Permanent magnet synchronous motor sensorless control method based on dynamic position error

Abstract

The application discloses a kind of permanent magnet synchronous motor position sensorless control method based on dynamic position error.Propose transition phase, contrast between the first position error signal obtained based on high-frequency signal injection method and the second position error signal obtained based on sliding film observer, standardize the position error of estimation between the two, dynamically determine the best switching speed point, and use nonlinear weighting function to smooth fusion two kinds of position error, finally get the estimated position and speed through phase-locked loop;Finally, according to the estimated speed, different error signals are used for position tracking.The application overcomes the problem of estimated value pulsation and jump caused by the dependence of traditional method on fixed experience switching point, realizes the smooth and adaptive switching of two estimation methods in full-speed range, significantly improves the control accuracy and operation stability of the system, and has simple structure and is easy to implement in engineering.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and more specifically to a sensorless control method for a permanent magnet synchronous motor (PMSM), and particularly to a sensorless control method for a permanent magnet synchronous motor based on dynamic position error. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in industrial drives, electric vehicles, and home appliances due to their advantages such as high efficiency, high power density, compact structure, and high reliability, thus becoming one of the mainstream technologies for AC motor system control. Traditional PMSMs rely heavily on mechanical position or speed sensors (such as rotary encoders and rotary transformers) for speed and position control. While these can directly obtain the rotor angle, they have serious shortcomings in terms of system cost, size, and maintainability.

[0003] In response, sensorless control technology has emerged. Currently, the mainstream sensorless control methods fall into two main categories: high-frequency signal injection (HF) and back-EMF (back-EMF) methods.

[0004] The HF method alone is suitable for startup or low-speed ranges, while the back EMF method is suitable for medium- and high-speed ranges. Achieving smooth, accurate, and stable sensorless control across the entire speed range is a challenge.

[0005] To cover the entire operating range from zero speed to high speed, researchers have proposed various composite or hybrid control strategies. For example, some schemes use high-frequency injection to obtain the initial position during startup and low-speed phases, switching to a back-EMF observer after the speed increases; other methods attempt to fuse the high-frequency response envelope and flux linkage observation signals, achieving cross-speed domain estimation through normalization processing. However, existing technologies still face several common challenges in practical applications:

[0006] 1. Stable and accurate control is difficult to achieve across the full speed threshold (from standstill / zero speed to high speed);

[0007] 2. Lacks a smooth, low-jitter switching strategy for low-speed to medium-speed to high-speed transitions;

[0008] 3. It lacks robustness and adaptability to changes in motor parameters, load, temperature, saturation, and noise.

[0009] Therefore, overcoming the above-mentioned shortcomings is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0010] In view of the above problems, and in order to at least partially solve the above technical problems, this application proposes a sensorless control method for permanent magnet synchronous motors based on dynamic position error. To achieve the above objective, the present invention adopts the following technical solution:

[0011] In a first aspect, embodiments of the present invention provide a sensorless control method for a permanent magnet synchronous motor based on dynamic position error, comprising the following steps:

[0012] The first position error signal is obtained by high-frequency signal injection, and the second position error signal is obtained by a synovial observer.

[0013] Define a speed switching function that dynamically adjusts the weights of the two error signals based on the comparison between the current speed and the preset switching speed point.

[0014] Based on the weights, the first position error signal and the second position error signal are weighted and fused to obtain a composite position error signal;

[0015] The composite position error signal is input into the phase-locked loop, and the estimated rotational speed and estimated rotor position are output.

[0016] The permanent magnet synchronous motor is controlled based on the estimated rotational speed and estimated rotor position.

[0017] Preferably, the speed switching function satisfies:

[0018]

[0019] In the formula, For the current estimated rotational speed, For switching speed, This is the curve slope parameter, used to control the length of the switching interval.

[0020] Preferably, the switching speed is determined in the following way:

[0021] Low-pass filtering is applied to the first position error signal and the second position error signal;

[0022] When the absolute values ​​of the first position error signal and the second position error signal after filtering are equal, the current rotational speed is used as the switching speed.

[0023] Preferably, position tracking is performed using different error signals based on the estimated rotational speed, including: dividing the entire speed domain into low-speed, transition, and high-speed stages based on the estimated rotational speed, wherein the division is based on:

[0024] Low speed phase ( );

[0025] Transition phase ( );

[0026] High-speed phase ( );

[0027] in, To estimate the rotational speed, For switching speed, To switch the half-width of the interval.

[0028] Preferably, position tracking is performed using different error signals based on the estimated rotational speed, including: dividing the entire speed domain into low-speed, transition, and high-speed stages based on the estimated rotational speed, wherein:

[0029] In the low-speed phase, position estimation is performed using only the position error signal extracted by the high-frequency signal injection method.

[0030] During the high-speed phase, position estimation is performed using only the position error signal extracted by the sliding mode observer method;

[0031] During the transition phase, position estimation is performed using composite position error signals.

[0032] Preferably, the first position error signal is obtained by a high-frequency signal injection method, including:

[0033] Construct a high-frequency mathematical model of a permanent magnet synchronous motor in a rotating dq-axis coordinate system;

[0034] A symmetrical square wave high-frequency voltage signal is injected into the estimated d-axis;

[0035] The high-frequency current response envelope signal in the α-β coordinate system is obtained through coordinate transformation;

[0036] The first position error signal of the rotor is extracted by vector cross product operation.

[0037] Preferably, the second position error signal is obtained through a synovial observer, including:

[0038] Construct a mathematical model of a permanent magnet synchronous motor in a stationary α-β axis coordinate system;

[0039] Design a sliding mode observer to estimate the stator current;

[0040] The equivalent back electromotive force signal output by the observer is extracted, and the second position error signal of the rotor is extracted by vector cross product.

[0041] Preferably, the composite position error signal is input into the phase-locked loop, and the estimated rotational speed and estimated rotor position are output according to the following formula:

[0042]

[0043]

[0044] In the formula, To estimate the rotational speed, This represents the composite position error signal. This represents the proportional gain of the phase-locked loop structure. This represents the integral gain of the phase-locked loop structure. To estimate the rotor position.

[0045] Secondly, embodiments of the present invention provide a sensorless control system for a permanent magnet synchronous motor based on dynamic position error. The system includes a processor and a memory, the memory storing a computer program, and the processor executing the computer program to implement the sensorless control method for a permanent magnet synchronous motor based on dynamic position error as described in any of the preceding claims.

[0046] This invention aims to provide a sensorless composite control method for permanent magnet synchronous motors based on dynamic position error and an adaptive switching strategy. It includes a dynamic position error threshold and an adaptive weighting algorithm to address estimation errors and pulsations generated during the switching process in traditional control methods, ensuring smooth operation across the entire speed range. Compared with existing technologies, this invention offers higher control accuracy and better robustness, effectively solving the problem that existing technologies cannot simultaneously satisfy full-speed-range operation, high-precision control, and robustness, and has broad application prospects.

[0047] Specifically, the beneficial effects of the present invention include at least the following:

[0048] 1. Innovatively, a method is proposed to determine the optimal switching timing based on the standardized estimation of position error. When the estimation errors of the high-frequency injection method and the sliding mode observer method are similar, the switching process is automatically triggered, so that the selection of the switching point has a clear theoretical basis and adaptability.

[0049] 2. During the transition phase, a nonlinear Log-Sigmoid function is used to weight and fuse the estimation errors of the two methods, avoiding abrupt changes at the boundary of linear weighting, thereby significantly suppressing the speed and position fluctuations during the switching process.

[0050] This switching strategy not only ensures high-precision estimation across the entire range from zero speed to high speed and enhances robustness to different load conditions, but also simplifies system implementation through a unified phase-locked loop structure, reducing the computational requirements of the processor. This makes the method more practical in engineering while improving system control performance and stability. Attached Figure Description

[0051] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0052] Figure 1 This is a flowchart of the sensorless control method for permanent magnet synchronous motors based on dynamic position error according to the present invention.

[0053] Figure 2 This is a flowchart of a sensorless control method for a permanent magnet synchronous motor based on dynamic position error in one embodiment. Detailed Implementation

[0054] 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.

[0055] To address the issues of switching pulsation, instability, and poor robustness caused by existing technologies relying on fixed thresholds or unverified instantaneous signals during the switching process, this invention discloses a sensorless control method for permanent magnet synchronous motors based on dynamic position error. The aim is to achieve precise control across the entire speed range, particularly seamless transitions during low-speed, transient, and high-speed phases. The core of this method lies in providing a smooth switching mechanism based on online assessment of observer confidence. This mechanism dynamically adjusts the weight of each observer's output signal in the final decision by quantifying the reliability of each observer, thereby achieving truly intelligent, smooth, and robust switching.

[0056] In one embodiment, this invention provides a sensorless control method for a permanent magnet synchronous motor based on dynamic position error, such as... Figure 1 The steps include:

[0057] The first position error signal is obtained by high-frequency signal injection, and the second position error signal is obtained by a synovial observer.

[0058] Define a speed switching function that dynamically adjusts the weights of the two error signals based on the comparison between the current speed and the preset switching speed point.

[0059] Based on the weights, the first position error signal and the second position error signal are weighted and fused to obtain a composite position error signal;

[0060] The composite position error signal is input into the phase-locked loop, and the estimated rotational speed and estimated rotor position are output.

[0061] The permanent magnet synchronous motor is controlled based on the estimated rotational speed and estimated rotor position.

[0062] As a specific implementation scheme of this embodiment, the overall process is as follows: Figure 2 .

[0063] In one optional embodiment, obtaining the first position error signal via a high-frequency signal injection method includes:

[0064] 1. Construct a high-frequency mathematical model of an embedded permanent magnet synchronous motor (IPMSM) in a rotating dq-axis coordinate system:

[0065]

[0066] In the formula, , The voltage component of IPMSM in the dq axis coordinate system; , R represents the current component in the dq-axis coordinate system; R is the stator resistance. , For dq axis inductance; For rotor permanent magnet flux linkage; Electric angular velocity; Represents the differential operator.

[0067] Since the frequency of the injected square wave signal is much higher than the fundamental frequency, the effects of the voltage drop across the stator resistance and the back electromotive force of the high-frequency injected signal can be ignored. Therefore, the mathematical model of IPMSM in the high-frequency case is:

[0068]

[0069] In the formula, , , , This represents the voltage and current components in the dq-axis coordinate system at high frequencies, where the superscript... Represents a rotated dq-axis coordinate system, subscript It represents a high-frequency quantity.

[0070] 2. Inject a symmetrical square wave high-frequency voltage signal into the estimated d-axis; wherein, the symmetrical square wave high-frequency voltage signal is:

[0071]

[0072] In the formula, , To estimate the high-frequency voltage components injected along the dq axis, The amplitude of the injected voltage signal, Indicates sampling time, superscript This represents the estimated dq-axis coordinate system.

[0073] 3. Obtain the high-frequency current response envelope signal in the α-β coordinate system through coordinate transformation; in this embodiment, the actual rotor position is... The estimated rotor position is Position error The envelope information of the high-frequency response current in the stationary α-β axis system, obtained through coordinate transformation, is as follows:

[0074]

[0075] in, Indicates the inductance difference; The envelope signal representing the phase response of high-frequency current; Indicates the sampling period. This represents the amplitude of the high-frequency injection voltage, when the position error... When the envelope current is small, the response is similar to Approximately linear correlation.

[0076] 4. Extract the rotor position error signal through vector cross product operation.

[0077] In some implementation schemes, to avoid the influence of changes in inductance parameters, the envelope signal is first normalized:

[0078]

[0079] In the formula, , This represents the normalized envelope signal components. This represents the magnitude of the envelope vector.

[0080] Then, the position error signal is extracted using the vector cross product method. :

[0081]

[0082] In one optional embodiment, a second position error signal is obtained via a synovial observer; including:

[0083] 5. Establish a mathematical model of IPMSM in a stationary coordinate system. The mathematical model expression of the motor in the axial coordinate system is:

[0084]

[0085] In the formula: , The voltage components are in the α-β axis coordinate system; , The current components are in the α-β axis coordinate system; , This is the back electromotive force term of the motor, which contains information about the motor rotor's electrical angle and electrical angular velocity. Its expression is:

[0086]

[0087] Rewritten as the current equation:

[0088]

[0089] 6. Design a sliding mode observer and construct a sliding mode observer to estimate the stator current;

[0090]

[0091] In the formula: , The current component observed by the sliding mode observer is indicated by the superscript "^".

[0092] and The control input for the sliding mode observer can be expressed by the following formula:

[0093]

[0094] In the formula: sat For symbolic functions, This represents the sliding mode gain, which is a positive number.

[0095] 7. Extract the equivalent back electromotive force signal output by the observer, and extract the rotor position error signal through vector cross product.

[0096] Specifically, on the synovial surface, the control input... , Approaching back electromotive force , .right , Perform per-unit processing:

[0097]

[0098] in, , This represents the normalized back electromotive force of the motor.

[0099] Position error signal is extracted using the vector cross product method. :

[0100]

[0101] In one optional embodiment, a speed switching function is defined to dynamically adjust the weights of the two error signals based on a comparison between the current speed and a preset switching speed point; in this embodiment, this step includes:

[0102] 8. Monitor and estimate position errors, and obtain the estimated position errors of both methods in real time:

[0103]

[0104] As a preferred implementation, step 9 is further performed;

[0105] 9. Low-pass filtering: Due to the pulsation in the estimated position error, a low-pass filter (LPF) is used to extract the fundamental frequency error signal.

[0106]

[0107] 10. Determining the switching speed point: Traditional methods typically switch at an empirical value of 10% to 20% of the rated speed. This fails to fully consider the dynamic performance differences between the two estimation methods under different operating conditions, easily leading to significant pulsations or even jumps in the speed and position estimations at the moment of switching. This application uses the speed corresponding to when the absolute values ​​of the two errors are equal after filtering as the switching speed point. ,Right now:

[0108]

[0109] 11. Further, a switching function is defined. This invention uses the Log-Sigmoid function as the switching function:

[0110]

[0111] In the formula, For the current estimated rotational speed, For switching speed, The slope parameter is used to control the length of the switching interval. In this application, the switching function... The value range is [0,1]. The weights of the two error signals are dynamically adjusted using a switching function:

[0112] when << , ≈0, mainly using high-frequency injection method;

[0113] when >> , ≈1, mainly using the synovial observation method.

[0114] In one optional embodiment, the first position error signal and the second position error signal are weighted and fused based on the weights to obtain a composite position error signal;

[0115] 12. The weighting process of the composite position error signal is as follows:

[0116]

[0117] In one optional embodiment, the composite position error signal is input into a phase-locked loop, and the estimated rotational speed and estimated rotor position are output.

[0118] 13. Inputting the composite position error signal into the phase-locked loop includes:

[0119] PI controller: Estimates speed based on error output.

[0120]

[0121] Integrator: Integrates the estimated velocity to obtain the estimated position.

[0122]

[0123] In the formula, To estimate the rotational speed, This represents the composite position error signal. This represents the proportional gain of the phase-locked loop structure. This represents the integral gain of the phase-locked loop structure. To estimate the rotor position.

[0124] Position error signal ( After entering, Responsible for rapid response and providing the main tracking torque; It is responsible for fine-tuning and clearing residual errors. The sum of the outputs of the two is the correction amount for the estimated velocity, which is then integrated to obtain the estimated position.

[0125] In one optional embodiment, position tracking is performed using different error signals based on the estimated rotational speed. In this embodiment, this step includes:

[0126] 14. Full-speed domain operation logic design:

[0127] Low speed phase ( ): Only use .

[0128] Transition phase ( Using weighted error .

[0129] High-speed phase ( ): Only use .

[0130] in, To estimate the rotational speed, For switching speed, To switch the half-width of the interval.

[0131] In one exemplary embodiment, the electrical parameters of the permanent magnet motor are as follows: inductance is L d =5.25mH, L q =12.00mH resistance is R s =0.958Ω, rotor flux is ψ f =0.1827Wb, number of permanent magnet pairs p=4, rated speed 1500rpm, control cycle Ts=0.0002s, motor moment of inertia J=0.03kg·m 2 The coefficient of friction, B, is 0.008. Then perform the complete steps 1-14 described above.

[0132] Finally, through no-load and rated load experiments, the results show that: by using the method of the present invention, the dynamic error of the estimated speed in the transition phase is reduced by about 60% compared with the traditional empirical switching method, and the pulsation amplitude of the estimated position error is reduced by about 55%, thus successfully realizing smooth, high-precision sensorless control across the entire speed range.

[0133] Based on the same inventive concept, this invention also provides a sensorless control system for a permanent magnet synchronous motor based on dynamic position error. The system includes a processor and a memory, the memory storing a computer program. When the processor executes the computer program, it implements the sensorless control method for a permanent magnet synchronous motor based on dynamic position error as described in any of the preceding embodiments. The specific steps of the control method are consistent with the preceding description and will not be repeated here.

[0134] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0135] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sensorless control method for a permanent magnet synchronous motor based on dynamic position error, characterized in that, include: The first position error signal is obtained by high-frequency signal injection, and the second position error signal is obtained by sliding mode observer; Define a speed switching function that satisfies: In the formula, To estimate the rotational speed, The switching speed is determined as follows: when the absolute values ​​of the first position error signal and the second position error signal are equal, the current rotational speed is used as the switching speed. This is the curve slope parameter, used to control the length of the switching interval; Based on the comparison between the current rotational speed and the preset switching speed point, the weights of the first position error signal and the second position error signal are dynamically adjusted. Based on the weights, the first position error signal and the second position error signal are weighted and fused to obtain a composite position error signal; In the formula, This represents the composite position error signal. This represents the speed switching function. This indicates the positional error of the high-frequency injection method. This indicates the position error of the sliding mode observer; The composite position error signal is input into the phase-locked loop, which outputs the estimated rotational speed and the estimated rotor position.

2. The sensorless control method for a permanent magnet synchronous motor according to claim 1, characterized in that, Position tracking is performed using different error signals based on the estimated rotational speed, including: dividing the entire speed domain into low-speed, transition, and high-speed stages based on the estimated rotational speed, wherein the division is based on: Low-speed phase: ; Transition phase: ; High-speed phase: ; in, To estimate the rotational speed, For switching speed, To switch the half-width of the interval.

3. The sensorless control method for a permanent magnet synchronous motor according to claim 1, characterized in that, Position tracking is performed using different error signals based on the estimated rotational speed, including: dividing the full speed domain into low-speed, transition, and high-speed stages based on the estimated rotational speed, wherein: In the low-speed phase, position estimation is performed using only the position error signal extracted by the high-frequency signal injection method. During the high-speed phase, position estimation is performed using only the position error signal extracted by the sliding mode observer method; During the transition phase, position estimation is performed using composite position error signals.

4. The sensorless control method for a permanent magnet synchronous motor according to claim 1, characterized in that, The first position error signal is obtained by high-frequency signal injection, including: Construct a high-frequency mathematical model of a permanent magnet synchronous motor in a rotating dq-axis coordinate system; A symmetrical square wave high-frequency voltage signal is injected into the estimated d-axis; The high-frequency current response envelope signal in the α-β coordinate system is obtained through coordinate transformation; The first position error signal of the rotor is extracted by vector cross product operation.

5. The sensorless control method for a permanent magnet synchronous motor according to claim 1, characterized in that, The second position error signal is obtained through a sliding mode observer, including: Construct a mathematical model of a permanent magnet synchronous motor in a stationary α-β axis coordinate system; Design a sliding mode observer to estimate the stator current; The equivalent back electromotive force signal output by the observer is extracted, and the second position error signal of the rotor is extracted by vector cross product.

6. The sensorless control method for a permanent magnet synchronous motor according to claim 1, characterized in that, The composite position error signal is input into the phase-locked loop, and the estimated rotational speed and estimated rotor position are output according to the following formulas: In the formula, To estimate the rotational speed, This represents the composite position error signal. This represents the proportional gain of the phase-locked loop structure. This represents the integral gain of the phase-locked loop structure. To estimate the rotor position.

7. A sensorless control system for a permanent magnet synchronous motor based on dynamic position error, characterized in that, It includes a processor and a memory, the memory storing a computer program, and the processor executing the computer program to implement the sensorless control method for a permanent magnet synchronous motor based on dynamic position error as described in any one of claims 1 to 6.

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