Winding multiplexing motor rotation angle self-sensing system and method based on eddy current effect

Abstract

This invention discloses a winding reuse-based self-sensing system and method for motor rotation angle based on the eddy current effect, belonging to the field of micro-motor sensing and control technology. It includes a brushless coreless motor rotor, a non-magnetic conductive strip disposed on the rotor surface, a multi-pole coil winding, and a high-frequency measurement and decoupling module connected to the winding. During operation, the high-frequency module injects a high-frequency excitation signal into the multi-pole coil winding; as the rotor rotates, eddy current coupling occurs between the conductive strip and the coil winding, causing the equivalent impedance of the coil winding to change regularly with the rotation angle. By isolating and decoupling and extracting the impedance change signal, combined with the timing relationship, the real-time rotation angle of the motor can be calculated. This invention cleverly reuses the original winding resources of the motor, eliminating the need for an external traditional encoder, and has advantages such as extremely high spatial integration, non-contact and wear-free operation, and resistance to low-frequency electromagnetic interference.

Description

Technical Field

[0001] This invention relates to the field of micro motor sensing and control technology, and in particular to a self-sensing system and method for the rotation angle of a winding multiplexed motor based on the eddy current effect. Background Technology

[0002] Brushless coreless motors possess advantages such as low rotational inertia, no cogging effect, fast response speed, high efficiency, and small size, and are widely used in precision actuators, medical devices (such as surgical robots), micro handheld devices, aerospace, and high-end servo systems. In these applications, accurately acquiring the motor rotor angle or position information is a necessary prerequisite for achieving high dynamic closed-loop control, precise commutation, and accurate positioning.

[0003] In existing technologies, the rotation angle measurement of brushless coreless motors typically relies on external Hall sensors, magnetic encoders, or photoelectric encoders. While Hall sensors offer simple structure, their angular resolution is limited. Photoelectric encoders offer high accuracy but are bulky, expensive, and complex to assemble, severely hindering the miniaturization of motor systems. Magnetic encoders, suitable for rotation measurement, are difficult to install within the space-constrained coreless motor and are highly susceptible to low-frequency electromagnetic interference from the strong magnetic fields of the motor's stator and rotor. On the other hand, eddy current-based sensing technology offers advantages such as non-contact operation, contamination resistance, high frequency response, and ease of miniaturization. However, current eddy current displacement or angle sensors are mostly independently packaged external devices. To obtain high-resolution rotation angle information without significantly increasing the axial or radial dimensions of the motor, key technical challenges remain to be addressed in this field. These challenges include how to deeply integrate the eddy current sensing mechanism with the motor's original physical structure, and how to overcome the interference of strong electric drive signals (such as low-frequency PWM pulse signals) on weak sensing signals, achieving effective decoupling between drive and sensing. Summary of the Invention

[0004] To address the above technical problems, this invention provides a winding multiplexing motor rotation angle self-sensing system and method based on the eddy current effect, which solves the problems of existing technologies relying on external encoders, resulting in complex structures, increased size, and difficulty in achieving stable built-in measurements under high-power drive environments.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A winding multiplexing motor rotation angle self-sensing system based on eddy current effect includes: a brushless coreless motor rotor, a non-magnetic conductive strip disposed on the surface of the rotor, a multi-pole coil winding, and a motor drive module and a high-frequency measurement and decoupling module both connected to the multi-pole coil winding; wherein, the high-frequency measurement and decoupling module injects a high-frequency excitation signal into the multi-pole coil winding and isolates the low-frequency drive signal output by the motor drive module; when the rotor rotates, eddy current coupling occurs between the non-magnetic conductive strip and the multi-pole coil winding, causing the equivalent impedance parameter of the multi-pole coil winding to change with the rotation angle; the high-frequency measurement and decoupling module extracts the change signal of the equivalent impedance parameter and calculates the rotor rotation angle information based on the signal timing relationship.

[0006] Furthermore, the non-magnetic conductive strip is disposed on the outer circumferential surface of the permanent magnet rotor.

[0007] Furthermore, the rotor is cylindrical in shape and fixedly connected to the central shaft, rotating around the central shaft.

[0008] Furthermore, the non-magnetic conductive strip is a strip structure formed of copper foil, copper plating, aluminum foil, aluminum plating, or a non-ferromagnetic highly conductive material.

[0009] Furthermore, the high-frequency measurement and decoupling module includes a high-frequency isolation circuit and a high-frequency impedance measurement circuit; the high-frequency isolation circuit is connected between the multipole coil winding and the high-frequency impedance measurement circuit to prevent the drive current from entering the high-frequency impedance measurement circuit, while allowing the transmission of the high-frequency excitation signal and the high-frequency carrier signal carrying impedance change information.

[0010] Furthermore, the high-frequency impedance measurement circuit includes a high-frequency excitation generation unit, a signal conditioning unit, and a demodulation unit; the demodulation unit is used to extract the amplitude or phase change characteristics in the high-frequency carrier signal to obtain the equivalent impedance parameter.

[0011] Furthermore, the width of the non-magnetic conductive strip is less than or equal to the pole pitch of two adjacent multipole coil windings.

[0012] Furthermore, the multipole coil winding is equivalent to multiple windings along the circumferential direction.

[0013] This invention also provides a self-sensing method for the rotation angle of a winding-multiplexed motor based on the eddy current effect, applied to the above-mentioned system, comprising the following steps: S1, arranging a non-magnetic conductive strip on the outer circumferential surface of the motor rotor; S2, injecting a high-frequency excitation signal into the multi-pole coil winding of the motor stator through a high-frequency measurement and decoupling module, and isolating the low-frequency drive signal of the motor; S3, during motor rotation, extracting the equivalent impedance parameter change signal of the multi-pole coil winding caused by the eddy current coupling effect through the high-frequency measurement and decoupling module; S4, calculating the rotor rotation angle information based on the characteristic parameters of the change signal and the signal timing relationship.

[0014] Furthermore, in step S4, the characteristic parameters of the changing signal include one or more of amplitude, phase, peak and valley positions, zero crossing points, and waveform characteristic points; the calculation of the rotor angle information adopts at least one of peak and valley counting, table lookup fitting, feature point identification, or phase-locked tracking algorithm.

[0015] Compared with existing technologies, this invention has at least the following advantages: 1. Extreme structural integration: It eliminates the need for additional photoelectric encoders or external magnetic targets, cleverly reusing the motor's own multi-pole coil windings as stator detection probes, achieving "zero axial / radial volume increase" for angle sensing, making it extremely suitable for miniaturized and lightweight systems. 2. Excellent anti-interference capability: By introducing a high-frequency measurement and decoupling mechanism, it effectively resists interference from the strong magnetic field inside the motor and the PWM drive current by utilizing the frequency domain difference between the high-frequency excitation magnetic field (MHz level) and the low-frequency motor drive magnetic field (kHz level). 3. High reliability and environmental adaptability: Employing a non-contact eddy current sensing mechanism completely eliminates mechanical wear and provides strong immunity to harsh environments such as dust, oil, and humidity. 4. High flexibility: The parameters (width, quantity, spacing) and arrangement rules (equal spacing or pseudo-random coding) of the conductive strips can be flexibly designed to meet diverse application needs from relative position incremental measurement to absolute position measurement. Attached Figure Description

[0016] Figure 1(a) is a three-dimensional structural schematic diagram of the self-sensing device for the winding reuse type motor rotation angle of the present invention;

[0017] Figure 1(b) is a schematic diagram of the radial cross-section and circumferential distribution of the conductive strip of the device of the present invention;

[0018] Figure 2 This is a schematic diagram of the circuit connection of the device of the present invention;

[0019] Figure 3 This is a schematic diagram showing the relative positional relationship between the non-magnetic conductive strip and the multipole coil winding as the device operates along the circumferential direction.

[0020] Figure 4A schematic diagram illustrating the timing relationship established based on the equivalent impedance change signal output by the multipole coil winding;

[0021] Figure 5(a) shows the finite element simulation cloud map of the magnetic field distribution when the conductive strip is in different positions relative to the multipole coil winding;

[0022] Figure 5(b) is a graph showing the change in equivalent impedance of adjacent coil windings extracted from the simulation.

[0023] Figure 5(c) shows the inductance difference of the equivalent impedance change of adjacent coil windings extracted by simulation.

[0024] Figure 6(a) is a graph showing the change in equivalent impedance of adjacent coil windings obtained from experimental measurements;

[0025] Figure 6(b) shows the inductance difference diagram of the equivalent impedance change of adjacent coil windings obtained by experimental measurement.

[0026] The annotations in the attached figures are explained as follows:

[0027] 1: Conductive strip; 2: Rotor; 3: Multipole coil winding; 4: Shaft. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, this invention adopts the following technical solution.

[0029] As shown in Figures 1(a) and 1(b), the self-sensing system for winding multiplexed motor rotation angle based on eddy current effect disclosed in this embodiment includes: a rotor 2 of a brushless coreless motor, a multi-pole coil winding 3, a non-magnetic conductive strip 1 disposed on the outer surface of the rotor, and a rotating shaft 4. Figure 1(a) shows a three-dimensional perspective view of the device, and Figure 1(b) shows a radial cross-section and a schematic diagram of the circumferential distribution of the conductive strip when viewed along the motor axial direction.

[0030] In this embodiment, the rotor 2 is cylindrical in shape and fixedly connected to the central shaft 4. A multi-pole coil winding 3 is disposed on the outer circumference of the rotor, forming the stator winding structure of the hollow cup motor. To achieve angle sensing, a non-magnetic conductive strip 1 is axially disposed on the outer circumferential surface of the rotor 2. The conductive strip 1 can be formed using copper foil, aluminum foil, copper plating, aluminum plating, or a non-ferromagnetic highly conductive material.

[0031] As shown in Figure 1(b), the multi-pole coil winding 3 can be equivalent to multiple windings along the circumferential direction, as illustrated in the figure as the 1st winding, 2nd winding, 3rd winding, ..., nth winding. Here, "n" represents the number of windings in the motor and is not limited to a fixed value. The conductive strip 1 is fixed to the rotor surface and rotates synchronously with the rotor. The relative position of the multi-pole coil winding 3 to the conductive strip on the rotor surface in space also changes accordingly.

[0032] As a core implementation detail of the present invention, such as Figure 2 As shown, the multi-pole coil winding 3 is connected to both the motor drive module and the high-frequency measurement and decoupling module. During normal motor operation, the motor drive module outputs a low-frequency high-voltage drive signal (such as PWM pulse width modulation current) to the multi-pole coil winding 3. To reuse the winding for sensing without affecting normal motor operation, the high-frequency measurement and decoupling module includes a high-frequency isolation circuit (e.g., an LC frequency division multiplexing network or a high-pass / low-pass filter network). This isolation circuit effectively blocks low-frequency high-voltage drive current from entering the high-frequency impedance measurement section, while allowing megahertz (MHz) level high-frequency excitation signals to be injected into the coil and successfully extracting the high-frequency carrier signal carrying eddy current modulation information. This achieves perfect decoupling between the high-voltage drive and the low-voltage sensing, greatly improving the device's electromagnetic interference resistance.

[0033] The basic sensing principle of this invention is to utilize the eddy current effect generated by a non-magnetic conductive strip under the action of a high-frequency alternating magnetic field to modulate the equivalent impedance parameters (including equivalent inductance and equivalent active resistance) of adjacent multipole coil windings. When a conductive strip rotates to the area directly opposite a coil winding, the conductive strip generates strong eddy currents under the penetration of the high-frequency excitation magnetic field, thereby generating an additional reverse magnetic field. Due to the superposition of magnetic fields and the eddy current loss effect, the equivalent inductance of the corresponding coil winding decreases and the equivalent resistance increases. As the conductive strip gradually leaves the area corresponding to the coil winding, the eddy current coupling effect weakens, and the equivalent impedance parameters of the coil winding gradually return to the baseline value.

[0034] like Figure 3 As shown, after unfolding the structure along the circumference of the motor, the spatial correspondence between the conductive strip and multiple multi-pole coil windings can be obtained. In the figure, the conductive strip passes through the 1st winding, the 2nd winding, the 3rd winding, ..., the nth winding in sequence along the rotation direction. Due to the different relative positions of the coil windings and the conductive strip, when the conductive strip sweeps through different winding positions in sequence, the impedance parameter change signals output by each coil winding will exhibit regular time delays or phase differences.

[0035] like Figure 4As shown, taking the equivalent impedance parameters (such as inductance) response curves of the first, second, third, and nth windings as an example, when the rotation angle changes continuously, different multi-pole coil windings will obtain response curves with similar waveform characteristics but staggered on the time axis. The high-frequency measurement and decoupling module extracts the peak and valley values, inflection points, zero-crossing points, or related phase relationships of each curve through demodulation, and can calculate the rotation angle in the following manner.

[0036] Specifically, let the number of multi-pole coil windings equivalently divided along the circumferential direction be... The center angle interval between adjacent windings is:

[0037] ;

[0038] No. The circumferential center angle of each winding is:

[0039] ;

[0040] When the rotor's single-turn rotation angle is At that time, the first The equivalent impedance measured for each winding can be expressed as:

[0041] ;

[0042] in, For the first The equivalent resistance of each winding For the first The equivalent inductance of each winding ω is the angular frequency of the high-frequency excitation signal. Due to the eddy current coupling between the conductive strip and the winding varying with the relative angle, the angular frequency of the excitation signal... The equivalent impedance of each winding can be further expressed as:

[0043] ;

[0044] in, This is the reference impedance when the conductive strip is far from the winding. This represents the impedance change caused by eddy current coupling. The impedance change is related to the conductivity band relative to the first... The angle deviation of each winding is related, that is:

[0045] ;

[0046] in, This represents a periodic response function determined by the conductor strip width, conductivity, winding geometry, air gap distance, and high-frequency excitation frequency. Indicates to Take the mold.

[0047] In one solution method, the current adjacent winding interval of the conductive strip is first determined based on the impedance change of each winding. For example, when the conductive strip is located in the winding... With winding When the interval is between, the local subdivision angle within that interval is defined as:

[0048] ;

[0049] A differential signal is constructed by selecting the changes in equivalent inductance or equivalent impedance of adjacent windings. For example, for adjacent windings... and The normalized difference component is defined as:

[0050] ;

[0051] or:

[0052] ;

[0053] When the conductive strip is from the winding To the winding When moving in a certain direction, It exhibits monotonically changing within the corresponding angular interval, therefore, it can be determined based on the pre-calibrated functional relationship:

[0054] ;

[0055] Obtain the subdivided angle position of the conductive strip within the adjacent winding interval, and further obtain the current single-turn angle:

[0056] ;

[0057] in, It can be obtained through table lookup, curve fitting, polynomial fitting, or piecewise linear interpolation.

[0058] In another solution method, the impedance changes or inductance changes of multiple windings can be combined into a multi-channel eigenvector:

[0059] ;

[0060] or:

[0061] ;

[0062] in, , The feature vectors acquired in real time With pre-calibrated angular feature template By matching, the current single-lap angle can be directly obtained through the minimum error criterion:

[0063] ;

[0064] For continuous rotation processes, the rotation direction can be determined by combining the peak-valley sequence of adjacent sampling times, the order of zero-crossing points, and the phase sequence of multi-channel signals. The number of complete revolutions can then be accumulated using peak-valley counting or phase-locked tracking algorithms. Thus, the continuous cumulative turning angle is obtained:

[0065] ;

[0066] in, To accumulate the total number of laps, This represents the current single-turn rotation angle. Using the above method, the relative angle or continuous cumulative rotation angle of the rotor can be measured solely by utilizing the high-frequency impedance response of the multiplexed winding without the need for an external encoder.

[0067] To verify the modulation effect of the conductive strip on the coil parameters in this invention, this embodiment uses the three-dimensional finite element method to simulate and analyze the magnetic field and eddy current distribution when the conductive strip is in different relative positions. Figure 5(a) shows the finite element simulation cloud map results of the magnetic field distribution when the conductive strip is in different positions relative to the coil winding. It can be seen that when the conductive strip is located in the direction directly opposite the winding, the local magnetic field distribution and the direction of the magnetic field lines are significantly distorted due to the eddy current reaction. Figure 5(b) is a curve of the change of the equivalent impedance parameter (inductance) of adjacent coil windings extracted by simulation. It can be seen intuitively that when the conductive strip is far away from the area directly opposite the coil winding, the eddy current effect weakens and the inductance of the first winding gradually increases. At this time, when the conductive strip is close to the adjacent coil winding, the eddy current effect strengthens and the inductance of the second winding gradually decreases. Moreover, the inductance difference between adjacent coil windings is monotonically changing.

[0068] In practical verification, adjacent winding units in the multi-pole coil winding were also selected as test benchmarks. These units were connected to the high-frequency excitation generation and demodulation unit via a high-frequency isolation circuit. Impedance characteristic data of the coil windings were sampled under low-speed or step-rotation conditions of the rotor. Figure 6(a) shows the curve of the equivalent impedance change of adjacent coil windings obtained from the verification experiment using a self-made multi-pole coil winding. Figure 6(b) shows the inductance difference diagram of the equivalent impedance change of adjacent coil windings obtained from the experiment. As can be seen from the figures, this is highly consistent with the finite element simulation results shown in Figures 5(b) and 5(c), fully demonstrating that the multiplexed winding eddy current coupling mechanism proposed in this invention can reflect the microscopic angle changes of the rotor with high fidelity.

[0069] Furthermore, when the impedance signal is synchronously or polled on multiple coil windings using a high-frequency measurement and decoupling module, it can be combined with... Figure 4The temporal relationship shown is used to construct a multi-channel angle fusion solution algorithm. For example, peak-valley counting, adjacent channel delay estimation, cross-correlation analysis, or phase-locked tracking technology can be used to jointly solve the multi-channel output, thereby achieving high resolution, strong noise resistance, and excellent dynamic response performance for corner detection in a miniaturized space.

[0070] Although illustrative specific embodiments of the present invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the present invention is not limited to the scope of the specific embodiments. Various modifications will be apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and established by the appended claims, and all inventions utilizing the inventive concept are protected.

Claims

1. A self-sensing system for the rotation angle of a winding-multiplexed motor based on the eddy current effect, characterized in that, include: The system comprises a brushless coreless motor rotor, a non-magnetic conductive strip disposed on the rotor surface, a multi-pole coil winding, and a motor drive module and a high-frequency measurement and decoupling module, both connected to the multi-pole coil winding. The high-frequency measurement and decoupling module injects a high-frequency excitation signal into the multi-pole coil winding and isolates the low-frequency drive signal output by the motor drive module. When the rotor rotates, eddy current coupling occurs between the non-magnetic conductive strip and the multi-pole coil winding, causing the equivalent impedance parameter of the multi-pole coil winding to change with the rotation angle. The high-frequency measurement and decoupling module extracts the change signal of the equivalent impedance parameter and calculates the rotor rotation angle information based on the signal timing relationship. The non-magnetic conductive strip is disposed on the outer circumferential surface of the permanent magnet rotor; The rotor is cylindrical in shape and is fixedly connected to the central shaft, rotating around the central shaft; The high-frequency measurement and decoupling module includes a high-frequency isolation circuit and a high-frequency impedance measurement circuit; the high-frequency isolation circuit is connected between the multipole coil winding and the high-frequency impedance measurement circuit to prevent the drive current from entering the high-frequency impedance measurement circuit, while allowing the transmission of the high-frequency excitation signal and the high-frequency carrier signal carrying impedance change information. The high-frequency impedance measurement circuit includes a high-frequency excitation generation unit, a signal conditioning unit, and a demodulation unit; the demodulation unit is used to extract the amplitude or phase change characteristics in the high-frequency carrier signal to obtain the equivalent impedance parameter. The rotor angle information calculation includes converting the multipole coil winding into multiple windings along the circumferential direction, sweeping the conductive strip across each winding in sequence to form a regular delay or phase difference, determining the interval between adjacent windings, and using the monotonic relationship of the differential signals between adjacent windings to obtain the subdivided angle within the interval and the current single-turn angle.

2. The self-sensing angle sensing system according to claim 1, characterized in that, The non-magnetic conductive strip is a strip structure formed of copper foil, copper plating, aluminum foil, aluminum plating, or a non-ferromagnetic highly conductive material.

3. The self-sensing angle system according to claim 1, characterized in that, The width of the non-magnetic conductive strip is less than or equal to the pole pitch of two adjacent multipole coil windings.

4. The self-sensing angle system according to claim 1, characterized in that, The multipole coil winding is equivalent to multiple windings along the circumferential direction.

5. A self-sensing method for the rotation angle of a winding-multiplexed motor based on the eddy current effect, characterized in that, The system, as described in any one of claims 1-4, comprises the following steps: S1, arranging a non-magnetic conductive strip on the outer circumferential surface of the motor rotor; S2, injecting a high-frequency excitation signal into the multi-pole coil winding of the motor stator through a high-frequency measurement and decoupling module, and isolating the low-frequency drive signal of the motor; S3, during motor rotation, extracting the equivalent impedance parameter change signal of the multi-pole coil winding caused by the eddy current coupling effect through the high-frequency measurement and decoupling module; S4, calculating the rotor angle information based on the characteristic parameters of the change signal and the signal timing relationship.

6. The method according to claim 5, characterized in that, In step S4, the characteristic parameters of the changing signal include one or more of amplitude, phase, peak and valley positions, zero crossing points, and waveform feature points; the calculation of the rotor angle information adopts at least one of peak and valley counting, table lookup fitting, feature point identification, or phase-locked tracking algorithm.

Images