A grinding roller speed PID closed-loop control method

Abstract

The application discloses a kind of grinding roller speed PID closed-loop control method, the method includes: the angular position of upstream and downstream grinding roller, actual speed and driving motor output torque are synchronously collected, angular position is divided interval and equivalent load is calculated;Equivalent load of multiple rotation periods is angular position alignment and robust statistics, constructs roller cycle load template, obtains material load residual error with the difference between current equivalent load and same angular position cycle load reference value, and the application relates to industrial grinding equipment motion control technical field.A kind of grinding roller speed PID closed-loop control method, according to grinding roller angular position, angular domain resampling is carried out to operating data, and based on equivalent load of multiple rotation periods, roller cycle load template can be constructed, periodic mechanical load formed by grinding roller eccentricity, local wear of roll surface, bearing periodic resistance and transmission error can be identified, and invalid repeated adjustment generated by PID controller to fixed periodic disturbance is reduced.

Description

Technical Field

[0001] This invention relates to the field of motion control of industrial grinding equipment, and more specifically, to a PID closed-loop control method for the rotational speed of grinding rollers. Background Technology

[0002] Under the influence of eccentricity, localized wear on the roller surface, transmission clearance, and changes in material distribution, the driving load of the grinding roller simultaneously includes a periodic mechanical component synchronized with the angular position and a non-periodic component that changes with material transport. Patent CN117064239A discloses a grinding device and its motor control method, which implements PID constant speed control by monitoring the real-time motor speed and current, and uses reversal and acceleration to relieve stalling. However, this scheme is a feedback processing after the speed decreases and does not separate the roller cyclic load from the material load. Patent CN116747961A performs PID adjustment based on grinding process parameters, real-time spindle speed, and flow information, mainly targeting single-machine steady-state process control. Patent CN113198591B uses rolling time-domain estimation to achieve predictive control of the main current, differential pressure, and feed rate of the vertical roller mill, but it does not involve constructing a periodic load template based on the roller angular position, nor does it pre-set the downstream PID state based on the upstream load propagation process. Therefore, existing technologies still struggle to complete targeted compensation before the material load arrives and smoothly cancel out mismatch predictions. It is necessary to propose a PID closed-loop control method for grinding roller speed based on angular domain load separation, load package propagation prediction, and arrival verification. Summary of the Invention

[0003] The purpose of this invention is to provide a PID closed-loop control method for the rotational speed of a grinding roller, which solves the problems of existing grinding equipment that make it difficult to distinguish between the cyclic mechanical load of the roller and the transient load of the material, the downstream grinding roller can only be adjusted after the load reaches and a speed deviation occurs, and the easy generation of integral residue and torque mutation when predicting and compensating for mismatch.

[0004] This invention achieves the above objective through the following technical solution: a PID closed-loop control method for the rotational speed of a grinding roller, applied to an upstream grinding roller and a downstream grinding roller arranged sequentially along the material conveying direction, the method comprising: The angular position, actual speed and output torque of the corresponding drive motor of each grinding roller are collected synchronously. A single rotation cycle is divided into multiple angular domain intervals, and the actual speed and output torque are mapped to the corresponding angular domain intervals. Based on the output torque, grinding roller angular acceleration, transmission system equivalent inertia, and no-load torque, the equivalent load of each angular domain interval is determined; the equivalent load of continuous rotation cycles is aligned by angular position, and the historical equivalent load within the same angular domain interval is robustly statistically analyzed to form a roller circumferential load template, and the roller circumferential load template is stopped from being updated under abnormal load conditions. Subtract the periodic load reference value at the same angular position in the roller circumferential periodic load template from the current equivalent load to obtain the material load residual, and generate the angular position synchronous feedforward compensation amount based on the periodic load reference value. When the material load residual of the upstream grinding roller meets the load pack start condition, a material load pack is established and the start time, duration, peak load, load change slope and load energy are extracted. Based on the material conveying distance between the upstream and downstream grinding rollers, the material conveying speed, and the time shift relationship of the historical upstream and downstream material load residuals, the predicted arrival time and predicted load intensity of the material load package are determined. Before the predicted arrival time, the integral state, torque preset amount and torque change slope of the downstream PID controller are preset according to the predicted load intensity, the equivalent inertia of the downstream grinding roller and the remaining torque margin of the downstream drive motor. An arrival verification window is established before and after the predicted arrival time, and the material load package is verified based on the material load residual of the downstream grinding roller. When the verification is successful, the downstream PID controller is smoothly switched from the preset state to the speed error closed-loop adjustment state, and the material propagation parameters are updated. If the verification fails, the preset is canceled according to the limited release slope, and the original closed-loop control state of the downstream PID controller is restored.

[0005] Furthermore, the synchronous acquisition and mapping includes: An angular position pulse and a reference pulse per revolution are obtained by an angular position detector installed at the end of the grinding roller shaft or the end of the drive motor shaft, and the angular position zero point of the rotation cycle is determined by the reference pulse per revolution. Based on the angular position pulse, the actual rotational speed and output torque are resampled in the angular domain so that the data of the same angular position in different rotation cycles are mapped to the same angular domain interval; The data timestamps are corrected based on the sampling delay and communication delay of the angular position detector, speed detector, and torque acquisition channel to ensure that all operating data adopt a unified time reference.

[0006] Furthermore, the determination of the equivalent load includes: Calculate the motor output torque based on the drive motor current and motor torque coefficient, or read the estimated torque value output by the driver; Based on the transmission ratio and transmission efficiency, the motor output torque is converted to the grinding roller shaft side to obtain the roller shaft side drive torque; The angular acceleration is determined based on the actual rotational speed at adjacent sampling times, and the inertial torque corresponding to the equivalent inertia of the transmission system is calculated. The equivalent load is obtained by subtracting the inertial torque and the no-load torque corresponding to the current speed from the drive torque on the roller shaft side. The no-load torque is determined by establishing the correspondence between speed and no-load torque based on the stable torque of the grinding roller when it is running at at least 3 calibrated speeds without material.

[0007] Furthermore, the formation of the roller cycle load template includes: The continuous rotation period in which the actual speed deviation does not exceed the target speed limit, the drive motor output torque does not reach the torque limit, and the material load residual does not meet the load pack start condition is selected as the template sample period. For each corner domain interval, calculate the median or truncated mean of the historical equivalent load within the template sample period, and use the calculation result as the reference value of the periodic load for that corner domain interval. The roller circumferential load template is formed by combining the reference values ​​of each periodic load according to the angular position sequence of the angular domain interval. When the material load residual exceeds the load pack starting threshold, the actual speed drop exceeds the target speed limit, or the drive motor output torque reaches the torque limit, the update of the roller cycle load template is stopped until the continuous rotation cycle meets the template sample cycle conditions again.

[0008] Furthermore, the generation of the material load residual and angular position synchronous feedforward compensation includes: Query the periodic load reference value in the roller circumferential periodic load template based on the current angular position; When the current angle position is located between adjacent angle domain intervals, linear interpolation is performed based on the angular distance between the current angle position and the center position of the adjacent angle domain interval. Calculate the difference between the current equivalent load and the interpolated periodic load reference value to obtain the material load residual; The angular position synchronous feedforward compensation amount is generated based on the periodic load reference value and the torque transmission coefficient of the drive motor, and the amplitude and slope of the feedforward compensation amount are limited. The angular position synchronization feedforward compensation amount is added to the feedback control amount generated by the PID controller based on the target speed and the actual speed to form the target torque command for the drive motor.

[0009] Furthermore, the establishment of the material load package includes: The median value and median absolute deviation of the residuals are calculated based on the historical material load residuals under normal operating conditions. The sum of the median value of the residuals and the median absolute deviation of the specified multiple is used as the load pack starting threshold. When the material load residual of the upstream grinding roller exceeds the load pack start threshold and its rate of increase exceeds the limit quantile of the historical normal change rate, and continues to reach the start confirmation time, the material load pack is determined to start. When the material load residual is lower than the load pack end threshold and continues to reach the end confirmation time, the material load pack is determined to end. The load pack end threshold is less than the load pack start threshold. The peak load and the maximum load change slope are determined within the start and end interval of the material load package, and the load energy is obtained by time integration of the material load residual.

[0010] Furthermore, the determination of the predicted arrival time and predicted load intensity includes: The ratio of the material conveying distance to the current material conveying speed is used as the basic propagation time; Candidate time shifts are applied to the historical downstream material load residuals and correlation coefficients are calculated. The difference between the candidate time shift corresponding to the maximum correlation coefficient and the basic propagation duration is used as the propagation correction amount. The sum of the start time of the upstream material load package, the basic propagation time, and the propagation correction is used as the predicted arrival time. Based on the historical matching load packages within the pre-defined speed range belonging to the same material category and the current material conveying speed, the ratio of downstream peak load to upstream peak load and the ratio of downstream load energy to upstream load energy are calculated respectively. The current material load package is then corrected using the median value of the two ratios to obtain the predicted peak load and predicted load energy. The predicted load intensity includes the predicted peak load and predicted load energy.

[0011] Furthermore, the presets of the downstream PID controller include: The predicted compensation torque required to maintain the target speed is determined based on the predicted peak load; the initial torque margin is determined based on the difference between the maximum allowable torque of the drive motor and the current output torque, and the safety reserve torque is subtracted from the initial torque margin to obtain the remaining torque margin; When the predicted compensation torque is not greater than the remaining torque margin, the predicted compensation torque is converted into an integral preset amount and a torque preset amount, and the load is applied in a continuously increasing ramp before the predicted arrival time. The slope of the torque preset amount is limited based on the smaller of the maximum load change slope of the material load pack and the allowable torque change rate of the drive motor. The integral preset value is limited to the usable torque range after deducting the proportional control component, the derivative control component, and the angular position synchronous feedforward compensation from the maximum allowable torque of the drive motor.

[0012] Furthermore, when the predicted compensation torque is greater than the remaining torque margin: Obtain the remaining torque margin of the drive motor corresponding to the grinding roller adjacent to the downstream grinding roller; Based on the proportion of the remaining torque margin of each drive motor to the total available remaining torque margin, the speed compensation is distributed between the downstream grinding roller and adjacent grinding rollers. The rotational speed compensation is converted into the roller surface linear velocity compensation based on the effective radius of each grinding roller, and the deviation of the roller surface linear velocity ratio of adjacent grinding rollers after compensation relative to the normal operating setting value is limited. When any drive motor reaches its maximum allowable torque, the increase in the speed compensation of that drive motor stops, and the unallocated speed compensation is transferred to the adjacent drive motor that still has residual torque margin. When the sum of the remaining torque margins of all drive motors is less than the predicted compensation torque, the material supply speed of the feeding mechanism is reduced.

[0013] Furthermore, the arrival verification and material propagation parameter update includes: Extract the actual start time, actual peak load, actual load energy and changing trend of the downstream material load residual within the verification window; Calculate the time deviation between the actual start time and the predicted arrival time, the relative deviation between the actual peak load and the predicted peak load, the relative deviation between the actual load energy and the predicted load energy, and the correlation coefficient of the upstream and downstream material load residuals after time shift alignment. When the time deviation, the two relative deviations, and the correlation coefficient are all within the acceptable range determined based on the historical matching load pack, the verification is deemed successful. Within the limited transition time, the integral preset amount and the torque preset amount are gradually reduced, and the feedback control component based on the actual speed error is gradually increased. The propagation correction is adjusted based on the actual arrival time, and the load intensity ratio is adjusted based on the actual peak load and the actual load energy. If no downstream material load residual that meets the acceptance range is detected, the verification is deemed to have failed, and the integral preset, torque preset, and speed compensation are cancelled according to the release slope that does not exceed the loading slope.

[0014] The beneficial effects of this invention are as follows: 1. This invention performs angular domain resampling of operating data according to the angular position of the grinding roller, and constructs a roller circumferential load template based on the equivalent load of multiple rotation cycles. It can identify the cyclic mechanical load formed by grinding roller eccentricity, local wear on the roller surface, bearing cyclic resistance and transmission error, and reduce the ineffective repeated adjustment of the PID controller for fixed periodic disturbances.

[0015] 2. The present invention uses the difference between the current equivalent load and the reference value of the periodic load at the same angular position as the material load residual, separates the periodic mechanical load from the non-periodic material load, and identifies the material load pack accordingly, so that the identification result can more accurately reflect the material agglomeration, material hardness change and feeding impact.

[0016] 3. This invention uses the time-shift relationship between material conveying distance, material conveying speed and historical upstream and downstream material load residuals to predict the arrival time and load intensity of the material load package. This enables the downstream PID controller to preset the integral state, torque output and torque change slope before the material load actually arrives, thereby reducing the speed drop and speed recovery time caused by sudden load increases.

[0017] 4. The present invention sets arrival verification windows before and after the predicted arrival time, and verifies the arrival time deviation, residual change trend, peak load deviation and load energy deviation respectively; when the verification is successful, it smoothly switches to the actual speed error closed-loop adjustment; when the verification fails, it gradually cancels the preset state, which can avoid integral saturation, torque step and speed reverse fluctuation caused by incorrect prediction.

[0018] 5. When the residual torque margin of the downstream drive motor is insufficient, the present invention allocates the speed compensation amount according to the actual available residual torque margin of the adjacent drive motor, and maintains the ratio of the roller surface linear velocity of the adjacent grinding rollers, thereby improving the collaborative operation capability of the multi-roller grinding equipment under high load conditions and reducing the risk of material slippage, accumulation and blockage. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart illustrating the overall method of the present invention; Figure 2 This is a schematic diagram illustrating the synchronous acquisition of operational data, corner domain mapping, and equivalent load calculation of the present invention. Figure 3 This is a schematic diagram of the construction of the roller circumferential load template and the separation of material load residuals according to the present invention; Figure 4 This is a schematic diagram of the material load package propagation prediction, downstream PID state preset, and adjacent roller compensation allocation of the present invention. Figure 5 This is a schematic diagram of the material load package arrival verification and closed-loop correction process of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the described embodiments are only for illustrating the present invention and are not intended to limit the scope of protection of the present invention. Adaptive adjustments made by those skilled in the art to the data acquisition frequency, the number of angular domain divisions, the form of the driving device, the control cycle, and the parameter values ​​without departing from the technical concept of the present invention should all fall within the scope of protection of the present invention.

[0021] Example 1: Please see Figures 1 to 5 This invention provides a PID closed-loop control method for the rotational speed of a grinding roller, applicable to a grinding equipment including an upstream grinding roller, a downstream grinding roller, a drive motor, a frequency converter, a material conveying mechanism, an angular position detector, a speed detector, and a controller.

[0022] Upstream and downstream grinding rollers are arranged sequentially along the material conveying direction and are each independently driven by a corresponding drive motor. The drive motors are connected to their respective grinding rollers via transmission mechanisms, and the frequency converter adjusts the output torque of the drive motors according to the target torque command output by the controller. An angular position detector is located at the end of the grinding roller shaft or the drive motor shaft to acquire angular position pulses and reference pulses per revolution; a speed detector is used to acquire the actual speed of the grinding rollers; and the frequency converter outputs an estimated value of the drive motor current or torque to the controller. The controller is communicatively connected to the angular position detector, speed detector, frequency converter, and material conveying mechanism.

[0023] In this embodiment, the rated torque of the drive motor is 500 N·m, the maximum allowable torque is 650 N·m, and the allowable torque change rate is 1200 N·m / s; the rated speed of the grinding roller is 180 r / min, and the allowable continuous operating speed range is 120 to 240 r / min; the PID control cycle of the controller is 1 ms.

[0024] S1: Synchronously collect running data and perform corner domain mapping The controller synchronously acquires the instantaneous angular position, actual speed, and corresponding drive motor output torque of the upstream and downstream grinding rollers. When the drive motor is equipped with a torque sensor, the output value of the torque sensor is directly used as the output torque of the drive motor; when the drive motor is not equipped with a torque sensor, the estimated torque value output by the frequency converter driver is read, or the output torque of the drive motor is determined based on the product of the drive motor current and the motor torque coefficient.

[0025] The motor torque coefficient is initially determined by the ratio of the rated torque to the rated torque current of the drive motor, and is calibrated using a standard torque sensor during the equipment commissioning phase. During calibration, 20%, 40%, 60%, and 80% of the drive motor's rated torque are used as calibration load points, and the calculated and measured torques are recorded respectively. When the relative error between the two exceeds 5%, the motor torque coefficient is corrected until the relative error at each calibration load point does not exceed 5%.

[0026] The angular position detector uses an incremental encoder that outputs 2048 pulses per revolution. The incremental encoder outputs a reference pulse per revolution in each rotation cycle. The controller determines the position corresponding to the reference pulse per revolution as the angular position zero point, and determines the current instantaneous angular position based on the number of angular position pulses accumulated after the angular position zero point.

[0027] The controller's data sampling frequency is set to 2000Hz, and the single rotation cycle of the grinding roller is divided into 72 continuous angular domain intervals, each corresponding to a 5° roller rotation angle. The number of angular domain intervals is determined based on the maximum operating speed of the grinding roller, the controller's sampling frequency, and the resolution of the angular position detector. When the grinding roller is running at its maximum operating speed of 240 r / min, the single rotation cycle is 0.25s. At a sampling frequency of 2000Hz, 500 sampling points are obtained per rotation cycle. After mapping these 500 sampling points to the 72 angular domain intervals, an average of 6.94 sampling points are obtained per angular domain interval, ensuring that each angular domain interval has at least 4 valid sampling points.

[0028] The controller maps the actual rotational speed and output torque to the corresponding angular domain intervals based on the instantaneous angular position at each sampling moment. When the instantaneous angular position is between the center positions of two adjacent angular domain intervals, the data of the two adjacent angular domain intervals are linearly interpolated according to the angular distances from the instantaneous angular position to the two center positions.

[0029] Because the angular position detection channel, speed detection channel, and torque acquisition channel have different sampling and communication delays, a step test signal is synchronously input to each acquisition channel during the equipment debugging phase. Delay calibration is performed 10 times consecutively, and the median value of the delay test results for each acquisition channel is used as the corresponding delay correction value. In this embodiment, the delay correction value for the angular position detection channel is 1.0 ms, the delay correction value for the speed detection channel is 2.5 ms, and the delay correction value for the torque acquisition channel is 4.0 ms. The controller corrects the timestamps of each operating data according to the above delay correction values, ensuring that the instantaneous angular position, actual speed, and output torque use a unified time reference.

[0030] S2: Calculate the equivalent load on the grinding roller. The controller determines the equivalent load of each grinding roller within its corresponding angular range based on the drive motor output torque, transmission ratio, transmission efficiency, equivalent inertia of the transmission system, angular acceleration of the grinding rollers, and no-load torque. The drive motor output torque is converted to the grinding roller shaft side based on the transmission ratio and transmission efficiency to obtain the roller shaft-side drive torque. The grinding roller angular acceleration is determined based on the actual rotational speed at adjacent sampling times, and the inertial torque is determined based on the equivalent inertia of the transmission system. The equivalent load of the grinding rollers is calculated using the following formula:

[0031] In the formula, Indicates the first The grinding roller is in the first... The equivalent load at each sampling time, in units of ; Indicates the first Each grinding roller corresponds to the output torque of the drive motor, in units of... ; This represents the transmission ratio of the drive motor output torque converted to the shaft side of the grinding roller, and is a dimensionless parameter; This represents the transmission efficiency, which is a dimensionless parameter. This represents the equivalent moment of inertia of the transmission system referred to the shaft side of the grinding roller, in units of... ; Indicates the first The angular acceleration of each grinding roller, in units of ; Indicates the first The no-load torque of a grinding roller at the current angular velocity, in units of ; Indicates the first The current angular velocity of each grinding roller, in units of / In formula (1), the driving torque, inertial torque, and no-load torque are all calculated using... As a unified unit, the product of the equivalent inertia and angular acceleration of the transmission system corresponds to the inertial torque.

[0032] In this embodiment, the transmission ratio from the drive motor to the grinding roller is 3.5, the transmission efficiency is 0.92, and the equivalent inertia of the transmission system referred to the shaft side of the grinding roller is 8.6. The equivalent inertia of the transmission system was calculated based on the rotational inertia of the drive motor rotor, coupling, reduction mechanism, and grinding roller, and verified through no-load acceleration and deceleration tests. During verification, three acceleration and deceleration tests were performed at 120 km / h. Accelerate to 180 Accelerated testing and three trials by 180 Reduce speed to 120 The deceleration test was conducted, and the equivalent inertia of the transmission system was corrected based on the correspondence between the measured driving torque, no-load torque and angular acceleration.

[0033] To reduce the impact of rotational speed detection noise on angular acceleration calculation results, a sliding median filter with a length of 10 sampling points is used for the actual rotational speed. At a sampling frequency of 2000Hz, 10 sampling points correspond to 5ms, which can filter out individual sampling spikes without affecting the identification timing of the material load package.

[0034] The no-load torque is determined by the stable output torque of the grinding rollers running at 120 r / min, 150 r / min, 180 r / min, 210 r / min, and 240 r / min without material. Each calibrated speed is run for 60 seconds, and the acceleration and stabilization data of the first 10 seconds are discarded. The median value of the output torque in the last 50 seconds is taken as the no-load torque at the corresponding calibrated speed. In this embodiment, the no-load torques corresponding to the above five calibrated speeds are 42 N·m, 46 N·m, 51 N·m, 57 N·m, and 64 N·m, respectively. When the actual speed is between two adjacent calibrated speeds, linear interpolation is performed on the two adjacent no-load torques; when the actual speed is below 120 r / min or above 240 r / min, the no-load torque corresponding to 120 r / min or 240 r / min is used respectively to avoid extrapolation outside the calibrated range.

[0035] S3: Constructing a Roll Cyclic Load Template The controller determines whether the current rotation cycle of the grinding roller meets the template sample cycle conditions. In this embodiment, a rotation cycle is determined to be a template sample cycle when the following conditions are met simultaneously: the deviation between the actual rotation speed and the target rotation speed does not exceed 2% of the target rotation speed; the output torque of the drive motor does not exceed 85% of the maximum allowable torque; no slippage alarm, overload alarm, or material blockage alarm is generated during the rotation cycle; the material load residual does not exceed the load pack starting threshold; and the deviation of the material supply speed from the set material supply speed does not exceed 5%.

[0036] The 2% speed deviation threshold is determined based on normal and stable equipment operation tests. After the equipment runs continuously for 30 minutes at the rated material supply speed, the fluctuation range of the actual speed relative to the target speed is statistically analyzed. The 95th percentile of the obtained speed fluctuation range is 1.6%, rounded up, and 2% is determined as the speed stability threshold for the template sample cycle. The drive motor output torque threshold is set to 85% of the maximum allowable torque to stop template updates before the drive motor enters a high-load state, preventing abnormal material loads from being written into the roller cycle load template.

[0037] The controller selects 20 consecutive template sample periods and performs robust statistics on the historical equivalent load within the same corner domain interval. For each corner domain interval, the 20 historical equivalent loads are arranged in ascending order of value. The two historical equivalent loads with the smallest value and the two historical equivalent loads with the largest value are removed. The arithmetic mean of the remaining 16 historical equivalent loads is calculated, and the result is used as the reference value of the periodic load for that corner domain interval.

[0038] Twenty rotational cycles were chosen as the template sample size because, at the target rotational speed of 180 r / min, 20 rotational cycles correspond to approximately 6.67 s, which is sufficient to cover the cyclic mechanical load across multiple consecutive rotational cycles without causing significant lag in the template's tracking of changes in equipment operating status. 10% of the historical equivalent load was removed before and after the initial load to reduce the impact of occasional material impacts and sampling anomalies on the cyclic load baseline value.

[0039] The controller combines the angular position reference values ​​of each cycle according to the angular position sequence of 72 angular domain intervals to form a roller circumferential load template. The roller circumferential load template is used to characterize the angular position synchronization load caused by grinding roller eccentricity, local wear on the roller surface, bearing cyclic resistance, and transmission error.

[0040] Under normal operating conditions, the roller cyclic load template is recursively updated after each template sample cycle. When the material category and target speed remain unchanged, the update ratio of the current rotation cycle data in the template update is set to 0.05. After the material category is switched, the update ratio for the first 10 effective rotation cycles is set to 0.15, and then returns to 0.05. The update ratio is determined based on template tracking tests. When the update ratio is lower than 0.03, the roller cyclic load template tracks roller surface wear and changes in transmission status too slowly; when the update ratio is higher than 0.20, non-cyclic material loads are more likely to enter the template. Therefore, the update ratio under stable operating conditions is set to 0.05, and the update ratio after material category switching is set to 0.15.

[0041] The update of the roller cycle load template will be frozen when any of the following occurs: the material load residual exceeds the load pack initial threshold; the actual rotational speed decreases by more than 5% relative to the target rotational speed; the drive motor output torque reaches 85% of the maximum allowable torque; the equipment generates a slippage alarm; the equipment generates an overload alarm; or the equipment generates a material blockage alarm. After the above abnormal conditions are resolved, the template update will only resume when the template sample cycle conditions are met again after 5 consecutive rotational cycles, to prevent short-term load oscillations after the abnormal state is resolved from entering the roller cycle load template.

[0042] S4: Separate material load residuals and generate angular position synchronous feedforward compensation. The controller queries the periodic load reference value of the corresponding angular region from the roller circumferential periodic load template based on the current instantaneous angular position of the grinding roller. When the current instantaneous angular position coincides with the center position of the angular region, the periodic load reference value of that angular region is directly read; when the current instantaneous angular position is between the centers of two adjacent angular regions, the adjacent two periodic load reference values ​​are linearly interpolated based on the angular distances from the current instantaneous angular position to the two center positions. The material load residual is calculated according to formula (2):

[0043] In the formula, Indicates the first The grinding roller is in the first... Material load residual at each sampling time, in units of ; Indicates the first The grinding roller is in the first... The equivalent load at each sampling time, in units of ; Indicates the first The reference value of the periodic load corresponding to the current instantaneous angular position of each grinding roller, in units of ; Indicates the first The grinding roller is in the first... The instantaneous angular position at each sampling moment, in degrees.

[0044] In Formula (2), both the current equivalent load and the cyclic load reference value are expressed in N·m as a unified unit, and the unit of the resulting material load residual is N·m. By subtracting the cyclic load reference value at the same angular position from the current equivalent load, the material load residual mainly reflects the non-cyclic load formed by changes in feed rate, changes in material hardness, material agglomeration, and material impact.

[0045] The controller generates angular position synchronization feedforward compensation based on the periodic load reference value and the drive motor torque transmission coefficient. The drive motor torque transmission coefficient is determined through equipment no-load testing: additional torque commands of 20 N·m, 40 N·m, 60 N·m, and 80 N·m are applied sequentially to the frequency converter driver, and the actual torque change on the shaft side of the grinding roller is recorded. The median value of the ratio of the commanded torque change to the actual torque change on the shaft side is taken as the torque transmission coefficient.

[0046] In this embodiment, the torque transmission coefficient is 0.94. The absolute value of the angular position synchronous feedforward compensation does not exceed 15% of the rated torque of the drive motor, i.e., not more than 75 N·m; the slope of the change of the angular position synchronous feedforward compensation does not exceed 70% of the allowable torque change rate of the drive motor, i.e., not more than 840 N·m / s.

[0047] The amplitude threshold and slope threshold of the angular position synchronous feedforward compensation were determined through no-load and rated load tests. Comparative tests were conducted with the feedforward compensation amplitude set to 10%, 15%, and 20% of the rated torque of the drive motor, respectively, and the slope thresholds were set to 50%, 70%, and 90% of the allowable torque change rate, respectively. Using the selection criteria of additional speed fluctuation not exceeding 1% of the target speed and not producing a torque step, the amplitude threshold was determined to be 15% of the rated torque, and the slope threshold to be 70% of the allowable torque change rate.

[0048] The controller adds the angular position synchronization feedforward compensation amount to the feedback control amount generated by the PID controller based on the target speed and the actual speed to form the target torque command for the drive motor, so that the periodic mechanical load synchronized with the angular position is compensated before it causes a significant speed error.

[0049] S5: Identify the material load package of the upstream grinding roller. The controller extracts the material load residual of the upstream grinding roller from the most recent 100 rotation cycles that meet the template sample cycle conditions, calculates the median value and median absolute deviation of the material load residual, and determines the sum of the median value of the material load residual and 3 times the median absolute deviation as the load pack starting threshold.

[0050] The threshold multiple of 3 was determined based on false triggering tests during normal equipment operation. When the threshold multiple is less than 2.5, the number of false identifications caused by normal material particle fluctuations increases significantly; when the threshold multiple is greater than 3.5, material loads with small amplitudes but long durations are prone to being missed. Therefore, the threshold multiple is set to 3.

[0051] In this embodiment, the median value of the historical material load residual is 8 N·m, and the median absolute deviation is 14 N·m, thus determining the load pack initial threshold to be 50 N·m. The controller further calculates the rise rate of the material load residual over the aforementioned 100 rotation cycles and determines the 95th percentile of the rise rate as the load pack rise rate threshold. In this embodiment, the load pack rise rate threshold is 420 N·m / s.

[0052] The material load packet is determined to begin when the material load residual of the upstream grinding roller exceeds 50 N·m, the rate of increase of the material load residual exceeds 420 N·m / s, and both conditions are maintained continuously for at least 50 ms. The initial confirmation time of 50 ms is greater than the sum of the torque acquisition channel delay and the filtering window time, which can eliminate single sampling spikes and short-term electromagnetic interference.

[0053] The controller determines the load pack end threshold as 60% of the load pack start threshold. In this embodiment, the load pack end threshold is 30 N·m. When the material load residual is below 30 N·m and remains below that for 100 ms, the material load pack is considered to have ended. Setting the load pack end threshold to 60% of the load pack start threshold creates a 20 N·m hysteresis interval, preventing the same continuous load process from being repeatedly divided when the material load residual fluctuates near the load pack start threshold. The 100 ms end confirmation time is determined based on the shortest time required for the equipment to recover from the material impact state to a stable state, and is greater than the start confirmation time.

[0054] Between the start and end times of the material load pack, the controller determines the duration of the material load pack, takes the largest material load residual within this time interval as the peak load, and uses the ratio of the change in material load residual to the sampling time interval between adjacent sampling times as the load change slope, extracting the maximum load change slope. The controller integrates the material load residual over time within the duration of the material load pack to obtain the load energy. The unit of load energy is N·m·s, used to characterize the comprehensive load effect applied to the grinding roller by the material load pack during the duration.

[0055] S6: Predict the arrival time and load intensity of the material load package The controller acquires the material conveying distance and current material conveying speed between the upstream and downstream grinding rollers. The material conveying distance is determined by the actual conveying path length between the material's position leaving the upstream grinding zone and entering the downstream grinding zone, rather than the straight-line distance between the axes of the upstream and downstream grinding rollers. In this embodiment, the material conveying distance is 1.20m. The current material conveying speed is obtained by an encoder mounted on the drive shaft of the material conveying mechanism. When the encoder outputs the drive shaft speed, the speed is converted into the material conveying linear velocity based on the effective circumference of the drive rollers, with the unit being m / s.

[0056] The predicted arrival time of the material load package to the downstream grinding roller is calculated according to formula (3):

[0057] In the formula, This indicates the predicted arrival time of the material load pack to the downstream grinding roller, in units of... ; Indicates the start time of the material loading package at the upstream grinding roller, in units of... ; This indicates the material conveying distance between the upstream and downstream grinding rollers, in units of... ; This indicates the current material conveying speed, in units of... ; This represents the historical propagation correction amount, in units of... In formula (3), the unit of the ratio of material conveying distance to material conveying speed is _____. It has the same dimensions as the historical propagation correction quantity.

[0058] The historical propagation correction is determined based on the time-shift relationship between historical upstream and downstream material load residuals. The ratio of material conveying distance to the current material conveying speed is used as the base propagation time. A candidate time-shift range is formed by extending this base propagation time forward and backward by 50% of the base propagation time. The controller applies different candidate time-shift amounts to the historical upstream material load residuals using one sampling period as the candidate time-shift step size, and calculates the correlation coefficient between the time-shifted upstream material load residual and the historical downstream material load residual. The difference between the candidate time-shift amount corresponding to the maximum correlation coefficient and the base propagation time is used as the historical propagation correction.

[0059] Historical propagation data is used to determine and update historical propagation corrections only when the maximum correlation coefficient is not less than 0.70. The correlation coefficient threshold of 0.70 is determined based on historical material load pack matching tests of the equipment. When the correlation coefficient is not less than 0.70, the material load pack mismatch rate is less than 5%; historical data with a correlation coefficient less than 0.70 are judged as non-corresponding load data caused by material dispersion, changes in conveying status, or human intervention.

[0060] The controller stores historical material load packages according to material category and material conveying speed range. The material category is determined by the production formula number or material batch number, and the material conveying speed is divided into multiple speed ranges at intervals of 0.10 m / s. From the historical data of the same material category and material conveying speed within the same speed range as the current data, the 30 most recently verified material load packages are selected, and the ratio of downstream peak load to upstream peak load, as well as the ratio of downstream load energy to upstream load energy, are calculated.

[0061] The controller uses the median value of the peak load ratio as the peak load propagation coefficient and the median value of the load energy ratio as the load energy propagation coefficient. Using the median value avoids excessive influence of individual material blockages, material spillage, and abnormal sensor data on the propagation coefficients. The predicted peak load of the downstream grinding roller is obtained by multiplying the peak load of the current upstream material load package by the peak load propagation coefficient; the predicted load energy of the downstream grinding roller is obtained by multiplying the load energy of the current upstream material load package by the load energy propagation coefficient. The predicted peak load and predicted load energy together constitute the predicted load intensity.

[0062] If the number of successfully verified historical material load packages within the same material category and the same material conveying speed range is less than 5, historical data from adjacent material conveying speed ranges are retrieved. If the number of valid historical data from adjacent material conveying speed ranges is still less than 5, the initial propagation coefficient calibrated during the equipment commissioning phase is used. In this embodiment, the initial peak load propagation coefficient is 0.85, and the initial load energy propagation coefficient is 0.80.

[0063] S7: Preset the control state of the downstream PID controller The controller determines the predicted compensation torque required to maintain the target speed when the material load package arrives at the downstream grinding roller based on the predicted peak load. Considering the drive torque estimation error and torque transmission error, 1.05 times the predicted peak load is determined as the predicted compensation torque. The coefficient 1.05 is used to compensate for torque estimation errors not exceeding 5%, and is not used for the weighted calculation of multiple evaluation indicators.

[0064] The target torque command of the downstream PID controller is calculated according to formula (4):

[0065] In the formula, Indicates the first Each grinding roller corresponds to a target torque command for the drive motor, in units of... ; This represents the proportionality coefficient, with units of 1000g. / ( ); This represents the speed error between the target speed and the actual speed, expressed in units of... ; Represents the integral coefficient, in units of / [( )· ]; The time integral representing the rotational speed error, in units of ( )· ; Represents the differential coefficient, in units of / ( ); express Control cycle, unit is ; This represents the angular position synchronization feedforward compensation amount, in units of... ; This indicates the preset torque amount to be applied before the material load pack arrives, in units of... The proportional control component, integral control component, derivative control component, angular position synchronous feedforward compensation, and torque preset in formula (4) all adopt... As a unified unit of measurement.

[0066] The proportional, integral, and derivative coefficients of the PID controller were determined through no-load speed step tests and rated load step tests. In this embodiment, the proportional coefficient of the downstream grinding roller was set to 6.5 N·m / (r / min), the integral coefficient was set to 18 N·m / [(r / min)·s], and the derivative coefficient was set to 0.12 N·m·s / (r / min). The specific parameter determination rules are as follows: First, a target speed step of 10 r / min is applied under no-material conditions, ensuring that the overshoot of the actual speed does not exceed 3% of the target speed and the settling time does not exceed 1.0 s; then, a load step of 20% of the rated torque of the drive motor is applied, ensuring that the maximum speed drop of the grinding roller does not exceed 5% of the target speed and that the slope of the output torque change of the drive motor does not exceed the allowable torque change rate.

[0067] The controller determines the initial torque margin based on the difference between the maximum allowable torque of the downstream drive motor and the current output torque, and subtracts the safety reserve torque from the initial torque margin to obtain the remaining torque margin. The safety reserve torque is the larger of 10% of the drive motor's rated torque and the 95th percentile of the drive motor's output torque fluctuation under normal operating conditions. In this embodiment, 10% of the drive motor's rated torque is 50 N·m, and the 95th percentile of the output torque fluctuation is 42 N·m; therefore, the safety reserve torque is determined to be 50 N·m.

[0068] When the predicted compensation torque is not greater than the remaining torque margin, 30% of the predicted compensation torque is applied through the integral state of the PID controller, and 70% is applied as the torque preset value. The 30% and 70% mentioned above are the distribution ratios of the same predicted compensation torque between the integral preset channel and the torque preset channel, not the evaluation weights of multiple indicators. This distribution ratio is determined through a load step test. When the integral preset ratio is below 20%, the steady-state speed error during the continuous phase of the material load is relatively large; when the integral preset ratio is above 40%, integral residue is easily generated after the material load disappears. Therefore, the integral preset ratio is set to 30%, and the torque preset ratio is set to 70%.

[0069] In this embodiment, the integral and torque preset values ​​are loaded starting 300ms before the predicted arrival time, using a continuously increasing ramp method to ensure that the integral and torque preset values ​​reach their corresponding target values ​​before the predicted arrival time. The preset start time is determined based on the drive system torque setup time and the shortest duration of the historical material load package. In this embodiment, the time required for the drive system to reach the target torque value from receiving the target torque command is no more than 120ms, and the shortest duration of the historical material load package is 240ms; therefore, the preset start time is set to 300ms before the predicted arrival time.

[0070] The slope of the torque preset change is taken as the smaller of the slope of the maximum load change of the material load pack and the allowable torque change rate of the drive motor, and is limited to no more than 1000 N·m / s. The integral preset is subject to integral amplitude limiting. The torque corresponding to the integral control component must not exceed the remaining torque after deducting the proportional control component, derivative control component, angular position synchronization feedforward compensation, torque preset, and safety reserve torque from the maximum allowable torque of the drive motor. During the integral state and torque preset loading process, the target speed of the downstream grinding roller remains unchanged to improve the downstream PID controller's ability to handle the incoming material load pack.

[0071] S8: Distribute speed compensation when the residual torque margin is insufficient. When the predicted compensation torque exceeds the residual torque margin of the downstream drive motor, the controller obtains the residual torque margin of the drive motors corresponding to the downstream grinding rollers and their adjacent grinding rollers. The controller subtracts the corresponding safety reserve torque from the initial torque margin of each drive motor to obtain the available residual torque margin of each drive motor. Then, based on the proportion of each drive motor's available residual torque margin to the sum of all available residual torque margins, the controller allocates the speed compensation amount to each drive motor. This allocation process is based on the actual available torque of the drive motor and does not incorporate subjective evaluation weights.

[0072] Based on the effective radius of each grinding roller, the rotational speed compensation is converted into a roller surface linear velocity compensation. After compensation, the deviation of the roller surface linear velocity ratio between adjacent grinding rollers from the normal operating setting should not exceed 2%. The 2% deviation threshold for the roller surface linear velocity ratio is determined through a material slippage test. When the deviation exceeds 3%, the degree of shearing on the material surface and the probability of roller surface slippage increase significantly. Therefore, the allowable deviation is set to 2% to retain a safety margin of no less than 1 percentage point.

[0073] When the output torque of any drive motor reaches its maximum allowable torque, the increase of the speed compensation amount undertaken by that drive motor stops, and the unallocated speed compensation amount is transferred to the drive motor that still has residual torque margin.

[0074] When the sum of the available residual torque margins of all drive motors is less than the predicted compensation torque, the controller reduces the material supply speed of the material conveying mechanism. Initially, the current material supply speed is reduced by 10%, and the available residual torque margins of all drive motors are reassessed every 0.5 seconds. If the available residual torque margins are still insufficient, the current material supply speed is further reduced by 10% until it reaches 40% of the normal set value. When the material supply speed reaches 40% of the normal set value, if the available residual torque margins of all drive motors are still less than the predicted compensation torque, the material conveying mechanism is stopped and an overload warning signal is output.

[0075] S9: Perform material load pack arrival verification and closed-loop correction. The controller establishes an arrival verification window before and after the predicted arrival time. In this embodiment, the start point of the arrival verification window is 0.20 seconds before the predicted arrival time, and the end point is 0.30 seconds after the predicted arrival time. The range of the verification window is determined based on historical arrival time prediction errors. During the equipment commissioning phase, statistics on 100 successfully verified material load packages showed that 95% of the actual arrival times deviated from the predicted arrival times by 0.16 to 0.24 seconds. Therefore, the arrival verification window is extended by 0.20 seconds before the predicted arrival time and by 0.30 seconds after the predicted arrival time.

[0076] Within the verification window, the controller extracts the actual start time, actual peak load, actual load energy and trend of the material load residual of the downstream grinding roller, and calculates the time deviation between the actual start time and the predicted arrival time, the relative deviation between the actual peak load and the predicted peak load, the relative deviation between the actual load energy and the predicted load energy, and the correlation coefficient of the upstream and downstream material load residuals after time shift alignment.

[0077] The material load package is considered successfully verified when the absolute deviation between the actual start time and the predicted arrival time does not exceed 0.15s, the correlation coefficient of the upstream and downstream material load residuals after time-shift alignment is not less than 0.70, the relative deviation between the actual peak load and the predicted peak load does not exceed 25%, and the relative deviation between the actual load energy and the predicted load energy does not exceed 30%. The above verification process uses a condition-by-condition judgment method, without weighting the time deviation, correlation coefficient, peak load deviation, and load energy deviation, thereby avoiding the influence of the evaluation weight selection on the verification results.

[0078] The time deviation threshold of 0.15s is determined based on the 90th percentile of the absolute value of the historical arrival time prediction error; the correlation coefficient threshold of 0.70 is determined based on the requirement that the mismatch rate does not exceed 5%; the peak load relative deviation threshold of 25% and the load energy relative deviation threshold of 30% are determined by rounding up the 95th percentile of the historical corresponding error.

[0079] Upon successful verification, the controller gradually reduces the integral and torque preset values ​​within a 0.30s transition time, and gradually increases the PID feedback control component based on the actual speed error, enabling the downstream PID controller to smoothly switch from the preset state to the actual speed error closed-loop adjustment state. The controller corrects the historical propagation correction based on the difference between the actual and predicted arrival times, corrects the peak load propagation coefficient based on the ratio of the actual peak load to the upstream peak load, and corrects the load energy propagation coefficient based on the ratio of the actual load energy to the upstream load energy.

[0080] The single update ratio of the propagation parameters is normally set to 0.10. After five consecutive successful verifications with the absolute deviation between the actual arrival time and the predicted arrival time not exceeding 0.05 seconds, the single update ratio is reduced to 0.05. For the first five verifications after a material category switch, the single update ratio is increased to 0.20. This allows the propagation parameters to update slowly under stable operating conditions and adapt quickly after a material category switch.

[0081] If no downstream material load package meeting all four verification conditions is detected within the verification window, the material load package verification is deemed a failure. Upon verification failure, the controller cancels the integral preset, torque preset, and reallocated speed compensation within 0.30–0.60 seconds, according to a release slope not exceeding the preset loading slope. The angular position synchronous feedforward compensation continues to operate based on the roller circumferential load template, restoring the downstream PID controller to a speed closed-loop control state that does not include the material load package preset component.

[0082] Example 2: This embodiment illustrates the specific operation process of the PID closed-loop control method for the grinding roller speed. The effective diameter of the upstream grinding roller is 0.42m, and the target speed is 180r / min; the effective diameter of the downstream grinding roller is 0.40m, and the target speed is 189r / min. After setting the effective diameter and target speed as described above, the set roller surface linear velocity of the upstream grinding roller is approximately 3.96m / s, and the set roller surface linear velocity of the downstream grinding roller is approximately 3.96m / s, ensuring that the upstream and downstream grinding rollers maintain the same roller surface linear velocity under normal conditions.

[0083] The material conveying distance between the upstream and downstream grinding rollers is 1.20m, and the current material conveying speed is 0.80m / s. Based on the most recent 30 successfully verified historical material load packages, the historical propagation correction is determined to be 0.12s, the peak load propagation coefficient is 0.86, and the load energy propagation coefficient is 0.81.

[0084] At a certain operating moment, the upstream grinding rollers detected a material load. The peak load of this material load was 165 N·m, the duration was 0.42 s, the maximum load change slope was 760 N·m / s, and the load energy was 48 N·m·s. According to formula (3), the basic propagation time of the material load was 1.20 m divided by 0.80 m / s, which was calculated to be 1.50 s. The basic propagation time of 1.50 s was added to the historical propagation correction amount of 0.12 s to obtain the predicted propagation time of 1.62 s.

[0085] Based on a peak load propagation coefficient of 0.86, the predicted peak load of the downstream grinding roller is 141.90 N·m; based on a load energy propagation coefficient of 0.81, the predicted load energy of the downstream grinding roller is 38.88 N·m·s. Taking 1.05 times the predicted peak load as the predicted compensation torque, the predicted compensation torque is obtained as 149.00 N·m.

[0086] At this point, the maximum allowable torque of the downstream drive motor is 650 N·m, the current output torque is 430 N·m, and the safety reserve torque is 50 N·m. Therefore, the remaining torque margin of the downstream drive motor is 170 N·m. Since the predicted compensation torque of 149.00 N·m is less than the remaining torque margin of 170 N·m, the downstream drive motor independently undertakes the preset compensation. The controller starts loading the preset compensation 300 ms before the predicted arrival time. Among them, 30% of the predicted compensation torque, i.e., 44.70 N·m, is preset through the integral state of the PID controller; 70% of the predicted compensation torque, i.e., 104.30 N·m, is loaded as the torque preset amount.

[0087] The maximum load change slope of the material load pack is 760 N·m / s, which is less than the allowable torque change rate of the drive motor of 1200 N·m / s. Therefore, the loading slope of the torque preset amount is set to 760 N·m / s.

[0088] Within the verification window, the actual arrival time of the downstream material load package was detected to be 0.08 s later than the predicted arrival time. The actual peak load was 148 N·m, and the actual load energy was 40.20 N·m·s. The correlation coefficient of the upstream and downstream material load residuals after time-shift alignment was 0.81. Specifically, the time deviation of 0.08 s is less than the time deviation threshold of 0.15 s; the relative deviation between the actual peak load and the predicted peak load is approximately 4.30%, less than the peak load relative deviation threshold of 25%; the relative deviation between the actual load energy and the predicted load energy is approximately 3.40%, less than the load energy relative deviation threshold of 30%; and the correlation coefficient of 0.81 is greater than the correlation coefficient threshold of 0.70. Therefore, the controller determines that the material load package verification was successful.

[0089] Within 0.30 seconds, the controller gradually decreases the integral preset and torque preset, and gradually increases the PID feedback control component based on the actual speed error, enabling the downstream PID controller to smoothly switch to the closed-loop adjustment state based on the actual speed error. Subsequently, the controller corrects the historical propagation correction, peak load propagation coefficient, and load energy propagation coefficient according to a single update ratio of 0.10, completing the closed-loop correction of this material load package propagation process.

[0090] After adopting the above control method, when the material load bag reaches the downstream grinding roller, the maximum speed drop of the downstream grinding roller is reduced from 5.8% when no state preset control is used to 1.7%, the speed recovery time is shortened from 1.26s to 0.44s, and the maximum change slope of the drive motor output torque is 825N·m / s, which does not exceed the allowable torque change rate of 1200N·m / s.

[0091] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, adjustments or substitutions can be made to the sampling parameters, number of angular domain intervals, number of template sample periods, threshold determination method, and driving control parameters in the above embodiments without departing from the principles and technical concept of the present invention. All such adjustments or substitutions should be included within the protection scope of the present invention.

[0092] The above embodiments provide a detailed description of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A PID closed-loop control method for the rotational speed of a grinding roller, characterized in that, The method, applied to upstream and downstream grinding rollers arranged sequentially along the material conveying direction, includes: The angular position, actual speed and output torque of the corresponding drive motor of each grinding roller are collected synchronously. A single rotation cycle is divided into multiple angular domain intervals, and the actual speed and output torque are mapped to the corresponding angular domain intervals. Based on the output torque, grinding roller angular acceleration, transmission system equivalent inertia, and no-load torque, the equivalent load of each angular domain interval is determined; the equivalent load of continuous rotation cycles is aligned by angular position, and the historical equivalent load within the same angular domain interval is robustly statistically analyzed to form a roller circumferential load template, and the roller circumferential load template is stopped from being updated under abnormal load conditions. Subtract the periodic load reference value at the same angular position in the roller circumferential periodic load template from the current equivalent load to obtain the material load residual, and generate the angular position synchronous feedforward compensation amount based on the periodic load reference value. When the material load residual of the upstream grinding roller meets the load pack start condition, a material load pack is established and the start time, duration, peak load, load change slope and load energy are extracted. Based on the material conveying distance between the upstream and downstream grinding rollers, the material conveying speed, and the time shift relationship of the historical upstream and downstream material load residuals, the predicted arrival time and predicted load intensity of the material load package are determined. Before the predicted arrival time, the integral state, torque preset amount and torque change slope of the downstream PID controller are preset according to the predicted load intensity, the equivalent inertia of the downstream grinding roller and the remaining torque margin of the downstream drive motor. An arrival verification window is established before and after the predicted arrival time, and the material load package is verified based on the material load residual of the downstream grinding roller. When the verification is successful, the downstream PID controller is smoothly switched from the preset state to the speed error closed-loop adjustment state, and the material propagation parameters are updated. If the verification fails, the preset is canceled according to the limited release slope, and the original closed-loop control state of the downstream PID controller is restored.

2. The PID closed-loop control method for grinding roller speed according to claim 1, characterized in that, The synchronous acquisition and mapping includes: An angular position pulse and a reference pulse per revolution are obtained by an angular position detector installed at the end of the grinding roller shaft or the end of the drive motor shaft, and the angular position zero point of the rotation cycle is determined by the reference pulse per revolution. Based on the angular position pulse, the actual rotational speed and output torque are resampled in the angular domain so that the data of the same angular position in different rotation cycles are mapped to the same angular domain interval; The data timestamps are corrected based on the sampling delay and communication delay of the angular position detector, speed detector, and torque acquisition channel to ensure that all operating data adopt a unified time reference.

3. The PID closed-loop control method for grinding roller speed according to claim 2, characterized in that, The determination of the equivalent load includes: Calculate the motor output torque based on the drive motor current and motor torque coefficient, or read the estimated torque value output by the driver; Based on the transmission ratio and transmission efficiency, the motor output torque is converted to the grinding roller shaft side to obtain the roller shaft side drive torque; The angular acceleration is determined based on the actual rotational speed at adjacent sampling times, and the inertial torque corresponding to the equivalent inertia of the transmission system is calculated. The equivalent load is obtained by subtracting the inertial torque and the no-load torque corresponding to the current speed from the drive torque on the roller shaft side. The no-load torque is determined by establishing the correspondence between speed and no-load torque based on the stable torque of the grinding roller when it is running at at least 3 calibrated speeds without material.

4. The PID closed-loop control method for grinding roller speed according to claim 3, characterized in that, The formation of the roller circumferential load template includes: The continuous rotation period in which the actual speed deviation does not exceed the target speed limit, the drive motor output torque does not reach the torque limit, and the material load residual does not meet the load pack start condition is selected as the template sample period. For each corner domain interval, calculate the median or truncated mean of the historical equivalent load within the template sample period, and use the calculation result as the reference value of the periodic load for that corner domain interval. The roller circumferential load template is formed by combining the reference values ​​of each periodic load according to the angular position sequence of the angular domain interval. When the material load residual exceeds the load pack starting threshold, the actual speed drop exceeds the target speed limit, or the drive motor output torque reaches the torque limit, the update of the roller cycle load template is stopped until the continuous rotation cycle meets the template sample cycle conditions again.

5. The PID closed-loop control method for grinding roller speed according to claim 4, characterized in that, The generation of the material load residual and angular position synchronous feedforward compensation includes: Query the periodic load reference value in the roller circumferential periodic load template based on the current angular position; When the current angle position is located between adjacent angle domain intervals, linear interpolation is performed based on the angular distance between the current angle position and the center position of the adjacent angle domain interval. Calculate the difference between the current equivalent load and the interpolated periodic load reference value to obtain the material load residual; The angular position synchronous feedforward compensation amount is generated based on the periodic load reference value and the torque transmission coefficient of the drive motor, and the amplitude and slope of the feedforward compensation amount are limited. The angular position synchronization feedforward compensation amount is added to the feedback control amount generated by the PID controller based on the target speed and the actual speed to form the target torque command for the drive motor.

6. The PID closed-loop control method for grinding roller speed according to claim 5, characterized in that, The creation of the material load package includes: The median value and median absolute deviation of the residuals are calculated based on the historical material load residuals under normal operating conditions. The sum of the median value of the residuals and the median absolute deviation of the specified multiple is used as the load pack starting threshold. When the material load residual of the upstream grinding roller exceeds the load pack start threshold and its rate of increase exceeds the limit quantile of the historical normal change rate, and continues to reach the start confirmation time, the material load pack is determined to start. When the material load residual is lower than the load pack end threshold and continues to reach the end confirmation time, the material load pack is determined to end. The load pack end threshold is less than the load pack start threshold. The peak load and the maximum load change slope are determined within the start and end interval of the material load package, and the load energy is obtained by time integration of the material load residual.

7. The PID closed-loop control method for grinding roller speed according to claim 6, characterized in that, The determination of the predicted arrival time and predicted load intensity includes: The ratio of the material conveying distance to the current material conveying speed is used as the basic propagation time; Candidate time shifts are applied to the historical downstream material load residuals and correlation coefficients are calculated. The difference between the candidate time shift corresponding to the maximum correlation coefficient and the basic propagation duration is used as the propagation correction amount. The sum of the start time of the upstream material load package, the basic propagation time, and the propagation correction is used as the predicted arrival time. Based on the historical matching load packages within the pre-defined speed range belonging to the same material category and the current material conveying speed, the ratio of downstream peak load to upstream peak load and the ratio of downstream load energy to upstream load energy are calculated respectively. The current material load package is then corrected using the median value of the two ratios to obtain the predicted peak load and predicted load energy. The predicted load intensity includes the predicted peak load and predicted load energy.

8. The PID closed-loop control method for grinding roller speed according to claim 7, characterized in that, The presets for the downstream PID controller include: The predicted compensation torque required to maintain the target speed is determined based on the predicted peak load; the initial torque margin is determined based on the difference between the maximum allowable torque of the drive motor and the current output torque, and the safety reserve torque is subtracted from the initial torque margin to obtain the remaining torque margin; When the predicted compensation torque is not greater than the remaining torque margin, the predicted compensation torque is converted into an integral preset amount and a torque preset amount, and the load is applied in a continuously increasing ramp before the predicted arrival time. The slope of the torque preset amount is limited based on the smaller of the maximum load change slope of the material load pack and the allowable torque change rate of the drive motor. The integral preset value is limited to the usable torque range after deducting the proportional control component, the derivative control component, and the angular position synchronous feedforward compensation from the maximum allowable torque of the drive motor.

9. The PID closed-loop control method for grinding roller speed according to claim 8, characterized in that, When the predicted compensation torque is greater than the remaining torque margin: Obtain the remaining torque margin of the drive motor corresponding to the grinding roller adjacent to the downstream grinding roller; Based on the proportion of the remaining torque margin of each drive motor to the total available remaining torque margin, the speed compensation is distributed between the downstream grinding roller and adjacent grinding rollers. The rotational speed compensation is converted into the roller surface linear velocity compensation based on the effective radius of each grinding roller, and the deviation of the roller surface linear velocity ratio of adjacent grinding rollers after compensation relative to the normal operating setting value is limited. When any drive motor reaches its maximum allowable torque, the increase in the speed compensation of that drive motor stops, and the unallocated speed compensation is transferred to the adjacent drive motor that still has residual torque margin. When the sum of the remaining torque margins of all drive motors is less than the predicted compensation torque, the material supply speed of the feeding mechanism is reduced.

10. The PID closed-loop control method for grinding roller speed according to claim 9, characterized in that, The arrival verification and material propagation parameter updates include: Extract the actual start time, actual peak load, actual load energy and changing trend of the downstream material load residual within the verification window; Calculate the time deviation between the actual start time and the predicted arrival time, the relative deviation between the actual peak load and the predicted peak load, the relative deviation between the actual load energy and the predicted load energy, and the correlation coefficient of the upstream and downstream material load residuals after time shift alignment. When the time deviation, the two relative deviations, and the correlation coefficient are all within the acceptable range determined based on the historical matching load pack, the verification is deemed successful. Within the limited transition time, the integral preset amount and the torque preset amount are gradually reduced, and the feedback control component based on the actual speed error is gradually increased. The propagation correction is adjusted based on the actual arrival time, and the load intensity ratio is adjusted based on the actual peak load and the actual load energy. If no downstream material load residual that meets the acceptance range is detected, the verification is deemed to have failed, and the integral preset, torque preset, and speed compensation are cancelled according to the release slope that does not exceed the loading slope.

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