Current sampling circuit, motor control MCU and motor control system

Abstract

The embodiment of the utility model provides a current sampling circuit, a motor control MCU and a motor control system, the current sampling circuit comprises two groups of same sampling units and filtering units, and the sampling units are respectively connected with a servo motor. The sampling unit comprises two sampling paths connected in parallel and two modulators connected to the output ends of the sampling paths respectively, and the current conduction directions of the two sampling paths are opposite to each other, so that the positive phase and the negative phase of sampling current can be separated; the sampling positive current and the sampling negative current are processed through the modulator and input into the independent channel of the filtering unit, and the sampling positive current and the sampling negative current are subtracted, so that the offset error in the sampling process is counteracted, and the precision and the real-time performance of current sampling are improved.

Description

Technical Field

[0001] This application relates to the field of digital signal processing, and in particular to a current sampling circuit, a motor control MCU, and a motor control system for servo motors. Background Technology

[0002] SDFM (Sigma-Delta Filter Modulator) is a filter that converts analog signals into digital signals through modulation techniques. It can include Sigma-Delta filters and Sigma-Delta modulators.

[0003] In the field of three-phase current sampling in motor control systems, existing technologies generally employ a discrete architecture based on Sigma-Delta modulators, such as... Figure 1 As shown. Specifically, each phase current signal needs to be configured with an independent sampling resistor and a Sigma-Delta modulator. A pulse density modulated bit stream is generated by measuring the voltage difference across the resistor, and the digital signal is reconstructed by the Sinc filter module inside the microcontroller unit (MCU).

[0004] Limited by the filtering characteristics of the SDFM module, the high-order Sinc filter introduces a significant group delay during downsampling. This delay increases linearly with the filter order, causing a phase lag between the sampled current value and the actual operating condition. Under high dynamic load conditions, this directly affects the response speed of the field-oriented control algorithm, leading to torque ripple and decreased system stability. Secondly, the reference voltage offset and gain error of each phase modulator in the discrete architecture are inconsistent. During temperature drift and long-term operation, these errors accumulate through the independent calculation process of the SDFM channels, ultimately resulting in DC offset and amplitude distortion in the three-phase current calculation results. Furthermore, the existing solution has significant limitations in hardware resource utilization: as a dedicated digital filtering unit, the SDFM module's four-channel architecture only uses two channels in typical three-phase motor control scenarios, while the third and fourth channels remain idle for extended periods. These technical bottlenecks make it difficult for traditional sampling schemes to meet the comprehensive requirements of high-precision servo systems for real-time performance, anti-interference capabilities, and cost optimization. Summary of the Invention

[0005] This application provides a current sampling circuit, a motor control MCU, and a motor control system for servo motors to meet the comprehensive requirements of high-precision servo systems for real-time performance, anti-interference, and cost optimization.

[0006] In a first aspect, embodiments of this application provide a current sampling circuit for a servo motor, comprising:

[0007] First sampling unit, second sampling unit, filtering unit;

[0008] The first sampling unit is connected to the first phase of the servo motor; the second sampling unit is connected to the second phase of the servo motor.

[0009] The first sampling unit includes a first sampling path, a second sampling path, and two modulators; the first sampling path and the second sampling path are connected in parallel and the currents flowing through the first sampling path and the second sampling path are in opposite directions;

[0010] The second sampling unit includes a third sampling path, a fourth sampling path, and two modulators; the third sampling path and the fourth sampling path are connected in parallel and the currents flowing through the third sampling path and the fourth sampling path are in opposite directions;

[0011] The filtering unit is connected to the output of the modulator and performs filtering processing on the received digital signal.

[0012] In one possible implementation, the first sampling path includes a first diode and a first sampling resistor, the first diode and the first sampling resistor being connected in series, wherein the conduction direction of the first diode is the first current direction; the second sampling path includes a second diode and a second sampling resistor, the second diode and the second sampling resistor being connected in series, wherein the conduction direction of the second diode is the second current direction, and the first current direction is opposite to the second current direction. In one possible implementation, the third sampling path includes a third diode and a third sampling resistor, the third diode and the third sampling resistor being connected in series, wherein the conduction direction of the third diode is the first current direction;

[0013] The fourth sampling path includes a fourth diode and a fourth sampling resistor, which are connected in series. The conduction direction of the fourth diode is the second current direction, and the first current direction is opposite to the second current direction.

[0014] In one possible implementation, the third sampling path includes a third diode, a third sampling resistor, and a fifth diode, which are connected in series in sequence, wherein the conduction direction of the third diode and the fifth diode is the first current direction.

[0015] The fourth sampling path includes a fourth diode, a fourth sampling resistor, and a sixth diode, which are connected in series. The conduction direction of the fourth diode and the sixth diode is the second current direction, and the first current direction is opposite to the second current direction.

[0016] In one possible implementation, the first sampling path includes a first diode, a first sampling resistor, and a seventh diode, wherein the first diode, the seventh diode, and the first sampling resistor are connected in series, and the conduction direction of the first diode and the seventh diode is the first current direction;

[0017] The second sampling path includes a second diode, a second sampling resistor, and an eighth diode. The second diode, the eighth diode, and the second sampling resistor are connected in series. The conduction direction of the second diode and the eighth diode is the second current direction, and the first current direction is opposite to the second current direction.

[0018] The third sampling path includes a third diode, a third sampling resistor, and a fifth diode, which are connected in series. The conduction direction of the third diode and the fifth diode is the first current direction.

[0019] The fourth sampling path includes a fourth diode, a fourth sampling resistor, and a sixth diode, which are connected in series. The conduction direction of the fourth diode and the sixth diode is the second current direction, and the first current direction is opposite to the second current direction.

[0020] In one possible implementation, the modulator includes a first modulator and a second modulator;

[0021] The first modulator is connected to the first sampling path and is used to convert the analog signal output by the first sampling path into a first digital signal;

[0022] The second modulator is connected to the second sampling path and is used to convert the analog signal output by the second sampling path into a second digital signal. In one possible implementation, the filtering unit includes a register for recording the first digital signal and the second digital signal output by the first modulator and the second modulator. The first digital signal and the second digital signal recorded in the registers corresponding to the first sampling path and the second sampling path are subtracted to obtain the sampling current of the first phase circuit of the motor.

[0023] In one possible implementation, the modulator includes a third modulator and a fourth modulator;

[0024] The third modulator is connected to the third sampling path and is used to convert the analog signal output by the third sampling path into a third digital signal.

[0025] The fourth modulator is connected to the fourth sampling path and is used to convert the analog signal output by the fourth sampling path into a fourth digital signal.

[0026] The filtering unit includes a register for recording the third digital signal and the fourth digital signal output by the third modulator and the fourth modulator. The third digital signal and the fourth digital signal recorded in the registers corresponding to the third sampling path and the fourth sampling path are subtracted to obtain the sampling current of the second phase circuit of the motor.

[0027] Secondly, this application provides a motor control MCU, including the current sampling circuit as described in the first aspect.

[0028] Thirdly, this application provides a motor control system, including a motor control MCU and a motor as described in the second aspect;

[0029] The motor control MCU is connected to the motor.

[0030] The embodiments of this application provide a current sampling circuit, a motor control MCU, and a motor control system for servo motors. The current sampling circuit includes two identical sampling units and a filtering unit. The sampling units are respectively connected to two phases of the servo motor. Each sampling unit includes two parallel sampling paths and two modulators respectively connected to the sampling paths. The current conduction directions of the two sampling paths are opposite to each other, thereby separating the positive and negative phases of the sampling current. The positive and negative sampling currents are processed by the modulators and input into separate channels of the filtering unit. The positive and negative sampling currents are subtracted, thereby offsetting the offset error in the sampling process and improving the accuracy and real-time performance of current sampling. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0032] Figure 1 This is a motor current sampling circuit based on existing technology;

[0033] Figure 2 This application provides a current sampling circuit for use in servo motors;

[0034] Figure 3 The current sampling circuit of the first embodiment provided in this application;

[0035] Figure 4 The current sampling circuit provided in the second embodiment of this application;

[0036] Figure 5 The current sampling circuit provided in the third embodiment of this application;

[0037] Figure 6 This is a schematic diagram of the structure of the motor control MCU provided in this application;

[0038] Figure 7 A schematic diagram of the motor control system provided in this application.

[0039] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0040] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0041] SDFM (Sigma-Delta Filter Modulator) is a filter that converts analog signals into digital signals using modulation techniques. It is commonly used for high-precision analog-to-digital conversion. For example, it can be used in motor control systems as an advanced digital filter. Advanced digital filtering refers to the use of complex algorithms and techniques in signal processing to achieve efficient and accurate signal filtering.

[0042] SDFM can include Sigma-Delta filters and Sigma-Delta modulators, and there can be one or more Sigma-Delta filters and Sigma-Delta modulators. The Sigma-Delta filter has four independent input channels, each of which can receive a bit stream from an independent Sigma-Delta modulator. The received bit stream is then transmitted to an independent digital decimation filter, which filters and decimates the bit stream to remove high-frequency noise and reduce the data rate, thereby obtaining an effective digital signal.

[0043] In motor control applications, the input channel of a Sigma-Delta filter is typically used for current measurement. Specifically, a Sigma-Delta modulator samples the voltage difference across a sampling resistor, converting the current into a voltage signal. This voltage signal is then converted into a digital bitstream; since voltage is generated by current, the digital bitstream represents the current. The input channel of the Sigma-Delta filter receives this digital bitstream from the Sigma-Delta modulator and transmits it to a digital decimation filter to output a precise digital current value. This digital current value can be used to control motor torque and speed.

[0044] In the field of three-phase current sampling in motor control systems, the motor is controlled by three-phase current, namely phase a, phase b and phase c. There is a 120-degree phase difference between phase a and phase b, and a 120-degree phase difference between phase b and phase c. The phase difference makes the vector sum of the total current at any point in time zero, thereby achieving balanced and efficient power transmission. Therefore, in practical applications, it is only necessary to collect the current of any two phases to obtain the complete three-phase current.

[0045] Existing technologies generally employ a discrete architecture based on Sigma-Delta modulators, such as... Figure 1 As shown. Specifically, each phase current signal needs to be configured with an independent sampling resistor and a Sigma-Delta modulator. A pulse density modulated bit stream is generated by measuring the voltage difference across the resistor, and the digital signal is reconstructed by the Sinc filter module inside the microcontroller unit (MCU).

[0046] Limited by the filtering characteristics of the SDFM module, the high-order Sinc filter introduces a significant group delay during downsampling. This delay increases linearly with the filter order, resulting in a phase lag between the current sample value and the actual operating condition. Under high dynamic load conditions, this will directly affect the response speed of the field-oriented control algorithm, thereby causing torque ripple and a decrease in system stability.

[0047] Secondly, the reference voltage offset and gain error of each phase modulator in the discrete architecture are inconsistent. During temperature drift and long-term operation, such errors will accumulate through the independent calculation process of the SDFM channel, eventually leading to DC offset and amplitude distortion of the three-phase current calculation results.

[0048] In addition, the existing solution has obvious shortcomings in the utilization of hardware resources: as a dedicated digital filtering unit, the SDFM module only uses two channels in a typical three-phase motor control scenario, while the third and fourth channels of the SDFM module are idle for a long time.

[0049] The aforementioned technical bottlenecks make it difficult for traditional sampling schemes to meet the comprehensive requirements of high-precision servo systems for real-time performance, anti-interference capabilities, and cost optimization.

[0050] The sampling method provided in this application can also be used for analog-to-digital conversion in fields such as communication systems and biomedicine.

[0051] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0052] Figure 2 The current sampling circuit for servo motors provided in this application, such as Figure 2 As shown, the current sampling circuit 10 includes two identical sampling units and a filtering unit.

[0053] Two identical sampling units are connected to two phases of the servo motor, respectively. For example, the first sampling unit is connected to phase a of the servo motor, and the second sampling unit is connected to phase b of the servo motor.

[0054] Each sampling unit includes two parallel sampling paths and two modulators, with the current conduction directions of the two parallel sampling paths being opposite to each other. For example, the first sampling unit includes a first sampling path 101 and a second sampling path 102, and the second sampling path includes a third sampling path 103 and a fourth sampling path 104.

[0055] Since the two sampling units are identical, taking the first sampling unit as an example, the current direction of the first sampling path 101 is the first current direction, and the current direction of the second sampling path 102 is the second current direction. The first current direction is opposite to the second current direction.

[0056] For example, the modulator can be a Sigma-Delta modulator, or other types of modulators, such as a successive approximation register (SAR) modulator.

[0057] The first modulator 105 is connected to the first sampling path 101 and is used to convert the analog signal output by the first sampling path 101 into a first digital signal; the second modulator 106 is connected to the second sampling path 102 and is used to convert the analog signal output by the second sampling path into a second digital signal; the third modulator 107 is connected to the third sampling path 103 and is used to convert the analog signal output by the third sampling path into a third digital signal; the fourth modulator 108 is connected to the fourth sampling path 104 and is used to convert the analog signal output by the fourth sampling path into a fourth digital signal.

[0058] The filtering unit 109 is connected to the first modulator 105, the second modulator 106, the third modulator 107, and the fourth modulator 108. The filtering unit includes registers for recording the first digital signal and the second digital signal output by the first modulator 105 and the second modulator 106, and subtracting the first digital signal and the second digital signal recorded in the registers corresponding to the first sampling path 101 and the second sampling path 102 to obtain the sampling current of the first phase circuit of the motor; it is also used to record the third digital signal and the fourth digital signal output by the third modulator 107 and the fourth modulator 108, and subtract the third digital signal and the fourth digital signal recorded in the registers corresponding to the third sampling path 103 and the fourth sampling path 104 to obtain the sampling current of the second phase circuit of the motor.

[0059] For example, the filtering unit can be an SDFM module with a four-channel architecture, where each channel can be individually connected to a modulator. The filtering unit 109 may include data pins for receiving digital signals transmitted by the modulator. The advantage of having two sampling paths with opposite conduction directions in the sampling unit is that it can separate the positive and negative currents controlled by the motor. Each sampling path only samples either the positive or negative current. If there is an offset error during the sampling process of each sampling path, the offset error can be canceled by subtracting the register values ​​corresponding to the two currents in the filtering unit. Simultaneously, the current range of each current sample is reduced by half, improving the quantization accuracy of the modulator.

[0060] This application also provides a current sampling circuit according to the first embodiment, such as... Figure 3 As shown,

[0061] The first sampling path 101 includes a first diode D1 and a first sampling resistor R1, which are connected in series. The conduction direction of the first diode D1 is the first current direction.

[0062] The second sampling path 102 includes a second diode D2 and a second sampling resistor R2, which are connected in series. The conduction direction of the second diode D2 is the second current direction, and the first current direction is opposite to the second current direction.

[0063] The third sampling path 103 includes a third diode D3 and a third sampling resistor R3, which are connected in series. The conduction direction of the third diode D3 is the first current direction.

[0064] The fourth sampling path 104 includes a fourth diode D4 and a fourth sampling resistor R4, which are connected in series. The conduction direction of the fourth diode D4 is the second current direction, and the first current direction is opposite to the second current direction.

[0065] This application also provides a current sampling circuit according to a second embodiment, such as... Figure 4 As shown,

[0066] The first sampling path 101 includes a first diode D1, a first sampling resistor R1, and a fifth diode D5. The first diode D1, the first sampling resistor R1, and the fifth diode D5 are connected in series in sequence, wherein the conduction direction of the first diode D1 and the fifth diode D5 is the first current direction.

[0067] The second sampling path 102 includes a second diode D2, a second sampling resistor R2, and a sixth diode D6. The second diode D2, the second sampling resistor R2, and the sixth diode D6 are connected in series. The conduction direction of the second diode D2 and the sixth diode D6 is the second current direction, and the first current direction is opposite to the second current direction.

[0068] The third sampling path 103 includes a third diode D3 and a third sampling resistor R3, which are connected in series. The conduction direction of the third diode D3 is the first current direction.

[0069] The fourth sampling path 104 includes a fourth diode D4 and a fourth sampling resistor R4, which are connected in series. The conduction direction of the fourth diode D4 is the second current direction, and the first current direction is opposite to the second current direction.

[0070] This application also provides a current sampling circuit according to a third embodiment, such as... Figure 5 As shown,

[0071] The first sampling path 101 includes a first diode D1, a first sampling resistor R1, and a fifth diode D5. The first diode D1, the first sampling resistor R1, and the fifth diode D5 are connected in series in sequence, wherein the conduction direction of the first diode D1 and the fifth diode D5 is the first current direction.

[0072] The second sampling path 102 includes a second diode D2, a second sampling resistor R2, and a sixth diode D6. The second diode D2, the second sampling resistor R2, and the sixth diode D6 are connected in series. The conduction direction of the second diode D2 and the sixth diode D6 is the second current direction, and the first current direction is opposite to the second current direction.

[0073] The third sampling path 103 includes a third diode D3, a third sampling resistor R3 and a seventh diode D7, which are connected in series. The conduction direction of the third diode D3 and the seventh diode D7 is the first current direction.

[0074] The fourth sampling path 104 includes a fourth diode D4, a fourth sampling resistor R4, and an eighth diode D8. The fourth diode D4, the fourth sampling resistor R4, and the eighth diode D8 are connected in series. The conduction direction of the fourth diode D4 and the eighth diode D8 is the second current direction, and the first current direction is opposite to the second current direction.

[0075] In one embodiment, the sampling path can also be implemented using devices such as transformers, which only acquire the positive and negative half-cycle signals and separate the positive and negative currents of the alternating current.

[0076] This application also provides a motor control MCU 30, such as... Figure 6 As shown, the motor control MCU3 includes the aforementioned current sampling circuit 10. The specific details of the current sampling circuit 10 can be found in the description of the above embodiments; for the sake of brevity, they will not be repeated here.

[0077] This application embodiment also provides a motor control system 40, such as Figure 7 As shown, the motor control system 40 includes the motor control MCU 30 and the motor 20 described above. For details regarding the motor control MCU 30, please refer to the description of the above embodiments; for brevity, it will not be repeated here.

[0078] This application also provides a computer-readable storage medium storing computer instructions, which, when executed by a processor, are used to implement the methods provided in the various embodiments described above.

[0079] This application also provides a computer program product including computer instructions stored in a computer-readable storage medium. At least one processor of the device can read the computer instructions from the computer-readable storage medium, and the at least one processor executes the computer instructions to cause the device to perform the methods provided in the various embodiments described above.

[0080] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A current sampling circuit applied to a servo motor, characterized by, The current sampling circuit comprises: a first sampling unit, a second sampling unit and a filter unit; the first sampling unit is connected to a first phase of the servo motor; the second sampling unit is connected to a second phase of the servo motor; the first sampling unit comprises a first sampling path, a second sampling path and two modulators; the first sampling path and the second sampling path are connected in parallel and the current directions through the first sampling path and the second sampling path are opposite; the second sampling unit comprises a third sampling path, a fourth sampling path and two modulators; the third sampling path and the fourth sampling path are connected in parallel and the current directions through the third sampling path and the fourth sampling path are opposite; the filter unit is connected to the output ends of the modulators and performs filtering processing on the received digital signals.

2. The current sampling circuit of claim 1, wherein, the first sampling path comprises a first diode and a first sampling resistor, the first diode and the first sampling resistor are connected in series, and the conduction direction of the first diode is the first current direction; the second sampling path comprises a second diode and a second sampling resistor, the second diode and the second sampling resistor are connected in series, and the conduction direction of the second diode is the second current direction, and the first current direction is opposite to the second current direction.

3. The current sampling circuit of claim 2, wherein, the third sampling path comprises a third diode and a third sampling resistor, the third diode and the third sampling resistor are connected in series, and the conduction direction of the third diode is the first current direction; the fourth sampling path comprises a fourth diode and a fourth sampling resistor, the fourth diode and the fourth sampling resistor are connected in series, and the conduction direction of the fourth diode is the second current direction.

4. The current sampling circuit according to claim 2, wherein the third sampling path comprises a third diode, a third sampling resistor and a fifth diode, the third diode, the third sampling resistor and the fifth diode are connected in series, and the conduction directions of the third diode and the fifth diode are the first current direction; the fourth sampling path comprises a fourth diode, a fourth sampling resistor and a sixth diode, the fourth diode, the fourth sampling resistor and the sixth diode are connected in series, and the conduction directions of the fourth diode and the sixth diode are the second current direction.

5. The current sampling circuit of claim 1, wherein, the first sampling path comprises a first diode, a first sampling resistor and a seventh diode, the first diode, the seventh diode and the first sampling resistor are connected in series, and the conduction directions of the first diode and the seventh diode are the first current direction; the second sampling path comprises a second diode, a second sampling resistor and an eighth diode, the second diode, the eighth diode and the second sampling resistor are connected in series, and the conduction directions of the second diode and the eighth diode are the second current direction, and the first current direction is opposite to the second current direction; the third sampling path comprises a third diode, a third sampling resistor and a fifth diode, the third diode, the third sampling resistor and the fifth diode are connected in series, and the conduction directions of the third diode and the fifth diode are the first current direction; The fourth sampling path comprises a fourth diode, a fourth sampling resistor and a sixth diode, which are connected in series, and the conducting directions of the fourth diode and the sixth diode are the second current direction.

6. The current sampling circuit of any of claims 1-5, wherein, The modulator comprises a first modulator and a second modulator; The first modulator is connected to the first sampling path and is configured to convert the analog signal output by the first sampling path into a first digital signal; The second modulator is connected to the second sampling path and is configured to convert the analog signal output by the second sampling path into a second digital signal.

7. The current sampling circuit of claim 6, wherein, The filter unit comprises a register configured to record the first digital signal and the second digital signal output by the first modulator and the second modulator, and subtract the first digital signal and the second digital signal recorded by the registers corresponding to the first sampling path and the second sampling path to obtain the sampling current of the first phase loop of the motor.

8. The current sampling circuit of any of claims 1-5, wherein, The modulator comprises a third modulator and a fourth modulator; The third modulator is connected to the third sampling path and is configured to convert the analog signal output by the third sampling path into a third digital signal; The fourth modulator is connected to the fourth sampling path and is configured to convert the analog signal output by the fourth sampling path into a fourth digital signal; The filter unit comprises a register configured to record the third digital signal and the fourth digital signal output by the third modulator and the fourth modulator, and subtract the third digital signal and the fourth digital signal recorded by the registers corresponding to the third sampling path and the fourth sampling path to obtain the sampling current of the second phase loop of the motor.

9. A motor control MCU, characterized by, The current sampling circuit comprises the motor control MCU and the motor.

10. An electric motor control system characterized by, The motor control MCU is connected to the motor. ​

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