Magnetic bearing control system and its current compensation method, device, and storage medium

Abstract

This invention discloses a current compensation method, device, control system, storage medium, and computer program product for a magnetic bearing control system. The magnetic bearing control system includes a sampling resistor for sampling the coil current. The method includes: when the system is stopped, applying a closed-loop current to the coil; determining the current compensation curve and compensation coefficient of the current sensor based on the closed-loop current, the voltage across the sampling resistor, and the current value of the current sensor; after the system starts, determining whether current compensation is needed based on the compensation coefficient; if current compensation is needed, compensating the current of the current sensor or compensating the output voltage of the current sensor based on the current compensation curve. This scheme ensures that the current sensor maintains high accuracy by calibrating the current sensor when the system is stopped and compensating the current sensor's detection results based on the calibrated current compensation curve during system operation.

Description

Technical Field

[0001] This invention belongs to the field of magnetic levitation control technology, specifically relating to a current compensation method, device, magnetic bearing control system, storage medium, and computer program product for a magnetic bearing control system. Background Technology

[0002] Magnetic levitation centrifuges utilize magnetic force to suspend the rotor in mid-air, eliminating mechanical contact between the rotor and stator. Advantages include low mechanical wear, low energy consumption, low noise, long lifespan, no need for lubrication, and no oil pollution. The magnetic bearing control system employs a dual closed-loop control: an outer displacement loop and an inner current loop. Controlling the magnetic bearing current is crucial for controlling magnetic levitation; a stable and reliable current loop requires precise current sampling feedback.

[0003] Hall current sensors are widely used in magnetic bearing current loops due to their advantages such as high accuracy and linearity, fast response speed, strong anti-interference ability, and ease of integration. However, mechanical vibration during centrifuge operation, humid operating environments, and lax painting processes during production can significantly reduce the lifespan of Hall current sensors, leading to a decline in detection accuracy and performance.

[0004] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The purpose of this invention is to provide a current compensation method, device, control system, storage medium, and computer program product for a magnetic bearing control system. This addresses the problem of decreased detection accuracy and performance of Hall current sensors in related solutions. By calibrating the current sensor during system shutdown to determine the current compensation curve, and then compensating the current sensor's detection results based on the current compensation curve during system operation, the invention ensures that the current sensor maintains high detection accuracy and improves the stability of the magnetic bearing control system.

[0006] This invention provides a current compensation method for a magnetic bearing control system. The magnetic bearing control system includes a current sensor, a coil, and a sampling resistor. The current sensor is used to detect the current in the coil. The sampling resistor is used to sample the current in the coil. The method includes: when the magnetic bearing control system is in a stopped state, applying a closed-loop current to the coil and acquiring the voltage value across the sampling resistor and the current value of the current sensor; determining a current compensation curve and a compensation coefficient for the current sensor based on the closed-loop current, the voltage value across the sampling resistor, and the current value of the current sensor; after the magnetic bearing control system is started, determining whether current compensation is needed based on the compensation coefficient; if current compensation is needed, compensating the current of the current sensor according to the current compensation curve; or, compensating the output voltage of the current sensor according to the current compensation curve to compensate the current of the current sensor.

[0007] In some implementations, determining the current compensation curve and compensation coefficient of the current sensor based on the closed-loop current, the voltage across the sampling resistor, and the current value of the current sensor includes: converting the voltage across the sampling resistor into a current value; establishing a current calibration curve based on the closed-loop current and the converted current value; establishing an actual current curve based on the closed-loop current and the current value of the current sensor; determining the current compensation curve based on the current standard curve and the actual current curve; and determining the slope of the current compensation curve as the compensation coefficient.

[0008] In some implementations, the closed-loop current applied to the coil is at least two currents of different magnitudes, and both closed-loop currents are greater than a preset first current value and less than a preset second current value.

[0009] In some implementations, determining whether current compensation is needed based on the compensation coefficient includes: judging the relationship between the compensation coefficient and a set threshold; if the compensation coefficient is greater than the set threshold, then determining that current compensation is needed; if the compensation coefficient is less than or equal to the set threshold, then determining that current compensation is not needed.

[0010] In some embodiments, compensating the current of the current sensor according to the current compensation curve includes: obtaining the target current of the coil; obtaining the corresponding compensation current from the current compensation curve based on the target current; and adding the compensation current to the current of the current sensor to compensate the current of the current sensor.

[0011] In some embodiments, the output voltage of the current sensor is compensated according to the current compensation curve to compensate the current of the current sensor, including: obtaining the target current of the coil; converting the current compensation curve into a voltage compensation curve based on a preset relationship between the voltage and current of the current sensor; obtaining the corresponding compensation voltage from the voltage compensation curve based on the target current; adding the compensation voltage to the output voltage of the current sensor to obtain the compensated output voltage of the current sensor; and converting the compensated output voltage of the current sensor into a current based on a preset relationship between the voltage and current of the current sensor to obtain the compensated current of the current sensor.

[0012] In conjunction with the above method, another aspect of the present invention provides a current compensation device for a magnetic bearing control system. The magnetic bearing control system includes a current sensor, a coil, and a sampling resistor. The current sensor is used to detect the current of the coil. The sampling resistor is used to sample the current of the coil. The device includes: an acquisition unit configured to apply a closed-loop current to the coil and acquire the voltage value across the sampling resistor and the current value of the current sensor when the magnetic bearing control system is in a stopped state; a control unit configured to determine a current compensation curve and a compensation coefficient of the current sensor based on the closed-loop current, the voltage value across the sampling resistor, and the current value of the current sensor; the control unit is further configured to determine whether current compensation is needed based on the compensation coefficient after the magnetic bearing control system is started; the control unit is further configured to compensate the current of the current sensor according to the current compensation curve if it is determined that current compensation is needed; or, to compensate the output voltage of the current sensor according to the current compensation curve, so that the current of the current sensor is compensated.

[0013] In some embodiments, the control unit determines the current compensation curve and compensation coefficient of the current sensor based on the closed-loop current, the voltage value across the sampling resistor, and the current value of the current sensor, including: converting the voltage value across the sampling resistor into a current value; establishing a current calibration curve based on the closed-loop current and the converted current value; establishing an actual current curve based on the closed-loop current and the current value of the current sensor; determining the current compensation curve based on the current standard curve and the actual current curve; and determining the slope of the current compensation curve as the compensation coefficient.

[0014] In some implementations, the closed-loop current applied to the coil is at least two currents of different magnitudes, and both closed-loop currents are greater than a preset first current value and less than a preset second current value.

[0015] In some implementations, the control unit determines whether current compensation is needed based on the compensation coefficient, including: determining the relationship between the compensation coefficient and a set threshold; if the compensation coefficient is greater than the set threshold, then determining that current compensation is needed; if the compensation coefficient is less than or equal to the set threshold, then determining that current compensation is not needed.

[0016] In some embodiments, the control unit compensates the current of the current sensor according to the current compensation curve, including: obtaining the target current of the coil; obtaining the corresponding compensation current from the current compensation curve based on the target current; and adding the compensation current to the current of the current sensor to compensate the current of the current sensor.

[0017] In some embodiments, the control unit compensates the output voltage of the current sensor according to the current compensation curve to compensate the current of the current sensor, including: obtaining the target current of the coil; converting the current compensation curve into a voltage compensation curve based on a preset relationship between the voltage and current of the current sensor; obtaining the corresponding compensation voltage from the voltage compensation curve based on the target current; adding the compensation voltage to the output voltage of the current sensor to obtain the compensated output voltage of the current sensor; and converting the compensated output voltage of the current sensor into a current based on a preset relationship between the voltage and current of the current sensor to obtain the compensated current of the current sensor.

[0018] In conjunction with the above-described device, the present invention further provides a magnetic bearing control system, comprising: the current compensation device of the magnetic bearing control system described above.

[0019] In conjunction with the above method, the present invention further provides a storage medium comprising a stored program, wherein, when the program is executed, the device on which the storage medium is located executes the current compensation method of the magnetic bearing control system described above.

[0020] In conjunction with the above method, the present invention further provides a computer program product comprising a computer program that, when processed and executed, implements the steps of the current compensation method for the magnetic bearing control system described above.

[0021] The present invention includes a sampling resistor in the magnetic bearing control system for sampling the coil current. When the system is stopped, a closed-loop current is applied to the coil. Based on the closed-loop current, the voltage across the sampling resistor, and the current value of the current sensor, a current compensation curve and a compensation coefficient for the current sensor are determined. After the system starts, the compensation coefficient is used to determine whether current compensation is needed. If current compensation is needed, the current of the current sensor is compensated according to the current compensation curve, or the output voltage of the current sensor is compensated according to the current compensation curve. Thus, by calibrating the current sensor to determine the current compensation curve when the system is stopped, and compensating the current sensor's detection results according to the current compensation curve during system operation, the current sensor maintains high detection accuracy at all times, improving the stability of the magnetic bearing control system.

[0022] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 This is a schematic flowchart of an embodiment of the current compensation method for the magnetic bearing control system of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of a current compensation device for a magnetic bearing control system according to an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the magnetic bearing control system.

[0027] Figure 4 This is a schematic diagram illustrating the principle of current loop control.

[0028] Figure 5 A schematic diagram of the current sampling circuit for a magnetic bearing without added current compensation;

[0029] Figure 6 A schematic diagram of the magnetic bearing current sampling circuit with added current compensation;

[0030] Figure 7 A schematic diagram of the circuit structure with added voltage compensation;

[0031] Figure 8 The current compensation curve after adding current compensation;

[0032] Figure 9 The voltage compensation curve after voltage compensation has been added;

[0033] Figure 10 A schematic diagram of the calibration process for a current sensor;

[0034] Figure 11 This is a schematic diagram of the process for compensating a current sensor.

[0035] Referring to the accompanying drawings, the reference numerals in the embodiments of the present invention are as follows:

[0036] 1-Hall current sensor; 2-Sampling resistor; 3-Conditioning circuit; 102-Acquisition unit; 104-Control unit. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0038] According to an embodiment of the present invention, a current compensation method for a magnetic bearing control system is provided. The magnetic bearing control system includes a current sensor, a coil, and a sampling resistor. The current sensor is used to detect the current of the coil, and the sampling resistor is used to sample the current of the coil.

[0039] The control principle of the magnetic bearing control system is as follows: Figure 3 and Figure 4 As shown, the controller calculates the target current through the position feedback value, and controls the switching transistors in the power amplifier by sending PWM waves with different duty cycles, thereby controlling the coil current.

[0040] like Figure 5 As shown, Hall current sensor 1 is used to acquire coil current in real time. The acquired current is fed back to the MCU controller after passing through a sampling and conditioning circuit. The MCU controls the coil current based on the acquired current and a reference current, thereby achieving closed-loop current control. Due to the lack of rigor in the manufacturing process of the current sensor and the influence of the working environment, the detection accuracy of the current sensor may decrease, leading to inaccurate coil current control and affecting the normal operation of equipment such as magnetic levitation compressors.

[0041] Therefore, this solution uses a sampling resistor in the magnetic bearing control system to calibrate the accuracy of the current sensor. Based on the calibration results, the current sensor is compensated, thereby improving its accuracy. The specific circuit for current calibration is as follows: Figure 6As shown, the power amplifier provides current to the coils in the magnetic bearing. Each coil's circuit is equipped with a Hall current sensor 1 for detecting the coil current. A sampling resistor 2 is installed at the switching transistor of the power amplifier corresponding to each coil. The current flowing through the sampling resistor 2 and the current flowing through the current coil are the same. A multi-channel decoder is used to modify the circuit, connecting the Hall current sensor 1 or the sampling resistor 2 to the conditioning circuit. For example, taking active magnetic levitation as an example, there are 10 coils in 5 degrees of freedom. The positive direction of the front radial direction (X) is assigned to channel A of the decoder, the negative direction to channel B, and so on. When channel A needs to be acquired, the MCU sends a chip select command to the decoder to select channel A. The decoder's output is connected to the MCU's ADC acquisition pin, allowing the acquisition of the sampling voltage value corresponding to the coil in the positive direction of the front radial direction (X).

[0042] Sampling resistor 2 is a high-precision sampling resistor, whose accuracy is virtually unaffected by the operating environment. The conditioning circuit converts the voltage value of the sampling resistor into a form that can be acquired by the MCU. The MCU converts the voltage value into a current value, calculates a compensation curve based on the current value, and stores the compensation curve. During system operation, the sampling resistor can also provide overcurrent protection to prevent excessive coil current.

[0043] like Figure 1 The diagram shows a flowchart of an embodiment of the method of the present invention. The current compensation method of the magnetic bearing control system may include steps S110 to S140.

[0044] In step S110, when the magnetic bearing control system is in a stopped state, a closed-loop current is applied to the coil, and the voltage value across the sampling resistor and the current value of the current sensor are obtained.

[0045] Current sensors are more accurate when detecting dynamic current during system operation; however, when detecting static current when the system is stopped, the accuracy of current sensors and sampling resistors is essentially the same. Therefore, during calibration, the current calculated from the voltage across the sampling resistor is used as the calibration standard, and the current sensors are calibrated using the static closed-loop current after system shutdown or before startup. During calibration, the system calibrates all current sensors sequentially, for example, in the order of front radial X, front radial Y, rear radial X, rear radial Y, and axial.

[0046] When the system applies closed-loop current to the coils, it sends multiple closed-loop currents to each coil, with the current range being 0–3A. Based on the sent closed-loop currents, the system can then determine the current calibration curve, the actual current curve, and thus obtain the current compensation curve.

[0047] In step S120, the current compensation curve and compensation coefficient of the current sensor are determined based on the closed-loop current, the voltage value across the sampling resistor, and the current value of the current sensor.

[0048] In some implementations, step S120, the specific process of determining the current compensation curve and compensation coefficient of the current sensor based on the closed-loop current, the voltage value across the sampling resistor, and the current value of the current sensor, includes: converting the voltage value across the sampling resistor into a current value; establishing a current calibration curve based on the closed-loop current and the converted current value, such as... Figure 8 The sampling resistor curve in the image; based on the closed-loop current and the current value of the current sensor, establish the actual current curve, such as... Figure 8 The current sensor curve in the figure; the current compensation curve is determined based on the current standard curve and the actual current curve, such as... Figure 8 The current compensation curve in the figure; the slope of the current compensation curve is determined as the compensation coefficient.

[0049] In some implementations, the closed-loop current applied to the coil is at least two currents of different magnitudes, and both closed-loop currents are greater than a preset first current value and less than a preset second current value.

[0050] The first current value is 0A, and the second current value is 3A. After each application of closed-loop current, the system collects the voltage across the sampling resistor and the current from the current sensor, thereby establishing a current calibration curve and an actual current curve. The more closed-loop current applied, the more accurate the curve.

[0051] Figure 8 In the graph, the horizontal axis represents the applied closed-loop current; for the sampling resistor curve, the vertical axis represents the current value of the sampling resistor; for the current sensor curve, the vertical axis represents the current value of the current sensor. For the current compensation curve, the horizontal axis represents the target current in the inner ring of the magnetic bearing, and the vertical axis represents the compensation current.

[0052] The slope of the current compensation curve can be calculated from the slope of the current calibration curve and the slope of the actual current curve. For example, if the slope of the current calibration curve is K and the slope of the actual current curve is 1, then the slope of the current compensation curve is 1 - (1 / k).

[0053] Figure 10 A schematic diagram of the calibration process for a current sensor, as shown below. Figure 10 As shown, the method includes:

[0054] Step 1: Begin calibration by controlling the decoder to change the circuit and connect the precision resistor corresponding to the current coil to the measurement circuit.

[0055] Step 2: The MCU sequentially sends multiple closed-loop currents between 0 and 3A. After each current transmission, the current values ​​of the current sensor and the precision resistor are recorded. Once the closed-loop current transmission is complete, the current curves of the current sensor and the precision resistor are obtained.

[0056] Step 3: Calculate the current compensation curve based on the current curves of the current sensor and the precision resistor. Then calibrate the next current sensor until all coils are calibrated.

[0057] In step S130, after the magnetic bearing control system is started, it is determined whether current compensation is required based on the compensation coefficient.

[0058] In some implementations, step S130, the specific process of determining whether current compensation is needed based on the compensation coefficient, includes: determining the relationship between the compensation coefficient and a set threshold; if the compensation coefficient is greater than the set threshold, then determining that current compensation is needed; if the compensation coefficient is less than or equal to the set threshold, then determining that current compensation is not needed.

[0059] The steeper the slope of the current compensation curve, the greater the deviation of the current sensor's detection result relative to the standard current, and the worse the accuracy of the current sensor. Therefore, when the slope is greater than the set threshold, the current sensor needs to be compensated, and when the slope is less than or equal to the set threshold, no current compensation is required.

[0060] In step S140, if it is determined that current compensation is required, the current of the current sensor is compensated according to the current compensation curve; or, the output voltage of the current sensor is compensated according to the current compensation curve so that the current of the current sensor is compensated.

[0061] When compensating for the detection results of a current sensor, there are two methods: current compensation and voltage compensation. Current compensation is a software-based method, while voltage compensation is a hardware-based method.

[0062] This solution involves using a decoder to calibrate all current sensors sequentially after each system shutdown and before each startup, updating the compensation curves accordingly. During system operation, hardware-based feedforward compensation is applied to the current sampling results based on the target current in the inner ring of the magnetic bearing. This minimizes the impact of environmental factors on the accuracy of the current sensors, thereby improving the stability and lifespan of the magnetic bearing system.

[0063] In some embodiments, step S140, the specific process of compensating the current of the current sensor according to the current compensation curve, includes: obtaining the target current of the coil; obtaining the corresponding compensation current from the current compensation curve based on the target current; adding the compensation current to the current of the current sensor to compensate the current of the current sensor, wherein the current sensor is a Hall current sensor, and the output voltage of the current sensor is the voltage across the Hall current sensor.

[0064] The current is compensated using software. When the system starts, the MCU controls the switching transistors and simultaneously adds the target current from the compensation curve to the current sensor reading, obtaining the compensated current. This compensated current is then used as the feedback value of the current loop. For example, if the displacement controller requires a target current of 1A, and the compensation current corresponding to the target current of 1A in the current compensation curve is 0.1A, then the result of adding 0.1A to the current sensor reading will be used as the compensated current.

[0065] In some embodiments, step S140, which involves compensating the output voltage of the current sensor according to the current compensation curve to compensate the current of the current sensor, includes the following specific steps: obtaining the target current of the coil; converting the current compensation curve into a voltage compensation curve based on a preset relationship between the voltage and current of the current sensor; obtaining the corresponding compensation voltage from the voltage compensation curve based on the target current; adding the compensation voltage to the output voltage of the current sensor to obtain the compensated output voltage of the current sensor; and converting the compensated output voltage of the current sensor into a current based on a preset relationship between the voltage and current of the current sensor to obtain the compensated current of the current sensor.

[0066] The voltage is compensated using hardware compensation, and the compensation circuit structure is as follows: Figure 7 As shown, the compensation voltage is first determined based on the target current and the stored voltage compensation curve. The voltage of the current sensor is added to the compensation voltage and then converted into a form that can be acquired by the MCU in the conditioning circuit 3. The MCU can obtain the compensated current based on the compensated voltage.

[0067] The system pre-stores the current-voltage conversion relationship of the current sensor. Before voltage compensation, according to... Figure 8 The current compensation curve and current-voltage conversion relationship shown below yield the following results: Figure 9 The voltage compensation curve is shown. Figure 9In the voltage compensation curve, the vertical axis represents the compensation voltage, and the horizontal axis represents the target current in the inner ring of the magnetic bearing. The magnitude of the voltage to be compensated can be determined from the target current. During compensation, the displacement sensor calculates the real-time target current based on the real-time displacement, determines the compensation voltage based on the target current, controls the DAC module to output the compensation voltage, and applies this compensation voltage to the output voltage of the current sensor through a conditioning circuit to obtain the compensated voltage. For example, if the target current is 1A, and the compensation voltage is determined to be 0.05V based on the voltage compensation curve, and the current sensor's output voltage is 2.3V, then the compensated voltage is 2.35V. The MCU then calculates the compensated current based on the compensated voltage and the current-voltage conversion relationship.

[0068] Figure 11 A flowchart illustrating the compensation process for a current sensor is shown below. Figure 11 As shown, the method includes:

[0069] Step 11: When the compressor is about to start, if the calibration of all current sensors has not been completed, calibration is performed, and the calibrated compensation curve is stored. If the calibration of all current sensors is completed, it is determined whether the coefficient of the compensation curve exceeds the threshold. If the coefficient does not exceed the threshold, no compensation is performed, and the compressor starts directly; if the coefficient exceeds the threshold, it is determined that compensation is required. Then, if software compensation is used, proceed to step 12; if hardware compensation is used, proceed to step 13.

[0070] Step 12: Based on the current compensation curve, determine the compensation current according to the target current. Add the compensation current to the feedback current value of the current sensor to obtain the compensated current. Control the compressor operation according to the compensated current.

[0071] Step 13: Based on the voltage compensation curve, determine the compensation voltage according to the target current. The MCU controls the DAC module to output the compensation voltage, which is added to the feedback voltage value from the current sensor to obtain the compensated voltage. The compressor operation is controlled according to the compensated voltage.

[0072] The technical solution of this embodiment includes a sampling resistor in the magnetic bearing control system for sampling the coil current. When the system is stopped, a closed-loop current is applied to the coil. Based on the closed-loop current, the voltage across the sampling resistor, and the current value of the current sensor, the current compensation curve and compensation coefficient of the current sensor are determined. After the system starts, the compensation coefficient is used to determine whether current compensation is needed. If current compensation is needed, the current of the current sensor is compensated according to the current compensation curve, or the output voltage of the current sensor is compensated according to the current compensation curve. Thus, by calibrating the current sensor to determine the current compensation curve when the system is stopped, and compensating the current sensor's detection results according to the current compensation curve when the system is running, the current sensor maintains high detection accuracy at all times, improving the stability of the magnetic bearing control system.

[0073] According to an embodiment of the present invention, a current compensation device for a magnetic bearing control system corresponding to a current compensation method for a magnetic bearing control system is also provided. The magnetic bearing control system includes a current sensor, a coil, and a sampling resistor; the current sensor is used to detect the current in the coil; the sampling resistor is used to sample the current in the coil.

[0074] The control principle of the magnetic bearing control system is as follows: Figure 3 and Figure 4 As shown, the controller calculates the target current through the position feedback value, and controls the switching transistors in the power amplifier by sending PWM waves with different duty cycles, thereby controlling the coil current.

[0075] like Figure 5 As shown, Hall current sensor 1 is used to acquire coil current in real time. The acquired current is fed back to the MCU controller after passing through a sampling and conditioning circuit. The MCU controls the coil current based on the acquired current and a reference current, thereby achieving closed-loop current control. Due to the lack of rigor in the manufacturing process of the current sensor and the influence of the working environment, the detection accuracy of the current sensor may decrease, leading to inaccurate coil current control and affecting the normal operation of equipment such as magnetic levitation compressors.

[0076] Therefore, this solution uses a sampling resistor in the magnetic bearing control system to calibrate the accuracy of the current sensor. Based on the calibration results, the current sensor is compensated, thereby improving its accuracy. The specific circuit for current calibration is as follows: Figure 6As shown, the power amplifier provides current to the coils in the magnetic bearing. Each coil's circuit is equipped with a Hall current sensor 1 for detecting the coil current. A sampling resistor 2 is installed at the switching transistor of the power amplifier corresponding to each coil. The current flowing through the sampling resistor 2 and the current flowing through the current coil are the same. A multi-channel decoder is used to modify the circuit, connecting the Hall current sensor 1 or the sampling resistor 2 to the conditioning circuit. For example, taking active magnetic levitation as an example, there are 10 coils in 5 degrees of freedom. The positive direction of the front radial direction (X) is assigned to channel A of the decoder, the negative direction to channel B, and so on. When channel A needs to be acquired, the MCU sends a chip select command to the decoder to select channel A. The decoder's output is connected to the MCU's ADC acquisition pin, allowing the acquisition of the sampling voltage value corresponding to the coil in the positive direction of the front radial direction (X).

[0077] Sampling resistor 2 is a high-precision sampling resistor, whose accuracy is virtually unaffected by the operating environment. The conditioning circuit converts the voltage value of the sampling resistor into a form that can be acquired by the MCU. The MCU converts the voltage value into a current value, calculates a compensation curve based on the current value, and stores the compensation curve. During system operation, the sampling resistor can also provide overcurrent protection to prevent excessive coil current.

[0078] See Figure 2 The diagram shows a structural schematic of an embodiment of the device of the present invention. The current compensation device of the magnetic bearing control system may include: an acquisition unit 102 and a control unit 104.

[0079] The acquisition unit 102 is configured to apply a closed-loop current to the coil and acquire the voltage value across the sampling resistor and the current value of the current sensor when the magnetic bearing control system is in a stopped state. The specific functions and processing of the acquisition unit 102 are described in step S110.

[0080] Current sensors are more accurate when detecting dynamic current during system operation; however, when detecting static current when the system is stopped, the accuracy of current sensors and sampling resistors is essentially the same. Therefore, during calibration, the current calculated from the voltage across the sampling resistor is used as the calibration standard, and the current sensors are calibrated using the static closed-loop current after system shutdown or before startup. During calibration, the system calibrates all current sensors sequentially, for example, in the order of front radial X, front radial Y, rear radial X, rear radial Y, and axial.

[0081] When the system applies closed-loop current to the coils, it sends multiple closed-loop currents to each coil, with the current range being 0–3A. Based on the sent closed-loop currents, the system can then determine the current calibration curve, the actual current curve, and thus obtain the current compensation curve.

[0082] Control unit 104 is configured to determine the current compensation curve and compensation coefficient of the current sensor based on the closed-loop current, the voltage value across the sampling resistor, and the current value of the current sensor. The specific functions and processing of this control unit 104 are described in step S120.

[0083] In some embodiments, the control unit 104 determines the current compensation curve and compensation coefficient of the current sensor based on the closed-loop current, the voltage value across the sampling resistor, and the current value of the current sensor. This process includes: converting the voltage value across the sampling resistor into a current value; and establishing a current calibration curve based on the closed-loop current and the converted current value, such as... Figure 8 The sampling resistor curve in the image; based on the closed-loop current and the current value of the current sensor, establish the actual current curve, such as... Figure 8 The current sensor curve in the figure; the current compensation curve is determined based on the current standard curve and the actual current curve, such as... Figure 8 The current compensation curve in the figure; the slope of the current compensation curve is determined as the compensation coefficient.

[0084] In some implementations, the closed-loop current applied to the coil is at least two currents of different magnitudes, and both closed-loop currents are greater than a preset first current value and less than a preset second current value.

[0085] The first current value is 0A, and the second current value is 3A. After each application of closed-loop current, the system collects the voltage across the sampling resistor and the current from the current sensor, thereby establishing a current calibration curve and an actual current curve. The more closed-loop current applied, the more accurate the curve.

[0086] Figure 8 In the graph, the horizontal axis represents the applied closed-loop current; for the sampling resistor curve, the vertical axis represents the current value of the sampling resistor; for the current sensor curve, the vertical axis represents the current value of the current sensor. For the current compensation curve, the horizontal axis represents the target current in the inner ring of the magnetic bearing, and the vertical axis represents the compensation current.

[0087] The slope of the current compensation curve can be calculated from the slope of the current calibration curve and the slope of the actual current curve. For example, if the slope of the current calibration curve is K and the slope of the actual current curve is 1, then the slope of the current compensation curve is 1 - (1 / k).

[0088] Figure 10 A schematic diagram of the calibration process for a current sensor, as shown below. Figure 10 As shown, the method includes:

[0089] Step 1: Begin calibration by controlling the decoder to change the circuit and connect the precision resistor corresponding to the current coil to the measurement circuit.

[0090] Step 2: The MCU sequentially sends multiple closed-loop currents between 0 and 3A. After each current transmission, the current values ​​of the current sensor and the precision resistor are recorded. Once the closed-loop current transmission is complete, the current curves of the current sensor and the precision resistor are obtained.

[0091] Step 3: Calculate the current compensation curve based on the current curves of the current sensor and the precision resistor. Then calibrate the next current sensor until all coils are calibrated.

[0092] The control unit 104 is further configured to determine whether current compensation is needed based on the compensation coefficient after the magnetic bearing control system is started. The specific functions and processing of the control unit 104 are described in step S130.

[0093] In some implementations, the control unit 104 determines whether current compensation is needed based on the compensation coefficient, including: determining the relationship between the compensation coefficient and a set threshold; if the compensation coefficient is greater than the set threshold, determining that current compensation is needed; if the compensation coefficient is less than or equal to the set threshold, determining that current compensation is not needed.

[0094] The steeper the slope of the current compensation curve, the greater the deviation of the current sensor's detection result relative to the standard current, and the worse the accuracy of the current sensor. Therefore, when the slope is greater than the set threshold, the current sensor needs to be compensated, and when the slope is less than or equal to the set threshold, no current compensation is required.

[0095] The control unit 104 is further configured to, if it is determined that current compensation is required, compensate the current of the current sensor according to the current compensation curve; or, compensate the output voltage of the current sensor according to the current compensation curve, so that the current of the current sensor is compensated, wherein the current sensor is a Hall current sensor, and the output voltage of the current sensor is the voltage across the Hall current sensor. For the specific functions and processing of this control unit 104, please refer to step S140.

[0096] When compensating for the detection results of a current sensor, there are two methods: current compensation and voltage compensation. Current compensation is a software-based method, while voltage compensation is a hardware-based method.

[0097] This solution involves using a decoder to calibrate all current sensors sequentially after each system shutdown and before each startup, updating the compensation curves accordingly. During system operation, hardware-based feedforward compensation is applied to the current sampling results based on the target current in the inner ring of the magnetic bearing. This minimizes the impact of environmental factors on the accuracy of the current sensors, thereby improving the stability and lifespan of the magnetic bearing system.

[0098] In some embodiments, the specific process by which the control unit 104 compensates the current of the current sensor according to the current compensation curve includes: obtaining the target current of the coil; obtaining the corresponding compensation current from the current compensation curve based on the target current; and adding the compensation current to the current of the current sensor to compensate the current of the current sensor.

[0099] The current is compensated using software. When the system starts, the MCU controls the switching transistors and simultaneously adds the target current from the compensation curve to the current sensor reading, obtaining the compensated current. This compensated current is then used as the feedback value of the current loop. For example, if the displacement controller requires a target current of 1A, and the compensation current corresponding to the target current of 1A in the current compensation curve is 0.1A, then the result of adding 0.1A to the current sensor reading will be used as the compensated current.

[0100] In some embodiments, the control unit 104 compensates the output voltage of the current sensor according to the current compensation curve to compensate the current of the current sensor. The specific process includes: obtaining the target current of the coil; converting the current compensation curve into a voltage compensation curve based on a preset relationship between the voltage and current of the current sensor; obtaining the corresponding compensation voltage from the voltage compensation curve based on the target current; adding the compensation voltage to the output voltage of the current sensor to obtain the compensated output voltage of the current sensor; and converting the compensated output voltage of the current sensor into current based on a preset relationship between the voltage and current of the current sensor to obtain the compensated current of the current sensor.

[0101] The voltage is compensated using hardware compensation, and the compensation circuit structure is as follows: Figure 7 As shown, the compensation voltage is first determined based on the target current and the stored voltage compensation curve. The voltage of the current sensor is added to the compensation voltage and then converted into a form that can be acquired by the MCU in the conditioning circuit 3. The MCU can obtain the compensated current based on the compensated voltage.

[0102] The system pre-stores the current-voltage conversion relationship of the current sensor. Before voltage compensation, according to... Figure 8 The current compensation curve and current-voltage conversion relationship shown below yield the following results: Figure 9 The voltage compensation curve is shown. Figure 9In the voltage compensation curve, the vertical axis represents the compensation voltage, and the horizontal axis represents the target current in the inner ring of the magnetic bearing. The magnitude of the voltage to be compensated can be determined from the target current. During compensation, the displacement sensor calculates the real-time target current based on the real-time displacement, determines the compensation voltage based on the target current, controls the DAC module to output the compensation voltage, and applies this compensation voltage to the output voltage of the current sensor through a conditioning circuit to obtain the compensated voltage. For example, if the target current is 1A, and the compensation voltage is determined to be 0.05V based on the voltage compensation curve, and the current sensor's output voltage is 2.3V, then the compensated voltage is 2.35V. The MCU then calculates the compensated current based on the compensated voltage and the current-voltage conversion relationship.

[0103] Figure 11 A flowchart illustrating the compensation process for a current sensor is shown below. Figure 11 As shown, the method includes:

[0104] Step 11: When the compressor is about to start, if the calibration of all current sensors has not been completed, calibration is performed, and the calibrated compensation curve is stored. If the calibration of all current sensors is completed, it is determined whether the coefficient of the compensation curve exceeds the threshold. If the coefficient does not exceed the threshold, no compensation is performed, and the compressor starts directly; if the coefficient exceeds the threshold, it is determined that compensation is required. Then, if software compensation is used, proceed to step 12; if hardware compensation is used, proceed to step 13.

[0105] Step 12: Based on the current compensation curve, determine the compensation current according to the target current. Add the compensation current to the feedback current value of the current sensor to obtain the compensated current. Control the compressor operation according to the compensated current.

[0106] Step 13: Based on the voltage compensation curve, determine the compensation voltage according to the target current. The MCU controls the DAC module to output the compensation voltage, which is added to the feedback voltage value from the current sensor to obtain the compensated voltage. The compressor operation is controlled according to the compensated voltage.

[0107] Since the processing and functions implemented by the device in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned methods, any details not covered in the description of this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0108] The technical solution of this invention includes a sampling resistor in the magnetic bearing control system for sampling the coil current. When the system is stopped, a closed-loop current is applied to the coil. Based on the closed-loop current, the voltage across the sampling resistor, and the current value of the current sensor, the current compensation curve and compensation coefficient of the current sensor are determined. After the system starts, the compensation coefficient is used to determine whether current compensation is needed. If current compensation is needed, the current of the current sensor is compensated according to the current compensation curve, or the output voltage of the current sensor is compensated according to the current compensation curve. Thus, by calibrating the current sensor to determine the current compensation curve when the system is stopped, and compensating the current sensor's detection results according to the current compensation curve when the system is running, the current sensor maintains high detection accuracy at all times, improving the stability of the magnetic bearing control system.

[0109] According to an embodiment of the present invention, a magnetic bearing control system corresponding to a current compensation device for a magnetic bearing control system is also provided. This magnetic bearing control system may include the current compensation device for the magnetic bearing control system described above.

[0110] Since the processing and functions implemented by the magnetic bearing control system in this embodiment are basically the same as those of the aforementioned device embodiments, principles and examples, any details not covered in this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0111] The technical solution of this invention includes a sampling resistor in the magnetic bearing control system for sampling the coil current. When the system is stopped, a closed-loop current is applied to the coil. Based on the closed-loop current, the voltage across the sampling resistor, and the current value of the current sensor, the current compensation curve and compensation coefficient of the current sensor are determined. After the system starts, the compensation coefficient is used to determine whether current compensation is needed. If current compensation is needed, the current of the current sensor is compensated according to the current compensation curve, or the output voltage of the current sensor is compensated according to the current compensation curve. Thus, by calibrating the current sensor to determine the current compensation curve when the system is stopped, and compensating the current sensor's detection results according to the current compensation curve when the system is running, the current sensor maintains high detection accuracy at all times, improving the stability of the magnetic bearing control system.

[0112] According to an embodiment of the present invention, a storage medium corresponding to a current compensation method for a magnetic bearing control system is also provided. The storage medium includes a stored program, wherein, when the program is executed, the device where the storage medium is located executes the current compensation method for the magnetic bearing control system described above.

[0113] Since the processing and functions implemented by the storage medium in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned methods, any details not covered in this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0114] The technical solution of this invention includes a sampling resistor in the magnetic bearing control system for sampling the coil current. When the system is stopped, a closed-loop current is applied to the coil. Based on the closed-loop current, the voltage across the sampling resistor, and the current value of the current sensor, the current compensation curve and compensation coefficient of the current sensor are determined. After the system starts, the compensation coefficient is used to determine whether current compensation is needed. If current compensation is needed, the current of the current sensor is compensated according to the current compensation curve, or the output voltage of the current sensor is compensated according to the current compensation curve. Thus, by calibrating the current sensor to determine the current compensation curve when the system is stopped, and compensating the current sensor's detection results according to the current compensation curve when the system is running, the current sensor maintains high detection accuracy at all times, improving the stability of the magnetic bearing control system.

[0115] According to an embodiment of the present invention, a computer program product corresponding to a current compensation method for a magnetic bearing control system is also provided. The computer program product includes a computer program that, when processed and executed, implements the steps of the current compensation method for the magnetic bearing control system described above.

[0116] Since the processing and functions implemented by the computer program product in this embodiment are basically corresponding to the embodiments, principles and examples of the aforementioned methods, any details not covered in the description of this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0117] The technical solution of this invention includes a sampling resistor in the magnetic bearing control system for sampling the coil current. When the system is stopped, a closed-loop current is applied to the coil. Based on the closed-loop current, the voltage across the sampling resistor, and the current value of the current sensor, the current compensation curve and compensation coefficient of the current sensor are determined. After the system starts, the compensation coefficient is used to determine whether current compensation is needed. If current compensation is needed, the current of the current sensor is compensated according to the current compensation curve, or the output voltage of the current sensor is compensated according to the current compensation curve. Thus, by calibrating the current sensor to determine the current compensation curve when the system is stopped, and compensating the current sensor's detection results according to the current compensation curve when the system is running, the current sensor maintains high detection accuracy at all times, improving the stability of the magnetic bearing control system.

[0118] In summary, it is readily understood by those skilled in the art that, without conflict, the aforementioned advantageous methods can be freely combined and superimposed.

[0119] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A current compensation method for a magnetic bearing control system, characterized in that, The magnetic bearing control system includes a current sensor, a coil, and a sampling resistor; the current sensor is used to detect the current in the coil; the sampling resistor is used to sample the current in the coil; the sampling resistor is also used to calibrate the accuracy of the current sensor. The method includes: When the magnetic bearing control system is in a stopped state, a closed-loop current is applied to the coil, and the voltage value across the sampling resistor and the current value of the current sensor are obtained. Based on the closed-loop current, the voltage across the sampling resistor, and the current value of the current sensor, determine the current compensation curve and compensation coefficient of the current sensor; After the magnetic bearing control system is started, it is determined whether current compensation is required based on the compensation coefficient. If it is determined that current compensation is required, the current of the current sensor is compensated according to the current compensation curve; or, the output voltage of the current sensor is compensated according to the current compensation curve so that the current of the current sensor is compensated. Specifically, the current compensation curve and compensation coefficient of the current sensor are determined based on the closed-loop current, the voltage across the sampling resistor, and the current value of the current sensor, including: The voltage value across the sampling resistor is converted into a current value; a current calibration curve is established based on the closed-loop current and the converted current value. Based on the closed-loop current and the current value of the current sensor, an actual current curve is established; The current compensation curve is determined based on the current standard curve and the actual current curve; the slope of the current compensation curve is determined as the compensation coefficient.

2. The current compensation method for the magnetic bearing control system according to claim 1, characterized in that, The closed-loop current applied to the coil is at least two currents of different magnitudes, and both closed-loop currents are greater than a preset first current value and less than a preset second current value.

3. The current compensation method for the magnetic bearing control system according to claim 1, characterized in that, Determining whether current compensation is needed based on the compensation coefficient includes: Determine the relationship between the compensation coefficient and the set threshold. If the compensation coefficient is greater than the set threshold, it is determined that current compensation is required; If the compensation coefficient is less than or equal to the set threshold, then it is determined that current compensation is not required.

4. The current compensation method for the magnetic bearing control system according to claim 1 or 2, characterized in that, Compensating the current of the current sensor according to the current compensation curve includes: Obtain the target current of the coil; The corresponding compensation current is obtained from the target current based on the current compensation curve; The compensation current is added to the current of the current sensor to compensate for the current of the current sensor.

5. The current compensation method for the magnetic bearing control system according to claim 1 or 2, characterized in that, The output voltage of the current sensor is compensated according to the current compensation curve to compensate the current of the current sensor, including: Obtain the target current of the coil; Based on the preset relationship between the voltage and current of the current sensor, the current compensation curve is converted into a voltage compensation curve. The corresponding compensation voltage is obtained from the voltage compensation curve based on the target current; The compensation voltage is added to the output voltage of the current sensor to obtain the compensated output voltage of the current sensor; Based on the preset relationship between the voltage and current of the current sensor, the output voltage of the compensated current sensor is converted into current to obtain the current of the compensated current sensor.

6. A current compensation device for a magnetic bearing control system, characterized in that, The magnetic bearing control system includes a current sensor, a coil, and a sampling resistor; the current sensor is used to detect the current in the coil; the sampling resistor is used to sample the current in the coil. The sampling resistor is also used to calibrate the accuracy of the current sensor; The device includes: The acquisition unit is configured to apply a closed-loop current to the coil and acquire the voltage value across the sampling resistor and the current value of the current sensor when the magnetic bearing control system is in a shutdown state. The control unit is configured to determine the current compensation curve and compensation coefficient of the current sensor based on the closed-loop current, the voltage value across the sampling resistor, and the current value of the current sensor. The control unit is also configured to determine whether current compensation is required based on the compensation coefficient after the magnetic bearing control system is started. The control unit is further configured to, if it is determined that current compensation is required, compensate the current of the current sensor according to the current compensation curve; or, compensate the output voltage of the current sensor according to the current compensation curve, so that the current of the current sensor is compensated. The control unit determines the current compensation curve and compensation coefficient of the current sensor based on the closed-loop current, the voltage across the sampling resistor, and the current value of the current sensor, including: The voltage value across the sampling resistor is converted into a current value; a current calibration curve is established based on the closed-loop current and the converted current value. Based on the closed-loop current and the current value of the current sensor, an actual current curve is established; The current compensation curve is determined based on the current standard curve and the actual current curve; the slope of the current compensation curve is determined as the compensation coefficient.

7. A magnetic bearing control system, characterized in that, include: The current compensation device for the magnetic bearing control system as described in claim 6.

8. A storage medium, characterized in that, The storage medium includes a stored program, wherein, when the program is executed, it controls the device containing the storage medium to perform the current compensation method of the magnetic bearing control system according to any one of claims 1 to 5.

9. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

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