Method for determining occurrence of zero-crossing in an ac signal and electric machine arrangement

Abstract

A method for determining the occurrence of a zero-crossing point in an AC signal with a fixed frequency for a permanent magnet synchronous motor includes: sampling the AC signal to obtain a plurality of data points; starting to count the number of consecutive data points with the same sign within a detection range to generate a count value, wherein the plurality of data points includes consecutive data points; determining whether the count value is substantially equal to a zero-crossing point determination value; and determining, in response to the count value being equal to the zero-crossing point determination value, that a zero-crossing point has occurred at a last data point of the consecutive data points.

Description

Technical Field

[0001] This invention relates to a permanent magnet synchronous motor (PMSM), and more particularly to a method and related motor device for determining the occurrence of a zero crossing point in an alternating current (AC) signal of a fixed frequency in a permanent magnet synchronous motor, which has high interference immunity and low delay. Background Technology

[0002] For sensorless drive of permanent magnet synchronous motors (hereinafter referred to as "PMSMs"), the rotor position is usually predicted by estimating the fixed-frequency AC signal of the PMSM (e.g., back electromotive force, back EMF). Since the back EMF signal is a signal with alternating positive and negative signs and is similar to a sine wave, the zero-crossing point of the back EMF signal is an important trigger signal for reset position estimation. As long as the rotor position can be corrected according to the time point of the zero-crossing point when the PMSM is driven, the phase change of the stator of the PMSM can be correct.

[0003] The back electromotive force (EMF) signal of a permanent magnet synchronous motor (PMSM) is typically estimated using Kirchhoff's voltage law (KCL). This method introduces sampling noise into the analog-to-digital converter (ADC) sampling of the motor voltage and current, leading to errors in determining the zero-crossing point. In a conventional method for determining the zero-crossing point in the back EMF signal of a PMSM, for example, a low-pass filter is applied to filter the sampling noise. However, this delays the occurrence of the zero-crossing point, and the filtered signal waveform exhibits a phase delay when compared to the original back EMF signal. Therefore, an innovative method with high noise immunity and low delay is urgently needed for determining the zero-crossing point in the back EMF signal of a PMSM. Summary of the Invention

[0004] Therefore, one of the objectives of this invention is to provide a method and related motor device for determining the occurrence of a zero-crossing point in an AC signal with a fixed frequency for a permanent magnet synchronous motor, in order to solve the above-mentioned problems.

[0005] According to an embodiment of the present invention, a method is provided for determining the occurrence of a zero-crossing point in an AC signal having a fixed frequency for a permanent magnet synchronous motor. The method may include: sampling the AC signal to obtain a plurality of data points; starting to count the number of a plurality of consecutive data points having the same sign within a detection range to generate a count value, wherein the plurality of data points includes the plurality of consecutive data points; determining whether the count value is equal to a zero-crossing point determination value; and, in response to the count value being substantially equal to the zero-crossing point determination value, determining that a zero-crossing point has occurred at a last data point of the plurality of consecutive data points.

[0006] According to another embodiment of the present invention, a motor device is provided. The motor device may include a permanent magnet synchronous motor, a sampling circuit, and a processing circuit. The sampling circuit may be coupled to the permanent magnet synchronous motor and may be used to sample an AC signal of the permanent magnet synchronous motor having a fixed frequency to obtain multiple data points. The processing circuit may be coupled to the sampling circuit and may be used to: start counting the number of multiple consecutive data points with the same sign within a detection range to generate a count value, wherein the multiple data points include the multiple consecutive data points; determine whether the count value is substantially equal to a zero-crossing point determination value; and, in response to the count value being substantially equal to the zero-crossing point determination value, determine that a zero-crossing point occurs at a last data point of the multiple consecutive data points.

[0007] One advantage of this invention is that, after generating a comparison result between the rotational speed at a zero-crossing point and the rotational speed limit setting obtained by the method of this invention, if the zero-crossing point is determined to be sampling noise according to the comparison result, this invention can eliminate the sampling noise. In addition, the phase delay between the AC signal with a fixed frequency (e.g., back EMF signal) obtained by the method of this invention and the original AC signal is not too significant. Therefore, the method of this invention can determine the occurrence of a zero-crossing point in the AC signal with a fixed frequency of the permanent magnet synchronous motor under conditions of high immunity and low delay. Attached Figure Description

[0008] Figure 1 This is a block diagram of a motor device according to an embodiment of the present invention.

[0009] Figure 2 This is a schematic diagram illustrating the relationship between rotor position and back electromotive force signal according to an embodiment of the present invention.

[0010] Figure 3 This is a flowchart illustrating the process of generating a count value in Case 1 according to an embodiment of the present invention.

[0011] Figure 4 This is a flowchart illustrating the process of generating a count value in Case 2 according to an embodiment of the present invention.

[0012] Figure 5 According to an embodiment of the present invention Figure 2 A schematic diagram of the data points in region A of the back electromotive force signal.

[0013] Figure 6 This is a flowchart of a method for determining the occurrence of a zero crossover point in the back electromotive force signal of a permanent magnet synchronous motor according to an embodiment of the present invention.

[0014] Figure 7 This is a schematic diagram of the back electromotive force signal according to an embodiment of the present invention. Detailed Implementation

[0015] Figure 1 This is a block diagram of a motor device 10 according to an embodiment of the present invention. The motor device 10 may include a permanent magnet synchronous motor (hereinafter referred to as "permanent magnet synchronous motor") 100, a sampling circuit 102, and a processing circuit 104, wherein the sampling circuit 102 may be coupled to the permanent magnet synchronous motor 100, and the processing circuit 104 may be coupled to the sampling circuit 102. The permanent magnet synchronous motor 100 may include a stator 106 and a rotor 108, wherein the stator 106 may be a three-phase stator winding, and the rotor 108 may be a permanent magnet. A zero-crossing point in the back electromotive force signal of one of the three-phase stator windings can be used to determine the position of the rotor 108. Furthermore, when a zero-crossing point of the back electromotive force signal occurs, the sign of the back electromotive force signal passing through the zero-crossing point can change from positive to negative, or vice versa. It should be noted that the occurrence of the zero crossover point in the back EMF signal is for illustrative purposes only, and the present invention is not limited thereto. In fact, the occurrence of the zero crossover point of the permanent magnet synchronous motor 100 in any other type of AC signal with a fixed frequency (e.g., feedback current signal) falls within the scope of the present invention.

[0016] Figure 2 This is a schematic diagram illustrating the relationship between rotor position and back electromotive force (EMF) signal according to an embodiment of the present invention. To determine the occurrence of a zero-crossing point in the back EMF signal, the sampling circuit 102 first samples the back EMF signal to obtain multiple data points. Then, the processing circuit 104 can be used to set a threshold TH, and based on the threshold TH and its negative value (in... Figure 2A detection range is obtained by marking "-TH" in the middle to determine the occurrence of a zero-crossing point. This detection range has an upper limit, which is the threshold TH, and a lower limit, which is the negative of the threshold TH. For a data point DP (which is any one of multiple data points), the absolute value of the sampled value of data point DP can be compared with the threshold TH by the processing circuit 104. When the absolute value of the sampled value of data point DP is not less than the threshold TH, the sampled value of data point DP is determined to be outside the detection range.

[0017] In response to the sampled value of data point DP being outside the detection range, the processing circuit 104 can set a target data SIGN_TARGET_DATA based on the sign of data point DP to determine whether consecutive data points with the same sign are among multiple data points, where multiple data points include consecutive data points. For example, when the sign of the back electromotive force signal changes from positive to negative at the zero crossing point and the sign of data point DP is positive (i.e., the sampled value of data point DP is not less than the threshold TH), the target data SIGN_TARGET_DATA is set to 1 to begin determining whether consecutive data points with negative signs are among multiple data points (in...). Figure 2 In addition, when the back EMF signal changes from negative to positive at the zero crossover point and the sign of data point DP is negative (that is, the sampled value of data point DP is not greater than the negative of the threshold TH), the sign target data SIGN_TARGET_DATA is set to -1 to begin judging whether consecutive data points with positive sampled values ​​are among multiple data points (in... Figure 2 (The text is marked as "SIGN_TARGET_DATA=-1").

[0018] On the other hand, in response to the sampled value of data point DP being within the detection range (i.e., the absolute value of the sampled value of data point DP being less than the threshold TH), the processing circuit 104 may further be configured to start counting the number of consecutive data points with the same sign based on the sign target data SIGN_TARGET_DATA, to generate a count value, wherein the count value may include a first count value P_N_CC and a second count value N_P_CC, the first count value P_N_CC being generated by counting the number of consecutive data points with negative sign sampled values, and the second count value N_P_CC being generated by counting the number of consecutive data points with positive sign sampled values. Furthermore, the processing circuit 104 may further be configured to set a zero-crossing point judgment value Nmax and determine whether the count value is equal to the zero-crossing point judgment value Nmax. In response to the count value being equal to the zero-crossing point judgment value Nmax, it can be determined that a zero-crossing point has occurred at the last data point of the consecutive data points.

[0019] Table 1

[0020] <![CDATA[ω m (rpm)]]> S1 S2 Nmax 1000 1500 8 8 2000 750 4 4 4000 375 2 2 6000 250 1 2 8000 188 1 2 10000 150 0 2 20000 75 0 2 30000 50 0 2

[0021] Table 1 shows the rotational speed ω of the permanent magnet synchronous motor 100. m An example of the relationship between the zero-crossing point judgment value Nmax and the value is given, where S1 is the number of sampling points in a 360-degree period and S2 is the number of sampling points in a 2-degree electrical angle. Note that the permanent magnet synchronous motor 100 is a four-pole motor (i.e., P=4), and the frequency f of the pulse width modulation (PWM) of the permanent magnet synchronous motor 100 is... c It is 50 kHz. The value of S1 can be obtained by converting 120 × f c Divide by P×ω m To calculate (that is) The value of S2 can be equal to or less than 1. The maximum integer, and the zero-crossing point judgment value Nmax can be equal to the maximum value between 2 and S2. For example, at the speed ω of the permanent magnet synchronous motor 100... m When the revolutions per minute (RPM) is 1000, the value of S1 can be 1500. And the value of S2 can be equal to 8 (that is, less than 8). The maximum integer is 2, therefore, the zero crossing point judgment value Nmax can be equal to 8 (that is, the maximum value between 2 and 8).

[0022] Given the above, the process of generating the count values ​​(i.e., the first count value P_N_CC and the second count value N_P_CC) can be divided into two cases (e.g., Case 1 and Case 2). In Case 1, the sign target data SIGN_TARGET_DATA is determined to be 1 (i.e., the sign of the back EMF signal changes from positive to negative when it passes through the zero crossover point). When the sign of the data point DP with a sample value within the detection range is negative (i.e., sign(DP) = -1), the first count value P_N_CC can be generated by counting the number of consecutive data points with negative sample values. When the sign of the data point DP with a sample value within the detection range is positive (i.e., sign(DP) = 1), the first count value P_N_CC is set to 0 (when SIGN_TARGET_DATA = 1 and sign(DP) = 1, P_N_CC = 0).

[0023] In Case 2, the target data SIGN_TARGET_DATA is determined to be -1 (meaning the sign changes from negative to positive when the back EMF signal passes through the zero crossover point). When the sign of a data point DP with a sample value within the detection range is positive (i.e., sign(DP) = 1), the second count value N_P_CC can be generated by counting the number of consecutive data points with positive sample values. When the sign of a data point DP with a sample value within the detection range is negative (i.e., sign(DP) = -1), the second count value N_P_CC is set to 0 (when SIGN_TARGET_DATA = -1 and sign(DP) = -1, N_P_CC = 0).

[0024] Figure 3 This is a flowchart illustrating the process of generating a count value (specifically, a first count value P_N_CC) in Case 1 according to an embodiment of the present invention. The steps do not necessarily need to be followed exactly if the same result can be obtained. Figure 3 The process shown is executed sequentially. For example, in Case 1, the process of generating the count value can be performed by... Figure 1 The processing circuit 104 shown is used to perform and / or control this process.

[0025] In step S300, it is determined whether the target data SIGN_TARGET_DATA with positive or negative sign is equal to 1 and whether the sign of the data point DP with the sampled value within the detection range is negative (that is, sign(DP) = -1). If yes, proceed to step S302; if no, proceed to step S308.

[0026] In step S302, a first count value P_N_CC is generated by counting the number of consecutive data points with negative signs.

[0027] In step S304, it is determined whether the first count value P_N_CC is greater than or equal to the zero crossover point judgment value Nmax. If yes, proceed to step S306; otherwise, Case 1 ends.

[0028] In step S306, the first count value P_N_CC is set to the zero crossover point judgment value Nmax (that is, P_N_CC = Nmax).

[0029] In step S308, it is determined whether the target data SIGN_TARGET_DATA with positive or negative sign is equal to 1 and whether the sign of the data point DP with sampled value within the detection range is positive (i.e., sign(DP) = 1). If yes, proceed to step S310; otherwise, Case 1 ends.

[0030] In step S310, the first count value P_N_CC is set to 0 (that is, P_N_CC = 0).

[0031] Figure 4 This is a flowchart illustrating the process of generating a count value (particularly the second count value N_P_CC) in Case 2 according to an embodiment of the present invention. The steps do not necessarily need to be followed exactly if the same result can be obtained. Figure 4 The process shown is executed sequentially. For example, in Case 2, the process of generating the count value can be performed by... Figure 1 The processing circuit 104 shown is used to perform and / or control this process.

[0032] In step S400, it is determined whether the target data SIGN_TARGET_DATA with positive or negative sign is equal to -1 and whether the sign of the data point DP with sampled value within the detection range is positive (i.e., sign(DP) = 1). If yes, proceed to step S402; if no, proceed to step S408.

[0033] In step S402, a second count value N_P_CC is generated by counting the number of consecutive data points with negative signs.

[0034] In step S404, it is determined whether the second count value N_P_CC is greater than or equal to the zero crossover point judgment value Nmax. If yes, proceed to step S406; otherwise, Case 2 ends.

[0035] In step S406, the second count value N_P_CC is set to the zero crossover point judgment value Nmax (that is, P_N_CC = Nmax).

[0036] In step S408, it is determined whether the target data SIGN_TARGET_DATA with positive or negative sign is equal to -1 and whether the sign of the data point DP with sampled value within the detection range is negative (that is, sign(DP) = -1). If yes, proceed to step S410; otherwise, Case 2 ends.

[0037] In step S310, the second count value N_P_CC is set to 0 (that is, N_P_CC = 0).

[0038] To better understand, Figure 2 The region A of the back electromotive force signal shown is magnified to illustrate the determination of the zero crossover point at the last data point in a series of data points. Figure 5 According to an embodiment of the present invention Figure 2The diagram shows data points in region A of the back EMF signal. Since the back EMF signal changes sign from positive to negative at the zero-crossing point in region A, the count value is generated under Case 1, and the target data SIGN_TARGET_DATA is 1. In this embodiment, assuming the zero-crossing point judgment value Nmax is set to 3, in a first interval B (greater than 0 and less than the threshold TH), since the data sign is positive, the first count value P_N_CC is set to 0. In a second interval C (negative numbers greater than the threshold TH and less than 0), the first count value P_N_CC is generated by counting the number of consecutive data points with negative signs. Since the zero-crossing point judgment value Nmax is set to 3, a zero-crossing point is determined to occur at a data point D (the last data point in the consecutive data points when the first count value P_N_CC equals the zero-crossing point judgment value Nmax). Furthermore, data points with alternating positive and negative signs before data point D in region E are considered sampling noise.

[0039] Figure 6 This is a flowchart of a method for determining the occurrence of a zero-crossing point in the back electromotive force signal of a permanent magnet synchronous motor according to an embodiment of the present invention. If the same result can be obtained, the steps do not necessarily need to be followed exactly. Figure 6 The process shown will be executed sequentially. For example... Figure 6 The method shown can be derived from Figure 1 The sampling circuit 102 and processing circuit 104 shown are used for sampling and / or control.

[0040] In step S600, the first count value P_N_CC, the second count value N_P_CC, and the positive / negative target data SIGN_TARGER_DATA are set to 0, and the zero crossover point judgment value Nmax and the threshold TH are set to determine the occurrence of a zero crossover point in the back electromotive force signal of the permanent magnet synchronous motor 100.

[0041] In step S602, the back electromotive force signal is sampled by the sampling circuit 102 to generate multiple data points.

[0042] In step S604, for a data point DP (which is any one of the multiple data points), it is determined whether the absolute value of the sampled value of the data point DP (for simplicity, it is marked as "abs(DP)") is greater than or equal to the threshold TH. If yes, proceed to step S606; if no, proceed to step S618.

[0043] In step S606, it is determined whether the target data SIGN_TARGET_DATA is equal to 0. If yes, proceed to step S608; otherwise, proceed to step S610.

[0044] In step S608, the sign target data SIGN_TARGET_DATA is set to 1 or -1 (that is, SIGN_TARGET_DATA = sign(DP)) according to the sign of the data point DP. When the sign of the back EMF signal changes from positive to negative when it passes through the zero crossing point and the sign of the data point DP is positive (that is, sign(DP) = 1), the sign target data SIGN_TARGET_DATA is set to 1. On the other hand, when the sign of the back EMF signal changes from negative to positive when it passes through the zero crossing point and the sign of the data point DP is negative (that is, sign(DP) = -1), the sign target data SIGN_TARGET_DATA is set to -1.

[0045] In step S610, it is determined whether the second count value N_P_CC is equal to the zero crossover point judgment value Nmax. If yes, proceed to step S612; otherwise, proceed to step S614.

[0046] In step S612, the second count value N_P_CC is set to 0.

[0047] In step S614, it is determined whether the first count value P_N_CC is equal to the zero crossover point judgment value Nmax. If yes, proceed to step S616; otherwise, proceed to step S618.

[0048] In step S616, the first count value P_N_CC is set to 0.

[0049] In step S618, the following steps are performed: Figure 3 The process shown is for generating the first count value P_N_CC in Case 1.

[0050] In step S620, perform Figure 4 The process shown is for generating the second count value N_P_CC in Case 2.

[0051] In step S622, it is determined whether the first count value P_N_CC is equal to the zero crossover point judgment value Nmax and whether the positive and negative target data SIGN_TARGET_DATA is equal to 1. If yes, proceed to step S624; if no, proceed to step S626.

[0052] In step S624, it is determined that a zero-crossing point occurred at the last data point of the continuous data points, where the sign of the back electromotive force signal changes from positive to negative when it passes through the zero-crossing point (for simplicity, it is marked as "P->N zero-crossing point").

[0053] In step S626, it is determined whether the second count value N_P_CC is equal to the zero crossover point judgment value Nmax and whether the positive and negative target data SIGN_TARGET_DATA is equal to -1. If yes, proceed to step S628; otherwise, return to step S604.

[0054] In step S628, it is determined that a zero-crossing point occurred at the last data point of the continuous data points, where the sign of the back electromotive force signal changes from negative to positive when it passes through the zero-crossing point (for simplicity, it is marked as "N->P zero-crossing point").

[0055] As those skilled in the art can easily understand from the above description... Figure 6 For the sake of brevity, the operations shown in each step will not be repeated here in this embodiment.

[0056] Furthermore, to avoid and eliminate sampling noise, the determination of the occurrence of the zero crossover point can also be limited by the rotational speed according to the method of the present invention. Figure 7 This is a schematic diagram of a back electromotive force signal according to an embodiment of the present invention. Figure 7 As shown, a first zero-crossing point P1 occurs at time point t2, a second zero-crossing point P2 occurs at time point t3, a third zero-crossing point P3 occurs at time point t1, and a fourth zero-crossing point P4 occurs at time point t0. When the back EMF signal passes through the first zero-crossing point P1 and the fourth zero-crossing point P4, the sign of the back EMF signal changes from negative to positive. When the back EMF signal passes through the second zero-crossing point P2 and the third zero-crossing point P3, the sign of the back EMF signal changes from positive to negative.

[0057] In passing Figure 6 After obtaining a zero-crossing point in the back EMF signal using the method shown, two limiting speeds can be calculated based on the time difference between two adjacent zero-crossing points before this zero-crossing point. For example, for speeds passing through... Figure 6 The method shown obtains a fifth zero-crossing point P5 (where the sign of the back EMF signal changes from negative to positive when it passes through the fifth zero-crossing point P5). Since the rotational speed of the back EMF signal can be calculated from the time difference between any two zero-crossing points, a first limiting rotational speed ω is thus determined. e1 And a second limiting speed ω e2 The following formula can be calculated using processing circuit 104:

[0058]

[0059]

[0060] The first limiting speed ωe1 The first limiting speed ω is calculated by dividing π by the time difference between time point t2 corresponding to the first zero crossing point P1 and time point t1 corresponding to the third zero crossing point P3. e1 (Calculated by half the time period at the first zero-crossing point P1), and the second limiting speed ω e2 The second limiting speed ω is calculated by dividing 2π by the time difference between time point t2 corresponding to the first zero crossing point P1 and time point t0 corresponding to the fourth zero crossing point P4. e2 (Calculated by the full time period at the first zero crossing point P1).

[0061] Similarly, for those who pass Figure 6 The method shown obtains a sixth zero-crossing point P6 (where the sign of the back EMF signal changes from positive to negative when it passes through the sixth zero-crossing point P6), and a third limiting speed ω. e3 And a fourth limiting speed ω e4 The following formula can be calculated using processing circuit 104:

[0062]

[0063]

[0064] The third limiting speed ω e3 The third limiting speed ω is calculated by dividing π by the time difference between time point t3, which corresponds to the second zero crossing point P2, and time point t2, which corresponds to the first zero crossing point P1. e3 (Calculated by half the time period at the second zero-crossing point P2), and the fourth limiting speed ω e4 The fourth limiting speed ω is calculated by dividing 2π by the time difference between time point t3 corresponding to the second zero crossing point P2 and time point t1 corresponding to the third zero crossing point P3. e4 (Calculated over the entire time period at the second zero-crossing point P2).

[0065] In this embodiment, the processing circuit 104 can set a first speed constant Check1PILimit and a second speed constant Check2PILimit based on the rotor inertia. The first speed constant Check1PILimit may be different from the second speed constant Check2PILimit. For a light rotor inertia, the values ​​of both Check1PILimit and Check2PILimit can be set between 0.3 and 0.5, while for a heavy rotor inertia, the values ​​of both Check1PILimit and Check2PILimit can be set between 0.5 and 0.7. Furthermore, the process of determining the zero-crossing point based on the rotational speed can be divided into two cases (e.g., Case A and Case B).

[0066] In Case A, Figure 6 The method shown determines whether the back electromotive force signal passes through a zero crossing point (e.g., Figure 7 The sign of the fifth zero-crossing point P5 changes from negative to positive. For limiting the fifth zero-crossing point P5 by rotational speed, the two rotational speed limit settings (e.g., a first rotational speed limit setting FRS and a second rotational speed limit setting SRS) can be determined based on the first limiting rotational speed ω. e1 Second limiting speed ω e2 The first speed limit setting (FRS) is calculated by using the first speed constant Check1PILimit and the second speed constant Check2PILimit. The first speed limit setting (FRS) can be achieved by combining the first speed constant Check1PILimit with the first speed limit ω. e1 Calculated by multiplication (i.e., FRS = Check1PILimit × ω) e1 The second speed limit setting SRS can be achieved by setting the second speed constant Check2PILimit and the second speed limit ω. e2 Calculate by multiplication (i.e., SRS = Check2PILimit × ω) e2 ).

[0067] To determine whether the fifth zero-crossing point P5 is a valid zero-crossing point, the first rotational speed ω is calculated based on half the time period of the fifth zero-crossing point P5. eh The second speed ω is compared with the first speed limit setting FRS and calculated over the entire time period at the fifth zero crossing point P5. ef Compare with the second speed limit setting SRS. In response to the first speed ω eh Greater than or equal to the first speed limit setting FRS and the second speed ω efGreater than or equal to the second speed limit setting SRS (i.e., ω) eh ≥Check1PILimit×ω e1 And ω ef ≥Check2PILimit×ω e2 If the fifth zero-crossing point P5 is determined to be a valid zero-crossing point, then in response to the first rotational speed ω, the zero-crossing point P5 can be considered a valid zero-crossing point. eh Setting FRS or second speed ω below the first speed limit ef Less than the second speed limit setting SRS (that is, ω) eh <Check1PILimit×ω e1 or ω ef <Check2PILimit×ω e2 If the fifth zero-crossing point P5 does not meet the conditions for a valid zero-crossing point, it can be considered as sampling noise.

[0068] In Case B, Figure 6 The method shown determines whether the back electromotive force signal passes through a zero crossing point (e.g., Figure 7 The sign of the sixth zero-crossing point P6 changes from positive to negative. For limiting the sixth zero-crossing point P6 by rotational speed, the two rotational speed limit settings (e.g., a third rotational speed limit setting TRS and a fourth rotational speed limit setting QRS) can be determined based on the third limiting rotational speed ω. e3 Fourth limiting speed ω e4 The first speed constant Check1PILimit and the second speed constant Check2PILimit are used for calculation, and the third speed limit setting TRS can be calculated by combining the first speed constant Check1PILimit with the third speed limit ω. e3 Calculated by multiplication (i.e., TRS = Check1PILimit × ω) e3 The fourth speed limit setting QRS can be achieved by setting the second speed constant Check2PILimit and the fourth speed limit ω. e4 Calculate by multiplication (i.e., QRS = Check2PILimit × ω) e4 ).

[0069] To determine whether the sixth zero-crossing point P6 is a valid zero-crossing point, the first rotational speed ω is calculated using the half-time period of the sixth zero-crossing point P6. eh Comparison with the third speed limit setting TRS, and a second speed ω calculated over the entire time period at the sixth zero crossing point P6. ef Compare with the fourth speed limit setting QRS. In response to the first speed ω eh The third speed limit setting TRS is greater than or equal to the second speed ω. efGreater than or equal to the fourth speed limit setting QRS (i.e., ω) eh ≥Check1PILimit×ω e3 And ω ef ≥Check2PILimit×ω e4 If the sixth zero-crossing point P6 is determined to be a valid zero-crossing point, then in response to the first rotational speed ω, the zero-crossing point P6 can be considered a valid zero-crossing point. eh Less than the third speed limit setting TRS or the second speed ω ef The QRS (i.e., ω) setting is less than the fourth speed limit. eh <Check1PILimit×ω e3 or ω ef <Check2PILimit×ω e4 If the sixth zero-crossing point P6 does not meet the conditions for a valid zero-crossing point, it can be considered as sampling noise.

[0070] In generating pass Figure 6 The method shown yields the rotational speed at the zero crossover point (i.e., the first rotational speed ω). eh and the second rotational speed ω ef After comparing the speed limit settings calculated in Case A and Case B, if the zero crossover point is determined to be sampling noise based on the comparison result, the processing circuit 104 can also be used to eliminate the sampling noise. In addition, as long as the zero crossover point judgment value Nmax is not large, the phase lag between the back EMF signal obtained by the method of the present invention and the original back EMF signal will not be too obvious. Therefore, the method of the present invention can determine the occurrence of a zero crossover point in the back EMF signal of the permanent magnet synchronous motor 100 under conditions of high immunity and low delay.

[0071] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention should be included within the scope of the present invention.

[0072] [Symbol Explanation]

[0073] 10: Motor assembly

[0074] 100: Permanent magnet synchronous motor

[0075] 102: Sampling Circuit

[0076] 104: Processing Circuit

[0077] 106: Stator

[0078] 108: Rotor

[0079] SIGN_TARGET_DATA: Sign / Subject target data

[0080] TH: Threshold

[0081] B, C: Interval

[0082] D: Data points

[0083] S300~S310, S400~S410, S600~S628: Steps

[0084] t0~t4: Time points

[0085] P1~P6: Zero Crossing Point

Claims

1. A method for determining the occurrence of a zero-crossing point in an AC signal of a fixed frequency for a permanent magnet synchronous motor, comprising: The AC signal is sampled to obtain multiple data points; Within a detection range, the number of consecutive data points with the same sign is counted to generate a count value, wherein the multiple data points contain the multiple consecutive data points; determining whether the count value is substantially equal to a zero crossing determination value; as well as In response to the count value being substantially equal to the zero-crossing point judgment value, it is determined that a zero-crossing point occurred at the last data point among the plurality of consecutive data points. in, When the sign of the AC signal changes from positive to negative at the zero-crossing point, the count value is generated by counting the number of consecutive data points with negative sample values; When the sign of the AC signal changes from negative to positive at the zero-crossing point, the count value is generated by counting the number of consecutive data points with positive sample values.

2. The method of claim 1, further comprising: For a data point, which is any one of the plurality of data points, determining whether a sample value of the data point is not within the detection range; as well as In response to the fact that the sampled value of the data point is not within the detection range, a target data with a positive or negative sign is set based on the sign of the data point. The sign of each of the multiple consecutive data points is different from the sign of the target data.

3. The method of claim 2, wherein the step of determining whether the sampled value of the data point is outside the detection range includes: The absolute value of the sampled value of the data point is compared with a threshold; and If the absolute value is not less than the threshold, it is determined that the sampled value of the data point is not within the detection range.

4. The method of claim 2, wherein the detection range has an upper limit, which is a positive value, and a lower limit, which is a negative value, the sampled value of the data point is not less than the upper limit of the detection range, and the count value is generated by counting the number of the plurality of consecutive data points with negative signs.

5. The method of claim 2, wherein the detection range has an upper limit, which is a positive value, and a lower limit, which is a negative value, the sampled value of the data point is not greater than the lower limit of the detection range, and the count value is generated by counting the number of consecutive data points with positive signs.

6. The method of claim 1, wherein the step of determining that the zero-crossing point occurs at the last data point among the plurality of consecutive data points comprises: A first limiting speed and a second limiting speed are calculated based on the two adjacent zero crossing points before the zero crossing point. A threshold setting is calculated based on the first speed limit and the second speed limit; A first rotational speed calculated by half a time period and a second rotational speed calculated by full time period for the last data point of the plurality of consecutive data points are compared with the threshold setting to generate a comparison result; as well as The comparison result is used to determine whether the zero-crossing point occurs at the last data point among multiple consecutive data points.

7. The method of claim 6, wherein the first limiting speed is calculated based on a time difference between the two adjacent zero-crossing points, wherein one of the two adjacent zero-crossing points corresponds to the sign of the AC signal changing from negative to positive, and the other of the two adjacent zero-crossing points corresponds to the sign of the AC signal changing from positive to negative.

8. The method of claim 6, wherein the sign of the AC signal changes from positive to negative when it passes through the zero-crossing point; the second limiting speed is calculated based on a time difference between the two adjacent zero-crossing points, wherein each of the two adjacent zero-crossing points corresponds to the sign of the AC signal changing from positive to negative.

9. The method of claim 6, wherein the sign of the AC signal changes from negative to positive when it passes through the zero-crossing point; the second limiting speed is calculated based on a time difference between the two adjacent zero-crossing points, wherein each of the two adjacent zero-crossing points corresponds to the sign of the AC signal changing from negative to positive.

10. The method of claim 6, wherein the threshold setting includes a first speed limit setting and a second speed limit setting, the first speed limit setting being calculated by multiplying a first speed constant by the first speed limit, and the second speed limit setting being calculated by multiplying a second speed constant by the second speed limit.

11. The method of claim 10, wherein in response to the first rotational speed being greater than or substantially equal to the first rotational speed limit setting and the second rotational speed being greater than or substantially equal to the second rotational speed limit setting, it is determined that the zero crossover point occurs at the last data point of the plurality of consecutive data points.

12. An electric motor device comprising: A permanent magnet synchronous motor; a sampling circuit coupled to the permanent magnet synchronous motor and configured to sample an alternating current signal having a fixed frequency of the permanent magnet synchronous motor to obtain a plurality of data points; as well as A processing circuit, coupled to the sampling circuit, is used for: Within a detection range, the number of consecutive data points with the same sign is counted to generate a count value, wherein the multiple data points contain the multiple consecutive data points; Determine whether the count value is substantially equal to a zero-crossing point judgment value; as well as In response to the count value being substantially equal to the zero-crossing point judgment value, it is determined that a zero-crossing point occurred at the last data point among the plurality of consecutive data points. Wherein, when the sign of the AC signal changes from positive to negative at the zero crossover point, the count value is generated by counting the number of consecutive data points with negative sample values; When the sign of the AC signal changes from negative to positive at the zero-crossing point, the count value is generated by counting the number of consecutive data points with positive sample values.

Images