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

Abstract

The invention discloses a current compensation method and device of a magnetic bearing control system, the magnetic bearing control system, a storage medium and a computer program product. A sampling resistor used for sampling coil current is arranged in the magnetic bearing control system. The method comprises the following steps: when a system is shut down, applying closed-loop current to a coil, and determining a current compensation curve and a compensation coefficient of a current sensor according to the closed-loop current, voltage values at two ends of a sampling resistor and a current value of the current sensor; after the system is started, determining whether current compensation is needed or not according to the compensation coefficient; if it is determined that current compensation needs to be carried out, 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. According to the scheme, the current sensor is calibrated when the system is shut down, the detection result of the current sensor is compensated according to the current compensation curve obtained through calibration when the system runs, and it is ensured that the current sensor always keeps high precision.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic suspension control, and in particular relates to a current compensation method and device for a magnetic bearing control system, a magnetic bearing control system, a storage medium and a computer program product. Background Art

[0002] The magnetic levitation centrifuge uses magnetic force to suspend the rotor in the air, so that there is no mechanical contact between the rotor and the stator. It has the advantages of low mechanical wear, low energy consumption, low noise, long life, no lubrication, no oil pollution, etc. The magnetic bearing control system adopts double closed-loop control, the outer loop is the displacement loop, and the inner loop is the current loop. Controlling the magnetic bearing current is the core of controlling magnetic levitation. A stable and reliable current loop requires accurate current sampling feedback.

[0003] Hall current sensors are widely used in magnetic bearing current loops due to their high precision, high linearity, fast response, strong anti-interference ability and easy integration. However, the mechanical vibration during centrifuge operation, the humid operating environment and the lax paint process during the production process will greatly reduce the service life of the Hall current sensor, causing problems with detection accuracy and performance.

[0004] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0005] The object of the present invention is to provide a current compensation method, device, magnetic bearing control system, storage medium and computer program product for a magnetic bearing control system to solve the problem of reduced detection accuracy and performance of the Hall current sensor in the magnetic bearing control system in the related schemes, so as to achieve the effect of ensuring that the current sensor always maintains a high detection accuracy and improving the stability of the magnetic bearing control system by calibrating the current sensor when the system is shut down to determine the current compensation curve and compensating the detection result of the current sensor according to the current compensation curve when the system is running.

[0006] The present invention provides a current compensation method for a magnetic bearing control system, wherein the magnetic bearing control system comprises 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 method comprises: when the magnetic bearing control system is in a shutdown state, applying a closed-loop current to the coil, and obtaining a voltage value across the sampling resistor and a current value of the current sensor; determining a current compensation curve and a compensation coefficient of the current sensor according to 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 required according to the compensation coefficient; if it is determined that current compensation is required, 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 so that the current of the current sensor is compensated.

[0007] In some embodiments, a current compensation curve and a compensation coefficient of the current sensor are determined according to 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 according to the closed-loop current and the converted current value; establishing an actual current curve according to the closed-loop current and the current value of the current sensor; determining the current compensation curve according to 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 embodiments, the closed-loop current applied to the coil is at least two currents of different magnitudes, and both of the closed-loop currents are greater than a preset first current value and less than a preset second current value.

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

[0010] In some embodiments, compensating the current of the current sensor according to the current compensation curve includes: obtaining a target current of the coil; obtaining a corresponding compensation current from the current compensation curve according to the target current; and adding the compensation current to the current of the current sensor to compensate for 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 so that the current of the current sensor is compensated, 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 a corresponding compensation voltage from the voltage compensation curve according to 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; 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] Matching the above method, the present invention provides a current compensation device for a magnetic bearing control system on the other hand, 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 when the magnetic bearing control system is in a shutdown state, and to acquire the voltage value across the sampling resistor and the current value of the current sensor; a control unit, configured to determine the current compensation curve and compensation coefficient of the current sensor according to 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 according to the compensation coefficient after the magnetic bearing control system is started; the control unit is also configured to compensate the current of the current sensor according to the current compensation curve if it is determined that current compensation is required; 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.

[0013] In some embodiments, the control unit determines the current compensation curve and compensation coefficient of the current sensor according to 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 according to the closed-loop current and the converted current value; establishing an actual current curve according to the closed-loop current and the current value of the current sensor; determining the current compensation curve according to 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 embodiments, the closed-loop current applied to the coil is at least two currents of different magnitudes, and both of the closed-loop currents are greater than a preset first current value and less than a preset second current value.

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

[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 a corresponding compensation current from the current compensation curve according to the target current; and adding the compensation current to the current of the current sensor to compensate for 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 so that the current of the current sensor is compensated, 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 a corresponding compensation voltage from the voltage compensation curve according to 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; 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] Matching the above-mentioned device, the present invention further provides a magnetic bearing control system on the other hand, including: the current compensation device of the magnetic bearing control system described above.

[0019] In accordance with the above method, the present invention provides a storage medium on the other hand, wherein the storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the current compensation method of the magnetic bearing control system described above.

[0020] Matching the above method, the present invention further provides a computer program product on the other hand, wherein the computer program product includes a computer program, and when the computer program product is processed and executed, the steps of the current compensation method of the magnetic bearing control system are implemented.

[0021] The scheme of the present invention is that a sampling resistor for sampling coil current is provided in the magnetic bearing control system; when the system is shut down, a closed-loop current is applied to the coil, and the current compensation curve and compensation coefficient of the current sensor are determined according to the closed-loop current, the voltage value at both ends of the sampling resistor, and the current value of the current sensor; after the system is started, it is determined whether current compensation is required according to 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. Thus, by calibrating the current sensor to determine the current compensation curve when the system is shut down, and compensating the detection result of the current sensor according to the current compensation curve when the system is running, it is ensured that the current sensor always maintains a high detection accuracy, and the stability of the magnetic bearing control system is improved.

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

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic flow chart of an embodiment of a current compensation method for a magnetic bearing control system of the present invention;

[0025] Figure 2 It is a structural schematic diagram of an embodiment of a current compensation device of a magnetic bearing control system of the present invention;

[0026] Figure 3 It is the principle schematic diagram of the magnetic bearing control system;

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

[0028] Figure 5 It is a structural schematic diagram of a magnetic bearing current sampling circuit without adding current compensation;

[0029] Figure 6 It is a structural diagram of a magnetic bearing current sampling circuit with added current compensation;

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

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

[0032] Fig. 9 The voltage compensation curve after adding voltage compensation;

[0033] Fig.10 A schematic diagram of a process for calibrating a current sensor;

[0034] Fig.11 Schematic diagram of the process of compensating the current sensor.

[0035] In conjunction with 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 DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[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 on and off of the switch tube in the power amplifier by sending PWM waves with different duty cycles to achieve control of the coil current.

[0040] like Figure 5 As shown, the Hall current sensor 1 is used to collect the coil current in real time. The collected current is fed back to the MCU controller after passing through the sampling and conditioning circuit. The MCU controls the coil current based on the collected current and the reference current, thereby realizing closed-loop control of the current. Due to the lax production process of the current sensor and the influence of the working environment of the current sensor, the detection accuracy of the current sensor may decrease, which in turn leads to inaccurate coil current control, affecting the normal operation of equipment such as magnetic levitation compressors.

[0041] Therefore, this solution sets a sampling resistor in the magnetic bearing control system to calibrate the accuracy of the current sensor, and compensates the current sensor based on the calibration result, thereby improving the accuracy of the current sensor. Figure 6As shown, the power amplifier provides current for the coil in the magnetic bearing, and each coil is provided with a Hall current sensor 1 for detecting the coil current. A sampling resistor 2 is provided at the switch tube of the power amplifier corresponding to each coil, and the current flowing through the sampling resistor 2 is the same as the current flowing through the current coil. The multi-channel decoder is used to change the circuit so that the Hall current sensor 1 or the sampling resistor 2 is connected to the conditioning circuit. For example, taking active magnetic suspension as an example, there are 10 coils in 5 degrees of freedom. The positive direction of the front radial X is assigned to the A channel of the decoder, and the negative direction of the front radial is assigned to the B channel, and so on. When the A channel needs to be collected, the MCU sends a chip select A channel input instruction to the decoder, and the output of the decoder is connected to the ADC acquisition pin of the MCU. At this time, the sampling voltage value of the sampled electric group corresponding to the positive direction coil of the front radial X can be collected.

[0042] Sampling resistor 2 is a high-precision sampling resistor, which is hardly affected by the working environment and its accuracy is not reduced. The conditioning circuit is used to convert the voltage value of the sampling resistor into a form that can be collected by the MCU. The MCU will convert the voltage value into a current value, calculate the compensation curve based on the current value, and store the compensation curve. During the operation of the system, the sampling resistor can also perform overcurrent protection to prevent the coil current from being too large.

[0043] like Figure 1 The flow chart of an embodiment of the method of the present invention is shown in FIG. 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 shutdown state, a closed-loop current is applied to the coil, and a voltage value across the sampling resistor and a current value of the current sensor are obtained.

[0045] When detecting the dynamic current during the operation of the system, the current sensor is more accurate; when detecting the static current when the system stops running, the accuracy of the current sensor and the sampling resistor is basically the same. Therefore, when calibrating, the current calculated based on the sampling resistor voltage is used as the calibration standard, and the static closed-loop current after the system is shut down or before it is turned on is used to calibrate the current sensor. During the calibration process, the system will calibrate all current sensors in sequence, 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 coil, multiple closed-loop currents are sent to each coil, and the current range is 0 to 3 A. Then, based on the sent closed-loop current, the current calibration curve and the current actual curve can be determined to obtain the current compensation curve.

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

[0048] In some embodiments, in step S120, the specific process of determining the current compensation curve and compensation coefficient of the current sensor according to 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 according to the closed-loop current and the converted current value, such as Figure 8 According to the closed-loop current and the current value of the current sensor, an actual current curve is established, such as Figure 8 The current sensor curve in the current sensor curve; determining the current compensation curve according to the current standard curve and the current actual curve, such as Figure 8 The current compensation curve in the embodiment of the present invention is used; and the slope of the current compensation curve is determined as the compensation coefficient.

[0049] In some embodiments, the closed-loop current applied to the coil is at least two currents of different magnitudes, and both of the 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 0, and the second current value is 3A. Each time a closed-loop current is applied, the system will collect the voltage across the sampling resistor and the current of the current sensor to establish a current calibration curve and a current actual curve. The more closed-loop current is applied, the more accurate the curve will be.

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

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

[0053] Fig.10 The schematic diagram of the process of calibrating the current sensor is as follows: Fig.10 As shown, the method includes:

[0054] Step 1, start calibration, control the decoder to change the circuit, and connect the precision resistor corresponding to the current coil to the measurement circuit.

[0055] Step 2: MCU sends multiple closed-loop currents between 0 and 3A in sequence, and records the current value of the current sensor and the current value of the precision resistor after each current is sent. After the closed-loop current is sent, the current curve of the current sensor and the current curve of the precision resistor are obtained.

[0056] Step 3: Calculate the current compensation curve based on the current curve of the current sensor and the current curve of 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 according to the compensation coefficient.

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

[0059] The greater the slope of the current compensation curve, the greater the deviation of the detection result of the current sensor 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] At 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 the detection result of the current sensor, it is divided into current compensation and voltage compensation. Current compensation is a software compensation method, and voltage compensation is a hardware compensation method.

[0062] This solution uses a decoder to calibrate all current sensors in sequence and update the compensation curve after each system shutdown or before startup. During system operation, hardware feedforward compensation is performed on the current sampling results according to the target current of the inner ring of the magnetic bearing, thereby eliminating the influence of the current sensor accuracy reduction caused by environmental factors as much as possible, and improving the stability and service life of the magnetic bearing system.

[0063] In some embodiments, in 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 a corresponding compensation current from the current compensation curve according to the target current; adding the compensation current to the current of the current sensor to compensate for 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 by software compensation. When the system starts, the MCU controls the switch tube and adds the current corresponding to the target current of the compensation curve to the current of the current sensor to obtain the compensated current, which is used as the feedback value of the current loop. For example, 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 of the current sensor is used as the compensated current.

[0065] In some embodiments, in step S140, the specific process of compensating the output voltage of the current sensor according to the current compensation curve so that the current of the current sensor is compensated 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 a corresponding compensation voltage from the voltage compensation curve according to 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; 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 by hardware compensation. The compensation circuit structure is as follows: Figure 7 As shown, firstly, the compensation voltage is determined based on the target current and the stored voltage compensation curve, and the voltage of the current sensor is added to the compensation voltage and then converted into a form that can be collected 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, Figure 8 The current compensation curve and current-voltage conversion relationship shown in the figure are as follows: Fig. 9 The voltage compensation curve is shown. Fig. 9In the figure, for the voltage compensation curve, the ordinate is the compensation voltage, and the abscissa is the target current of the inner ring of the magnetic bearing. The voltage to be compensated can be obtained according to the target current. When performing compensation, the displacement sensor calculates the real-time target current through the real-time displacement, determines the compensation voltage according to the target current, controls the DAC module to output the compensation voltage, and adds the compensation voltage to the output voltage of the current sensor through the conditioning circuit to obtain the compensated voltage. For example, the target current is 1A, and the compensation voltage is determined to be 0.05V according to the voltage compensation curve. At this time, the output voltage of the current sensor is 2.3V, and the compensated voltage is 2.35V. Then the MCU converts the compensated current according to the compensated voltage and the current-voltage conversion relationship.

[0068] Fig.11 The schematic diagram of the process of compensating the current sensor is as follows: Fig.11 As shown, the method includes:

[0069] Step 11: When the compressor is ready 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 has been 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 is started directly; if the coefficient exceeds the threshold, it is determined that compensation is required, and then if software compensation is used, step 12 is executed, and if hardware compensation is used, step 13 is executed.

[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 operation of the compressor 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, and adds the compensation voltage to the feedback voltage value of the current sensor to obtain the compensated voltage. The compressor is controlled to operate according to the compensated voltage.

[0072] According to the technical solution of this embodiment, a sampling resistor for sampling coil current is provided in the magnetic bearing control system; when the system is shut down, a closed-loop current is applied to the coil, and the current compensation curve and compensation coefficient of the current sensor are determined according to the closed-loop current, the voltage value at both ends of the sampling resistor, and the current value of the current sensor; after the system is started, it is determined whether current compensation is required according to 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. Thus, by calibrating the current sensor to determine the current compensation curve when the system is shut down, and compensating the detection result of the current sensor according to the current compensation curve when the system is running, it is ensured that the current sensor always maintains a high detection accuracy, thereby improving the stability of the magnetic bearing control system.

[0073] According to an embodiment of the present invention, a current compensation device of a magnetic bearing control system corresponding to the current compensation method of the 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 of the coil; and the sampling resistor is used to sample the current of 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 on and off of the switch tube in the power amplifier by sending PWM waves with different duty cycles to achieve control of the coil current.

[0075] like Figure 5 As shown, the Hall current sensor 1 is used to collect the coil current in real time. The collected current is fed back to the MCU controller after passing through the sampling and conditioning circuit. The MCU controls the coil current based on the collected current and the reference current, thereby realizing closed-loop control of the current. Due to the lax production process of the current sensor and the influence of the working environment of the current sensor, the detection accuracy of the current sensor may decrease, which in turn leads to inaccurate coil current control, affecting the normal operation of equipment such as magnetic levitation compressors.

[0076] Therefore, this solution sets a sampling resistor in the magnetic bearing control system to calibrate the accuracy of the current sensor, and compensates the current sensor based on the calibration result, thereby improving the accuracy of the current sensor. Figure 6As shown, the power amplifier provides current for the coil in the magnetic bearing, and each coil is provided with a Hall current sensor 1 for detecting the coil current. A sampling resistor 2 is provided at the switch tube of the power amplifier corresponding to each coil, and the current flowing through the sampling resistor 2 is the same as the current flowing through the current coil. The multi-channel decoder is used to change the circuit so that the Hall current sensor 1 or the sampling resistor 2 is connected to the conditioning circuit. For example, taking active magnetic suspension as an example, there are 10 coils in 5 degrees of freedom. The positive direction of the front radial X is assigned to the A channel of the decoder, and the negative direction of the front radial is assigned to the B channel, and so on. When the A channel needs to be collected, the MCU sends a chip select A channel input instruction to the decoder, and the output of the decoder is connected to the ADC acquisition pin of the MCU. At this time, the sampling voltage value of the sampled electric group corresponding to the positive direction coil of the front radial X can be collected.

[0077] Sampling resistor 2 is a high-precision sampling resistor, which is hardly affected by the working environment and its accuracy is not reduced. The conditioning circuit is used to convert the voltage value of the sampling resistor into a form that can be collected by the MCU. The MCU will convert the voltage value into a current value, calculate the compensation curve based on the current value, and store the compensation curve. During the operation of the system, the sampling resistor can also perform overcurrent protection to prevent the coil current from being too large.

[0078] See also Figure 2 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 when the magnetic bearing control system is in a shutdown state, and acquire the voltage value across the sampling resistor and the current value of the current sensor. The specific functions and processing of the acquisition unit 102 refer to step S110.

[0080] When detecting the dynamic current during the operation of the system, the current sensor is more accurate; when detecting the static current when the system stops running, the accuracy of the current sensor and the sampling resistor is basically the same. Therefore, when calibrating, the current calculated based on the sampling resistor voltage is used as the calibration standard, and the static closed-loop current after the system is shut down or before it is turned on is used to calibrate the current sensor. During the calibration process, the system will calibrate all current sensors in sequence, 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 coil, multiple closed-loop currents are sent to each coil, and the current range is 0 to 3 A. Then, based on the sent closed-loop current, the current calibration curve and the current actual curve can be determined to obtain the current compensation curve.

[0082] The control unit 104 is configured to determine the current compensation curve and compensation coefficient of the current sensor according to 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 the control unit 104 refer to step S120.

[0083] In some embodiments, the control unit 104 determines the current compensation curve and compensation coefficient of the current sensor according to 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 according to the closed-loop current and the converted current value, such as Figure 8 According to the closed-loop current and the current value of the current sensor, an actual current curve is established, such as Figure 8 The current sensor curve in the current sensor curve; determining the current compensation curve according to the current standard curve and the current actual curve, such as Figure 8 The current compensation curve in the embodiment of the present invention is used; and the slope of the current compensation curve is determined as the compensation coefficient.

[0084] In some embodiments, the closed-loop current applied to the coil is at least two currents of different magnitudes, and both of the 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 0, and the second current value is 3A. Each time a closed-loop current is applied, the system will collect the voltage across the sampling resistor and the current of the current sensor to establish a current calibration curve and a current actual curve. The more closed-loop current is applied, the more accurate the curve will be.

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

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

[0088] Fig.10 The schematic diagram of the process of calibrating the current sensor is as follows: Fig.10 As shown, the method includes:

[0089] Step 1, start calibration, control the decoder to change the circuit, and connect the precision resistor corresponding to the current coil to the measurement circuit.

[0090] Step 2: MCU sends multiple closed-loop currents between 0 and 3A in sequence, and records the current value of the current sensor and the current value of the precision resistor after each current is sent. After the closed-loop current is sent, the current curve of the current sensor and the current curve of the precision resistor are obtained.

[0091] Step 3: Calculate the current compensation curve based on the current curve of the current sensor and the current curve of 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 required according to the compensation coefficient after the magnetic bearing control system is started. The specific functions and processing of the control unit 104 refer to step S130.

[0093] In some embodiments, the control unit 104 determines whether current compensation is required based on the compensation coefficient, and the specific process includes: judging the size relationship between the compensation coefficient and a set threshold; if the compensation coefficient is greater than the set threshold, determining that current compensation is required; if the compensation coefficient is less than or equal to the set threshold, determining that current compensation is not required.

[0094] The greater the slope of the current compensation curve, the greater the deviation of the detection result of the current sensor 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. The specific functions and processing of the control unit 104 refer to step S140.

[0096] When compensating the detection result of the current sensor, it is divided into current compensation and voltage compensation. Current compensation is a software compensation method, and voltage compensation is a hardware compensation method.

[0097] This solution uses a decoder to calibrate all current sensors in sequence and update the compensation curve after each system shutdown or before startup. During system operation, hardware feedforward compensation is performed on the current sampling results according to the target current of the inner ring of the magnetic bearing, thereby eliminating the influence of the current sensor accuracy reduction caused by environmental factors as much as possible, and improving the stability and service life of the magnetic bearing system.

[0098] In some embodiments, the control unit 104 performs a specific process of compensating the current of the current sensor according to the current compensation curve, including: obtaining the target current of the coil; obtaining a corresponding compensation current from the current compensation curve according to the target current; and adding the compensation current to the current of the current sensor to compensate for the current of the current sensor.

[0099] The current is compensated by software compensation. When the system starts, the MCU controls the switch tube and adds the current corresponding to the target current of the compensation curve to the current of the current sensor to obtain the compensated current, which is used as the feedback value of the current loop. For example, 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 of the current sensor is 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 so that the current of the current sensor is compensated, and the specific process includes: obtaining the target current of the coil; based on a preset relationship between the voltage and current of the current sensor, converting the current compensation curve into a voltage compensation curve; from the voltage compensation curve, obtaining a corresponding compensation voltage according to 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; based on a preset relationship between the voltage and current of the current sensor, converting the compensated output voltage of the current sensor into a current to obtain the compensated current of the current sensor.

[0101] The voltage is compensated by hardware compensation. 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 in the conditioning circuit 3 into a form that can be collected by the MCU, and 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, Figure 8 The current compensation curve and current-voltage conversion relationship shown in the figure are as follows: Fig. 9 The voltage compensation curve is shown. Fig. 9In the figure, for the voltage compensation curve, the ordinate is the compensation voltage, and the abscissa is the target current of the inner ring of the magnetic bearing. The voltage to be compensated can be obtained according to the target current. When performing compensation, the displacement sensor calculates the real-time target current through the real-time displacement, determines the compensation voltage according to the target current, controls the DAC module to output the compensation voltage, and adds the compensation voltage to the output voltage of the current sensor through the conditioning circuit to obtain the compensated voltage. For example, the target current is 1A, and the compensation voltage is determined to be 0.05V according to the voltage compensation curve. At this time, the output voltage of the current sensor is 2.3V, and the compensated voltage is 2.35V. Then the MCU converts the compensated current according to the compensated voltage and the current-voltage conversion relationship.

[0103] Fig.11 The schematic diagram of the process of compensating the current sensor is as follows: Fig.11 As shown, the method includes:

[0104] Step 11: When the compressor is ready 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 has been 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 is started directly; if the coefficient exceeds the threshold, it is determined that compensation is required, and then if software compensation is used, step 12 is executed, and if hardware compensation is used, step 13 is executed.

[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 operation of the compressor 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, and adds the compensation voltage to the feedback voltage value of the current sensor to obtain the compensated voltage. The compressor is controlled to operate according to the compensated voltage.

[0107] Since the processing and functions implemented by the device of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0108] According to the technical solution of the present invention, a sampling resistor for sampling coil current is provided in the magnetic bearing control system; when the system is shut down, a closed-loop current is applied to the coil, and the current compensation curve and compensation coefficient of the current sensor are determined according to the closed-loop current, the voltage value at both ends of the sampling resistor, and the current value of the current sensor; after the system is started, whether current compensation is required is determined according to 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. Thus, by calibrating the current sensor to determine the current compensation curve when the system is shut down, and compensating the detection result of the current sensor according to the current compensation curve when the system is running, it is ensured that the current sensor always maintains a high detection accuracy, thereby 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 of a magnetic bearing control system is also provided. The magnetic bearing control system may include: the current compensation device of the magnetic bearing control system described above.

[0110] Since the processing and functions implemented by the magnetic bearing control system of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned device, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0111] According to the technical solution of the present invention, a sampling resistor for sampling coil current is provided in the magnetic bearing control system; when the system is shut down, a closed-loop current is applied to the coil, and the current compensation curve and compensation coefficient of the current sensor are determined according to the closed-loop current, the voltage value at both ends of the sampling resistor, and the current value of the current sensor; after the system is started, whether current compensation is required is determined according to 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. Thus, by calibrating the current sensor to determine the current compensation curve when the system is shut down, and compensating the detection result of the current sensor according to the current compensation curve when the system is running, it is ensured that the current sensor always maintains a high detection accuracy, thereby 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, wherein the storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the current compensation method for the magnetic bearing control system described above.

[0113] Since the processing and functions implemented by the storage medium of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0114] According to the technical solution of the present invention, a sampling resistor for sampling coil current is provided in the magnetic bearing control system; when the system is shut down, a closed-loop current is applied to the coil, and the current compensation curve and compensation coefficient of the current sensor are determined according to the closed-loop current, the voltage value at both ends of the sampling resistor, and the current value of the current sensor; after the system is started, whether current compensation is required is determined according to 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. Thus, by calibrating the current sensor to determine the current compensation curve when the system is shut down, and compensating the detection result of the current sensor according to the current compensation curve when the system is running, it is ensured that the current sensor always maintains a high detection accuracy, thereby improving the stability of the magnetic bearing control system.

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

[0116] Since the processing and functions implemented by the computer program product of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0117] According to the technical solution of the present invention, a sampling resistor for sampling coil current is provided in the magnetic bearing control system; when the system is shut down, a closed-loop current is applied to the coil, and the current compensation curve and compensation coefficient of the current sensor are determined according to the closed-loop current, the voltage value at both ends of the sampling resistor, and the current value of the current sensor; after the system is started, whether current compensation is required is determined according to 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. Thus, by calibrating the current sensor to determine the current compensation curve when the system is shut down, and compensating the detection result of the current sensor according to the current compensation curve when the system is running, it is ensured that the current sensor always maintains a high detection accuracy, thereby improving the stability of the magnetic bearing control system.

[0118] In summary, it is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0119] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in 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 of the coil; the sampling resistor is used to sample the current of the coil; The method comprises: When the magnetic bearing control system is in a shutdown state, a closed-loop current is applied to the coil, and a voltage value across the sampling resistor and a current value of the current sensor are obtained; Determine a current compensation curve and a compensation coefficient of the current sensor according to 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 required according to 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.

2. The current compensation method of the magnetic bearing control system according to claim 1 is characterized in that: Determining a current compensation curve and a compensation coefficient of the current sensor according to the closed-loop current, the voltage value across the sampling resistor, and the current value of the current sensor, including: Converting the voltage value at both ends of the sampling resistor into a current value; establishing a current calibration curve according to the closed-loop current and the converted current value; Establishing a current actual curve according to the closed-loop current and the current value of the current sensor; The current compensation curve is determined according to the current standard curve and the current actual curve; and the slope of the current compensation curve is determined as the compensation coefficient.

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

4. The current compensation method of the magnetic bearing control system according to claim 1 or 2, characterized in that: Determining whether current compensation is required according to the compensation coefficient includes: Determining the magnitude relationship between the compensation coefficient and a set threshold; If the compensation coefficient is greater than a set threshold, it is determined that current compensation is required; If the compensation coefficient is less than or equal to the set threshold, it is determined that current compensation is not required.

5. The current compensation method of the magnetic bearing control system according to any one of claims 1 to 3, characterized in that: Compensating the current of the current sensor according to the current compensation curve includes: obtaining a target current of the coil; From the current compensation curve, obtaining a corresponding compensation current according to the target current; The compensation current is added to the current of the current sensor to compensate for the current of the current sensor.

6. The current compensation method of a magnetic bearing control system according to any one of claims 1 to 3, characterized in that: 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, comprising: obtaining a target current of the coil; Based on a preset relationship between a voltage and a current of the current sensor, converting the current compensation curve into a voltage compensation curve; From the voltage compensation curve, obtaining a corresponding compensation voltage according to 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; Based on a preset relationship between the voltage and the current of the current sensor, the compensated output voltage of the current sensor is converted into current to obtain the compensated current of the current sensor.

7. 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 of the coil; the sampling resistor is used to sample the current of the coil; The device comprises: an acquisition unit, configured to apply a closed-loop current to the coil when the magnetic bearing control system is in a shutdown state, and acquire a voltage value across the sampling resistor and a current value of the current sensor; A control unit, configured to determine a current compensation curve and a compensation coefficient of the current sensor according to 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 required according to 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.

8. A magnetic bearing control system, characterized in that: include: The current compensation device of the magnetic bearing control system as claimed in claim 7.

9. A storage medium, characterized in that: The storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the current compensation method of the magnetic bearing control system according to any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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