Current sensing correction method and driving system

Abstract

A current sensing correction method and a driving system. The current sensing correction method comprises: obtaining a detection value of three-phase current by a measuring unit; judging whether the three-phase current maintains a direct current state according to the detection value; recording a direct current value of the three-phase current as a three-phase demagnetization value; calculating a d-axis current and a q-axis current according to the three-phase demagnetization value; calculating a d-axis correction current command and a q-axis correction current command according to a proportional constant, the d-axis current and the q-axis current; generating a three-phase demagnetization current to the measuring unit according to the d-axis correction current command and the q-axis correction current command; judging whether a demagnetization time of the measuring unit receiving the three-phase demagnetization current reaches a first predetermined time; wherein when the demagnetization time reaches the first predetermined time, the generation of the three-phase demagnetization current is stopped.

Description

Technical Field

[0001] The present disclosure relates to a current sensing calibration method, and more particularly to a current sensing calibration method for a drive system. Background Art

[0002] Current sensors composed of magnetoelectric conversion elements, such as Hall sensors, are commonly used in drive systems for driving load devices such as motors. These current sensors detect the three-phase current output by the drive system and generate corresponding voltage detection signals, allowing the drive system to adjust the three-phase current accordingly.

[0003] See also Figure 1 and Figure 2A ,in Figure 1 The current timing diagram of any two phases of the three-phase current output by the traditional drive system is: Figure 2A The magnetic induction intensity-magnetic field intensity (BH) curve diagram of the current sensor is shown in FIG. Figure 1 and Figure 2A As shown in the figure, taking the load device as an elevator motor as an example, when the elevator reaches the corresponding floor and the mechanical brake device fixes the motor, the drive system needs to output a three-phase current in a DC state to allow the motor to generate torque to support the load, so that the motor maintains zero speed. In this way, the elevator can stay at the corresponding floor. Therefore, the currents of any two phases of the three-phase current output by the drive system, such as phase a current ia and phase b current ib, are as follows Figure 1 As shown. Figure 1 As shown, while the elevator motor continuously outputs torque and maintains zero speed, the three-phase current output by the drive system (e.g., phase A current ia and phase B current ib) remains DC for a period of time until the mechanical brake device secures the motor. When the mechanical brake device secures the motor, the drive system stops outputting the three-phase current.

[0004] Furthermore, before the elevator motor begins normal operation, it first enters the starting state. While in the starting state, the motor remains immobilized by the mechanical brake until it releases. Similarly, after the mechanical brake releases, the drive system must supply three-phase current to the motor, generating output torque that balances the load torque for zero-speed control and maintains the elevator car at the desired floor. During this period, the three-phase current remains DC. Once the motor begins normal operation, the three-phase current becomes AC.

[0005] Due to the characteristics of the current sensor composed of magnetoelectric conversion elements, such as Figure 2AThis phenomenon indicates that when the current sensor receives a zero-current, three-phase current value maintained in a DC state, residual magnetization (RM) occurs on the current sensor due to the magnetic field generated by the DC current, as shown at point A or A1 in the figure. This causes the voltage detection signal generated by the current sensor at zero current to reflect a temporary voltage offset caused by the residual magnetization. This temporary voltage offset can easily cause serious errors when the controller reads the current sensor's current value.

[0006] Figure 2B Schematic diagram for reading current from a current sensor. Figure 2A and Figure 2B Assuming the residual magnetism on the current sensor follows the A curve, this residual magnetism could cause the current sensor to produce a reading of V1. However, in reality, the current signal on the current sensor should be zero, so the current sensor should not produce any reading. Similarly, assuming the residual magnetism on the current sensor follows the A1 curve, this residual magnetism could cause the current sensor to produce a reading of V2. Therefore, when the current sensor receives a current signal, the reading produced by the current sensor has a significant error.

[0007] Furthermore, after temporarily stopping the load device, the drive system must read the voltage detection signal from the current sensor to perform current offset correction for the three-phase current. The purpose of current offset correction is to compensate for two known and predictable current offset causes. The first is that the control unit within the drive system can only read positive signals. Therefore, a preset voltage offset value must be added to the current sensor's detection results so that all current sensor detection results received by the control unit are positive. The second is the voltage offset caused by temperature drift of the current sensor. Both the first and second causes can be corrected by detecting the voltage signal from the current sensor when there is no current output. Therefore, accurate compensation can be performed when the drive system performs current offset correction for the three-phase current.

[0008] However, due to the residual magnetism effect of the current sensors, when the drive system stops driving and performs three-phase current offset correction, the detection results read from the current sensors actually include errors caused by residual magnetism. Furthermore, the errors caused by residual magnetism are temporary and cannot be predicted in advance. This results in errors and inaccuracies in the current offset correction of the drive system. This affects the drive control performance of the drive device, causing the drive system to generate current ripples at the same drive frequency when driving the load device and performing current control, thereby generating vibration and noise.

[0009] Therefore, it is necessary to develop an improved current sensing calibration method and driving system to solve the above problems faced by the prior art. Summary of the Invention

[0010] The present disclosure aims to provide a current sensing calibration method and a drive system, thereby resolving the problem in which, during current offset calibration in conventional drive systems, the residual magnetism of the current sensor prevents accurate calibration, thereby affecting the control performance of the drive system and causing vibration and noise in the load device during operation.

[0011] To achieve the above objectives, the present disclosure provides a current sensing calibration method for a drive system, wherein the drive system includes a drive unit, a control unit, a measurement unit, and a storage unit. The drive unit is configured to provide a three-phase current to a load device. The control unit executes the current sensing calibration method, and the current sensing calibration method includes: obtaining detection values ​​of the three-phase currents through the measurement unit; determining whether the three-phase currents maintain a DC state based on the detection values; if the three-phase currents maintain a DC state, obtaining the DC values ​​of the three-phase currents through the measurement unit and recording the DC values ​​in the storage unit as three-phase demagnetization values; wherein when the control unit determines that the detection values ​​are zero, the current sensing calibration method further includes: calculating d-axis current and q-axis current based on the three-phase demagnetization values; calculating a d-axis correction current command and a q-axis correction current command based on a proportional constant, the d-axis current, and the q-axis current; operating the drive unit based on the d-axis correction current command and the q-axis correction current command to generate a three-phase demagnetization current for the measurement unit; and determining whether a demagnetization time during which the measurement unit receives the three-phase demagnetization current has reached a first predetermined time; wherein when the demagnetization time reaches the first predetermined time, controlling the drive unit to stop generating the three-phase demagnetization current.

[0012] To achieve the above-mentioned purpose, the present disclosure further provides a drive system, comprising: a drive unit, a control unit, a measuring unit and a storage unit. The drive unit is used to provide three-phase current to a load device. The measuring unit is used to measure the three-phase current to output a detection value of the three-phase current. The control unit is coupled to the drive unit, the measuring unit and the storage unit. The control unit determines whether the three-phase current maintains a DC state based on the detection value. When the control unit determines that the three-phase current maintains a DC state, the control unit obtains the DC value of the three-phase current through the measuring unit and records the DC value in the storage unit as a three-phase demagnetization value. When the control unit determines that the detection value is zero, the control unit calculates the d-axis current and the q-axis current based on the three-phase demagnetization value, and the control unit also calculates the d-axis correction current command and the q-axis correction current command based on the proportional constant, the d-axis current and the q-axis current. The control unit operates the drive unit based on the d-axis correction current command and the q-axis correction current command to generate a three-phase demagnetization current for the measuring unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Current timing diagram of any two phases among the three-phase current output by the traditional drive system;

[0014] Figure 2Ais a schematic diagram of the magnetic induction intensity-magnetic field intensity (BH) curve of the current sensor;

[0015] Figure 2B A schematic diagram showing how a current sensor reads the current;

[0016] Figure 3A Schematic diagram of a circuit block of a driving system 1 according to a preferred embodiment of the present disclosure;

[0017] Figure 3B 1 is a waveform diagram of the operating speed of the load device 9 connected to the drive system 1 according to a preferred embodiment of the present disclosure;

[0018] Figure 3C The waveform diagram of the three-phase current connected to the drive system 1 of the preferred embodiment of the present disclosure is as follows:

[0019] Figure 4 The q-axis current presented after the dq-axis coordinate transformation of the three-phase current output by the conventional drive system and the q-axis current presented after the dq-axis coordinate transformation of the three-phase currents ia, ib, ic output by the drive system 1 of the present disclosure;

[0020] Figure 5 Schematic diagram of the waveforms of the current harmonics and vibration frequency of the drive system 1 of the present disclosure and the current harmonics and vibration frequency of the traditional drive system;

[0021] Figure 6 1 is a flow chart of the steps of a current sensing calibration method according to a preferred embodiment of the present disclosure.

[0022] The description of the accompanying drawings is as follows:

[0023] 1: Drive system

[0024] 2: Drive unit

[0025] 3: Measurement unit

[0026] 4: Storage unit

[0027] 5: Control unit

[0028] ia, ib, ic: three-phase current

[0029] iat, ibt, ict: detection values ​​of three-phase current

[0030] 20: Rectifier circuit

[0031] C: bus capacitance

[0032] 21: Inverter

[0033] 300: Current sensing calibration method

[0034] S1~S13: Steps of current sensing calibration method DETAILED DESCRIPTION

[0035] Some typical embodiments that embody the features and advantages of the present disclosure will be described in detail in the following description. It should be understood that the present disclosure is capable of various modifications in different aspects without departing from the scope of the present disclosure, and the description and drawings are intended to be illustrative in nature and not to limit the present disclosure.

[0036] See also Figure 3A , which is a schematic block diagram of the circuit structure of the drive system 1 according to the preferred embodiment of the present disclosure. Figure 3A As shown, the drive system 1 of the present disclosure can be used to drive a load device 9, wherein the load device 9 can be, but is not limited to, an elevator motor. The drive system 1 includes a drive unit 2, a measuring unit 3, a storage unit 4, and a control unit 5. The drive unit 2 is electrically connected to the load device 9. The drive unit 2 can receive input current and convert it to provide three-phase currents ia, ib, and ic to the load device 9, thereby driving the load device 9 into an operating state. In addition, the drive unit 2 can also drive the load device 9 into a standby state. In some embodiments, the drive unit 2 can include, but is not limited to, a rectifier circuit 20, a bus capacitor C, and an inverter 21. Depending on whether the input current is a single-phase input current or a three-phase input current, the rectifier circuit 20 can be a unidirectional rectifier circuit or a three-phase rectifier circuit, and the inverter 21 can include multiple switching elements. Since the circuit architecture and operation of the rectifier circuit 20, the bus capacitor C, and the inverter 21 are already common in the field of electronic circuits, they will not be described in detail here.

[0037] The measuring unit 3 is used to measure the three-phase currents ia, ib, ic output by the driving unit 2 to output the detection values ​​iat, ibt, ict of the three-phase currents ia, ib, ic, that is, Figure 3A As shown. In some embodiments, the measuring unit 3 may include a current sensor 30 composed of a magnetoelectric conversion element, such as a Hall sensor, and the number of current sensors 30 may be three to measure the three-phase currents ia, ib, and ic respectively, and the three-phase currents ia, ib, and ic are all single-phase currents (collectively referred to as three-phase currents herein). Of course, since the remaining single-phase current can be inferred from the DC detection values ​​of two of the phase currents measured by the two current sensors, in other embodiments, the measuring unit 3 may also include only two current sensors 30 to measure the first phase current and the second phase current of the three-phase currents ia, ib, and ic, and the control unit 5 calculates the third phase current of the three-phase currents ia, ib, and ic based on the first phase current and the second phase current. It is particularly noted that the first to third phase currents can be arbitrarily combined with the a-phase current ia, the b-phase current ib, and the c-phase current ic according to needs, but the present invention is not limited to this.

[0038] The storage unit 4 can be used to store the DC detection value output by the measurement unit 3. In some embodiments, the storage unit 4 can be, but is not limited to, a non-volatile memory, such as a flash memory, an erasable and programmable read-only memory (EPROM), an electrically erasable and programmable read-only memory (EEPROM), or a hard disk.

[0039] The control unit 5 is coupled to the drive unit 2, the measurement unit 3, and the storage unit 4. The control unit 5 is configured to control the overall operation of the drive system 1. The control unit 5 can output control commands to the drive unit 2, causing the drive unit 2 to operate the inverter 21 to output three-phase currents ia, ib, and ic to drive the load device 9. In some embodiments, the control unit 5 may be, but is not limited to, a microcontroller, a processor, a central processing unit (CPU), etc.

[0040] Figure 3B 1 is a waveform diagram of the rotation speed of the load device 9 connected to the drive system 1 according to a preferred embodiment of the present disclosure. Figure 3C The waveform diagram of the three-phase current connected to the drive system 1 of the preferred embodiment of the present disclosure is shown in FIG. Figure 3C In order to clearly depict the waveform, only the a-phase current ia is shown as a representative.

[0041] It is particularly noted that, in order to facilitate the explanation of the operating principle of the present invention, the present invention is described using an elevator system including a motor as an example, but the present invention is not limited thereto. A general elevator system includes: an elevator car (not shown), a motor, a brake device (not shown), etc. In addition, the motor described in the following embodiments is Figure 3A The load device 9 is shown in FIG. 1 , but the present invention is not limited thereto.

[0042] like Figure 3A As shown, the drive system 1 outputs three-phase current (e.g., a-phase current ia, b-phase current ib, c-phase current ic) to the motor, which then moves the elevator car based on the three-phase current. Furthermore, the brake device is used to hold the motor in place, allowing the elevator car to stay at a designated floor. Please also refer to Figures 3A to 3C , to illustrate the following embodiments.

[0043] At Figure 3B and Figure 3C In interval 1, when the elevator car approaches the designated corresponding floor, the control unit 5 controls the drive unit 2 to reduce the frequency of the three-phase current (ia, ib, ic) in the AC state. In this way, the speed of the motor will gradually decrease, such as Figure 3B The interval 1 is shown.

[0044] When the elevator just arrives at the designated corresponding floor, the control unit 5 controls the drive unit 2 to generate a three-phase current (ia, ib, ic) that maintains a DC state, such as Figure 3C As shown in interval 2. At this time, the motor generates torque based on the three-phase current (ia, ib, ic) that maintains the DC state to support the weight of the elevator car. Since the torque generated by the motor and the weight of the elevator car reach a force balance, the motor speed is zero, as shown in Figure 3B This is shown in Interval 2 of the figure. Those skilled in the art refer to this as zero-speed motor control. Note that during Intervals 1 and 2, the elevator system's brakes are not engaged (the brakes are not activated). Typically, when an elevator arrives at a designated floor, the elevator car is not yet aligned with the designated floor (also known as leveling). Therefore, zero-speed motor control is required to allow the elevator to remain at the designated floor and fine-tune the car's position to achieve leveling.

[0045] At Figure 3B and Figure 3C In interval 2, the control unit 5 determines whether the three-phase currents (ia, ib, ic) maintain a DC state based on the detection values ​​(iat, ibt, ict). If the control unit 5 determines that the three-phase currents (ia, ib, ic) do not maintain a DC state and have returned to an AC state (indicating that the motor is not in zero-speed control), the control unit 5 continues to receive the detection values ​​(iat, ibt, ict). Conversely, if the control unit 5 determines that the three-phase currents (ia, ib, ic) maintain a DC state (indicating that the motor is in zero-speed control), the control unit 5 obtains the DC values ​​of the three-phase currents (ia, ib, ic) that maintain a DC state through the measurement unit 3. The control unit 5 then records these DC values ​​in the storage unit 4 for use in the demagnetization process of the current sensor 30. The control unit 5 uses the DC values ​​stored in the storage unit 4 as the three-phase demagnetization values.

[0046] At Figure 3C In interval 2, the three-phase currents (ia, ib, ic) remaining in a DC state are the primary cause of residual magnetism in the current sensor 30 in the measurement unit 3. In other words, the extent to which residual magnetism affects the current sensor 30 is directly related to the magnitude of the three-phase demagnetization value. This three-phase demagnetization value is the primary reason why the current sensor 30 cannot accurately measure the three-phase currents (ia, ib, ic).

[0047] When the control unit 5 determines that the detection value (iat, ibt, ict) of the three-phase current (ia, ib, ic) is zero, the control unit 5 determines that the brake device fixes the motor (the motor speed must be zero and the three-phase current (ia, ib, ic) is close to zero). Figure 3B and Figure 3CTherefore, the control unit 5 determines that the motor enters the standby state.

[0048] Therefore, Figure 3C In interval 3, when the control unit 5 determines that the detection values ​​(iat, ibt, ict) of the three-phase currents (ia, ib, ic) are zero, the control unit 5 calculates the d-axis current and the q-axis current based on the three-phase demagnetization values ​​stored in the storage unit 4. Then, the control unit 5 further calculates the d-axis correction current command and the q-axis correction current command based on a proportional constant, the d-axis current, and the q-axis current. After the control unit 5 completes the calculation of the d-axis correction current command and the q-axis correction current command, Figure 3C The interval 3 ends.

[0049] Next, enter Figure 3C In the interval 4, the control unit 5 operates the drive unit 2 according to the d-axis correction current command and the q-axis correction current command to generate a three-phase demagnetization current for the measuring unit 3. Then, the control unit 5 determines whether the demagnetization time of the measuring unit 3 receiving the three-phase demagnetization current reaches a first predetermined time. The first predetermined time is Figure 3C The interval 4 (1.5 seconds to 2 seconds) is provided, but the present invention is not limited thereto. It should be noted that the first predetermined time is a software setting value, and the present invention can be flexibly adjusted according to actual conditions.

[0050] When the control unit 5 determines that the demagnetization time has reached the first predetermined time, the control unit 5 controls the drive unit 2 to stop generating the three-phase demagnetization current. Then, when the control unit 5 determines that the demagnetization time has reached the first predetermined time, the control unit 5 enters Figure 3C In interval 5, the control unit 5 measures the three-phase current (ia, ib, ic) through the measuring unit 3 to serve as the three-phase current correction value. In this embodiment, after the measuring unit 3 receives the three-phase demagnetization current to remove the residual magnetism, the three-phase current (ia, ib, ic) measured by the measuring unit 3 can be regarded as the offset of the current reading value (for example: Figure 2B V1 or V2).

[0051] Next, enter Figure 3C In the interval 5, the control unit 5 determines whether the correction time for the three-phase current correction value to remain unchanged reaches a second predetermined time. The second predetermined time is Figure 3C The interval 5 (2 seconds to 2.5 seconds) is not limited thereto. It is important to note that the second predetermined time is a software setting and can be flexibly adjusted according to actual circumstances. When the correction time reaches the second predetermined time, the control unit 5 stores the three-phase current correction value in the storage unit 4. Conversely, if the correction time does not reach the second predetermined time, the control unit 5 continues to determine the three-phase current correction value.

[0052] Next, enter Figure 3C In interval 6, when the elevator car is ready to start to the next designated floor, the brake device changes from fixing the motor to releasing the motor. When the brake device does not fix the motor (the brake device is not activated), the control unit 5 first performs zero speed control of the motor. When performing zero speed control of the motor, the control unit 5 receives the detection values ​​(iat, ibt, ict) of the three-phase current (ia, ib, ic) to determine whether the motor (load device 9) has entered the operating state. At this time, the control unit 5 obtains the detection values ​​of the three-phase current (ia, ib, ic) through the measuring unit 3, and the control unit 5 retrieves the correction values ​​of the three-phase current (ia, ib, ic) from the storage unit 4. Then. The control unit 5 subtracts the working value from the three-phase current correction value in the storage unit 4 to obtain the actual value of the three-phase current (ia, ib, ic), and the control unit 5 operates the drive unit 2 according to the actual value.

[0053] exist Figure 3C After the interval 6, the three-phase current (ia, ib, ic) is in AC state. That is, Figure 3C After interval 6, the motor starts operating to move the elevator car. At this time, the control unit 5 similarly obtains the detected values ​​of the three-phase currents (ia, ib, ic) and subtracts the detected values ​​from the three-phase current correction values ​​stored in the storage unit 4 to obtain the actual values ​​of the three-phase currents (ia, ib, ic). The control unit 5 then operates the drive unit 2 based on the actual values ​​to adjust the frequency or amplitude of the three-phase currents (ia, ib, ic) in the AC state, but the present invention is not limited thereto.

[0054] In a preferred embodiment, before the brake device fixes the motor, the control unit 5 captures the last value of the three-phase current (ia, ib, ic) that maintains the DC state, for example, capturing the last value of the three-phase current (ia, ib, ic) at Figure 3C The values ​​of the three-phase current (ia, ib, ic) at the first second of interval 2 are used as the above three-phase demagnetization values. Therefore, in a preferred embodiment, Figure 3C In the interval 2, the control unit 5 continuously stores the DC values ​​of the three-phase current (ia, ib, ic) in the storage unit 4. Figure 3C During interval 3, the control unit 5 retrieves the last DC value stored in the storage unit 4 as the three-phase demagnetization value, and performs demagnetization and calibration through the above-mentioned operation process. In this way, the accuracy of the current sensor 30 can be significantly increased.

[0055] Those skilled in the art will appreciate that the control unit 5 can generate pulse width signals to the drive unit 2 based on the actual values ​​of the three-phase currents, thereby controlling the switching operation of the multiple switching elements of the inverter 21 of the drive unit 2 to generate three-phase currents (ia, ib, ic) in an AC or DC state. Furthermore, those skilled in the art will appreciate that the control unit 5 can also generate pulse width signals to the drive unit 2 based on the d-axis correction current command and the q-axis correction current command, thereby controlling the switching operation of the multiple switching elements of the inverter 21 of the drive unit 2 to generate a three-phase demagnetization current. Therefore, this disclosure will not be further elaborated.

[0056] In some other embodiments, the present invention may also be applied to other systems with AC / DC current switching, such as an Internet of Things system (IoT system) and a Smart Grid system, but the present invention is not limited thereto.

[0057] The following briefly describes the operating principle of the control unit 5. A person skilled in the art can use equation (1) to calculate the d-axis current id and the q-axis current iq based on the three-phase currents ia, ib, and ic. Equation (1) is as follows:

[0058]

[0059] in, is the transformation matrix from the stationary coordinate axis to the rotating coordinate axis, θ e is the rotor position.

[0060] Therefore, when the load device 9 enters zero speed control, the control unit 5 uses the DC values ​​of the three-phase currents ia, ib, and ic that maintain the DC state as the three-phase demagnetization values, and the d-axis current id and q-axis current iq calculated based on the three-phase demagnetization values ​​can be expressed as follows: (where the three-phase demagnetization value i a_stop 、i b_stop andi c_stop Substituting into equation (1), we can obtain equation (2)

[0061]

[0062] where i d_stop andi q_stop are the current values ​​of the d-axis current and the q-axis current respectively calculated by the control unit 5, i a_stop 、i b_stop andi c_stop They are the sizes of the three-phase demagnetization values ​​respectively.

[0063] Furthermore, the control unit 5 calculates the d-axis correction current command and the q-axis correction current command according to the proportional constant, the d-axis current and the q-axis current, wherein the d-axis correction current command i * d_DeMag And q-axis correction current command i * q_DeMag It is expressed as follows:

[0064]

[0065] where K DeMag is the proportionality constant.

[0066] The control unit 5 operates the drive unit 2 according to the d-axis correction current command and the q-axis correction current command, so that the drive unit 2 excites the load device 9 to generate a three-phase demagnetization current to the measuring unit 3, wherein the three-phase demagnetization current i * a_DeMag 、i * b_DeMag andi * c_DeMag It can be obtained from the following equations (4) and (5):

[0067]

[0068]

[0069] See also Figure 4 and Figure 5 ,in Figure 4 The timing diagram is a q-axis current presented after the dq-axis coordinate conversion of the three-phase current output by the drive system of the present disclosure and the q-axis current presented after the dq-axis coordinate conversion of the three-phase current output by the traditional drive system. Figure 5 Schematic diagram of the waveforms of the current harmonics and vibration frequency of the drive system disclosed herein and the current harmonics and vibration frequency of the traditional drive system. Figure 4 and Figure 5 As shown, since the drive system 1 of the present disclosure can stimulate the load device 9 to generate a three-phase demagnetization current to the measuring unit 3, thereby demagnetizing the measuring unit 3, Figure 4 It can be seen that the drive system 1 of the present disclosure (such as Figure 4 Compared with the traditional drive system (such as Figure 4 As shown below) can effectively improve the output torque ripple problem, and by Figure 5 It can be seen that under the same driving frequency, for example, 16.3 Hz, the current harmonics (such as Figure 5 The dashed line above) is compared with the current harmonics of the traditional drive system (such as Figure 5The solid line shown above) is reduced by about 56.5%, and the vibration of the drive system 1 of the present disclosure (such as Figure 5 The dashed line below) is compared with the vibration harmonics of the traditional drive system (such as Figure 5 Therefore, the current offset correction of the drive system 1 of the present invention can be more accurate, so that the drive control performance of the drive system 1 of the present invention is greatly improved compared with the drive control performance of the traditional drive system.

[0070] See also Figure 6 , and cooperate with Figures 3A to 3C ,in Figure 6 The figure is a flow chart illustrating the steps of a current sensing calibration method 300 according to a preferred embodiment of the present disclosure. As shown, the current sensing calibration method 300 of the present disclosure is applicable to the drive system 1 described in the aforementioned embodiment and is used for the drive unit 2. This current sensing calibration method can be executed by a control unit 5. The drive system 1 includes the drive unit 2, the control unit 5, a measurement unit 3, and a storage unit 4. The drive unit 2 is configured to provide three-phase currents (ia, ib, ic) to a load device 9 (e.g., a motor). The control unit 5 executes the current sensing calibration method 300, which includes the following steps.

[0071] In step S1 , the control unit 5 obtains the detection values ​​(iat, ibt, ict) of the three-phase currents (ia, ib, ic) through the measuring unit 3 .

[0072] In step S2, the control unit 5 determines whether the three-phase currents (ia, ib, ic) maintain a DC state based on the detected values ​​(iat, ibt, ict) of the three-phase currents (ia, ib, ic). If the three-phase currents (ia, ib, ic) do not maintain a DC state, the control unit 5 returns to step S1. Conversely, if the three-phase currents (ia, ib, ic) maintain a DC state, the control unit 5 proceeds to step S3.

[0073] In step S3 , if the three-phase currents (ia, ib, ic) maintain the DC state, the control unit 5 obtains the DC values ​​of the three-phase currents (ia, ib, ic) through the measuring unit 3 .

[0074] In step S4 , the control unit 5 records the DC values ​​of the three-phase currents (ia, ib, ic) in the storage unit 4 as three-phase demagnetization values.

[0075] In step S5, the control unit 5 determines whether the detected values ​​(iat, ibt, ict) of the three-phase currents (ia, ib, ic) are zero. If the control unit 5 determines that the detected values ​​(iat, ibt, ict) of the three-phase currents (ia, ib, ic) are zero (indicating that the brake device is engaged to hold the motor in place), the control unit 5 proceeds to step S6, where the control unit 5 calculates the d-axis current and the q-axis current based on the three-phase demagnetization values. Conversely, if the control unit 5 determines in step S5 that the detected values ​​(iat, ibt, ict) of the three-phase currents (ia, ib, ic) are not zero, the control unit 5 repeatedly executes steps S3 to S5 to repeatedly record the three-phase demagnetization values ​​in the storage unit 4.

[0076] In some embodiments, the current sensing calibration method disclosed herein may further include the following steps.

[0077] In step S7, the control unit 5 calculates the d-axis correction current command and the q-axis correction current command according to the proportional constant, the d-axis current and the q-axis current. In this embodiment, steps S2 to S7 are performed at Figure 3B and Figure 3C 2 to 3, but the present invention is not limited thereto.

[0078] In step S8, the control unit 5 operates the driving unit 2 according to the d-axis correction current command and the q-axis correction current command to generate a three-phase demagnetization current for the measuring unit 3 (for example: Figure 3B and Figure 3C interval 4).

[0079] In step S9, the control unit 5 determines whether the demagnetization time of the three-phase demagnetization current received by the measuring unit 3 reaches the first predetermined time. The first predetermined time is Figure 3C The interval 4 (1.5 seconds to 2 seconds) is provided, but the present invention is not limited thereto. It should be noted that the first predetermined time is a software setting value, and the present invention can be flexibly adjusted according to actual conditions.

[0080] In step S10, if the result of step S9 indicates that the demagnetization time has reached the first predetermined time, the control unit 5 controls the drive unit 2 to stop generating the three-phase demagnetization current. After step S10 is completed, the demagnetization of the measuring unit 3 is complete. Alternatively, if the result of step S9 indicates that the demagnetization time has not reached the first predetermined time, step S8 is executed again.

[0081] In step S11, when the demagnetization time reaches the first predetermined time, the control unit 5 measures the three-phase current through the measuring unit 3 to serve as the three-phase current correction value (for example: Figure 3B and Figure 3C interval 5).

[0082] In step S12, the control unit 5 determines whether the correction time for the three-phase current correction value to remain unchanged reaches a second predetermined time (for example: Figure 3B and Figure 3C The second predetermined time is Figure 3C The interval 5 (2 seconds to 2.5 seconds) is not limited thereto. It should be noted that the second predetermined time is a software setting value, and the present invention can be flexibly adjusted according to actual conditions.

[0083] In step S13, when the correction time reaches the second predetermined time as determined in step S12, the control unit 5 stores the three-phase current correction value in the storage unit 4. Alternatively, when the correction time does not reach the second predetermined time as determined in step S12, step S11 is executed again.

[0084] Pay special attention to Figure 6 The above steps S1 to S13 are only used to describe an example of the current sensing calibration method 300 of the present invention. Figure 6 The order of the above steps S1 to S13 is not intended to limit the present invention.

[0085] In summary, the present disclosure provides a current sensing calibration method and a drive system. The current sensing calibration method of the present disclosure can operate a drive unit of the drive system to generate a three-phase demagnetization current for a measuring unit when a load device enters a startup state, thereby demagnetizing the measuring unit. As a result, the drive system of the present disclosure can perform current offset calibration more accurately, thereby improving the drive control performance of the drive system of the present disclosure and preventing vibration and noise generated by the load device during operation.

[0086] It should be noted that the above description is merely a preferred embodiment for the purpose of illustrating the present disclosure. The present disclosure is not limited to the described embodiment. The scope of the present disclosure is determined by the appended claims. Furthermore, the present disclosure may be modified in various ways by those skilled in the art, without departing from the scope of the appended claims.

Claims

1. A current sensing calibration method for a drive system, wherein the drive system comprises a drive unit, a control unit, a measurement unit, and a storage unit, wherein the drive unit is configured to provide a three-phase current to a load device, and the control unit executes the current sensing calibration method, wherein the current sensing calibration method comprises: Obtaining detection values ​​of the three-phase current through the measuring unit; determining whether the three-phase current maintains a DC state according to the detection value; If the three-phase current maintains the DC state, obtaining the DC value of the three-phase current through the measuring unit; recording the DC value in the storage unit as a three-phase demagnetization value; When the control unit determines that the detection value is zero, the current sensing calibration method further includes: Calculating a d-axis current and a q-axis current according to the three-phase demagnetization values; Calculating a d-axis correction current command and a q-axis correction current command according to a proportional constant, the d-axis current, and the q-axis current; operating the driving unit according to the d-axis correction current command and the q-axis correction current command to generate a three-phase demagnetization current for the measuring unit; and Determining whether a demagnetization time during which the measuring unit receives the three-phase demagnetization current reaches a first predetermined time; When the demagnetization time reaches the first predetermined time, the driving unit is controlled to stop generating the three-phase demagnetization current.

2. The current sensing calibration method according to claim 1 , further comprising: When the demagnetization time reaches the first predetermined time, the three-phase current is measured by the measuring unit to serve as a three-phase current correction value.

3. The current sensing calibration method according to claim 2 , further comprising: Determining whether a correction time during which the three-phase current correction value remains unchanged reaches a second predetermined time; When the correction time reaches the second predetermined time, the three-phase current correction value is stored in the storage unit.

4. A drive system comprising: a drive unit for providing three-phase current to a load device; a measuring unit, configured to measure the three-phase current and output detection values ​​of the three-phase current; a storage unit; as well as a control unit coupled to the driving unit, the measuring unit, and the storage unit; The control unit determines whether the three-phase current maintains a DC state according to the detection value; When the control unit determines that the three-phase current maintains the DC state, the control unit obtains the DC value of the three-phase current through the measuring unit and records the DC value in the storage unit as the three-phase demagnetization value; When the control unit determines that the detection value is zero, the control unit calculates a d-axis current and a q-axis current according to the three-phase demagnetization value, and further calculates a d-axis correction current command and a q-axis correction current command according to a proportional constant, the d-axis current, and the q-axis current; The control unit operates the driving unit according to the d-axis correction current command and the q-axis correction current command to generate a three-phase demagnetization current for the measuring unit.

5. The drive system according to claim 4, wherein: The control unit determines whether a demagnetization time during which the measuring unit receives the three-phase demagnetization current reaches a first predetermined time; when the demagnetization time reaches the first predetermined time, the control unit controls the driving unit to stop generating the three-phase demagnetization current.

6. The drive system according to claim 5, wherein: When the demagnetization time reaches the first predetermined time, the control unit measures the three-phase current through the measuring unit to use the three-phase current correction value.

7. The drive system according to claim 6, wherein: The control unit determines whether a correction time during which the three-phase current correction value remains unchanged reaches a second predetermined time; When the correction time reaches the second predetermined time, the control unit stores the three-phase current correction value in the storage unit.

8. The drive system according to claim 7, wherein: When the control unit receives the detection value through the measuring unit, the control unit retrieves the three-phase current correction value from the storage unit.

9. The drive system according to claim 8, wherein: The control unit subtracts the detection value from the three-phase current correction value in the storage unit to obtain the actual value of the three-phase current, and the control unit operates the driving unit according to the actual value.

10. The drive system according to claim 4, wherein: The measuring unit includes three Hall sensors, and the three Hall sensors are respectively used to measure the three-phase currents.

11. The drive system according to claim 4, wherein: The measuring unit includes two Hall sensors, and the two Hall sensors are respectively used to measure a first phase current and a second phase current of the three-phase current, wherein the control unit calculates a third phase current of the three-phase current according to the first phase current and the second phase current.

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