Plc automatic control method and system for concrete mixing plant

Abstract

The application discloses a PLC automatic control method and system for a concrete mixing station, and relates to the technical field of concrete mixing control. The method comprises the following steps: analyzing the performance of the concrete mixing station based on the production process of ultra-high performance concrete, deploying compensation hardware, and establishing a mapping relationship between the compensation hardware and compensation parameters; performing a pre-production self-check, sequentially executing a segmented mixing process, automatically controlling the rotating speed and mixing time of the mixing host by the PLC controller according to the preset segmented process parameters, controlling the feeding sequence and feeding mode, automatically calling the corresponding compensation hardware according to the real-time detected process parameters, adjusting the compensation parameters according to the mapping relationship, and maintaining the process within the target range. The technical problem that the product quality consistency is poor due to the influence of raw material fluctuation, equipment state change and process disturbance in the production process of ultra-high performance concrete in the prior art is solved, and the technical effects of improving the product quality stability and consistency are achieved.

Description

Technical Field

[0001] This invention relates to the field of concrete mixing control technology, specifically to a PLC automatic control method and system for concrete mixing plants. Background Technology

[0002] Ultra-high performance concrete (UHPC) is a new type of cement-based composite material with ultra-high strength, high durability, high impermeability, and excellent crack resistance. It is widely used in bridge engineering, prefabricated buildings, marine engineering, and special protective structures. Because UHPC typically employs a low water-cement ratio design and incorporates various components such as silica fume, mineral admixtures, water-reducing agents, and steel fibers, its production process places high demands on the accuracy of raw material metering, the order of feeding, the mixing intensity, the mixing time, and the control of flowability. Most existing concrete mixing plants use PLC control systems to automate the batching, feeding, and mixing processes. However, most control methods still rely on fixed process parameters and preset control logic, lacking the ability to perform refined, segmented control of the UHPC production process. When the moisture content of raw materials changes, the performance of admixtures fluctuates, the steel fiber feeding status is abnormal, or the equipment operating conditions change, existing control systems struggle to dynamically adjust and compensate for the mixing parameters in a timely manner. This can easily lead to increased deviations in concrete flowability, decreased uniformity of steel fiber dispersion, and unstable mixing quality, ultimately affecting the performance stability and product quality consistency of UHPC. Summary of the Invention

[0003] This application provides a PLC automatic control method and system for concrete mixing plants, which solves the technical problem of poor product quality consistency caused by fluctuations in raw materials, changes in equipment status and process disturbances during the production of ultra-high performance concrete in the prior art.

[0004] The first aspect of this application provides a PLC automatic control method for a concrete mixing plant, the method comprising:

[0005] Based on the production process of ultra-high performance concrete, the performance of the concrete mixing plant is analyzed, compensation hardware is deployed, and a mapping relationship between the compensation hardware and compensation parameters is established. The production mode of ultra-high performance concrete is initialized, a pre-production self-inspection is performed, and the segmented mixing process is executed sequentially. The segmented mixing process includes a dry material premixing stage, an initial wet mixing stage, a fluidity closed-loop fine adjustment stage, a steel fiber feeding stage, a homogeneous fine mixing stage, and an interlocked discharge stage. At each stage, the PLC controller automatically controls the speed and mixing time of the mixing host according to the preset segmented process parameters, controls the feeding sequence and feeding method, and automatically calls the corresponding compensation hardware according to the real-time detected process parameters, adjusts the compensation parameters according to the mapping relationship, and maintains the process within the target range.

[0006] A second aspect of this application provides a PLC automatic control system for a concrete mixing plant, the system comprising:

[0007] Analysis Module: Based on the production process of ultra-high performance concrete, the performance of the concrete mixing plant is analyzed, compensation hardware is deployed, and a mapping relationship between the compensation hardware and compensation parameters is established. Compensation Control Module: Initializes the production mode of ultra-high performance concrete, performs pre-production self-check, and sequentially executes the segmented mixing process. The segmented mixing process includes a dry material premixing stage, an initial wet mixing stage, a fluidity closed-loop fine adjustment stage, a steel fiber feeding stage, a homogeneous fine mixing stage, and an interlocked discharge stage. In each stage, the PLC controller automatically controls the speed and mixing time of the mixing host according to the preset segmented process parameters, controls the feeding sequence and feeding method, and automatically calls the corresponding compensation hardware according to the real-time detected process parameters, adjusts the compensation parameters according to the mapping relationship, and maintains the process within the target range.

[0008] One or more technical solutions provided in this application have at least the following technical effects or advantages:

[0009] This paper analyzes the performance of a concrete mixing plant based on the production process of ultra-high performance concrete (UHVPC), deploys compensation hardware, and establishes a mapping relationship between the compensation hardware and compensation parameters. The UHVPC production mode is initialized, pre-production self-inspection is performed, and a segmented mixing process is executed sequentially. This segmented mixing process includes a dry premixing stage, an initial wet mixing stage, a fluidity closed-loop fine-tuning stage, a steel fiber feeding stage, a homogenized fine mixing stage, and an interlocked discharge stage. At each stage, the PLC controller automatically controls the speed and mixing time of the mixing host according to preset segmented process parameters, controls the feeding sequence and method, and automatically calls the corresponding compensation hardware based on real-time detected process parameters, adjusting the compensation parameters according to the mapping relationship to maintain the process within the target range. This solves the technical problem of poor product quality consistency caused by fluctuations in raw materials, changes in equipment status, and process disturbances in the production process of UHVPC, achieving the technical effect of improving product quality stability and consistency. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 A schematic diagram of a PLC automatic control method for a concrete mixing plant provided in an embodiment of this application;

[0012] Figure 2This is a schematic diagram of the structure of a PLC automatic control system for a concrete mixing plant, provided in an embodiment of this application.

[0013] Explanation of reference numerals in the attached diagram: Analysis module 11, Compensation control module 12. Detailed Implementation

[0014] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0015] Example 1, as Figure 1 As shown, this application provides a PLC automatic control method for concrete mixing plants, wherein the method includes:

[0016] Based on the production process of ultra-high performance concrete, the performance of concrete mixing plants is analyzed, compensation hardware is deployed, and a mapping relationship between the compensation hardware and compensation parameters is established.

[0017] Specifically, based on the production process requirements of ultra-high performance concrete (UHVPC), an adaptability analysis was conducted on the concrete batching plant to identify key process steps affecting the production quality of UHVPC. Corresponding compensation hardware was then configured for areas with insufficient control capabilities to enhance the batching plant's adaptability to the UHVPC production process. Subsequently, the deployed compensation hardware underwent parameter configuration, communication connection, and functional verification. A correspondence between the compensation hardware and compensation parameters was established, enabling different compensation hardware to perform corresponding compensation adjustments for different process parameter deviations. The compensation parameters characterize the output adjustment amount of the compensation hardware, and the correspondence between the compensation hardware and compensation parameters guides the PLC controller to automatically invoke the corresponding compensation hardware for compensation control during production based on real-time detected process parameter deviations. This provides the foundation for the automatic execution and closed-loop adjustment of the subsequent segmented mixing process.

[0018] Furthermore, the performance analysis of concrete mixing plants based on the production process of ultra-high performance concrete includes:

[0019] This study analyzes the performance deficiencies of ordinary mixing plants in various dimensions, including metering accuracy, mixing and shearing capacity, fiber feeding uniformity, and environmental adaptability. Based on these performance deficiencies, corresponding compensation hardware is deployed. This compensation hardware includes: an independent high-precision weighing hopper for ultrafine powders, an electromagnetic flowmeter pulse metering system for admixtures, a variable frequency vibrating fiber feeder, and real-time sensors for material temperature and flowability. Based on the correspondence between the compensation hardware and the performance deficiencies, a mapping relationship between the compensation hardware and compensation parameters is established. This mapping relationship includes a functional correspondence between the output adjustment of each compensation hardware and the deviation of the target process parameters.

[0020] Preferably, the process requirements parameters for ultra-high performance concrete are retrieved, including powder metering accuracy requirements, target water-cement ratio range, steel fiber dosage range, target flowability range, target material temperature range, and mixing intensity requirements at each stage. These process requirements parameters are then used as evaluation benchmarks to assess the performance of ordinary concrete mixing plants. Specifically, regarding metering accuracy, the actual metering errors of powder, water, and admixtures are statistically analyzed. If the metering error exceeds a preset allowable deviation, a deficiency in metering accuracy performance is identified. Regarding mixing shear capacity, data on load current, torque changes, and mixing uniformity of the mixing host at different speeds are collected. If the uniform dispersion effect required for ultra-high performance concrete cannot be achieved, a deficiency in mixing shear capacity performance is identified. Regarding fiber feeding uniformity, the fluctuation rate of steel fiber feeding per unit time and fiber agglomeration rate are statistically analyzed. If these exceed a preset threshold, a deficiency in fiber feeding uniformity performance is identified. Regarding environmental adaptability, fluctuations in production environment temperature, raw material temperature, and finished product temperature are monitored. If temperature changes cause the flowability to deviate from the target range, a deficiency in environmental adaptability performance is identified.

[0021] Based on the identified performance deficiency characteristics, corresponding compensation hardware is deployed. Specifically, when there is a deficiency in metering accuracy, an independent high-precision weighing hopper for ultrafine powder is installed in the ultrafine powder feeding channel, and an admixture electromagnetic flowmeter pulse metering system is installed in the admixture dosing channel. When there is a deficiency in fiber feeding uniformity, a variable frequency vibrating fiber feeder is installed in the steel fiber feeding channel. When there is a deficiency in environmental adaptability, real-time material temperature and flowability sensors are installed at the discharge port of the mixing host, inside the mixing cylinder, or in the conveying channel. After the compensation hardware deployment is completed, the parameters of each compensation hardware component are calibrated to obtain the change in process parameters corresponding to the unit output change of the compensation hardware.

[0022] Based on the correspondence between compensation hardware and performance deficiency characteristics, a mapping relationship between compensation hardware and compensation parameters is established. Specifically, this involves collecting flowability deviation, material temperature deviation, fiber feeding uniformity deviation, and corresponding compensation hardware adjustment data under different production conditions to construct a compensation sample set. Based on this sample set, the influence of changes in the output adjustment of each compensation hardware on the target process parameters is statistically analyzed, and a compensation rule relationship is established. When the flowability is below the target lower limit, a correspondence is established between the flowability deviation and the opening time of the micro-water supply valve, and water supply compensation parameters are generated. When the flowability is above the target upper limit, a correspondence is established between the flowability deviation and the number of revolutions of the ash supply screw conveyor. The system generates ash compensation parameters; when the material temperature exceeds the target range, it establishes a correspondence between the material temperature deviation and the extension of the stirring time, and generates temperature compensation parameters; when the uniformity of steel fiber feeding is lower than the preset threshold, it establishes a correspondence between the uniformity deviation and the frequency adjustment of the variable frequency vibrating fiber feeder, and generates fiber compensation parameters; then, it stores the water compensation parameters, ash compensation parameters, temperature compensation parameters, and fiber compensation parameters in the mapping table of the PLC controller, forming a mapping relationship between the output adjustment of the compensation hardware and the deviation of the target process parameters, providing a basis for the PLC controller to automatically call the compensation hardware to perform dynamic compensation in the subsequent production process.

[0023] The production mode of ultra-high performance concrete is initialized, and a pre-production self-inspection is performed. The segmented mixing process is executed sequentially. The segmented mixing process includes a dry material premixing stage, an initial wet mixing stage, a fluidity closed-loop fine adjustment stage, a steel fiber feeding stage, a homogeneous fine mixing stage, and an interlocked discharge stage. In each stage, the PLC controller automatically controls the speed and mixing time of the mixing host according to the preset segmented process parameters, controls the feeding sequence and feeding method, and automatically calls the corresponding compensation hardware according to the real-time detected process parameters. The compensation parameters are adjusted according to the mapping relationship to maintain the process within the target range.

[0024] When initializing the production mode of ultra-high performance concrete, the PLC controller first retrieves the ultra-high performance concrete formula data, process parameter data, and quality control parameter data corresponding to the current production task, and loads the corresponding production mode configuration file. This configuration file includes at least the target dosage of each raw material, target rotation speed for each stage, target mixing time, target flowability range, target material temperature range, steel fiber feeding parameters, and compensation control parameters. After loading the production mode, the PLC controller performs a pre-production self-check, detecting the communication and operating status of the ultra-fine powder independent high-precision weighing hopper, admixture electromagnetic flowmeter pulse metering system, frequency conversion vibrating fiber feeder, material temperature sensor, flowability detection sensor, and mixing host. It verifies whether the zero-point data of each metering device and the sensor feedback signals are within the preset normal range, and confirms that each compensation hardware has completed parameter initialization according to the preset mapping relationship. When all self-check items pass, the PLC controller enters automatic production mode; otherwise, it outputs a fault alarm message and prohibits production from starting.

[0025] After entering the automatic production state, the PLC controller executes the dry material premixing stage, the initial wet mixing stage, the flowability closed-loop fine adjustment stage, the steel fiber feeding stage, the homogenization fine mixing stage, and the interlocking discharge stage in sequence according to the preset process sequence. In the dry material premixing stage, the PLC controller controls the sequential addition of quartz sand, cement, silica fume, and ultrafine fly ash microspheres to the mixing host according to a set sequence, and controls the mixing host to run at a preset low speed for a preset time to form a uniform dry mixture. After the dry material premixing is completed, the initial wet mixing stage begins. The PLC controller controls the addition of all anti-skinning admixtures and a preset proportion of mixing water to the mixing host, and controls the mixing host to switch to a preset medium-high speed to initially form the slurry. Subsequently, the fluidity closed-loop fine-tuning stage begins. The PLC controller adds the remaining mixing water in batches according to a preset time interval, while simultaneously collecting fluidity data from the fluidity detection sensor in real time and comparing the real-time fluidity with the target fluidity range. When the fluidity is lower than the target lower limit, the micro-water replenishment function is automatically invoked to perform compensation according to the mapping relationship. When the fluidity is higher than the target upper limit, the ash replenishment function is automatically invoked to perform compensation according to the mapping relationship. If the target range is still not reached after multiple consecutive compensations, an abnormal alarm message is generated and the current batch is marked.

[0026] After fluidity adjustment, the steel fiber feeding stage begins. The PLC controller reduces the mixing host to a preset low speed, while simultaneously starting the variable frequency vibrating fiber feeder to continuously and evenly feed steel fibers at a set frequency. The feeder's operating status and feeding duration are monitored in real time. After steel fiber feeding, the homogenization and fine mixing stage begins. The PLC controller controls the mixing host to operate at a preset medium speed and continuously collects data on the mixing host's load current, material temperature, and fluidity. When the load current fluctuation exceeds a preset threshold, the homogenization and fine mixing time is automatically extended to further evenly disperse the steel fibers and slurry. Throughout each production stage, the PLC controller collects process parameters such as fluidity, material temperature, mixing host load current, and water-cement ratio in real time at a preset scanning cycle. It compares these real-time parameters with the target range for the corresponding stage, calculating the deviation and direction. Based on the deviation results, it queries the compensation hardware mapping table to determine the corresponding compensation hardware and parameters. The output control signal drives the compensation hardware to perform compensation actions, thereby dynamically adjusting the process. Finally, in the interlocked discharge stage, the PLC controller performs a comprehensive check on the flowability, material temperature, equipment status, and compensation status. When all parameters meet the discharge conditions, the discharge gate is automatically opened to complete the discharge operation. If any condition is not met, discharge is prohibited and the interlock protection mechanism is triggered to ensure that the final product quality is within the target range.

[0027] Furthermore, the pre-production self-inspection includes:

[0028] Verify that the metering deviations of each powder, water, and admixture are within the preset allowable range; check whether the mixing host and vibrating feeder are in normal standby mode; verify that the signals of the material temperature sensor and flowability detection device are valid; confirm that all compensation hardware has completed parameter initialization according to the mapping relationship.

[0029] During pre-production self-inspection, the PLC controller first enters self-inspection mode and executes the self-inspection process sequentially, following the order of metering system check, equipment status check, sensor status check, and compensation hardware initialization check. During the metering system check, the PLC controller reads the current zero-point data of each powder weighing hopper, water metering device, and admixture metering device, and performs no-load zero calibration. It obtains feedback metering values ​​by sending detection commands to the metering devices, compares these values ​​with the corresponding reference zero-point values, and calculates the metering deviation. If the metering deviation does not exceed the preset allowable range, the metering device is considered normal; otherwise, a metering abnormality alarm is generated, and production is prohibited. During the equipment status check, the PLC controller reads the operating feedback signals from the mixing host, variable frequency vibrating fiber feeder, and related actuators. It detects whether the equipment has fault codes, emergency stop lockout status, communication abnormality status, or non-reset status, and verifies whether each device is in a standby condition that allows startup. When all devices return a normal standby signal, the equipment status check is considered passed; otherwise, the corresponding fault information is output, and the subsequent self-inspection process is terminated.

[0030] After completing the equipment status check, the PLC controller verifies the signal validity of the material temperature sensor and flowability detection device. Specifically, it continuously collects a preset number of detection data points and performs range judgment, fluctuation judgment, and communication integrity judgment on the collected data. When the detection data is within the effective measurement range of the sensor and there are no signal interruptions, abnormal jumps, or communication timeouts during continuous sampling, the corresponding detection device is determined to be working normally. If there is no signal output, data exceeds the range, data remains unchanged, or communication is abnormal, the corresponding detection device is determined to be faulty, and a sensor fault alarm is triggered. Subsequently, the PLC controller performs an initialization check on the ultrafine powder independent high-precision weighing hopper, admixture electromagnetic flowmeter pulse metering system, frequency conversion vibrating fiber feeder, and related compensation actuators. It reads the current parameter configuration values ​​of each compensation hardware and checks them against the initial parameters in the pre-stored mapping table to confirm that the device address, control mode, adjustment range, and initial compensation parameters of each compensation hardware are correctly loaded. If missing parameters, parameters exceeding limits, or mapping relationship loading failures are found, the initialization parameters are automatically reloaded, and verification is performed again. After all metering devices, execution equipment, detection devices, and compensation hardware have passed the self-test, the PLC controller generates a self-test pass flag, allowing entry into the ultra-high performance concrete automatic production process; if any self-test item fails, the system remains locked and the corresponding fault information is recorded until the fault is resolved and the pre-production self-test is re-executed.

[0031] Furthermore, the preset segmented process parameters include:

[0032] The dry material premixing stage involves sequentially adding quartz sand, cement, silica fume, and ultrafine fly ash microspheres, with the mixing host running at a relatively low speed for a first preset time. The initial wet mixing stage involves adding all the anti-skinning admixture and a preset proportion of mixing water, with the mixing host running at a medium-high speed for a second preset time. The fluidity closed-loop fine-tuning stage involves adding the remaining mixing water in two equal portions, with the mixing host running at a medium speed for a third preset time, real-time monitoring of fluidity, and adding a small amount of water if the fluidity falls below the target lower limit, and adding water if the fluidity exceeds the target higher limit. The upper limit is reached by adding a small amount of ash. If the limit is not met multiple times, an alarm will be triggered and material discharge will be prohibited. The steel fiber feeding stage is when the mixing host switches to the second lower speed and the variable frequency vibrating feeder is started to uniformly disperse and feed steel fibers, running for a fourth preset time. The homogenization and fine mixing stage is when the mixing host runs at the third medium speed for a fifth preset time. During this period, the load current of the mixing host is monitored. If the fluctuation exceeds the threshold, the fine mixing time is automatically extended. The interlocked discharge stage is when the material temperature, flowability, equipment status and compensation hardware all meet the conditions and the material is automatically discharged.

[0033] The PLC controller automatically calls the preset segmented process parameters according to the production mode corresponding to ultra-high performance concrete, and executes each mixing stage in sequence according to the process order.

[0034] During the dry material premixing stage, the PLC controller controls the corresponding metering and feeding devices to complete the feeding in the order of quartz sand, cement, silica fume, and ultrafine fly ash microspheres. After all the dry materials are fed in, the PLC controller controls the mixing host to run at the lowest speed for the first preset time to fully disperse and premix the powder raw materials and avoid local agglomeration during the subsequent water addition process. After the first preset time ends, the PLC controller automatically switches to the initial wet mixing stage, controls all the anti-skinning special admixture and the preset proportion of mixing water to be added to the mixing host at once, and at the same time switches the mixing host to the first medium-high speed for the second preset time to form a uniform slurry between the powder and liquid raw materials.

[0035] After the initial wet mixing, the flowability is fine-tuned in a closed-loop manner. The PLC controller adds the remaining mixing water twice in equal amounts to the mixing host at preset time intervals, and controls the mixing host to run at a second medium speed for a third preset duration. During this stage, the flowability detection device continuously outputs real-time flowability data, and the PLC controller collects the flowability detection results according to a preset sampling period and compares them with the target flowability range. When the real-time flowability is lower than the target lower limit, the PLC controller calculates the corresponding water replenishment amount based on the flowability deviation and controls the micro-water replenishment valve to open for the corresponding time to replenish water. When the real-time flowability is higher than the target upper limit, the PLC controller calculates the corresponding ash replenishment amount based on the flowability deviation and controls the ultrafine powder weighing hopper or micro-ash replenishment conveying mechanism to perform the ash replenishment operation. After each compensation, the flowability is re-detected. If the target range is still not reached after a preset number of consecutive compensations, the PLC controller generates a quality anomaly alarm, records the current batch's abnormal status, and sets a prohibited discharge indicator.

[0036] Once the fluidity reaches the target range, the PLC controller enters the steel fiber feeding stage, switching the mixing host to a second lower speed operation state to reduce the risk of agglomeration during steel fiber feeding. Simultaneously, the variable frequency vibrating fiber feeder is started to continuously and uniformly feed steel fibers at a preset feeding frequency. During steel fiber feeding, the PLC controller monitors the feeder's operating status and cumulative feeding amount in real time to ensure that the steel fibers are evenly dispersed and added to the slurry within a fourth preset time period. When the target feeding amount is reached, the PLC controller stops the feeder and automatically enters the homogenization and fine mixing stage.

[0037] During the homogenization and fine mixing stage, the PLC controller controls the mixing host to run at the third medium speed for the fifth preset time, further homogenizing the steel fibers and slurry. Simultaneously, the current detection module collects the load current of the mixing host in real time and calculates the load current fluctuation amplitude. When the load current fluctuation amplitude exceeds a preset threshold, it is determined that the current mixing uniformity has not yet met the requirements. The PLC controller automatically increases the fine mixing time by a preset extension step and continuously monitors the load current changes. When the load current fluctuation returns to the preset range, the homogenization and fine mixing process ends.

[0038] After homogenization and fine mixing, the system enters the interlocked discharge stage. The PLC controller reads feedback information from the material temperature sensor, flowability detection device, equipment status detection module, and compensation hardware status module to comprehensively judge whether the material temperature is within the target range, whether the flowability meets the discharge requirements, whether each device is in normal operation, and whether the compensation hardware has completed any compensation tasks. When all conditions are met, the PLC controller automatically releases the discharge interlock and opens the discharge gate to complete the discharge. If any condition is not met, the discharge interlock state is maintained, and corresponding alarm information is output until the abnormal state is resolved and the discharge conditions are re-verified.

[0039] Optionally, in the dry material premixing stage, the materials are added in the following order: quartz sand, cement, silica fume, and ultrafine fly ash microspheres. Then, the mixing host is controlled to run at a first low speed of 15-25 r / min for 30-60 seconds. In this embodiment, it is preferably run at 20 r / min for 45 seconds to fully disperse the powder raw materials and form a uniform dry mix. After the dry material premixing is completed, the initial wet mixing stage is entered. All the anti-skinning special admixture and 60%-80% of the total mixing water are added, preferably 70% of the mixing water. The mixing host is controlled to run at a first medium-high speed of 60-90 r / min for 60-120 seconds. In this embodiment, it is preferably run at 75 r / min for 90 seconds to initially form the slurry. After the initial wet mixing, the flowability is fine-tuned in a closed loop. The remaining mixing water is added in two equal portions, with an interval of 20–40 seconds, preferably 30 seconds. The mixing host runs at a second medium speed of 40–70 r / min for 60–120 seconds, preferably 50 r / min for 90 seconds in this embodiment. The PLC controller collects flowability data in real time at a sampling period of 1 second and controls the flowability within the range of 220–260 mm, preferably within the range of 240 ± 10 mm. When the real-time flowability is lower than the target lower limit, a small amount of water is added according to the rule of adding 0.1%–0.3% of the total mixing water for every 5 mm decrease. When the real-time flowability is higher than the target upper limit, a small amount of cementitious material is added according to the rule of adding 0.05%–0.2% of the total mass of cementitious material for every 5 mm increase. If the flowability still exceeds the target range after three consecutive compensations, a quality anomaly alarm is triggered and the discharge of the current batch is prohibited. After the fluidity reaches the target range, the steel fiber feeding stage begins. The mixing host is switched to a second lower speed of 10-20 r / min, preferably 15 r / min in this embodiment. Simultaneously, the variable frequency vibrating fiber feeder is started, continuously and uniformly feeding steel fibers at a feeding frequency of 15-30 Hz. The feeding time is controlled within the range of 60-180 s, preferably 120 s in this embodiment, to avoid steel fiber agglomeration and local accumulation. After the steel fiber feeding is completed, the homogenization and fine mixing stage begins. The PLC controller controls the mixing host to run at a third medium speed of 40-80 r / min for 90-180 s, preferably 60 r / min for 120 s in this embodiment. During the fine mixing process, the load current of the mixing host is collected in real time, and the fluctuation rate is calculated based on the average load current of the most recent 10 s. When the load current fluctuation rate exceeds ±10%, the mixing uniformity is determined to be insufficient, and the fine mixing time is automatically increased in extension steps of 30 s / time, with a cumulative extension time not exceeding 120 s. When the load current fluctuation rate remains within ±5% for 30 s consecutively, the mixing state is determined to meet the homogenization requirements.After homogenization and fine mixing are completed, the interlocked discharge stage begins. The PLC controller comprehensively verifies the material temperature, fluidity, equipment status, and compensation hardware status. The material temperature is controlled within the range of 15-35℃, the fluidity is controlled within the target range, there are no fault alarms in any equipment, and all compensation tasks have been completed. When all the above conditions are met, the discharge gate is automatically opened to complete the discharge; otherwise, the interlocked state is maintained and the corresponding alarm information is output.

[0040] Furthermore, the corresponding compensation hardware is automatically invoked based on the real-time detected process parameters, and the compensation parameters are adjusted according to the mapping relationship, including:

[0041] The PLC controller collects process parameters in real time according to a preset scanning cycle. These parameters include real-time flowability, real-time material temperature, mixer load current, and the current calculated water-cement ratio. The real-time process parameters are compared with the target range of the corresponding process stage to calculate the deviation and direction between each parameter and the target value. Based on the deviation and direction, a pre-stored compensation hardware mapping table is consulted to determine the type of compensation hardware to be called and the output adjustment amount. According to the compensation hardware type and output adjustment amount, the PLC controller outputs a control signal to the target compensation hardware. This control signal carries the output adjustment amount parameter. Upon receiving the control signal, the compensation hardware performs corresponding adjustments according to the adjustment amount parameter, including: opening the micro-water supply valve for a specified duration, running the micro-ash supply screw conveyor a specified number of times, or adjusting the frequency of the variable frequency vibrating feeder.

[0042] During concrete production, the PLC controller cyclically executes process parameter acquisition and compensation control tasks according to a preset scanning cycle, which is set to 100ms to 1000ms based on control accuracy requirements. The PLC controller acquires real-time flowability data through a flowability detection device, real-time material temperature data through a material temperature sensor, and real-time mixer load current data through a current detection module. It also calculates the current water-cement ratio in real-time based on the cumulative feed amount, cumulative water replenishment amount, and total mass of cementitious materials for the current batch, thus forming a process parameter set including real-time flowability, real-time material temperature, mixer load current, and the calculated water-cement ratio. Subsequently, the PLC controller calls the corresponding target parameter range according to the current process stage, compares the real-time process parameters with the target range, and calculates the deviation and direction of each process parameter relative to the target value. A real-time value lower than the target value is defined as a negative deviation, and a real-time value higher than the target value is defined as a positive deviation, and the corresponding deviation magnitude is recorded.

[0043] After obtaining the deviation results, the PLC controller accesses the compensation hardware mapping table pre-stored in the internal memory or the host computer database. It performs a search and matching based on the current process stage, process parameter type, deviation direction, and deviation range to determine the corresponding compensation hardware type and output adjustment amount. Specifically, when the fluidity is below the lower limit of the target range, a micro-water replenishment compensation strategy is invoked, determining the opening duration of the micro-water replenishment valve based on the fluidity deviation. When the fluidity is above the upper limit of the target range, an ash replenishment compensation strategy is invoked, determining the ash replenishment amount and number of rotations of the micro-ash replenishment screw conveyor based on the fluidity deviation. When the steel fiber dispersion is insufficient or the load current fluctuation of the mixing host exceeds a preset threshold, a fiber feeding compensation strategy is invoked, determining the frequency adjustment amount and feeding duration of the variable frequency vibrating feeder based on the degree of deviation. When the material temperature deviates from the target range, a material temperature compensation strategy is invoked, adjusting the subsequent mixing time or pausing subsequent feeding until the material temperature returns to the target range based on the degree of temperature deviation.

[0044] After determining the compensation hardware and output adjustment amount, the PLC controller generates corresponding control signals and sends them to the target compensation hardware via digital output module, analog output module, or communication bus. The control signals must include at least the device address, compensation type, output adjustment amount, and execution duration parameters. Upon receiving the control signals, the compensation hardware executes the corresponding compensation actions. Specifically, the micro-water supply valve controls water supply for a specified opening duration, the micro-ash supply screw conveyor delivers the compensation powder according to a specified number of revolutions, and the variable frequency vibrating feeder adjusts the feeding speed according to a specified frequency. After the compensation action is completed, the PLC controller continues to collect updated process parameters according to the next scan cycle and performs deviation calculation and compensation decision again. When the updated process parameters enter the target range of the corresponding process stage, the current compensation action stops and normal production control is maintained. When the process parameters still exceed the target range, the next round of compensation control is executed, thus forming a closed-loop compensation control mechanism based on real-time detection, deviation analysis, compensation decision, and feedback verification, ensuring that the ultra-high performance concrete production process remains within the target process range.

[0045] The compensation hardware mapping table can be established in advance through production calibration tests. Some examples of the mapping relationships are as follows:

[0046] For example, when the real-time flowability is lower than the lower limit of the target flowability range, the micro-water supply valve is invoked to perform compensation based on the flowability deviation. Specifically: when the flowability deviation is -10mm to -20mm, the micro-water supply valve is opened for 2 seconds; when the flowability deviation is -20mm to -30mm, the micro-water supply valve is opened for 5 seconds; when the flowability deviation is greater than -30mm, the micro-water supply valve is opened for 8 seconds, and an abnormal flowability warning message is generated.

[0047] For example, when the real-time flowability is higher than the upper limit of the target flowability range, a micro-feeding screw conveyor is invoked to perform compensation based on the flowability deviation. Specifically: when the flowability deviation is +10mm to +20mm, the micro-feeding screw conveyor runs 5 revolutions; when the flowability deviation is +20mm to +30mm, the micro-feeding screw conveyor runs 10 revolutions; and when the flowability deviation is greater than +30mm, the micro-feeding screw conveyor runs 15 revolutions, and a quality warning message is generated.

[0048] For example, when the load current of the mixing host fluctuates beyond the target range, a fine mixing time compensation strategy is invoked according to the current fluctuation rate, wherein: when the current fluctuation rate is 10% to 15%, the homogenization fine mixing time is extended by 30s; when the current fluctuation rate is 15% to 20%, the homogenization fine mixing time is extended by 60s; when the current fluctuation rate exceeds 20%, the homogenization fine mixing time is extended by 90s, and the speed of the mixing host is reduced by 5%.

[0049] For example, when the uniformity of steel fiber dispersion deviates from the target range, the variable frequency vibrating feeder is called to perform compensation according to the amount of uniformity deviation. Specifically: when the uniformity deviation is 5% to 10%, the frequency of the variable frequency vibrating feeder is increased by 2Hz; when the uniformity deviation is 10% to 15%, the frequency of the variable frequency vibrating feeder is increased by 5Hz; when the uniformity deviation exceeds 15%, the frequency of the variable frequency vibrating feeder is increased by 8Hz, and the steel fiber feeding time is extended by 20s.

[0050] For example, when the real-time material temperature exceeds the target material temperature range, a temperature compensation strategy is invoked based on the material temperature deviation, wherein: when the material temperature deviation is 2℃ to 4℃, the low-speed stirring time is extended by 20s; when the material temperature deviation is 4℃ to 6℃, subsequent material feeding is suspended for 30s; when the material temperature deviation exceeds 6℃, production is suspended and an over-temperature alarm is triggered.

[0051] Preferably, when the PLC controller detects multiple process parameters deviating from their corresponding target ranges simultaneously within the same scan cycle, it executes compensation decisions based on preset compensation priorities. Flowability deviation has the highest priority, followed by water-cement ratio deviation, then material temperature deviation, and finally, the load current deviation of the mixing host has the lowest priority. The PLC controller prioritizes compensation calculations for high-priority process parameters and re-acquires the process parameters after compensation is completed. If deviations in low-priority parameters still exist, the corresponding compensation operation continues. When multiple deviations correspond to the same compensation hardware, the multiple compensation values ​​are merged and calculated to generate a unified output adjustment value, avoiding repeated actions of the same compensation hardware within a short period.

[0052] Furthermore, it also includes:

[0053] During the interlocked material discharge stage, when all discharge conditions are met, the discharge gate is automatically opened to complete the discharge; when the discharge conditions are not met, the fault interlock protection mechanism is triggered and the discharge is suspended. In addition, after each production batch is completed, production process data is automatically collected and stored to build a traceable production ledger.

[0054] After completing the homogenization and fine mixing stage, the PLC controller enters the interlocked discharge stage and initiates the comprehensive discharge condition judgment program. The PLC controller first reads real-time data from the flowability detection device, material temperature sensor, mixing host status detection module, compensation hardware status module, and fault monitoring module, verifying each discharge condition item by item. Specifically, the flowability detection value should be within the preset target flowability range, the material temperature should be within the preset allowable temperature range, the mixing host should be in normal operating condition without fault alarm information, each compensation hardware should have completed the current batch compensation task and there should be no unexecuted compensation instructions, and the system should not have interlocked faults such as over-temperature, metering abnormalities, communication abnormalities, or emergency stops. When all discharge conditions are met, the PLC controller generates a discharge permission signal, controlling the discharge gate actuator to automatically open the discharge gate and complete material discharge according to the preset discharge time. During the discharge process, the discharge gate status feedback signal is continuously monitored; when a discharge completion signal is detected, the discharge gate is automatically closed, ending the current production batch.

[0055] If any discharge condition is not met, the PLC controller immediately prevents the discharge door from opening and triggers the fault interlock protection mechanism, suspending the current discharge operation. Simultaneously, it records the fault type, occurrence time, and corresponding detection parameter values, and outputs alarm information through the human-machine interface. For faults that can be automatically recovered, the PLC controller continuously monitors the fault status according to a preset recovery strategy, and re-executes the discharge condition verification after the fault is cleared. For faults that cannot be automatically recovered, the interlock remains locked, awaiting manual intervention and reconfirmation before the interlock can be released.

[0056] After the current batch is discharged, the PLC controller automatically performs a production data archiving operation, collecting and storing key process data from the production process of this batch. This key process data includes at least the production batch number, production time, actual raw material input quantity, mixing speed at each stage, mixing duration at each stage, flowability test results, material temperature test results, mixer load current variation data, water-cement ratio variation data, compensation hardware call records, compensation parameter adjustment records, fault alarm records, and the final discharge result. The PLC controller associates and organizes this key process data by batch, generating production record files for the corresponding production batches and storing them in a local database or a host computer management system. Simultaneously, it establishes an index relationship between batch numbers and production record files, forming a traceable production ledger. When subsequent quality traceability is required, the complete production process data for the corresponding batch can be retrieved based on the production batch number, achieving information tracking and quality traceability management throughout the entire ultra-high performance concrete production process.

[0057] Furthermore, the fault interlocking protection mechanism includes:

[0058] Real-time monitoring of over-temperature faults and production suspension; shutdown alarm when monitoring single-stage process timeouts exceeding allowable deviations; automatic rejection of the current batch when monitoring measurement deviations exceeding allowable accuracy; and execution of all output resets and system emergency stop lockout in response to emergency stop signals.

[0059] The fault interlock protection mechanism is executed in real time by the PLC controller throughout the entire production process, and performs interlock protection control according to over-temperature fault monitoring, process timeout monitoring, metering anomaly monitoring, and emergency shutdown monitoring. During over-temperature fault monitoring, the PLC controller continuously collects real-time material temperature data fed back by the material temperature sensor according to a preset scanning cycle, and compares the real-time material temperature with the preset maximum allowable material temperature; when the real-time material temperature exceeds the preset maximum allowable material temperature, the PLC controller immediately triggers the over-temperature interlock protection, suspends the current production process, stops subsequent raw material feeding operations, maintains the mixing host at low speed or stops running, and outputs over-temperature alarm information; at the same time, it records the time of over-temperature occurrence, the duration of over-temperature, and the corresponding material temperature value, and the production process can only be resumed after the material temperature returns to a safe range.

[0060] During the process timeout monitoring, the PLC controller establishes corresponding process timers for the dry material premixing stage, the initial wet mixing stage, the flowability closed-loop fine adjustment stage, the steel fiber feeding stage, and the homogenization fine mixing stage. When the actual running time of any process stage exceeds the corresponding preset process duration and exceeds the allowable deviation range, a process timeout fault is determined to have occurred. The PLC controller immediately stops the operation of the current stage, shuts down the relevant actuators, and triggers a shutdown alarm. At the same time, it records the timeout stage name, planned duration, actual running time, and timeout amount information to prevent product quality degradation due to equipment abnormalities or process malfunctions.

[0061] During the monitoring of metering anomalies, the PLC controller continuously reads the real-time metering data from each powder weighing device, water metering device, and admixture metering device, and compares the actual metering results with the target feed amount to calculate the metering deviation. When the metering deviation exceeds the preset allowable accuracy range, a metering anomaly is determined to have occurred. The PLC controller automatically marks the current production batch as a non-conforming batch and performs batch rejection processing. At the same time, the batch is prohibited from entering the normal discharge process, and the abnormal material type, target metering value, actual metering value, and deviation information are recorded to prevent concrete that does not meet the process requirements from entering the subsequent use stage.

[0062] During emergency stop monitoring, the PLC controller monitors the status of the emergency stop button, the host computer's emergency stop command, and the safety protection circuit in real time. When any emergency stop signal is received, the system's emergency stop program is immediately executed, resetting all digital outputs, analog outputs, and communication control outputs. The feeding device, compensation hardware, discharge actuator, and mixing host drive system are shut down, and the system status is switched to emergency stop locked state. In the emergency stop locked state, all automatic production functions are prohibited from starting until the cause of the fault is confirmed by manual verification and a reset and unlocking operation is performed. Only then can the PLC controller restore the system's operating permissions, thereby ensuring the safety of equipment operation and the safety of the production process.

[0063] In summary, the embodiments of this application have at least the following technical effects:

[0064] This paper analyzes the performance of a concrete mixing plant based on the production process of ultra-high performance concrete (UHVPC), deploys compensation hardware, and establishes a mapping relationship between the compensation hardware and compensation parameters. The UHVPC production mode is initialized, pre-production self-inspection is performed, and a segmented mixing process is executed sequentially. This segmented mixing process includes a dry premixing stage, an initial wet mixing stage, a fluidity closed-loop fine-tuning stage, a steel fiber feeding stage, a homogenized fine mixing stage, and an interlocked discharge stage. At each stage, the PLC controller automatically controls the speed and mixing time of the mixing host according to preset segmented process parameters, controls the feeding sequence and method, and automatically calls the corresponding compensation hardware based on real-time detected process parameters, adjusting the compensation parameters according to the mapping relationship to maintain the process within the target range. This solves the technical problem of poor product quality consistency caused by fluctuations in raw materials, changes in equipment status, and process disturbances in the production process of UHVPC, achieving the technical effect of improving product quality stability and consistency.

[0065] Example 2, based on the same inventive concept as the PLC automatic control method for concrete mixing plants in the previous examples, such as... Figure 2 As shown, this application provides a PLC automatic control system for a concrete mixing plant, wherein the system includes:

[0066] Analysis Module 11: Based on the production process of ultra-high performance concrete, the performance of the concrete mixing plant is analyzed, compensation hardware is deployed, and a mapping relationship between the compensation hardware and compensation parameters is established. Compensation Control Module 12: Initializes the production mode of ultra-high performance concrete, performs pre-production self-inspection, and sequentially executes the segmented mixing process. The segmented mixing process includes a dry material premixing stage, an initial wet mixing stage, a fluidity closed-loop fine adjustment stage, a steel fiber feeding stage, a homogeneous fine mixing stage, and an interlocked discharge stage. In each stage, the PLC controller automatically controls the speed and mixing time of the mixing host according to the preset segmented process parameters, controls the feeding sequence and feeding method, and automatically calls the corresponding compensation hardware according to the real-time detected process parameters, adjusts the compensation parameters according to the mapping relationship, and maintains the process within the target range.

[0067] Furthermore, the compensation control module 12 is used to perform the following method:

[0068] During the interlocked material discharge stage, when all discharge conditions are met, the discharge gate is automatically opened to complete the discharge; when the discharge conditions are not met, the fault interlock protection mechanism is triggered and the discharge is suspended. In addition, after each production batch is completed, production process data is automatically collected and stored to build a traceable production ledger.

[0069] Furthermore, the parsing module 11 is used to perform the following methods:

[0070] This study analyzes the performance deficiencies of ordinary mixing plants in various dimensions, including metering accuracy, mixing and shearing capacity, fiber feeding uniformity, and environmental adaptability. Based on these performance deficiencies, corresponding compensation hardware is deployed. This compensation hardware includes: an independent high-precision weighing hopper for ultrafine powders, an electromagnetic flowmeter pulse metering system for admixtures, a variable frequency vibrating fiber feeder, and real-time sensors for material temperature and flowability. Based on the correspondence between the compensation hardware and the performance deficiencies, a mapping relationship between the compensation hardware and compensation parameters is established. This mapping relationship includes a functional correspondence between the output adjustment of each compensation hardware and the deviation of the target process parameters.

[0071] Furthermore, the compensation control module 12 is used to perform the following method:

[0072] Verify that the metering deviations of each powder, water, and admixture are within the preset allowable range; check whether the mixing host and vibrating feeder are in normal standby mode; verify that the signals of the material temperature sensor and flowability detection device are valid; confirm that all compensation hardware has completed parameter initialization according to the mapping relationship.

[0073] Furthermore, the compensation control module 12 is used to perform the following method:

[0074] The dry material premixing stage involves sequentially adding quartz sand, cement, silica fume, and ultrafine fly ash microspheres, with the mixing host running at a relatively low speed for a first preset time. The initial wet mixing stage involves adding all the anti-skinning admixture and a preset proportion of mixing water, with the mixing host running at a medium-high speed for a second preset time. The fluidity closed-loop fine-tuning stage involves adding the remaining mixing water in two equal portions, with the mixing host running at a medium speed for a third preset time, real-time monitoring of fluidity, and adding a small amount of water if the fluidity falls below the target lower limit, and adding water if the fluidity exceeds the target higher limit. The upper limit is reached by adding a small amount of ash. If the limit is not met multiple times, an alarm will be triggered and material discharge will be prohibited. The steel fiber feeding stage is when the mixing host switches to the second lower speed and the variable frequency vibrating feeder is started to uniformly disperse and feed steel fibers, running for a fourth preset time. The homogenization and fine mixing stage is when the mixing host runs at the third medium speed for a fifth preset time. During this period, the load current of the mixing host is monitored. If the fluctuation exceeds the threshold, the fine mixing time is automatically extended. The interlocked discharge stage is when the material temperature, flowability, equipment status and compensation hardware all meet the conditions and the material is automatically discharged.

[0075] Furthermore, the compensation control module 12 is used to perform the following method:

[0076] Real-time monitoring of over-temperature faults and production suspension; shutdown alarm when monitoring single-stage process timeouts exceeding allowable deviations; automatic rejection of the current batch when monitoring measurement deviations exceeding allowable accuracy; and execution of all output resets and system emergency stop lockout in response to emergency stop signals.

[0077] Furthermore, the compensation control module 12 is used to perform the following method:

[0078] The PLC controller collects process parameters in real time according to a preset scanning cycle. These parameters include real-time flowability, real-time material temperature, mixer load current, and the current calculated water-cement ratio. The real-time process parameters are compared with the target range of the corresponding process stage to calculate the deviation and direction between each parameter and the target value. Based on the deviation and direction, a pre-stored compensation hardware mapping table is consulted to determine the type of compensation hardware to be called and the output adjustment amount. According to the compensation hardware type and output adjustment amount, the PLC controller outputs a control signal to the target compensation hardware. This control signal carries the output adjustment amount parameter. Upon receiving the control signal, the compensation hardware performs corresponding adjustments according to the adjustment amount parameter, including: opening the micro-water supply valve for a specified duration, running the micro-ash supply screw conveyor a specified number of times, or adjusting the frequency of the variable frequency vibrating feeder.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A PLC automatic control method for concrete mixing plants, characterized in that, The method includes: Based on the production process of ultra-high performance concrete, the performance of concrete mixing plants is analyzed, compensation hardware is deployed, and a mapping relationship between the compensation hardware and compensation parameters is established. The production mode of ultra-high performance concrete is initialized, and a pre-production self-inspection is performed. The segmented mixing process is executed sequentially. The segmented mixing process includes a dry material premixing stage, an initial wet mixing stage, a fluidity closed-loop fine adjustment stage, a steel fiber feeding stage, a homogeneous fine mixing stage, and an interlocked discharge stage. In each stage, the PLC controller automatically controls the speed and mixing time of the mixing host according to the preset segmented process parameters, controls the feeding sequence and feeding method, and automatically calls the corresponding compensation hardware according to the real-time detected process parameters. The compensation parameters are adjusted according to the mapping relationship to maintain the process within the target range.

2. The PLC automatic control method for concrete mixing plants according to claim 1, characterized in that, Also includes: During the interlocked discharge phase, when all discharge conditions are met, the discharge gate is automatically opened to complete the discharge. When the discharge conditions are not met, the fault interlock protection mechanism is triggered and the discharge is suspended. Each time a production batch is completed, production process data is automatically collected and stored to build a traceable production ledger.

3. The PLC automatic control method for concrete mixing plants according to claim 1, characterized in that, Performance analysis of concrete batching plants based on the production process of ultra-high performance concrete, including: Analysis of the performance deficiencies of ordinary mixing plants in terms of metering accuracy, mixing and shearing capacity, fiber feeding uniformity, and environmental adaptability. Based on the performance deficiencies in various dimensions, corresponding compensation hardware is deployed. The compensation hardware includes: an independent high-precision weighing hopper for ultrafine powders, an electromagnetic flowmeter pulse metering system for admixtures, a frequency-converting vibrating fiber feeder, and a real-time sensor for material temperature and flowability. Based on the correspondence between the compensation hardware and the performance deficiency characteristics, a mapping relationship between the compensation hardware and the compensation parameters is established, wherein the mapping relationship includes the functional correspondence between the output adjustment amount of each compensation hardware and the deviation of the target process parameter.

4. The PLC automatic control method for concrete mixing plants according to claim 1, characterized in that, The pre-production self-inspection includes: Verify whether the metering deviations of each powder, water, and additive are within the preset allowable range; Check whether the mixing host and vibrating feeder are in normal standby mode; Verify the validity of the signals from the material temperature sensor and the flowability detection device; Confirm that all compensation hardware has completed parameter initialization according to the mapping relationship.

5. The PLC automatic control method for concrete mixing plants according to claim 1, characterized in that, The preset segmented process parameters include: The dry material premixing stage involves feeding the materials in the following order: quartz sand, cement, silica fume, and ultrafine fly ash microspheres. The mixing host operates at a first low speed for a first preset time. The initial wet mixing stage involves adding all the anti-skinning special additives and a preset proportion of mixing water, with the mixing host running at a first medium-high speed for a second preset time. The fluidity closed-loop fine-tuning stage involves adding the remaining mixing water in two equal amounts, with the mixing host running at a second medium speed for a third preset time, and real-time monitoring of fluidity. If the fluidity is lower than the target lower limit, a small amount of water is added; if the fluidity is higher than the target upper limit, a small amount of ash is added. If the fluidity fails to meet the target multiple times, an alarm is triggered and material discharge is prohibited. The steel fiber feeding stage involves switching the mixing host to a second lower speed and simultaneously starting the variable frequency vibrating feeder to uniformly disperse and feed the steel fibers, running for a fourth preset time. The homogenization and fine mixing stage is when the mixing host runs at the third medium speed for the fifth preset time. During this period, the load current of the mixing host is monitored, and the fine mixing time is automatically extended when the fluctuation exceeds the threshold. The interlocked discharge stage involves automatic discharge after the material temperature, flowability, equipment status, and compensation hardware all meet the required conditions.

6. The PLC automatic control method for concrete mixing plants according to claim 2, characterized in that, The fault interlock protection mechanism includes: Real-time monitoring of over-temperature faults and production suspension; shutdown alarm when monitoring single-stage process timeouts exceeding allowable deviations; automatic rejection of the current batch when monitoring measurement deviations exceeding allowable accuracy; and execution of all output resets and system emergency stop lockout in response to emergency stop signals.

7. The PLC automatic control method for concrete mixing plants according to claim 1, characterized in that, The corresponding compensation hardware is automatically invoked based on the real-time detected process parameters, and the compensation parameters are adjusted according to the mapping relationship, including: The PLC controller collects process parameters in real time at a preset scanning cycle. The process parameters include real-time flowability, real-time material temperature, load current of the mixing host, and the current calculated water-cement ratio. Compare the real-time process parameters with the target range of the corresponding process stage, and calculate the deviation and direction of each parameter from the target value. Based on the deviation amount and deviation direction, query the pre-stored compensation hardware mapping table to determine the type of compensation hardware to be called and the output adjustment amount. According to the type of compensation hardware and the output adjustment amount, the PLC controller outputs a control signal to the target compensation hardware. The control signal carries the output adjustment amount parameter. After receiving the control signal, the compensation hardware performs corresponding regulation according to the adjustment amount parameter, including: opening the micro water supply valve for a specified duration, running the micro ash supply screw conveyor a specified number of times, or adjusting the frequency of the frequency conversion vibrating feeder.

8. A PLC automatic control system for concrete mixing plants, characterized in that, The system is used to implement the PLC automatic control method for concrete mixing plants according to any one of claims 1-7, the system comprising: Analysis module: Based on the production process of ultra-high performance concrete, the performance of concrete mixing plant is analyzed, compensation hardware is deployed, and the mapping relationship between compensation hardware and compensation parameters is established; The compensation control module initializes the production mode of ultra-high performance concrete, performs pre-production self-inspection, and sequentially executes the segmented mixing process. The segmented mixing process includes a dry material premixing stage, an initial wet mixing stage, a fluidity closed-loop fine adjustment stage, a steel fiber feeding stage, a homogeneous fine mixing stage, and an interlocked discharge stage. In each stage, the PLC controller automatically controls the speed and mixing time of the mixing host according to the preset segmented process parameters, controls the feeding sequence and feeding method, and automatically calls the corresponding compensation hardware according to the real-time detected process parameters, adjusts the compensation parameters according to the mapping relationship, and maintains the process within the target range.

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