Motor rotor angle estimation method and device

Abstract

The invention discloses a motor rotor angle estimation method and device. The method comprises the steps of obtaining first back electromotive force of a motor; determining an estimated rotor angle of the motor according to the first back electromotive force; acquiring a second counter electromotive force containing an actual rotor angle of the motor; constructing a third back electromotive force containing the estimated rotor angle and the compensated rotor angle; generating an input error value based on the second back electromotive force and the third back electromotive force; the compensation rotor angle is adjusted, the input error value is controlled to be zero, and the current compensation rotor angle is obtained; and calculating the sum value of the current compensation rotor angle and the estimated rotor angle to obtain the actual rotor angle of the motor. After the error of the input error value is eliminated through the PI controller, the actual rotor angle of the motor can be accurately obtained by combining the current compensation rotor angle and the estimated rotor angle, and extra calibration or complex algorithms are not needed. According to the method, the compensation process of the rotor angle is simplified, the complexity is reduced, the reliability is improved, and meanwhile, the estimation precision of the rotor angle is ensured.

Description

Technical Field

[0001] This application relates to the field of motor control technology, and in particular to a method and apparatus for estimating the rotor angle of a motor. Background Technology

[0002] In hydrogen fuel cell air compressor controllers, sensorless field-oriented control algorithms are typically used to control the speed of permanent magnet synchronous motors. This algorithm can estimate rotor angles in the medium to high speed range, with sliding mode estimation being a commonly used method. However, due to the influence of the algorithm and filters, the estimated angles may have deviations, thus requiring compensation.

[0003] Currently, fixed compensation angles or other open-loop methods are commonly used to compensate for rotor angles. However, due to algorithmic limitations, the compensation angle varies under different speeds and currents, necessitating experimental calibration for different operating conditions, a complex process. Summary of the Invention

[0004] This application provides a method and apparatus for estimating the rotor angle of a motor, in order to solve the problem that the experimental calibration process for different working conditions is quite complicated.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] The first aspect of this application provides a method for estimating the rotor angle of an electric motor, including:

[0007] Obtain the first back electromotive force of the motor;

[0008] The estimated rotor angle of the motor is determined based on the first back electromotive force;

[0009] Obtain the second back electromotive force, which includes the actual rotor angle of the motor;

[0010] Construct a third back electromotive force that includes the estimated rotor angle and the compensated rotor angle;

[0011] An input error value is generated based on the second back electromotive force and the third back electromotive force;

[0012] Adjust the compensation rotor angle to control the input error value to zero, and obtain the current compensation rotor angle;

[0013] Calculate the sum of the current compensated rotor angle and the estimated rotor angle, where the sum is the actual rotor angle of the motor.

[0014] Optionally, determining the estimated rotor angle of the motor based on the first back electromotive force includes:

[0015] The first back electromotive force is filtered to obtain the filtered first back electromotive force.

[0016] The filtered first back electromotive force is calculated to obtain the estimated rotor angle of the motor.

[0017] Optionally, obtaining the second back electromotive force, which includes the actual rotor angle of the motor, includes:

[0018] The product of the cosine of the actual rotor angle and the amplitude of the back electromotive force is determined as the second back electromotive force along the α axis.

[0019] The product of the sine of the actual rotor angle and the amplitude of the back electromotive force is determined to be the second back electromotive force of the β axis;

[0020] The second back electromotive force of the α-axis and the second back electromotive force of the β-axis are determined to be the second back electromotive force of the motor.

[0021] Optionally, the construction of the third back electromotive force, which includes the estimated rotor angle and the compensated rotor angle, includes:

[0022] The cosine of the sum of the estimated rotor angle and the compensated rotor angle is determined as the third back electromotive force of the α-axis;

[0023] The sine of the sum of the estimated rotor angle and the compensated rotor angle is determined as the third back electromotive force along the β axis;

[0024] The third back electromotive force of the α-axis and the third back electromotive force of the β-axis are defined as the third back electromotive force.

[0025] Optionally, generating the input error value based on the second back electromotive force and the third back electromotive force includes:

[0026] Calculate the product of the third back electromotive force along the α-axis and the second back electromotive force along the β-axis to obtain the first product;

[0027] Calculate the product of the third back electromotive force of the β axis and the second back electromotive force of the α axis to obtain the second product;

[0028] Calculate the difference between the first product and the second product to obtain the input error value.

[0029] A second aspect of this application provides a motor rotor angle estimation device, comprising:

[0030] The first sliding mode observer is used to obtain the first back electromotive force of the motor;

[0031] The estimated rotor angle determination module is used to determine the estimated rotor angle of the motor based on the first back electromotive force.

[0032] A second sliding mode observer is used to obtain a second back electromotive force that includes the actual rotor angle of the motor.

[0033] A construction module is used to construct a third back electromotive force that includes the estimated rotor angle and the compensated rotor angle;

[0034] An error value determination module is used to generate an input error value based on the second back electromotive force and the third back electromotive force;

[0035] A PI controller is used to adjust the compensation rotor angle to control the input error value to zero, thereby obtaining the current compensation rotor angle.

[0036] The calculation module is used to calculate the sum of the current compensated rotor angle and the estimated rotor angle, where the sum is the actual rotor angle of the motor.

[0037] Optionally, the rotor angle estimation module includes:

[0038] The filtering module is used to filter the first back electromotive force to obtain the filtered first back electromotive force.

[0039] The phase-locked loop module is used to calculate the filtered first back electromotive force to obtain the estimated rotor angle of the motor.

[0040] Optionally, the second sliding mode observer is also used for:

[0041] The product of the cosine of the actual rotor angle and the amplitude of the back electromotive force is determined as the second back electromotive force along the α axis.

[0042] The product of the sine of the actual rotor angle and the amplitude of the back electromotive force is determined to be the second back electromotive force of the β axis;

[0043] The second back electromotive force of the α-axis and the second back electromotive force of the β-axis are determined to be the second back electromotive force of the motor.

[0044] Optionally, the building module is further configured to:

[0045] The cosine of the sum of the estimated rotor angle and the compensated rotor angle is determined as the third back electromotive force of the α-axis;

[0046] The sine of the sum of the estimated rotor angle and the compensated rotor angle is determined as the third back electromotive force along the β axis;

[0047] The third back electromotive force of the α-axis and the third back electromotive force of the β-axis are defined as the third back electromotive force.

[0048] Optionally, the error value determination module is further configured to:

[0049] Calculate the product of the third back electromotive force along the α-axis and the second back electromotive force along the β-axis to obtain the first product;

[0050] Calculate the product of the third back electromotive force of the β axis and the second back electromotive force of the α axis to obtain the second product;

[0051] Calculate the difference between the first product and the second product to obtain the input error value.

[0052] The technical solution provided in this application involves: obtaining a first back electromotive force (EMF) of the motor; determining an estimated rotor angle based on the first EMF; obtaining a second back EMF containing the actual rotor angle of the motor; constructing a third back EMF containing the estimated rotor angle and the compensated rotor angle; generating an input error value based on the second and third back EMFs; adjusting the compensated rotor angle to control the input error value to zero, thus obtaining the current compensated rotor angle; and calculating the sum of the current compensated rotor angle and the estimated rotor angle to obtain the actual rotor angle of the motor. By eliminating the error in the input error value through a PI controller, and combining the current compensated rotor angle and the estimated rotor angle, the actual rotor angle of the motor can be accurately obtained without additional calibration or complex algorithms. This method simplifies the rotor angle compensation process, reduces complexity, improves reliability, and ensures the accuracy of rotor angle estimation. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of this application 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 of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 A flowchart illustrating a method for estimating the rotor angle of a motor, as provided in this application embodiment;

[0055] Figure 2 A schematic diagram illustrating a sliding mode observer method for rotor angle estimation provided in an embodiment of this application;

[0056] Figure 3 This is a schematic diagram of the architecture of a motor rotor angle estimation device provided in an embodiment of this application. Detailed Implementation

[0057] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0058] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0059] like Figure 1 The flowchart shown is a method for estimating the rotor angle of a motor provided in this embodiment, including the following steps:

[0060] S101: Obtain the first back electromotive force of the motor.

[0061] The first back electromotive force (EMF) of the motor can be obtained through a first sliding mode observer, which is a general-purpose sliding mode observer. The first back EMF includes the initial back EMF of the α-axis (i.e., Ealpha1) and the initial back EMF of the β-axis (i.e., Ebeta1).

[0062] Specifically, the three-phase current and three-phase voltage of the motor are collected and transformed into a two-phase stationary coordinate system to obtain two-phase current and two-phase voltage; the two-phase current and two-phase voltage are then input into the first sliding mode observer to obtain the first back electromotive force of the motor.

[0063] Alternatively, the first sliding mode observer calculates the first back electromotive force by combining the stator current, voltage, and motor model of the motor.

[0064] S102: Determine the estimated rotor angle of the motor based on the first back electromotive force.

[0065] Optionally, the first back electromotive force can be calculated using a phase-locked loop module to obtain the estimated rotor angle of the motor.

[0066] Optionally, in another embodiment of this application, the specific implementation of step S102 includes processes A1 to A2.

[0067] A1: Filter the first back EMF to obtain the filtered first back EMF.

[0068] The first back electromotive force can be filtered using a filter.

[0069] It should be noted that, since the output of the first sliding mode observer has a large jitter, it needs to be filtered to obtain the first back electromotive force after filtering as Ealpha1Fil and Ebeta1Fil.

[0070] A2: Calculate the first back electromotive force after filtering to obtain the estimated rotor angle of the motor.

[0071] Understandably, the estimated rotor angle of the motor can be effectively calculated by using a phase-locked loop (PLL) module to calculate the filtered first back electromotive force (EMF). Specifically, the PLL module tracks the phase of the first back EMF to estimate the motor rotor angle, thus obtaining the estimated rotor angle of the motor.

[0072] S103: Obtain the second back electromotive force, which includes the actual rotor angle of the motor.

[0073] Specifically, a second back electromotive force (EMF) containing the actual rotor angle of the motor can be obtained through a second sliding mode observer. The second sliding mode observer is a constant velocity approaching law, delay-free sliding mode observer. The second back EMF includes at least the second back EMF along the α-axis and the second back EMF along the β-axis.

[0074] Understandably, due to the significant output jitter of general sliding mode observers, a constant-velocity reaching law, delay-free sliding mode observer is typically used, with a filter added to the output. The rotor angle is estimated using the filtered α and β-axis back EMFs. However, the improved sliding mode reaching law and the filter introduce phase delay, causing the phases of Ealpha1Fil and Ebeta1Fil to lag behind the actual phases. Consequently, the estimated rotor angle obtained from phase-locked loops also exhibits phase delay. Therefore, steps S104 to S107 are required to compensate for the estimated rotor angle.

[0075] It is important to emphasize that since the actual rotor angle cannot be directly extracted from the second back electromotive force, it is necessary to estimate the rotor angle and compensate for the rotor angle difference determined by the first back electromotive force in order to calculate the accurate rotor angle subsequently.

[0076] It should be noted that the filter has not yet been added when performing step S103. Therefore, the actual rotor angle included in the determination of the second back EMF based on the second sliding mode observer is only an approximation and not the true rotor angle of the motor.

[0077] Optionally, in another embodiment of this application, the specific implementation of step S103 includes processes B1 to B4.

[0078] B1: Determine the second back electromotive force of the α-axis as the product of the cosine of the actual rotor angle and the amplitude of the back electromotive force.

[0079] The specific form of the second back electromotive force along the α axis is as follows: .in, E is the actual rotor angle, E is the back electromotive force amplitude, and Ealpha2 is the second back electromotive force of the α axis.

[0080] B2: The product of the sine of the actual rotor angle and the amplitude of the back electromotive force is determined as the second back electromotive force of the β axis.

[0081] The specific form of the second back electromotive force along the β axis is as follows: Where Ebeta2 is the second back electromotive force along the β axis.

[0082] B3: Determine the second back EMF of the α-axis and the second back EMF of the β-axis as the second back EMF of the motor.

[0083] Specifically, the specific manifestation of the second back electromotive force is shown in formula (1).

[0084] (1)

[0085] S104: Construct a third back electromotive force that includes estimating the rotor angle and compensating for the rotor angle.

[0086] The third back electromotive force includes at least the third back electromotive force along the α-axis and the third back electromotive force along the β-axis.

[0087] Optionally, in another embodiment of this application, the specific implementation of step S104 includes processes C1 to C3.

[0088] C1: Determine the third back electromotive force of the estimated rotor angle and the cosine of the sum of the compensated rotor angles as the α-axis.

[0089] The specific form of the third back electromotive force along the α axis is as follows: Where Ealpha3 is the third back electromotive force along the α axis. To estimate the rotor angle, To compensate for the rotor angle.

[0090] C2: Determine the third back electromotive force of the sine of the estimated rotor angle and the sum of the compensated rotor angles as the β-axis.

[0091] The specific form of the third back electromotive force along the β axis is as follows: Where Ebeta3 is the third back electromotive force along the β axis.

[0092] C3: Determine the third back electromotive force along the α-axis and the third back electromotive force along the β-axis as the third back electromotive force.

[0093] The specific manifestation of the third back electromotive force is shown in formula (2).

[0094] (2)

[0095] S105: Generate input error values ​​based on the second and third back EMFs.

[0096] In step S105, an input error value is generated based on the second back electromotive force and the third back electromotive force. Specifically, the third back electromotive force along the α-axis and the third back electromotive force along the β-axis are obtained from the third back electromotive force, and the second back electromotive force along the α-axis and the second back electromotive force along the β-axis are obtained from the second back electromotive force. The input error value is determined based on the third back electromotive force along the α-axis, the third back electromotive force along the β-axis, the second back electromotive force along the α-axis, and the second back electromotive force along the β-axis.

[0097] Optionally, in another embodiment of this application, the specific implementation of step S104 includes processes D1 to D3.

[0098] D1: Calculate the product of the third back electromotive force along the α-axis and the second back electromotive force along the β-axis to obtain the first product.

[0099] The specific form of the first product is as follows: .

[0100] D2: Calculate the product of the third back electromotive force along the β axis and the second back electromotive force along the α axis to obtain the second product.

[0101] The specific form of the second product is as follows: .

[0102] D3: Calculate the difference between the first product and the second product to obtain the input error value.

[0103] The specific form of the input error value is shown in formula (3).

[0104] (3)

[0105] In formula (3), Let be the input error value of the PI controller, where formula (3) can be transformed into formula (4).

[0106] (4)

[0107] It should be noted that the input error value contains some high-frequency jitter components (i.e., the second back EMF), which affect the accuracy of the back EMF. Therefore, the input error value needs to be filtered to remove the high-frequency components and retain only its DC component. The DC component represents the stable part of the back EMF, which is directly related to the rotor angle change of the motor and can be used for more accurate angle estimation and control.

[0108] S106: Adjust the compensation rotor angle to control the input error value to zero and obtain the current compensation rotor angle.

[0109] Specifically, it can be seen from formula (4) that when Approximately hour, Since the input error value approaches 0, the PI controller is used to adjust the compensation rotor angle so that the input error value is controlled to zero, thus obtaining the current compensation rotor angle.

[0110] S107: Calculate the sum of the current compensated rotor angle and the estimated rotor angle. The sum is the actual rotor angle of the motor.

[0111] Understandably, when the input error value is zero, it indicates that the PI controller has been successfully adjusted, eliminating the error between the estimated rotor angle and the actual rotor angle. The PI controller continuously adjusts to ensure the input error value is close to zero, thereby precisely matching the estimated angle and the actual angle to achieve an ideal control state. Under these conditions, the compensated rotor angle can be considered accurate, stable, and error-free.

[0112] In order to better understand Figure 1 The content shown is explained below. See also: Figure 2The diagram illustrates a sliding mode observer method for rotor angle estimation. First, the back electromotive forces Ealpha1 and Ebeta1 (i.e., the first back electromotive force) of the α-axis and β-axis are calculated using a first sliding mode observer. Since the output of the first sliding mode observer has significant jitter, it needs to be filtered. After filtering, Ealpha1Fil and Ebeta1Fil are obtained. Then, the estimated rotor angle is obtained through a phase-locked loop module. However, this estimated rotor angle will have a phase delay and is therefore inaccurate. In this application, in order to eliminate phase delay, the rotor angle estimation method provided in the embodiments of this application is used to compensate for the rotor angle θ obtained by the sliding mode observer method. Specifically, the third back electromotive force (i.e., Ealpha3 and Ebeta3) and the second back electromotive force (i.e., Ealpha2 and Ebeta2) are first obtained. The input error value is determined based on the third back electromotive force and the second back electromotive force. The input error value is filtered to obtain the filtered input error value. The compensation rotor angle is adjusted by the PI controller so that the filtered input error value is controlled to zero, and the current compensation rotor angle is obtained. The sum of the current compensation rotor angle and the estimated rotor angle is calculated, and the sum is the actual rotor angle of the motor.

[0113] In summary, by eliminating input error values ​​through a PI controller and combining the current compensated rotor angle with the estimated rotor angle, the actual rotor angle of the motor can be accurately obtained without additional calibration or complex algorithms. This method simplifies the rotor angle compensation process, reduces complexity, improves reliability, and ensures the accuracy of rotor angle estimation.

[0114] like Figure 3 The diagram shown is a schematic of the architecture of a motor rotor angle estimation device provided in an embodiment of this application. The estimation device includes: a first sliding mode observer 100, a rotor angle estimation determination module 200, a second sliding mode observer 300, a construction module 400, an error value determination module 500, a PI controller 600, and a calculation module 700.

[0115] The first sliding mode observer 100 is used to obtain the first back electromotive force of the motor.

[0116] The rotor angle estimation module 200 is used to determine the estimated rotor angle of the motor based on the first back electromotive force.

[0117] The rotor angle estimation and determination module 200 includes:

[0118] The filtering module is used to filter the first back electromotive force to obtain the filtered first back electromotive force.

[0119] The phase-locked loop module is used to calculate the filtered first back electromotive force to obtain the estimated rotor angle of the motor.

[0120] The second sliding mode observer 300 is used to obtain the second back electromotive force, which includes the actual rotor angle of the motor.

[0121] The second sliding mode observer 300 is also used to determine the product of the cosine of the actual rotor angle and the amplitude of the back electromotive force as the second back electromotive force of the α axis; to determine the product of the sine of the actual rotor angle and the amplitude of the back electromotive force as the second back electromotive force of the β axis; and to determine the second back electromotive force of the α axis and the second back electromotive force of the β axis as the second back electromotive force of the motor.

[0122] Module 400 is used to construct a third back electromotive force, which includes the estimated rotor angle and the compensated rotor angle.

[0123] The construction module 400 is also used to determine the third back electromotive force (EMF) of the estimated rotor angle and the sum of the compensated rotor angles as the cosine of the sum of the estimated rotor angles and the sum of the compensated rotor angles as the third back EMF of the β-axis; and to determine the third back EMF of the α-axis and the third back EMF of the β-axis as the third back EMF.

[0124] The error value determination module 500 is used to generate an input error value based on the second back electromotive force and the third back electromotive force.

[0125] The error value determination module 500 is also used to calculate the product of the third back electromotive force of the α-axis and the second back electromotive force of the β-axis to obtain the first product; calculate the product of the third back electromotive force of the β-axis and the second back electromotive force of the α-axis to obtain the second product; and calculate the difference between the first product and the second product to obtain the input error value.

[0126] The PI controller 600 is used to adjust the compensation rotor angle to control the input error value to zero and obtain the current compensation rotor angle.

[0127] The calculation module 700 is used to calculate the sum of the current compensated rotor angle and the estimated rotor angle, which is the actual rotor angle of the motor.

[0128] In summary, by eliminating input error values ​​through a PI controller and combining the current compensated rotor angle with the estimated rotor angle, the actual rotor angle of the motor can be accurately obtained without additional calibration or complex algorithms. This method simplifies the rotor angle compensation process, reduces complexity, improves reliability, and ensures the accuracy of rotor angle estimation.

[0129] 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. In particular, for system or system embodiments, since they are fundamentally similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. Components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0130] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0131] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. 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 this application. Therefore, this application 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 method of estimating the angle of a rotor of an electric machine, characterized by, The method comprises the following steps: acquiring a first back electromotive force of a motor; determining an estimated rotor angle of the motor according to the first back electromotive force; acquiring a second back electromotive force containing an actual rotor angle of the motor; constructing a third back electromotive force containing the estimated rotor angle and a compensation rotor angle; generating an input error value based on the second back electromotive force and the third back electromotive force; adjusting the compensation rotor angle so that the input error value is controlled to zero to obtain a current compensation rotor angle; calculating a sum value of the current compensation rotor angle and the estimated rotor angle, and the sum value is the actual rotor angle of the motor.

2. The method of claim 1, wherein, The step of determining the estimated rotor angle of the motor according to the first back electromotive force comprises the following steps: filtering the first back electromotive force to obtain a filtered first back electromotive force; calculating the filtered first back electromotive force to obtain the estimated rotor angle of the motor.

3. The method of claim 1, wherein, The step of acquiring the second back electromotive force containing the actual rotor angle of the motor comprises the following steps: determining a product of a cosine of the actual rotor angle and a back electromotive force amplitude as a second back electromotive force of an alpha axis; determining a product of a sine of the actual rotor angle and the back electromotive force amplitude as a second back electromotive force of a beta axis; determining the second back electromotive force of the alpha axis and the second back electromotive force of the beta axis as the second back electromotive force of the motor.

4. The method of claim 3, wherein, The step of constructing the third back electromotive force containing the estimated rotor angle and the compensation rotor angle comprises the following steps: determining a cosine of a sum value of the estimated rotor angle and the compensation rotor angle as a third back electromotive force of an alpha axis; determining a sine of the sum value of the estimated rotor angle and the compensation rotor angle as a third back electromotive force of a beta axis; determining the third back electromotive force of the alpha axis and the third back electromotive force of the beta axis as the third back electromotive force.

5. The method of claim 4, wherein, The step of generating the input error value based on the second back electromotive force and the third back electromotive force comprises the following steps: calculating a product of the third back electromotive force of the alpha axis and the second back electromotive force of the beta axis to obtain a first product; calculating a product of the third back electromotive force of the beta axis and the second back electromotive force of the alpha axis to obtain a second product; calculating a difference value of the first product and the second product to obtain the input error value.

6. A motor rotor angle estimation device, characterized in that, The method comprises the following steps: a first sliding mode observer is used to acquire a first back electromotive force of a motor; an estimated rotor angle determination module is used to determine an estimated rotor angle of the motor according to the first back electromotive force; a second sliding mode observer is used to acquire a second back electromotive force containing an actual rotor angle of the motor; a construction module is used to construct a third back electromotive force containing the estimated rotor angle and a compensation rotor angle; an error value determination module is used to generate an input error value based on the second back electromotive force and the third back electromotive force; a PI controller is used to adjust the compensation rotor angle so that the input error value is controlled to zero to obtain a current compensation rotor angle; a calculation module is used to calculate a sum value of the current compensation rotor angle and the estimated rotor angle, and the sum value is the actual rotor angle of the motor.

7. The apparatus of claim 6, wherein, The estimated rotor angle determination module comprises the following steps: a filtering module is used to filter the first back electromotive force to obtain a filtered first back electromotive force; a phase-locked loop module configured to calculate the filtered first back EMF to obtain an estimated rotor angle of the motor.

8. The apparatus of claim 6, wherein, The second sliding mode observer is further configured to: determine a product of a cosine of an actual rotor angle and a back EMF amplitude as a second back EMF of an α-axis; determine a product of a sine of the actual rotor angle and the back EMF amplitude as a second back EMF of a β-axis; determine the second back EMF of the α-axis and the second back EMF of the β-axis as a second back EMF of the motor.

9. The apparatus of claim 8, wherein, The constructing module is further configured to: determine a cosine of a sum of the estimated rotor angle and a compensated rotor angle as a third back EMF of the α-axis; determine a sine of the sum of the estimated rotor angle and the compensated rotor angle as a third back EMF of the β-axis; determine the third back EMF of the α-axis and the third back EMF of the β-axis as a third back EMF.

10. The apparatus of claim 9, wherein, The error value determining module is further configured to: calculate a product of the third back EMF of the α-axis and the second back EMF of the β-axis to obtain a first product; calculate a product of the third back EMF of the β-axis and the second back EMF of the α-axis to obtain a second product; calculate a difference between the first product and the second product to obtain an input error value.

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