Projector direct current motor locked-rotor detection system and method

Abstract

The invention relates to a projector direct current motor locked-rotor detection system and method. The detection system comprises a main control module, a projection lens, a direct current motor, a motor driving module and a sampling comparison module. The motor driving module is connected, and the direct current motor is connected with the projection lens to form a corresponding driving loop; the comparison signal output end of the sampling comparison module is connected with the signal input end of the main control module, and the comparison signal output end of the sampling comparison module is output into the main control module; the control signal output end of the main control module is connected with the control signal input end of the motor driving module, and the physical characteristic that the sampling voltage is remarkably changed due to the fact that the current of the direct-current motor sharply rises in the locked-rotor state is utilized. Lens stroke end detection which can only be completed by depending on a mechanical limiting piece originally is converted into real-time electronic detection on a voltage signal of a driving loop. Therefore, a lens limiting detection effect which is more suitable for miniaturized and highly integrated projection equipment is obtained.

Description

Technical Field

[0001] This invention relates to the technical field of motor stall detection, and in particular to a DC motor stall detection system and method for projectors. Background Technology

[0002] Currently, projectors typically rely on a motor to move the lens along the optical axis to adjust the focus. Common driving methods in existing technologies include stepper motors, which are widely used due to their mature control mechanisms. To detect the end of the lens travel, current projector products generally require an additional limit detection mechanism within the stepper motor solution. A traditional stepper motor solution typically includes the stepper motor body, lens drive connection components, a limit component for detecting the end position of the lens (such as an optocoupler limiter or a mechanical hard switch), a separate detection board circuit for processing the limit signal, a stepper motor driver IC, and the projector's main control chip (SOC). During operation, the stepper motor moves the lens. When the lens reaches the end of its travel, the limit component is triggered. The trigger signal is processed by the separate detection board and transmitted to the SOC, which then controls the stepper motor to stop, thus completing the end-of-journey detection of the lens travel.

[0003] However, such stepper motor solutions generally suffer from problems such as complex structure, large size and high cost: First, limit detection requires additional optocouplers or mechanical limit components, increasing the number of components; Second, limit components usually require independent small board circuits to process signals, making the overall structure more complex; Third, stepper motors are large in size, which is not conducive to their placement in the compact space of projectors. Summary of the Invention

[0004] To address the issues of complex limiting structures, limited size, and high cost in existing stepper motor solutions, this application provides a projector DC motor stall detection system and method.

[0005] A projector DC motor stall detection system, comprising a main control module, a projection lens, a DC motor, a motor drive module, and a sampling comparison module; The drive signal output terminal of the motor drive module is connected to the DC motor, and the DC motor is connected to the projection lens to control the rotation of the projection lens and form a corresponding drive circuit. The detection signal input terminal of the sampling comparison module is used to obtain the working voltage in the drive circuit. The comparison signal output terminal of the sampling comparison module is connected to the signal input terminal of the main control module. The sampling comparison module generates a corresponding comparison signal by comparing the working voltage with a preset reference voltage, and outputs it to the main control module through the comparison signal output terminal of the sampling comparison module. The control signal output terminal of the main control module is connected to the control signal input terminal of the motor drive module. When the comparison signal indicates that the DC motor is stalled, the main control module generates a corresponding control signal to control the motor drive module to stop driving the DC motor, thereby causing the projection lens to stop rotating.

[0006] By adopting the above technical solution, electronic limit detection of lens travel can be achieved without relying on mechanical limit components. The electrical characteristics of the motor when stalled are used as the trigger condition. After detecting abnormal working conditions, the drive output is interrupted in time, thereby effectively reducing the complexity of the overall structure, reducing the number of components and costs, and making lens limit control faster, more reliable and space-friendly.

[0007] Preferably, the sampling comparison module includes a comparator chip U2 and a sampling resistor RG42. The first end of the sampling resistor RG42 is connected to the power supply, the second end of the sampling resistor RG42 is connected to the power input terminal of the motor drive module, the common node between the second end of the sampling resistor RG42 and the power input terminal of the motor drive module is connected to the non-inverting input terminal of the comparator chip U2, the inverting input terminal of the comparator chip U2 obtains the corresponding reference voltage, and the signal output terminal of the comparator chip U2 is connected to the signal input terminal of the main control module.

[0008] By adopting the above technical solution, the voltage change corresponding to the current flowing through the DC motor can be sampled in real time, and a status signal can be generated through a simple and reliable voltage comparison method. This achieves high integration and high response speed in the stall judgment process, effectively improves the lens limit detection accuracy, and reduces dependence on external circuits and space occupation.

[0009] Preferably, the sampling comparison module further includes an adjustable resistor RG38 and an adjustable resistor RG39. The first end of the adjustable resistor RG38 is connected to the power supply, the second end of the adjustable resistor RG38 is connected to the first end of the adjustable resistor RG39, the second end of the adjustable resistor RG39 is grounded, and the common node between the second end of the adjustable resistor RG38 and the first end of the adjustable resistor RG39 is connected to the inverting input terminal of the comparator chip U2.

[0010] By adopting the above technical solution, the reference voltage can be flexibly adjusted according to the specific DC motor model, lens mechanism resistance difference, or overall factory calibration requirements. This allows for the precise setting of the stall judgment threshold based on different products or structural differences, improving the system's adaptability and electrical detection stability, and avoiding misjudgments or missed judgments caused by fixed thresholds.

[0011] A method for detecting stalled DC motors in projectors, applied to a system for detecting stalled DC motors in projectors, includes the following detection methods: After the main control module issues the start command for the DC motor, it enters and executes the surge shielding process during the start-up phase. If the surge shielding process is detected to have ended, the average operating current obtained in the surge shielding process is updated. Based on the updated average operating current and the historical peak current, the corresponding real-time dynamic stall threshold is calculated based on the adaptive adjustment model. The real-time dynamic stall threshold is used to determine the corresponding reference voltage. The operating voltage in the drive circuit is acquired in real time, and the operating voltage is compared with the reference voltage to generate a corresponding comparison signal, which is used to control whether the projection lens stops rotating. The adaptive adjustment model is updated based on the comparison signal.

[0012] By adopting the above technical solution, the reference voltage can be flexibly adjusted according to the specific DC motor model, lens mechanism resistance difference, or overall factory calibration requirements. This allows for the precise setting of the stall judgment threshold based on different products or structural differences, improving the system's adaptability and electrical detection stability, and avoiding misjudgments or missed judgments caused by fixed thresholds.

[0013] Preferably, the surge shielding process includes the following steps: When the main control module issues a start command for the DC motor, it records the corresponding start time information and obtains the working voltage data in the drive circuit from the moment corresponding to the start time information according to a preset sampling period. The operating voltage data acquired in each sampling period is sequentially converted into current sampling values ​​for the startup phase, and the current sampling values ​​are accumulated to form a current sampling sequence for the startup phase. Based on the current sampling sequence, determine whether the surge shielding process meets the preset termination condition; If the surge shielding process is determined to meet the preset termination conditions, the corresponding average operating current is calculated based on the current sampling sequence of the startup phase.

[0014] By adopting the above technical solution, and by collecting the current sampling sequence during the starting phase after the motor starts and performing surge shielding, abnormally high current fluctuations caused by the excitation current at the moment of motor start-up can be effectively filtered out, avoiding mistaking the starting current as the stall current. This allows the system to perform threshold calculations based solely on the average value of the operating current obtained after stabilization, significantly improving the stability and accuracy of stall detection.

[0015] Preferably, the step of determining whether the surge shielding process meets the preset termination condition based on the current sampling sequence includes: Based on the current sampling sequence, determine the current sampling value I(t) of the current sampling period and the current sampling value I(t-1) of the previous sampling period, as well as the time difference Δt between the time point corresponding to the current sampling period and the start time information. The current change rate dl is calculated using the formula: dl = I(t) - I(t-1); When the time difference Δt reaches the preset shielding duration, or when the current change rate dl changes from positive to negative and the number of sequences in the current sampling sequence reaches the preset number of consecutive samples, it is determined that the surge shielding process has met the preset termination condition.

[0016] By adopting the above technical solution, and by using factors such as the current sampling value, time difference, and current change rate between the current and the previous sampling period to determine whether the shielding phase has ended, the current stable range can be automatically identified under the natural decay trend of the motor starting characteristics, thereby accurately determining that the motor has entered the normal working state, and providing a more reliable data basis for the calculation of the average operating current and the generation of dynamic thresholds.

[0017] Preferably, the step of calculating the corresponding real-time dynamic stall threshold based on the updated average operating current and historical peak stall current using an adaptive adjustment model includes: Based on the updated average operating current and the historical peak current, the corresponding input variables are constructed and input into the adaptive adjustment model; Based on the adaptive adjustment model, the corresponding current prediction value is generated through a preset weighted calculation rule; Based on the predicted current value and the preset safety compensation coefficient, the corresponding preliminary dynamic stall threshold is calculated and generated. Upper and lower limits are imposed on the preliminary dynamic blocking threshold to generate the corresponding actual dynamic blocking threshold.

[0018] By adopting the above technical solution, the average operating current and the historical peak stall current are input into the adaptive adjustment model. Based on weighted calculation, current prediction, safety compensation and upper and lower limit constraints, a dynamic threshold is formed. The stall judgment threshold can be adaptively adjusted according to the actual operating status of the equipment. This can avoid misjudgment caused by a low threshold and also avoid missed judgment caused by a high threshold, thereby improving the system's long-term recognition capability when facing different structural resistance, temperature rise changes and lens aging.

[0019] Preferably, the step of calculating and generating the corresponding preliminary dynamic stall threshold based on the predicted current value and the preset safety compensation coefficient includes: The predicted current value is proportionally calculated with a preset safety compensation coefficient to generate a corresponding compensation current value. Based on the compensation current value, the corresponding preliminary dynamic stall threshold Ith is calculated according to the preset linear proportional adjustment rule. The calculation formula is as follows: Ith = Ka × Ic + Ba; Where Ka is the proportional coefficient, Ic is the compensation current value, and Ba is the bias coefficient.

[0020] By adopting the above technical solution, by applying safety compensation to the current prediction value and introducing a linear proportional adjustment formula, the final calculated preliminary dynamic stall threshold can have both prediction accuracy and safety margin. This ensures the sensitivity of stall detection and avoids false triggering caused by prediction deviation, making the threshold calculation more controllable and stable in engineering.

[0021] Preferably, the step of comparing the operating voltage with the reference voltage to generate a corresponding comparison signal for controlling whether the projection lens stops rotating includes: The operating voltage is compared with the reference voltage to calculate the corresponding voltage difference; The corresponding trend of change is determined based on the current sampling sequence, and a corresponding comparison signal is generated based on the voltage difference characteristics and the trend of change. The comparison signal is converted into a corresponding operating status identifier, which includes at least a normal operating status and a suspected stalled status. The current rotation direction of the projection lens is determined. Based on the rotation direction and the trend of change, it is determined whether the DC motor is in an actual stall state. If so, the main control module controls the motor drive chip to shut off the drive output to stop the lens rotation.

[0022] By adopting the above technical solution, by obtaining the difference between the working voltage and the reference voltage, and combining the voltage change trend with the lens rotation direction to generate a comparison signal to characterize the operating status, it is possible to accurately distinguish between normal load changes and actual stall behavior during lens movement. This allows the system to immediately stop driving when actual stall is detected, thereby avoiding continuous stress on the lens, damage to the mechanism, or limit collisions, and improving the protection capability of the entire focusing mechanism.

[0023] Preferably, the step of updating the adaptive adjustment model based on the comparison signal includes: Based on the comparison signal, determine the corresponding voltage difference amplitude characteristics, false positive and false negative characteristics, and upper and lower limit drift characteristics; Based on the voltage difference amplitude characteristics, a peak current estimate is generated to update the historical peak current parameters. Based on the aforementioned false positive and false negative characteristics, a sensitivity correction amount is generated to adjust the safety compensation coefficient; Based on the upper and lower limit drift characteristics, a range update amount is generated to correct the dynamic threshold upper and lower limit constraint interval.

[0024] By adopting the above technical solution, the voltage difference amplitude, misjudgment and omission features, and upper and lower limit drift features are extracted from the comparison signal and used to update the historical peak current, safety compensation coefficient, and upper and lower limit constraint range, respectively. This enables the adaptive adjustment model to continuously self-calibrate its own parameters according to the actual operation of the system, realize the continuous optimization of the threshold algorithm, and make the subsequent stall judgment process more accurate and more in line with the actual mechanical condition and long-term working characteristics of the equipment.

[0025] In summary, this application includes at least one of the following beneficial technical effects: This application introduces an electrical control link into the projector's focusing drive architecture, consisting of a main control module, a motor drive module, a DC motor, and a sampling and comparison module. Utilizing the physical characteristic that the DC motor experiences a sharp increase in current when stalled, leading to a significant change in the sampling voltage, the lens travel limit detection, originally reliant on mechanical limiters, is transformed into real-time electronic detection of the drive circuit voltage signal. The sampling and comparison module continuously collects the operating voltage of the DC motor and compares it in real-time with a preset reference voltage. When the comparison indicates that the motor has entered a stalled state, the main control module immediately receives the comparison signal and controls the motor drive module to stop output, thus directly achieving the lens limit protection function. This eliminates the need for traditional limit devices such as optocouplers and microswitches, and also eliminates the need for additional small circuit boards for limit signal processing. The overall limit detection structure is compressed into a simple circuit relationship between a sampling resistor, a comparator, and the main control chip, making the entire lens limit control mechanism more compact, intuitive, and highly integrated. Furthermore, due to the small size and simple drive chain of DC motors, this technology significantly reduces the space occupied by the internal structure of the projector while maintaining the reliability of the focusing function, reducing the number of components and manufacturing costs. At the same time, it avoids the wear, travel deviation and assembly complexity problems that may be caused by mechanical limiting parts, thus obtaining a lens limiting detection effect that is more suitable for miniaturized and highly integrated projection equipment. Attached Figure Description

[0026] Figure 1 This is a flowchart of a DC motor stall detection system for a projector according to one embodiment of this application; Figure 2 This is a detailed structural implementation diagram of a projector DC motor stall detection system according to one embodiment of this application; Figure 3 This is a flowchart illustrating the implementation of a DC motor stall detection method for a projector according to one embodiment of this application. Detailed Implementation

[0027] The present application will be further described in detail below with reference to the accompanying drawings.

[0028] In one embodiment, such as Figure 1 As shown, this application discloses a projector DC motor stall detection system, which includes a main control module, a projection lens, a DC motor, a motor drive module, and a sampling comparison module. The drive signal output terminal of the motor drive module is connected to the DC motor, and the DC motor is connected to the projection lens to control the rotation of the projection lens and form a corresponding drive circuit. The detection signal input terminal of the sampling and comparison module is used to obtain the working voltage in the drive circuit. The comparison signal output terminal of the sampling and comparison module is connected to the signal input terminal of the main control module. The sampling and comparison module generates a corresponding comparison signal by comparing the working voltage with the preset reference voltage, and outputs it to the main control module through the comparison signal output terminal of the sampling and comparison module. The control signal output terminal of the main control module is connected to the control signal input terminal of the motor drive module. When the comparison signal indicates that the DC motor is stalled, the main control module generates a corresponding control signal to control the motor drive module to stop driving the DC motor, thereby stopping the projection lens from rotating.

[0029] In this embodiment, the projector DC motor stall detection system comprises a main control module, a motor drive module, a DC motor, a projection lens, and a sampling and comparison module, forming an electrical control closed loop. The components are tightly coupled via electrical and mechanical transmission links to achieve coordinated control of lens focusing and stall detection. The main control module, as the core control unit of the entire system, establishes a stable digital control channel between its control signal output and the control signal input of the motor drive module, used to issue commands such as start, direction switching, and stop driving. After receiving the drive control signal from the main control module, the motor drive module generates corresponding motor drive voltage and current through its internal power switch array. Its drive signal output is directly connected to the positive and negative terminals of the DC motor, thus forming an electrical drive link between the main control module, the motor drive module, and the DC motor.

[0030] A DC motor is mechanically connected to the transmission assembly of the projection lens. The output of the motor shaft, controlled by the motor drive module, moves the lens along the optical axis, enabling real-time adjustment of the focus position. When the DC motor drives the lens load, its current magnitude varies with the lens's movement resistance, stroke position, and degree of mechanism jamming. These changes are directly reflected in the voltage drop characteristics of the motor's power supply circuit. Therefore, this embodiment incorporates a sampling comparison module in the DC motor's drive circuit, connecting its detection signal input to a voltage sampling point on the motor's drive path to obtain the sampling voltage corresponding to the motor's operating current in real time.

[0031] The sampling and comparison module integrates components such as a sampling resistor and a comparator. The sampling resistor converts the current change in the drive circuit into a measurable voltage signal, which is then input to one comparison terminal of the comparator. The other comparison terminal of the comparator is connected to a reference voltage set by the system or dynamically calculated, used to construct the stall threshold judgment range. When the motor is in normal rotation, the sampling voltage is lower than the reference voltage, and the comparator outputs a stable low level. However, when the lens reaches its travel limit or the mechanism jams, causing the motor to stall, the motor current surges, causing the sampling voltage to quickly exceed the reference voltage. At this point, the comparator immediately switches to a high-level output, which is transmitted to the signal input terminal of the main control module through its comparison signal output terminal.

[0032] The main control module determines whether the motor is stalled based on the received comparison signal. When the comparator output indicates a stall, the main control module immediately generates a shutdown command and transmits it to the motor drive module via the drive control link. This command cuts off the drive voltage to the DC motor, thereby stopping the lens movement in time and preventing mechanical damage to the focusing mechanism due to continuous stress. In this way, the system achieves electronic limit detection based on the motor's electrical characteristics, eliminating reliance on mechanical limit components such as optocouplers and microswitches. This fundamentally simplifies the structure of the projector's focusing assembly, improves the immediacy and reliability of limit detection, and significantly reduces the overall space occupation and cost.

[0033] Furthermore, such as Figure 2 As shown, the sampling and comparison module includes a comparator chip U2 and a sampling resistor RG42. The first end of the sampling resistor RG42 is connected to the power supply, the second end of the sampling resistor RG42 is connected to the power input terminal of the motor drive module, the common node between the second end of the sampling resistor RG42 and the power input terminal of the motor drive module is connected to the non-inverting input terminal of the comparator chip U2, the inverting input terminal of the comparator chip U2 obtains the corresponding reference voltage, and the signal output terminal of the comparator chip U2 is connected to the signal input terminal of the main control module.

[0034] In this embodiment, the sampling and comparison module consists of a comparator chip U2 and a sampling resistor RG42, and uses the current sampling point in the motor drive circuit as the core monitoring node to realize real-time determination of the DC motor's operating status. The first end of the sampling resistor RG42 is directly connected to the system power supply, and its second end is connected in series with the power input terminal of the motor drive module. This ensures that the operating current flowing through the motor drive module and the DC motor must first pass through the sampling resistor, resulting in a voltage drop across RG42 proportional to the current magnitude. This voltage drop varies significantly under different motor operating conditions. When the motor is under light load or in normal operation, the current is small, and the sampling voltage remains at a low level. When the lens movement is obstructed or the motor is stalled due to the transmission mechanism, the motor load increases sharply, and the high current generates a significantly increased voltage signal through the sampling resistor.

[0035] The non-inverting input of comparator chip U2 is directly connected to the second terminal of sampling resistor RG42, aligning with the current sampling node of the motor drive circuit, enabling U2 to instantly sense voltage changes across the sampling resistor. The inverting input of U2 receives a stable reference voltage, representing a stall threshold set by the system or dynamically calculated by the algorithm, used to distinguish between normal motor current and stall current. When the DC motor is operating normally, the sampling voltage at the non-inverting input is lower than the reference voltage at the inverting input, and the comparator output remains at a preset low level. When the sampling voltage is detected to rise above the reference voltage due to stall, the output of U2 immediately reverses to a high level to provide a clear stall indication signal to the main control module.

[0036] A stable digital communication path is established between the signal output terminal of comparator chip U2 and the signal input terminal of the main control module, enabling the main control module to receive the comparator's judgment result without delay. Once the comparator outputs a signal indicating an abnormal motor state, the main control module can trigger subsequent control actions based on this signal, including shutting off the output voltage of the motor drive module, stopping the rotation of the DC motor, or resetting the focusing process. This implementation completely transforms the motor stall detection from a mechanical limit mode to an electrical detection mode. It uses a simple and highly reliable circuit composed of a sampling resistor and a comparator to achieve accurate identification at the end of the lens travel, and the main control module responds quickly, thereby realizing electronic limit protection for the entire focusing mechanism.

[0037] Furthermore, such as Figure 2 As shown, the sampling comparison module also includes adjustable resistors RG38 and RG39. The first end of adjustable resistor RG38 is connected to the power supply, the second end of adjustable resistor RG38 is connected to the first end of adjustable resistor RG39, the second end of adjustable resistor RG39 is grounded, and the common node between the second end of adjustable resistor RG38 and the first end of adjustable resistor RG39 is connected to the inverting input of comparator chip U2.

[0038] In this embodiment, to obtain a stable and adjustable reference voltage for the inverting input of comparator chip U2, thereby adapting to the current characteristics of different DC motors under stall conditions, the sampling and comparison module further includes adjustable resistors RG38 and RG39, which form a reference voltage generation network in series. The first terminal of adjustable resistor RG38 is directly connected to the system power supply, and its second terminal is connected to the first terminal of adjustable resistor RG39. After being connected in series, the second terminal of RG39 is grounded, forming a voltage divider chain between the power supply and ground. By adjusting the resistance ratio of RG38 and RG39, different voltage levels can be obtained at their common node, making the voltage output at that node continuously adjustable within a certain range. This common node is also connected to the inverting input of comparator chip U2; therefore, the voltage divided at this point serves as the comparator's reference voltage input.

[0039] During actual operation of the DC motor, the sampling voltage across the sampling resistor RG42 fluctuates with changes in motor load. The reference voltage needs to be adjusted to a range that accurately distinguishes between normal operating current and stall current, based on factors such as product model, motor resistance, structural friction, and assembly tolerances. Through the adjustable structure of RG38 and RG39, R&D personnel or production line debugging personnel can fine-tune the voltage division ratio after assembly, based on the actual operating current of the prototype, ensuring the comparator's reference voltage precisely falls within the ideal stall threshold. When the DC motor is in normal operation, the sampling voltage is lower than this divided voltage, and the comparator maintains a low-level output. When the lens reaches its travel limit or encounters mechanical obstruction causing the motor to stall, the sampling voltage rises above the divided voltage, and the comparator immediately flips its output state.

[0040] This reference voltage generation method based on an adjustable voltage divider structure not only ensures the adaptability and flexibility of the entire stall detection circuit in different product environments, but also improves the controllability of the comparator's judgment threshold. This allows the system to maintain stable and reliable detection accuracy even when faced with differences in motor characteristics, changes in operating temperature, or current drift caused by long-term wear. This implementation provides the entire stall detection system with a high-precision adjustable threshold setting capability, further enhancing the applicability and engineering practicality of electronic limit control.

[0041] like Figure 3 As shown, a method for detecting stalled DC motors in projectors is applied to a system for detecting stalled DC motors in projectors. The detection method includes: S10. After the main control module issues the start command for the DC motor, the surge shielding process of the start-up phase is entered and executed. The surge shielding process of the start-up phase refers to a short-term current characteristic filtering process performed by the system on the motor operating parameters after the DC motor receives the start command from the main control module in order to avoid interference from the excitation current generated at the moment of start-up on the stall detection. This process determines whether to end by monitoring whether the current sampling value collected during the motor start-up tends to stabilize.

[0042] S20. If the surge shielding process is detected to have ended, the average operating current obtained during the surge shielding process is updated. Based on the updated average operating current and the historical peak stall current, the corresponding real-time dynamic stall threshold is calculated using an adaptive adjustment model. The real-time dynamic stall threshold is used to determine the corresponding reference voltage. The average operating current is the average current value that characterizes the normal load state of the motor, calculated by the system based on multiple sampling results after the current sequence continuously collected during the surge shielding process enters the stable region. It is used as the basic input for the subsequent threshold model. The historical peak stall current is a record of the peak current generated by the motor when it has stalled in the past, which is stored internally by the system. This record can be gradually updated through multiple stall events to adapt to the stall current drift caused by mechanical wear, temperature rise changes, and load changes. The adaptive adjustment model is a dynamic threshold calculation mechanism built internally by the system based on variables such as the average operating current and the historical peak stall current. This model can generate a stall judgment threshold that is more consistent with the current motor state based on input features, historical data, and preset adjustment strategies, so that projectors with different structures or usage environments can obtain a more suitable detection sensitivity. The real-time dynamic stall threshold is a current threshold calculated by the adaptive adjustment model at a specific point in time to distinguish between normal operation and stall conditions. This threshold is instantaneous and is constantly updated as the operating current and historical stall data change, making the detection results more consistent with the actual mechanical conditions.

[0043] S30. The working voltage in the drive circuit is acquired in real time, and the working voltage is compared with the reference voltage to generate a corresponding comparison signal for controlling whether the projection lens stops rotating. The reference voltage is a voltage signal used by the comparator or equivalent circuit for reference. It corresponds one-to-one with the real-time dynamic stall threshold and is mapped from the current threshold. It is used as a comparison parameter to determine whether the motor has entered the stall side.

[0044] S40. Update the adaptive adjustment model based on the comparison signal.

[0045] For example, in a small projector, the DC motor experiences a significant current fluctuation upon startup. Therefore, the system first enters a surge shielding process. After a few milliseconds, the current gradually stabilizes, and the system calculates the average operating current to be 80mA, while the historical peak stall current is currently recorded as 150mA. The adaptive adjustment model calculates a real-time dynamic stall threshold of 130mA based on these two inputs and maps it to an equivalent reference voltage. If the lens moves normally at this time, the operating voltage remains below the reference voltage, and the comparison signal remains in normal operating condition. However, when the lens moves to the end of the structure, causing a sudden increase in load, the operating voltage spikes above the reference voltage, and the comparison signal immediately switches to an abnormal state. The main control module then shuts down the drive output, the lens stops moving, and the system updates the historical peak stall current based on this stall behavior, making subsequent judgments more accurate.

[0046] Furthermore, the surge shielding process includes the following steps: S101. When the main control module issues a start command for the DC motor, the corresponding start time information is recorded, and the operating voltage data in the drive circuit is acquired according to a preset sampling period starting from the moment corresponding to the start time information. The start time information is a reference time recorded by the system's internal timer at the same moment the main control module issues the DC motor start command. It is used to mark the start time of the start process and ensure that subsequent sampling periods are precisely aligned with the actual start moment of the motor. The operating voltage data is the instantaneous voltage value obtained by periodically and in real-time acquiring the voltage drop formed by the current change in the motor drive circuit. It reflects the load change of the motor at each sampling point after startup. The preset sampling period is the voltage acquisition interval set by the system to ensure that the acquisition frequency is high enough to capture the rapidly fluctuating current changes during the startup phase, while keeping the acquired load within a controllable range.

[0047] S102. The operating voltage data acquired in each sampling period is sequentially converted into current sampling values ​​for the startup phase, and the current sampling values ​​are accumulated to form a current sampling sequence for the startup phase. The startup time information is a reference time recorded by the system's internal timer at the same moment the main control module issues the DC motor startup command. This time is used to mark the starting point of the startup process and ensure that subsequent sampling periods are precisely aligned with the actual startup moment of the motor. The operating voltage data is the instantaneous voltage value obtained by periodically and in real-time acquiring the voltage drop caused by the current change in the motor drive circuit. It reflects the load change of the motor at each sampling point after startup. The preset sampling period is the voltage acquisition interval set by the system to ensure that the acquisition frequency is high enough to capture the rapidly fluctuating current changes during the startup phase, while keeping the acquired load within a controllable range.

[0048] Specifically, in this system, the operating voltage data acquired in each sampling period is converted into current sampling values ​​during the startup phase because the projector does not have a directly integrated current sensor. Instead, it indirectly measures the current magnitude by establishing a current-voltage correspondence through a sampling resistor. The current sampling resistor already carries the entire operating current of the motor in the circuit, and its voltage change stably and linearly reflects the current trend. Therefore, acquiring the voltage and converting it using a known resistance value is more reliable, lower in cost, and requires less space than directly adding a current sensor. Furthermore, the motor current changes very rapidly during startup. Direct current sampling would require an additional high-speed current detection chip to meet the bandwidth requirements, while voltage sampling offers advantages in response speed, anti-interference capability, and circuit complexity. For these reasons, the system selects sampling voltage and converting it into a current value as the current characteristic during startup, instead of using an additional current sensor.

[0049] S103. Based on the current sampling sequence, determine whether the surge shielding process meets the preset termination condition. After acquiring continuous operating voltage data, the system converts these voltage values ​​into corresponding current sampling values ​​according to the sampling resistor parameters of the motor drive circuit. The conversion method relies on the linear relationship between current and voltage, ensuring that the voltage signal at each moment reflects the instantaneous load state of the motor in the form of current. As sampling continues, these current sampling values ​​are accumulated by the system in chronological order, forming a current sampling sequence for the startup phase. This sequence completely records the current change trajectory of the motor from the moment of startup to the point where operation tends to stabilize. Whether the surge shielding process meets the preset termination condition is determined by the system based on the changing trend of the current sampling sequence, judging whether the current motor operation has escaped the influence of the excitation current at the moment of startup and entered a relatively stable state. The preset termination condition is usually composed of multiple factors such as the current change rate, the duration of sampling points, and the sampling time, used to determine whether the current fluctuation has dropped to the normal operating range.

[0050] S104. If the surge shielding process is determined to meet the preset termination condition, the corresponding average operating current is calculated based on the current sampling sequence during the startup phase. When the system determines that the surge shielding process has ended, it means that the sampling sequence has contained sufficiently reliable stable current information. At this time, the system calculates the average operating current based on the current sampling sequence during the startup phase, so that the generation of subsequent dynamic thresholds is based on the real and stable motor operating load, and will not be affected by the surge at the moment of startup.

[0051] Specifically, after determining that the surge fluctuations during motor startup have attenuated and the sampling sequence has entered a stable range, the system extracts continuous sampling points corresponding to the stable segment from the current sampling sequence of the entire startup phase. The current values ​​of these sampling points are then summed and normalized to ensure that the calculated average current accurately reflects the steady-state operating characteristics of the motor under normal load. To avoid the influence of occasional noise on the results, the system performs a lightweight filtering process on the sampling sequence, such as using a sliding window averaging or amplitude limiting correction algorithm, to eliminate the offset caused by sudden points to the overall average value. This ensures that the final average operating current has sufficient smoothness and faithfully reflects the true current level of the motor during stable operation, thus providing a reliable basis for the subsequent adaptive calculation of the stall threshold.

[0052] Furthermore, the step of determining whether the surge shielding process meets the preset termination conditions based on the current sampling sequence includes: S1031. Based on the current sampling sequence, determine the current sampling value I(t) of the current sampling period and the current sampling value I(t-1) of the previous sampling period, as well as the time difference Δt between the time point corresponding to the current sampling period and the start-up time information. The current sampling value I(t) of the current sampling period represents the instantaneous current value obtained by the system at the t-th sampling time point through voltage sampling and resistance conversion, while the current sampling value I(t-1) of the previous sampling period corresponds to the current value recorded in the immediately preceding sampling period. These two adjacent data points together describe the short-time variation amplitude of the current in the continuous sampling period. The time difference Δt between the time point corresponding to the current sampling period and the start-up time information is the length of time experienced by the motor after startup, calculated by the system through an internal timer, used to reflect whether the motor's operation process during the startup phase has entered the stable region. S1032. Calculate the rate of change of current dl, the formula is: dl = I(t) - I(t-1); The current sample value I(t) of the current sampling period represents the instantaneous current value obtained by the system through voltage sampling and resistance conversion at the t-th sampling time point, while the current sample value I(t-1) of the previous sampling period corresponds to the current value recorded in the immediately preceding sampling period. These two adjacent data points together describe the short-time change amplitude of the current in the continuous sampling period. The time difference Δt between the time point corresponding to the current sampling period and the start-up time information is the length of time the motor has experienced after starting, calculated by the system through the internal timer, and is used to reflect whether the motor's running process in the start-up phase has entered the stable region; S1033. When the time difference Δt reaches the preset shielding duration, or when the current change rate dl changes from positive to negative and the number of sequences in the continuous current sampling sequence reaches the preset number of continuous samples, the surge shielding process is determined to have met the preset termination condition. The preset shielding duration is the minimum shielding time window set by the system to avoid the startup excitation current from mistakenly triggering the stall judgment. During this duration, the system will not execute the stall judgment, and the motor drive will not be interrupted even if the current fluctuates abnormally. The preset number of continuous samples is the number of conditions used by the system to determine whether the current trend is stable. Only when the current change rate no longer shows an obvious upward trend after several consecutive sampling cycles and turns to a negative change is the motor considered to have entered the stable operating range from the startup stage. If the time difference Δt has exceeded the preset shielding duration, the system directly considers the surge shielding process to have ended. If dl changes from positive to zero or negative and maintains at least the preset number of continuous sampling points before Δt reaches the shielding duration, the system can still determine in advance that the motor has entered a stable state, avoiding the delay in threshold calculation due to the fixed shielding time being too long.

[0053] Furthermore, the step of calculating the corresponding real-time dynamic stall threshold based on the updated average operating current and historical peak stall current using an adaptive adjustment model includes: S201. Based on the updated average operating current and historical stall peak current, corresponding input variables are constructed and input into the adaptive adjustment model. Essentially, this combines the motor's current operating state with records of past stall events, using an algorithmic model to generate a judgment threshold that more closely reflects actual mechanical load changes. Constructing input variables means that after the surge shielding process, the average operating current calculated in the current cycle and the historical stall peak current accumulated over time are fed into the adaptive adjustment model as feature parameters. These two parameters respectively characterize the motor's current low-load stability and high-load limit under stall conditions, serving as the main basis for the model's threshold estimation. The adaptive adjustment model is a dynamic algorithm framework capable of generating predicted currents based on input features, operating trends, and internal weight configurations. It continuously updates internal parameters according to the motor's actual operating conditions, making the generated threshold more consistent with the system's current real physical environment.

[0054] S202. Based on the adaptive adjustment model, corresponding current prediction values ​​are generated through preset weighted calculation rules. The preset weighted calculation rules are the operational logic used internally by the adaptive adjustment model, which combines the average operating current with the historical peak stall current according to a certain proportion, bias, or functional relationship, enabling the model to calculate representative current prediction values ​​under different operating conditions. This current prediction value is an estimate of the current trend of the motor before it may stall, reflecting the current range that the motor may reach between normal operation and extreme operation.

[0055] Specifically, the adaptive adjustment model internally pre-defines a set of dynamically updatable weighting coefficients to describe the contribution ratio of the average operating current and the historical peak stall current in the overall stall trend judgment. When the system enters this step, it records the latest calculated average operating current as the fundamental quantity reflecting the current load stability, while considering the historical peak stall current as a representation of the motor's extreme load capacity during previous stall events. The weighted calculation rule combines these two quantities using a weighted function combination (e.g., linear weighting, exponential weighting, or decaying weighting), and introduces bias corrections when necessary, enabling the model to calculate the expected current level that the motor might reach under current operating conditions before actual stalling occurs. This predicted current value retains the immediacy of the current operating state while also considering the reliability of historical stall records, thus forming a dynamic current trend estimate that can adapt to mechanical wear, ambient temperature changes, and load characteristic drift, serving as an important benchmark for subsequent calculation of the dynamic stall threshold.

[0056] S203. Calculate and generate the corresponding preliminary dynamic stall threshold based on the current prediction value and the preset safety compensation coefficient. The safety compensation coefficient is a compensation parameter added to the model to avoid the stall threshold being too sensitive or not sensitive enough due to fluctuations in the current prediction value caused by structural differences, assembly errors or environmental changes. It is usually set by the system during the commissioning phase and can be dynamically adjusted during long-term operation.

[0057] S204. Apply upper and lower limit constraints to the preliminary dynamic stall threshold to generate the corresponding actual dynamic stall threshold. After the system generates the preliminary dynamic stall threshold based on the current prediction value and the safety compensation coefficient, in order to prevent the threshold from jumping unreasonably due to prediction deviation or extreme data, it is also necessary to introduce upper and lower limit constraints to limit the threshold. The upper and lower limit constraints are preset by the system to ensure that the final generated actual dynamic stall threshold is always within the acceptable judgment range of the motor, so that the detection process is neither misjudged nor missed, thereby improving the stability of the overall algorithm.

[0058] Specifically, applying upper and lower limits to the initial dynamic stall threshold is to prevent excessively large or small jumps in the threshold due to model prediction bias, occasional load fluctuations, or noise interference, which could affect the stability of stall detection. The system establishes a set of dynamically updatable upper and lower limit ranges for the threshold during factory commissioning or long-term operation. These ranges are typically determined based on the motor's rated current, actual mechanical limit resistance, ambient temperature changes, and historical stall data statistics. After obtaining the initial dynamic stall threshold, the system first compares it with the preset upper limit. If the threshold exceeds the upper limit, it is truncated to the upper limit to avoid missed stall detections due to overly high predictions; conversely, if the threshold is below the lower limit, it is raised to the lower limit to prevent frequent misjudgments due to an excessively low threshold. Through this interval-based constraint method, the system ensures that the final actual dynamic stall threshold fluctuates within a controllable range, accurately reflecting the current actual mechanical state while maintaining the continuity and robustness of the detection process, providing a stable and reliable reference input for subsequent voltage comparisons and stall detection.

[0059] Furthermore, the step of calculating and generating the corresponding preliminary dynamic stall threshold based on the predicted current value and the preset safety compensation coefficient includes: S2031. The predicted current value is proportionally calculated with a preset safety compensation coefficient to generate the corresponding compensation current value; the current trend predicted by the model is further corrected into an engineering judgment value that can be used for actual stall determination. The predicted current value is the theoretical current level that the motor may reach before approaching stall, calculated by the adaptive adjustment model based on the current average operating current and historical peak stall current. However, since the motor may deviate significantly under different operating conditions, temperatures, mechanical wear states, or load fluctuations, the system needs to introduce a safety compensation coefficient to adjust it. The safety compensation coefficient is a preset multiplier parameter used to provide the necessary margin for the predicted value based on actual test experience or long-term system operating data, enabling the system to identify risk signals earlier before stall occurs. By proportionally calculating the predicted current value with this compensation coefficient, the compensation current value can be obtained. The compensation current value is equivalent to a corrected current value that is closer to the actual stall conditions, after further considering differences in the machine structure, changes in mechanical friction, and even changes in ambient temperature on the basis of the theoretical predicted value.

[0060] Specifically, the proportional calculation between the predicted current value and the preset safety compensation coefficient addresses potential deviations in the predicted value due to motor aging, transmission structure wear, environmental temperature changes, or assembly tolerances. This provides an engineering-based risk compensation for the predicted value before entering the stall judgment stage. Upon entering this step, the system treats the predicted current value as a baseline and uses the safety compensation coefficient as a multiplier to amplify or reduce this baseline value. The proportional calculation is performed by multiplying the two values. This multiplier is typically a slight amplification factor greater than 1, ensuring the compensation result is slightly higher than the uncompensated predicted value, thus guaranteeing a necessary safety margin for stall judgment. In certain special cases where the system exhibits an oversensitivity tendency, the compensation coefficient can be set slightly less than 1 to make the overall judgment smoother and less prone to false triggering. During the calculation, the system processes the multiplication result with fixed precision to ensure the compensated current value remains within the acceptable effective range for the motor and maintains numerical compatibility with the subsequent linear adjustment formula. Through this proportional operation based on multiplication, the system can obtain a compensation current value that reflects the actual working risk with minimal computational complexity, making the subsequent threshold generation more robust and reliable in engineering.

[0061] S2032. Based on the compensation current value, calculate the corresponding preliminary dynamic stall threshold Ith according to the preset linear proportional adjustment rule. The calculation formula is as follows: Ith = Ka × Ic + Ba; Where Ka is the proportional coefficient, Ic is the compensation current value, and Ba is the bias coefficient; after obtaining the compensation current value, the system generates the final preliminary dynamic stall threshold through a preset linear proportional adjustment rule. The linear proportional adjustment rule is a threshold generation method constructed through a simple linear function relationship, which can map the compensation current to the stall judgment threshold space in a clear and controllable manner. The proportional coefficient Ka used in the linear model represents the growth rate of the compensation current's contribution to the threshold, usually determined by factors such as motor type, load characteristics, and the stress condition of the transmission structure; the bias coefficient Ba is the basic offset required for the threshold based on the compensation current, used to compensate for zero-point offset, aging errors, or calibration errors that occur after long-term system operation. By inputting the compensation current value Ic into the linear model according to the formula Ith=Ka×Ic+Ba, the system can generate a preliminary dynamic stall threshold that reflects the actual stall characteristics of the motor, serving as the basis for the next step of upper and lower limit constraint processing.

[0062] Furthermore, the step of comparing the operating voltage with the reference voltage to generate a corresponding comparison signal for controlling whether the projection lens stops rotating includes: S301. The operating voltage is compared with the reference voltage to calculate the corresponding voltage difference; this is a crucial process for the system to identify whether a DC motor has entered a stalled state. The operating voltage is an electrical quantity that reflects the actual load of the motor in real time, obtained through the instantaneous voltage change formed on the sampling resistor by the current in the motor drive circuit; the reference voltage is mapped from the real-time dynamic stall threshold and is used to represent the dividing point for the system to judge stall. When the system calculates using the operating voltage and reference voltage obtained within the same sampling period, a voltage difference is obtained, which reflects the degree of deviation of the current motor current from the stall critical point. If the motor is operating under a light load, the voltage difference is usually small; if the motor is obstructed or close to its travel limit, the voltage difference will increase rapidly. Therefore, the voltage difference is the most basic discrimination signal for judging the motor state.

[0063] S302. Based on the current sampling sequence, the corresponding trend is determined. Based on the voltage difference characteristics and the trend, a corresponding comparison signal is generated. The system also calculates the motor's trend over a continuous sampling period by combining the current sampling sequence. This trend reflects the direction and speed of current change over time, helping the system distinguish between short-term load fluctuations and actual near-stalling behavior. For example, when the trend continuously rises and increases along with the voltage difference, it usually means the motor is rapidly approaching a stall state; if the trend occasionally rises but immediately falls back, it usually indicates normal load changes. After obtaining the trend and voltage difference characteristics, the system generates a comparison signal through a feature combination algorithm to more accurately describe the motor's current state.

[0064] Specifically, in each sampling cycle, the system first obtains the voltage difference between the current operating voltage and the reference voltage, and then correlates this voltage difference with the differences of the previous cycle or multiple cycles to form trend information reflecting the rate, direction, and magnitude of voltage change. Subsequently, the system uses a preset pattern matching logic to jointly judge the voltage difference amplitude and trend data: if the voltage difference is in a low range and the trend is stable or decreasing, the current load change is determined to be a normal operating fluctuation; if the voltage difference is in a critical range and accompanied by a continuous upward trend, the system marks this state as suspected stall; if the voltage difference rapidly exceeds a threshold and the trend is steep, it is directly determined to be approaching stall or about to stall. During this process, the system encodes the state results into digital signals according to the defined threshold range and trend criteria. For example, a low level indicates a normal state, and a high level indicates a suspected stall or stall state, thereby generating the final comparison signal. This allows the main control module to read these digital outputs with minimal processing delay and promptly trigger subsequent protection actions.

[0065] S303. Convert the comparison signal into a corresponding operating status identifier. The operating status identifier includes at least normal operating status and suspected stall status. After classification processing, the comparison signal is mapped to an operating status identifier, which is used to visually indicate whether the motor is in normal operating status or suspected stall status. Normal operating status indicates that the voltage difference is small, the trend is not continuously increasing, and it has not approached the stall range. Suspected stall status indicates that the voltage difference has reached a partial critical range or the trend is continuously increasing but has not yet fully met the stall conditions, so that the system can take risk prevention and control measures in advance.

[0066] S304. Determine the current rotation direction of the projection lens. Based on the rotation direction and trend, determine whether the DC motor is actually stalled. If so, the main control module controls the motor drive chip to shut off the drive output to stop the lens rotation. To further confirm whether stalling has actually occurred, the system also considers the rotation direction of the projection lens. The rotation direction is usually recorded in real time by the main control module based on the current focusing command and is a necessary condition for determining the direction of motor force, load direction, and stall logic. For example, when the lens is in forward focusing, an upward trend accompanied by an increase in voltage difference indicates approaching the forward mechanical limit; if it is in reverse focusing, the same characteristics may indicate approaching the reverse limit.

[0067] Finally, when the system determines that the motor has entered a stall state based on the rotation direction and trend, the main control module immediately sends a shutdown command to the motor drive chip to cut off the drive output instantly, so as to avoid the motor being continuously subjected to force, which could cause damage to the lens mechanism or further aggravate the jamming, and ensure that the lens is stably stopped at a safe position at the travel boundary.

[0068] Furthermore, the step of updating the adaptive adjustment model based on the comparison signal includes: S401. Based on the comparison signal, determine the corresponding voltage difference amplitude characteristics, false positive / false negative characteristics, and upper / lower limit drift characteristics. The comparison signal is generated by comparing the operating voltage and the reference voltage and analyzing their trends, containing rich information about the motor's current operating status. The voltage difference amplitude characteristic refers to the voltage difference amplitude range in the comparison signal that reflects the strength of real-time load changes in the motor. It usually fluctuates with changes in lens load, stroke position, and mechanism resistance, and is an important quantitative indicator reflecting the degree to which the motor approaches stall. The false positive / false negative characteristics are the time-dimensional characteristics of the comparison signal. By monitoring whether the comparison signal exhibits critical jumps within multiple sampling periods, whether it remains in a suspected stall state without ultimately triggering a true stall, or whether a stall occurs but the comparison signal response is lagging, it reflects whether the current threshold setting is overly sensitive or insensitive. The upper / lower limit drift characteristics are used to reflect the changing trend of the overall current distribution area of ​​the motor due to factors such as temperature changes, mechanical wear, and electrical aging during long-term operation. It indicates whether the maximum feasible range of the dynamic stall threshold needs to be adjusted to ensure that the model can maintain stable judgment capabilities at different stages.

[0069] S402. Based on the voltage difference amplitude characteristics, generate a peak current estimate for updating historical peak current parameters. Specifically, the process of generating the peak current estimate based on the voltage difference amplitude characteristics is a key step in the system's back-calculation and quantification of potential peak currents during the current operation. The voltage difference amplitude characteristics describe the continuous increase in operating voltage as the motor approaches the stall stage. This characteristic typically originates from the cumulative change in voltage amplitude across the sampling resistor and reflects the current increase experienced by the motor as it approaches stall under current load conditions. After entering this step, the system converts the voltage difference amplitude into a corresponding current amplitude increment based on the motor's known electrical model (e.g., resistance, inductance, drive capability) and the linear conversion relationship between voltage difference and current. Simultaneously, the system combines the current peak values ​​recorded in historical stall events with a prediction model such as incremental iteration formulas, exponential smoothing formulas, or dynamic weight fusion formulas to superimpose the current current amplitude increment onto the historical peak current, thereby generating a new peak current estimate. This estimate not only comprehensively considers the actual voltage response during the current motor's approach to the stall phase but also incorporates the electrical characteristics of previous stall occurrences, enabling the parameters to gradually converge to the peak current corresponding to the actual mechanical limit load over multiple operating cycles. Through this dynamic estimation method driven by amplitude characteristics, the system can continuously correct historical records even under stall current drift caused by structural wear, temperature rise changes, or load differences, ensuring that the stall peak current parameters remain consistent with the motor's actual operating state and improving the accuracy of dynamic threshold calculation.

[0070] S403. Based on the characteristics of false positives and false negatives, a sensitivity correction amount is generated to adjust the safety compensation coefficient. Specifically, the characteristics of false positives and false negatives originate from the behavior of the comparison signal in multiple consecutive sampling periods. By analyzing whether the comparison signal frequently enters a suspected stall state without actual stalling, or exhibits response lag when stalling occurs, the system can identify whether the current threshold setting is too high or too low. When the comparison signal prematurely transitions to a suspected stall state within multiple periods, it indicates that the system's stall judgment is too sensitive. In this case, the sensitivity correction amount will be calculated as a negative adjustment value to reduce the safety compensation coefficient. Conversely, when the comparison signal fails to reach the expected response in time at the moment of stalling, or when there is no obvious trend indication before stalling occurs, the system will calculate the sensitivity correction amount as a positive adjustment value to increase the safety compensation coefficient, thereby enhancing the timeliness and reliability of the judgment. In the specific calculation process, the system quantifies factors such as the number of false positives, the number of false negatives, the trend response delay time, and the critical dwell time of the comparison signal. These factors are then integrated into a continuous adjustment quantity using proportional weights or an exponential decay function. This allows the sensitivity correction to be applied smoothly and gradually to the safety compensation coefficient, without causing abrupt changes. Through this dynamic adjustment mechanism based on real-time behavioral feedback, the system can automatically adapt to different motor loads, structural wear levels, temperature environments, or lens movement patterns, thus maintaining reasonable sensitivity in stall detection throughout the entire equipment lifecycle.

[0071] S404. Based on the upper and lower limit drift characteristics, generate range update quantities for correcting the dynamic threshold upper and lower limit constraint intervals. Specifically, the upper and lower limit drift characteristics reflect the trend of a slow shift in the overall operating current range of the motor over time under conditions such as temperature rise, wear, changes in lubrication status, structural component aging, or assembly loosening. When entering this step, the system first analyzes the degree of deviation between the current operating cycle and the average operating current, peak value estimate, and trend characteristics over multiple historical cycles. By identifying whether these deviations are continuously accumulating, unidirectional, and whether the rate of change exceeds the normal fluctuation range, it determines whether the environment or structure is causing the overall operating current range of the motor to drift. Subsequently, the system converts these drift quantities into correction quantities for the dynamic threshold interval according to a preset algorithm, including raising or lowering the upper limit of the interval and tightening or widening the lower limit, so as to maintain the entire threshold interval always covering the actual operating range of the motor. When generating the range update quantity, the system uses linear proportional, exponential smoothing, or rate-weighted methods to perform numerical calculations based on the direction and magnitude of the drift trend, so that the update quantity can act smoothly rather than abruptly on the upper and lower limit intervals. For example, when the overall current of the motor decreases after prolonged operation, causing the estimated stall peak value to remain below the historical average for an extended period, the system generates a negative range update, shifting the threshold range downwards. Conversely, when rising temperature or increased friction causes the overall current distribution to rise, a positive range update is generated, shifting the threshold range upwards. Through this continuous update mechanism based on drift trends, the system can dynamically maintain consistency between the threshold range and actual motor behavior throughout the equipment's lifecycle. This avoids misjudgments or missed judgments due to outdated range settings, ensuring that stall detection maintains stable and reliable judgment accuracy in different operating environments.

[0072] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A DC motor stall detection system for a projector, characterized in that, The projector DC motor stall detection system includes a main control module, a projection lens, a DC motor, a motor drive module, and a sampling comparison module. The drive signal output terminal of the motor drive module is connected to the DC motor, and the DC motor is connected to the projection lens to control the rotation of the projection lens and form a corresponding drive circuit. The detection signal input terminal of the sampling comparison module is used to obtain the working voltage in the drive circuit. The comparison signal output terminal of the sampling comparison module is connected to the signal input terminal of the main control module. The sampling comparison module generates a corresponding comparison signal by comparing the working voltage with a preset reference voltage, and outputs it to the main control module through the comparison signal output terminal of the sampling comparison module. The control signal output terminal of the main control module is connected to the control signal input terminal of the motor drive module. When the comparison signal indicates that the DC motor is stalled, the main control module generates a corresponding control signal to control the motor drive module to stop driving the DC motor, thereby causing the projection lens to stop rotating.

2. The projector DC motor stall detection system according to claim 1, characterized in that, The sampling and comparison module includes a comparator chip U2 and a sampling resistor RG42. The first end of the sampling resistor RG42 is connected to the power supply, and the second end of the sampling resistor RG42 is connected to the power input terminal of the motor drive module. The common node between the second end of the sampling resistor RG42 and the power input terminal of the motor drive module is connected to the non-inverting input terminal of the comparator chip U2. The inverting input terminal of the comparator chip U2 obtains the corresponding reference voltage, and the signal output terminal of the comparator chip U2 is connected to the signal input terminal of the main control module.

3. The projector DC motor stall detection system according to claim 2, characterized in that, The sampling comparison module further includes adjustable resistors RG38 and RG39. The first end of the adjustable resistor RG38 is connected to the power supply, the second end of the adjustable resistor RG38 is connected to the first end of the adjustable resistor RG39, the second end of the adjustable resistor RG39 is grounded, and the common node between the second end of the adjustable resistor RG38 and the first end of the adjustable resistor RG39 is connected to the inverting input terminal of the comparator chip U2.

4. A method for detecting stall in a projector's DC motor, characterized in that, The detection method, applied to the projector DC motor stall detection system as described in any one of claims 1-3, includes: After the main control module issues the start command for the DC motor, it enters and executes the surge shielding process during the start-up phase. If the surge shielding process is detected to have ended, the average operating current obtained in the surge shielding process is updated. Based on the updated average operating current and the historical peak current, the corresponding real-time dynamic stall threshold is calculated based on the adaptive adjustment model. The real-time dynamic stall threshold is used to determine the corresponding reference voltage. The operating voltage in the drive circuit is acquired in real time, and the operating voltage is compared with the reference voltage to generate a corresponding comparison signal, which is used to control whether the projection lens stops rotating. The adaptive adjustment model is updated based on the comparison signal.

5. The method for detecting stall in a projector DC motor according to claim 4, characterized in that, The surge shielding process includes the following steps: When the main control module issues a start command for the DC motor, it records the corresponding start time information and obtains the working voltage data in the drive circuit from the moment corresponding to the start time information according to a preset sampling period. The operating voltage data acquired in each sampling period is sequentially converted into current sampling values ​​for the startup phase, and the current sampling values ​​are accumulated to form a current sampling sequence for the startup phase. Based on the current sampling sequence, determine whether the surge shielding process meets the preset termination condition; If the surge shielding process is determined to meet the preset termination conditions, the corresponding average operating current is calculated based on the current sampling sequence of the startup phase.

6. The method for detecting stall in a projector DC motor according to claim 5, characterized in that, The step of determining whether the surge shielding process meets the preset termination condition based on the current sampling sequence includes: Based on the current sampling sequence, determine the current sampling value I(t) of the current sampling period and the current sampling value I(t-1) of the previous sampling period, as well as the time difference Δt between the time point corresponding to the current sampling period and the start time information. The current change rate dl is calculated using the formula: dl = I(t) - I(t-1); When the time difference Δt reaches the preset shielding duration, or when the current change rate dl changes from positive to negative and the number of sequences in the current sampling sequence reaches the preset number of consecutive samples, it is determined that the surge shielding process has met the preset termination condition.

7. The method for detecting stall in a projector DC motor according to claim 4, characterized in that, The step of calculating the corresponding real-time dynamic stall threshold based on the updated average operating current and historical peak stall current using an adaptive adjustment model includes: Based on the updated average operating current and the historical peak current, the corresponding input variables are constructed and input into the adaptive adjustment model; Based on the adaptive adjustment model, the corresponding current prediction value is generated through a preset weighted calculation rule; Based on the predicted current value and the preset safety compensation coefficient, the corresponding preliminary dynamic stall threshold is calculated and generated. Upper and lower limits are imposed on the preliminary dynamic blocking threshold to generate the corresponding actual dynamic blocking threshold.

8. The method for detecting stall in a projector DC motor according to claim 7, characterized in that, The step of calculating and generating the corresponding preliminary dynamic stall threshold based on the predicted current value and the preset safety compensation coefficient includes: The predicted current value is proportionally calculated with a preset safety compensation coefficient to generate a corresponding compensation current value. Based on the compensation current value, the corresponding preliminary dynamic stall threshold Ith is calculated according to the preset linear proportional adjustment rule. The calculation formula is as follows: Ith = Ka × Ic + Ba; Where Ka is the proportional coefficient, Ic is the compensation current value, and Ba is the bias coefficient.

9. The method for detecting stall in a projector DC motor according to claim 5, characterized in that, The step of comparing the operating voltage with the reference voltage to generate a corresponding comparison signal for controlling whether the projection lens stops rotating includes: The operating voltage is compared with the reference voltage to calculate the corresponding voltage difference; The corresponding trend of change is determined based on the current sampling sequence, and a corresponding comparison signal is generated based on the voltage difference characteristics and the trend of change. The comparison signal is converted into a corresponding operating status identifier, which includes at least a normal operating status and a suspected stalled status. The current rotation direction of the projection lens is determined. Based on the rotation direction and the trend of change, it is determined whether the DC motor is in an actual stall state. If so, the main control module controls the motor drive chip to shut off the drive output to stop the lens rotation.

10. A method for detecting stall in a projector's DC motor according to claim 7, characterized in that, The step of updating the adaptive adjustment model based on the comparison signal includes: Based on the comparison signal, determine the corresponding voltage difference amplitude characteristics, false positive and false negative characteristics, and upper and lower limit drift characteristics; Based on the voltage difference amplitude characteristics, a peak current estimate is generated to update the historical peak current parameters. Based on the aforementioned false positive and false negative characteristics, a sensitivity correction amount is generated to adjust the safety compensation coefficient; Based on the upper and lower limit drift characteristics, a range update amount is generated to correct the dynamic threshold upper and lower limit constraint interval.

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