A method and system for diagnosing operating conditions of a multi-stage conveying system

Abstract

The application provides a running state diagnosis method and system for a multi-stage conveying system, comprising: collecting no-load current values of two conveying devices on the same material channel in a no-load state; selecting a test period in a loaded running state, synchronously collecting real-time current sampling values of the two conveying devices, and calculating respective loaded current values; calculating average baseline current values and standard deviations of each conveying device in the test period; comparing the average baseline current values and standard deviations with those in the previous test period to determine whether the devices are in a normal running state; and if not, diagnosing as a process change or a conveying device failure. The application can accurately identify material quantity changes or conveying device failures by monitoring the relative current changes of two series-connected conveying devices in real time, taking the current change of one device as a reference, and cross- verifying the working state of the other device.

Description

Technical Field

[0001] This invention belongs to the field of bulk material conveying and metering monitoring technology in process industries, and in particular relates to a method and system for diagnosing the operating status of multi-stage conveying systems. Background Technology

[0002] In process industries such as cement, metallurgy, mining, and power generation, the precise and stable conveying and feeding of raw materials is a core prerequisite for ensuring product quality, production output, and energy consumption control. Metering and conveying equipment such as belt scales, screw scales, and plate flow meters perform the dual functions of real-time monitoring and control of material flow on the production line. These metering and conveying devices connect with multiple stages of conveying equipment, including elevators, belt conveyors, and screw conveyors, to form a complete material conveying system. Any abnormality in any operational link will directly affect the stability of the overall production process.

[0003] However, existing equipment condition monitoring systems still face many challenges in practical field applications.

[0004] On the one hand, equipment such as belt scales and belt conveyors rely heavily on manual inspection and control, lacking low-cost and easily implemented online intelligent monitoring methods. Common faults such as material jamming and transmission failure often worsen until they are detected as serious conditions such as equipment jamming and material interruption, screw conveyor running idle and causing material interruption, and belt slippage and overheating. This can easily lead to unplanned shutdowns and, in severe cases, damage to the conveying equipment itself, resulting in significant production interruption losses and equipment maintenance costs for enterprises.

[0005] On the other hand, in order to solve the problem of monitoring gaps caused by manual inspections, existing technologies attempt to achieve full-dimensional online monitoring by comprehensively installing dedicated sensing devices. However, this solution itself still has obvious defects: if full-dimensional status monitoring is achieved by installing dedicated sensing devices such as weighing, vibration, and infrared sensors on each level of conveying equipment, it will not only significantly increase the investment cost of on-site transformation, but also increase the difficulty of later equipment operation and maintenance and the number of failure points, making it difficult to widely apply on existing industrial production lines.

[0006] More critically, the most challenging issue in on-site operation and maintenance management lies in the fact that when the feedback parameters of metering and conveying equipment or conveying equipment at various levels deviate from the set process values, maintenance personnel cannot quickly and accurately trace the cause of the fault. They struggle to distinguish whether the anomaly is due to measurement deviations such as zero-point drift or inaccurate detection data caused by long-term equipment operation, or process changes caused by detached adhering materials, variations in the amount of conveyed material, or equipment jamming or transmission failure. Misjudgment can cause serious production disruptions: if the actual equipment fault is determined to be a measurement deviation, unnecessary equipment calibration will be performed, or the accumulated fault may lead to unexpected downtime; if the measurement deviation is determined to be an equipment fault, ineffective troubleshooting and repair will be conducted. Misjudgment increases production losses, and this pain point has long constrained the continuous and stable production operation of process industries.

[0007] The root cause of this problem is that the existing monitoring model relies solely on single-point operating parameters for judgment, and has not established a mechanism for analyzing the correlation of operating parameters between upstream and downstream conveying equipment. Therefore, it is impossible to accurately distinguish and trace the causes of failures through the linkage characteristics between equipment. Summary of the Invention

[0008] This invention breaks through the technical bias of traditional single-device independent monitoring and innovatively proposes a dual-device cross-reference diagnostic method and system based on current cross-verification. It removes measurement deviations from the principle level, effectively clarifies process changes and equipment faults, and realizes rapid and accurate determination of fault type and location, thus solving industry pain points.

[0009] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A method for diagnosing the operational status of a multi-stage conveying system includes the following steps: S1. When the multi-stage conveying system is in an unloaded state, collect the unloaded current values ​​of two conveying devices on the same material channel. S2. Under the condition of on-load operation, select a test cycle, synchronously collect the real-time current sampling values ​​of the two conveying devices, and subtract their respective no-load current values ​​to obtain their respective on-load current values. S3. Based on the on-load current value, calculate the average baseline current value and standard deviation of each conveying device during the test cycle; S4. Compare the average baseline current values ​​of the two conveying devices in the current test cycle with their average baseline current values ​​and standard deviation in the previous test cycle to determine whether the devices are in normal operating condition. S5. If the determination result is an abnormal operating state, then based on the relative change direction and magnitude of the average baseline current value, cross-diagnose it as a process change or a conveying equipment failure.

[0010] Furthermore, the two conveying devices are sequentially divided into an upstream conveying device and a downstream conveying device along the material conveying direction; in S2, the length of the test cycle is not less than the time required for the same wave of material to go from entering the upstream conveying device to leaving the downstream conveying device.

[0011] Furthermore, in S4, the criterion for determining normal operation is that the average baseline current values ​​of both conveying devices are within the range of the average baseline current value of their respective previous test cycle plus or minus three times the standard deviation.

[0012] Furthermore, in S5, if the average baseline current value of the upstream conveying equipment is greater than the average baseline current value of the previous test cycle plus three times the standard deviation, and the average baseline current value of the downstream conveying equipment is less than the average baseline current value of the previous test cycle minus three times the standard deviation, then it is determined that the upstream conveying equipment has a jamming fault.

[0013] Furthermore, in S5, if the average baseline current value of the upstream conveying equipment is within the range of the average baseline current value of the previous test cycle plus or minus three standard deviations, and the average baseline current value of the downstream conveying equipment is greater than the average baseline current value of the previous test cycle plus three standard deviations, then it is determined that the downstream conveying equipment has a jamming fault.

[0014] Furthermore, in S5, if the average baseline current value of the upstream conveying equipment is less than the average baseline current value of the previous test cycle minus three standard deviations, and the average baseline current value of the downstream conveying equipment is greater than the average baseline current value of the previous test cycle minus three standard deviations, then the material adhering to the upstream conveying equipment will fall off.

[0015] Furthermore, in S5, if the average baseline current value of the upstream conveying equipment is within the range of the average baseline current value of the previous test cycle plus or minus three times the standard deviation, and the average baseline current value of the downstream conveying equipment is less than the average baseline current value of the previous test cycle minus three times the standard deviation, then it is determined that the material adhering to the downstream conveying equipment has fallen off.

[0016] Furthermore, in S5, if the average baseline current value of any conveying device is less than 0, it is determined that the conveying device has a transmission failure fault.

[0017] Furthermore, in S5, if the average baseline current values ​​of both conveying devices are greater than the average baseline current value of their respective previous test cycle plus three times the standard deviation, or are less than the average baseline current value of their respective previous test cycle minus three times the standard deviation, then it is determined that the amount of conveyed material has changed.

[0018] Furthermore, when the multi-stage conveying system includes three or more conveying devices, any two conveying devices on the same material channel are divided into independent diagnostic units; each diagnostic unit is subjected to operational status diagnosis, and the diagnostic results of different diagnostic units are compared to accurately locate the fault.

[0019] An operational status diagnostic system for a multi-stage conveying system, used to execute the aforementioned operational status diagnostic method for a multi-stage conveying system, includes: The data acquisition module is used to simultaneously acquire the no-load current value and real-time current sampling value of the conveying equipment to be diagnosed; The signal processing and diagnostic engine is used to acquire the on-load current value of the conveying equipment, calculate the average baseline current value and standard deviation of each conveying equipment during the test cycle, determine whether the equipment is in normal operation, and perform fault diagnosis. The human-computer interaction and early warning module is used to display diagnostic results, fault quantification information, and early warning signals.

[0020] Furthermore, the signal processing and diagnostic engine includes: The data processing module is used to obtain the on-load current value of the conveying equipment and calculate the average baseline current value and standard deviation of each conveying equipment during the test cycle. The fault diagnosis module is used to compare the average baseline current value of the two conveying devices in the current test cycle with the average baseline current value and standard deviation in the previous test cycle, so as to determine whether the equipment is in normal operation and to perform fault diagnosis.

[0021] Furthermore, when the multi-level conveying system includes three or more conveying devices, and any two conveying devices on the same material channel are divided into independent diagnostic units, the fault diagnosis module is also used to summarize the diagnostic results of all diagnostic units in the multi-level conveying system and perform cross-verification.

[0022] Compared with existing technologies, the online diagnostic method and system for multi-level transmission equipment based on current cross-verification described in this invention has the following advantages: This invention breaks through the technical limitations of traditional single-device independent monitoring. It relies on the motor current data of two series-connected devices to achieve linked analysis. Through dynamic threshold determination, the operating status of one device is used as a reference to cross-verify the operating condition of the other device. This effectively removes the influence of measurement deviation, clarifies process changes and equipment failures, completely solves the problem of deviation in troubleshooting direction, enables rapid determination of fault type and location, accurately locates and distinguishes material jamming and transmission failure faults, reduces the probability of false alarms and missed alarms, and improves the overall accuracy of operating condition diagnosis and the efficiency of operation and maintenance.

[0023] This invention eliminates the need for additional specialized monitoring sensors such as weighing, vibration, and infrared sensors. The monitoring system can be built using only existing motor current acquisition signals on-site. It ensures long-term stable and reliable operation of the monitoring and diagnostic system without requiring frequent parameter calibration and instrument adjustment. This invention avoids the drawbacks of high modification costs and complex maintenance associated with adding new hardware, making it suitable for the retrofitting of various existing conveyor production lines and balancing production continuity with practical on-site value. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the overall process provided for an embodiment of the present invention; Figure 2 This is a schematic diagram of the conveying equipment provided in an embodiment of the present invention.

[0025] Explanation of reference numerals in the attached figures: 1. First belt; 11. First current sampling module; 12. Discharge end; 2. Second belt; 21. Second current sampling module; 22. Discharge end. Detailed Implementation

[0026] It should be noted that the "conveying equipment" mentioned in this invention refers to various equipment in process industry material conveying systems that perform material transfer functions, including but not limited to: pure conveying equipment such as belt conveyors, screw conveyors, bucket elevators, and chain conveyors, as well as metering and conveying equipment such as belt scales, screw scales, and plate flow meters that combine metering and conveying functions. Where there is no conflict, the embodiments and features in the embodiments of this invention can be combined with each other.

[0027] In the description of this invention, the directional terms are all based on the directions shown in the attached drawings and are only used to simplify the description. They are not intended to limit the actual installation structure or placement of the equipment. The terms "first" and "second" used in the text are only for distinguishing purposes and do not represent primary or secondary importance or sequence. The term "multi-level" in this invention is defined as two units, two or more units.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the term "installation" should be interpreted broadly. Those skilled in the art will understand the specific meaning of the above term in this invention based on the specific circumstances.

[0029] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] like Figures 1 to 2 As shown, a method for diagnosing the operational status of a multi-stage conveying system includes the following steps: S1. When the multi-stage conveying system is in an unloaded state, collect the current signals of two conveying devices on the same material channel and record the unloaded current value of each conveying device. S2. Under the condition of on-load operation, select a test cycle, synchronously collect the real-time current sampling values ​​of the two conveying devices, and subtract their respective no-load current values ​​to obtain their respective on-load current values. S3. Based on the on-load current value, calculate the average baseline current value and standard deviation of each conveying device during the test cycle; S4. Compare the average baseline current values ​​of the two conveying devices in the current test cycle with their average baseline current values ​​and standard deviation in the previous test cycle to determine whether the devices are in normal operating condition. S5. If the determination result is an abnormal operating state, then based on the relative change direction and magnitude of the average baseline current value, cross-diagnose it as a process change or a conveying equipment failure.

[0031] This invention compares and analyzes the current changes of two series-connected conveying devices on the same material channel, enabling status monitoring and fault diagnosis of the material conveying system without the need for additional sensors, thus reducing system modification costs. The dynamic threshold determination method based on statistics can avoid measurement deviations such as zero-point drift and inaccurate detection data caused by long-term operation of equipment, effectively avoiding false alarms and missed alarms.

[0032] Specifically, in S1, under the condition that the material conveying equipment is unloaded and operating stably, the motor current signals of two series-connected conveying devices (such as belt conveyors, screw conveyors, or bucket elevators) on the same material channel are synchronously acquired through the current sampling module. The current values ​​measured under this condition are recorded and stored as the unloaded current value of each conveying device, serving as the basis for subsequent calculations. This unloaded current value reflects the basic power consumption of the equipment itself, such as mechanical friction and transmission losses.

[0033] In S2, when the production line is feeding materials normally and the conveying equipment is operating under load, a fixed time window is selected as the test cycle. Within this cycle, real-time current sampling values ​​of the two conveying devices are synchronously collected at a predetermined sampling frequency (e.g., 1Hz). To eliminate the interference of the equipment's own basic power consumption on load judgment, the no-load current value of the corresponding device recorded in S1 is subtracted from each real-time current sampling value to obtain the on-load current value reflecting the change in material load.

[0034] In S3, the arithmetic mean of the on-load current values ​​obtained within the current test cycle is calculated, which is the average baseline current value of the conveying equipment within that test cycle. This value represents the average level of material load within that cycle. Simultaneously, the standard deviation of this on-load current value is calculated to quantify the normal fluctuation range of current under normal operating conditions caused by factors such as minor fluctuations in material flow and mechanical vibration.

[0035] In S4, the system calculates the average baseline current value for the current test cycle and compares it with the stored average baseline current value and standard deviation for the previous test cycle. The criterion for judgment is whether the current average baseline current values ​​of both devices fall within an allowable fluctuation range constructed based on historical data.

[0036] If both are within their respective allowable ranges, the device is determined to be in normal operating condition; otherwise, it is determined to be in abnormal operating condition, triggering further diagnostics.

[0037] In S5, once an abnormal operating condition is determined, a comprehensive analysis is performed on the relative changes in the average baseline current values ​​of the two conveying devices. Specifically, it compares whether the average baseline current values ​​of the two devices are "increasing" or "decreasing," and whether the magnitude of the change exceeds the normal threshold defined by "three times the standard deviation." By observing this "relative change," the root cause of the anomaly can be cross-validated and distinguished after removing the influence of measurement deviation: whether it is a process change (such as the shedding of adhered material) or a conveying device malfunction (such as jamming).

[0038] In a preferred embodiment of the present invention, the two conveying devices are sequentially divided into an upstream conveying device and a downstream conveying device along the material conveying direction; in S2, the length of the test cycle is not less than the time required for the same wave of material to go from entering the upstream conveying device to leaving the downstream conveying device.

[0039] Specifically, by limiting the minimum length of the test cycle, it is ensured that the current data collected within one cycle can fully cover the process of the same wave of material flowing through both devices. The calculated average baseline current value can accurately reflect the shared load effect of the material wave on the two devices, ensuring the temporal synchronization and physical correlation of the data from the upstream and downstream conveying equipment. If the test cycle is too short, it may only capture part of the material, leading to a distortion of the average baseline current value and reducing the accuracy of the diagnosis.

[0040] In a preferred embodiment of the present invention, in S4, the criterion for determining normal operation is that the average baseline current values ​​of the two conveying devices are both within the range of the average baseline current value of their respective previous test cycle plus or minus three times the standard deviation.

[0041] It should be noted that in this embodiment, the "average baseline current value plus or minus three standard deviations" is used as the judgment threshold. This is a conventional choice based on the 3σ principle of normal distribution in probability statistics. According to the 3σ principle, three standard deviations can cover approximately 99.73% of the normal data fluctuation range, achieving a balance between false positive and false negative rates. This is a conventional preferred solution in the field of anomaly detection.

[0042] Those skilled in the art will understand that three times the standard deviation is a preferred value in the technical solution of this invention and is not the core innovation of this invention. The core of this invention lies in establishing independent average baseline current values ​​for two conveying devices and comparing the baselines in different test cycles, thereby achieving effective monitoring of the equipment's operating status. Depending on the actual operating conditions of different equipment and the different requirements for false positive and false negative rates, those skilled in the art can adaptably choose other reasonable multiples such as 2 times, 2.5 times, 3.5 times, and 4 times as the judgment threshold without creative effort. These are all choices of conventional technical means and do not exceed the protection scope of this invention.

[0043] In a preferred embodiment of the present invention, in S5, if the average baseline current value of the upstream conveying equipment is greater than the average baseline current value of the previous test cycle plus three times the standard deviation, and the average baseline current value of the downstream conveying equipment is less than the average baseline current value of the previous test cycle minus three times the standard deviation, then it is determined that the upstream conveying equipment has a jamming fault.

[0044] Specifically, fault diagnosis is achieved by observing the relative direction of current changes between the two devices. The working principle is that, under normal operating conditions, the load currents of the upstream and downstream conveying devices exhibit a correlated trend. When the upstream conveying device experiences obstruction, the obstruction forces the blocked device to overcome greater friction or pushing force, resulting in a significant increase in the motor current of the upstream conveying device. This upstream obstruction leads to a decrease in the amount of material entering the downstream conveying device, causing a reverse change in the current of the downstream device, creating an operating characteristic of increased current upstream and decreased current downstream.

[0045] In a preferred embodiment of the present invention, in S5, if the average baseline current of the upstream conveying equipment is within the range of the average baseline current value of the previous test cycle plus or minus three times the standard deviation, and the average baseline current value of the downstream conveying equipment is greater than the average baseline current value of the previous test cycle plus three times the standard deviation, then it is determined that the downstream conveying equipment has a jamming fault.

[0046] Specifically, when downstream conveying equipment becomes jammed, the jammed equipment needs to overcome greater friction or pushing force, resulting in a significant increase in the motor current of the downstream conveying equipment. However, the upstream conveying equipment is unaffected by the downstream, creating an operating characteristic of stable upstream and increasing downstream.

[0047] In a preferred embodiment of the present invention, in S5, if the average baseline current value of the upstream conveying equipment is less than the average baseline current value of the previous test cycle minus three times the standard deviation, and the average baseline current value of the downstream conveying equipment is greater than the average baseline current value of the previous test cycle minus three times the standard deviation, then the material adhering to the upstream conveying equipment will fall off.

[0048] In S5, if the average baseline current value of the upstream conveying equipment is within the range of the average baseline current value of the previous test cycle plus or minus three standard deviations, and the average baseline current value of the downstream conveying equipment is less than the average baseline current value of the previous test cycle minus three standard deviations, then it is determined that the material adhering to the downstream conveying equipment has fallen off.

[0049] Specifically, a "material adhesion-detachment" phenomenon often occurs during material conveying, especially when conveying sticky or wet materials. Material adhesion increases equipment load, causing the current to rise slowly; however, when the adhered material accumulates to a certain extent and suddenly detaches, the current drops. When material adhering to upstream conveying equipment detaches and enters downstream conveying equipment, it causes the current in the downstream conveying equipment to rise. If material adhering to downstream conveying equipment detaches, it has no effect on the current in the upstream conveying equipment. Therefore, its current change characteristics perfectly match the diagnostic rules described above in this invention, identifying transient, non-periodic load fluctuations on the production line, avoiding misjudging them as equipment malfunctions, and improving the precision and accuracy of the diagnosis.

[0050] In a preferred embodiment of the present invention, in step S5, if the average baseline current value of any conveying device is less than 0, it is determined that the conveying device has a transmission failure fault.

[0051] Specifically, when a transmission failure occurs in the conveying equipment, the power transmission between the motor and the actuator (belt, screw, hopper) is interrupted. Although the equipment continues to rotate, it no longer bears the material load, and the motor's on-load current quickly drops back to near the no-load current. Theoretically, the average baseline current value should approach 0 at this point. However, due to factors such as fluctuations in on-site current sampling, baseline drift, and short-term interference, the calculated average baseline current value will fluctuate slightly around 0, occasionally showing a small negative value. Therefore, using a reduction in the average baseline current value to less than 0 as the criterion for determining transmission failure is consistent with engineering practice and has extremely high identification accuracy. This embodiment can issue early warnings before serious accidents such as belt overheating and burning, and screw idling and material breakage caused by transmission failure, greatly improving the safety of equipment operation.

[0052] In a preferred embodiment of the present invention, in S5, if the average baseline current values ​​of the two conveying devices are both greater than the average baseline current value of their respective previous test cycle plus three times the standard deviation, or both are less than the average baseline current value of their respective previous test cycle minus three times the standard deviation, then it is determined that the amount of conveyed material has changed.

[0053] Specifically, when the current of two devices exceeds the normal range synchronously and in the same direction, it is determined that the feed rate has changed in a real way. This avoids invalid calibration or incorrect maintenance due to misjudgment, guides maintenance personnel to make accurate decisions, and ensures the stability of the process and the continuity of production.

[0054] The logical judgment principle is shown in Table 1.

[0055] Table 1 Principles of Logical Judgment

[0056] In a further preferred embodiment of the present invention, when the method is applied to a multi-stage conveying production line containing three or more conveying devices, the conveying devices along the material conveying direction in the same material channel are paired into independent diagnostic units. Each diagnostic unit independently executes the above-mentioned operating status diagnostic method, thereby realizing systematic status monitoring and fault location of the entire production line; and the diagnostic results of different diagnostic units can corroborate each other.

[0057] For example, in an upstream diagnostic unit, if a downstream conveying device is diagnosed with a jamming fault, and this downstream conveying device is also the upstream conveying device of an adjacent downstream diagnostic unit, the two independent diagnostic units will simultaneously determine that the device has a jamming fault. Through this cross-unit alternating verification, the location of the faulty device can be further pinpointed, effectively improving the accuracy and reliability of the diagnostic results.

[0058] In a preferred embodiment of the present invention, an operational status diagnostic system for a multi-stage conveying system includes: The data acquisition module is used to simultaneously acquire the no-load current value and real-time current sampling value of the conveying equipment to be diagnosed; The signal processing and diagnostic engine is used to acquire the on-load current value of the conveying equipment, calculate the average baseline current value and standard deviation of each conveying equipment during the test cycle, determine whether the equipment is in normal operation and perform fault diagnosis; when the multi-level conveying system is divided into multiple diagnostic units, it is also used to summarize the diagnostic results of all the diagnostic units in the entire system and perform cross-verification. The human-computer interaction and early warning module is used to display diagnostic results, fault quantification information, and early warning signals.

[0059] When the multi-stage conveying system includes three or more conveying devices, any two conveying devices on the same material channel are divided into independent diagnostic units. When the multi-stage conveying system is divided into multiple diagnostic units... The data acquisition module is used to synchronously acquire the current signals of two transmission devices within the same diagnostic unit; The signal processing and diagnostic engine records the no-load current value for each diagnostic unit, calculates the average baseline current value and standard deviation under load operation, determines whether the equipment is in normal operation, and summarizes the diagnostic results of all diagnostic units in the entire system to achieve cross-verification of results across units. The human-computer interaction and early warning module is used to display the diagnostic results, fault quantification information and early warning signals of all diagnostic units in the entire system.

[0060] In a preferred embodiment of the present invention, the signal processing and diagnostic engine includes: The data processing module is used to record the no-load current value for each diagnostic unit and calculate the average baseline current value and standard deviation of each conveying device in the diagnostic unit during the test cycle. The fault diagnosis module compares the average baseline current value of the two conveying devices in the same diagnostic unit within the current test cycle with their average baseline current value and standard deviation in the previous test cycle to determine whether the equipment is in normal operating condition.

[0061] When the multi-stage conveying system includes three or more conveying devices, any two conveying devices on the same material channel are divided into independent diagnostic units. When the multi-stage conveying system is divided into multiple diagnostic units: The data processing module is used to obtain the on-load current value of the conveying equipment and calculate the average baseline current value and standard deviation of each conveying equipment during the test cycle. The fault diagnosis module is used to compare the average baseline current value of the two conveying devices in the current test cycle with the average baseline current value and standard deviation in the previous test cycle, so as to determine whether the equipment is in normal operation and to perform fault diagnosis. The cross-diagnostic module, when the multi-level conveying system is divided into multiple diagnostic units, summarizes the diagnostic results of all the diagnostic units in the entire system and performs cross-verification.

[0062] In a preferred embodiment of the present invention, the data acquisition module may employ a current transformer or Hall sensor installed in the motor control cabinet of two conveying devices, in conjunction with a PLC controller or an industrial IoT gateway to achieve real-time acquisition and data uploading of current signals.

[0063] The signal processing and diagnostic engine can be deployed on a local industrial control computer, edge computing node, or cloud server. It has built-in data processing algorithms and fault diagnosis logic to perform real-time calculations and status determination on the received current data.

[0064] The human-machine interaction and early warning module may include an on-site HMI touch screen, host computer monitoring software or mobile APP, used to display the equipment operating status, historical trends and fault alarm information in the form of visual charts, and supports multiple early warning notification methods such as sound, SMS or email.

[0065] The following section provides a complete and detailed description of the operational status diagnosis method and system for multi-stage conveying systems provided by this invention, based on specific experimental data. This embodiment is a specific implementation of the technical solution in a real industrial scenario and should not be construed as the sole limitation of this invention.

[0066] (I) Experimental Scenario and System Configuration This embodiment selects a raw material conveying line in a cement plant as the verification scenario, which is a typical bulk material conveying environment in a process industry. Specific parameters are as follows: Conveying Equipment: Two conveying devices were selected as two-stage belt conveyors connected in series, sequentially divided into an upstream first belt 1 and a downstream second belt 2 along the material conveying direction. The width of both the first belt 1 and the second belt 2 is 1000mm, the belt speed is 1.6m / s, and the rated power is 75kW and 90kW, respectively. Both conveyors selected for this verification have been in operation for over 10 years, and their aging results in a high failure rate, thus fully validating the effectiveness of this diagnostic method. It should be noted that although this embodiment uses a two-stage belt conveyor as an example, this invention is also applicable to other types of conveying equipment combinations, such as: an upstream screw conveyor (which combines metering and conveying functions) and a downstream belt conveyor; or an upstream belt conveyor and a downstream bucket elevator, etc.

[0067] Material characteristics: Cement raw meal, normal conveying capacity is 200t / h.

[0068] Current sampling: The first belt 1 and the second belt 2 are respectively equipped with an independent first current sampling module 11 and a second current sampling module 21, which synchronously collect the corresponding motor operating current signals in real time with a sampling frequency of 1Hz and an accuracy of 0.1A.

[0069] Verification and judgment methods: By using a preset test cycle (covering the complete conveying time of material from the feed end of the first belt 1 to the discharge end 22 of the second belt 2), the average baseline current and standard deviation are dynamically calculated. The average baseline current change of adjacent cycles is used as the criterion. Combined with the relative direction and amplitude of the current changes of the two belts, the predefined diagnostic rules are matched, and finally the specific abnormality type (such as jamming, transmission failure, etc.) and positioning position (such as the second belt 2) are output.

[0070] Verification period: 1 month.

[0071] (II) Implementation steps of online diagnostic methods With the conveyor equipment running stably under no-load conditions for 5 minutes, the motor current signals of the first belt 1 and the second belt 2 are synchronously collected via the data acquisition module. The no-load current value I of the first belt 1 is recorded. 10 =42A, the no-load current of the second belt 2 is I 20 =38A. These two values ​​are stored in the signal processing and diagnostic engine as a benchmark for subsequent calculations.

[0072] Once the production line is operating normally (with load), a test cycle is selected. Actual measurements show that the conveying time for the same wave of material from the inlet of the first belt 1 to the outlet of the second belt 2 is approximately 8 minutes. Therefore, in this embodiment, the test cycle is set to 10 minutes to ensure complete coverage of the material flow process.

[0073] During the 10-minute test period, real-time current sampling values ​​of the two conveyor systems were synchronously acquired at a frequency of 1Hz, resulting in the current sequence {I1(t)} of the first conveyor belt 1 and the current sequence {I2(t)} of the second conveyor belt 2 (t=1,2,...,N, N=600, where N is the total number of sampling points). Then, the corresponding no-load current values ​​were subtracted from each to obtain the sequence of loaded current values. 1(t) = I1(t) - I 10 , 2(t) = I²(t) - I 20 This embodiment underwent a total of 4320 test cycles.

[0074] For the sequence of on-load current values ​​within the current test cycle, calculate the average baseline current value and standard deviation of the first belt 1 and the second belt 2 respectively: Average baseline current value of the first belt 1: 1= ; Average baseline current value of the second belt 2: 2= ; Standard deviation of the first belt 1: σ1=( ) 0.5; The standard deviation of the second belt 2: σ2=( ) 0.5 .

[0075] Taking the first test cycle (i.e., the first 10 minutes after the equipment starts feeding materials) as an example, the calculation is as follows: σ1 = 18A, σ1 = 2.1A; 2 = 22A, σ² = 2.5A. Taking the second test cycle as an example, the baseline of the previous test cycle (the first test cycle) was: The allowable range for the first belt 1 is [18-3×2.1, 18+3×2.1]=[11.7A, 24.3A]; The allowable range for the second belt 2 is [22-3×2.5, 22+3×2.5]=[14.5A, 29.5A].

[0076] If measured in the second period 1 and If each of the above intervals falls within a certain range, the system is considered to be operating normally; otherwise, proceed to the next step for detailed anomaly assessment.

[0077] The following describes several typical abnormal operating conditions that occurred during 30 consecutive days of operation (4320 test cycles in total, each cycle lasting 10 minutes) in this embodiment.

[0078] Operating Condition 1: Normal Operation Verification During most test cycles of stable material conveying (200t / h±5%), the average baseline current values ​​of the two conveying devices remained stable within the range of the average baseline current value of their respective previous cycles plus or minus three times the standard deviation. The system continuously output normal operating status and did not trigger any warnings.

[0079] Operating Condition 2: Second Belt 2 jamming fault In the 152nd test cycle, the average baseline current value of the second belt 2 suddenly increased from 22A in the previous cycle to 30A. Calculations showed its upper limit (average baseline current value of the previous cycle plus three standard deviations) was 22 + 3 × 2.5 = 29.5A, which 30A exceeded. Meanwhile, the average baseline current value of the first belt 1 was 18.5A, still within its allowable range (average baseline current value of the previous cycle plus or minus three standard deviations) [11.7A, 24.3A (18 ± 3 × 2.1 = 11.7A ~ 24.3A)]. Based on the rule that "the average baseline current of the upstream conveyor is within the range of the average baseline current value of the corresponding previous test cycle plus or minus three standard deviations, while the average baseline current value of the downstream conveyor is greater than the range of the average baseline current value of the previous test cycle plus three standard deviations," the system determined that the downstream conveyor, i.e., the second belt 2, had a material jamming fault. After a warning, manual confirmation revealed that material caking at the discharge end 22 of the second belt 2 was causing the jamming, with a positioning accuracy of 100%. A similar fault occurred during the 3851st test cycle. Thanks to timely warnings, maintenance personnel were able to clear and resolve the issue in its initial stages within 5 minutes, preventing production line downtime and effectively avoiding unplanned downtime losses.

[0080] Operating Condition 3: Adhered material falls off In the 283rd test cycle, the average baseline current value of the first conveyor belt 1, 18.7A, was within the range of the average baseline current value of the previous test cycle plus or minus three standard deviations (18-3×2.0=12.0A, 18+3×2.0=24.0A). The average baseline current value of the second conveyor belt 2 dropped sharply from 22A in the previous cycle to 14A, which was less than the average baseline current value of the previous cycle minus three standard deviations, 14.5A (22-3×2.5=14.5A). Based on the rule that "if the average baseline current value of the upstream conveyor is within the range of the average baseline current value of the previous test cycle plus or minus three standard deviations, and the average baseline current value of the downstream conveyor is less than the average baseline current value of the previous test cycle minus three standard deviations," the system determined that there was material detachment from the second conveyor belt 2. Manual confirmation confirmed that the large pieces of raw material previously adhered to the second conveyor belt 2 had completely detached.

[0081] In the 1767th test cycle, the average baseline current value of the first conveyor belt 1 was 10.7A, which was less than the average baseline current value of the previous test cycle minus three standard deviations (18-3×2.0=12.0A). The average baseline current value of the second conveyor belt 2 surged to 31A, exceeding the average baseline current value of the previous cycle plus three standard deviations (22+3×2.4=29.2A). Based on the rule that "if the average baseline current value of the upstream conveyor is less than the average baseline current value of the previous test cycle minus three standard deviations, and the average baseline current value of the downstream conveyor is greater than the average baseline current value of the previous test cycle minus three standard deviations," the system determined that there was material detachment from the second conveyor belt 1. Manual confirmation revealed that the large pieces of raw material previously adhering to the first conveyor belt 1 had completely detached.

[0082] Operating Condition 4: Transmission Failure In the 421st test cycle, the average baseline current value of the second belt 2 was calculated to be -3A. Based on the rule that "if the average baseline current value of any conveyor is less than 0, then the conveyor is determined to have a transmission failure fault," the system determined that the second belt 2 had a transmission failure fault. On-site inspection revealed that insufficient belt tension caused slippage. After adjustment, normal operation was restored within 5 minutes. This was resolved before the fault progressed to a serious stage, preventing a belt burnout accident and subsequent unplanned downtime. The first belt 1 did not experience a transmission failure fault.

[0083] Operating Condition 5: First belt 1 jamming fault In the 1877th test cycle, the average baseline current value of the first conveyor belt 1 surged from 18A in the previous cycle to 35A. Calculations showed its upper limit (average baseline current value of the previous cycle plus three standard deviations) was 25.5A (18 + 3 × 2.4 = 25.5A), exceeding this limit. Simultaneously, the average baseline current value of the second conveyor belt 2 was 11.5A, less than its lower limit (average baseline current value of the previous cycle minus three standard deviations) of 12.0A (18 - 3 × 2.0 = 12.0A). Based on the rule that "if the average baseline current value of the upstream conveyor is greater than the range of the average baseline current value of the previous test cycle plus three standard deviations, and the average baseline current value of the downstream conveyor is less than the range of the average baseline current value of the previous test cycle minus three standard deviations," the system determined that the upstream conveyor, i.e., the first conveyor belt 1, had a material jamming fault and issued a warning. After manual confirmation following the warning, it was found that material caking at 12 points on the discharge end of the first conveyor belt 1 was causing the jamming, with a positioning accuracy of 100%. Thanks to the timely warning, maintenance personnel were able to clear and resolve the issue in the early stages of the blockage within 5 minutes, preventing production line downtime and effectively avoiding unplanned downtime losses.

[0084] Operating Condition 6: Change in the amount of material being conveyed When the upstream feed rate was actively adjusted from 200t / h to 230t / h, in the 2604th test cycle, the average baseline current of the first belt 1 rose to 26A, exceeding the average baseline current of the previous cycle plus three standard deviations (24.3A) (18 + 3 × 2.1 = 24.3A); the average baseline current of the second belt 2 rose to 32A, exceeding the average baseline current of the previous cycle plus three standard deviations (29.5A) (22 + 3 × 2.5 = 29.5A). Both devices increased synchronously and in the same direction. Based on the rule that "if the average baseline current value of either conveyor is greater than the average baseline current value of its previous test cycle plus three standard deviations, or less than the average baseline current value of its previous test cycle minus three standard deviations, then it is determined as a change in the conveyed material quantity," the system correctly output "Change in conveyed material quantity" instead of conveyor equipment failure.

[0085] (III) Comparative Analysis with Traditional Solutions Comparative example (traditional approach): To compare the effectiveness of this invention, a traditional monitoring scenario on the same production line without the implementation of this method was selected as a comparative example, as follows: Monitoring methods: Relying on manual inspections (once every 2 hours) and surveillance cameras; metering equipment (belt scale) only provides flow data, without any equipment status correlation analysis.

[0086] Comparison time: One month before the on-site verification of the method of the present invention was carried out on the raw material conveying line of the cement plant.

[0087] Anomaly detected: Jamming faults (including jamming faults of first belt 1 and second belt 2, similar to conditions 2 and 5): Jamming faults occurred a total of 3 times. During worker inspections, first belt 1 was found to be jammed once and second belt 2 was found to be jammed once, with an average on-site cleanup time of 1 hour, which did not affect production; jamming of first belt 1 caused a trip to the stop once, resulting in a 2-hour downtime, but the motor belt was not damaged.

[0088] Identifying adhered material detachment (similar to condition 3): Not identified as it did not affect normal production.

[0089] Transmission failure (similar to working condition 4): A transmission failure occurred once. It was not detected in the control room. During the workers' inspection, it was found that the belt tension was insufficient, causing slippage. After adjustment, it returned to normal, which took 20 minutes and did not cause any loss.

[0090] Changes in the amount of material being conveyed (similar to working condition 6): The operator identifies the change based on their own operation records, and there are no errors.

[0091] Because there was no current baseline for comparison, the operator suspected that the "measurement was inaccurate". After a meeting of the production department, external personnel were invited to calibrate the equipment once.

[0092] Through 4320 test cycles, the key performance indicators of the embodiments of the present invention were compared with those of the traditional solutions, and the comparison results are shown in Table 2: Table 2 Comparison of Key Performance Indicators

[0093] Based on the data from a month-long on-site comparison and verification, and statistical calculations based on the failure patterns, it is estimated that long-term application of this technical solution on the production line, through early warning and rapid response, can reduce the number of unplanned downtimes and equipment damage frequency caused by jamming and transmission failures to about 10% of the original level of traditional solutions. At the same time, it can completely avoid invalid calibrations caused by the inability to distinguish operating conditions, reducing the number of invalid calibrations to about 25% of the original level of traditional solutions, providing clear data support for improving the economic efficiency and reducing energy consumption of the production line in the future.

[0094] (iv) Economic Benefit Analysis This invention underwent on-site verification at a cement plant's raw material conveying line for 30 consecutive days (4320 test cycles). The two conveyors selected for verification were both aging equipment that had been in operation for over 10 years, exhibiting a high failure rate, thus fully validating the practical application effectiveness of this diagnostic method. Based on the verification data, the estimated annual economic benefits are as follows: 1) Reduce losses from unplanned downtime Under the traditional approach, the production line experiences an average of about one unplanned shutdown per month due to jamming or transmission failure, with each shutdown lasting an average of 2 hours. Based on the production line's capacity of 200t / h and a unit profit of about 50 yuan / ton for cement raw materials, the direct loss from a single shutdown is about 20,000 yuan.

[0095] After applying this invention, early warning of faults can be achieved, and unplanned downtime is expected to be reduced to 0.1 times / month.

[0096] Annual reduction in downtime losses: 2 × (1 - 0.1) × 12 = 216,000 yuan / year 2) Reduce the cost of invalid calibration Under traditional methods, it is impossible to distinguish between "inaccurate measurement" and "equipment malfunction," requiring an average of two calibrations per year. Each calibration necessitates hiring external professional verification personnel, with a total cost of approximately 10,000 yuan per calibration. After applying this invention, the error rate is reduced to 0%, and the calibration operation is expected to be reduced to 0.5 times per year.

[0097] Annual calibration cost savings: 1 × (2 - 0.5) = 15,000 yuan / year 3) Avoid equipment damage and repair costs During the verification period, this invention successfully provided early warning of one transmission failure and three jamming failures, all of which were detected and addressed in their early stages, preventing serious accidents such as belt burnout and motor overload damage. Based on past experience, the motor is repaired once a year and the belt twice a year, with motor repair costs of 20,000 yuan per repair and belt repair costs of 10,000 yuan per repair.

[0098] Annual maintenance losses avoided: 2 × (1 - 0.1) + 1 × (2 - 0.2) = 36,000 yuan / year 4) Energy saving and emission reduction benefits Reducing energy waste caused by unplanned shutdowns, based on an estimated 1000 kWh of additional electricity consumption for restarting the production line after each shutdown and an electricity price of 0.6 yuan / kWh, would result in annual electricity savings of approximately (1-0.1)×12×1000=10,800 kWh, equivalent to a saving of 6,480 yuan in electricity costs. Based on the national average carbon emission factor of 0.5306 kgCO2 / kWh, this corresponds to a CO2 emission reduction of approximately 5.73 tons / year.

[0099] In summary, the application of this invention in a single cement plant can generate direct economic benefits of approximately RMB 273,480 per year and reduce carbon emissions by 5.73 tons per year.

[0100] According to incomplete statistics, there are approximately 1,500 similar production lines in the domestic cement industry alone. Each cement production line has at least 20 similar conveying devices. Assuming a 50% penetration rate, this would generate approximately 27.348 × (20 ÷ 2) × 1500 × 50% ≈ 2 billion yuan in economic benefits annually, while simultaneously reducing CO2 emissions by approximately 43,000 tons annually. This invention provides a new, low-cost, low-intrusion, and highly reliable technological path for the intelligent upgrading and transformation of existing conveying equipment in process industries. It has significant demonstrative value for promoting technological upgrading in traditional industries such as cement, metallurgy, mining, and power, and overall possesses significant economic and social benefits and broad prospects for widespread application.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for diagnosing the operational status of a multi-stage conveying system, characterized in that, Includes the following steps: S1. When the multi-stage conveying system is in an unloaded state, collect the unloaded current values ​​of two conveying devices on the same material channel. S2. Under the condition of on-load operation, select a test cycle, synchronously collect the real-time current sampling values ​​of the two conveying devices, and subtract their respective no-load current values ​​to obtain their respective on-load current values. S3. Based on the on-load current value, calculate the average baseline current value and standard deviation of each conveying device during the test cycle; S4. Compare the average baseline current values ​​of the two conveying devices in the current test cycle with their average baseline current values ​​and standard deviation in the previous test cycle to determine whether the devices are in normal operating condition. S5. If the determination result is an abnormal operating state, then based on the relative change direction and magnitude of the average baseline current value, cross-diagnose it as a process change or a conveying equipment failure.

2. The method for diagnosing the operating status of a multi-stage conveying system according to claim 1, characterized in that: The two conveying devices are sequentially divided into an upstream conveying device and a downstream conveying device along the material conveying direction; in S2, the length of the test cycle is not less than the time required for the same wave of material to go from entering the upstream conveying device to leaving the downstream conveying device.

3. The method for diagnosing the operating status of a multi-stage conveying system according to claim 1, characterized in that: In S4, the standard for determining normal operation is that the average baseline current values ​​of the two conveying devices are both within the range of the average baseline current value of their respective previous test cycle plus or minus three times the standard deviation.

4. The method for diagnosing the operating status of a multi-stage conveying system according to claim 2, characterized in that: In S5, if the average baseline current value of the upstream conveying equipment is greater than the average baseline current value of the previous test cycle plus three times the standard deviation, and the average baseline current value of the downstream conveying equipment is less than the average baseline current value of the previous test cycle minus three times the standard deviation, then it is determined that the upstream conveying equipment has a jamming fault.

5. The method for diagnosing the operating status of a multi-stage conveying system according to claim 2, characterized in that: In S5, if the average baseline current value of the upstream conveying equipment is within the range of the average baseline current value of the previous test cycle plus or minus three standard deviations, and the average baseline current value of the downstream conveying equipment is greater than the average baseline current value of the previous test cycle plus three standard deviations, then it is determined that the downstream conveying equipment has a jamming fault.

6. The method for diagnosing the operating status of a multi-stage conveying system according to claim 2, characterized in that: In S5, if the average baseline current value of the upstream conveying equipment is less than the average baseline current value of the previous test cycle minus three standard deviations, and the average baseline current value of the downstream conveying equipment is greater than the average baseline current value of the previous test cycle minus three standard deviations, then it is determined that the material adhering to the upstream conveying equipment has fallen off.

7. The method for diagnosing the operating status of a multi-stage conveying system according to claim 2, characterized in that: In S5, if the average baseline current value of the upstream conveying equipment is within the range of the average baseline current value of the previous test cycle plus or minus three standard deviations, and the average baseline current value of the downstream conveying equipment is less than the average baseline current value of the previous test cycle minus three standard deviations, then it is determined that the material adhering to the downstream conveying equipment has fallen off.

8. The method for diagnosing the operating status of a multi-stage conveying system according to claim 1, characterized in that: In S5, if the average baseline current value of any conveying device is less than 0, it is determined that the conveying device has a transmission failure fault.

9. The method for diagnosing the operating status of a multi-stage conveying system according to claim 1, characterized in that: In S5, if the average baseline current values ​​of the two conveying devices are both greater than the average baseline current value of their respective previous test cycle plus three times the standard deviation, or both are less than the average baseline current value of their respective previous test cycle minus three times the standard deviation, then it is determined that the amount of conveyed material has changed.

10. The method for diagnosing the operating status of a multi-stage conveying system according to claim 1, characterized in that: When the multi-stage conveying system includes three or more conveying devices, any two conveying devices on the same material channel are divided into independent diagnostic units; the operating status of each diagnostic unit is diagnosed separately, and the diagnostic results of different diagnostic units are compared to accurately locate the fault.

11. A system for diagnosing the operational status of a multi-stage conveying system, used to execute the method for diagnosing the operational status of a multi-stage conveying system as described in any one of claims 1-10, characterized in that, include: The data acquisition module is used to simultaneously acquire the no-load current value and real-time current sampling value of the conveying equipment to be diagnosed; The signal processing and diagnostic engine is used to obtain the on-load current value of the conveying equipment and calculate the average baseline current value and standard deviation of each conveying equipment during the test cycle. And determine whether the equipment is in normal operating condition and perform fault diagnosis; The human-computer interaction and early warning module is used to display diagnostic results, fault quantification information, and early warning signals.

12. The operational status diagnostic system for a multi-stage conveying system according to claim 11, characterized in that, The signal processing and diagnostic engine includes: The data processing module is used to obtain the on-load current value of the conveying equipment and calculate the average baseline current value and standard deviation of each conveying equipment during the test cycle. The fault diagnosis module is used to compare the average baseline current value of the two conveying devices in the current test cycle with the average baseline current value and standard deviation in the previous test cycle, so as to determine whether the equipment is in normal operation and to perform fault diagnosis.

13. The operational status diagnostic system for a multi-stage conveying system according to claim 12, characterized in that: When the multi-level conveying system includes three or more conveying devices, and any two conveying devices on the same material channel are divided into independent diagnostic units, the fault diagnosis module is also used to summarize the diagnostic results of all diagnostic units in the multi-level conveying system and perform cross-verification.

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