A control method for a sensorless brushed DC motor

Abstract

This invention relates to the field of motor control technology and discloses a sensorless brushed DC motor control method. The method includes calculating the optimal tracking angle of the control panel and obtaining the current angle of the control panel; acquiring the current signal of the brushed DC motor through a ripple current conversion circuit, converting the current signal into a PWM pulse signal and inputting it to an MCU; the MCU counting the number of ripples per unit time and calculating the motor speed based on the number of ripples; controlling the brushed DC motor to start running based on the current angle and the optimal tracking angle of the control panel; during the operation of the brushed DC motor, calculating the optimal stopping angle based on the motor current and motor speed, while simultaneously acquiring the current angle of the control panel in real time, and controlling the brushed DC motor to stop running when the current angle of the control panel reaches the optimal stopping angle. The advantages of this invention are that it can achieve precise speed control of a brushed DC motor without sensors and effectively reduce implementation costs.

Description

Technical Field

[0001] This invention relates to the field of brushed DC motor control technology, and particularly to a control method for a sensorless brushed DC motor, which is especially suitable for controlling brushed DC motors used in photovoltaic brackets. Background Technology

[0002] Photovoltaic brackets are key components in solar photovoltaic power generation systems used to fix and support solar panels. In order to improve power generation efficiency, photovoltaic brackets need to adjust the position of solar panels in real time according to the sun's angle. This requires the drive motor (usually a brushed DC motor) to have high-precision speed control function.

[0003] To meet the requirements of high-precision speed control, some photovoltaic brackets are equipped with Hall sensors for current detection. However, due to the complex outdoor environment of photovoltaic brackets (such as temperature changes, dust interference, etc.), Hall sensors are prone to failure and have high maintenance costs. At the same time, the system needs to operate at low power for a long time, and relying on Hall sensors will increase energy consumption.

[0004] Of course, there are some sensorless control solutions in the existing technology, such as the back EMF detection method or the current ripple frequency analysis method. However, the back EMF detection method will fail at low speed or stall, and is not suitable for photovoltaic tracking scenarios with frequent start and stop. The current ripple frequency analysis method relies on FFT or complex filtering algorithms, which consumes a lot of computing resources and is difficult to implement on low-cost MCUs.

[0005] In view of the above-mentioned problems, there is an urgent need to provide a control method that can achieve precise control of the speed of a brushed DC motor without sensors, while also effectively reducing the implementation cost. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a sensorless brushed DC motor control method that enables precise speed control of the brushed DC motor without sensors, while also effectively reducing implementation costs.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A control method for a sensorless brushed DC motor, the control method comprising:

[0009] Angle Calculation: Calculates the optimal tracking angle for the panel and obtains the current angle of the panel;

[0010] Signal processing: During the operation of the brushed DC motor, the current signal of the brushed DC motor is collected through the ripple current conversion circuit, and the current signal is converted into a PWM pulse signal and input to the MCU.

[0011] Speed ​​calculation: The MCU counts the number of ripples per unit time and calculates the motor speed based on the number of ripples;

[0012] Closed-loop control of panel rotation angle: The brushed DC motor is started to run based on the current angle of the panel and the optimal tracking angle of the panel; during the operation of the brushed DC motor, the optimal stopping angle is calculated based on the motor current and motor speed, and the current angle of the panel is acquired in real time. When the current angle of the panel reaches the optimal stopping angle, the brushed DC motor is stopped to run.

[0013] Furthermore, the step of controlling the brushed DC motor to start running based on the current panel angle and the optimal tracking angle of the panel specifically includes:

[0014] Determine if the difference between the current panel angle and the optimal tracking angle is greater than or equal to a preset angle value. If so, control the brushed DC motor to start running, specifically including:

[0015] Motor startup: Start-up is performed by increasing the PWM duty cycle by 0.2% every 20ms. During startup, under light load conditions, acceleration stops when the motor speed reaches the rated speed, and the brushed DC motor runs at the rated speed. Under heavy load conditions, the PWM is controlled to continuously rise to the rated voltage of the motor, and the brushed DC motor runs at the rated voltage of the motor.

[0016] During motor operation: The PID algorithm is used to adjust the motor speed in real time, so that the brushed DC motor can operate at the rated speed or rated voltage.

[0017] If not, the brushed DC motor will not be controlled to start.

[0018] Furthermore, the calculation of the optimal stopping angle based on the motor current and motor speed specifically includes:

[0019] Calculate the maximum voltage at which the brushed DC motor stops rotating under the current load. ,in, This is the motor current. This is the internal resistance of the motor;

[0020] The PWM duty cycle that stops the brushed DC motor is calculated based on the maximum voltage at which rotation stops. ,in, It is the input voltage of the power supply;

[0021] The brushed DC motor's soft stop is achieved by decreasing the PWM duty cycle by 0.2% every 50ms, and the motor's stopping time is calculated. ,in, This indicates the PWM duty cycle of a brushed DC motor during operation.

[0022] Calculate the optimal parking angle ,in, For the optimal tracking angle of the panel, The current motor speed, This is the reduction ratio of the brushed DC motor.

[0023] Furthermore, obtaining the current angle of the panel specifically involves:

[0024] The method of segmented calibration is adopted. Calibration is performed once every set temperature value within the preset temperature range, and the calibration coefficient of each segment is written to FLASH.

[0025] The tilt angle of the photovoltaic panel is obtained by using a tilt sensor installed on the panel, and the operating temperature of the tilt sensor is obtained by using an NTC temperature sensor installed next to the tilt sensor. The obtained panel tilt angle is multiplied by a calibration coefficient under the current operating temperature to obtain the final current angle of the panel.

[0026] Furthermore, the preset temperature range is -30~70℃, and the set temperature value is 5℃.

[0027] Furthermore, the ripple current conversion circuit includes a current sampling circuit for sampling the motor operating current and converting it into a voltage signal, and a ripple voltage-PWM conversion circuit for converting the ripple voltage into a PWM pulse signal.

[0028] Furthermore, the current sampling circuit includes resistors R9, R3, R4, R12, R13, amplifier U1, resistor R5, and capacitor C3. One end of resistors R9 and R3 is connected to the power supply PWR, and the other end of resistor R9 and one end of resistor R12 is connected to a brushed DC motor. The other end of resistor R12 and one end of resistor R13 are connected to the negative input terminal of amplifier U1. The other end of resistor R3 and one end of resistor R4 are connected to the positive input terminal of amplifier U1. The other end of resistor R13 is connected to the output terminal of amplifier U1, and the other end of resistor R4 is grounded. One end of resistor R5 is connected to the output terminal of amplifier U1, and one end of capacitor C3 is connected to the other end of resistor R5. The other end of capacitor C3 is grounded. The other end of resistor R5 is also connected to the MCU.

[0029] Furthermore, the ripple voltage-PWM conversion circuit includes capacitor C2, capacitor C1, resistors R1, R6, R8, R11, capacitor C6, amplifier U2, resistors R7, R10, capacitor C5, transistor Q1, resistor R2, and capacitor C4. One end of resistor R6 is connected to the output terminal of the current sampling circuit through capacitor C2, and the other end of resistor R6 is connected to the negative input terminal of amplifier U2. One end of capacitor C1 and resistor R1 is connected to the negative input terminal of amplifier U2, and the other end of capacitor C1 and resistor R1 is connected to the output terminal of amplifier U2; resistor R8... One end of resistor R11 and capacitor C6 is connected to the positive input terminal of amplifier U2. The other end of resistor R8 is connected to power supply VCC. The other ends of resistor R11 and capacitor C6 are grounded. One end of resistor R7 is connected to the output terminal of amplifier U2. The other end of resistor R7, as well as one end of resistor R10 and capacitor C5, are connected to the base (b) terminal of transistor Q1. The other ends of resistor R10 and capacitor C5, as well as the emitter (e) terminal of transistor Q1, are grounded. The collector (c) terminal of transistor Q1 is connected to one end of resistor R2 and the MCU. The other end of resistor R2 is grounded. Capacitor C4 is connected between the collector (c) and emitter (e) terminals of transistor Q1.

[0030] Furthermore, the calculation of the optimal tracking angle of the panel specifically involves: using an astronomical algorithm to calculate the solar declination angle and hour angle based on the latitude, longitude, and time of the controller's location on the photovoltaic panel, and then calculating the optimal tracking angle of the panel based on the latitude, longitude, solar declination angle, and hour angle.

[0031] Furthermore, the MCU counts the number of ripples per unit time in the following way: the MCU first uses a dynamic time window to filter the PWM pulse signal, and then counts the number of ripples per unit time.

[0032] By adopting the above-described technical solution of the present invention, at least the following beneficial effects are achieved:

[0033] 1. During the operation of a brushed DC motor, the current signal of the brushed DC motor is collected through a ripple current conversion circuit, the current signal is converted into a PWM pulse signal and input to the MCU, and the MCU counts the number of ripples per unit time and converts it into the motor speed. Compared with the existing technology, it does not require complex spectrum analysis, which can reduce the occupation of computing resources, nor does it require the installation of Hall sensors, which can reduce maintenance costs and energy consumption, thereby effectively reducing the overall implementation cost.

[0034] 2. By calculating the optimal stopping angle based on the motor current and motor speed, and controlling the brushed DC motor to stop at the optimal stopping angle, the brushed DC motor can be controlled to stop rotating at the optimal tracking angle of the panel more precisely. This means that the speed of the brushed DC motor can be precisely controlled without sensors, thereby ensuring that the photovoltaic panel can be rotated to the optimal tracking angle of the panel more accurately during adjustment.

[0035] 3. Multiplying the panel tilt angle obtained by the tilt sensor by the calibration coefficient at the current operating temperature can effectively eliminate the temperature drift error of the tilt sensor, thereby improving the detection accuracy of the current panel angle. Attached Figure Description

[0036] Figure 1 This is a flowchart illustrating the execution process of a sensorless brushed DC motor control method according to the present invention.

[0037] Figure 2 This is a hardware principle block diagram involved in the present invention;

[0038] Figure 3 This is a detailed circuit design diagram of the ripple current conversion circuit in this invention. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Before proceeding, let me first introduce the hardware structure involved in this invention, such as... Figure 2 As shown, the overall hardware structure includes an MCU, an NTC temperature sensor, a tilt sensor, a current sampling circuit, and a ripple voltage-PWM conversion circuit. The NTC temperature sensor is electrically connected to the MCU and is used to collect the ambient temperature of the tilt sensor and transmit it to the MCU. The tilt sensor is also electrically connected to the MCU and is used to collect the panel tilt angle and transmit it to the MCU. The current sampling circuit is connected to both the MCU and the ripple voltage-PWM conversion circuit, and is used to collect the operating current of the brushed DC motor and transmit it to both the MCU and the ripple voltage-PWM conversion circuit. The ripple voltage-PWM conversion circuit converts the current signal into a PWM pulse signal and transmits it to the MCU. The MCU is used for data processing and controlling the brushed DC motor.

[0041] Please see the appendix Figure 1This invention provides a control method for a sensorless brushed DC motor, the control method comprising:

[0042] Angle Calculation: Calculates the optimal tracking angle for the panel and obtains the current angle of the panel;

[0043] Signal processing: During the operation of the brushed DC motor, the current signal of the brushed DC motor is collected through the ripple current conversion circuit, and the current signal is converted into a PWM pulse signal and input to the MCU.

[0044] Speed ​​Calculation: The MCU counts the number of ripples per unit time and calculates the motor speed based on this count. In other words, during the operation of the brushed DC motor, the motor speed is calculated by counting the number of ripples per unit time. In a specific implementation of this invention, the formula for calculating the motor speed of the brushed DC motor is as follows: The unit of motor speed is rpm (i.e., the number of revolutions per minute). The number of ripples per unit time. This represents the number of electrode pairs in a brushed DC motor. This refers to the number of commutator segments;

[0045] Closed-loop control of panel rotation angle: The brushed DC motor is started to run based on the current angle of the panel and the optimal tracking angle of the panel; during the operation of the brushed DC motor, the optimal stopping angle is calculated based on the motor current and motor speed, and the current angle of the panel is acquired in real time. When the current angle of the panel reaches the optimal stopping angle, the brushed DC motor is stopped to run.

[0046] In some embodiments of the present invention, controlling the brushed DC motor to start running based on the current panel angle and the optimal tracking angle of the panel specifically includes:

[0047] Determine if the difference between the current panel angle and the optimal tracking angle is greater than or equal to a preset angle value. If so, control the brushed DC motor to start running, specifically including:

[0048] Motor startup: Start-up is performed by increasing the PWM duty cycle by 0.2% every 20ms. During startup, under light load conditions, acceleration stops when the motor speed reaches the rated speed, and the brushed DC motor runs at the rated speed. Under heavy load conditions, the PWM is controlled to continuously increase to the motor's rated voltage, and the brushed DC motor runs at the motor's rated voltage. As a specific embodiment of the present invention, when the current of the brushed DC motor exceeds 115% of the rated current, the brushed DC motor is determined to be under heavy load; otherwise, the brushed DC motor is determined to be under light load.

[0049] During motor operation: The PID algorithm is used to adjust the motor speed in real time, so that the brushed DC motor can operate at the rated speed or rated voltage. By operating the brushed DC motor under rated conditions, better efficiency can be achieved, thereby reducing power consumption. The PID algorithm is a closed-loop control algorithm that combines proportional, integral, and derivative control elements. It is currently widely used in industrial control, temperature control, and other fields. Its core principle is to calculate the system deviation (the difference between the set value and the actual value) in real time and generate a control signal based on the weighted sum of the proportional, integral, and derivative parts to achieve fast response, eliminate steady-state error, and suppress overshoot.

[0050] If not, the brushed DC motor will not be controlled to start.

[0051] As a specific embodiment of the present invention, in order to ensure the power generation efficiency of the photovoltaic panel and avoid excessively frequent adjustments, the preset angle value is 2°; of course, the above is only a specific embodiment of the present invention, but the present invention is not limited to this, and the preset angle value can be adjusted according to actual needs in specific implementation.

[0052] This invention starts the brushed DC motor by increasing the PWM duty cycle by 0.2% every 20ms, which reduces the rapid fluctuations during the start-up process and improves the stability of the brushed DC motor. At the same time, the brushed DC motor is only started to drive the photovoltaic panel to adjust when the difference between the current angle of the panel and the optimal tracking angle of the panel is greater than or equal to a preset angle value. This can ensure the power generation efficiency of the photovoltaic panel while avoiding excessively frequent adjustments.

[0053] In some embodiments of the present invention, calculating the optimal stopping angle based on the motor current and motor speed specifically includes:

[0054] Calculate the maximum voltage at which the brushed DC motor stops rotating under the current load. ,in, This is the motor current. This is the internal resistance of the motor;

[0055] The PWM duty cycle that stops the brushed DC motor is calculated based on the maximum voltage at which rotation stops. ,in, It is the input voltage of the power supply. That is, the maximum duty cycle of a brushed DC motor when it cannot rotate;

[0056] The brushed DC motor's soft stop is achieved by decreasing the PWM duty cycle by 0.2% every 50ms. That is, when the brushed DC motor reaches the optimal stopping angle, it is controlled to stop running at a rate of 0.2% decrease in the PWM duty cycle every 50ms. The motor stopping time is then calculated. In this invention, because chopper control is used to control the speed of the brushed DC motor, different PWM duty cycles will correspond to different output voltages. This indicates the duty cycle of the control signal during the normal operation of a brushed DC motor. , It is the input voltage of the power supply;

[0057] Calculate the optimal parking angle ,in, For the optimal tracking angle of the panel, The current motor speed, This refers to the reduction ratio. The motor used in photovoltaic panels consists of three parts: a brushed DC motor, a planetary gearbox, and a rotary gear reducer. The brushed DC motor itself has low output torque but high speed. The planetary gearbox and rotary gear reducer increase the torque and reduce the output speed. The photovoltaic panel's main shaft is directly connected to the rotary gear reducer. The photovoltaic panel's rotation speed is the reduced speed. We measure the motor speed. When the brushed DC motor rotates one revolution, the photovoltaic panel's rotation angle is only [missing value]. The reduction ratio specifically refers to the speed ratio between the motor speed and the speed of the rotary output shaft.

[0058] Because brushed DC motors cannot be stopped immediately during operation due to rotational inertia and other factors, this invention calculates the optimal stopping angle based on the motor current and speed, and then controls the brushed DC motor to stop at the optimal stopping angle. This allows for more precise control of the brushed DC motor to stop rotating at the optimal tracking angle of the panel, thus ensuring that the photovoltaic panel can be rotated to the optimal tracking angle more accurately during adjustments.

[0059] In some embodiments of the present invention, obtaining the current angle of the panel specifically involves:

[0060] The method of segmented calibration is adopted. Calibration is performed once every set temperature value within the preset temperature range. The calibration coefficient of each segment is written to FLASH, which represents cache.

[0061] The tilt angle of the photovoltaic panel is obtained by using a tilt sensor installed on the panel, and the operating temperature of the tilt sensor is obtained by using an NTC temperature sensor installed next to the tilt sensor. The obtained panel tilt angle is multiplied by a calibration coefficient under the current operating temperature to obtain the final current angle of the panel.

[0062] This invention employs a segmented calibration method, multiplying the panel tilt angle obtained by the tilt sensor by a calibration coefficient at the current operating ambient temperature. This temperature compensation effectively eliminates the temperature drift error present in the tilt sensor, thereby improving the detection accuracy of the current panel angle.

[0063] As a specific embodiment of the present invention, in order to ensure the calibration effect, the preset temperature range is -30~70℃, and the set temperature value is 5℃, that is, within the range of -30~70℃, a calibration operation is performed every 5℃.

[0064] In some embodiments of the present invention, please refer to Figure 3 As shown, in order to better convert the motor operating current into a PWM pulse signal, the ripple current conversion circuit includes a current sampling circuit for sampling the motor operating current and converting it into a voltage signal, and a ripple voltage-PWM conversion circuit for converting the ripple voltage into a PWM pulse signal.

[0065] In one specific embodiment of the present invention, the current sampling circuit includes resistors R9, R3, R4, R12, R13, amplifier U1, resistor R5, and capacitor C3. One end of resistors R9 and R3 is connected to the power supply PWR, and the other end of resistor R9 and one end of resistor R12 is connected to a brushed DC motor. The other end of resistor R12 and one end of resistor R13 are connected to the negative input terminal of amplifier U1. The other end of resistor R3 and one end of resistor R4 are connected to the positive input terminal of amplifier U1. The other end of resistor R13 is connected to the output terminal of amplifier U1, and the other end of resistor R4 is grounded. One end of resistor R5 is connected to the output terminal of amplifier U1, and one end of capacitor C3 is connected to the other end of resistor R5. The other end of capacitor C3 is grounded. The other end of resistor R5 is also connected to the MCU.

[0066] In the current sampling circuit of this invention, resistor R9 has a resistance of 0.002Ω and is used to sample the motor operating current and convert it into a voltage signal. Resistors R3, R4, R12, R13, and amplifier U1 form a differential amplifier circuit with a gain of 50. This circuit amplifies the sampled current signal and inputs it to the MCU's ADC port for motor operating current detection, and amplifies the converted voltage signal and inputs it to the ripple voltage-PWM conversion circuit. Resistor R5 and capacitor C3 form a low-pass filter with a cutoff frequency of 1.5kHz. This filter is used to filter out noise signals generated by the drive pulse frequency of the motor drive circuit, i.e., to eliminate high-frequency noise.

[0067] In one specific embodiment of the present invention, the ripple voltage-PWM conversion circuit includes capacitor C2, capacitor C1, resistors R1, R6, R8, R11, capacitor C6, amplifier U2, resistors R7, R10, capacitor C5, transistor Q1, resistor R2, and capacitor C4. One end of resistor R6 is connected to the output terminal of the current sampling circuit through capacitor C2, and the other end of resistor R6 is connected to the negative input terminal of amplifier U2. One end of capacitor C1 and resistor R1 are connected to the negative input terminal of amplifier U2, and the other end of capacitor C1 and resistor R1 are connected to the output terminal of amplifier U2. One end of resistors R8, R11, and C6 is connected to the positive input terminal of amplifier U2. The other end of resistor R8 is connected to power supply VCC, and the other ends of resistors R11 and C6 are grounded. One end of resistor R7 is connected to the output terminal of amplifier U2. The other end of resistor R7, as well as one end of resistor R10 and capacitor C5, is connected to the base (b) terminal of transistor Q1. The other ends of resistor R10 and capacitor C5, as well as the emitter (e) terminal of transistor Q1, are grounded. The collector (c) terminal of transistor Q1 is connected to one end of resistor R2 and the MCU. The other end of resistor R2 is grounded. Capacitor C4 is connected between the collector (c) and emitter (e) terminals of transistor Q1.

[0068] In the ripple voltage-PWM conversion circuit of this invention, capacitor C2, resistor R6, capacitor C1, resistor R1, and amplifier U2 form an active bandpass filter circuit with a 470x amplification. Its function is to extract and amplify the current ripple signal. Capacitor C2 and resistor R6 form the high-pass filter section with a cutoff frequency of 20Hz, extracting the current ripple from the current signal sampled from the previous stage (since the current sampling circuit samples the voltage generated after the current flows through resistor R9, essentially converting current into voltage, the sampled ripple voltage is a manifestation of the current ripple). Capacitor C1 and resistor R1 form the low-pass filter section with a cutoff frequency of 2kHz. Resistors R8, R11, and capacitor C6 form a bias voltage supply circuit, providing a 0.7V bias voltage for the ripple voltage. Resistors R7 and R10, capacitor C5, transistor Q1, resistor R2, and capacitor C4 constitute the main part of the ripple voltage-PWM conversion circuit. This circuit converts the portion of the ripple voltage above a threshold to a low level and the portion below the threshold to a high level, thus generating a PWM pulse signal that is input to the MCU. Resistors R7 and R10 are used to set the threshold for ripple voltage conversion and eliminate parasitic pulse interference; capacitor C5 filters out random signal interference; resistor R2 is a pull-up resistor; and capacitor C4 filters out random interference signals.

[0069] In some embodiments of the present invention, the calculation of the optimal tracking angle of the panel specifically involves: using an astronomical algorithm to calculate the solar declination angle and hour angle based on the latitude, longitude, and time of the controller's location on the photovoltaic panel; and then calculating the optimal tracking angle of the panel based on the latitude, longitude, solar declination angle, and hour angle. It should be noted that using an astronomical algorithm to calculate the optimal tracking angle of the panel is a commonly used algorithm in the prior art; therefore, the specific calculation process of the astronomical algorithm will not be described in further detail here.

[0070] In some embodiments of the present invention, the MCU counts the number of ripples per unit time in the following ways: the MCU first uses a dynamic time window to filter the PWM pulse signal, that is, dynamically sets the minimum sampling time window according to the speed range of the brushed DC motor to eliminate parasitic pulse interference, and then counts the number of ripples (i.e., the number of square waves) per unit time.

[0071] In some embodiments of the present invention, the control method further includes:

[0072] During the operation of the brushed DC motor, it is monitored in real time whether the brushed DC motor is stalled or experiencing overcurrent. If so, the brushed DC motor is controlled to stop running; otherwise, the brushed DC motor is kept running.

[0073] After practical application, the technical solution of this invention can reduce hardware costs by 10-20% by eliminating the Hall sensor, thus having a cost advantage and being applicable to large-scale photovoltaic power plants; the speed error is less than ±2% within the range of -30℃ to 70℃, showing good environmental adaptability; the current sampling circuit can be turned off during the brushed DC motor stoppage to reduce power consumption, thus having energy-saving characteristics.

[0074] In summary, by adopting the above-described technical solution of the present invention, at least the following beneficial effects are achieved:

[0075] 1. During the operation of a brushed DC motor, the current signal of the brushed DC motor is collected through a ripple current conversion circuit, the current signal is converted into a PWM pulse signal and input to the MCU, and the MCU counts the number of ripples per unit time and converts it into the motor speed. Compared with the existing technology, it does not require complex spectrum analysis, which can reduce the occupation of computing resources, nor does it require the installation of Hall sensors, which can reduce maintenance costs and energy consumption, thereby effectively reducing the overall implementation cost.

[0076] 2. By calculating the optimal stopping angle based on the motor current and motor speed, and controlling the brushed DC motor to stop at the optimal stopping angle, the brushed DC motor can be controlled to stop rotating at the optimal tracking angle of the panel more precisely. This means that the speed of the brushed DC motor can be precisely controlled without sensors, thereby ensuring that the photovoltaic panel can be rotated to the optimal tracking angle of the panel more accurately during adjustment.

[0077] 3. Multiplying the panel tilt angle obtained by the tilt sensor by the calibration coefficient at the current operating temperature can effectively eliminate the temperature drift error of the tilt sensor, thereby improving the detection accuracy of the current panel angle.

[0078] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A control method for a sensorless brushed DC motor, characterized in that, The control method includes: Angle Calculation: Calculates the optimal tracking angle for the panel and obtains the current angle of the panel; Signal processing: During the operation of the brushed DC motor, the current signal of the brushed DC motor is collected through the ripple current conversion circuit, and the current signal is converted into a PWM pulse signal and input to the MCU. Speed ​​calculation: The MCU counts the number of ripples per unit time and calculates the motor speed based on the number of ripples; Panel rotation angle closed-loop control: The brushed DC motor is started based on the current panel angle and the optimal tracking angle. During the operation of the brushed DC motor, the optimal stopping angle is calculated based on the motor current and speed, specifically including: calculating the maximum voltage at which the brushed DC motor stops rotating under the current load. ,in, This is the motor current. Given the motor's internal resistance; calculate the PWM duty cycle that stops the brushed DC motor based on the maximum voltage at which it stops rotating. ,in, This refers to the input voltage of the power supply; the brushed DC motor's soft stop is achieved by decreasing the PWM duty cycle by 0.2% every 50ms, and the motor's stopping time is calculated. ,in, This indicates the PWM duty cycle of the brushed DC motor during operation; the optimal stopping angle is calculated. ,in, For the optimal tracking angle of the panel, The current motor speed, It is the reduction ratio of the brushed DC motor; at the same time, it acquires the current angle of the panel in real time, and controls the brushed DC motor to stop running when the current angle of the panel reaches the optimal stopping angle.

2. The control method for a sensorless brushed DC motor according to claim 1, characterized in that, The specific steps of controlling the brushed DC motor to start running based on the current angle of the panel and the optimal tracking angle of the panel include: Determine if the difference between the current panel angle and the optimal tracking angle is greater than or equal to a preset angle value. If so, control the brushed DC motor to start running, specifically including: Motor startup: Start-up is performed by increasing the PWM duty cycle by 0.2% every 20ms. During startup, under light load conditions, acceleration stops when the motor speed reaches the rated speed, and the brushed DC motor runs at the rated speed. Under heavy load conditions, the PWM is controlled to continuously rise to the rated voltage of the motor, and the brushed DC motor runs at the rated voltage of the motor. During motor operation: The PID algorithm is used to adjust the motor speed in real time, so that the brushed DC motor can operate at the rated speed or rated voltage. If not, the brushed DC motor will not be controlled to start.

3. The control method for a sensorless brushed DC motor according to claim 1, characterized in that, The specific steps for obtaining the current angle of the panel are: The method of segmented calibration is adopted. Calibration is performed once every set temperature value within the preset temperature range, and the calibration coefficient of each segment is written to FLASH. The tilt angle of the photovoltaic panel is obtained by using a tilt sensor installed on the panel, and the operating temperature of the tilt sensor is obtained by using an NTC temperature sensor installed next to the tilt sensor. The obtained panel tilt angle is multiplied by a calibration coefficient under the current operating temperature to obtain the final current angle of the panel.

4. The control method for a sensorless brushed DC motor according to claim 3, characterized in that, The preset temperature range is -30~70℃, and the set temperature value is 5℃.

5. The control method for a sensorless brushed DC motor according to claim 1, characterized in that, The ripple current conversion circuit includes a current sampling circuit for sampling the motor operating current and converting it into a voltage signal, and a ripple voltage-PWM conversion circuit for converting the ripple voltage into a PWM pulse signal.

6. The control method for a sensorless brushed DC motor according to claim 5, characterized in that, The current sampling circuit includes resistors R9, R3, R4, R12, R13, amplifier U1, resistor R5, and capacitor C3. One end of resistors R9 and R3 is connected to the power supply PWR. The other end of resistor R9 and one end of resistor R12 are connected to a brushed DC motor. The other end of resistor R12 and one end of resistor R13 are connected to the negative input terminal of amplifier U1. The other end of resistor R3 and one end of resistor R4 are connected to the positive input terminal of amplifier U1. The other end of resistor R13 is connected to the output terminal of amplifier U1, and the other end of resistor R4 is grounded. One end of resistor R5 is connected to the output terminal of amplifier U1, and one end of capacitor C3 is connected to the other end of resistor R5. The other end of capacitor C3 is grounded. The other end of resistor R5 is also connected to the MCU.

7. The control method for a sensorless brushed DC motor according to claim 5, characterized in that, The ripple voltage-PWM conversion circuit includes capacitor C2, capacitor C1, resistor R1, resistor R6, resistor R8, resistor R11, capacitor C6, amplifier U2, resistor R7, resistor R10, capacitor C5, transistor Q1, resistor R2, and capacitor C4. One end of resistor R6 is connected to the output terminal of the current sampling circuit through capacitor C2, and the other end of resistor R6 is connected to the negative input terminal of amplifier U2. One end of capacitor C1 and resistor R1 is connected to the negative input terminal of amplifier U2, and the other end of capacitor C1 and resistor R1 is connected to the output terminal of amplifier U2. Resistor R8, resistor R6, resistor R7, resistor R10, capacitor C5, transistor Q1, resistor R2, and capacitor C4 are also included. One end of resistor R11 and capacitor C6 is connected to the positive input terminal of amplifier U2. The other end of resistor R8 is connected to power supply VCC. The other ends of resistor R11 and capacitor C6 are grounded. One end of resistor R7 is connected to the output terminal of amplifier U2. The other end of resistor R7, as well as one end of resistor R10 and capacitor C5, are connected to the base (b) terminal of transistor Q1. The other ends of resistor R10 and capacitor C5, as well as the emitter (e) terminal of transistor Q1, are grounded. The collector (c) terminal of transistor Q1 is connected to one end of resistor R2 and the MCU. The other end of resistor R2 is grounded. Capacitor C4 is connected between the collector (c) and emitter (e) terminals of transistor Q1.

8. The control method for a sensorless brushed DC motor according to claim 1, characterized in that, The calculation of the optimal tracking angle of the panel is specifically as follows: using an astronomical algorithm to calculate the solar declination angle and hour angle based on the latitude, longitude, and time of the controller's location on the photovoltaic panel, and then calculating the optimal tracking angle of the panel based on the latitude, longitude, solar declination angle, and hour angle.

9. The control method for a sensorless brushed DC motor according to claim 1, characterized in that, The MCU counts the number of ripples per unit time in the following way: the MCU first uses a dynamic time window to filter the PWM pulse signal, and then counts the number of ripples per unit time.

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