Low-voltage motor based on segmented threshold PWM control

Abstract

The application relates to the technical field of motor control, and discloses a low-voltage motor based on segmented threshold PWM control, which comprises a motor shell, a motor tail cover arranged at the tail of the motor shell, a control circuit board arranged at the middle of the motor tail cover, a device assembly arranged on the surface of the control circuit board, wherein the device assembly comprises a microcontroller arranged on the surface of the control circuit board, the microcontroller is internally provided with a control system, and the device assembly further comprises a PWM signal input unit, a power input and filtering unit, a voltage reduction and stabilization unit, a reverse electromotive force and voltage sampling unit, a motor power driving unit, a current sampling unit and a temperature detection unit arranged on the surface of the control circuit board. The application utilizes segmented threshold control, closed-loop speed regulation architecture and dynamic threshold reconstruction logic to realize shielding of instruction jitter and accurate speed regulation, and the current determination boundary is reconstructed in real time through the speed deviation and the running state, so that the transient response capability of the motor and the hardware safety and reliability under all working conditions are considered.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, specifically to a low-voltage motor based on segmented threshold PWM control. Background Technology

[0002] Low-voltage motors typically use pulse width modulation (PWM) signals to regulate speed. In conventional control schemes, the system's parsing of external commands and the underlying protection logic often follow a preset, fixed path.

[0003] In complex electromagnetic environments, externally input control signals are easily interfered with near the start-stop critical point, causing the motor to switch frequently and unstablely at the turn-off and start-up edges, increasing the electrical stress on the drive circuit and affecting the motor's operational stability.

[0004] Furthermore, existing speed control logic and safety monitoring mechanisms typically operate independently, lacking real-time information exchange between them. Regarding safety protection, since overcurrent protection thresholds are often set to fixed values, conflicts arise when the system handles dynamic adjustment demands. When a low-voltage motor needs to output a large current for short-term dynamic compensation to respond to transient commands or overcome sudden load increases, static protection boundaries are prone to falsely triggering safety shutdown.

[0005] Conversely, if the fixed threshold is increased in order to meet the power response requirements, the motor may not be able to effectively identify abnormal temperature rises caused by invalid pulses when operating at low speeds at the start-stop critical point, which increases the risk of device damage. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a low-voltage motor based on segmented threshold PWM control, which solves the problems of unstable start-stop boundary switching, independent speed regulation and protection logic, and the inability of static safety thresholds to balance dynamic response and thermal safety protection in existing low-voltage motors.

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

[0008] The present invention provides a low-voltage motor based on segmented threshold PWM control, including a motor housing, a motor tail cover at the rear of the motor housing, a control circuit board mounted in the middle of the motor tail cover, and a device assembly on the surface of the control circuit board.

[0009] The device assembly includes a microcontroller, a PWM signal input unit, a power input and filtering unit, a buck regulator unit, a back electromotive force and voltage sampling unit, a motor power drive unit, a current sampling unit, and a temperature detection unit mounted on the control circuit board. The microcontroller has a built-in control system, which is used to receive external control commands and perform closed-loop regulation and safety monitoring of the operating status and speed of the low-voltage motor.

[0010] Preferably, the control system includes:

[0011] The power management module is used to receive external power through the power input and filtering unit and call the buck regulator unit to convert the external power into a stable low-voltage logic voltage.

[0012] The instruction acquisition module is used to capture the external control instruction using the PWM signal input unit and parse the external control instruction to generate the input duty cycle;

[0013] The status determination module is used to receive the input duty cycle, process it through multi-level safety threshold determination logic, and determine the current macroscopic operating status.

[0014] The speed calculation module is used to determine when the macroscopic operating state is a valid operating command. If the input duty cycle is in the preset linear speed regulation range, the target speed is calculated by calling the speed mapping formula. If the input duty cycle is in the preset limit output range, the target speed is directly locked to the maximum rated operating speed of the motor.

[0015] The closed-loop control module is used to receive the target speed, obtain the actual operating speed of the low-voltage motor using the back electromotive force and voltage sampling unit, extract the compensation amount of the numerical deviation between the actual operating speed and the target speed, perform algebraic summation to generate a dynamic compensation duty cycle, and superimpose the dynamic compensation duty cycle to generate an output PWM drive duty cycle, which is then transmitted to the motor power drive unit.

[0016] The preset linear speed regulation range and the preset limit output range are preset based on the speed regulation conditions of the low-voltage motor.

[0017] Preferably, the power management module is specifically used for:

[0018] The external power supply is protected against polarity issues by using the reverse connection protection circuit of the power input and filtering unit, and noise is filtered out by using the filter capacitor array and transient voltage suppressor.

[0019] The conversion is performed using a low-dropout linear regulator or synchronous buck converter integrated within the buck regulator unit, and the on-time of the power transistor is dynamically adjusted through a closed-loop feedback loop to output a constant, stable low-voltage logic voltage.

[0020] Preferably, the multi-level security threshold determination logic of the state determination module is specifically as follows:

[0021] When the input duty cycle is less than the shutdown threshold, a stop command is generated and determined as the macroscopic operating state. A zero duty cycle signal is output to the motor power drive unit to force the low-voltage motor to stop.

[0022] When the input duty cycle is in the range of being greater than or equal to the shutdown threshold and less than the startup threshold, a determination to maintain the current start-stop mode is generated and used as the macroscopic operating state.

[0023] When the input duty cycle is greater than or equal to the start threshold, a determination of the valid running instruction is generated and used as the macroscopic running state;

[0024] The shutdown threshold and the start threshold are preset based on the operating state switching conditions of the low-voltage motor.

[0025] Preferably, the control system further includes a safety monitoring module, which is used for:

[0026] The current sampling unit is used to read the analog voltage signal reflecting the load state of the low-voltage motor in real time, and the temperature detection unit is used to obtain the physical resistance signal reflecting the physical temperature rise of the power device area in real time.

[0027] When the detected analog voltage signal is greater than the overcurrent safety threshold, or the physical resistance signal is greater than or equal to the safety critical point, a safety blocking is generated to cut off the motor power drive unit.

[0028] The overcurrent safety threshold and the safety critical point are preset based on the hardware safety protection parameters of the low-voltage motor.

[0029] Preferably, the control system further includes a dynamic threshold reconstruction module, which is used to receive the numerical deviation and the macroscopic operating status;

[0030] Using dynamic safety threshold reconstruction logic, a threshold expansion coefficient is calculated in real time based on the absolute value of the numerical deviation.

[0031] The reference overcurrent threshold is multiplied by the threshold expansion coefficient to generate a dynamic overcurrent safety threshold in real time, and the dynamic overcurrent safety threshold is synchronized to the safety monitoring module to replace the original overcurrent safety threshold.

[0032] The reference overcurrent threshold is preset based on the rated current parameters of the low-voltage motor.

[0033] Preferably, the specific logic for the dynamic threshold reconstruction module to generate the threshold expansion coefficient using the dynamic security threshold reconstruction logic is as follows:

[0034] Extract the absolute value of the numerical deviation and determine whether it exceeds the steady-state error tolerance:

[0035] If the absolute value of the numerical deviation is less than or equal to the steady-state error tolerance, then the threshold expansion coefficient is set to the base value;

[0036] If the absolute value of the numerical deviation is greater than the steady-state error tolerance, then the excess difference between the absolute value of the numerical deviation and the steady-state error tolerance is calculated, and the excess difference is multiplied by a preset proportional gain constant and then added to the base value to obtain the expansion coefficient calculation value.

[0037] The calculated value of the expansion coefficient is compared with the maximum expansion coefficient limit value. If the calculated value of the expansion coefficient is greater than the maximum expansion coefficient limit value, the maximum expansion coefficient limit value is used as the final threshold expansion coefficient; otherwise, the calculated value of the expansion coefficient is used as the final threshold expansion coefficient.

[0038] The steady-state error tolerance, the base value, the proportional gain constant, and the maximum expansion coefficient limit are preset based on the dynamic response requirements of the low-voltage motor.

[0039] Preferably, the dynamic threshold reconstruction module is further configured to forcibly lock the threshold expansion coefficient to the base value when the state determination module determines that the macroscopic operating state is to maintain the current start-stop mode.

[0040] This invention provides a low-voltage motor based on segmented threshold PWM control. It has the following advantages:

[0041] 1. This invention segments the input duty cycle using multi-level safety threshold judgment logic, establishing a state maintenance interval between the shutdown threshold and the start threshold. This mechanism effectively shields critical fluctuations in the input signal, avoiding frequent start-stop phenomena caused by command jitter at the start-stop boundary of the low-voltage motor, and improving the stability of motor operating state switching.

[0042] 2. This invention utilizes a closed-loop control module combined with a speed mapping formula to calculate the actual operating speed by extracting the back electromotive force and performing algebraic summation compensation, thereby achieving tracking of the target speed. At the same time, it combines a safety monitoring module to read the analog voltage signal and physical resistance signal in real time, triggering a safety interruption under overcurrent or overtemperature conditions to cut off the motor power drive unit, thus achieving synergy between speed control and underlying hardware safety protection.

[0043] 3. This invention establishes a feedforward elastic protection and cross-interlock mechanism based on real-time operating condition perception between closed-loop regulation and underlying safety monitoring by setting a dynamic threshold reconstruction module. When a sudden external load or rapid acceleration command causes a sharp increase in numerical deviation, the module actively and temporarily raises the underlying current judgment boundary, allowing short-term high-current dynamic compensation output to improve dynamic response capability and avoid false triggering of safety blocking. At the same time, when the status judgment module determines that the macroscopic operating state is to maintain the current start-stop mode, the module forcibly locks the threshold expansion coefficient to the base value, making the current judgment boundary unconditionally tighten, thereby preventing the low-voltage motor from causing abnormal hardware heating due to ineffective high-frequency excitation pulses when creeping at low speed at the start-stop critical point. Attached Figure Description

[0044] Figure 1 This is a three-dimensional schematic diagram of the present invention;

[0045] Figure 2 This is an exploded view of the low-voltage motor of the present invention;

[0046] Figure 3 This is a schematic diagram of the control system architecture of the present invention;

[0047] Figure 4 This is a circuit diagram of the three-phase inverter bridge power drive and current sampling circuit of the present invention;

[0048] Figure 5 This is a diagram of the microcontroller core and its signal logic distribution circuit of the present invention;

[0049] Figure 6 This is a circuit diagram of the power device temperature monitoring and sampling circuit of the present invention;

[0050] Figure 7 This is a circuit diagram of the external command capture and signal conditioning circuit of the present invention;

[0051] Figure 8 This is a circuit diagram of the power supply bus voltage sampling circuit of the present invention;

[0052] Figure 9 This is a circuit diagram of the power input surge protection and energy storage filter of the present invention;

[0053] Figure 10 This is a circuit diagram for sampling and filtering the back electromotive force of a motor according to the present invention.

[0054] The components include: 1. Motor housing; 2. Motor tail cover; 3. Control circuit board. Detailed Implementation

[0055] 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.

[0056] Please see the appendix Figure 1 and attached Figure 2 This invention provides a low-voltage motor based on segmented threshold PWM control, including a motor housing 1, a motor tail cover 2 at the rear of the motor housing 1, a control circuit board 3 mounted in the middle of the motor tail cover 2, and a device assembly on the surface of the control circuit board 3, including a microcontroller mounted on the surface of the control circuit board 3. The microcontroller has a built-in control system, which is used to receive external control commands and perform closed-loop regulation and safety monitoring of the operating status and speed of the low-voltage motor.

[0057] The device assembly also includes a PWM signal input unit, a power input and filtering unit, a buck regulator unit, a back electromotive force and voltage sampling unit, a motor power drive unit, a current sampling unit, and a temperature detection unit mounted on the control circuit board 3.

[0058] The motor tail cover 2 is set around the control circuit board 3 as a cover, and the side wall of the motor tail cover 2 has an exhaust vent to facilitate the discharge of the heat exchanged airflow.

[0059] See appendix Figure 4 -Appendix Figure 10 In order to achieve highly integrated control logic, the control circuit board 3 has the above-mentioned functional units distributed on its surface.

[0060] The microcontroller, as the core computing entity, is used to execute various instructions of the closed-loop speed control system;

[0061] The PWM signal input unit includes terminals and an RC filter network, and is mainly responsible for receiving external control commands.

[0062] The power input and filtering unit includes a power input terminal, a reverse connection protection diode, and a filter capacitor. It is responsible for power supply reception and noise filtering. Together with the buck regulator unit, which includes a buck regulator chip and surrounding capacitors, it provides a relatively stable low-voltage power supply for logic devices.

[0063] The reverse electromotive force and voltage sampling unit includes a voltage divider resistor and capacitor network for extracting signals from the stator coils;

[0064] The motor power drive unit includes power MOSFETs arranged in a ring, designed to execute commands from the control system to form a three-phase inverter bridge that drives the motor coils;

[0065] The current sampling unit includes a current sensing chip resistor and supporting circuitry, which can realize closed-loop current monitoring of the system.

[0066] The temperature detection unit is typically composed of a thermistor and is used to sense the physical temperature of the motor power drive unit area.

[0067] Specifically, Figure 4 The circuit corresponds to the aforementioned motor power drive unit and current sampling unit. It includes a three-phase inverter bridge composed of multiple power MOSFETs (Q1-Q6) and a current sensing resistor (RS1) connected in series in the loop for acquiring phase current. This circuit is used to receive PWM drive commands from the microcontroller to drive the motor and to feed back analog voltage signals reflecting the motor load status to the microcontroller in real time, thereby realizing closed-loop current monitoring and overcurrent safety blocking of the system.

[0068] Figure 5 The circuit is based on a microcontroller chip (such as LKS32MC034) and integrates a buck regulator circuit consisting of a voltage regulator chip (U5) and its surrounding capacitors. It is used to receive various analog and digital signals from the external sampling circuit, execute segmented threshold PWM control logic and closed-loop speed regulation calculation, and distribute the calculated output PWM drive duty cycle and other instructions to various functional pins.

[0069] Figure 6 The circuit corresponds to the aforementioned temperature detection unit, and its core is equipped with a negative temperature coefficient thermistor (NTC) and matching voltage divider resistors (R30) and filter capacitors (C21). This circuit is used to sense the physical temperature changes in the motor power drive unit area in real time and convert them into physical resistance signals, which are then fed back to the microcontroller's safety monitoring module to provide a basis for over-temperature safety protection.

[0070] Figure 7 The circuit corresponding to the aforementioned PWM signal input unit utilizes a transistor (Q7) and an RC network to perform level conversion and noise reduction on the externally input PWM signal. This circuit is used to convert externally issued control commands into transition signals that the microcontroller can stably recognize, ensuring the accuracy of the subsequent level transition period analysis and input duty cycle calculation by the command acquisition module.

[0071] Figure 8The circuit utilizes a voltage divider resistor network (R31, R32) to proportionally attenuate the externally supplied bus voltage (BAT). This circuit provides a real-time bus voltage reference for the microcontroller, enabling the closed-loop regulation module to capture voltage zero crossings or perform relevant compensation calculations with accurate voltage parameters.

[0072] Figure 9 The circuit corresponds to the front-end protection section of the power input and filtering unit mentioned above, using a transient voltage suppression diode (D4) and a large-capacity filter electrolytic capacitor (C4) connected in parallel. This circuit is used to filter out high-frequency noise and transient surge voltages at the external power input terminal and buffer energy, improving the purity and electrical reliability of the overall system input voltage.

[0073] Figure 10 The circuit corresponds to the aforementioned reverse electromotive force and voltage sampling unit. Signal links are drawn from the U, V, and W phase terminals of the motor, respectively, and filtered through a resistor divider (R27-R29) and capacitor (C11-C13) network. This circuit is used to extract the residual voltage of the unconducted phase in the stator coil and send it to the microcontroller to assist the control system in capturing the voltage zero-crossing point to calculate the actual operating speed of the motor.

[0074] See appendix Figure 3 In a preferred embodiment of the present invention, the control system built into the microcontroller calls various device components arranged on the control circuit board 3 to perform closed-loop regulation and safety monitoring of the operating status and speed of the low-voltage motor.

[0075] The control system includes a power management module, a command acquisition module, a status determination module, a speed calculation module, a closed-loop regulation module, a safety monitoring module, and a dynamic threshold reconstruction module.

[0076] The aforementioned functional modules rely on the computing resources of the microcontroller to work together and interact with the physical hardware units on the control circuit board 3 to exchange data and issue commands.

[0077] The power management module receives external power through the power input and filtering unit and calls the buck regulator unit to convert the external power into a stable low-voltage logic voltage. This stable low-voltage logic voltage typically provides the basic operating power for various modules inside the microcontroller and peripheral sensing and sampling devices.

[0078] After acquiring a stable low-voltage logic voltage, the instruction acquisition module begins to operate independently. In this embodiment, the instruction acquisition module uses the PWM signal input unit to capture external control commands and parses the level transition period of the external control commands to generate an input duty cycle. This input duty cycle is transmitted to the status determination module as a reference input parameter for subsequent speed regulation and start / stop judgment.

[0079] The status determination module receives the input duty cycle and processes it through multi-level safety threshold determination logic to determine the current macroscopic operating state. This multi-level safety threshold determination logic pre-sets shutdown and start thresholds based on the low-voltage motor's operating state switching conditions. When the input duty cycle is less than the shutdown threshold, the status determination module generates a stop command and determines it as the macroscopic operating state, while simultaneously outputting a zero duty cycle signal to the motor power drive unit to force the low-voltage motor to stop.

[0080] On the other hand, when the input duty cycle is within the range of being greater than or equal to the shutdown threshold and less than the start threshold, the state determination module determines to maintain the current start-stop mode and treats it as the macroscopic operating state. This range creates a buffer zone at the logic level, helping to prevent frequent start-stops of the low-voltage motor caused by minor fluctuations in external control commands at critical states. Conversely, when the input duty cycle is greater than or equal to the start threshold, the state determination module determines that a valid operating command is in effect and treats it as the macroscopic operating state.

[0081] Once the status determination module establishes a valid operating command, the speed calculation module begins to calculate the specific target speed. If the input duty cycle is within the preset linear speed regulation range, the speed calculation module calls the speed mapping formula and calculates the target speed by combining the motor's minimum stable operating speed and the motor's maximum rated operating speed. If the input duty cycle is within the preset limit output range, the speed calculation module skips the mapping calculation process and directly locks the target speed to the motor's maximum rated operating speed.

[0082] The closed-loop control module continuously performs dynamic corrections during motor operation. This module receives the target speed, uses the back electromotive force and voltage sampling unit to obtain the actual operating speed of the low-voltage motor, and extracts the compensation amount for the numerical deviation between the actual operating speed and the target speed, performing algebraic summation to generate a dynamic compensation duty cycle.

[0083] The closed-loop control module dynamically compensates the duty cycle and generates the output PWM drive duty cycle, which is then transmitted to the motor power drive unit.

[0084] In addition to the main speed control process described above, to cope with extreme operating conditions, the safety monitoring module executes a full-cycle protection mechanism independently of the main loop. This safety monitoring module uses a current sampling unit to read the analog voltage signal reflecting the load status of the low-voltage motor in real time, and simultaneously uses a temperature detection unit to acquire the physical resistance signal reflecting the physical temperature rise of the power device area in real time.

[0085] When the detected analog voltage signal exceeds the overcurrent safety threshold, or the physical resistance signal is greater than or equal to the safety critical point, the safety monitoring module generates a safety interruption to cut off the motor power drive unit. This overcurrent safety threshold and safety critical point are preset based on the hardware safety protection parameters of the low-voltage motor. Real-time interruption based on hardware sampling can significantly reduce the risk of damage to the low-voltage motor under extreme conditions such as overload or heat dissipation failure.

[0086] In this embodiment, the power management module undertakes the fundamental functions of low-voltage motor power conversion and power quality assurance, providing an electrical reference for the execution of subsequent control logic. Specifically, the power management module receives external power using a power input and filtering unit.

[0087] To cope with complex external power supply environments, the power management module uses a reverse connection protection circuit in the power input and filtering unit to detect and protect the external power supply polarity. This significantly reduces the risk of physical damage caused by reversed power supply polarity. Simultaneously, the power management module utilizes an internal filter capacitor array and transient voltage suppressor to filter out high-frequency noise and surge voltages from the external power supply, thereby improving the purity of the input voltage. To further suppress electromagnetic interference, as a preferred approach, the unit can also be equipped with ferrite beads or common-mode inductors to optimize the current quality entering subsequent circuits.

[0088] The rated input range of the external power supply is usually preset based on the application scenario and electric drive power requirements of the low-voltage motor. For example, in automotive applications or industrial drive fields, the rated input voltage of the external power supply can be set to DC 12V or 24V, and its allowable fluctuation range is usually set within ±20% of the rated value.

[0089] The power management module invokes the buck regulator unit to perform voltage dip and regulation actions. Specifically, the buck regulator unit converts the processed external power supply through an internally integrated low-dropout linear regulator or synchronous buck converter, thereby outputting a stable low-voltage logic voltage.

[0090] In this embodiment, the buck regulator unit typically includes a closed-loop feedback loop. By sampling the output voltage through voltage division and feeding it back to the internal error amplifier, the on-time of the power transistor is dynamically adjusted to ensure a constant output voltage. The specific circuit architecture design for this conversion process, such as adjusting the duty cycle of the switching transistor through a PWM controller to maintain a constant output voltage, is well-known in the art and will not be described in detail here.

[0091] The stable low-voltage logic voltage generated by the power management module is preset based on the microcontroller's logic level standard and the power supply requirements of the peripheral units.

[0092] In this embodiment, the stable low-voltage logic voltage can be set to DC 3.3V or 5V to provide continuous and stable power support for the microcontroller, PWM signal input unit, and temperature detection unit. Precise adjustment of the buck regulator unit helps ensure that the fluctuation rate of the stable low-voltage logic voltage remains within a preset range (e.g., less than ±5%) when the external power supply experiences fluctuations of a certain magnitude, thereby guaranteeing the determinism and reliability of the entire system's logic operations.

[0093] In summary, the power management module distributes the stable low-voltage logic voltage to various functional modules within the control system. This power supply architecture, based on the collaboration of hardware units and software modules, solves the problem of voltage drops that may occur during the startup of low-voltage motors or during heavy load switching.

[0094] In this embodiment, after the power management module establishes an electrical reference, the command acquisition module performs digital analysis on the externally input speed control signal.

[0095] Specifically, the command acquisition module uses a PWM signal input unit to capture external control commands. Considering that external control commands are often affected by the electromagnetic compatibility of external cables during transmission, the PWM signal input unit is preferably configured with an RC filter network at the physical layer. This network performs preliminary noise reduction on the input signal through a preset cutoff frequency, which helps improve the stability of the subsequent signal edge recognition by the microcontroller.

[0096] In the specific implementation of signal analysis, the core of this module is how to convert continuous level transitions into digital duty cycle information. The instruction acquisition module obtains the level transition period by performing high-frequency monitoring of the waveform characteristics of external control instructions.

[0097] Specifically, the microcontroller's timer peripheral uses its input capture function to time the rising and falling edges of the PWM waveform. The instruction acquisition module measures and records the time interval between two adjacent rising edges in real time, defining it as the total period; it also records the time interval between each rising edge and the immediately following falling edge, defining it as the high-level duration. Based on this, the instruction acquisition module calculates and generates the input duty cycle by dividing the count value corresponding to the high-level duration by the count value corresponding to the total period.

[0098] In this embodiment, in order to ensure the integrity of the algorithm logic and avoid logic dead zones, the instruction acquisition module is also equipped with a timeout detection mechanism; if no level transition is detected within the preset time threshold (e.g., 50ms to 100ms, set according to the minimum allowable frequency of the external control instruction), the input duty cycle is directly determined to be 0% or 100% based on the current physical level state.

[0099] The sampling frequency used in the above analysis process is usually preset based on the control accuracy requirements of the low-voltage motor. For example, to ensure that the speed regulation resolution is better than 0.1%, the internal sampling clock frequency of the command acquisition module is usually set to more than 1000 times the external control command frequency.

[0100] As a specific application example, if the frequency range of the external control command is set between 100Hz and 10kHz, the command acquisition module configures the timer prescaler to maintain the counting clock frequency between 1MHz and 10MHz, thereby ensuring that sufficient sampling depth can be obtained at different frequencies.

[0101] The command acquisition module also includes a filtering mechanism for invalid signals during the generation of the input duty cycle. In this embodiment, if the command acquisition module detects a significant abnormality in the total period or the duration of the high level, such as a measured periodic signal far exceeding the preset pulse width range, it determines that the current external control command is an interference signal and performs error masking processing. This logic of verifying the integrity of the waveform's time-domain characteristics largely ensures the authenticity of the input duty cycle.

[0102] In summary, after calculating the input duty cycle, the instruction acquisition module will temporarily store it in an internal register or memory buffer for subsequent use by the status determination module and the speed calculation module.

[0103] In this embodiment, the state determination module receives the input duty cycle output by the instruction acquisition module and calls the multi-level safety threshold determination logic for processing to establish the current macroscopic operating state. This multi-level safety threshold determination logic uses a preset asymmetric threshold range to logically map the input duty cycle, thereby constructing a determination mechanism with a hysteresis effect at the program execution level.

[0104] To achieve precise control over the start-up and shutdown process of low-voltage motors, multi-level safety threshold judgment logic typically introduces dual judgment criteria.

[0105] Specifically, the multi-level safety threshold determination logic pre-sets shutdown and start thresholds based on the low-voltage motor's operating state switching conditions. When the state determination module detects that the input duty cycle is less than the shutdown threshold, the multi-level safety threshold determination logic generates a shutdown command and issues it as the macroscopic operating state. In this state, the microcontroller outputs a zero duty cycle signal to the motor power drive unit to force the low-voltage motor's rotor to stop rotating. As a preferred method, the system will clear the microcontroller's internal status register at this time to mark the current shutdown record state.

[0106] Considering the possible back-and-forth fluctuations of the signal at the critical point, when the value of the input duty cycle gradually increases and falls within the range of being greater than or equal to the shutdown threshold and less than the startup threshold, the multi-level safety threshold determination logic generates a determination to maintain the current start-stop mode.

[0107] Specifically, the status determination module will read the running flag bit of the previous operation cycle stored in the status register; if the previous cycle was in the stop state, it will maintain the zero duty cycle of the output; if the previous cycle was in the valid running state, it will continue to run without switching states.

[0108] By establishing a logical buffer between physical shutdown and formal startup, it helps prevent frequent start-stop of low-voltage motors caused by slight jumps in external control commands near critical points.

[0109] In this embodiment, the shutdown threshold is usually preset based on the sampling noise margin of the external signal line (e.g., set to 8%), while the start threshold is preset based on the minimum torque duty cycle required for the low-voltage motor to overcome rotor static friction (e.g., set to 10%).

[0110] Furthermore, if the input duty cycle continues to increase and reaches a range greater than or equal to the start-up threshold, the multi-level safety threshold determination logic generates a valid operating instruction and transmits it as the macroscopic operating status to the subsequent speed control stage. At this time, the status determination module confirms that the low-voltage motor has entered the speed control activation stage and sets the status register.

[0111] By using segmented state determination, the multi-level safety threshold determination logic utilizes the difference between the start threshold and the stop threshold to shield control jitter caused by electromagnetic interference or insufficient duty cycle adjustment accuracy of the host computer at the logic level.

[0112] In summary, the macroscopic operating status output by the status determination module determines the permitted power output of the low-voltage motor. The hysteresis comparison calculation process involved in the multi-level safety threshold determination logic can be implemented by those skilled in the art through the comparison logic unit or conditional judgment statement within the microcontroller. The specific code implementation logic is well-known in the field and will not be elaborated upon here.

[0113] In this embodiment, provided that the status determination module confirms that the operation command is valid, the speed calculation module receives the input duty cycle output by the command acquisition module and executes the corresponding calculation logic according to the range of the value.

[0114] From the perspective of speed regulation smoothness, when the speed calculation module detects that the input duty cycle is within the preset linear speed regulation range, the system will perform linear mapping calculation to achieve continuous speed adjustment. In this embodiment, the preset linear speed regulation range is pre-set based on the electromagnetic torque characteristics of the low-voltage motor and the speed regulation resolution requirements of the host computer (e.g., set to [10%, 90%)). Within this range, the speed calculation module linearly maps the input duty cycle to the target speed of the motor by calling the speed mapping formula. The speed mapping formula is as follows:

[0115] ;

[0116] In the formula: The target rotational speed; Input duty cycle; This is the minimum stable operating speed of the motor; This refers to the motor's maximum rated operating speed.

[0117] To ensure the integrity of the algorithm logic and avoid logical dead zones near the start-up threshold, as a preferred approach, if the state determination module determines that the current macroscopic operating state is a valid operating command, but the input duty cycle is below the start-up threshold (e.g., maintained between 8% and 10% due to hysteresis), the speed calculation module typically sets the target speed directly to the motor's minimum stable operating speed without performing the aforementioned subtraction operation. This approach ensures that the motor always operates within the preset physical safety boundaries.

[0118] To ensure reliable operation of the motor under various load conditions, the minimum stable operating speed of the motor is typically preset based on the back electromotive force observation accuracy and load-bearing starting capability of the low-voltage motor, for example, set to 500 rpm; while the maximum rated operating speed of the motor is preset based on the bearing mechanical strength and temperature rise limit of the low-voltage motor, for example, set to 3000 rpm. This mapping method, achieved through normalization calculation, helps ensure that when the input duty cycle varies within the preset linear speed regulation range, the target speed can smoothly and linearly switch between the minimum and maximum values.

[0119] On the other hand, if the input duty cycle continues to increase and enters the preset limit output range, the speed calculation module executes the full-power operation logic. In this embodiment, the preset limit output range is pre-set based on the system redundancy and the fault tolerance range of the full-speed operation command (for example, set as [90%, 100%]). Within this range, the speed calculation module will no longer perform algebraic operations on the speed mapping formula, but will directly lock the target speed to the motor's maximum rated operating speed, simplifying the algorithm overhead and ensuring that the low-voltage motor can operate stably at its rated maximum power when the host computer outputs the maximum speed regulation signal.

[0120] In summary, the target speed calculated by the speed calculation module is stored in the system memory as a reference input for the closed-loop control module. Through the coordinated operation of the preset linear speed regulation range and the preset limit output range, the speed calculation module achieves full-range coverage of the input duty cycle. For the piecewise interpolation and fixed-point number processing involved in the speed mapping formula, those skilled in the art can use the multiplier and adder units within the microcontroller for real-time calculation. The specific underlying instruction set is well-known in the field and will not be elaborated upon here.

[0121] In this embodiment, the closed-loop control module receives the target speed output by the speed calculation module. The closed-loop control module uses a back electromotive force and voltage sampling unit to obtain the actual operating speed. In this embodiment, the low-voltage motor typically adopts a sensorless speed control architecture. The back electromotive force and voltage sampling unit collects the residual voltage of the unconducted phase in the motor power drive unit by voltage division, and captures the voltage zero-crossing point by comparing the divided coil voltage signal with half of the bus voltage.

[0122] The closed-loop control module calculates the current actual operating speed by calculating the time interval between two adjacent zero intersections and combining this with the number of pole pairs of the motor. This sampling frequency is usually preset based on the maximum speed of the low-voltage motor and the sampling accuracy requirements, for example, set to perform sampling calculations once every 500μs or 1ms.

[0123] After obtaining the actual operating speed, the closed-loop control module compares the target speed with the actual operating speed and extracts the numerical deviation between the actual operating speed and the target speed.

[0124] Building upon this foundation, to make deviation compensation more targeted, the closed-loop control module introduces algebraic summation processing logic to generate a dynamic compensation duty cycle. Specifically, this dynamic compensation duty cycle is obtained by performing a proportional operation on the current numerical deviation, integrating it with the historical cumulative value of that numerical deviation, and then performing an algebraic summation. The proportional operation involves multiplying the numerical deviation by a preset proportionality coefficient; the integral operation involves multiplying the cumulative sum of the numerical deviations by a preset integral coefficient.

[0125] As a preferred approach, the aforementioned preset proportional coefficient is usually pre-set based on the dynamic response speed requirements of the system (e.g., set between 0.05 and 0.2) to quickly suppress speed fluctuations; while the preset integral coefficient is pre-set based on the system's steady-state error elimination capability (e.g., set between 0.01 and 0.05) to compensate for speed deficits caused by load friction.

[0126] In this embodiment, in order to avoid integral saturation and ensure the integrity of the algorithm logic, the closed-loop control module usually performs amplitude limiting on the integral accumulation terms involved in the algebraic summation to prevent the system from overshooting or losing control when the motor is blocked for a long time or the speed changes drastically.

[0127] The closed-loop control module superimposes the dynamically compensated duty cycle to generate the output PWM drive duty cycle. In this embodiment, the process of generating the output PWM drive duty cycle typically involves a combination of feedforward control and feedback compensation. That is, the system uses the base duty cycle calculated by the speed calculation module as a reference and algebraically superimposes it with the dynamically compensated duty cycle. To prevent the calculation result from exceeding the hardware drive limit, the closed-loop control module usually performs amplitude limiting processing on the superimposed value, restricting it to a legal range of 0% to 100%.

[0128] Through a feedback loop, the closed-loop control module transmits the generated output PWM drive duty cycle to the motor power drive unit. This motor power drive unit adjusts the conduction ratio of the power MOSFETs according to the instructions, changing the average voltage applied to the motor windings. This ensures that when the load changes abruptly, the low-voltage motor can dynamically compensate for the duty cycle, allowing the actual operating speed to return to near the target speed within a short time. This helps ensure the speed determinism of the low-voltage motor under complex operating conditions.

[0129] The control algorithms and parameter debugging process involved in this module can be configured by those skilled in the art according to the rotational inertia of the specific motor. The specific underlying implementation method is a well-known technology in this field and will not be described in detail here.

[0130] In this embodiment, the safety monitoring module is used to monitor the motor's operating load and physical temperature rise in real time throughout the entire cycle.

[0131] Specifically, during the operation of the low-voltage motor, the safety monitoring module uses a current sampling unit to read the analog voltage signal reflecting the load status of the low-voltage motor in real time, and uses a temperature detection unit to obtain the physical resistance signal reflecting the physical temperature rise of the power device area in real time.

[0132] To accurately assess the risks of motor overload and stall, the safety monitoring module uses a current sampling unit to convert the main circuit current in real time. Specifically, the current sampling unit typically includes a precision sampling resistor connected in series in the power supply path of the motor power drive unit (for example, the sampling resistor can be set in the low-voltage side main circuit of a three-phase inverter bridge). The voltage drop generated when current flows through this sampling resistor is captured by the control system as an analog voltage signal. Based on this, the safety monitoring module compares this analog voltage signal with a preset overcurrent safety threshold.

[0133] As a preferred approach, the overcurrent safety threshold is preset based on the hardware safety protection parameters of the low-voltage motor. Its specific value is typically determined by referencing the rated maximum continuous current of the power MOSFET in the motor power drive unit and the resistance accuracy of the sampling resistor. For example, when the maximum allowable current of the power device is 20A and the sampling resistor is 10mΩ, considering the voltage drop margin of the circuit board traces, the overcurrent safety threshold can be set to 200mV to 220mV. Once the analog voltage signal exceeds this overcurrent safety threshold, the safety monitoring module determines that the motor is currently in an overcurrent or abnormally obstructed state.

[0134] Regarding thermal failure protection for power devices, the safety monitoring module utilizes a temperature detection unit to acquire physical resistance signals. This temperature detection unit typically employs a negative temperature coefficient thermistor and is mounted near the motor power drive unit on the control circuit board 3. As heat accumulates from the power devices, the thermistor value shifts accordingly, and this shift is read by the safety monitoring module as the physical resistance signal. Subsequently, the safety monitoring module compares this physical resistance signal with a preset safety threshold.

[0135] In this embodiment, the safety threshold is preset based on the hardware safety protection parameters of the low-voltage motor. Its value usually corresponds to the specific resistance value of the thermistor at the highest allowable temperature that the power device or control circuit board 3 substrate can withstand (e.g., set to 105°C or 125°C), which can monitor the dynamic balance of heat exchange in the power device area in real time.

[0136] When the detected analog voltage signal exceeds the overcurrent safety threshold, or the physical resistance signal is greater than or equal to the safety critical point, the safety monitoring module generates a safety blocking mechanism.

[0137] In this embodiment, the specific lower-level features for generating safety blocking include, but are not limited to: using a hardware fault inside the microcontroller to block the input terminal (e.g., the microcontroller's Break control register), directly blocking the PWM signal pulse output to the motor power drive unit, or pulling down the logic enable pin of the motor power drive unit.

[0138] The blocking action of directly cutting off the execution path of the motor power drive unit can cut off the current path of the motor in a short time because it does not rely on the scheduling of the software speed regulation cycle.

[0139] To ensure the integrity of the algorithm logic and avoid frequent cut-offs and recovery at critical points, in this embodiment, once a safety block is triggered, the system usually enters a fault-locked state; only when the physical resistance signal recovers to below the preset recovery threshold (the corresponding temperature is usually 10°C to 20°C lower than the temperature corresponding to the safety critical point) and a reset signal from an external control command is received, the safety monitoring module allows the safety block to be released.

[0140] By implementing closed-loop monitoring of both electrical and thermal energy indicators, an automatic avoidance mechanism for low-voltage motors under extreme operating conditions is constructed. This real-time protection logic, based on current sampling units and temperature detection units, enhances the low-voltage motor's tolerance to harsh environments such as stall, overload, and high ambient temperatures.

[0141] For the analog signal filtering and comparator hysteresis parameter configuration involved in the safety monitoring module, those skilled in the art can select the appropriate model based on the specific electromagnetic compatibility test standards. The specific underlying circuit implementation is a well-known technology in this field and will not be described in detail here.

[0142] In this embodiment, the control system further includes a dynamic threshold reconstruction module. This module relies on a microcontroller for core logic operations and integrates signal feedback from the back electromotive force and voltage sampling units, as well as the current sampling unit, to achieve its functionalities. The dynamic threshold reconstruction module is used to construct a feedforward elastic protection mechanism based on real-time operating condition perception. This module receives the numerical deviation extracted by the closed-loop control module and the macroscopic operating status output by the state determination module.

[0143] To achieve feedforward elastic protection, the dynamic threshold reconstruction module utilizes dynamic safety threshold reconstruction logic to calculate and generate a threshold expansion coefficient in real time based on the absolute value of the numerical deviation. Specifically, the logic by which the dynamic threshold reconstruction module calls the dynamic safety threshold reconstruction logic to generate the threshold expansion coefficient is as follows: extract the absolute value of the numerical deviation and determine whether it exceeds the steady-state error tolerance. The steady-state error tolerance is preset based on the dynamic response requirements of the low-voltage motor (e.g., set to 50 rpm).

[0144] As a preferred approach, if the absolute value of the numerical deviation is less than or equal to the steady-state error tolerance, it usually indicates that the low-voltage motor is currently in a stable operating phase with good command follow-up. Under this condition, the system does not need to provide additional transient high current support, and the dynamic threshold reconstruction module directly sets the threshold expansion coefficient to the base value. The base value is preset based on the dynamic response requirements of the low-voltage motor (e.g., set to a constant of 1.0).

[0145] When a motor encounters a sudden load or a rapid acceleration command, the rotor speed often drops or lags, causing the back electromotive force in the stator coil to decrease instantaneously. Under the premise of stable supply voltage, the decrease in back electromotive force will cause the phase current to rise naturally, thereby providing the low-voltage motor with the extra electromagnetic torque required to overcome the load. If the original static safety boundary is maintained at this time, this normal dynamic compensation current used to restore speed is easily misjudged as an overcurrent abnormality.

[0146] Based on the above reasons, if the absolute value of the numerical deviation is greater than the steady-state error tolerance, it indicates that the low-voltage motor is currently facing a sudden external load or has received a rapid acceleration external control command, requiring the low-voltage motor to relax its current limit to output a large torque for dynamic compensation. At this time, the dynamic threshold reconstruction module calculates the excess difference between the absolute value of the numerical deviation and the steady-state error tolerance, multiplies the excess difference by a preset proportional gain constant, and then adds it to the base value to obtain the calculated expansion coefficient value. The proportional gain constant is preset based on the dynamic response requirements of the low-voltage motor (e.g., set to 0.01).

[0147] Considering that excessively relaxing the safety boundary may increase the risk of thermal runaway or damage to the underlying power devices, an arithmetic limiting determination is introduced. The dynamic threshold reconstruction module compares the calculated expansion coefficient value with the maximum expansion coefficient limit value. The maximum expansion coefficient limit value is preset based on the dynamic response requirements of the low-voltage motor (e.g., set to 1.5).

[0148] If the calculated value of the expansion coefficient is greater than the maximum expansion coefficient limit, the dynamic threshold reconstruction module will trigger the limit protection action and use the maximum expansion coefficient limit as the final threshold expansion coefficient; otherwise, the calculated value of the expansion coefficient will be used as the final threshold expansion coefficient.

[0149] After completing the above logical judgment and data assignment, the dynamic threshold reconstruction module multiplies the reference overcurrent threshold and the threshold expansion coefficient to generate a dynamic overcurrent safety threshold in real time. The reference overcurrent threshold is preset based on the rated current parameters of the low-voltage motor (e.g., set to 200mV).

[0150] After generating the dynamic overcurrent safety threshold, the dynamic threshold reconstruction module synchronizes the dynamic overcurrent safety threshold to the safety monitoring module, replacing the original overcurrent safety threshold. The safety monitoring module then compares this dynamically updated dynamic overcurrent safety threshold with the real-time read analog voltage signal to determine whether to cut off the motor power drive unit.

[0151] In addition to dynamic relaxation logic based on numerical deviation, the dynamic threshold reconstruction module also features a degradation interlock function based on motor operating conditions. When the state determination module determines that the macroscopic operating state is to maintain the current start-stop mode, the dynamic threshold reconstruction module forcibly locks the threshold expansion coefficient to the base value. The cross-interlock mechanism enables the current determination boundary to be tightened directly when the motor is in the sensitive start-up range, thereby preventing abnormal hardware overheating caused by ineffective high-frequency excitation pulses when the low-voltage motor is alternating at low speeds at the start-stop critical point.

[0152] For the specific numerical extraction, conditional branch comparison, floating-point multiplication operation, and the underlying microprocessor operation mechanism of writing the calculation results into the memory register for other modules to call in the dynamic threshold reconstruction module, those skilled in the art can refer to the arithmetic logic unit configuration specification of the microcontroller kernel for code implementation and compilation. Its underlying hardware calculation process is a well-known technology in this field and will not be described in detail here.

Claims

1. A low-voltage motor based on piecewise threshold PWM control, characterized in that, The device includes a motor housing (1), a motor tail cover (2) is provided at the rear of the motor housing (1), a control circuit board (3) is installed in the middle of the motor tail cover (2), and a device assembly is provided on the surface of the control circuit board (3). The device assembly includes a microcontroller, a PWM signal input unit, a power input and filtering unit, a step-down voltage regulation unit, a back electromotive force and voltage sampling unit, a motor power drive unit, a current sampling unit and a temperature detection unit mounted on the control circuit board (3). The microcontroller has a built-in control system, which is used to receive external control commands and perform closed-loop regulation and safety monitoring of the operating status and speed of the low-voltage motor. The control system includes: The power management module is used to receive external power through the power input and filtering unit and call the buck regulator unit to convert the external power into a stable low-voltage logic voltage. The instruction acquisition module is used to capture the external control instruction using the PWM signal input unit and parse the external control instruction to generate the input duty cycle; The status determination module is used to receive the input duty cycle, process it through multi-level safety threshold determination logic, and determine the current macroscopic operating status. The speed calculation module is used to determine when the macroscopic operating state is a valid operating command. If the input duty cycle is in the preset linear speed regulation range, the target speed is calculated by calling the speed mapping formula. If the input duty cycle is in the preset limit output range, the target speed is directly locked to the maximum rated operating speed of the motor. The closed-loop control module is used to receive the target speed, obtain the actual operating speed of the low-voltage motor using the back electromotive force and voltage sampling unit, extract the compensation amount of the numerical deviation between the actual operating speed and the target speed, perform algebraic summation to generate a dynamic compensation duty cycle, and superimpose the dynamic compensation duty cycle to generate an output PWM drive duty cycle, which is then transmitted to the motor power drive unit. The multi-level security threshold determination logic of the state determination module is specifically as follows: When the input duty cycle is less than the shutdown threshold, a stop command is generated and determined as the macroscopic operating state. A zero duty cycle signal is output to the motor power drive unit to force the low-voltage motor to stop. When the input duty cycle is in the range of being greater than or equal to the shutdown threshold and less than the startup threshold, a determination to maintain the current start-stop mode is generated and used as the macroscopic operating state. When the input duty cycle is greater than or equal to the startup threshold, the determination of the valid running instruction is generated and used as the macroscopic running state.

2. A low-voltage motor based on piecewise threshold PWM control according to claim 1, characterized in that, The power management module is specifically used for: The external power supply is protected against polarity issues by using the reverse connection protection circuit of the power input and filtering unit, and noise is filtered out by using the filter capacitor array and transient voltage suppressor. The conversion is performed using a low-dropout linear regulator or synchronous buck converter integrated within the buck regulator unit, and the on-time of the power transistor is dynamically adjusted through a closed-loop feedback loop to output a constant stable low-voltage logic voltage.

3. A low-voltage motor based on piecewise threshold PWM control according to claim 1, characterized in that, The control system further includes a safety monitoring module, which is used for: The current sampling unit is used to read the analog voltage signal reflecting the load state of the low-voltage motor in real time, and the temperature detection unit is used to obtain the physical resistance signal reflecting the physical temperature rise of the power device area in real time. When the simulated voltage signal is detected to be greater than the overcurrent safety threshold, or the physical resistance signal is greater than or equal to the safety critical point, a safety blocking is generated to cut off the motor power drive unit.

4. A low-voltage motor based on piecewise threshold PWM control according to claim 3, characterized in that, The control system further includes a dynamic threshold reconstruction module, which is used to receive the numerical deviation and the macroscopic operating status using the back electromotive force and voltage sampling unit and the current sampling unit. Using dynamic safety threshold reconstruction logic, a threshold expansion coefficient is calculated in real time based on the absolute value of the numerical deviation. The reference overcurrent threshold is multiplied by the threshold expansion coefficient to generate a dynamic overcurrent safety threshold in real time. The dynamic overcurrent safety threshold is then synchronized to the safety monitoring module to replace the original overcurrent safety threshold.

5. A low-voltage motor based on segmented threshold PWM control according to claim 4, characterized in that, The specific logic by which the dynamic threshold reconstruction module generates the threshold expansion coefficient using the dynamic security threshold reconstruction logic is as follows: Extract the absolute value of the numerical deviation and determine whether it exceeds the steady-state error tolerance: If the absolute value of the numerical deviation is less than or equal to the steady-state error tolerance, then the threshold expansion coefficient is set to the base value; If the absolute value of the numerical deviation is greater than the steady-state error tolerance, then the excess difference between the absolute value of the numerical deviation and the steady-state error tolerance is calculated, and the excess difference is multiplied by a preset proportional gain constant and then added to the base value to obtain the expansion coefficient calculation value. The calculated value of the expansion coefficient is compared with the maximum expansion coefficient limit. If the calculated value of the expansion coefficient is greater than the maximum expansion coefficient limit, the maximum expansion coefficient limit is used as the final threshold expansion coefficient; otherwise, the calculated value of the expansion coefficient is used as the final threshold expansion coefficient.

6. A low-voltage motor based on segmented threshold PWM control according to claim 5, characterized in that, The dynamic threshold reconstruction module is also used to forcibly lock the threshold expansion coefficient to the base value when the state determination module determines that the macroscopic operating state is to maintain the current start-stop mode.

7. A low-voltage motor based on piecewise threshold PWM control according to claim 6, characterized in that, The preset linear speed regulation range and the preset limit output range are preset based on the speed regulation conditions of the low-voltage motor. The shutdown threshold and the start threshold are preset based on the operating state switching conditions of the low-voltage motor; The overcurrent safety threshold and the safety critical point are preset based on the hardware safety protection parameters of the low-voltage motor; The reference overcurrent threshold is preset based on the rated current parameters of the low-voltage motor; The steady-state error tolerance, the base value, the proportional gain constant, and the maximum expansion coefficient limit are preset based on the dynamic response requirements of the low-voltage motor.

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