Speed ​​detection and control device for series-excited motor and speed detection calculation method thereof

Abstract

The present application relates to a speed detection and control device for a series-excited motor and a speed detection calculation method thereof, belonging to the field of motor control equipment. The device includes a power supply circuit for a series motor to power the motor, a current detection module electrically connected to the power supply circuit, and used to detect the motor commutation current signal; an amplification and shaping module electrically connected to the current detection module, and used to amplify and shape the commutation current signal; a processing module, used to receive the signal of the amplification and shaping module and calculate the speed of the motor; a speed control module is provided between the processing module and the motor, and the speed control module is used to receive and respond to the control signal of the processing module to adjust the speed of the motor. The present application has the effect of realizing motor speed detection without the use of Hall elements.

Description

Technical Field

[0001] The present application relates to the field of motor control equipment, and in particular to a speed detection and control device for a series-excited motor and a speed detection and calculation method thereof. Background Art

[0002] The stator of a series-excited motor consists of a salient-pole core and field windings, while the rotor consists of a non-salient-pole core, armature windings, a commutator, and a rotating shaft. Series-excited motors are used in household appliances, such as wall breakers, meat grinders, dough mixers, soymilk makers, and egg beaters. Due to their inherent mechanical characteristics, series-excited motors operate at higher speeds when operating under light loads, i.e., when stirring small, soft ingredients. However, excessively high speeds do not significantly improve the performance of the equipment and can cause excessive noise, overflow, and other adverse effects. Therefore, series-excited motors generally operate under the control of a speed control circuit. This speed control circuit adjusts the motor speed based on the speed detection results to stabilize it within a specific, desired range.

[0003] Currently, most motor speed detection methods on the market use Hall sensors, which use the Hall sensors to sense changes in the rotor's magnetic field and then convert them into motor speed. For example, a food processor with good test results is disclosed in Chinese utility model patent publication number CN210297474U, which includes a main unit, a processing chamber, a motor and a control board disposed in the main unit, and a crushing knife disposed in the processing chamber. The motor includes a rotor and a stator sleeved on the outside of the rotor. The rotor is provided with a magnetic ring for generating a conversion magnetic field signal. The food processor preferably includes a Hall element electrically connected to the control board for sensing the magnetic field change signal, and the Hall element is arranged horizontally parallel to the magnetic ring.

[0004] The food processor in the aforementioned solution accurately detects the motor's rotational speed, enabling closed-loop speed control via a control panel. This prevents noise issues caused by excessive rotation when the material is low. Regarding the aforementioned related art, the inventors believe that the use of a Hall effect element and a magnetic ring as speed detection components requires a reserved mounting location for the Hall effect element within the motor, increasing the difficulty and cost of motor assembly. Summary of the Invention

[0005] In order to solve the assembly problem of the motor when using Hall elements to measure speed, the present application provides a speed detection and control device for a series-excited motor and a speed detection calculation method thereof.

[0006] In a first aspect, the present application provides a speed detection and control device for a series-excited motor, which adopts the following technical solution:

[0007] A speed detection and control device for a series-excited motor, comprising a power supply circuit for connecting the motor in series to supply power to the motor, and also comprising

[0008] A current detection module is electrically connected to the power supply circuit and is used to detect the motor commutation current signal;

[0009] The amplification and shaping module is electrically connected to the current detection module and is used for amplifying and shaping the commutation current signal;

[0010] A processing module, used for receiving the signal from the amplification and shaping module and calculating the speed of the motor;

[0011] A speed control module is provided between the processing module and the motor. The speed control module is used to receive and respond to a control signal from the processing module and adjust the speed of the motor.

[0012] By adopting the above technical solution, when the motor is working, the motor brushes need to be commutated differently. The current detection module is used to detect the current change generated by the motor at the moment of commutation and detect and record it. The current signal output by the current detection module is amplified and shaped by the amplification and shaping module to generate a commutation signal. The processing module calculates the motor speed based on the change period of the commutation signal and the number of motor brushes and commutators, thereby achieving the effect of motor speed detection without the help of Hall elements.

[0013] Preferably, the current detection module includes a current sampler arranged in series with the motor and a high-pass filter circuit electrically connected to the current sampler, and the high-pass filter circuit includes a first capacitor and a first resistor arranged in series, and the first capacitor is a non-polar capacitor.

[0014] By adopting the above technical solution, a current sampler is set to detect the motor current, and the low-frequency components in the current signal are filtered out by high-pass filtering, so that the high-frequency current and the brush current pulsation are synchronized, so that the cross-current signal of the commutation can be relatively clearly separated.

[0015] Preferably, the amplification and shaping module includes an amplification unit and a shaping unit, the input end of the amplification unit is connected to the output end of the current detection module, the input end of the shaping unit is connected to the output end of the amplification unit, and the output end of the shaping unit is connected to the input end of the processing module.

[0016] By adopting the above technical solution, the weak commutation current signal detected by the current detection module is amplified by the amplification unit, the waveform amplitude of the commutation voltage signal is increased, and the interference of noise on the commutation voltage signal is reduced. The sinusoidal signal is converted into a square wave signal output by the shaping unit.

[0017] Preferably, the processing module includes a timing unit and a speed calculation unit, the timing unit is used to query whether the interval time is reached, and the speed calculation unit is used to receive the voltage signal output by the amplification and shaping module and calculate the real-time speed of the motor according to the voltage signal.

[0018] By adopting the above technical solution, the speed calculation module measures the duration of the speed pulse width with the timing time of the timing unit as a reference.

[0019] Preferably, the processing module is connected to a speed control module, the input end of the speed control module is electrically connected to the output end of the processing module, and the speed control module is used to receive the control signal output by the processing module and adjust the motor speed according to the control signal; the speed control module includes a drive unit electrically connected to the processing module and a switch unit connected in series between the motor power supply circuit and the drive unit.

[0020] By adopting the above technical solution, the speed control module receives the control signal output by the processing module, and controls and adjusts the speed of the motor according to the control signal output by the processing module.

[0021] Preferably, the switch unit adopts an N-channel MOS transistor, the MOS transistor is connected in series between the power supply circuit and the power supply, and the gate of the MOS transistor is connected to the output end of the driving unit.

[0022] By adopting the above technical solution, the MOS tube receives the conduction signal of the driving unit. When the gate of the MOS tube is energized at a high level, the source and gate of the MOS tube are turned on, the motor supply voltage is reduced, and the motor speed is slowed down.

[0023] Preferably, the switch unit adopts a thyristor, the thyristor is connected in series with the power supply circuit of the motor, and the G pin of the thyristor is connected to the output end of the drive unit.

[0024] By adopting the above technical solution and utilizing the conductivity of the thyristor, the thyristor is used to receive the conduction signal of the drive unit, so that the thyristor controls the conduction of the motor under the control signal of the processing module.

[0025] Preferably, the processing module is further connected to a zero-crossing detection module, and the zero-crossing detection module is used to detect whether the alternating current passes through zero.

[0026] By adopting the above technical solution, the zero-crossing detection module is used to detect whether the AC power passes through zero, so that the processing module controls the thyristor to conduct after a certain delay when the AC power passes through zero, so as to ensure that the thyristor achieves a chopping effect.

[0027] In a second aspect, the present application provides a method for detecting and calculating the speed of a series-excited motor, which adopts the following technical solution:

[0028] A method for detecting and calculating the speed of a series-excited motor, based on any one of the above-described speed detection and control devices for a series-excited motor, comprises the following steps:

[0029] Step S1: Power on the motor and initialize the processing module;

[0030] Step S2: Determine whether the timing time of the timing unit has arrived; if not, re-check; if so, proceed to the next step;

[0031] Step S3, high and low levels are continuously accumulated;

[0032] Step S4: Determine whether the pulse is continuous; if not, refresh the speed variable in a self-adding manner, and then proceed to the next step after refreshing the speed variable; if so, proceed directly to the next step;

[0033] Step S5: determine whether the high-level / low-level time ratio is within the threshold; if so, use the moving average method to refresh the current speed variable; if not, use the interpolation method to replace the previous speed variable with the current speed variable and refresh;

[0034] Step S6: Speed ​​PID calculation set-time;

[0035] Step S7: pulse output control.

[0036] In summary, this application includes at least one of the following beneficial technical effects:

[0037] 1. By setting up a current detection module to detect the commutation current generated by the motor brush commutation, the motor speed detection effect can be achieved without the help of Hall elements;

[0038] 2. Analyze the commutation current signal detected by the current detection module by setting a processing module to prevent interference signals from adversely affecting the speed detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a block diagram of the overall structure of an embodiment of the present application;

[0040] Figure 2 This is a partial structural circuit diagram of an embodiment of the present application, which mainly shows the circuit structure of the power conversion module;

[0041] Figure 3 This is a partial structural circuit diagram of an embodiment of the present application;

[0042] Figure 4 This is a partial test waveform diagram of the embodiment of the present application;

[0043] Figure 5This is a circuit diagram of the overall structure of an embodiment of the present application, mainly showing one model of a current sampler;

[0044] Figure 6 This is a circuit diagram of the overall structure of an embodiment of the present application, mainly showing the second model of the current sampler;

[0045] Figure 7 Part of the structural circuit diagram of the embodiment of the present application mainly shows the circuit structure of the amplification and shaping module;

[0046] Figure 8 This is a partial test waveform diagram of the embodiment of the present application, which mainly shows the two detected waveform diagrams after magnification and shaping;

[0047] Figure 9 This is a partial test waveform diagram of an embodiment of the present application, mainly showing a waveform diagram of a cycle loss state;

[0048] Figure 10 This is a partial flowchart of an embodiment of the present application;

[0049] Figure 11 This is the overall structural diagram of Example 1 of the present application;

[0050] Figure 12 This is a partial structural circuit diagram of Example 1 of the present application;

[0051] Figure 13 This is the overall structural diagram of Example 2 of the present application;

[0052] Figure 14 This is a partial structural circuit diagram of Example 2 of the present application;

[0053] Figure 15 This is a partial structural circuit diagram of Example 3 of the present application.

[0054] Explanation of the accompanying drawings: 1. Power supply circuit; 11. Bridge rectifier unit; 12. Capacitor filter unit; 13. Common-mode inductor unit; 2. Current detection module; 21. Current sampler; 22. High-pass filter circuit; 3. Amplification and shaping module; 31. Amplification unit; 32. Shaping unit; 4. Processing module; 5. Speed ​​control module; 51. Drive unit; 52. Switching unit; 53. Absorption circuit; 6. Power conversion module; 7. Zero-crossing detection module. DETAILED DESCRIPTION

[0055] The following is combined with Figure 1-15 This application is described in further detail.

[0056] Existing motor speed detection usually uses a Hall system for detection, that is, detection is performed with the cooperation of Hall elements and multi-pole magnets, and then the processor is used to convert and calculate the motor speed. This speed measurement method not only requires the motor hardware production and assembly plant (department) to change the motor hardware processing, but also requires the software circuit design plant (department) to make corresponding changes to the circuit structure and program code. The existing hardware plant (department) and circuit design plant (department) are usually independent of each other. During the motor production process, the two plants (departments) need to cooperate and communicate with each other, which not only increases the communication cost, but also requires the addition of corresponding mounting molds and wires to connect the Hall elements to the processor, which not only increases the space occupied by the equipment, but also increases the production cost.

[0057] In this application, in order to more intuitively compare the detection accuracy of the present application scheme with the detection accuracy of the existing Hall system, during the test, the existing Hall system is retained, and the detection results of this device and the detection results of the Hall system are displayed in the same waveform diagram.

[0058] The embodiments of the present application disclose a speed detection and control device for a series-excited motor.

[0059] Example 1

[0060] Reference Figure 1 The speed detection and control device includes a power supply circuit 1 for connecting a series motor to power the motor operation, a current detection module 2 for detecting the motor commutation current signal VCS, and an amplification and shaping module 3 electrically connected to the current detection module 2 for current processing. The amplification and shaping module 3 is connected to a processing module 4. The processing module 4 is used to receive the signal of the amplification and shaping module 3 and calculate the speed of the motor. A speed control module 5 is provided between the processing module 4 and the motor. The speed control module 5 is used to receive and respond to the control signal of the processing module 4 and adjust the speed of the motor to ensure that the motor speed is stable within a specific required range and will not be too fast to cause problems such as excessive noise.

[0061] Reference Figure 1 The power supply circuit 1 is powered by the mains power grid and includes a bridge rectifier unit 11 and a capacitor filter unit 12 connected in parallel with the motor. The capacitor used in the capacitor filter unit 12 can be a non-polar capacitor or an electrolytic capacitor ( Figure 1(shown as an electrolytic capacitor in the figure) The mains electricity is rectified by a bridge rectifier unit 11 and output as direct current. The capacitor filter unit 12 filters the direct current output after the bridge rectifier unit 11. The direct current filtered and rectified by the capacitor filter unit 12 is used to power the motor. When the motor is working, the brushes of the motor need to be commutated at different times. At the moment of commutation, the motor current will change. The current detection module 2 detects and records the real-time change of the current. The current signal VCS1 output by the current detection module 2 is amplified and shaped by the amplification and shaping module 3 to generate a commutation current signal VCS3 output as a square wave. The processing module 4 calculates the motor speed based on the change period of the commutation signal and the number of brushes and commutators of the motor.

[0062] Reference Figures 2 to 4 The power supply circuit 1 is also connected to a power conversion module 6. In this application, the power conversion module 6 steps down the AC power to convert it into 5V and 12V power supplies, which are used to power some electrical components of the speed detection and control device. In order to facilitate the determination of the law of periodic changes in speed, voltage and current, during the test and detection process, a voltage probe for detecting the DC bus voltage signal HVDC and a current probe for detecting the bus current signal Current are provided in the power supply circuit 1 of the motor. The detection results of the Hall system, the voltage probe, and the current probe are displayed in the waveform diagram. At the same time, the detection results of this application are displayed in the waveform diagram, and the detection results of the Hall system and this application are compared.

[0063] Reference Figures 4 to 6 In order to prevent the brushes from always overlapping with the two adjacent magnetic poles of the commutator when passing through the two magnetic poles of the commutator, thereby causing the commutation current generated by the brushes to be continuous, the current detection module 2 includes a current sampler 21 arranged in series with the motor and a high-pass filter circuit 22 electrically connected to the current sampler 21. In the present application, the current sampler 21 can be a voltage divider resistor RF or a transformer. When the current sampler 21 is a voltage divider resistor RF, the input end of the high-pass filter circuit 22 is electrically connected between the voltage divider resistor RF and the motor; when the current sampler 21 is a current transformer TA, the primary winding of the current transformer TA is connected in series with the power supply circuit 1 of the motor, and one end of the secondary winding of the current transformer TA is grounded and the other end is connected to the high-pass filter circuit 22. Since the current sampler 21 is connected in series with the motor, the current detection module 2 can detect the motor current through the current sampler 21, and at the same time filter out the low-frequency component (AC fundamental wave part) in the current signal through the high-pass filter circuit 22, so as to achieve synchronization of the high-frequency current and the brush current pulsation, so that the cross-current signal of the commutation can be relatively clearly separated.

[0064] Reference Figure 7 and Figure 8In this application, in order to better reduce the cost of motor improvement, the current sampler 21 uses a voltage divider resistor RF, and the high-pass filter circuit 22 uses a differential circuit formed by a first capacitor C1 and a first resistor R1 connected in series, wherein the first capacitor C1 is a non-polar capacitor, and one end of the first capacitor C1 is electrically connected to the wire between the voltage divider resistor RF and the motor, and the other end of the first capacitor C1 is electrically connected to one end of the first resistor R1, and the first resistor R1 is grounded at one end away from the first capacitor C1; the commutation current signal is coupled through the first capacitor C1 to generate a corresponding voltage signal. The input end of the amplification and shaping module 3 is electrically connected between the first capacitor C1 and the first resistor R1, and the amplification and shaping module 3 amplifies and rectifies the commutation voltage signal output by the current detection module 2 and obtains a voltage signal that meets the quality requirements.

[0065] Reference Figure 7 The amplification and shaping module 3 includes an amplification unit 31 connected to the output end of the current detection module 2 and a shaping unit 32 connected to the output end of the amplification unit 31. In this application, the amplification unit 31 includes an operational amplifier N1 whose positive input end is connected to the output end of the current detection module 2 and a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a second capacitor C2 electrically connected to the operational amplifier N1, wherein the second resistor R2 is connected in series between the power supply and the positive input end of the operational amplifier N1 to bias the input static voltage to a non-zero initial value voltage, the third resistor R3 and the second capacitor C2 are connected in series between the reverse input end of the operational amplifier N1 and the ground, and the second capacitor C2 is a non-polar capacitor, the fourth resistor R4 is connected in series between the output end and the negative input end of the operational amplifier N1, and the fifth resistor R5 is connected in series between the output end of the operational amplifier N1 and the input end of the shaping unit 32. The amplifying unit 31 is a non-inverting amplifier, which amplifies the weak commutation current signal detected by the current detection module 2, thereby increasing the waveform amplitude of the commutation voltage signal and reducing the interference of noise on the commutation voltage signal.

[0066] Reference Figure 7 The shaping unit 32 converts the voltage signal into a corresponding level signal, that is, converts the sinusoidal signal into a square wave signal for output. In the present application, the shaping unit 32 includes a comparator N2 and a sixth resistor R6 and a seventh resistor R7 electrically connected to the comparator N2. The sixth resistor R6 and the seventh resistor R7 are connected in series between the power supply and the ground, and the connection node between the sixth resistor R6 and the seventh resistor R7 is connected to the reverse input end of the comparator N2 to form a reference circuit of the reverse input end of the comparator N2. The positive input end of the comparator N2 is connected to the output end of the amplification unit 31, and the output end of the comparator N2 is connected to the processing module 4.

[0067] Reference Figure 7 and Figure 9During the test, it was discovered that the commutation signal detected by current detection module 2 contained disturbances, resulting in a certain inconsistency in the pulse width of the voltage signal output by current detection module 2. Furthermore, the voltage signal occasionally exhibited insufficient pulse amplitude, leading to periodic loss in the level signal output by amplification and shaping module 3. To address this periodic loss, processing module 4 inserted compensation into the level signal output by amplification and shaping module 3 based on the pattern of periodic loss, ensuring the periodic integrity of the test results.

[0068] Reference Figure 10 and Figure 11 The processing module 4 includes a timing unit and a speed calculation unit. The timing unit is used to check whether the interval time has been reached to ensure that the interval time between two executions is equal. The speed calculation unit is used to receive the voltage signal output by the amplification and shaping module 3 and calculate the real-time speed of the motor based on the voltage signal. The calculation of the motor speed mainly includes the following steps:

[0069] Step S1: Power on the motor and initialize the processing module 4;

[0070] Step S2: Determine whether the timing time of the timing unit has arrived; if not, re-check; if so, proceed to the next step;

[0071] Step S3, high and low levels are accumulated continuously; during the timing time of the timing unit, the number of high levels and the number of low levels are accumulated respectively, and at each rising edge, the number of high levels and the number of low levels are summed to obtain the period T;

[0072] Step S4: Determine whether the pulse is continuous; if not, refresh the speed variable in a self-adding manner, and then proceed to the next step after refreshing the speed variable; if so, proceed directly to the next step;

[0073] Step S5: determine whether the high-level / low-level time ratio is within the threshold; if so, use the moving average method to refresh the current speed variable; if not, use the interpolation method to replace the previous speed variable with the current speed variable and refresh;

[0074] Step S6: Speed ​​PID calculation set-time;

[0075] Step S7, pulse output control; the pulse is controlled according to the set-time value so that the speed of the motor is adjusted accordingly, and the processing module 4 restarts the speed calculation.

[0076] Specifically, after the motor is powered on, processing module 4 begins initialization, which includes initializing the MCU system, IO pin levels, software UART, and PID functions. After successful initialization, the timing unit determines whether its set time has arrived. If not, it returns to recheck whether the set time has arrived. If so, it accumulates the number of high and low level times. Within the timing unit's set time, the number of high and low level times are accumulated, respectively, and the sum of the high and low level times is calculated at each rising edge to obtain the period T. Next, it checks whether the pulse is continuous, that is, whether the period T increases indefinitely. If the pulse is detected to be discontinuous, it indicates that there is a period loss phenomenon, and processing module 4 needs to insert compensation for the period, that is, refresh the speed variable in a self-adding manner, and then proceed to the next step. If the detected pulse is continuous, it proceeds directly to the next step. The next step is to determine whether the high and low level time ratios are within a threshold value. Under normal circumstances, the high and low level time ratios are within 1.5, that is, the threshold value is 1.5. If the high and low level times differ too much, that is, the high and low level time ratios are not within the threshold value, then this detection result is discarded, and the previous detection result is inserted into this detection result using interpolation. If the high and low level time ratios are within the threshold value, the current speed variable is refreshed with this detection result. After the speed detection is completed, the speed PID calculation set-time is performed, and the processing module 4 performs duty cycle control according to the value of the set-time, thereby controlling the pulse output.

[0077] Reference Figure 11 and Figure 12 The processing module 4 is connected to a speed control module 5 for adjusting the motor speed. The input end of the speed control module 5 is electrically connected to the output end of the processing module 4 for receiving the control signal output by the processing module 4. The speed control module 5 includes a drive unit 51 electrically connected to the processing module 4 and a switch unit 52 connected in series between the motor power supply circuit 1 and the drive unit 51. The drive unit can be an optocoupler element or a totem pole drive device. In this application, the drive unit 51 is an optocoupler element including a light transmitter and a light receiver. Figure 12 The light emitter is a light emitting diode (LED), and the light receiver is a phototransistor (Q). The light emitter is connected in series between the output terminal of the processing module 4 and the ground, and the light receiver is connected in series between the power supply and the power supply circuit 1. The light sensing end of the light receiver faces the light emitter and is used to receive the light emitted by the light emitter. In this application, the switch unit 52 is an enhanced N-channel MOS transistor, and the gate of the MOS transistor is connected to the output terminal of the light receiver, the drain of the MOS transistor is connected to the bridge rectifier unit 11, and the source of the MOS transistor is connected to the motor. When the processing module 4 detects and analyzes that the motor speed is too high, the processing module 4 outputs a control signal to turn on the drive unit 51. At this time, the gate of the MOS transistor is energized at a high level, the source and gate of the MOS transistor are turned on, the power supply voltage of the motor is reduced, and the speed of the motor is slowed down.

[0078] The implementation principle of the speed detection and control device of a series-excited motor in an embodiment of the present application is as follows: when the relationship between the brush and the commutator of the motor is determined, the number of changes in the commutation current generated by the commutation during the rotation of the brush is fixed during one rotation of the motor, and the speed of the motor is obtained by obtaining the change cycle of the commutation current. The speed of the motor is measured by the brush, and the interference signal in the measurement process is processed and replaced by the processing module 4 to ensure that the measurement of the motor speed is not affected by the interference signal. The motor speed is analyzed and calculated by the processing module 4. When the processing module 4 measures that the motor speed is too large, the control signal is output by adjusting the duty cycle of the PWM, so that the control unit receives the corresponding control signal to adjust the speed of the motor. Each module in the present application can adopt a discrete electrical connection structure or an integrated circuit connection structure.

[0079] Example 2

[0080] Reference Figure 13 and Figure 14 This embodiment differs from Embodiment 1 in that the switch unit 52 is a thyristor (SCR). In this application, the thyristor (SCR) is a bidirectional thyristor (BTS) connected in series to the mains power grid. The G pin of the thyristor (SCR) is connected to the output of the drive unit 51, and an NPN transistor is provided between the thyristor (SCR) and the drive unit 51. The control electrode of the transistor is connected to the output of the optical receiver, the collector of the transistor is connected to the power supply circuit 1 of the motor, the emitter of the transistor is grounded, and the G pin of the thyristor (SCR) is connected to the collector of the transistor, so that the thyristor (SCR) controls the conduction of the motor in response to the control signal output by the processing module 4.

[0081] Reference Figure 13 and Figure 14 To prevent the generation of a large number of high-order harmonics during the speed regulation process, processing module 4 is further connected to a zero-crossing detection module 7. This zero-crossing detection module 7 includes a switching element connected to the input of processing module 4. The switching element is an NPN transistor. The collector of the transistor is connected to the signal input of processing module 4, the control electrode of the transistor is connected to the mains power grid, and the emitter of the transistor is grounded. Zero-crossing detection module 7 is used to detect whether the AC power crosses zero, so that processing module 4 can control the thyristor (SCR) to conduct after a certain delay when the AC power crosses zero.

[0082] Example 3

[0083] Reference Figure 15The difference between this embodiment and embodiment 2 is that the motor is powered by alternating current, and the power supply circuit 1 includes a common-mode inductor unit 13 and a capacitor filter unit 12 arranged in parallel with the motor. The common-mode inductor unit 13 uses the isotropic nature of the common-mode current to make the coil exhibit high impedance, thereby generating a strong damping effect, thereby attenuating the common-mode current and achieving a filtering effect.

[0084] A thyristor (SCR) is connected in series between the motor and the current sampler. In this application, the SCR is a bidirectional thyristor, and its G pin is connected to the drive unit 51. The SCR's ability to alternately conduct and shut down in two directions is utilized to adjust and control the motor speed. An absorption circuit is connected in parallel across the SCR. The absorption circuit includes a third capacitor and an eighth resistor connected in series. This RC absorption circuit absorbs the induced voltage, thereby protecting the thyristor.

[0085] This application also discloses a motor speed detection calculation method, referring to Figure 10 , the calculation of motor speed mainly includes the following steps:

[0086] Step S1: Power on the motor and initialize the processing module 4;

[0087] Step S2: Determine whether the timing time of the timing unit has arrived; if not, re-check; if so, proceed to the next step;

[0088] Step S3, high and low levels are accumulated continuously; during the timing time of the timing unit, the number of high levels and the number of low levels are accumulated respectively, and at each rising edge, the number of high levels and the number of low levels are summed to obtain the period T;

[0089] Step S4: Determine whether the pulse is continuous; if not, refresh the speed variable in a self-adding manner, and then proceed to the next step after refreshing the speed variable; if so, proceed directly to the next step;

[0090] Step S5: determine whether the high-level / low-level time ratio is within the threshold; if so, use the moving average method to refresh the current speed variable; if not, use the interpolation method to replace the previous speed variable with the current speed variable and refresh;

[0091] Step S6: Speed ​​PID calculation set-time;

[0092] Step S7, pulse output control; the pulse is controlled according to the set-time value so that the speed of the motor is adjusted accordingly, and the processing module 4 restarts the speed calculation.

[0093] Specifically, after the motor is powered on, processing module 4 begins initialization, which includes initializing the MCU system, IO pin levels, software UART, and PID functions. After successful initialization, the timing unit determines whether its set time has arrived. If not, it returns to recheck whether the set time has arrived. If so, it accumulates the number of high and low level times. Within the timing unit's set time, the number of high and low level times are accumulated, respectively, and the sum of the high and low level times is calculated at each rising edge to obtain the period T. Next, it checks whether the pulse is continuous, that is, whether the period T increases indefinitely. If the pulse is detected to be discontinuous, it indicates that there is a period loss phenomenon, and processing module 4 needs to insert compensation for the period, that is, refresh the speed variable in a self-adding manner, and then proceed to the next step. If the detected pulse is continuous, it proceeds directly to the next step. The next step is to determine whether the high and low level time ratios are within a threshold value. Under normal circumstances, the high and low level time ratios are within 1.5, that is, the threshold value is 1.5. If the high and low level times differ too much, that is, the high and low level time ratios are not within the threshold value, then this detection result is discarded, and the previous detection result is inserted into this detection result using interpolation. If the high and low level time ratios are within the threshold value, the current speed variable is refreshed with this detection result. After the speed detection is completed, the speed PID calculation set-time is performed, and the processing module 4 performs duty cycle control according to the value of the set-time, thereby controlling the pulse output.

[0094] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A speed detection and control device for a series-excited motor, comprising a power supply circuit (1) for supplying power to the motor in series, characterized in that: Also includes A current detection module (2) is electrically connected to the power supply circuit (1) and is used to detect a motor commutation current signal; an amplification and shaping module (3), electrically connected to the current detection module (2), and used for amplifying and shaping the commutation current signal; a processing module (4), configured to receive the signal from the amplification and shaping module (3) and calculate the rotational speed of the motor; A speed control module (5) is provided between the processing module (4) and the motor, and the speed control module (5) is used to receive and respond to the control signal of the processing module (4) to adjust the speed of the motor. The processing module (4) includes a timing unit and a speed calculation unit. The timing unit is used to query whether the interval time has been reached. The speed calculation unit is used to receive the voltage signal output by the amplification and shaping module (3) and calculate the real-time speed of the motor based on the voltage signal. The processing module (4) is connected to a speed control module (5), an input end of the speed control module (5) is electrically connected to an output end of the processing module (4), and the speed control module (5) is used to receive a control signal output by the processing module (4) and adjust the motor speed according to the control signal; the speed control module (5) includes a drive unit (51) electrically connected to the processing module (4) and a switch unit (52) connected in series between the motor power supply circuit (1) and the drive unit (51), The processing module (4) is used to calculate the real-time rotation speed according to the period of the square wave signal, and when a period loss is detected, it is judged whether the high-level and low-level time ratio exceeds a threshold value of 1.

5. If the difference between the high-level and low-level time is too large, that is, the high-level and low-level time ratio is not within the threshold, the current detection result is discarded, and the previous detection result is inserted into the current detection result by using an interpolation method; If the high and low level time ratio is within the threshold, the current speed variable is refreshed with the detection result. The current detection module (2) comprises a current sampler (21) arranged in series with the motor and a high-pass filter circuit (22) electrically connected to the current sampler (21), wherein the high-pass filter circuit (22) comprises a first capacitor and a first resistor arranged in series, wherein the first capacitor is a non-polar capacitor, and the high-pass filter circuit (22) is used to filter out low-frequency components and separate the commutation current signal. The processing module (4) is further connected to a zero-crossing detection module (7), which is used to detect whether the alternating current passes through zero. The zero-crossing detection module (7) comprises a switch element connected to the input end of the processing module (4), wherein the switch element is an NPN-type transistor, the collector of the transistor is connected to the signal input end of the processing module (4), the control electrode of the transistor is connected to the mains power grid, and the emitter of the transistor is grounded.

2. The speed detection and control device for a series-excited motor according to claim 1, characterized in that: The amplification and shaping module (3) comprises an amplification unit (31) and a shaping unit (32), wherein the input end of the amplification unit (31) is connected to the output end of the current detection module (2), the input end of the shaping unit (32) is connected to the output end of the amplification unit (31), and the output end of the shaping unit (32) is connected to the input end of the processing module (4).

3. The speed detection and control device for a series-excited motor according to claim 1, characterized in that: The switch unit (52) uses an N-channel MOS transistor, which is connected in series between the power supply circuit (1) and the power supply, and the gate of the MOS transistor is connected to the output end of the drive unit (51).

4. The speed detection and control device for a series-excited motor according to claim 1, characterized in that: The switch unit (52) adopts a thyristor, the thyristor is connected in series with the power supply circuit (1) of the motor, and the G pin of the thyristor is connected to the output end of the drive unit (51).

5. A method for detecting and calculating the rotational speed of a series-excited motor, based on the rotational speed detection and control device for a series-excited motor according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step S1, power on the motor and initialize the processing module (4); Step S2: determine whether the timing time of the timing unit has arrived; If not, retest, if yes, proceed to the next step; Step S3, high and low levels are continuously accumulated; Step S4: Determine whether the pulse is continuous; if not, refresh the speed variable in a self-adding manner, and then proceed to the next step after refreshing the speed variable; if so, proceed directly to the next step; Step S5: determine whether the high-level / low-level time ratio is within the threshold; if so, use the moving average method to refresh the current speed variable; if not, use the interpolation method to replace the previous speed variable with the current speed variable and refresh; Step S6: Speed ​​PID calculation set-time; Step S7: pulse output control.

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