A direct current permanent magnet motor speed control device

Abstract

This invention discloses a DC permanent magnet motor speed control device, comprising: a permanent magnet motor, a permanent magnet rotor, a segmented stator assembly, a flux valve assembly, a speed detection unit, and a controller; the segmented stator assembly is divided into several stator segments along the axial direction, each stator segment corresponding to the effective coupling area of ​​the permanent magnet rotor; the flux valve assembly is installed between the stator segments, and the flux valve assembly adjusts the through-gap flux between the stator segments; the controller collects the voltage and current of each flux valve coil to estimate the flux linkage change rate of each segment, constructs a boundary induced electromotive force imbalance index based on the difference in flux linkage change rate between adjacent stator segments, and generates control quantities for each segment based on the target speed and the boundary induced electromotive force imbalance index to suppress cross-segment eddy current loop drive and inter-segment magnetic circuit crosstalk; this invention avoids the amplified influence of frictional hysteresis, gap accumulation, and repetitive positioning error of the displacement mechanism on the air gap stability, directly making the torque output and speed regulation process smoother and the speed ripple lower.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and in particular to a speed control device for a DC permanent magnet motor. Background Technology

[0002] Permanent magnet motors are widely used in fans, pumps, conveying equipment, and various electromechanical actuators due to their simple structure, large starting torque, and convenient control. To meet the speed matching requirements under different operating conditions, existing systems typically use armature voltage regulation, PWM speed control, and other methods to control the speed of permanent magnet motors.

[0003] However, in scenarios with large load inertia, frequent impact conditions, or requiring a wide speed range and smooth output, relying solely on motor-based electronic speed control can easily lead to problems such as large armature current fluctuations, increased commutation sparking, poor low-speed stability, and increased electromagnetic noise and heat generation. To improve the speed range and operational stability, coupling speed controllers are often installed between the motor and the load in engineering practice. These controllers achieve torque transmission and speed regulation in a non-contact manner, thereby buffering impacts, isolating vibrations, and reducing maintenance.

[0004] For example, Chinese patent CN119253925B discloses a magnetic levitation permanent magnet speed regulator and its speed regulation method based on a magnetic levitation linear motor. This type of mechanism changes the contact area between the permanent magnet rotor and the stator through mechanical displacement. However, in long-term operation, it is prone to repeated positioning errors due to factors such as friction hysteresis, gap wear and assembly eccentricity, resulting in dead zones in the coupling adjustment and inducing speed ripple.

[0005] Therefore, it is necessary to design a DC permanent magnet motor speed control device to solve this type of problem. Summary of the Invention

[0006] This invention overcomes the shortcomings of the prior art and provides a DC permanent magnet motor speed control device.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a DC permanent magnet motor speed control device, comprising:

[0008] The permanent magnet rotor is fixedly connected to the output shaft of the permanent magnet motor and rotates with it;

[0009] The segmented stator assembly is fixedly connected inside the permanent magnet motor and sleeved on the outside of the permanent magnet rotor; wherein, the permanent magnet rotor and the segmented stator assembly are radially spaced to form a working air gap, and their axial relative positions remain unchanged during speed regulation; the segmented stator assembly is divided into several stator segments along the axial direction, and each stator segment corresponds to the effective coupling area of ​​the permanent magnet rotor in sequence.

[0010] A flux valve assembly is installed between several of the stator segments, and the flux valve assembly adjusts the through-gap magnetic flux between the stator segments;

[0011] The speed detection unit is used to obtain the actual speed of the rotor; and

[0012] The controller collects the voltage and current of each flux valve coil to estimate the flux change rate of each segment, constructs a boundary induced electromotive force imbalance index based on the difference in flux change rate between adjacent stator segments, and generates control quantities for each stator segment based on the target rotational speed and the boundary induced electromotive force imbalance index to drive the flux valve assembly of each stator segment.

[0013] In a preferred embodiment of the present invention, the flux valve assembly includes a bypass magnetic bridge and a control coil;

[0014] The bypass magnetic bridge is made of a saturable soft magnetic material;

[0015] The control coil is used to change the equivalent magnetic reluctance of the bypass magnetic bridge to switch or continuously adjust between opening the bypass magnetic flux channel and restricting the bypass magnetic flux channel, thereby changing the through-gap magnetic flux of the stator segment.

[0016] In a preferred embodiment of the present invention, each of the stator segments has a corresponding segment magnetic yoke structure.

[0017] In a preferred embodiment of the present invention, the effective coupling area is determined by the effective coupling length of each stator segment and the corresponding circumferential action area.

[0018] When the controller determines that a stator segment participates in electromagnetic coupling, the through-gap magnetic flux of a certain stator segment reaches a preset threshold or its magnetic flux valve component control enters a preset working range. When the through-gap magnetic flux is lower than the preset threshold or its magnetic flux valve component control enters a preset non-working range, the controller determines that the stator segment does not participate in electromagnetic coupling.

[0019] The controller selects several stator segments to participate in electromagnetic coupling by increasing or decreasing the control amount of the flux valve assembly of different stator segments, thereby changing the total effective coupling area.

[0020] In a preferred embodiment of the present invention, estimating the flux linkage change rate of each segment includes:

[0021] The coil voltage and coil current of the flux valve assembly for each stator segment are collected, and the results are based on the coil voltage, coil current, and the corresponding coil resistance and number of coil turns.

[0022] The coil voltage at different times is recorded to form a pair of adjacent time point data for numerical calculation.

[0023] Based on the number of coil turns and the time period, the coil voltage component is mapped to an estimated value of the change in flux linkage within the sampling time interval, thus obtaining the flux linkage increment within that interval. This increment is then divided by the sampling period length to obtain the rate of change of flux linkage within that period.

[0024] In a preferred embodiment of the present invention, the step of constructing the boundary induced potential imbalance index based on the difference in flux linkage change rate between adjacent stator segments includes:

[0025] According to the circumferential order of the stator segments, adjacent stator segments are grouped into a boundary pair;

[0026] The flux linkage change rates of the two stator segments within each boundary pair are compared to obtain the flux linkage change rate difference at the boundary position. The flux linkage change rate difference is used to represent the difference in the dynamic behavior of the flux linkage of the two segments at the boundary under a time-varying magnetic field.

[0027] By aggregating the differences in flux change rates at each boundary location, and by performing absolute value processing, amplitude amplification processing, and normalization processing on the differences, all boundary differences can be transformed into a single comprehensive quantitative parameter; and by summing and squaring, the boundary induced potential imbalance index can be obtained.

[0028] In a preferred embodiment of the present invention, the controller is configured to generate a target coupling capability based on the deviation between the target rotational speed and the actual rotational speed, and to minimize the boundary induced electromotive force imbalance index when generating control quantities for each stator segment flux valve assembly. One of the constraints or optimization objectives.

[0029] The controller is configured to acquire the target speed n and the actual speed n1, calculate the speed deviation e, and generate a target coupling capability τ based on the speed deviation e, wherein the target coupling capability τ is used to characterize the target torque transmission level or target coupling strength level that the effective coupling area should achieve.

[0030] In a preferred embodiment of the present invention, the controller is configured to generate control quantities vk for each stator segment flux valve assembly, such that the actual coupling capability τ1 formed by the control quantities vk tracks the target coupling capability τ, and to include the boundary induced potential imbalance index when generating the control quantities vk. As one of the constraints or optimization objectives, reducing the difference in flux linkage rate between adjacent stator segments is a key objective.

[0031] Among them, the This is an index constructed based on the difference in flux linkage change rate between adjacent stator segments.

[0032] In a preferred embodiment of the present invention, the controller is configured to set amplitude constraints and rate of change constraints for the control quantity vk of each stator segment, wherein the amplitude constraint limits vk to be within a preset allowable range, and the rate of change constraint limits the change of vk within the control period Δt to not exceed a preset threshold Δumax, so as to limit the sudden change of flux linkage rate and reduce the induced potential difference at the boundary of adjacent stator segments.

[0033] In a preferred embodiment of the present invention, the controller is implemented using a microcontroller, DSP or FPGA with analog-to-digital converter, timer, PWM output and digital signal processing capabilities, and includes at least a sampling module, an estimation module, an index construction module, a target generation module, a control quantity solving module and a drive output module.

[0034] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0035] (1) The present invention provides a DC permanent magnet motor speed control device. By dividing the segmented stator assembly into several stator segments along the axial direction and making each stator segment correspond to the effective coupling area of ​​the permanent magnet rotor in sequence, the effective coupling area can be graded or continuously adjusted by selecting several stator segments to participate in the coupling. This transforms the adjustment of coupling capability from single-channel amplitude adjustment to controllable spatial area allocation, thereby expanding the speed range and improving the speed resolution without changing the axial position. Furthermore, when the load changes abruptly, faster torque redistribution and smaller speed fluctuations can be achieved by rapidly changing the number of stator segments participating in the coupling or the coupling strength.

[0036] (2) The present invention provides a DC permanent magnet motor speed control device. The controller collects the voltage and current of each flux valve coil and estimates the flux change rate of each segment. It constructs a boundary induced electromotive force imbalance index based on the difference in flux change rate of adjacent stator segments, actively controls the induced electromotive force difference at the boundary of adjacent segments, thereby suppressing the excitation of cross-segment circulating current from the source under continuous conditions, reducing the additional losses and local temperature rise uncertainty caused by cross-segment eddy current, and reducing the torque ripple caused by the potential difference at the boundary.

[0037] (3) The present invention provides a DC permanent magnet motor speed control device. By minimizing the boundary induced electromotive force imbalance index when generating the control quantity of each stator segment flux valve component, and by limiting the amplitude and rate of change of the control quantity, the difference in flux change rate between adjacent stator segments is kept under control under the premise of meeting the target speed. This avoids the boundary electromotive force peak caused by flux change caused by segment switching or rapid modulation, directly reduces transient cross-segment eddy current and torque impact and improves the smoothness of dynamic response, further reduces the risk of noise vibration and mechanical fatigue and improves the stable operation capability under rapid acceleration and deceleration and load impact scenarios.

[0038] (4) The present invention uses a permanent magnet rotor that is fixedly connected to the output shaft of a permanent magnet motor and rotates with it, and a segmented stator assembly that is fixedly installed and sleeved on the outside of the permanent magnet rotor. At the same time, the axial relative position of the permanent magnet rotor and the segmented stator assembly remains unchanged during the speed regulation process, so that the speed regulation no longer depends on axial displacement or mechanical slippage to change the coupling relationship. This avoids the amplified effect of frictional hysteresis, gap accumulation and repeated positioning error of the displacement mechanism on the air gap stability, directly making the torque output and speed regulation process smoother and the speed ripple lower, further improving the control consistency and device reliability under long-term operation and reducing the maintenance frequency. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a three-dimensional structural diagram of a DC permanent magnet motor according to a preferred embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the internal structure of a DC permanent magnet motor according to a preferred embodiment of the present invention;

[0042] Figure 3 This is a timing diagram of the DC permanent magnet motor speed control process according to a preferred embodiment of the present invention;

[0043] Figure 4 This is a partial cross-sectional view of the flux valve assembly according to a preferred embodiment of the present invention;

[0044] In the diagram: 1. Permanent magnet motor; 2. Permanent magnet rotor; 3. Flux valve assembly; 4. Stator section; 5. Bypass magnetic bridge; 6. Control coil. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0047] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0048] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0049] like Figure 1 and Figure 2 As shown, a DC permanent magnet motor speed control device includes:

[0050] 1. Permanent magnet motor; 2. Permanent magnet rotor; 3. Segmented stator assembly; 4. Flux valve assembly; 5. Speed ​​detection unit and controller;

[0051] The permanent magnet rotor 2 is fixedly connected to the output shaft of the permanent magnet motor 1 and rotates with it;

[0052] The segmented stator assembly is fixedly connected inside the permanent magnet motor 1 and sleeved on the outside of the permanent magnet rotor 2;

[0053] The permanent magnet rotor 2 and the segmented stator assembly form a working air gap with radial spacing, and their axial relative positions remain unchanged during speed regulation.

[0054] The segmented stator assembly is divided into several stator segments 4 along the axial direction, and each stator segment 4 corresponds to the effective coupling area of ​​the permanent magnet rotor 2.

[0055] The flux valve assembly 3 is installed between several stator sections 4, and the flux valve assembly 3 adjusts the through-gap magnetic flux between the stator sections 4.

[0056] The speed detection unit is used to obtain the actual speed of the load shaft;

[0057] The controller collects the voltage and current of each flux valve coil to estimate the flux change rate of each segment, constructs a boundary induced electromotive force imbalance index based on the difference in flux change rate of adjacent stator segments, and generates control quantities for each segment based on the target speed and the boundary induced electromotive force imbalance index to suppress cross-segment eddy current loop drive and inter-segment magnetic circuit crosstalk.

[0058] The present invention employs a surface-mount permanent magnet motor 1, wherein the permanent magnet is attached to the surface of the permanent magnet rotor 2. The stator is divided into several stator segments 4 along the axial direction, and each stator segment 4 corresponds to the effective coupling area of ​​the permanent magnet rotor 2. Thus, the stator segment 4 corresponds to the permanent magnet on the surface of the permanent magnet rotor 2, which is the effective coupling area.

[0059] When the through-gap magnetic flux of a certain stator segment 4 enters the region where it can effectively participate in electromagnetic energy conversion, that segment participates in doing work in space, thereby effectively expanding the coupling area of ​​the motor.

[0060] In the existing technology, the stator is driven to move by mechanical movement, and the change of the effective coupling area between the stator and the permanent magnet rotor 2 is controlled. The existing technology uses splines and rolling bearings to achieve axial mobility and radial constraint, but it has frictional hysteresis, clearance wear and eccentric runout, which will cause dead zone and repeated positioning error in the coupling area adjustment, affecting the smoothness and accuracy of speed control.

[0061] Therefore, dividing the stator into several stator segments 4 along the axial direction allows the permanent magnet motor 1 to be speed-controlled by controlling the effective coupling area. During speed regulation, the axial relative position of the permanent magnet rotor 2 and the segmented stator assembly remains unchanged, so that speed regulation no longer depends on axial displacement or mechanical slippage to change the coupling relationship. This avoids the amplified impact of frictional hysteresis, gap accumulation, and repetitive positioning errors of the displacement mechanism on the air gap stability, directly making the torque output and speed regulation process smoother and the speed ripple lower. This further improves the control consistency and device reliability under long-term operation and reduces the maintenance frequency.

[0062] When the stator is used to select several segments to participate in coupling to achieve equivalent coupling area adjustment, the segments are not naturally independent electromagnetically. Especially in scenarios where the conductor is continuous, the magnetic circuit is continuous, or the bypass magnetic bridge 5 enters a nonlinear saturation bypass state, the asynchronous change rate of magnetic flux of any adjacent stator segment 4 will form an induced potential difference at the segment boundary, thereby driving cross-segment circulating current or boundary eddy current loop. The magnitude of this type of circulating current is affected by material resistivity, temperature, assembly tolerance and magnetic saturation state, and exhibits unpredictable characteristics. Therefore, it is difficult to simultaneously meet the requirements of rapid speed regulation and low ripple stability by relying solely on traditional speed closed-loop, such as adjusting a certain current amplitude or a certain duty cycle based solely on speed error.

[0063] In other words, the segmented structure brings spatial freedom, but also boundary uncertainty. If the induced potential difference at the boundary is not explicitly constrained, the faster the segmented speed regulation, the easier it is to trigger a sudden change in magnetic flux, which in turn leads to cross-segment eddy currents and torque impacts, manifested as increased speed ripple or even oscillation.

[0064] That is, when there is a continuous conduction path between adjacent stator segments 4, the time-varying magnetic flux will induce circulating currents and eddy currents in the closed loop across segments; at the same time, when some segments enter the bypass or local saturation state, the magnetic circuits of adjacent segments will be borrowed or squeezed, which will cause the magnetic flux changes of adjacent segments to restrain each other, resulting in segment control not being independent and unpredictable nonlinearity and crosstalk in torque response.

[0065] The controller collects the voltage and current of each flux valve coil to estimate the flux change rate of each segment, constructs a boundary induced electromotive force imbalance index based on the difference in flux change rate of adjacent stator segments, and generates control quantities for each segment based on the target speed and the boundary induced electromotive force imbalance index to suppress cross-segment eddy current loop drive and inter-segment magnetic circuit crosstalk.

[0066] like Figure 3 and Figure 4 As shown, in this embodiment, a flux valve assembly 3 is provided between adjacent stator segments 4. The purpose of the flux valve assembly 3 is to adjust the through-gap magnetic flux between stator segments 4, thereby changing the magnetic flux distribution of each segment entering the magnetic field interaction region of the permanent magnet rotor 2 through the working air gap. Its position is at the boundary of adjacent stator segments 4 or at the setting point that crosses the boundary. Its constraint condition is that it does not contact the rotating parts under all working conditions, and its electromagnetic action does not introduce mechanical displacement that would damage the stability of the main air gap.

[0067] As a preferred structure, the flux valve assembly 3 includes a bypass magnetic bridge 5 and a control coil 6. The bypass magnetic bridge 5 is made of a saturable soft magnetic material, and the control coil 6 is used to change the equivalent magnetic reluctance of the bypass magnetic bridge 5 to switch or continuously adjust between opening the bypass magnetic flux channel and restricting the bypass magnetic flux channel, thereby changing the through-gap magnetic flux of the stator section 4.

[0068] The bypass magnetic bridge 5 refers to providing a bypass magnetic flux channel with controllable magnetic resistance between adjacent segments. Its equivalent magnetic resistance is low in the unsaturated state, and the magnetic flux tends to close within the bypass, thereby reducing the magnetic flux that crosses the working air gap and enters a certain effective coupling region.

[0069] Under saturated or controlled reluctance conditions, the bypass equivalent reluctance increases, and the magnetic flux tends to enter the main coupling magnetic flux channel of this section through the working air gap, thereby enabling this section to participate in coupling.

[0070] The control coil 6 refers to the excitation coil wound around the bypass magnetic bridge 5 or its magnetic core, which changes the magnetization state of the magnetic bridge by applying coil voltage or coil current.

[0071] In this embodiment, the through-gap magnetic flux refers to the bypass magnetic flux component that passes through the structural gap between segments. This magnetic flux component can come from the leakage magnetic flux of the permanent magnet rotor 2 in space, or from the overflow magnetic flux of a certain stator magnetic circuit under a high magnetopotential difference.

[0072] If left uncontrolled, the through-gap magnetic flux will become the main carrier of crosstalk between magnetic circuits and will form a driving potential difference for cross-segment circulating currents when the flux change rates of adjacent segments are not synchronized.

[0073] Therefore, the flux valve assembly 3 is not only used to change the coupling strength of a certain segment, but also to manage the energy exchange at the boundary between segments. The key technical problem it solves is that after the segmented structure is introduced, new electromagnetic side effects will appear at the boundary between segments, including eddy current additional losses caused by the imbalance of induced electromotive force at the boundary, local temperature rise uncertainty and torque ripple. If these side effects are not constrained, they will offset the advantages brought by segmented speed regulation.

[0074] By setting a controllable flux valve assembly 3 between segments, the through-gap flux is incorporated into a controllable variable. This allows the difference in flux change rate at the segment boundary to be buffered and modulated by the controllable magnetic resistance, thereby providing a physical actuator for the subsequent controller to introduce boundary imbalance indicators.

[0075] In this embodiment, the flux valve assembly 3 preferably includes a bypass magnetic bridge 5 and a control coil 6. The bypass magnetic bridge 5 is made of a saturable soft magnetic material, and the control coil 6 is used to change the equivalent magnetic reluctance of the bypass magnetic bridge 5 to switch or continuously adjust between opening the bypass magnetic flux channel and restricting the bypass magnetic flux channel, thereby changing the through-gap magnetic flux of the stator section 4.

[0076] In this embodiment, the saturable soft magnetic material of the bypass magnetic bridge 5 can be one or a combination of silicon steel, permalloy, amorphous soft magnetic material, nanocrystalline soft magnetic material or ferrite. When the control coil 6 applies a magnetizing current, the bypass magnetic bridge 5 gradually tends to saturate in the magnetization direction, the equivalent permeability of the material decreases, and thus the equivalent magnetic reluctance of the bypass magnetic bridge 5 increases.

[0077] When the current in the control coil 6 is reduced or removed, the material is in a state of high permeability, the equivalent magnetic reluctance of the bypass magnetic bridge 5 decreases, and the bypass magnetic flux channel tends to be open.

[0078] In this way, controlling the current of coil 6 provides a continuously adjustable capability for the bypass flux path from low to high magnetic reluctance.

[0079] Furthermore, the inter-segment gap magnetic flux is not solely determined by the geometric gap, and it dynamically changes with speed, load, armature reaction, and magnetic saturation state during motor operation. Relying solely on fixed structural isolation cannot simultaneously achieve low crosstalk and controllable coupling under a wide range of operating conditions.

[0080] By using a saturable magnetic bridge to form a flux valve, the magnetic resistance can be reduced at low speeds and high torque or when rapid torque increase is required to allow a certain bypass flux for a smooth transition. At high speeds or when it is necessary to suppress eddy currents and ripples, the magnetic resistance can be increased to suppress the through-gap flux, thereby achieving adaptive management of energy exchange at the segment boundary and improving the efficiency and stability of the whole machine over a wide speed range.

[0081] This invention defines the effective coupling area as being jointly determined by the effective coupling length of each stator segment 4 and the corresponding circumferential area. Specifically, let D be the effective diameter of the outer circle of the permanent magnet rotor 2, then the equivalent coupling area of ​​the k-th segment can be expressed as... ,in Let [0, 1] be the participation coefficient of segment k, used to characterize the proportion of the through-gap magnetic flux of this segment relative to the fully participated state. When the through-gap magnetic flux of the kth stator segment 4 reaches a preset threshold or its magnetic flux valve assembly 3 control quantity reaches a preset range, the stator segment 4 is considered to participate in coupling. When the through-gap magnetic flux is below a preset threshold or the control quantity enters or exits the preset range, the stator segment 4 is considered to have disengaged, and the setting is 1. It is 0.

[0082] The preset threshold and preset range are determined as follows: During the factory calibration stage, the motor is run unloaded at a safe speed. The voltage or current of the control coil 6 is scanned segment by segment, and the estimated value of the through-gap magnetic flux and the torque response in the corresponding segment are recorded. The magnetic flux value corresponding to the inflection point that makes the torque response start to change significantly is selected as the preset threshold.

[0083] A range of engineering margins is established above and below this inflection point to determine noise and drift resistance. The controller selects several stator segments 4 to participate in coupling by increasing or decreasing the control quantity of the flux valve assembly 3 of different stator segments 4, thereby changing the total equivalent coupling area. .

[0084] In this embodiment, the speed detection unit is used to obtain the actual speed of the load shaft. This unit can be a Hall encoder, a magnetoelectric speed sensor, a photoelectric encoder, or a positionless estimation unit based on back EMF.

[0085] The speed regulation degree of freedom of the present invention comes from the distribution of the coupling area and coupling strength of the stator segment 4. Its control object is not a single voltage or a single current. Therefore, the equivalent gain varies with the number of segments involved, the state of the flux valve and the load state.

[0086] Without actual speed feedback, the controller can only adopt an open-loop or semi-open-loop strategy. In this case, any load disturbance, resistance change caused by temperature rise, permanent magnet demagnetization, or magnetic bridge saturation drift will cause the deviation between the target coupling capability and the actual coupling capability to be unable to be corrected in time, which will eventually manifest as steady-state speed error, dynamic response hysteresis, or even instability.

[0087] By forming a closed loop through speed detection, the controller can convert the target speed into the target coupling capability, and then further generate control quantities for each segment through optimized allocation, so that the speed regulation process is robust to load disturbances and the speed ripple remains controllable during segment switching.

[0088] In this embodiment, the controller can be implemented using a microcontroller, DSP, or FPGA with analog-to-digital converter, timer, PWM output, and digital signal processing capabilities. It includes at least a sampling module, an estimation module, an index construction module, a target generation module, a control quantity solving module, and a drive output module.

[0089] The sampling module is used to synchronously acquire the coil voltage and coil current of the flux valve control coil 6 within the discrete control cycle, and to acquire the actual rotational speed output by the rotational speed detection unit;

[0090] The estimation module is used to estimate the rate of change of flux linkage in each segment based on the sampled values;

[0091] The index construction module is used to calculate the boundary induced potential imbalance index;

[0092] The target generation module is used to generate target coupling capability based on the deviation between the target rotational speed and the actual rotational speed;

[0093] The control quantity solving module is used to solve the control quantities of the four flux valves in each stator section under constraints.

[0094] The drive output module is used to convert the control quantity into a drive voltage or drive current command for the control coil 6 and output it to the power drive circuit.

[0095] In terms of flux linkage rate estimation, this embodiment uses sampling of the coil voltage and coil current of the flux valve assembly 3 of the kth stator segment 4 to calculate the flux linkage rate.

[0096] The root cause of the difference in induced electromotive force at the boundary between segments is that the flux change rate of adjacent segments is not synchronized. The flux change rate is usually difficult to reliably measure in the small space inside the motor using a direct flux sensor. Furthermore, direct flux measurement introduces additional sensor costs, is sensitive to installation location, and is difficult to resist interference.

[0097] In contrast, the flux valve control coil 6, as an existing actuator, can have its terminal voltage and current obtained through conventional current sampling resistors and isolated sampling circuits. The flux linkage change rate can be estimated without additional flux sensors using the basic electromagnetic equations, thus achieving observable boundary imbalances at low cost.

[0098] This solves the problem that in segmented speed regulation structures, it is necessary to obtain observable measurements of the electromagnetic state at the segment boundaries, otherwise it is impossible to suppress the cross-segment circulating current drive at the control level. Therefore, without significantly increasing hardware complexity, online estimation of the induced potential difference at the segment boundaries is achieved, providing real-time data for subsequent constraint optimization.

[0099] Specifically, in order to obtain the boundary induced potential imbalance index, this embodiment establishes an online calculation method for estimating the flux change rate for each segment of the flux valve control coil 6.

[0100] Specifically, the driving source of the cross-segment eddy current loop is not the segment itself, but the induced potential difference at the segment boundary, and the induced potential is directly related to the rate of change of magnetic flux in an electromagnetic sense.

[0101] Therefore, by reducing the equivalent induced potential difference at the boundary of adjacent segments to a sufficiently low level, even if there is continuity in the conductor shape, the driving force of the cross-segment circulation can be weakened from the source, causing the cross-segment eddy current to degenerate from a deterministic circulation that is forced to be excited into a weakly excited random loss term. This transforms the problem that is most difficult to solve by the structure in one go into an index control problem that can be continuously suppressed in the closed loop.

[0102] Specifically, the controller is configured to control the coil voltage of the flux valve assembly 3 in the kth stator segment 4. With coil current Sampling is performed, and the flux linkage rate of the kth stator segment 4 is estimated based on the coil voltage, coil current, equivalent resistance, and number of turns: Where k is the sequence number of stator segment 4, The coil voltage of the control coil 6 of the flux valve assembly 3 in the kth stator segment 4 is... The coil current of the control coil 6 for the flux valve assembly 3 of the kth stator segment 4 is... Let be the equivalent resistance of the control coil 6 of the kth stator segment 4. The number of turns of the control coil 6 in the kth stator segment 4. Let t be the flux linkage corresponding to the kth stator segment 4, and t be time.

[0103] The controller can identify in real time whether the flux linkage changes too fast or too slow in a certain segment, as well as the inconsistent changes in flux linkage of adjacent segments, thereby quantifying the risks of crosstalk and cross-segment circulating current in advance and incorporating them into the control law.

[0104] Regarding the construction of the boundary induced potential imbalance index, this embodiment constructs an index based on the difference in flux change rate between adjacent stator segments 4, which is used to characterize the strength of the induced potential difference at the boundary of adjacent stator segments 4.

[0105] Because when the flux change rates of adjacent segments are not synchronized, the conductive structures near the segment boundaries will be excited by different induced electromotive forces, which may lead to the formation of cross-segment eddy current loops.

[0106] The presence of cross-segment eddy current loops generates additional copper or iron losses and causes localized temperature rise. This temperature rise further alters parameters such as equivalent resistance, forming an error closed loop. Furthermore, the eddy current magnetic field reacts to the main magnetic flux, leading to torque ripple and noise vibration. Simultaneously, during segment switching or rapid modulation, the eddy current peak value amplifies transient electromagnetic shocks, thereby reducing reliability. Therefore, simply allowing the actual rotational speed to track the target rotational speed is insufficient to guarantee efficient and smooth system operation. It is essential to explicitly consider the strength of potential differences at the boundary when generating control inputs and suppress them within acceptable limits.

[0107] Therefore, it is necessary to construct an index for the imbalance of boundary induced potential, for example, by constructing an index based on the difference in flux change rate between adjacent segments k and (k+1) of the kth segment: ,in and , respectively, are the flux linkage change rates of the adjacent k-th segment and the (k+1)-th segment, and m is the number of stator segments 4; Used to characterize the strength of the difference in induced potential at the boundary of adjacent stator segments 4.

[0108] Inter-segment crosstalk and cross-segment circulating current are scalars: the larger the index, the stronger the induced potential difference at the boundary, the easier it is for the cross-segment loop to be driven, and the higher the risk of additional losses and torque ripple; the smaller the index, the more the potential is balanced at the boundary of adjacent segments, the cross-segment circulating current driving force is suppressed, and the segment control independence is closer to the ideal state.

[0109] Upon obtaining the boundary induced electromotive force imbalance index, the controller is configured to generate a target coupling capability based on the deviation between the target speed and the actual speed, and to minimize the boundary induced electromotive force imbalance index when generating the control quantities for each stator segment 4 flux valve assembly 3. One of the constraints or optimization objectives.

[0110] It should be noted that the coil voltage is used as a means to suppress cross-segment eddy currents mainly because, by adjusting the driving voltage of coil 6 controlled by the flux valve, the trend of the magnetomotive force of the stator segment changing with time can be directly changed, thereby changing the rate of change of the flux linkage.

[0111] Since the generation of cross-segment eddy currents depends on the inconsistency of the flux change rate of adjacent stator segments, a transient induced potential difference that can drive eddy currents will only be formed at the core boundary between segments when the flux change rate of a certain segment is significantly higher or lower than that of its neighboring segment.

[0112] Therefore, by coordinating and adjusting the coil voltage, the flux change rate of each segment can be kept synchronous or nearly synchronous in time evolution, which can significantly reduce or even eliminate the induced potential difference between segments. This results in insufficient driving potential inside the iron core to maintain the eddy current loop, and the eddy current naturally decays and is suppressed.

[0113] In a preferred embodiment of the present invention, the flux valve assembly is disposed between any adjacent k-th stator segment and k+1 stator segment, and the magnetic permeability is controlled by the excitation coil in the assembly, so that the change law of magnetic flux of each stator segment over time can be uniformly coordinated by the controller.

[0114] The controller drives the flux valve coil in the form of voltage. By adjusting the instantaneous voltage across the coil, the magnetic state of the flux valve core is dynamically changed, so that the section exhibits different equivalent magnetic reluctance.

[0115] Since the coil voltage is a direct variable that determines the rate of change of magnetic flux, the controller can precisely adjust the growth or decay of magnetic flux in this segment per unit time, so that it is consistent with the trend of magnetic flux change in adjacent segments, thereby suppressing cross-segment eddy current loops caused by magnetic flux differences.

[0116] For any k-th stator segment, this invention expresses the relationship between the controlled voltage of the excitation coil and the change in the core flux linkage as follows: .

[0117] The flux linkage change rate reflects the dynamic response of the instantaneous magnetomotive force of that segment and is a key physical quantity that determines the magnitude of the boundary induced electromotive force between adjacent stator segments.

[0118] When the rates of change of flux linkages of two adjacent segments are inconsistent, an inter-segment induced potential difference will be formed within the continuous path of the iron core they connect, thereby driving cross-segment eddy currents. The induced potential difference between adjacent segments k and k+1 is defined as... .

[0119] It can be seen that as long as the flux linkage change rates of the two stator segments are not consistent, a non-zero potential difference will appear between the segments. Once this potential difference has a closed conductive path in a certain region, a cross-segment eddy current loop can be formed, and the instantaneous magnitude of the eddy current is proportional to the potential difference.

[0120] To suppress eddy current loops, this embodiment uses the potential difference between all adjacent segments as an imbalance index, namely the boundary induced potential imbalance index. The controller always limits this index below a preset threshold throughout the speed regulation process, so that the cross-segment eddy currents lack driving force.

[0121] The potential difference is suppressed by actively adjusting the voltage of each section of the coil. Since the rate of change of magnetic flux varies with the coil voltage, and the governing equation can be expressed as follows: Where f is the function mapping of the change in magnetic permeability of each flux valve assembly to the rate of flux linkage change, which can be obtained through parameter identification. Since the coil current is determined by the changes in the magnetic reluctance of the flux valve and the stator core, as well as the working air gap, the controller can adjust the voltage to make the rate of flux linkage change rise or fall at the required speed while maintaining the coil current within a controllable range. Therefore, by adjusting the coil voltage, the rates of flux linkage change of segments k and k+1 can satisfy... This causes the potential difference between segments to approach zero.

[0122] In each control cycle, the controller determines the set of stator segments that need to participate in magnetic coupling based on the target coupling area, target torque, and the current rotor position, and determines the desired total flux linkage. Calculate the flux contribution that each segment should provide.

[0123] Let the target of the k-th magnetic flux linkage be Ψk, then it satisfies ,in The weight of each segment's contribution to the overall coupling is 0-1, defined by the staff.

[0124] To avoid magnetic circuit crosstalk caused by excessive inter-segment boundary potential differences, the controller introduces constraint terms when solving for coil voltages. This ensures that while meeting the total flux linkage requirement, the flux linkage change rate between all segments remains as consistent as possible. In actual calculations, the controller will vector the coil voltage... .

[0125] To avoid instantaneous peak values ​​in the flux linkage rate caused by voltage steps, this invention imposes a restriction on the slope of the coil voltage change, ensuring that the voltage change between any two control cycles satisfies... .

[0126] in, This represents the terminal voltage applied to the excitation coil of the k-th segment flux valve at time t in the current control cycle, preferably the instantaneous control voltage across the coil. It represents the terminal voltage applied to the same coil at time t+Δt in the next control cycle; Δt represents the time interval between two adjacent control cycles, that is, the control cycle of the motor speed controller, the value of which is determined by the sampling and calculation frequency of the controller. A preset voltage variation limit is used to limit the maximum allowable variation of the coil voltage within a control cycle.

[0127] The above constraints limit the slope of the coil voltage change over time. Even when the stator segment participates in state switching or the target flux linkage changes abruptly, the coil voltage of each segment will not experience a sudden step change. This avoids the instantaneous peak value of the flux linkage change rate caused by voltage step change, and further prevents the inter-segment induced potential from increasing suddenly and exciting the strong cross-segment eddy current loop.

[0128] In embodiments of the present invention, the desired total flux linkage is a reference flux linkage determined by the controller based on the target output torque, target speed, and current rotor position. This reference flux linkage is used to constrain the overall magnetic coupling capability required by all participating stator segments within the control cycle. Since the magnetic field strength formed by the permanent magnet rotor in the air gap is essentially fixed, in a segmented stator structure, only the equivalent magnetic reluctance formed by the effective coupling area of ​​the rotor and the opening degree of the flux valves in each segment is actually adjustable.

[0129] Therefore, by adjusting the voltage of each section of the flux valve coil, the whole machine can have a total flux linkage level that is consistent with the target torque and speed at that moment, which is the essential source of the desired total flux linkage in this invention.

[0130] When using this invention, the permanent magnet motor 1 and the load shaft are first assembled and positioned, so that the permanent magnet rotor 2 is fixedly connected to the motor output shaft and rotates with it. At the same time, the segmented stator assembly is fixedly installed inside the motor and sleeved on the outside of the permanent magnet rotor 2, with the two radially spaced to form a working air gap. During the entire speed regulation operation, the axial relative position of the permanent magnet rotor 2 and the segmented stator assembly remains unchanged, and each stator segment 4 is equipped with a segmented magnetic yoke structure, so that the main coupling magnetic flux channel is mainly closed within the range of each stator segment 4. From the structural level, the frictional hysteresis, gap accumulation and repeated positioning error caused by relying on axial displacement or mechanical slippage to change the coupling relationship are avoided from amplifying the impact on the air gap stability. This provides a stable magnetic circuit boundary and a lower inter-segment crosstalk basis for the subsequent allocation of coupling capability according to the stator segment 4.

[0131] Subsequently, flux valve assemblies 3 are installed sequentially between adjacent stator segments 4 and electrically connected. The flux valve assembly 3 includes a bypass magnetic bridge 5 and a control coil 6. The bypass magnetic bridge 5 is made of saturable soft magnetic material, and the control coil 6 is used to change the equivalent magnetic reluctance of the bypass magnetic bridge 5 to switch or continuously adjust between conducting and limiting the bypass magnetic flux channel, thereby controllably modulating the through-gap magnetic flux between stator segments 4. This allows for the regulation of the bypass magnetic flux at the segment boundary, suppressing cross-segment eddy current loop drive caused by asynchronous inter-segment magnetic linkages and reducing inter-segment magnetic circuit crosstalk. Simultaneously, the effective coupling area is determined based on the effective coupling length and corresponding circumferential action area of ​​each stator segment 4. The corresponding stator segment 4 is judged to participate in coupling based on the through-gap magnetic flux threshold or the preset range of the flux valve control quantity. Thus, the effective coupling area can be controllably changed by selecting several stator segments 4 to participate in coupling. Then, a speed detection unit is installed on the load shaft and connected to the controller to obtain the actual speed and form the feedback quantity necessary for closed-loop speed regulation.

[0132] Upon entering operation control, the controller acquires the target speed and the actual speed, calculates the speed deviation, and generates the target coupling capability from the speed deviation. The target coupling capability characterizes the target torque transmission level or target coupling strength level that the effective coupling area should achieve. Based on this, the controller synchronously collects the voltage and current of each flux valve control coil 6 to estimate the flux linkage change rate of each segment. It also constructs a boundary induced electromotive force imbalance index based on the difference in flux linkage change rates between adjacent stator segments 4, characterizing the strength of the induced electromotive force difference at the boundary of adjacent stator segments 4. Finally, when generating the control quantities for each stator segment 4 flux valve assembly 3, the actual coupling capability tracks the target coupling capability, minimizing the boundary induced electromotive force imbalance. The potential imbalance index is used as one of the constraints or optimization objectives to reduce the difference in flux change rate between adjacent stator segments 4, so as to suppress the driving potential difference of cross-segment eddy current loops from the source and reduce the impact of crosstalk between segments on coupling strength distribution. At the same time, amplitude and rate of change constraints are applied to the control quantity, limiting the control quantity to be within the allowable range and the change in quantity within the control cycle not to exceed the preset threshold. When the segment participates in the state switching, a gradual handover method is adopted to gradually increase the control quantity of the newly added segment and gradually decrease the control quantity of the exiting segment, thereby limiting the sudden change in flux change rate and reducing the peak value of the boundary potential. Ultimately, the target speed tracking is achieved while smooth speed regulation with low loss, low ripple, and low impact is achieved.

[0133] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A speed control device for a DC permanent magnet motor, characterized in that, include: The permanent magnet rotor is fixedly connected to the output shaft of the permanent magnet motor and rotates with it; The segmented stator assembly is fixedly connected inside the permanent magnet motor and sleeved on the outside of the permanent magnet rotor; wherein, the permanent magnet rotor and the segmented stator assembly are radially spaced to form a working air gap, and their axial relative positions remain unchanged during speed regulation; the segmented stator assembly is divided into several stator segments along the axial direction, and each stator segment corresponds to the effective coupling area of ​​the permanent magnet rotor in sequence. A flux valve assembly is installed between several of the stator segments, and the flux valve assembly adjusts the through-gap magnetic flux between the stator segments; The speed detection unit is used to obtain the actual speed of the rotor; and The controller collects the voltage and current of each flux valve coil to estimate the flux change rate of each segment, constructs a boundary induced electromotive force imbalance index based on the difference in flux change rate between adjacent stator segments, and generates control quantities for each stator segment based on the target rotational speed and the boundary induced electromotive force imbalance index to drive the flux valve assembly of each stator segment.

2. The DC permanent magnet motor speed control device according to claim 1, characterized in that: The flux valve assembly includes a bypass magnetic bridge and a control coil; The bypass magnetic bridge is made of a saturable soft magnetic material; The control coil is used to change the equivalent magnetic reluctance of the bypass magnetic bridge to switch or continuously adjust between opening the bypass magnetic flux channel and restricting the bypass magnetic flux channel, thereby changing the through-gap magnetic flux of the stator segment.

3. The DC permanent magnet motor speed control device according to claim 1, characterized in that: Each of the stator segments has a corresponding segment magnetic yoke structure.

4. The DC permanent magnet motor speed control device of claim 1, wherein: The effective coupling area is determined by the effective coupling length of each stator segment and the corresponding circumferential action area. When the controller determines that a stator segment participates in electromagnetic coupling, the through-gap magnetic flux of a certain stator segment reaches a preset threshold or its magnetic flux valve component control enters a preset working range. When the through-gap magnetic flux is lower than the preset threshold or its magnetic flux valve component control enters a preset non-working range, the controller determines that the stator segment does not participate in electromagnetic coupling. The controller selects several stator segments to participate in electromagnetic coupling by increasing or decreasing the control amount of the flux valve assembly of different stator segments, thereby changing the total effective coupling area.

5. The DC permanent magnet motor speed control device of claim 1, wherein: The estimated rate of change of flux linkage in each segment includes: The coil voltage and coil current of the flux valve assembly for each stator segment are collected, and the results are based on the coil voltage, coil current, and the corresponding coil resistance and number of coil turns. The coil voltage at different times is recorded to form a pair of adjacent time point data for numerical calculation. Based on the number of coil turns and the time period, the coil voltage component is mapped to an estimated value of the change in flux linkage within the sampling time interval, thus obtaining the flux linkage increment within that interval. This increment is then divided by the sampling period length to obtain the rate of change of flux linkage within that period.

6. The DC permanent magnet motor speed control device of claim 1, wherein: The construction of the boundary induced potential imbalance index based on the difference in flux change rate between adjacent stator segments includes: According to the circumferential order of the stator segments, adjacent stator segments are grouped into a boundary pair; The flux linkage change rates of the two stator segments within each boundary pair are compared to obtain the flux linkage change rate difference at the boundary position. The flux linkage change rate difference is used to represent the difference in the dynamic behavior of the flux linkage of the two segments at the boundary under a time-varying magnetic field. By aggregating the differences in flux change rates at each boundary location, and by performing absolute value processing, amplitude amplification processing, and normalization processing on the differences, all boundary differences can be transformed into a single comprehensive quantitative parameter; and by summing and squaring, the boundary induced potential imbalance index can be obtained.

7. A DC permanent magnet motor speed control device according to claim 6, characterized in that: The controller is configured to generate a target coupling capability in dependence on a deviation of a target rotational speed from an actual rotational speed, and to generate the stator segment flux valve assembly control quantities so as to minimize the boundary induction potential imbalance indicator to constrain or optimize one of the targets; The controller is configured to acquire the target speed n and the actual speed n1, calculate the speed deviation e, and generate a target coupling capability τ based on the speed deviation e, wherein the target coupling capability τ is used to characterize the target torque transmission level or target coupling strength level that the effective coupling area should achieve.

8. A DC PM motor speed control device according to claim 7, characterized in that: The controller is configured to generate control quantities vk for the respective stator segment flux valve assemblies such that an actual coupling capability τ1 formed collectively by the control quantities vk tracks the target coupling capability τ, and to take into account a boundary induced voltage imbalance indicator As one of the constraints or optimization targets, a reduction of a difference in a rate of change of flux linkage of adjacent stator segments is reduced; Wherein, the is an index constructed from the difference in the rate of change of flux linkage of adjacent stator segments.

9. A DC PM motor speed control device according to claim 8, characterized in that: The controller is configured to set amplitude constraints and rate of change constraints for the control quantity vk of each stator segment, wherein the amplitude constraint limits vk to be within a preset allowable range, and the rate of change constraint limits the change of vk within the control period Δt to not exceed a preset threshold Δumax, so as to limit the sudden change in flux linkage rate and reduce the induced potential difference at the boundary of adjacent stator segments.

10. The DC permanent magnet motor speed control device according to claim 1, characterized in that: The controller is implemented using a microcontroller, DSP, or FPGA with analog-to-digital converter, timer, PWM output, and digital signal processing capabilities. It includes at least a sampling module, an estimation module, an index construction module, a target generation module, a control quantity solving module, and a drive output module.

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