater the accuracy of the final magneto-electric encoder. For example, according to some embodiments, m and n are prime numbers and are mutually prime. As shown in fig. 2 and 3, m is 5, n is 3, and p is 100 in the present embodiment, but the present application is not limited thereto.

According to an example embodiment of the present application, the third plurality of pairs of pole magnets 130 are located at the outermost ring, the second plurality of pairs of pole magnets 120 are located at the innermost ring, and the first plurality of pairs of pole magnets 110 are interposed between the third plurality of pairs of pole magnets 130 and the second plurality of pairs of pole magnets 120. For convenience of description, the outer ring, the middle ring, and the inner ring correspond to the third plurality of pairs of pole magnets 130, the first plurality of pairs of pole magnets 110, and the second plurality of pairs of pole magnets 120, respectively. The pole pair number m of the first plurality of pole magnets 110 is greater than the pole pair number n of the second plurality of pole magnets 120. This is because the diameter of the intermediate ring is larger than the diameter of the inner ring, and the number of intermediate ring magnet pole pairs is larger than the number of inner ring magnet pole pairs in order to make the magnet size uniform.

The polar logarithm m of the middle ring and the polar logarithm n of the inner ring are limited in the application, so that in the practical application process, effective detection signals can be obtained, and the detection signals are prevented from overlapping in a certain angle interval.

According to some embodiments of the present application, the magnetization direction of the first plurality of pairs of pole magnets 110 coincides with the radial or axial direction of the servo motor shaft. In the embodiment shown in fig. 2, 3, the magnetization direction of the first plurality of pairs of pole magnets 110 is set to be axial. The second plurality of pole magnets 120 have a magnetization direction that is coincident with the radial or axial direction of the servomotor shaft. In the embodiment shown in fig. 2 and 3, the magnetization direction of the second plurality of pairs of pole magnets 120 is set to be axial. Similarly, the third plurality of pole magnets 130 have a magnetization direction that is aligned with the radial or axial direction of the servomotor shaft. In the embodiment shown in fig. 2 and 3, the magnetization direction of the third plurality of pairs of pole magnets 130 is set to be axial. The present application does not limit the magnetization direction.

The first, second, and third pluralities of pole magnets 110, 120, 130 may each be formed of a plurality of magnetic pole pairs bonded thereto, but are not limited thereto. According to the embodiment of the application, the magnets can be made of neodymium iron boron permanent magnet materials, and a plurality of magnets can be attached to the substrate or directly attached to the end part of the rotating shaft. According to some embodiments, a plurality of magnets may be disposed on the support plate. The support plate may have a ring-shaped structure, and the second, first and third pairs of pole magnets 120, 110 and 130 may be sequentially disposed along a circumferential normal direction of the inner hole thereof. The fixing means may be glue joint, and when the fixing means is installed, there is an installed angle difference between the initial poles of the first and second pairs of pole magnets 110 and 120.

As shown in fig. 2 and 3, the multi-pair magnetic-electric encoder further includes a first group of hall elements, a second group of hall elements, and a third group of hall elements for detecting magnetic signals generated by the multi-pair magnets.

A first group of hall elements including a first linear hall sensor 111 and a second linear hall sensor 112 are disposed adjacent to the first plurality of pairs of pole magnets 110, and output a first group of detection signals according to magnetic pole signals of the first plurality of pairs of pole magnets 110. The output signals of the first linear hall sensor 111 and the second linear hall sensor 112 are 90 degrees out of phase.

A second group of hall elements including a third linear hall sensor 121 and a fourth linear hall sensor 122 are disposed adjacent to the second plurality of pairs of pole magnets 120, and output a second group of detection signals according to the magnetic pole signals of the second plurality of pairs of pole magnets 120. The output signals of the third linear hall sensor 121 and the fourth linear hall sensor 122 are out of phase by 90 degrees.

A third group of hall elements including a fifth linear hall sensor 131, a sixth linear hall sensor 132, and a seventh linear hall sensor 133 are disposed adjacent to the third plurality of pairs of pole magnets 130, and output a modified third group of detection signals according to the magnetic pole signals of the third plurality of pairs of pole magnets 130. The output signals of the fifth, sixth and seventh linear hall sensors 131, 132 and 133 are phase-separated by 120 degrees.

According to some embodiments, in the above encoder structure, the first and third linear hall sensors 111 and 121 and the fifth linear hall sensor 131 are aligned at one end.

FIG. 4 shows a flow chart of a method for absolute angle detection of a multi-pair magneto-electric encoder in an embodiment of the present application.

The application also provides a method for detecting the absolute angle of the multi-pair-pole magneto-electric encoder, as shown in fig. 4, which comprises the following steps:

In step S410, the first set of detection signals, the second set of detection signals, and the modified third set of detection signals are obtained by the first set of hall elements, the second set of hall elements, and the third set of hall elements, respectively.

The multi-pair-pole magnetoelectric encoder comprises an inner ring, a middle ring and an outer ring which are coaxially and radially sequentially annularly arranged, wherein the magnetic pole pairs of the inner ring and the middle ring are mutually equal, and the three groups of magnets are coaxially arranged on a rotating shaft and are isolated by an isolation means so as to prevent magnetic field coupling. The magnetic field around the three sets of multi-pair pole magnets appears as a sinusoidal distribution in the circumferential direction.

The two linear Hall sensors in the first group of Hall elements and the second group of Hall elements which are respectively arranged corresponding to the plurality of pairs of pole magnets of the middle ring and the inner ring are arranged at an included angle of 90 degrees. The principle of detecting the magnetic signal of the inner or intermediate ring magnet using two linear hall sensors is described below in connection with fig. 5 and 6.

Fig. 5 shows a schematic diagram of signal detection of two linear hall sensors in an embodiment of the present application.

Fig. 6 shows a schematic diagram of detection signals of two linear hall elements in an embodiment of the present application.

The magnet rotates along with the rotating shaft for one circle, the magnetic field change at any point in the space where the magnet is positioned is regular, the change can be converted into sine and cosine electric signals by using two linear Hall sensors with the electric angle difference of 90 degrees, and the frequency of the electric signal change is the same as the frequency of the magnetic pole rotation. As shown in fig. 5 and 6, for the 3-pole inner ring magnet, the third linear hall sensor 121 and the fourth linear hall sensor 122 detect three periods of sine and cosine signals, respectively, i.e., a set of detection signals, for one revolution of the magnet. The first set of detection signals is obtained by a first set of hall elements arranged in an intermediate loop. A second set of detection signals is obtained by a second set of Hall elements arranged in the inner ring.

In the practical process, the two hall arrangement modes are usually arranged by adopting an included angle with an electric angle of 90 degrees. However, the two hall method is difficult to eliminate errors due to machining or assembly, and also difficult to suppress for harmonic errors existing in the magnetic field. The number of the Hall is increased or the Hall is symmetrically arranged, and the main effect is that the mechanical error is reduced by using a symmetrical counteracting mode, and meanwhile, harmonic components can be counteracted. Therefore, the three-Hall arrangement mode is arranged on the multi-pair pole magnet of the outer ring, and meanwhile, the three Hall electric angles can obtain higher calculation accuracy when 120 degrees.

The third group of Hall elements are arranged adjacent to the outer ring multi-pair pole magnets, and three linear Hall sensors are arranged at intervals at an included angle of 120 DEG in electrical angle. The principle of detecting magnetic signals of the outer ring multi-pair pole magnets by three linear hall sensors is described below in connection with fig. 7-10.

Fig. 7 shows a schematic diagram of signal detection of three linear hall sensors in an embodiment of the present application.

Fig. 8 shows a schematic diagram of detection signals of three linear hall sensors in an embodiment of the present application.

Fig. 9 shows a schematic diagram of eliminating zero drift using three hall signals in an embodiment of the present application.

Fig. 10 shows a schematic diagram of synthesizing two-phase hall signals in an embodiment of the present application.

According to the principle, it is easy to know that the magnetic field change can be converted into sine and cosine electric signals by using three linear Hall sensors with 120-degree electric angle difference. As shown in fig. 7 and 8, for a group of multi-pole magnets having 6 pairs of poles in the outer ring, the magnets rotate one revolution, and the fifth, sixth and seventh linear hall sensors 131, 132 and 133 detect six periods of sine and cosine signals, respectively, that is, original three-phase hall signals. The original three-phase Hall signals here respectively adopt U in FIG. 9 ₁ 、U ₂ 、U ₃ Representation is made and U ₁ A detection signal corresponding to the fifth linear hall sensor 131; u (U) ₂ A detection signal corresponding to the sixth linear hall sensor 132; u (U) ₃ Corresponds to the detection signal of the seventh linear hall sensor 133.

Due to problems of hall arrangement, mechanical assembly and the like,original three-phase hall signal U ₁ 、U ₂ 、U ₃ Superimposed with some error signals, the components U being in phase difference of 90 DEG between the two phases _d 、U _q At this time, zero drift occurs with a high probability.

Therefore, the acquired original three-phase hall signal needs to be subjected to zero drift treatment, and as shown in fig. 9, the zero drift treatment is specifically calculated according to the following formula:

In U ₁ 、U ₂ 、U ₃ Is an original three-phase Hall signal; u (U) _shift Is the signal drift amount; u's' ₁ 、U′ ₂ 、U′ ₃ And the three-phase Hall voltage signals after the drift amount are removed.

Then synthesizing the three-phase Hall voltage signals without zero drift into U with two phase differences of 90 DEG _d 、U _q As shown in fig. 10, the following formula is specifically used for conversion:

wherein alpha is the included angle between the electric angle of the detection signal of any one of the linear Hall sensors in the third group of Hall elements and the horizontal direction, U _d 、U _q The two-phase hall voltage signal is the corrected third group detection signal.

At this time, the corrected third group of detection signals with the two-phase difference of 90 ° can be approximately regarded as sine and cosine detection signals acquired by the two linear hall sensors. For convenience of the following text, the third group of hall elements is approximately regarded as two linear hall sensors arranged at an included angle of 90 ° in electrical angle.

Of course, the inner ring and the middle ring of the present application may also adopt a three hall sensor arrangement to improve measurement accuracy, and then the collected detection signal is converted into a detection signal with a two-phase difference of 90 ° by using the above formula.

In step S420, the first set of detection signals, the second set of detection signals, and the modified third set of detection signals are respectively subjected to angle calculation to obtain a first electrical angle value, a second electrical angle value, and a third electrical angle value.

After the sine and cosine signals are obtained by using the linear Hall sensor, a digital voltage value with a certain number of bits can be obtained through an A/D conversion circuit. That is, the first set of voltage values, the second set of voltage values, or the third set of voltage values are obtained after a/D conversion is performed on the first set of detection signals, the second set of detection signals, or the modified third set of detection signals, respectively. The digital voltage value at this time has a certain relation with the measured angle value of the encoder, but is not the measured angle value of the encoder, and an angle calculation is required.

For the signals of each group of magnetic poles, the positions of the two linear Hall sensors are different by 90 degrees in space, so that the sine and cosine signals output by the two linear Hall sensors are different by 90 degrees in phase. In this case, the phase-advanced signal is regarded as a sine signal, and the phase-retarded signal is regarded as a cosine signal. The tangent value of the point signal can be obtained by dividing the sine signal by the cosine signal, and then the electric angle value of the point can be obtained by performing arctangent processing on the tangent value.

Since the interval of the tangent function is [ -90 DEG, 90 DEG ], the direct angle calculation according to the above procedure will lead to the interval error of the angle calculation. Therefore, the problem of interval error needs to be solved by an interval partitioning method, that is, an electrical angle interval where the first set of detection signals or the second set of detection signals or the modified third set of detection signals are located is obtained according to the positive and negative polarities and the numerical magnitudes of the voltage values in the first set of voltage values or the second set of voltage values or the third set of voltage values.

Taking the angular resolution of a set of magnetic poles as an example, 360 ° of the set of magnetic poles may be divided into 8 equal-length sections at 45 ° intervals. The position of the Hall signal at the moment is judged by judging the magnitude and the positive and negative of the voltage values detected by the two linear Hall elements, and the realization principle of the inter-partition arc tangent algorithm is shown in the following table 1. Wherein VA and VB are linear Hall detection signals with phase difference of 90 degrees.

TABLE 1 division of angle intervals

Through the division of the angle interval, the conversion from the signal collected by the Hall element to the angle signal can be realized, and the range of the converted electric angle interval is [0 DEG, 360 DEG ].

For the multi-pair magneto-electric encoder, according to the positive and negative properties and the numerical values of the voltage values in the first group of voltage values, the second group of voltage values and the third group of voltage values, the angle interval where the first group of detection signals, the second group of detection signals and the modified third group of detection signals are located can be obtained. According to the angle interval, the first electrical angle value, the second electrical angle value and the third electrical angle value can be obtained by adopting an arctangent algorithm on the first group of voltage values or the second group of voltage values or the third group of voltage values according to the table 1. The electric angle value herein refers to an electric angle value of a single pair of magnetic pole periods, which is simply referred to as a single period electric angle value.

In the angle measurement process, three groups of multiple pairs of pole magnets simultaneously rotate along with the rotating shaft, and the linear Hall element is kept static and is used for receiving a magnetic field signal generated by the magnetic poles in the rotating process. The electric angle value of the single-pair magnetic pole period of the measured magnet can be obtained by processing the induction signal of the linear Hall through the arctangent table lookup method. After the single-period electric angle value is determined, the magnetic pole interval where the single-period electric angle value is located is determined, and then the absolute angle values detected by the multi-pair magnetic-electric encoder can be finally obtained.

In the absolute angle detection method of the multi-pair-pole magnetoelectric encoder, an initial mechanical angle with certain precision is determined according to two groups of detection signals of the inner ring magnet and the middle ring magnet, then the initial mechanical angle is utilized to calibrate the specific magnetic pole interval of the outer ring magnet in which the single-period electrical angle value of the outer ring magnet is currently positioned, and finally the mechanical angle of the multi-pair-pole magnetoelectric encoder is calculated by utilizing a calculation formula of the mechanical angle value. The mechanical angle referred to in this application is also referred to as absolute angle.

Next, the present application will describe in detail how to obtain an initial mechanical angle with a certain accuracy.

In this application, the calculation of the initial mechanical angle may be calculated according to the following formula:

θ _{_single} ＝N _m ×360°/m+θ _m m formula (3) wherein N _m ∈[0，m-1]Or (b)

θ _{_single} ＝(N _m -1)×360°/m+θ _m M formula (4) wherein N _m ∈[1，m]

In θ _{_single} For an initial mechanical angle, θ _m For single period electrical angle values measured by linear hall sensors on the first plurality of pairs of pole magnets 110, N _m For theta _m A first magnetic pole section; m is the pole pair number of the first plurality of pole magnets 110. Here, θ _m Also referred to as a first electrical angle value.

For the encoder shown in fig. 2-3, there is an angular difference θ between the starting pole mounting positions of the inner ring magnet and the intermediate ring magnet _x The initial mechanical angle can also be expressed as:

θ _{_single} ＝N _n ×360°/n+θ _n /n+θ _x formula (5) wherein N _n ∈[0，n-1]Or (b)

θ _{_single} ＝(N _n -1)×360°/n+θ _n /n+θ _x Formula (6) wherein N _n ∈[1，n]

In θ _{_single} For an initial mechanical angle, θ _n For single period electrical angle values, N, measured by linear Hall sensors on the second plurality of pairs of pole magnets 120 _n For theta _n The second magnetic pole section is positioned; n is the pole pair number of the second plurality of pole magnets 120. θ _n Also referred to as a second electrical angle value.

Therefore, on the basis that the first electrical angle value or the second electrical angle value has been obtained, the initial mechanical angle value can be calculated according to the above-described formula (3) -formula (6) as long as the corresponding magnetic pole section thereof is determined.

In step S430, a first magnetic pole section corresponding to the first electrical angle value is determined according to the magnetic pole pair number m of the first plurality of pairs of pole magnets 110, the magnetic pole pair number n of the second plurality of pairs of pole magnets 120, the first electrical angle value, and the second electrical angle value.

When the linear hall sensors on the first plurality of pairs of pole magnets 110 measure the same single-period electrical angle value twice, the two single-period electrical angle values measured by the linear hall sensors on the corresponding second plurality of pairs of pole magnets 120 are different, so that the number of pole pairs, i.e. the pole intervals, where the single-period electrical angle of the first plurality of pairs of pole magnets 110 is currently located can be distinguished.

With the encoder magnet structure 100 provided herein, in the case that the greatest common divisor of the magnetic pole pairs m, n of the first and second pluralities of pole magnets 110, 120 is 1, i.e., mutually prime, each pair of poles of the first plurality of pole magnets 110 has a corresponding non-repeating magnetic pole portion of the second plurality of pole magnets 120. The following is a proof method.

Assuming that there is a positive integer N _m1 ，N _m2 ，N _n1 ，N _n2 ，N _m1 ≠N _m2 The following formula is established:

(N _m1 -1)×360°/m+θ _m /m＝(N _n1 -1)×360°/n+θ _n /n+θ _x

(N _m2 -1)×360°/m+θ _m /m＝(N _n2 -1)×360°/n+θ _n /n+θ _x formula (7)

Wherein θ _m For single period electrical angle values measured by linear hall sensors on the first plurality of pairs of pole magnets 110, N _m1 ，N _m2 ∈[1，m]For two times of measuring theta _m The corresponding first magnetic pole interval; θ _n For single period electrical angle values, N, measured by linear Hall sensors on the second plurality of pairs of pole magnets 120 _n1 ，N _n2 ∈[1，n]For two times of measuring theta _n The corresponding second magnetic pole section; θ _x Is the difference in mounting angle between the starting points of a pair of poles in the two sets of magnets.

Subtracting the two formulas in the formula (7) can obtain:

since m and N are mutually equal, and N _m1 -N _m2 ∈[1，m-1]Therefore, equation (8) is constantly not established, i.e., equation (7) is constantly not established.

Further from equation (8):

equation (9) for any different N _m And corresponding N thereof _n Neither is true. That is, equation (9) is not true for the magnetic pole pairs in the different first plurality of pole magnets 110 and the corresponding magnetic pole pairs in the second plurality of pole magnets 120. It can be demonstrated that when the linear hall sensors on the first plurality of pairs of pole magnets 110 measure the same single-cycle electrical angle value, the two single-cycle electrical angle values measured by the linear hall sensors on the corresponding second plurality of pairs of pole magnets 120 are different. Thus, the magnetic pole section where the first angle value is currently located can be resolved by the positional relationship between the first plurality of pairs of pole magnets 110 and the second plurality of pairs of pole magnets 120.

Is obtained by combining the formula (3) and the formula (5):

it can be seen that the right value of the expression is a single-period electrical angle value without the current sampling point, the magnitude of the value is only dependent on the magnetic pole interval numbers of the inner ring and the middle ring, the value is determined by the number of the magnetic pole interval group (N _m ，N _n ) In the fixed case, the value is a constant, and the constant is the characteristic value of the mapping interval number group.

Is provided withAnd defines it as a pole position feature value. As can be seen from the equation (10), when the number of the pole pairs of the first and second pluralities of pole magnets 110 and 120 is unchanged, the characteristic value of the pole position is unchanged. When at least one of them is changed, the magnetic pole position characteristic value is also changed, otherwise, the equation (9) is established, and contradicts the precondition of mutual quality of the magnetic pole pairs. Therefore, the magnetic pole section where the current electrical angle is located can be determined by calculating the magnetic pole position characteristic value.

When theta is as _x If not equal to 0, that is, if the magnetic pole starting points of a certain pair of the inner ring and the intermediate ring magnet are not overlapped, the magnetic pole position characteristic values λ cannot be overlapped by changing the coordinate starting points, and m+n different values are shared. As shown in fig. 11.

Fig. 11 shows a schematic diagram of the number of magnetic pole position feature values in the embodiment of the present application.

In fig. 11, the middle ring magnet has m pairs of poles, m being 5, so 5 boxes are used to represent a planar expansion illustration of 5 pairs of poles. The inner ring magnet has n pairs of poles, n takes 3, and after the inner ring magnet is subjected to plane expansion, 3 vertical lines are introduced into 5 boxes. Since θx+.0, the total of m+n+1 lines will be divided into m+n shares. That is, there are 8 different values of the position characteristic value for an encoder of one 5-pole magnet and one 3-pole magnet. By analogy, for an encoder with 23 pairs of pole magnets and 19 pairs of pole magnets, there are 42 different values for the pole position characteristic values.

After the inner ring and the middle ring magnet are installed, θ _x If the value of m+n is already determined, then the value of m+n is already constant. From the number m of the magnetic pole pairs of the first plurality of pole magnets 110 and the number n of the magnetic pole pairs of the second plurality of pole magnets 120, and the first electrical angle value and the second electrical angle value, a magnetic pole position characteristic value corresponding to the first plurality of pole magnets 110 can be determined. Taking the multi-pair magneto-electric encoder structure shown in FIG. 2 as an example, θ _x When=40° the rotation direction of the magnets is clockwise, the magnetic pole position characteristic value obtained by calibration and the magnetic pole section on the corresponding first plurality of pairs of pole magnets 110 are shown in table 2.

Table 2 corresponding relationship between lambda value and magnetic pole interval of first multi-pair pole magnet

The identification of the magnetic pole position can be completed through the corresponding relation between lambda and the magnetic pole section in table 2, namely, the first magnetic pole section where the first electric angle value is currently located is calculated according to the characteristic value of the magnetic pole position.

In step S440, an initial mechanical angle θ formed by the first and second pairs of pole magnets 110, 120 is determined based on the first pole segment, the number m of pole pairs of the first plurality of pole magnets 110, and the first electrical angle value _{_single} 。

After determining the first electrical angle value and the first pole section in which the electrical angle value is located, the initial mechanical angle formed by the first plurality of pairs of pole magnets 110 and the second plurality of pairs of pole magnets 120 may be obtained according to equation (3).

In step S450, the third magnetic pole interval where the third electrical angle value is currently located is calibrated according to the initial mechanical angle.

On the premise that the initial mechanical angle is obtained, the initial mechanical angle can be used for calibrating a third magnetic pole interval where a third electric angle value of the outer ring magnet is currently located.

In the present application, the third magnetic pole section N _p The following correspondence exists with the initial mechanical angle:

N _p ＝INT(θ _{_single} ×p/360)，N _p ∈[0，p-1]

therefore, an index table is established according to the corresponding relation between the initial mechanical angle and the third magnetic pole section, the first column of the index table is the value of the initial mechanical angle, and the second column is the section number of the third magnetic pole section corresponding to the initial mechanical angle. Because the initial mechanical angle is an absolute angle, the value range is [0 DEG, 360 DEG ], the first row of the first row has a first behavior number of 0 and the last row of the first row has a last behavior number of 360.

By way of example, assuming a pole pair number of 5 for the outer ring multi-pair magnets, the initial mechanical angle and corresponding third pole interval obtained by calibration are shown in table 3.

TABLE 3 index Table of the relationship between pole intervals in the initial mechanical Angle and third multiple pairs of pole magnets

Initial mechanical angle θ _{_single}	Magnetic pole interval P
		0	0
1	0
		2	0
3	…
		…	3
358	3
		359	4
360	4

Therefore, only the degree of the initial mechanical angle is determined, and the numerical value of the third magnetic pole interval can be obtained by looking up a table. But it should be noted that: in the case of tabulation, the number of rows of the column of the initial mechanical angle needs to be set to be far greater than the number of pole pairs of the third plurality of pairs of pole magnets 130, so that the accuracy of the magnetoelectric encoder can be greatly improved.

For example: in table 3, the number of rows of the column of the initial mechanical angle is 360 rows, and the number of pole pairs of the third plurality of pole magnets 130 is only 5, satisfying the requirement of being far larger than the number of pole pairs of the third plurality of pole magnets 130.

Assuming that the number of pole pairs of the third plurality of pairs of pole magnets 130 is 360, the number of rows of the column of the initial mechanical angle may be set to 360 rows, i.e., each degree of the initial mechanical angle corresponds to a pole interval of one third plurality of pairs of pole magnets 130; similarly, the number of rows in the column of the initial mechanical angle may be set to 3600 rows, such that every 0.1 degrees of the initial mechanical angle corresponds to a pole segment of the third plurality of pairs of pole magnets 130, and such that the accuracy of the magneto-electric encoder is improved by a factor of 10. Accordingly, the precision can be improved by 20 times, 30 times, even 100 times or more, which is the meaning that the number of lines is far greater than the number of pole pairs.

In step S460, the absolute angles of the pairs of the multi-pair magneto-electric encoders are determined according to the following formula using the determined third magnetic pole interval and the third electric angle value and the magnetic pole pair number p of the third pairs of the magnetic poles 130:

θ＝N _p ×360°/p+θ _p /p

wherein θ is the absolute angle of the output of the multi-pair magneto-electric encoder, N _p For a third electrical angle value theta _p Number N of magnetic pole interval where current is located _p ∈[0，p-1]。

Based on the above, the multi-pair magneto-electric encoder can output absolute angles of two accuracies, namely θ ₁ And theta ₂ Wherein θ ₁ For a high precision absolute angle θ determined by the first plurality of pairs of pole magnets 110 and the second plurality of pairs of pole magnets 120 _{_single} At this time theta ₁ ＝θ _{_single} ；θ ₂ To utilize the obtained high-precision absolute angle theta ₁ Combining the third mostUltra-high precision absolute angle θ determined by antipodal magnet 130, at which θ ₂ =θ; in practical combination application of the multi-pair-pole magnetoelectric encoder and the servo motor, the detection precision of the multi-pair-pole magnetoelectric encoder is limited by the highest rotating speed of the servo motor, namely: taking 8000rpm as an example of the maximum rotation speed allowed by the multi-pair magneto-electric encoder, when the maximum rotation speed of the servo motor is 6400rpm, the multi-pair magneto-electric encoder can maintain the ultra-high precision absolute angle output capability, namely the output theta ₂ The method comprises the steps of carrying out a first treatment on the surface of the When the maximum rotation speed of the servo motor is greater than 9600rpm, the electric signal frequency of the multi-pair-pole magneto-electric encoder cannot follow the maximum rotation speed of the servo motor, so that the output theta ₂ Failure.

In view of this, due to the existence of the limit of the maximum rotation speed of the servo motor, the absolute angle of the final output of the multi-pair-pole magnetoelectric encoder is as follows ₁ And theta ₂ There is an angle switching output relationship of the following formula:

/>

in θ ₃ Absolute angles which are finally output by the multi-pair-pole magneto-electric encoder;

omega is the current highest rotating speed of the servo motor;

ω ₀ 0.8 times of the maximum rotation speed allowed by the ultra-high precision absolute angle output by the multi-pair polar magneto-electric encoder, namely:wherein T represents a control period of the control instruction, and k represents a kth control period;

ω ₁ 1.2 times of the highest rotation speed allowed by the ultra-high precision absolute angle output by the multi-pair polar magneto-electric encoder, namely:wherein T represents a control period of the control instruction, and k represents a kth control period;

in addition, in order to understand the above-mentioned angle switching selection output relationship of absolute angles, the present application further provides a linear schematic diagram as shown in fig. 12, and it can be seen from the combination of formula (11) and fig. 12:

when omega is less than or equal to omega ₀ At the time, the absolute angle theta of the final output of the multi-pair magneto-electric encoder ₃ ＝θ ₂ ；

When omega is greater than omega ₀ And at the same time less than omega ₁ At the time, the absolute angle theta of the final output of the multi-pair magneto-electric encoder ₃ Will combine theta ₂ And theta ₁ Simultaneously taking values;

when omega is greater than or equal to omega ₁ At the time, the absolute angle theta of the final output of the multi-pair magneto-electric encoder ₃ ＝θ ₁ 。

Therefore, based on the above, the final absolute angles output by the multiple pairs of electrode magneto-electric encoders can be obtained, and then the accurate control of the servo system can be realized by combining the working principle of the servo system.

As shown in fig. 1, in the working process of the high-precision servo control system, a plurality of pairs of magneto-electric encoders detect the rotation angle of a motor shaft of a servo motor so as to obtain the rotation angle or position of the motor shaft; and the current signals collected by the current sensor are transmitted to the control unit, six paths of PWM signals are calculated and output through the processing of the control unit, and the work of the IPM inverter circuit is driven, so that the controller outputs three-phase voltage signals for driving the servo motor to work, namely working instructions, after receiving the working instructions, the servo driver outputs driving signals matched with the load of the servo motor according to the load requirements of the servo motor, and after receiving the driving signals, the servo motor drives the actuating mechanism to realize accurate control. In this example, the executing mechanism may be any one of a screw rod, a guide rail, a speed reducer, a two-dimensional turntable and a numerical control operation platform.

FIG. 13 is a flowchart of a control method of a high-precision servo control system in an embodiment of the present application.

As shown in fig. 13, the control method of the high-precision servo control system includes:

s1: the current sensor acquires an input current signal of the servo motor;

s2: detecting and outputting angle information of the servo motor by a plurality of pairs of pole magneto-electric encoders;

s3: the controller receives the data, processes the data and then outputs a voltage signal for the servo motor to work;

s4: the servo driver receives the working voltage signal of the servo controller and outputs a driving signal of the servo motor according to the load requirement of the servo motor;

s5: the servo motor receives the driving signal and drives the actuating mechanism to move so as to realize precise control of the motion state of the actuating mechanism.

FIG. 14 shows a first sub-flowchart of a control method of a high-precision servo control system in an embodiment of the present application.

As shown in fig. 14, the plurality of pairs of pole magneto-electric encoders detect and output angle information S2 of the servo motor, including:

s21: collecting rotating magnetic field information generated by driving a magnet when a servo motor rotates through three groups of linear Hall elements;

s22: amplifying and converting signals through an amplifier and an A/D converter;

s23: and outputting actual angle information of the rotation of the servo motor through a table lookup and calculation program.

As shown in fig. 15, the controller receives data, processes the data, and outputs a voltage signal S3 for the operation of the servo motor, and includes:

s31: receiving a current signal detected by a current sensor, and outputting a digital current signal after A/D sampling;

s32: receiving and outputting actual angle information of the rotation of the servo motor output by the multi-pair-pole magneto-electric encoder;

s33: receiving an instruction signal of an upper computer and rotation angle information of a servo motor shaft, calculating to obtain a current instruction and outputting the current instruction;

s34: receiving a current instruction and a digital current signal, calculating to obtain a duty ratio control signal of the three-phase voltage, and outputting the duty ratio control signal;

s35: and receiving the three-phase voltage duty ratio control signal, generating a PWM signal with six paths, and driving the IPM inverter circuit to work, so that a controller outputs a working instruction for driving the servo motor to work.

Finally, it should be noted that: the foregoing description is only illustrative of the preferred embodiments of the present invention, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described, or equivalents may be substituted for elements thereof, and any modifications, equivalents, improvements or changes may be made without departing from the spirit and principles of the present invention.

Claims

1. High accuracy servo control system, its characterized in that: comprises a servo motor;

2. The high precision servo control system of claim 1 wherein: the multi-pair pole magnetoelectric encoder selects and outputs the absolute angle with high precision and/or ultra-high precision under the rotating speed range of the servo motor through the following formula:

in θ ₃ The final absolute angle output by the multi-pair-pole magneto-electric encoder; θ ₁ Is composed of the first multiple pairs of pole magnets and the firstThe high-precision absolute angle determined by the two multi-pair pole magnets; θ ₂ To utilize the obtained high-precision absolute angle theta ₁ Combining the ultra-high precision absolute angles determined by the third multi-pair pole magnet; omega is the current rotating speed of the servo motor; omega ₀ 0.8 times of the maximum rotation speed allowed when the ultra-high precision absolute angle is output for the multi-pair magneto-electric encoder; omega ₁ 1.2 times of the highest rotation speed allowed when the ultra-high precision absolute angle is output for the multi-pair magneto-electric encoder; t represents a control cycle of the control instruction, and k represents a kth control cycle.

3. The high precision servo control system of claim 1 wherein: the servo motor is a permanent magnet synchronous servo motor.

4. The high precision servo control system of claim 1 wherein: m and n are prime numbers and mn < 23X 19.

5. The high precision servo control system of claim 1 wherein: the first set of detection signals includes: the first linear Hall sensor and the second linear Hall sensor output a first detection signal and a second detection signal according to magnetic pole signals of the first multi-pair pole magnets; the phase difference between the first detection signal and the second detection signal is 90 degrees;

6. The high precision servo control system of claim 1 wherein: the modified third set of detection signals includes: the fifth linear Hall sensor, the sixth linear Hall sensor and the seventh linear Hall sensor output detection signals of d axis and q axis according to the magnetic pole signals of the third multi-pair pole magnet; the method comprises the steps that a fifth linear Hall sensor, a sixth linear Hall sensor and a seventh linear Hall sensor acquire magnetic pole signals of a third multi-pair pole magnet to obtain an original three-phase Hall signal with 120-degree phase difference, wherein the original three-phase Hall signal is a fifth detection signal, a sixth detection signal and a seventh detection signal; and then, performing zero drift processing on the obtained original three-phase Hall signals, and outputting detection signals of d-axis and q-axis with 90-degree phase difference.

7. The high precision servo control system of claim 1 wherein: the first linear hall sensor is aligned with the third linear hall sensor and the fifth linear hall sensor at one end.

8. The high precision servo control system of claim 1 wherein: the third multi-pair pole magnets are located on the outermost ring, the second multi-pair pole magnets are located on the innermost ring, the first multi-pair pole magnets are located between the third multi-pair pole magnets and the second multi-pair pole magnets, and an angle difference exists between initial magnetic pole installation positions of the first multi-pair pole magnets and the second multi-pair pole magnets.

9. The high precision servo control system of claim 1 wherein: the magnetization directions of the first multi-pair pole magnets and the second multi-pair pole magnets are consistent with the radial direction or the axial direction of the rotating shaft of the servo motor; the magnetization direction of the third multi-pair pole magnet is consistent with the radial direction or the axial direction of the rotating shaft of the servo motor.

10. The high precision servo control system of claim 1 wherein: the actuating mechanism is any one of a screw rod, a guide rail, a speed reducer, a two-dimensional turntable and a numerical control operation platform.