Motor rotor initial position identification method

Abstract

The invention discloses a method for identifying the initial position of a motor rotor, and relates to the field of motors, and the method comprises the following steps: 1, selecting two vectors with the angle difference of 180 degrees, obtaining two initial D-axis currents corresponding to the vectors, determining an individual with the larger D-axis current through the judgment of the sizes of the two initial D-axis currents, and determining the initial position of the motor rotor according to the individual with the larger D-axis current; judging which vector the current rotor angle is closer to, and determining which vector the rotor angle is closer to as a determined vector according to the maximum D-axis current; and step 2, selecting a vector which has an angle difference of N degrees with the currently determined vector, and obtaining a new D. Compared with the prior art, the invention has the beneficial effects that the invention provides a rapid and reliable motor rotor initial position estimation method without a position sensor, the initial position of the motor can be identified in a very short time, and the accuracy of the motor rotor initial position estimation is improved. And the motor does not rotate in the identification process, and meanwhile, the cost of a motor position sensor is saved.

Description

Technical Field

[0001] The invention relates to the field of motors, and in particular to a method for identifying an initial position of a motor rotor. Background Art

[0002] Most conventional permanent magnet synchronous motors are equipped with a position sensor so that a controller can use the sensor to obtain the motor rotor position and then drive the motor normally.

[0003] At present, many products on the market usually force the motor rotor to a fixed position in the form of pre-positioning when the initial position of the motor rotor is unknown. This method may face the phenomenon of motor reversal during the attraction period, which is not allowed in some products (electric motorcycles, treadmills, etc.); at the same time, for some products that need to start quickly (high-speed hair dryers, vacuum cleaners, etc.), too long pre-positioning time cannot meet product requirements; therefore, the existing method of determining the initial position of the motor rotor in the form of pre-positioning has a small scope of application and needs to be improved. Summary of the invention

[0004] The object of the present invention is to provide a method for identifying the initial position of a motor rotor to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for identifying an initial position of a motor rotor comprises the following steps:

[0007] Step 1, select two vectors with an angle difference of 180°, and obtain two initial D-axis currents corresponding to the vectors (currents used to control the DC component of the rotor magnetic field in motor control). By judging the magnitudes of the two initial D-axis currents, determine the individual with a larger D-axis current, that is, the maximum D-axis current, to determine which vector the current rotor angle is closer to, and the vector to which the rotor angle is closer is the determined vector;

[0008] Step 2, select a vector that differs from the current determined vector by N degrees, obtain a new D-axis current, and determine the magnitude of the new D-axis current and the maximum D-axis current to determine which vector the current rotor angle is closer to;

[0009] Step 3, repeat step 2 until the vector is determined to be the maximum vector, and the error between the maximum vector and the current rotor angle is (N / 2)°.

[0010] As a further solution of the present invention: in step 1, inject voltage vectors V1 at 0° and V7 at 180° to obtain corresponding D-axis currents Id_1 and Id_7. If Id_1 > Id_7, then vector V1 is closer to magnetic pole N than vector V7. As the determined vector, the estimated motor angle Theta_M is 0°. At the same time, the maximum D-axis current Id_max is Id_1. On the contrary, if Id_1 < Id_7, then Theta_M is 180° and Id_max is Id_7, and vector V7 is the determined vector.

[0011] As a further solution of the present invention: step 2 includes the following steps:

[0012] Step 21, determine the injected voltage vector, and the injected voltage vector has an angle difference of N° from the currently determined vector;

[0013] Step 22, obtain a new D-axis current based on the injected voltage vector, and judge the magnitudes of the new D-axis current and the maximum D-axis current to determine which vector the current rotor angle is closer to.

[0014] As a further solution of the present invention: in step 21, based on the determined vector, select to inject voltage vectors V2 or V8. The angle between vector V2 and V1 is 30°, and the angle between V8 and V7 is 30°.

[0015] As a further solution of the present invention: in step 22, if Theta_M is 0° in step 1, then it is necessary to inject vector voltage V2. If Id_2 > Id_max, then vector V2 is closer to magnetic pole N than vector V1. Therefore, Theta_M is 30° and Id_max is Id_2. On the contrary, if Id_2 < Id_max, then Theta_M remains 0° and Id_max is not updated and remains Id_1;

[0016] If Theta_M is 180° in step 1, then it is necessary to inject vector voltage V8. If Id_8 > Id_max, then vector V8 is closer to magnetic pole N than vector V7. Therefore, Theta_M is 210° and Id_max is Id_8. On the contrary, if Id_8 < Id_max, then Theta_M remains 180° and Id_max is not updated and remains Id_7.

[0017] As a further solution of the present invention: in step 3, repeat step 2 until the determined vector is greater than the vectors with an angle difference of N° on both sides to obtain the vector with the largest D-axis current, which is the maximum vector. The error between the maximum vector and the current rotor angle is (N / 2)°.

[0018] As a further solution of the present invention: in step 1, the difference between the values ​​of Id_1 and Id_7 is less than the set value, and then the voltage vectors V4 of 90° and V10 of 270° are applied to further determine the position of the magnetic pole, and obtain currents Id_4 and Id_10. If Id_4>Id_10, the rotor is near the 270° position, otherwise it is near the 90° position.

[0019] Compared with the prior art, the beneficial effects of the present invention are: the present invention provides a method for estimating the initial position of a motor rotor that is fast and reliable and does not require a position sensor. The initial position of the motor can be identified in a very short time, and the motor does not rotate during the identification process. At the same time, the cost of the motor position sensor is saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a flow chart of a method for identifying the initial position of a motor rotor.

[0021] Figure 2 This is a flow chart of the first part of a method for identifying the initial position of a motor rotor.

[0022] Figure 3 This is a flow chart of the second part of a method for identifying the initial position of a motor rotor.

[0023] Figure 4 This is the flow chart of the third part of a method for identifying the initial position of a motor rotor.

[0024] Figure 5 Schematic diagram of the voltage vector corresponding to the D-axis current.

[0025] Figure 6 is a schematic diagram of the position vector.

[0026] Figure 7 Schematic diagram of angle error.

[0027] Figure 8 A schematic diagram of a more precise angle error. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] See also Figure 1 , a method for identifying the initial position of a motor rotor, comprising the following steps:

[0030] Step 1, select two vectors with an angle difference of 180°, and obtain two initial D-axis currents corresponding to the vectors (currents used to control the DC component of the rotor magnetic field in motor control). By judging the magnitudes of the two initial D-axis currents, determine the individual with a larger D-axis current, that is, the maximum D-axis current, to determine which vector the current rotor angle is closer to, and the vector to which the rotor angle is closer is the determined vector;

[0031] Step 2, select a vector that differs from the current determined vector by N degrees, obtain a new D-axis current, and determine the magnitude of the new D-axis current and the maximum D-axis current to determine which vector the current rotor angle is closer to;

[0032] Step 3, repeat step 2 until the vector is determined to be the maximum vector, and the error between the maximum vector and the current rotor angle is (N / 2)°.

[0033] In this example: See Figure 1 , Figure 2 , Figure 3 and Figure 4 In step 1, the voltage vectors V1 of 0° and V7 of 180° are injected to obtain the corresponding D-axis currents Id_1 and Id_7. If Id_1>Id_7, vector V1 is closer to the magnetic pole N than vector V7. To determine the vector, the estimated motor angle Theta_M is 0°. At the same time, the maximum D-axis current Id_max is Id_1. Otherwise, Theta_M is 180°, Id_max is Id_7, and vector V7 is the determined vector.

[0034] In this example: See Figure 1 , Figure 2 , Figure 3 and Figure 4 , step 2 includes the following steps:

[0035] Step 21, determining an injected voltage vector, wherein the injected voltage vector differs from the currently determined vector by an angle of N°;

[0036] Step 22, obtaining a new D-axis current based on the injected voltage vector, and determining the magnitude of the new D-axis current and the maximum D-axis current to determine which vector the current rotor angle is closer to.

[0037] In this example: See Figure 1 , Figure 2 , Figure 3 and Figure 4 In step 21, based on the determined vector, the injection voltage is selected to be vector V2 or V8, the angle difference between vectors V2 and V1 is 30°, and the angle difference between vectors V8 and V7 is 30°.

[0038] In this example: See Figure 1, Figure 2 , Figure 3 and Figure 4 , in step 22, if Theta_M is 0° in step 1, then the vector voltage V2 needs to be injected. If Id_2 > Id_max, then the vector V2 is closer to the magnetic pole N than the vector V1. Therefore, Theta_M is 30° and Id_max is Id_2. Conversely, if Id_2 < Id_max, then Theta_M remains 0° and Id_max is not updated and remains Id_1;

[0039] If Theta_M is 180° in step 1, then the vector voltage V8 needs to be injected. If Id_8 > Id_max, then the vector V8 is closer to the magnetic pole N than the vector V7. Therefore, Theta_M is 210° and Id_max is Id_8. Conversely, if Id_8 < Id_max, then Theta_M remains 180° and Id_max is not updated and remains Id_7.

[0040] In this embodiment: Please refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 , in step 3, repeat step 2 until a vector greater than the vectors with a difference of N° on both sides is determined, and the vector with the largest D-axis current is obtained as the maximum vector. The error between the maximum vector and the current rotor angle is (N / 2)°.

[0041] In this embodiment: Please refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 , in step 1, the difference between the two values of Id_1 and Id_7 is less than the set value (the two values are close, with a small deviation and are prone to misjudgment). Then, apply the voltage vectors V4 at 90° and V10 at 270° to further determine the position of the magnetic pole, and obtain the currents Id_4 and Id_10. If Id_4 > Id_10, then the rotor is near the 270° position; conversely, it is near the 90° position.

[0042] Please refer to Figure 5 , based on the principle that the current responses differently according to the degree of flux saturation, perform rotor position identification. By applying voltage vectors with the same time and amplitude at different angles to obtain the corresponding currents, the closer the current is to the N pole of the rotor, the faster it rises, that is, the larger the amplitude of its current within the same time.

[0043] Please refer to Figure 6For example, initially, 0° vector V1 and 180° vector V7 are selected. When Id_1>IId_7, 30° vector Id_2 is selected. When Id_2>Id_1, it means that the rotor is closer to 30°. Then, vector Id_3 at 60° is selected. When Id_2>Id_3, it is judged that the rotor is near 30°. Based on Id_2>Id_1, d_2>Id_3, the rotor position is between 15° and 45°. Taking 30 degrees as the rotor position, the error is less than 15°. Figure 7 shown.

[0044] If a higher rotor position accuracy is required, the angle difference between adjacent vectors can be smaller, such as 15°, 7.5°, 3.75°, etc. Figure 8 shown.

[0045] The present invention provides a method for estimating the initial position of a motor rotor that is fast and reliable without the need for a position sensor, and can identify the initial position of the motor in a very short time without any rotation of the motor during the identification process, while also saving the cost of the motor position sensor.

[0046] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered as exemplary and non-restrictive in all respects.

[0047] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for identifying the initial position of a motor rotor, characterized in that: The method for identifying the initial position of the motor rotor includes the following steps: Step 1: Select two vectors with an angle difference of 180°, and obtain the initial D-axis currents corresponding to the two sum vectors. By judging the magnitudes of the two initial D-axis currents, determine the one with the larger D-axis current, that is, the maximum D-axis current, to judge which vector the current rotor angle is closer to. The vector that the rotor angle is closer to is the determined vector; Step 2: Select a vector with an angle difference of N° from the current determined vector, obtain a new D-axis current, and judge the magnitudes of the new D-axis current and the maximum D-axis current to judge which vector the current rotor angle is closer to; Step 3: Repeat Step 2 until the determined vector is the maximum vector, and the error between the maximum vector and the current rotor angle is (N / 2)°; 2. The method for identifying the initial position of a motor rotor according to claim 1, characterized in that: In Step 1, inject the voltage vectors V1 at 0° and V7 at 180° to obtain the corresponding D-axis currents Id_1 and Id_7. If Id_1 > Id_7, then the vector V1 is closer to the magnetic pole N than the vector V7, and it is the determined vector. Therefore, the estimated motor angle Theta_M is 0°. At the same time, the maximum D-axis current Id_max is Id_1. On the contrary, Theta_M is 180°, Id_max is Id_7, and the vector V7 is the determined vector; 3. The method for identifying the initial position of a motor rotor according to claim 1, characterized in that: Step 2 includes the following steps: Step 21: Determine the injected voltage vector, and the injected voltage vector has an angle difference of N° from the current determined vector; Step 22: Based on the injected voltage vector, obtain a new D-axis current, and judge the magnitudes of the new D-axis current and the maximum D-axis current to judge which vector the current rotor angle is closer to; 4. The method for identifying the initial position of a motor rotor according to claim 3, characterized in that: In Step 21, based on the determined vector judged, select to inject the voltage vector V2 or V8. The angle between the vector V2 and V1 is 30°, and the angle between V8 and V7 is 30°; 5. The method for identifying the initial position of a motor rotor according to claim 3 or 4, characterized in that: In Step 22, if Theta_M is 0° in Step 1, then it is necessary to inject the vector voltage V2. If Id_2 > Id_max, then the vector V2 is closer to the magnetic pole N than the vector V1. Therefore, Theta_M is 30°, Id_max is Id_2. On the contrary, if Id_2 < Id_max, then Theta_M remains 0°, and Id_max is not updated and remains Id_1; If Theta_M is 180° in Step 1, then it is necessary to inject the vector voltage V8. If Id_8 > Id_max, then the vector V8 is closer to the magnetic pole N than the vector V7. Therefore, Theta_M is 210°, Id_max is Id_8. On the contrary, if Id_8 < Id_max, then Theta_M remains 180°, and Id_max is not updated and remains Id_7; 6. The method for identifying the initial position of a motor rotor according to claim 1, characterized in that: In Step 3, repeat Step 2 until the determined vector is greater than the vectors with an angle difference of N° on both sides to obtain the vector with the largest D-axis current, which is the maximum vector, and the error between the maximum vector and the current rotor angle is (N / 2)°; 7. The method for identifying the initial position of a motor rotor according to claim 2, characterized in that: In step 1, the difference between Id_1 and Id_7 is less than the set value, and then the voltage vector V4 of 90° and V10 of 270° are applied to further determine the position of the magnetic pole and obtain currents Id_4 and Id_10. If Id_4>Id_10, the rotor is near the 270° position, otherwise it is near the 90° position.

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