A Method for Online Dynamic Calibration of Temperature Drift of Current Sensors

Abstract

The present application provides a method for on-line dynamic correction of temperature drift of a current sensor, belonging to the technical field of motor control, specifically including: reading the A0 sampling result register to obtain the A-phase current sampling value; reading the A1 sampling result register to obtain the B-phase current sampling value; reading the electrical angle θ value; calculating K according to the A-phase current sampling value, B-phase current sampling value and electrical angle θ A , K B , K Value , and calculating the A-phase zero current sampling value; calculating K according to the A-phase current sampling value, B-phase current sampling value and electrical angle θ A , K B , K Value , and calculating the B-phase zero current sampling value; determining whether the calculated zero current sampling value is within the threshold range, and if satisfied, updating the A-phase zero current sampling value before correction and the B-phase zero current sampling value before correction; otherwise, not updating the A-phase zero current sampling value and the B-phase zero current sampling value. Through the processing solution of the present application, the sampling of the phase current value is ensured to be accurate, enabling the scanner to operate smoothly.

Description

Technical Field

[0001] The present application relates to the field of motor control, and particularly to a method for online dynamic correction of temperature drift of a current sensor. Background Art

[0002] Permanent magnet synchronous motors are applied to the servo drive system of airborne radar scanners due to their high efficiency, high power density, and excellent speed regulation performance. The current loop, as the innermost loop of vector control, plays a decisive role in the control performance of the scanner, and the accurate detection of three-phase currents is the prerequisite for improving the control performance of the current loop.

[0003] After the airborne radar scanner is powered on, power-down restart is not allowed. When it operates continuously, the ambient temperature changes greatly, and the inherent characteristic of the temperature drift of the current sensor causes the zero-current sampling value to change. The existing control algorithms only correct the zero-current sampling value of the current sensor during power-on. Affected by temperature drift, the phase current is distorted, the control performance of the current loop is reduced, and the scanner runs abnormally. Summary of the Invention

[0004] In view of this, the present application provides a method for online dynamic correction of temperature drift of a current sensor, which solves the problems in the prior art, ensures accurate sampling of the phase current value, and enables the scanner to operate smoothly.

[0005] The method for online dynamic correction of temperature drift of a current sensor provided by the present application adopts the following technical solutions:

[0006] A method for online dynamic correction of temperature drift of a current sensor includes:

[0007] Step 1: Read the A0 sampling result register to obtain the sampled value I of the A-phase current ADCA ;

[0008] Step 2: Read the A1 sampling result register to obtain the sampled value I of the B-phase current ADCB ;

[0009] Step 3: Read the value of the electrical angle θ;

[0010] Step 4: Calculate K A , K B , K Value according to the sampled value of the A-phase current, the sampled value of the B-phase current, and the electrical angle θ, and calculate the zero-current sampled value I ZeroOffsetA of the A-phase. The calculation formula is:

[0011]

[0012] Step 5: Calculate K A , K B , K Value, calculate the sampled value I of the zero current of phase B ZeroOffsetB , and the calculation formula is:

[0013]

[0014] Step 6: Determine whether the calculated zero current sampled value is within the threshold range. If it is satisfied, jump to Step 7; otherwise, jump to Step 8.

[0015] Step 7: Update the sampled value I of the zero current of phase A before calibration ZeroOffsetAOld and the sampled value I of the zero current of phase B before calibration ZeroOffsetBOld ;

[0016] Step 8: Do not update the sampled value I of the zero current of phase A ZeroOffsetAOld and the sampled value I of the zero current of phase B ZeroOffsetBOld .

[0017] Optionally, if the electrical angle is within 359.5° to 0.5°, calculate the sampled value I of the zero current of phase A ZeroOffsetA ; if the electrical angle is within 119.5° to 120.5°, calculate the sampled value I of the zero current of phase B ZeroOffsetB .

[0018] Optionally, after the current value sampled by the current sensor is normalized, it corresponds to 0 to 1, and the threshold range of the zero current sampled value is 0.4 - 0.6.

[0019] Optionally,

[0020] Optionally, K B = 2 * sinθ.

[0021] Optionally,

[0022] In summary, the present application includes the following beneficial technical effects:

[0023] The calibration of the present application does not require adding a new temperature sensor, reduces the hardware circuit and the layout area of the circuit board, and reduces the cost.

[0024] The present application dynamically calibrates the zero current sampled value in real time within the range of environmental temperature from -55°C to 70°C, ensures accurate sampling of the phase current value, enables the motor to operate smoothly, and improves the environmental adaptability of the radar scanner. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 is the servo drive control block diagram;

[0027] Figure 2 is the current sampling block diagram;

[0028] Figure 3 is the online dynamic correction flowchart of the temperature drift of the current sensor;

[0029] Figure 4 is the experimental diagram of the feedback angle at room temperature of 25°C;

[0030] Figure 5 is the experimental diagram of the phase A current at room temperature of 25°C;

[0031] Figure 6 is the experimental diagram of the feedback angle before and after correction;

[0032] Figure 7 is the experimental diagram of the phase A current before and after correction. Specific implementation manners

[0033] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0034] The following uses specific specific examples to illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0035] It should be noted that the following describes various aspects of the embodiments within the scope of the appended claims. It should be obvious that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is illustrative only. Based on the present application, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, this device can be implemented and this method can be practiced using other structures and / or functions in addition to one or more of the aspects described herein.

[0036] It should also be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner. The diagrams only show the components related to the present application, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0037] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0038] An embodiment of the present application provides a method for online dynamic correction of the temperature drift of a current sensor.

[0039] Aiming at the problems and deficiencies in the existing technology, a method for online dynamic correction of the temperature drift of a current sensor is proposed. The zero-current sampling value is dynamically corrected in real time within the ambient temperature range of -55°C to 70°C to ensure accurate sampling of the phase current value, enabling the motor to operate smoothly, improving the environmental adaptability of the radar scanner, and without increasing costs.

[0040] A method for online dynamic correction of the temperature drift of a current sensor includes:

[0041] Step 1: Read the A0 sampling result register to obtain the A-phase current sampling value I ADCA .

[0042] Step 2: Read the A1 sampling result register to obtain the B-phase current sampling value I ADCB .

[0043] Step 3: Read the electrical angle θ value.

[0044] Step 4: Calculate K A , K B , K Value according to the A-phase current sampling value, the B-phase current sampling value, and the electrical angle θ, and calculate the A-phase zero-current sampling value I ZeroOffsetA . The calculation formula is:

[0045]

[0046] Step 5: Calculate K A , K B , K Value according to the A-phase current sampling value, the B-phase current sampling value, and the electrical angle θ, and calculate the B-phase zero-current sampling value I ZerooffsetB . The calculation formula is:

[0047]

[0048] Step 6: Determine whether the calculated zero - current sampling value is within the threshold range. If it is satisfied, jump to Step 7; otherwise, jump to Step 8.

[0049] Step 7: Update the zero - current sampling value I of phase A before calibration ZeroOffsetAOld and the zero - current sampling value I of phase B before calibration ZeroOffsetBOld .

[0050] Step 8: Do not update the zero - current sampling value I of phase A ZeroOffsetAOld and the zero - current sampling value I of phase B ZeroOffsetBOld .

[0051] If the electrical angle is within 359.5° to 0.5°, calculate the zero - current sampling value I of phase A ZeroOffsetA ; if the electrical angle is within 119.5° to 120.5°, calculate the zero - current sampling value I of phase B ZeroOffsetB .

[0052] After the current value sampled by the current sensor is normalized, it corresponds to 0 - 1, and the threshold range of the zero - current sampling value is 0.4 - 0.6.

[0053] In the above,

[0054] K B = 2 * sinθ

[0055]

[0056] In one embodiment, the servo system uses a permanent - magnet synchronous motor, whose three - phase windings are star - connected, and the drive algorithm uses field - oriented control (FOC). The control block diagram of the position - speed - current three - loop is as Figure 1 shown.

[0057] The electrical angle value of the motor is detected by a resolver, and the current - loop feedback value is obtained by sampling the currents of phases A and B and through Clarke and Park transformations; after PID control, the duty cycle is obtained through IPark transformation and space - vector modulation SVPWM, and the on - off time of the three - phase full - bridge tubes of the IPM module is adjusted to control the operation of the motor.

[0058] As Figure 2 shown is the current - sampling block diagram. The currents of phases A and B are processed by a current sensor, a conditioning circuit, and a conversion circuit and then sent to the analog - to - digital conversion (ADC) unit integrated in the DSP. The analog range of the phase - current after conditioning is 0V - 3V, and the zero - current corresponds to the reference voltage of 1.5V. Due to the change in ambient temperature, the reference voltage of the zero - current will change, resulting in the change of the zero - current sampling value. Therefore, this patent proposes a method for online dynamic calibration of the temperature drift of the current sensor to calibrate the zero - current sampling value in real time.

[0059] The current expressions of phase A and phase B are shown in formula (1), where I ADCA is the sampled value of the current of phase A, and I ZeroOffsetA is the sampled value of the zero current of phase A; I ADCB is the sampled value of the current of phase B, and I ZeroOffsetB is the sampled value of the zero current of phase B;

[0060]

[0061] As shown in formula (2), it is the CLARKE transformation to obtain the phase current in the αβ-axis rotating coordinate system.

[0062]

[0063] As shown in formula (3), it is the PARK transformation to obtain the phase current in the dq-axis rotating coordinate system, where θ is the electrical angle of the motor.

[0064]

[0065] Due to the closed-loop control of the FOC current loop, the given value of the i d instruction is 0, so the feedback value of the i d is theoretically also 0; that is, i Alpha *cosθ + i Beta *sinθ = 0. Then it can be deduced that

[0066] I ZeroOffssetA *K A + I ZeroOffsetB *K B = K Value (4)

[0067] Among them:

[0068]

[0069] K B = 2*sinθ

[0070]

[0071] Therefore, the formulas for the sampled values of the zero currents of phases A and B can be obtained as shown in (5) and (6). Among them, I zeroOffsetAOId is the sampled value of the zero current of phase A before calibration; I ZeroOffsetB is the sampled value of the zero current of phase B before calibration.

[0072]

[0073]

[0074] The flowchart of the on-line calibration of the temperature drift of the current sensor is as shown in Figure 3As shown, first read the A0 sampling result register to obtain the sampled value I of the A-phase current ADCA , read the A1 sampling result register to obtain the sampled value I of the B-phase current ADCB , read the value of the electrical angle θ, and when it is determined that the electrical angle is within 0° to 0.5 degrees, calculate the zero-current sampled value I of the A-phase using formula (5) ZeroOffsetA ; when it is determined that the electrical angle is within 119.5° to 120.5 degrees, calculate the zero-current sampled value I of the B-phase using formula (6) ZeroOffsetB ; determine whether the calculated sampled value is within a reasonable range. If so, update the zero-current sampled value I of the A-phase before calibration ZeroOffsetAOld and the zero-current sampled value I of the B-phase before calibration ZeroOffsetBOld .

[0075] In one embodiment, for the above analysis and proposed calibration method, a physical platform is built. The control chip uses the TMS320F28335 of TI Corporation, with a main interrupt of 10 kHz, and magnetic field-oriented FOC control is adopted.

[0076] The current sensor uses the ACS712 Hall-type current sensor of Allegro Corporation, and the ADC uses a 12-bit resolution (the digital quantity corresponds to 0 to 4096, the analog quantity corresponds to 0 V to 3 V, and after per-unit conversion, it corresponds to 0 to 1).

[0077] When powered on at room temperature of 25°C, the zero-current sampled value of the A-phase is 0.4842; the zero-current sampled value of the B-phase is 0.4691; the experimental diagram of the feedback angle is as Figure 4 shown, and the operation is stable. The experimental diagram of the A-phase current is as Figure 5 shown, which is a standard sine wave.

[0078] Put the scanner into the incubator, set the temperature to rise from -55°C to 70°C. Before the dynamic calibration method is adopted, the experimental curve of the feedback angle is as Figure 6 shown in the first 23 s, and the scanner runs with jitter; the experimental curve of the A-phase current is as Figure 7 shown in the first 350 ms, and the A-phase current is distorted. After the dynamic calibration method is adopted, the experimental curve of the feedback angle is as Figure 6 shown in the last 23 s, and the scanner runs smoothly again; the experimental curve of the A-phase current is as Figure 7 shown in the last 350 ms, and the A-phase current returns to the sine wave. The experimental results show that the dynamic calibration method proposed in this patent can effectively solve the problem of temperature drift of the current sensor.

[0079] By observing the relationship between temperature and zero-current sampled value through software, as shown in Table 1. The zero-current sampled values of the A and B phases change with temperature.

[0080] Table 1 Relationship between temperature and zero-current sampled value

[0081] Temperature Sampling value of zero current of phase A Sampling value of zero current of phase B 70℃ 0.4972 0.4791 60℃ 0.4935 0.4765 50℃ 0.4912 0.4735 40℃ 0.4879 0.4712 30℃ 0.4855 0.4699 20℃ 0.4838 0.4686 10℃ 0.4805 0.4643 0℃ 0.479 0.46 -10℃ 0.4759 0.4587 -20℃ 0.4743 0.4532 -30℃ 0.4725 0.4502 -40℃ 0.4703 0.4489 -50℃ 0.4685 0.442 -55℃ 0.464 0.438

[0082] As described above, it is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for online dynamic calibration of the temperature drift of a current sensor, characterized in that, Including: Step 1: Read the A0 sampling result register to obtain the A-phase current sampling value ; Step 2: Read the A1 sampling result register to obtain the B-phase current sampling value ; Step 3: Read the electrical angle value; Step 4: Based on the sampled value of phase A current, the sampled value of phase B current, and the electrical angle calculate , , , , and calculate the sampled value of phase A zero current , and the calculation formula is: ; Step Five: Calculate, based on the sampled value of phase A current, the sampled value of phase B current, and the electrical angle to calculate , and calculate the sampled value of phase B zero current . The calculation formula is as follows: ; Step 6: Determine whether the calculated zero-current sampling value is within the threshold range. If it is satisfied, jump to Step 7; otherwise, jump to Step 8. Step 7: Update the sampled value of phase A zero current before calibration and the sampled value of phase B zero current before calibration ; Step 8: Do not update the zero-current sampling value of phase A and the zero-current sampling value of phase B .

2. The method for online dynamic calibration of the temperature drift of the current sensor according to claim 1, characterized in that, If the electrical angle is within 359.5° to 0.5°, calculate the sampled value of the zero current of phase A ; If the electrical angle is within 119.5° to 120.5°, calculate the sampled value of the zero current of phase B .

3. The method for online dynamic calibration of the temperature drift of the current sensor according to claim 1, characterized in that, The per-unit value of the current value after sampling by the current sensor corresponds to 0 to 1, and the threshold range of the zero-current sampling value is 0.4 - 0.6.

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