Vacuum valve step motor thermal protection method, step motor and medium

Abstract

The present disclosure provides a vacuum valve stepper motor heat protection method, a stepper motor and a medium; wherein the method comprises: synchronously sampling the instantaneous current values of two-phase windings of the stepper motor at a preset sampling period; when each sampling period arrives, determining a first monitoring level corresponding to a first time scale according to the instantaneous current sampling values of each phase winding, determining a second monitoring level corresponding to a second time scale according to the window thermal load intensity values of each phase winding in a preset time window, and determining a third monitoring level corresponding to a third time scale according to the instantaneous current sampling values of each phase winding and the historical thermal integral residual values retained in the last sampling period; and performing a target heat protection action according to the first monitoring level, the second monitoring level and the third monitoring level of each phase winding to perform heat protection on the stepper motor. The present disclosure can improve the flexibility and controllability of motor heat protection.

Description

Technical Field

[0001] This disclosure relates to the field of motor thermal protection technology, and in particular to a stepper motor thermal protection method for a vacuum valve, the stepper motor, and the medium. Background Technology

[0002] Vacuum valves are core actuators widely used in semiconductor manufacturing equipment, photovoltaic equipment, and precision control in the chemical industry. They control the vacuum level of process chambers by adjusting the valve opening. Vacuum valves typically use stepper motors as their power source, and the valve position is adjusted by controlling the rotation angle of the stepper motor. The operating environment of vacuum valves places special requirements on the thermal management of stepper motors.

[0003] Thermal protection technologies related to vacuum valve stepper motors typically use thermistors for overcurrent limiting, passively increasing resistance based on the component's own temperature rise, or using overcurrent protection chips to monitor current amplitude and shut down when the limit is exceeded. The protection logic of these technologies is too simplistic, and their flexibility and controllability have significant room for improvement. Summary of the Invention

[0004] In view of this, the purpose of this disclosure is to provide a stepper motor thermal protection method, a stepper motor and a medium for a vacuum valve, so as to provide a flexible and controllable stepper motor thermal protection technology for vacuum valves.

[0005] In a first aspect, embodiments of this disclosure provide a method for thermal protection of a stepper motor in a vacuum valve. The method includes: synchronously sampling the instantaneous current values ​​of two-phase windings of a stepper motor at a preset sampling period; at the end of each sampling period, determining a first monitoring level corresponding to a first time scale based on the instantaneous current sampling values ​​of each phase winding, determining a second monitoring level corresponding to a second time scale based on the window thermal load intensity values ​​of each phase winding within a preset time window, and determining a third monitoring level corresponding to a third time scale based on the instantaneous current sampling values ​​of each phase winding and the historical thermal integral residual value retained from the previous sampling period; wherein the window thermal load intensity value is the cumulative value of the square of the instantaneous current sampling value over time; and executing a target thermal protection action based on the first monitoring level, the second monitoring level, and the third monitoring level of each phase winding to provide thermal protection for the stepper motor.

[0006] Secondly, this disclosure provides a stepper motor, including a processor and a memory. The memory stores machine-executable instructions that can be executed by the processor. The processor executes the machine-executable instructions to implement the stepper motor thermal protection method for the vacuum valve described above.

[0007] Thirdly, embodiments of this disclosure provide a computer-readable storage medium storing computer-executable instructions. When the computer-executable instructions are invoked and executed by a processor, the computer-executable instructions cause the processor to implement the aforementioned stepper motor thermal protection method for a vacuum valve.

[0008] The embodiments disclosed herein bring the following beneficial effects: The aforementioned stepper motor thermal protection method for vacuum valves, the stepper motor, and the medium, by constructing a multi-time-scale judgment architecture, determines the target thermal protection action based on the quantified protection level of each time scale. This enables the protection method to have quantifiable traceability, a protection mechanism that can balance instantaneous thermal damage and time-accumulated thermal damage, an inherent memory of the winding thermal history, and the ability to form a hardware interlocking closed loop. As a result, the overall thermal protection is transformed from a single, rigid over-limit judgment to a multi-dimensional, memoryable, and quantifiable refined protection, significantly improving the flexibility and controllability of motor thermal protection.

[0009] Other features and advantages of this disclosure will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the disclosure. The objects and other advantages of this disclosure are realized and obtained through the structures particularly pointed out in the description, claims and drawings.

[0010] To make the above-mentioned objects, features and advantages of this disclosure more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the specific embodiments of this disclosure or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0012] Figure 1 This is a flowchart of one embodiment of the stepper motor thermal protection method for a vacuum valve in this disclosure; Figure 2 This is a map showing the coverage of the three time scales provided in this embodiment and the corresponding distribution of decisive failure scenarios. Figure 3 A schematic diagram of a stepper motor thermal protection device for a vacuum valve provided in an embodiment of this disclosure; Figure 4 This is a schematic diagram of a stepper motor provided in an embodiment of the present disclosure. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0014] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in this disclosure, claims, and accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” or “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0015] For ease of understanding, the specific process of the embodiments of this disclosure is described below. Please refer to [link / reference]. Figure 1 One embodiment of the stepper motor thermal protection method for the vacuum valve in this disclosure includes: Step S10: Synchronously sample the instantaneous current values ​​of the two-phase windings of the stepper motor at a preset sampling period; The stepper motor of the vacuum valve in this embodiment is a two-phase hybrid stepper motor used in vacuum valves. The vacuum valve can be a vacuum butterfly valve, vacuum ball valve, vacuum diaphragm valve, vacuum gate valve, etc. In this technical field, semiconductor vacuum valves commonly use a two-phase hybrid stepper motor (typically 1.8° / step) combined with microstepping drive, synthesizing orthogonal sinusoidal phase currents via H-bridge topology to achieve position and pressure control. This embodiment is applicable to the two-phase hybrid stepper motor microstepping drive platform used in vacuum valves in semiconductor manufacturing equipment. Through real-time sampling of phase current and multi-timescale thermal modeling, a complete safety closed loop is achieved, from device-level instantaneous protection and mechanical anomaly protection to winding cumulative thermal protection.

[0016] In this embodiment, the stepper motor of the vacuum valve is a two-phase hybrid stepper motor. The two-phase winding current of the motor includes the current flowing through the A-phase winding and the B-phase winding. The stator of the two-phase hybrid stepper motor has two independent winding coils that are spatially 90° out of phase. During operation, sinusoidal current or stepped current with a 90° phase difference are respectively passed through the two-phase windings, and the rotor is driven to rotate by the combined magnetic field of the two-phase current.

[0017] The physical characteristics of two-phase winding currents can include: bidirectionality, meaning the current direction changes with the pulse width modulation (PWM) encoded signal and the motor running direction, and can be either forward or reverse; ripple superposition, meaning that due to PWM modulation, the winding current is not a smooth DC or sine wave, but is superimposed with high-frequency PWM ripple; orthogonality, meaning the two-phase currents are 90° out of phase; and amplitude correlation, meaning the instantaneous amplitudes of the two-phase currents jointly determine the motor's output torque.

[0018] The instantaneous current value of two-phase windings can be detected using different physical principles. These include the sampling resistor method, Hall effect current sensors, current transformers, fluxgate current sensors, or tunnel magnetoresistive current sensors. Each detection method has its own characteristics and can be selected based on factors such as accuracy, cost, and isolation requirements. The signal representation of the two-phase winding current can also differ. Specifically, the two-phase winding current signal can be a differential voltage signal, a single-ended voltage signal, or a digital signal or a PWM duty cycle encoded signal; no specific limitation is made here.

[0019] In this embodiment, when synchronously sampling instantaneous current values, the current values ​​of the A-phase and B-phase windings are sampled simultaneously in the same sampling period, rather than being sampled alternately in a time-division manner. Synchronous sampling can ensure that the phase relationship between the two-phase currents is truly preserved in the sampled data, avoiding phase errors introduced by time-division sampling.

[0020] Synchronous sampling can be achieved through the synchronous sampling mode of a microcontroller's multi-channel analog-to-digital converter (ADC), or by using multiple independent ADCs for parallel sampling, or by using a sample-and-hold circuit with single ADC polling. Multi-channel parallel sampling can also be implemented in a field-programmable gate array (FPGA). The trigger source for synchronous sampling can be a timer compare-match event, a PWM carrier synchronization signal, or an external trigger signal, etc., and is not limited here.

[0021] In this embodiment, the preset sampling period is a pre-set time base for repeatedly sampling current at fixed time intervals, typically in the microsecond or millisecond range, and can be generated by dividing the system clock. Specifically, the time base source for the preset sampling period can include: generation by dividing the system master clock, generation by overflowing a dedicated timer, generation synchronized with the PWM carrier period, or provided by an external clock source, etc., and is not limited here.

[0022] In one implementation, the preset sampling period can be determined based on the PWM carrier frequency, the winding thermal time constant, or the system control cycle. For example, the preset sampling period can be more than twice the PWM carrier frequency to restore the waveform information of the winding current. The preset sampling period can be less than the thermal time constant of the motor winding. The preset sampling period can also be synchronized with the system control cycle or be an integer multiple thereof, so that the current sampling value is aligned with the thermal protection level judgment of subsequent time scales in time.

[0023] Step S20: At the arrival of each sampling period, determine the first monitoring level corresponding to the first time scale based on the instantaneous current sampling value of each phase winding, determine the second monitoring level corresponding to the second time scale based on the window thermal load intensity value of each phase winding within the preset time window, and determine the third monitoring level corresponding to the third time scale based on the instantaneous current sampling value of each phase winding and the historical heat integral residual value retained from the previous sampling period; wherein, the window thermal load intensity value is the cumulative value of the square of the instantaneous current sampling value over time; In this embodiment, for each phase winding, at the arrival of each sampling cycle, the instantaneous current sampling value of each phase winding is acquired, and the thermal protection level is determined for the instantaneous current sampling values ​​at at least three time scales, thereby obtaining at least the first monitoring level corresponding to the first time scale, the second monitoring level corresponding to the second time scale, and the third monitoring level corresponding to the third time scale; wherein, the first monitoring level is determined based on the instantaneous current sampling value of each phase winding, the second monitoring level is determined based on the window thermal load intensity value of each phase winding within a preset time window, and the third monitoring level is determined based on the instantaneous current sampling value of each phase winding and the historical thermal integral residual value retained from the previous sampling cycle.

[0024] In one implementation, the monitoring level determination logic used for the three time scales is different. Specifically, the monitoring level determination logic for the first time scale may include: determining the first monitoring level corresponding to the first time scale by comparing the instantaneous current sampling value of each phase winding with the preset maximum allowable current value; the monitoring level determination logic for the second time scale may include: determining the second monitoring level corresponding to the second time scale by comparing the window thermal load intensity value within the preset time window with the preset first reference value; the monitoring level determination logic for the third time scale may include: obtaining the cumulative thermal integral value of the current sampling period by recursively updating the instantaneous current sampling value of each phase winding and the historical thermal integral residual value remaining after heat dissipation attenuation in the previous sampling period, and comparing it with the preset second reference value to determine the third monitoring level corresponding to the third time scale.

[0025] In one implementation, the monitoring level judgment logic used at the three time scales can be executed in parallel, making independent judgments without interfering with each other. Each of the judgment logics at the three time scales maintains independent state variables, and the judgment result at any time scale does not affect the judgment process at other scales. This embodiment may also include monitoring level judgment logic at other time scales. For example, a fourth time scale for monitoring specific frequency resonances can be added according to specific application requirements; however, this is not limited here.

[0026] In this embodiment, the A-phase and B-phase windings use the same sampling period to synchronously sample the current. When each sampling period arrives, the current values ​​of the A-phase and B-phase in the current sampling period are collected simultaneously to obtain the instantaneous current sampling values ​​of the A-phase and B-phase in the current sampling period. Then, the monitoring level is judged for the instantaneous current sampling values ​​of the A-phase and B-phase at at least three time scales. At least the monitoring levels of the A-phase and B-phase at the three time scales are obtained, that is, at least the first monitoring level of the A-phase and B-phase at the first time scale, the second monitoring level of the A-phase and B-phase at the second time scale, and the third monitoring level of the A-phase and B-phase at the third time scale are obtained.

[0027] Understandably, since the two-phase windings are physically independent and electrically orthogonal, overheating of either phase poses a risk of winding damage. Therefore, this implementation method separately acquires current sampling values ​​for phase A and phase B and subsequently determines their monitoring levels. Each phase winding independently maintains its own thermal state parameters, without affecting the others.

[0028] This implementation assesses the motor's thermal state from three different time dimensions, with each dimension independently calculating a monitoring level, rather than sharing a single judgment result. The first time scale corresponds to the instantaneous amplitude judgment within a single sampling period, focusing on whether the current exceeds the absolute upper limit of the device's safe operating capacity at the current moment. The second time scale corresponds to a short-term cumulative judgment over a finite number of sampling periods, focusing on the heat generated by the accumulated current over a recent period. The third time scale corresponds to a long-term cumulative judgment since the system began operating, focusing on the remaining value of the heat accumulated by the motor from startup to the current moment after dissipation.

[0029] This implementation method covers multiple fault detections across multiple time scales. Specifically, the first time scale responds to instantaneous device-level faults, the second time scale covers mechanical anomaly faults, and the third time scale covers process accumulation faults. Each of the three scales performs its own function, achieving protection coverage across multiple time scales from microseconds to minutes.

[0030] In one implementation, the maximum permissible current value can be determined based on different device parameters. Specifically, it can be the calibrated maximum rated current obtained from the product manual, the peak withstand current obtained from the motor datasheet, or a safety limit uniformly calibrated during system design; no specific limitation is made here.

[0031] In this embodiment, when determining the second monitoring level corresponding to the second time scale based on the window thermal load intensity values ​​of each phase winding within a preset time window, the second monitoring level is determined by comparing the cumulative value of the square of the instantaneous current sampling value over time within the preset time window with a preset first reference value. The duration of the preset time window can be set according to different fault types. A shorter duration can be used for fast-responding small- and medium-diameter butterfly valves, a medium duration for general industrial butterfly valves, and a longer duration for large-diameter, high-inertia butterfly valves. The calculation of the cumulative value within the time window can be performed in real-time during each sampling cycle or in batches at set intervals; the specific method is not limited here.

[0032] In this embodiment, the preset time window is a time window that extends backward by a fixed time length, with the current sampling period as the end point. This window slides forward with each sampling period, and as the current sampling period is continuously updated, the data within the window is also updated accordingly.

[0033] In one implementation, time window buffers for phases A and B can be pre-maintained, with each buffer storing a sequence of current square values ​​within the most recent preset duration. During each sampling period, the current square value for the current sampling period is written into the buffer, and the oldest value that will be overwritten is subtracted from the accumulated sum to obtain the current window thermal load intensity value. This value is then compared with a preset first reference value, and a second monitoring level is determined based on the comparison result. The preset first reference value can be the product of the square of the winding's rated current and a preset duration. The preset duration (i.e., the duration of the preset time window) can be set according to the valve's response characteristics, for example, 200 ms.

[0034] In this embodiment, when determining the third monitoring level corresponding to the third time scale based on the instantaneous current sampling values ​​of each phase winding and the historical heat integral residual value retained from the previous sampling period, the cumulative heat integral value of the current sampling period can be obtained by recursively updating the instantaneous current sampling value of the current sampling period and the historical heat integral residual value retained after heat dissipation attenuation from the previous sampling period, thereby determining the third monitoring level corresponding to the third time scale. The historical heat integral residual value retained after heat dissipation attenuation from the previous sampling period is obtained by multiplying the cumulative heat integral value of the previous sampling period by a heat dissipation attenuation coefficient. This attenuation coefficient reflects the proportion of heat lost by the winding due to heat dissipation to the environment within the time interval between two adjacent sampling periods, and its specific form can vary depending on the selection of the thermal model. The cumulative heat integral value is a comprehensive indicator characterizing the thermal state of the winding at the third time scale, and can include historical information on the winding heat since the system was powered on, reflecting the equivalent thermal load of the winding at the current moment.

[0035] In one implementation, the cumulative heat integral variables of phases A and B can be pre-maintained. In each sampling period, the cumulative heat integral value of the previous sampling period is multiplied by a heat dissipation attenuation coefficient, and then added to the product of the squared current value and the sampling period to obtain the cumulative heat integral value of the current sampling period. The heat dissipation attenuation coefficient is determined by the sampling period and the winding thermal time constant. The cumulative heat integral value is then compared with a preset second reference value, and a third monitoring level is determined based on the comparison result.

[0036] Step S30: Execute the target thermal protection action according to the first monitoring level, second monitoring level and third monitoring level of each phase winding to provide thermal protection for the stepper motor.

[0037] This implementation determines the target thermal protection action based on all monitoring levels corresponding to all time scales of the two-phase windings, thereby avoiding the risk of winding damage caused by abnormal thermal state of any phase. When determining the target thermal protection action, a target protection level can be determined from the monitoring levels corresponding to each time scale according to preset rules, and then the target thermal protection action can be determined based on the target protection level. Alternatively, a target thermal protection action can be selected / generated from multiple candidate protection actions according to preset rules. The target thermal protection action may include maintaining the status quo, that is, taking no action; the specifics are not limited here.

[0038] When determining the target thermal protection action, different weights or priorities can be assigned to the monitoring levels at different time scales based on the thermal damage mechanisms corresponding to each time scale, and the target thermal protection action can be determined according to the weights or priorities. For example, the priority of instantaneous overcurrent can be higher than that of cumulative overheating, or the same protection action as instantaneous overcurrent can be triggered after cumulative overheating reaches a certain threshold. In another feasible implementation, the thermal state of both phase windings can also be considered for judgment. For example, the protection action level triggered when both phases are in a high thermal state is higher than the protection action level triggered when only one phase is in a high thermal state. The specific determination method can be flexibly set according to factors such as motor type, application scenario, and safety requirements.

[0039] The target thermal protection action can be selected from a set of preset tiered response actions. These preset tiered response actions can include multiple levels of actions arranged from low to high. For example, actions corresponding to the basic protection level may include logging and reporting warning information to the host computer; actions corresponding to the medium protection level may include derating and limiting the current amplitude of the PWM drive signal; actions corresponding to the high protection level may include pausing the motor's motion command or forcibly limiting the current; and the highest level action may include triggering a hardware interlock signal to drive the valve to the closed position, and cutting off the motor's drive enable after confirming that the valve has responded to the closed position. Actions corresponding to different protection levels can be executed individually or in combination. The correspondence between the various levels of actions can be flexibly configured according to the motor's safety requirements.

[0040] After the target thermal protection action is executed, a recovery action can be performed as needed to deactivate the thermal protection. When performing a recovery action as needed, it can be automatic, such as automatically deactivating the protection action when the thermal condition drops below a safe threshold; it can be manual, requiring operator confirmation before resuming normal operation; or it can be semi-automatic, such as issuing a prompt after detecting a safe thermal condition, requiring operator confirmation for recovery.

[0041] In one implementation, this step includes: when the first monitoring level corresponding to any phase winding is the highest protection level, the generation of the drive signal can be stopped, such as blocking PWM; when no winding corresponds to the first monitoring level being the highest protection level, the levels of the second and third monitoring levels are compared, and the monitoring level with the highest level is determined as the target protection level for the current sampling period; based on the target protection level, the target thermal protection action corresponding to the target protection level is determined from a plurality of preset graded response actions, and the target thermal protection action is executed.

[0042] The stepper motor thermal protection method for vacuum valves provided in the above embodiments constructs a multi-timescale parallel judgment architecture, determines the target thermal protection action based on the monitoring level corresponding to each timescale, and enables the protection method to have quantitative traceability, a protection mechanism that can balance instantaneous thermal damage and time-accumulated thermal damage, an inherent memory of the thermal history of the windings, and the ability to form a hardware interlocking closed loop. As a result, the thermal protection is transformed from a single rigid over-limit judgment to a multi-dimensional, memoryable, and quantifiable refined protection, which significantly improves the flexibility and controllability of motor thermal protection.

[0043] Next, we will explain the specific thermal protection method of the stepper motor in the vacuum valve.

[0044] In one embodiment, determining the first monitoring level corresponding to the first time scale based on the instantaneous current sampling value of each phase winding includes: comparing the instantaneous current sampling value of each phase winding with a preset maximum allowable current value; wherein the preset maximum allowable current value is the smaller of the absolute maximum current of the stepper motor's drive power device and the instantaneous withstand current of the corresponding winding; if the instantaneous current sampling value is greater than the preset maximum allowable current value, then the highest protection level is determined as the first monitoring level of the corresponding winding in the first time scale; if the instantaneous current sampling value is less than or equal to the preset maximum allowable current value, then the basic protection level is determined as the first monitoring level of the corresponding winding in the first time scale.

[0045] In this embodiment, the preset maximum allowable current value is taken as the smaller of the absolute maximum current of the motor's drive power device and the instantaneous withstand current of the corresponding winding. The absolute maximum current of the drive power device can be the maximum allowable on-state current specified by the power switching device (such as a MOSFET or IGBT) in the drive circuit, which can be obtained from the device's datasheet. This parameter is determined by the physical structure, chip area, and heat dissipation capability of the power device; exceeding this value may cause immediate device damage or a drastically shortened lifespan.

[0046] In this embodiment, the instantaneous withstand current of the corresponding winding is the maximum current value that the motor winding can withstand in a short period of time. It is determined by the cross-sectional area, material, and insulation class of the winding conductor and can be obtained from the product manual. It reflects the physical limit of the winding under instantaneous overcurrent conditions. Since the power devices and windings in the drive circuit are connected in series, overcurrent of any device (power device or winding) may lead to overall failure. Therefore, the protection threshold is taken as the weaker link between the two as a benchmark, which can ensure that no device in the drive circuit exceeds its physical safety limit, thus ensuring higher safety.

[0047] In this embodiment, when the instantaneous current sampling value is greater than the preset maximum allowable current value, the highest protection level is determined as the first monitoring level of the corresponding winding in the first time scale, and the target thermal protection action corresponding to the highest protection level can be triggered immediately; when the instantaneous current sampling value is less than or equal to the preset maximum allowable current value, the basic protection level is determined as the first monitoring level of the corresponding winding in the first time scale, and the specific details are not limited here.

[0048] In one implementation, when the first monitoring level corresponding to any phase winding is the highest protection level, the generation of the drive signal can be stopped, such as blocking PWM; only when no winding has a first monitoring level corresponding to the highest protection level will the subsequent steps of determining the second and third monitoring levels continue to be executed.

[0049] In one embodiment, determining the second monitoring level corresponding to the second time scale based on the window thermal load intensity value of each phase winding within a preset time window includes: for each phase winding, within the current sampling period and a preset time window of a preset duration, accumulating the product of the square of the instantaneous current sampling value of each sampling period and the sampling period to obtain the window thermal load intensity value corresponding to each phase winding; wherein, the preset duration is less than the winding thermal time constant of the stepper motor; comparing the window thermal load intensity value corresponding to each phase winding with a preset first reference value, and determining the second monitoring level corresponding to each phase winding at the second time scale based on the comparison result; wherein, the preset first reference value is the product of the square of the winding rated current of the motor and the preset duration.

[0050] In this embodiment, the window thermal load intensity value within the preset time window The calculation formula is as follows:

[0051] Where N is the number of current sampling samples (i.e., the number of sampling points) within the preset time window. Where W is the current sampling period, W is the duration of the preset time window (i.e., the preset duration mentioned above), k represents the discrete sampling time, and I represents the instantaneous current value. .

[0052] It is understandable that the physical meaning of the square of the current is that the Joule heat power in the winding is proportional to the square of the current. Therefore, the square of the current directly reflects the instantaneous heating intensity at that moment. Multiplying this value by the sampling period yields the relative heat generated within that sampling interval; summing the relative heat from all sampling intervals gives the total relative heat load (i.e., the window heat load intensity value) for the entire window period.

[0053] It's important to note that the window thermal load intensity value does not include a heat dissipation attenuation term; that is, older data within the window will not be forgotten or decayed over time. This design choice is based on the fact that the goal of the second time scale is to capture the instantaneous thermal shock caused by short-term mechanical anomalies (such as jamming or stalling). In these millisecond-level short-term fault scenarios, the heat dissipation effect to the environment is negligible; introducing heat dissipation attenuation would actually reduce the sensitivity of the protection and may lead to missed protection. Therefore, the calculation of the window thermal load intensity value only involves accumulation, without attenuation.

[0054] In this embodiment, the winding thermal time constant The thermal time constant is a physical parameter characterizing the thermal inertia of a motor winding. Physically, it represents the time required for the winding temperature to rise to 63.2% of its final stable temperature rise under step heating conditions, typically ranging from tens to hundreds of seconds. The thermal time constant reflects the rate at which the winding heats up or cools down—the smaller the time constant, the faster the winding temperature responds to changes in current; the larger the time constant, the slower the winding temperature responds to changes in current.

[0055] In this embodiment, the preset duration is shorter than the thermal time constant of the motor windings, ensuring that the time range covered by the second time scale is smaller than the time scale of the motor's thermal response. This means that within the preset window duration, the winding temperature hardly has time to undergo a significant global change. Therefore, the window thermal load intensity value can be considered an effective measure of instantaneous thermal shock, rather than a measure of global temperature rise. The specific value of the preset duration can be configured according to the valve's response characteristics and fault type. For example, a shorter window duration (e.g., 50ms) can be used for small- to medium-diameter butterfly valves with faster response, while a longer window duration (e.g., 500ms) can be used for larger-diameter, larger-inertia butterfly valves, but both must maintain the constraint of being less than the thermal time constant of the windings.

[0056] In this embodiment, a first reference value is preset. The rated current of the motor windings The product of the square of the product and the preset duration W is expressed as follows:

[0057] Using a preset first benchmark value as a comparison scale, the deviation of the actual window thermal load intensity value from the rated operating condition can be determined. When the motor runs continuously at the rated current, the winding temperature rise is within the normal range allowed by the design. At this time, the corresponding window thermal load intensity value constitutes the upper limit reference of the normal operating condition. When the actual window thermal load intensity value exceeds this benchmark value, it indicates that the current level has exceeded the rated operating condition, and corresponding protection actions can be triggered according to the degree of exceedance. Since the preset first benchmark value is directly related to the preset duration, the benchmark value changes proportionally with the change of window length, thereby ensuring the consistency of the judgment standard of the second monitoring level under different window length configurations.

[0058] In one implementation, when comparing the window thermal load intensity value with a preset first reference value and determining the second monitoring level of each phase winding at the second time scale based on the comparison result, the second monitoring level can be determined according to the ratio of the window thermal load intensity value to the preset first reference value. For example, when the ratio is low, it is determined to be the basic level L1; when the ratio reaches a certain value, it is determined to be the intermediate level L2; and when the ratio is high, it is determined to be the high level L3. The specific threshold division can be flexibly set according to the motor's overload capacity and the safety requirements of the application scenario.

[0059] Table 1 shows an example of the correspondence between the second monitoring level, the level threshold, and the protective action.

[0060] Table 1 According to Table 1: When 0.8 × 1.0 × At this time, the second monitoring level is the basic protection level L1, and the corresponding protection actions may include: logging and reporting early warning information to the host computer; When 1.0 × 1.4 × At this time, the second monitoring level is the intermediate protection level L2, and the corresponding protection actions may include: derating and limiting the current amplitude of the pulse width modulation drive signal to... ; When 1.4 × 2.0 × At this time, the second monitoring level is the advanced protection level L3, and the corresponding protection action may include: suspending the motor's movement command; when 2.0 × At this time, the second monitoring level is the highest protection level L4, and the corresponding protection action may include: triggering a hardware interlock signal to drive the valve to the closed position, and cutting off the motor drive enable after confirming that the valve has responded to the closed position.

[0061] Based on the above correspondence, the protection action corresponding to the second time scale can also be determined. This protection action can be used as the basis for determining the target protection action, or it can be used as the specific action to be performed when the monitoring level corresponding to the time scale indicates that the protection action needs to be performed immediately. The specifics are not limited here.

[0062] In one implementation, determining the third monitoring level corresponding to the third time scale based on the instantaneous current sampling value of each phase winding and the historical heat integral residual value retained from the previous sampling period includes: calculating the historical heat integral residual value retained by each phase winding after heat dissipation attenuation in the previous sampling period based on the cumulative heat integral value of each phase winding in the previous sampling period, the ratio of the preset sampling period to the winding thermal time constant of the stepper motor; multiplying the square of the instantaneous current sampling value of each phase winding in the current sampling period by the preset sampling period as the new heat value of each phase winding in the current sampling period; adding the historical heat integral residual value of each phase winding to the corresponding new heat value to obtain the cumulative heat integral value of each phase winding in the current sampling period; comparing the cumulative heat integral value of each phase winding in the current sampling period with a preset second reference value, and determining the third monitoring level corresponding to each phase winding in the third time scale based on the comparison result; wherein, the preset second reference value is the product of the square of the rated winding current of the motor and the winding thermal time constant.

[0063] In this embodiment, the cumulative heat integral value of the previous sampling period is the cumulative heat integral value calculated in the (k-1)th sampling period. This value contains all thermal history information since the system was powered on (or since the last thermal reset), updated recursively to the previous sampling period. In this embodiment, the ratio of the preset sampling period to the motor winding thermal time constant is... This ratio reflects the relative strength of the heat dissipation effect relative to the winding's thermal response speed within a single sampling period. This ratio is typically much smaller than 1, for example, 100μs / 100s = Specific details are not specified here.

[0064] The residual historical heat integral value after heat dissipation decay from the previous sampling period represents the proportion of accumulated heat from the previous sampling period that remains after one sampling period due to heat dissipation to the environment. It can be calculated by multiplying the accumulated heat integral value from the previous sampling period by the heat dissipation decay coefficient, expressed as:

[0065] In this embodiment, The winding thermal time constant, For the current sampling period, the newly added heat value in the current sampling period is This represents the newly generated heat load within the current sampling period, which is the incremental portion relative to the heat retained in the previous sampling period. The cumulative heat load value for the current sampling period is obtained by adding the historical residual heat load after heat dissipation to the newly generated heat load value.

[0066] In this embodiment, The winding thermal time constant, Let k be the current sampling period, and k represent the discrete sampling time. The cumulative heat integral value is calculated in the (k-1)th sampling period, where I represents the instantaneous current value. The preset second reference value is the product of the square of the rated current of the motor winding and the thermal time constant of the winding, i.e.

[0067] This indicates that when the motor operates at its rated current During continuous operation, the steady-state cumulative heat integral value is .

[0068] In one implementation, a second reference value is preset. Based on the stepper motor operating at rated current under the maximum permissible ambient temperature. The condition under which the winding temperature reaches the upper limit of the insulation class when energized and reaching steady state is pre-defined. Specifically, the maximum permissible ambient temperature (e.g., 40°C or 50°C) and insulation class (e.g., 155°C for Class F or 180°C for Class H) can be obtained from the motor specifications. At this maximum ambient temperature, if the motor operates at rated current for an extended period, the winding will eventually reach a stable maximum temperature, which should be exactly equal to the upper limit of the insulation class. The steady-state cumulative heat value under this condition is... .

[0069] Since the preset second reference value is calibrated based on the maximum permissible ambient temperature, in actual use, as long as the cumulative heat integral value does not exceed this reference value, the winding temperature will not exceed the upper limit of the insulation class, regardless of whether the current ambient temperature reaches the maximum permissible value. When the actual ambient temperature is lower than the maximum permissible value, the winding temperature is already below the upper limit of the insulation class before the cumulative heat integral value reaches the reference value, so the protection will trigger earlier, which is in line with the safety design direction. This calibration method enables the entire protection system to correctly determine the thermal state of the winding without configuring additional temperature sensors, achieving temperature immunity to the environment and the initial temperature of the winding.

[0070] In this embodiment, the cumulative heat integral value calculated in the current sampling period is used. Compared with the preset second reference value Numerical comparisons are performed, and the third monitoring level is determined based on the comparison results. Specifically... The third monitoring level can be determined based on the ratio of the cumulative heat integral value to a preset second benchmark value. The specific settings of each threshold can be flexibly configured according to insulation class requirements and safety margins.

[0071] Table 2 shows an example of the correspondence between the third monitoring level, the level threshold, the thermal state, and the protective action.

[0072] Table 2 According to Table 2: When 0.60 × <0.80 × At that time, the third monitoring level is the basic protection level L1, which corresponds to the thermal state when the temperature rise reaches the upper limit of 60%. The corresponding protection actions may include: recording the log and reporting the warning information to the host computer. When 0.80 × <0.95 × At this time, the third monitoring level is the intermediate protection level L2, corresponding to a thermal state where the temperature rise reaches 80% of the upper limit. The corresponding protection actions may include: reducing the current amplitude of the pulse width modulation drive signal to 0.85. ; When 0.95 × <1.00 × At this time, the third monitoring level is the advanced protection level L3, corresponding to a thermal state where the temperature rise reaches 95% of the upper limit. The corresponding protection actions may include: forced current limiting to 0.70. ; when ≥1.00 × At this time, the third monitoring level is the highest protection level L4, which corresponds to the thermal state reaching the rated upper limit. The corresponding protection action may include: triggering a hardware interlock signal to drive the valve to the closed position, and cutting off the motor drive enable after confirming that the valve has responded to the closed position.

[0073] Based on the above correspondence, the thermal state and protection action corresponding to the third time scale can also be determined. This protection action can be used as the basis for determining the target protection action, or as the specific action to be performed when the protection level indication corresponding to the time scale requires immediate execution of the protection action. The specifics are not limited here.

[0074] In one embodiment, a target thermal protection action is executed based on the first monitoring level, the second monitoring level, and the third monitoring level of each phase winding, including: comparing the levels of the first monitoring level, the second monitoring level, and the third monitoring level of each phase winding, determining the monitoring level with the highest level as the target protection level for the current sampling period; and determining the target thermal protection action corresponding to the target protection level from a plurality of preset graded response actions based on the target protection level, and executing the target thermal protection action.

[0075] This implementation method compares the monitoring levels obtained by phase A and phase B windings at the first, second, and third time scales, which constitute a set of six monitoring levels in total. The highest level is taken as the target protection level for the current sampling period, and the target thermal protection action is determined by the target protection level.

[0076] The system includes multiple preset tiered response actions, including a pre-configured set of protection actions arranged from low to high response intensity, each corresponding to a different target protection level. The differences between each level of action configuration lie in the degree of intervention in the motor's operating status. For example, low-level actions only include recording and notification, intermediate-level actions include adjusting operating parameters, high-level actions include stopping the motor, and the highest-level actions include cutting off the motor drive enable and triggering hardware interlocks; specific details are not limited here.

[0077] In one embodiment, the preset plurality of graded response actions include response actions corresponding to at least three protection levels from low to high. Based on the target protection level, a target thermal protection action corresponding to the target protection level is determined from the preset plurality of graded response actions, and the target thermal protection action is executed. This includes: when the target protection level is a basic protection level, obtaining the response action corresponding to the basic protection level from the preset plurality of graded response actions, using it as the target thermal protection action, and executing it. The response action corresponding to the basic protection level includes: recording a log and reporting a warning message to the host computer. When the target protection level is an intermediate protection level, obtaining the response action corresponding to the intermediate protection level from the preset plurality of graded response actions, using it as the target thermal protection action, and executing it. The response action corresponding to the intermediate protection level includes: derating and limiting the current amplitude of the pulse width modulation drive signal. When the target protection level is a high protection level, obtaining the response action corresponding to the high protection level from the preset plurality of graded response actions, using it as the target thermal protection action, and executing it. The response action corresponding to the high protection level includes: pausing the motor's motion command or forcibly limiting the current.

[0078] Basic protection level L1 is the lowest level among multiple preset graded response actions, corresponding to a thermal state that requires attention but has not yet reached the critical state requiring intervention. This level is typically triggered when thermal state parameters reach a low threshold, such as a window thermal load intensity value reaching 0.8 times the rated reference value, or a cumulative thermal integral value reaching 0.6 times the rated reference value. At this level, the motor does not face immediate risk, but the thermal state has deviated from the normal range and requires attention.

[0079] In this embodiment, the protection actions corresponding to the basic protection level include: recording logs and reporting early warning information to the host computer. When recording logs, the trigger timestamp, trigger reason (which may be the corresponding time scale source), thermal state parameter values ​​at the time of triggering (such as window thermal load intensity value, cumulative heat integral value), target protection level, etc. can be written into the system's log storage area. This can provide a data foundation for subsequent fault analysis and predictive maintenance, enabling maintenance personnel to trace the occurrence process and evolution pattern of thermal state anomalies.

[0080] When reporting early warning information to the host computer, the information can be sent to an external monitoring terminal via a communication interface. Communication can be achieved through data frame transmission via a communication bus, signal output via digital output terminals, or a combination of both. Early warning information allows maintenance personnel or the upper-level control system to promptly understand the changing trends in the motor's thermal state, enabling preventative measures to be taken before problems escalate, such as adjusting process parameters or scheduling maintenance.

[0081] Intermediate protection level L2 is an intermediate protection level, higher than level one but lower than level three. This level typically triggers when the thermal condition has significantly deviated from the normal range but has not yet reached an emergency level. For example, the window thermal load intensity value reaches 1.0 times but not more than 1.4 times the rated reference value, or the cumulative heat integral value reaches 0.8 times but not more than 0.95 times the rated reference value. At this level, the motor already faces a certain thermal risk and needs to reduce output power to mitigate temperature rise, but it has not yet reached a point where immediate shutdown is necessary.

[0082] In this embodiment, the protection action corresponding to the intermediate protection level includes: derating and limiting the current amplitude of the pulse width modulation drive signal, that is, reducing the current command value or duty cycle of the PWM drive signal, thereby reducing the output current amplitude of the motor (i.e., reducing the target current amplitude through current loop control, which is a command-level action mode, the current sine waveform is complete, proportionally reduced, and can minimize step loss). Specifically, the target current value can be reduced from the current value to a preset derating value, where the derating value can be a fixed value, such as limiting it to a certain percentage of the rated current (e.g., 85%); or it can be a dynamic value, reducing the current command value proportionally according to the degree of overheating (the more severe the overheating, the greater the derating). The purpose of derating and limiting is to reduce the heat generation power of the winding. Since the heat generation power is proportional to the square of the current, even a small derating can produce a significant heat reduction effect (e.g., when derating to 85%, the heat generation power drops to 72.25% of the original), thereby slowing down the rate of temperature rise and providing the winding with time for heat dissipation and recovery.

[0083] In one implementation, the duration and release condition of the derating limit can be configured such that when the thermal condition drops below a safe threshold, the current command value is gradually restored. The restoration process can be gradual (gradually increasing the current command value) or one-time (direct restoration), which can be set according to application requirements.

[0084] Advanced protection level L3 is a higher protection level than L2 but lower than L4. This level is typically triggered when the thermal condition is close to a dangerous boundary, such as when the window thermal load intensity reaches 1.4 times but not more than 2.0 times the rated reference value, or when the cumulative heat integral value reaches 0.95 times but not more than 1.0 times the rated reference value. At this level, the motor faces an imminent thermal risk and needs to immediately stop generating new heat, but the level has not yet reached the point where a complete power-off is necessary.

[0085] In this embodiment, the protection actions corresponding to the advanced protection level include: suspending the motor's motion commands or forcibly limiting current. Suspending the motor's motion commands means stopping the transmission of new motion control commands to the drive module, preventing the motor from performing new position or speed adjustments, and keeping the current valve plate position unchanged. The purpose of suspending the motion commands is to immediately stop the motor from generating new Joule heat, thereby preventing the winding temperature from continuing to rise. Suspension does not mean the motor is completely de-energized—the motor remains enabled but no longer receives new motion commands.

[0086] Forced current limiting refers to imposing a hard upper limit on the current command value of the PWM drive signal, ensuring that the motor winding current does not exceed this upper limit under any operating condition. This prevents further deterioration of heat accumulation without completely stopping the motor (i.e., chopping the current loop output by setting a current threshold in hardware; this is a hardware-level operation, and the current sine waveform may be clipped, allowing for loss of synchronization to protect the windings). Specifically, forced current limiting can be achieved by limiting the maximum duty cycle of the PWM drive signal. For example, the PWM duty cycle can reach 100% during normal operation; forced current limiting clamps the upper limit of the duty cycle to a preset value (e.g., 70%). Since the motor current is approximately proportional to the PWM duty cycle, the duty cycle clamping directly limits the current amplitude. This method is simple to implement, responds quickly, and takes effect within each PWM cycle.

[0087] In one implementation, the duration of the pause and the resumption conditions can be configured such that the execution of the motion command is automatically resumed when the thermal state drops below a safety threshold; or it can be configured such that the motion only resumes after the host computer sends a resumption command.

[0088] The highest protection level, L4, corresponds to a thermal condition that has reached or exceeded safety boundaries. For example, the window thermal load intensity exceeds 2.0 times the rated reference value, or the cumulative heat integral value exceeds 1.0 times the rated reference value. At this level, the motor faces the risk of irreversible thermal damage and requires the strongest protective measures.

[0089] In one implementation, when the target protection level is the highest protection level, the target thermal protection action corresponding to the target protection level is determined from a plurality of preset graded response actions according to the target protection level, and the target thermal protection action is executed. The implementation also includes: triggering a hardware interlock signal to drive the valve to the closed position, and cutting off the motor drive enable after confirming that the valve has responded to the closed position.

[0090] In this embodiment, the protection action corresponding to the highest protection level includes: triggering a hardware interlock signal to drive the valve to the closed position, and cutting off the motor drive enable after confirming that the valve has responded to the closed position. Triggering the hardware interlock signal to drive the valve to the closed position is achieved by sending an interlock signal through a hardware output interface (such as a relay or optocoupler). This signal is connected to the interlock input terminal of the valve controller, triggering the valve to perform a safe closing action. The difference between hardware interlock signals and software instructions is that the interlock signal is transmitted directly through the hardware circuit, without going through the encapsulation and decapsulation of the communication protocol stack, resulting in a faster response and independent operation even if the communication link is abnormal. The purpose of driving the valve to the closed position is to place the vacuum valve in the safest state, preventing safety accidents caused by motor malfunction or subsequent pressure abnormalities.

[0091] After confirming that the valve has responded to the closed position, the motor drive enable is cut off. That is, after triggering the hardware interlock signal, the system waits and confirms that the valve has actually responded and reached the closed position before cutting off the motor drive enable. Confirmation of the valve's closed position can be achieved by reading the confirmation status signal from the valve controller's digital output, which takes effect when the valve reaches the closed position. This implementation ensures the integrity of the safety closed loop, preventing the motor enable from being cut off if the valve fails to actually close due to mechanical or controller malfunction.

[0092] In this embodiment, cutting off the motor's drive enable can be achieved through hardware or software methods to prevent the power devices from conducting, thus preventing the motor from generating any torque. After the enable is cut off, the motor is in a free-stop or unpowered state and no longer generates Joule heat.

[0093] In one embodiment, the step of triggering a hardware interlock signal to drive the valve to the closed position, and then cutting off the motor drive enable after confirming that the valve has responded to the closed position, includes: outputting a hardware interlock signal via a relay or optocoupler; wherein the hardware interlock signal is connected to the interlock input terminal of the valve controller to control the motor to drive the valve to the closed position; reading the confirmation status signal of the digital output terminal of the valve controller to confirm that the valve has actually responded to the closed position; cutting off the motor drive enable after confirming that the valve has responded to the closed position; recording the trigger timestamp of the target thermal protection action, and reporting the trigger timestamp and fault information to the host computer.

[0094] This implementation transmits the interlock signal to external devices via a hardware output interface. The interlock signal output can be implemented using devices such as relays or optocouplers. The valve controller is equipped with an interlock input interface for receiving external signals. When the interlock input is activated, the valve controller immediately executes a preset safety action, including driving the valve plate to the closed position. The interlock signal is a trigger source, not a direct driving force; the actual driving action is completed by the internal logic and power circuitry of the valve controller.

[0095] In this embodiment, the feedback signal sent by the valve controller is read through the digital input interface. That is, after the valve controller detects that the valve plate has reached the closed position, it will output an acknowledgment status signal through its digital output terminal to provide feedback on the execution result to the external system and confirm whether the valve has actually responded to the closed position. For example, a high level of the acknowledgment status signal indicates that the position has been reached, and a low level indicates that the position has not been reached; the specific details are not limited here.

[0096] After confirming that the valve has responded to the closed position, the motor drive enable is cut off, meaning the motor is in a free-stop or unpowered state, no longer generating Joule heat. If the valve fails to respond to the closed position, any of the following measures can be taken: wait for a confirmation signal for a preset timeout period; after the timeout period, record the valve response anomaly and still cut off the enable to prevent the motor from continuing to overheat; while cutting off the enable, attempt to drive the valve to close again through another channel; or report the valve response anomaly to the host computer through the alarm channel.

[0097] In one embodiment, the method further includes: when a power failure signal is detected, writing the accumulated thermal integral value of the current sampling period as a thermal integral residual value into a non-volatile memory; when a power-on signal is detected, reading the thermal integral residual value from the non-volatile memory as the initial value of the historical thermal integral residual value retained after heat dissipation attenuation in the previous sampling period when the recursive update is performed for the first time after power-on.

[0098] This implementation saves the current accumulated heat integral value when the system is powered off, and restores this value as the recursive initial value when the system is powered on again. This allows the system to correctly identify the residual heat of the windings when the engine is warm, avoiding operation according to the cold engine parameters when the windings are still in a high temperature state, and eliminating the risk of secondary thermal damage caused by the loss of thermal history.

[0099] Figure 2 The diagram shows the coverage of each of the three time scales provided in this embodiment and the corresponding distribution of decisive failure scenarios. Figure 2 As shown, the first time scale corresponds to the instantaneous current amplitude judgment in a single sampling period, with a time coverage range in the microsecond range. It mainly covers device-level instantaneous fault scenarios such as short circuits / line faults (e.g., winding short circuits, power device shoot-through, etc.) and current spikes caused by incorrect drive parameters. The response at this scale is implemented by a hardware analog comparator, without relying on software execution, and the response time is in the sub-microsecond range, making it the fastest responding layer in the three-layer protection architecture.

[0100] Figure 2 In this model, the second time scale corresponds to the cumulative current square within a time window, with a time coverage range of milliseconds (typically 50ms to 500ms). It mainly covers mechanical anomaly fault scenarios such as valve plate mechanical jamming, high-frequency reciprocating oscillations caused by unstable pressure control, and accelerated overload of large-diameter valve plates. The thermal load intensity value of this scale does not include a heat dissipation attenuation term and accumulates continuously within the window duration. After the window slides, the old data is forgotten, making it suitable for capturing short-term thermal shock events.

[0101] Figure 2In this context, the third time scale corresponds to the recursive cumulative judgment including heat dissipation decay, with a time coverage range from seconds to minutes (determined by the winding thermal time constant, typically tens to hundreds of seconds). It mainly covers cumulative overheating scenarios that cannot be identified by instantaneous and window criteria alone, such as long-term high-frequency process scheduling, trending current rise due to gradual deterioration of mechanical friction, and hot-start of the engine after power failure. The cumulative heat integral value at this scale contains all thermal history information since the system was powered on (after exponential decay) and has long-term memory capability.

[0102] The three timescales are interconnected and non-overlapping, each covering a decisive fault scenario that cannot be replaced by other timescales. The first timescale covers device-level instantaneous faults, the second timescale covers short-term mechanical anomalies, and the third timescale covers long-term process-accumulated faults. The three timescales work together to achieve thermal protection coverage from microseconds to minutes.

[0103] For the corresponding method embodiments described above, see [link to relevant documentation]. Figure 3 The diagram shows a stepper motor thermal protection device for a vacuum valve. The device includes: a sampling module 32, used to synchronously sample the instantaneous current values ​​of two-phase windings of the stepper motor at a preset sampling period; a monitoring module 34, used to determine, at the end of each sampling period, a first monitoring level corresponding to a first time scale based on the instantaneous current sampling values ​​of each phase winding, a second monitoring level corresponding to a second time scale based on the window thermal load intensity values ​​of each phase winding within a preset time window, and a third monitoring level corresponding to a third time scale based on the instantaneous current sampling values ​​of each phase winding and the historical thermal integral residual value retained from the previous sampling period; wherein the window thermal load intensity value is the cumulative value of the square of the instantaneous current sampling value over time; and a thermal protection module 36, used to execute a target thermal protection action to thermally protect the stepper motor based on the first, second, and third monitoring levels of each phase winding.

[0104] The aforementioned stepper motor thermal protection device for vacuum valves constructs a multi-timescale parallel judgment architecture, determines the target thermal protection action based on the quantified protection level of each timescale, and enables the protection method to have quantifiable traceability, a protection mechanism that can balance instantaneous thermal damage and time-accumulated thermal damage, an inherent memory of the winding thermal history, and the ability to form a hardware interlocking closed loop. As a result, the thermal protection is transformed from a single, rigid over-limit judgment to a multi-dimensional, memoryable, and quantifiable refined protection, significantly improving the flexibility and controllability of motor thermal protection.

[0105] Optionally, the monitoring module 34 is further configured to: compare the instantaneous current sampling value of each phase winding with the preset maximum allowable current value; wherein the preset maximum allowable current value is the smaller of the absolute maximum current of the stepper motor's drive power device and the instantaneous withstand current of the corresponding winding; if the instantaneous current sampling value is greater than the preset maximum allowable current value, then the highest protection level is determined as the first monitoring level of the corresponding winding in the first time scale; if the instantaneous current sampling value is less than or equal to the preset maximum allowable current value, then the basic protection level is determined as the first monitoring level of the corresponding winding in the first time scale.

[0106] Optionally, the monitoring module 34 is further configured to: for each phase winding, within a preset time window of the current sampling period and the preset duration, accumulate the product of the square of the instantaneous current sampling value of each sampling period and the sampling period to obtain the window thermal load intensity value corresponding to each phase winding; wherein, the preset duration is less than the winding thermal time constant of the stepper motor; compare the window thermal load intensity value corresponding to each phase winding with a preset first reference value, and determine the second monitoring level corresponding to each phase winding on the second time scale based on the comparison result; wherein, the preset first reference value is the product of the square of the winding rated current of the motor and the preset duration.

[0107] Optionally, the monitoring module 34 is further configured to: calculate the historical heat integral residual value of each phase winding after heat dissipation attenuation in the previous sampling period based on the cumulative heat integral value of each phase winding in the previous sampling period, the ratio of the preset sampling period to the winding thermal time constant of the stepper motor; multiply the square of the instantaneous current sampling value of each phase winding in the current sampling period by the preset sampling period as the new heat value of each phase winding in the current sampling period; add the historical heat integral residual value of each phase winding to the corresponding new heat value to obtain the cumulative heat integral value of each phase winding in the current sampling period; compare the cumulative heat integral value of each phase winding in the current sampling period with the preset second reference value, and determine the third monitoring level corresponding to each phase winding in the third time scale based on the comparison result; wherein, the preset second reference value is the product of the square of the winding rated current of the motor and the winding thermal time constant.

[0108] Optionally, the thermal protection module 36 includes: a comparison unit, used to compare the levels of the first monitoring level, the second monitoring level, and the third monitoring level of each phase winding, and determine the monitoring level with the highest level as the target protection level for the current sampling period; and a determination unit, used to determine the target thermal protection action corresponding to the target protection level from a plurality of preset graded response actions based on the target protection level, and execute the target thermal protection action.

[0109] Optionally, the preset multiple graded response actions include at least three response actions corresponding to at least three protection levels from low to high; the determining unit is further configured to: when the target protection level is the basic protection level, obtain the response action corresponding to the basic protection level from the preset multiple graded response actions, and execute it as the target thermal protection action, wherein the response action corresponding to the basic protection level includes: recording a log and reporting a warning message to the host computer; when the target protection level is the intermediate protection level, obtain the response action corresponding to the intermediate protection level from the preset multiple graded response actions, and execute it as the target thermal protection action, wherein the response action corresponding to the intermediate protection level includes: derating and limiting the current amplitude of the pulse width modulation drive signal; when the target protection level is the high protection level, obtain the response action corresponding to the high protection level from the preset multiple graded response actions, and execute it as the target thermal protection action, wherein the response action corresponding to the high protection level includes: pausing the motor's motion command or forcibly limiting the current.

[0110] Optionally, when the target protection level is the highest protection level, the above-mentioned determining unit further includes: a closing subunit, used to trigger a hardware interlock signal to drive the valve to the closed position, and after confirming that the valve has responded to the closed position, to cut off the drive enable of the motor.

[0111] Optionally, the aforementioned shut-off subunit is also used to: output a hardware interlock signal via a relay or optocoupler; wherein the hardware interlock signal is connected to the interlock input terminal of the valve controller to control the motor to drive the valve to the closed position; read the confirmation status signal of the digital output terminal of the valve controller to confirm that the valve has actually responded to the closed position; after confirming that the valve has responded to the closed position, cut off the drive enable of the motor; record the trigger timestamp of the target thermal protection action, and report the trigger timestamp and fault information to the host computer.

[0112] This embodiment also provides a stepper motor, including a processor and a memory. The memory stores machine-executable instructions that can be executed by the processor. The processor executes the machine-executable instructions to implement the above-mentioned stepper motor thermal protection method for vacuum valve.

[0113] See Figure 4 As shown, the stepper motor includes a processor 100 and a memory 101. The memory 101 stores machine-executable instructions that can be executed by the processor 100. The processor 100 executes the machine-executable instructions to implement the stepper motor thermal protection method for the vacuum valve described above.

[0114] Furthermore, Figure 4 The stepper motor shown also includes a bus 102 and a communication interface 103. The processor 100, the communication interface 103 and the memory 101 are connected through the bus 102.

[0115] The memory 101 may include high-speed random access memory (RAM) and may also include non-volatile memory, such as at least one disk storage device. Communication between this system network element and at least one other network element is achieved through at least one communication interface 103 (which can be wired or wireless), such as the Internet, wide area network, local area network, metropolitan area network, etc. The bus 102 may be an ISA bus, PCI bus, or EISA bus, etc. The bus can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 4 The symbol is represented by a single double-headed arrow, but this does not mean that there is only one bus or one type of bus.

[0116] The processor 100 may be an integrated circuit chip with signal processing capabilities. In implementation, each step of the above method can be completed by the integrated logic circuitry in the hardware of the processor 100 or by instructions in software form. The processor 100 may be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc.; it may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this disclosure. The general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this disclosure can be directly manifested as execution by a hardware decoding processor, or execution by a combination of hardware and software modules in the decoding processor. The software module can reside in a readily available storage medium in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. This storage medium is located in memory 101, and the processor 100 reads the information from memory 101 and, in conjunction with its hardware, completes the steps of the method described in the foregoing embodiments.

[0117] This embodiment also provides a computer-readable storage medium storing computer-executable instructions. When the computer-executable instructions are called and executed by a processor, the computer-executable instructions cause the processor to implement the above-mentioned stepper motor thermal protection method for the vacuum valve.

[0118] The stepper motor thermal protection method for vacuum valves, the stepper motor, and the computer program product of the storage medium provided in this disclosure include a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the methods described in the preceding method embodiments. For specific implementation details, please refer to the method embodiments, which will not be repeated here.

[0119] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0120] Furthermore, in the description of the embodiments of this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure based on the specific circumstances.

[0121] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this disclosure, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this disclosure. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0122] In the description of this disclosure, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0123] Finally, it should be noted that the above embodiments are merely specific implementations of this disclosure, used to illustrate the technical solutions of this disclosure, and not to limit it. The protection scope of this disclosure is not limited thereto. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the scope of the technology disclosed in this disclosure. Such modifications, changes, 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 disclosure, and should all be covered within the protection scope of this disclosure. Therefore, the protection scope of this disclosure should be determined by the protection scope of the claims.

Claims

1. A method for thermal protection of a stepper motor in a vacuum valve, characterized in that, The method includes: The instantaneous current values ​​of the two-phase windings of the stepper motor are synchronously sampled at a preset sampling period. At the arrival of each sampling period, a first monitoring level corresponding to a first time scale is determined based on the instantaneous current sampling value of each phase winding; a second monitoring level corresponding to a second time scale is determined based on the window thermal load intensity value of each phase winding within a preset time window; and a third monitoring level corresponding to a third time scale is determined based on the instantaneous current sampling value of each phase winding and the historical thermal integral residual value retained from the previous sampling period; wherein, the window thermal load intensity value is the cumulative value of the square of the instantaneous current sampling value over time; Compare the levels of the first, second, and third monitoring levels of each phase winding, and determine the highest monitoring level as the target protection level for the current sampling period; Based on the target protection level, determine the target thermal protection action corresponding to the target protection level from a plurality of preset graded response actions, and execute the target thermal protection action; The determination of the third monitoring level corresponding to the third time scale based on the instantaneous current sampling value of each phase winding and the historical heat integral residual value retained from the previous sampling period includes: Based on the cumulative heat integral value of each phase winding in the previous sampling period and the ratio of the preset sampling period to the winding thermal time constant of the stepper motor, calculate the historical heat integral residual value of each phase winding after heat dissipation attenuation in the previous sampling period. The product of the square of the instantaneous current sample value of each phase winding in the current sampling period and the preset sampling period is used as the new heat value of each phase winding in the current sampling period. The historical heat integral residual value of each phase winding is added to the corresponding newly added heat value to obtain the cumulative heat integral value of each phase winding in the current sampling period; The cumulative heat integral value of each phase winding in the current sampling period is compared with the preset second reference value, and the third monitoring level corresponding to each phase winding in the third time scale is determined according to the comparison result; wherein, the preset second reference value is the product of the square of the rated current of the motor winding and the winding thermal time constant.

2. The method according to claim 1, characterized in that, The step of determining the first monitoring level corresponding to the first time scale based on the instantaneous current sampling values ​​of each phase winding includes: The instantaneous current sampling value of each phase winding is compared with the preset maximum allowable current value; wherein, the preset maximum allowable current value is the smaller of the absolute maximum current of the drive power device of the stepper motor and the instantaneous withstand current of the corresponding winding. If the instantaneous current sample value is greater than the preset maximum allowable current value, then the highest protection level is determined as the first monitoring level of the corresponding winding in the first time scale. If the instantaneous current sampling value is less than or equal to the preset maximum allowable current value, then the basic protection level is determined as the first monitoring level of the corresponding winding in the first time scale.

3. The method according to claim 1, characterized in that, The step of determining the second monitoring level corresponding to the second time scale based on the window thermal load intensity value of each phase winding within a preset time window includes: For each phase winding, within a preset time window of the current sampling period and the previous preset duration, the product of the square of the instantaneous current sampling value of each sampling period and the sampling period is accumulated to obtain the window thermal load intensity value corresponding to each phase winding; wherein, the preset duration is less than the winding thermal time constant of the stepper motor. The window thermal load intensity value corresponding to each phase winding is compared with a preset first reference value, and the second monitoring level corresponding to each phase winding in the second time scale is determined according to the comparison result; wherein, the preset first reference value is the product of the square of the rated current of the motor winding and the preset duration.

4. The method according to claim 1, characterized in that, The preset multiple graded response actions include at least three response actions corresponding to at least three protection levels from low to high; The step of determining the target thermal protection action corresponding to the target protection level from a set of preset graded response actions based on the target protection level, and executing the target thermal protection action, includes: When the target protection level is the basic protection level, the response action corresponding to the basic protection level is obtained from the preset multiple graded response actions, and is executed as the target thermal protection action. The response action corresponding to the basic protection level includes: recording a log and reporting a warning message to the host computer. When the target protection level is intermediate protection level, the response action corresponding to the intermediate protection level is obtained from the preset multiple graded response actions, and is executed as the target thermal protection action. The response action corresponding to the intermediate protection level includes: derating and limiting the current amplitude of the pulse width modulation drive signal. When the target protection level is a high protection level, the response action corresponding to the high protection level is obtained from the preset multiple graded response actions, and is executed as the target thermal protection action. The response action corresponding to the high protection level includes: pausing the motor's motion command or forcibly limiting the current.

5. The method according to claim 1, characterized in that, When the target protection level is the highest protection level, the step of determining the target thermal protection action corresponding to the target protection level from a plurality of preset graded response actions based on the target protection level, and executing the target thermal protection action, further includes: The hardware interlock signal is triggered to drive the valve to the closed position, and after confirming that the valve has responded to the closed position, the drive enable of the motor is cut off.

6. The method according to claim 5, characterized in that, The steps of triggering a hardware interlock signal to drive the valve to the closed position, and then cutting off the drive enable of the motor after confirming that the valve has responded to the closed position, include: A hardware interlock signal is output via a relay or optocoupler; wherein, the hardware interlock signal is connected to the interlock input terminal of the valve controller and is used to control the motor to drive the valve to move to the closed position; Read the confirmation status signal from the digital output terminal of the valve controller to confirm that the valve has actually responded to the closed position; After confirming that the valve has responded to the closed position, the drive enable of the motor is cut off; Record the trigger timestamp of the target thermal protection action, and report the trigger timestamp and fault information to the host computer.

7. The method according to claim 1, characterized in that, The method also includes: When a power failure signal is detected, the accumulated heat integral value of the current sampling period is written as the heat integral residual value into the non-volatile memory; When a power-on signal is detected, the residual thermal integral value is read from the non-volatile memory and used as the initial value of the historical residual thermal integral value after heat dissipation during the first recursive update after power-on.

8. A stepper motor, characterized in that, It includes a processor and a memory, the memory storing machine-executable instructions that can be executed by the processor, the processor executing the machine-executable instructions to implement the stepper motor thermal protection method for the vacuum valve according to any one of claims 1-7.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when invoked and executed by a processor, cause the processor to implement the stepper motor thermal protection method for the vacuum valve according to any one of claims 1-7.

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