Industrial control system and method for a flexible variable pitch conveyor

Abstract

The present application relates to the technical field of industrial control, in particular to an industrial control system and method for a flexible variable-pitch conveyor, comprising: obtaining product specifications, target pitch and conveying tempo issued by an upper computer, and rotor position and adjacent rotor position fed back by an encoder; generating a variable-pitch trajectory containing target position, target speed and target acceleration; collecting driver current and converting it into driving force; time-synchronizing and filtering the driving force, rotor speed and target acceleration; correcting equivalent mass and friction parameters in the free variable-pitch stage without contact; calculating inertial thrust and friction thrust according to the equivalent mass, target acceleration and friction parameters, and deducting the driving force to obtain an external contact force estimate; determining the risk level based on the comparison result of the external contact force estimate and a pre-warning threshold and a safety threshold, and adjusting the subsequent variable-pitch trajectory; the present application realizes indirect contact trend judgment and subsequent trajectory correction for products.

Description

Technical Field

[0001] This invention relates to the field of industrial control technology, specifically to an industrial control system and method for flexible variable pitch conveyors. Background Technology

[0002] Currently, flexible variable pitch conveyor control usually needs to simultaneously handle position control, parameter identification, and risk assessment during the process of compressing or widening product spacing. Since the drive current, encoder feedback, and trajectory commands often come from different sampling references, and the product contact trend will be superimposed on the normal drive response, if there is a lack of a unified data synchronization, parameter freezing, and threshold judgment mechanism, problems such as estimation deviation, misjudgment of contact risk, and instability of subsequent trajectory adjustment can easily occur during the pitch change process. Summary of the Invention

[0003] The main objective of this invention is to propose an industrial control system and method for flexible variable pitch conveyors, which combines a unified data synchronization, parameter freezing, and threshold determination mechanism to accurately assess contact risks and stably adjust subsequent variable pitch trajectories during flexible variable pitch conveyor control, thereby effectively avoiding estimation deviations and misjudgments during the variable pitch process.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] An industrial control system for flexible variable pitch conveyors, applied to flexible variable pitch conveyors containing a driver, a mover connected to the driver, and an encoder, including:

[0006] The trajectory generation module is used to generate a variable pitch trajectory based on the product specifications, target pitch and conveying cycle time sent by the host computer, combined with the position of the mover and adjacent movers, and output the target position, target velocity and target acceleration.

[0007] The position control module communicates with the encoder to obtain the position and velocity of the mover fed back by the encoder, and determines the position error by combining the target position.

[0008] The current acquisition module is used to acquire the current of the driver and convert it into driving force according to the driver thrust constant;

[0009] The thrust calculation module is used to determine the inertial thrust based on the equivalent mass and target acceleration, and the friction thrust based on the friction parameters and the velocity of the mover.

[0010] The signal processing module is used for time synchronization and filtering of the driving force, the velocity of the mover, and the target acceleration.

[0011] The parameter correction module is used to correct the equivalent mass and friction parameters based on the synchronized driving force, target acceleration and friction thrust during the non-contact free pitch change phase.

[0012] The contact force calculation module is used to subtract the inertial thrust and frictional thrust from the driving force to obtain an estimated value of the external contact force.

[0013] The risk assessment module is used to determine the risk level based on the comparison results between the estimated external contact force and the warning threshold and safety threshold.

[0014] The trajectory adjustment module is used to output instructions based on the risk level to adjust the subsequent variable-pitch trajectory;

[0015] The status control module is used to control the execution and switching of each module according to the trajectory generation stage, free pitch stage, contact monitoring stage and protection stage.

[0016] In one alternative, the current acquisition module acquires the current according to a sampling period corresponding to the position, velocity, and target acceleration fed back by the encoder;

[0017] The signal processing module is also used to perform low-pass filtering on the converted driving force, mover velocity, and target acceleration.

[0018] In one alternative, when the estimated external contact force value is continuously less than or equal to a preset identification threshold, the target acceleration is greater than or equal to a preset acceleration threshold, and the current of the driver is not saturated, the parameter correction module corrects the equivalent mass based on the ratio of the result of the driving force minus the friction thrust to the target acceleration.

[0019] The identification error is determined by the difference between the driving force of the current cycle and the driving force calculated based on the equivalent mass, target acceleration and friction thrust. When the identification error exceeds the preset error threshold, the equivalent mass exceeds the preset mass range or the state control module enters the contact monitoring stage, the update stops and the last valid parameter determined when the update conditions were met is retained.

[0020] In one alternative, the risk assessment module filters the estimated external contact force and determines the risk level based on the filtered estimated external contact force and preset warning thresholds and safety thresholds. The risk level includes warning status and over-limit protection status.

[0021] The trajectory adjustment module reduces the subsequent acceleration or speed limit in the warning state, and executes at least one of the deceleration trajectory, buffer trajectory or rollback trajectory according to the preset protection strategy in the over-limit protection state.

[0022] When in contact monitoring and over-limit protection mode, the status control module stops updating and maintains the previous valid parameters of equivalent mass and friction parameters; when communication interruption, data out-of-bounds, or sampling failure occurs, the output signal is in an abnormal state.

[0023] An industrial control method for flexible variable pitch conveyors, applied to flexible variable pitch conveyors including a driver, a mover connected to the driver, and an encoder, comprising:

[0024] Obtain the product specifications, current product spacing, target pitch, conveying cycle time, and the position of the mover and the position of the mover adjacent to the mover from the host computer.

[0025] Verify the communication status of the encoder, current acquisition link, and driver;

[0026] Based on the verification results, current product spacing, target pitch, and conveying cycle time, determine the variable pitch transition trajectory and output the target position, target speed, and target acceleration;

[0027] Based on the target position and the position feedback from the encoder, position closed-loop control is performed to control the driver to drive the actuator.

[0028] The current of the driver is collected and converted into driving force based on the driver thrust constant;

[0029] Time synchronization and filtering are performed on the driving force, the velocity of the mover and the target acceleration to obtain the synchronized driving force, the velocity of the mover and the target acceleration.

[0030] During the non-contact free pitch phase, the equivalent mass and friction parameters are corrected based on the synchronized driving force, target acceleration, and friction thrust.

[0031] When the current product spacing is reduced to the preset contact monitoring area, the estimated value of the external contact force is obtained by subtracting the inertial thrust determined according to the equivalent mass and target acceleration, and the frictional thrust determined according to the friction parameters and the velocity of the mover from the synchronized driving force.

[0032] The risk level is determined by comparing the estimated external contact force with the warning threshold and the safety threshold, and the subsequent variable pitch trajectory is adjusted according to the risk level.

[0033] In one alternative approach, the steps of acquiring the driver's current and converting it into driving force, as well as synchronous filtering, include:

[0034] The current is collected according to the sampling period corresponding to the position and target acceleration fed back by the encoder;

[0035] The current is converted into driving force based on the driver thrust constant;

[0036] The converted driving force, mover velocity, and target acceleration are time-synchronized and low-pass filtered to obtain the synchronized driving force, mover velocity, and target acceleration.

[0037] In one alternative approach, the steps for correcting the equivalent mass and friction parameters during the non-contact free-torsion phase include:

[0038] When the estimated external contact force is continuously less than or equal to the preset identification threshold within a preset time period, the target acceleration is greater than or equal to the preset acceleration threshold, and the current of the driver is not saturated, the equivalent mass is corrected based on the ratio of the result of the synchronized driving force minus the frictional thrust to the target acceleration.

[0039] The identification error is determined by the difference between the driving force after the current cycle synchronization and the driving force calculated based on the equivalent mass, target acceleration and friction thrust. When the identification error exceeds the preset error threshold, the equivalent mass exceeds the preset mass range or enters the contact monitoring zone, the correction is stopped and the previous valid parameter determined when the update conditions were most recently met is retained.

[0040] The sign of the friction thrust is determined by the direction of the mover's velocity, and the magnitude of the friction thrust is determined by the magnitude of the velocity, thus determining the friction thrust.

[0041] In one alternative approach, the step of obtaining an estimate of the external contact force within the contact monitoring zone includes:

[0042] The estimated external contact force is determined based on the synchronized driving force, equivalent mass, target acceleration, frictional thrust, and pre-calibrated compensation terms used to compensate for the zero bias of the driver or the steady-state error of the model.

[0043] The risk status is determined based on the filtered external contact force estimate, its duration, and rate of change, combined with pre-set warning thresholds, safety thresholds, and recovery thresholds.

[0044] When the filtered external contact force estimate is greater than or equal to the warning threshold and less than the safety threshold, and remains greater than or equal to the preset warning time, a warning status is output; when the filtered external contact force estimate is greater than or equal to the safety threshold, or the rate of change of the filtered external contact force estimate is greater than or equal to the preset sudden change threshold, an over-limit protection status is output.

[0045] In one alternative approach, the steps for adjusting subsequent pitch trajectories based on risk levels include: continuing to execute the current pitch trajectories under normal conditions;

[0046] In a warning state, reduce the subsequent acceleration or speed limit and extend the pitch change time;

[0047] When the product spacing is reduced further under the over-limit protection state, at least one of the following is executed according to the preset protection strategy: deceleration trajectory, buffer trajectory, or retraction trajectory.

[0048] In the event of an abnormal signal, updates will be stopped and the previous valid parameters of the equivalent mass and friction parameters will be retained. If the conditions for closed-loop operation are still met, the operation trajectory at the preset safe speed will be executed; otherwise, the machine will be stopped. The abnormal signal state is triggered by communication interruption or data out of bounds.

[0049] When the variable pitch task is completed, the contact risk is eliminated, and the signal is valid, update the equivalent mass and friction parameters that have passed the identification error and range constraint verification. Otherwise, retain the previous valid parameters and record the risk data, which includes at least the estimated external contact force, risk level, and trigger time.

[0050] The beneficial effects of this invention are:

[0051] 1. This invention continuously acquires the position and speed feedback from the encoder through the position control module, and generates a variable pitch trajectory by the trajectory generation module in conjunction with the product specifications, target pitch, and conveying cycle time issued by the host computer. This enables the mover to operate according to uniform trajectory parameters within the same control cycle, thereby improving the consistency of position control in the flexible variable pitch process and providing a stable basis for subsequent parameter identification and risk assessment. The current acquisition module acquires the current according to the sampling period corresponding to the encoder feedback data and target acceleration data, and the signal processing module performs time synchronization and filtering processing on the driving force, mover speed, and target acceleration. This can eliminate the conversion deviation caused by different sampling references, suppress high-frequency fluctuations and spike interference, thereby improving the stability and accuracy of contact force estimation.

[0052] 2. This invention uses a parameter correction module to correct the equivalent mass and friction parameters during the contactless free pitch transition phase based on the synchronized driving force, target acceleration, and friction thrust. Parameters are only updated when the estimated external contact force is consistently below a preset identification threshold, the target acceleration is greater than a preset acceleration threshold, and the driver current is not saturated. This ensures the identification process remains within usable operating conditions, preventing contamination of parameter results by contact trends, zero-speed jitter, or current saturation, thereby improving the reliability of the equivalent mass and friction parameters. By stopping updates and maintaining the previous valid parameters when identification errors exceed limits, equivalent mass exceeds the range, or contact monitoring is initiated, abnormal cycles cannot directly rewrite valid parameters, ensuring that subsequent thrust calculations and contact force estimations always operate based on stable parameters.

[0053] 3. This invention obtains an estimated external contact force by subtracting inertial thrust and frictional thrust from the synchronized driving force through a contact force calculation module. The risk assessment module then determines the risk level by combining the warning threshold, safety threshold, and the filtered estimated value. This allows for continuous monitoring of product contact trends without the need for additional physical force sensors, thereby identifying warning states and over-limit protection states in advance and reducing the risk of product compression or collision. The trajectory adjustment module performs acceleration limiting, speed limiting, deceleration, buffering, or reversal processing on subsequent pitch-changing trajectories based on the risk level. This directly converts the risk assessment results into executable subsequent trajectory correction actions, thereby reducing the continuous deterioration of contact risk and improving the controllability of the pitch-changing process. Attached Figure Description

[0054] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0055] Figure 1 This is a module architecture diagram of the industrial control system of the flexible variable pitch conveyor in the embodiments of this application;

[0056] Figure 2 This is a flowchart of an industrial control method for a flexible variable-pitch conveyor according to an embodiment of the present invention. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] Please see Figure 1 An industrial control system for flexible variable pitch conveyors, applied to flexible variable pitch conveyors containing a driver, a mover connected to the driver, and an encoder, including:

[0059] The trajectory generation module is used to generate a variable pitch trajectory based on the product specifications, target pitch and conveying cycle time issued by the host computer, combined with the position of the mover and adjacent movers, and output the target position, target speed and target acceleration.

[0060] The position control module communicates with the encoder to obtain the position and velocity of the mover fed back by the encoder, and determines the position error by combining the target position.

[0061] The current acquisition module is used to acquire the current of the driver and convert it into driving force according to the driver thrust constant;

[0062] The thrust calculation module is used to determine the inertial thrust based on the equivalent mass and target acceleration, and the friction thrust based on the friction parameters and the velocity of the mover.

[0063] The signal processing module is used for time synchronization and filtering of the driving force, the velocity of the mover, and the target acceleration.

[0064] The parameter correction module is used to correct the equivalent mass and friction parameters based on the synchronized driving force, target acceleration and friction thrust during the non-contact free pitch change phase.

[0065] The contact force calculation module is used to subtract the inertial thrust and frictional thrust from the driving force to obtain an estimated value of the external contact force.

[0066] The risk assessment module is used to determine the risk level based on the comparison results between the estimated external contact force and the warning threshold and safety threshold.

[0067] The trajectory adjustment module is used to output instructions based on the risk level to adjust the subsequent variable-pitch trajectory;

[0068] The status control module is used to control the execution and switching of each module according to the trajectory generation stage, free pitch stage, contact monitoring stage and protection stage;

[0069] In some possible implementations, the current acquisition module acquires the current according to a sampling period corresponding to the position, velocity, and target acceleration fed back by the encoder;

[0070] The signal processing module is also used to perform low-pass filtering on the converted driving force, mover velocity and target acceleration;

[0071] When the estimated external contact force value is continuously less than or equal to the preset identification threshold within a preset time period, the target acceleration is greater than or equal to the preset acceleration threshold, and the current of the driver is not saturated, the parameter correction module corrects the equivalent mass based on the ratio of the result of the driving force minus the friction thrust to the target acceleration.

[0072] The identification error is determined by the difference between the driving force of the current cycle and the driving force calculated based on the equivalent mass, target acceleration and friction thrust. When the identification error exceeds the preset error threshold, the equivalent mass exceeds the preset mass range or the state control module enters the contact monitoring stage, the update stops and the last valid parameter determined when the update conditions were met is retained.

[0073] The flexible variable pitch conveyor sequentially transports hoses, plastic bottles, or cosmetic packaging along a predetermined conveying direction. Adjacent moving parts carry the corresponding products and adjust the pitch according to the target pitch before entering the subsequent workstation.

[0074] This embodiment provides a method for judging contact trends and correcting trajectories without physical force sensors: based on driver current, encoder feedback and pre-generated variable pitch trajectories, the contact trends between products are judged, and the subsequent running trajectory is corrected before contact risks are formed;

[0075] During system operation, the position control module continuously receives the position and speed of the mover returned by the encoder; the trajectory generation module receives the product specifications, target pitch and conveying cycle corresponding to the current task from the host computer, and generates the variable pitch trajectory for this cycle by combining the current position of the mover and the positional relationship of adjacent movers.

[0076] The trajectory contains the target position, target velocity, and target acceleration, which are handed over to the position control module for driver control and to the state control module as the basis for stage switching. The position control module compares the target position with the encoder feedback position to obtain the position error, which is used to ensure that the mover runs according to the generated trajectory.

[0077] When the mover enters the pitch control task, the current acquisition module reads the driver current according to the driver control cycle and converts it into driving force based on the driver thrust constant.

[0078] To avoid inconsistencies in sampling references between data from different sources, the signal processing module aligns the driving force, mover velocity, and target acceleration output from the trajectory generation module to the same system period before filtering. The processed signals are then provided to the parameter correction module, thrust calculation module, and contact force calculation module, respectively, so that subsequent calculations no longer directly depend on the original sampled values.

[0079] During the free pitch change phase, the state control module maintains a non-contact status indicator based on the product spacing, the positional relationship of adjacent movers, and the current running progress; during this phase, the parameter correction module calls the synchronized driving force, target acceleration, and current friction thrust to update the equivalent mass and friction parameters.

[0080] The equivalent mass is used to characterize the comprehensive load characteristics of the mover and its load-bearing products under the current mission, and the friction parameters are used to characterize the frictional effects during operation; the updated parameters are written into the current valid parameter area for direct use by the subsequent thrust calculation module.

[0081] Once contact monitoring is initiated, the status control module stops the parameter correction module from updating and retains the most recent valid parameters to avoid mistakenly writing the additional thrust caused by contact between products into the equivalent mass or friction parameters.

[0082] The thrust calculation module reads the currently effective equivalent mass, the synchronized target acceleration, and the mover velocity, and calculates the inertial thrust and frictional thrust respectively; the contact force calculation module then uses the synchronized driving force as a basis, subtracts the inertial thrust and frictional thrust, and obtains the estimated value of the external contact force.

[0083] The estimated value is sent to the risk assessment module and compared with the warning threshold and the safety threshold. When the estimated value does not reach the warning threshold, the system maintains the current variable pitch trajectory. When the estimated value reaches the warning threshold but does not exceed the safety threshold, the risk assessment module outputs the warning level. When the estimated value exceeds the safety threshold, the protection level is output.

[0084] After receiving the risk level, the trajectory adjustment module adjusts the subsequent variable pitch trajectory that has not yet been executed. The adjustment may include lowering the upper limit of subsequent acceleration, lowering the upper limit of velocity, or changing the propulsion method of subsequent compression pitch. The adjustment result is returned to the trajectory generation module to generate new target position, target velocity, and target acceleration.

[0085] The state control module is used to switch between the trajectory generation stage, the free pitch stage, and the contact monitoring and protection stage; the trajectory generation stage mainly completes the task parameter reception and initial trajectory generation; the free pitch stage mainly allows for the correction of equivalent mass and friction parameters;

[0086] Contact monitoring mainly performs contact force estimation and risk assessment; the protection phase mainly performs trajectory adjustment results triggered by risk level; the original sampling data is not directly written back between each phase, but is connected through the current effective parameters, current risk level and current trajectory parameters, so as to ensure that each module processes the same set of data in the same cycle;

[0087] If encoder feedback, driver current, or adjacent mover position information cannot be obtained normally in the current system cycle, the state control module can maintain the trajectory stage confirmed in the previous valid cycle and suspend the writing of new parameter corrections, retaining only the equivalent mass and friction parameters determined before the current cycle to ensure the continuity of current position control and subsequent risk assessment; after obtaining valid data again in subsequent cycles, the normal calculation process will resume.

[0088] In this embodiment, the consistency of the sampling period is used to solve the conversion error problem when the driver current, encoder feedback speed and target acceleration source are not synchronized. If the values ​​are taken separately according to the default cycle of each interface, misalignment may occur between the driving force and speed and acceleration under high dynamic variable pitch conditions, affecting the contact force estimation.

[0089] Therefore, the current acquisition module acquires the current according to the sampling period corresponding to the encoder feedback data and the target acceleration data, and the signal processing module further performs low-pass filtering on the converted driving force, mover speed and target acceleration.

[0090] After this processing, the high-frequency fluctuations in the driving force and the spikes in velocity and acceleration are suppressed, and the subsequent thrust and contact force calculations are based on stable data under the same period.

[0091] In this embodiment, the update conditions are used to limit parameter correction to occur only under identifiable working conditions; if the estimated value of the external contact force during the free pitch stage remains below the preset identification threshold for a preset duration, it indicates that no contact requiring protection has been formed between the products.

[0092] If the target acceleration is greater than the preset acceleration threshold, it indicates that the current trajectory provides sufficient excitation for equivalent mass identification; if the driver current is not saturated, it indicates that the current sampling is still within the effective conversion range.

[0093] When the above conditions are met, the parameter correction module corrects the equivalent mass based on the ratio of the result of the driving force minus the friction thrust to the target acceleration, and simultaneously maintains the friction parameters corresponding to the mass.

[0094] Considering that short-term outliers may occur during high-cycle operation, simply allowing updates cannot guarantee that the parameters will always be valid; therefore, this implementation further limits the circumstances under which updates are stopped.

[0095] When the calculation results used for parameter correction exceed the preset error threshold, it indicates that the conversion relationship of the current cycle is no longer suitable for updating; when the equivalent quality exceeds the preset quality range, it indicates that the current estimation result deviates from the reasonable range of equipment and product combination.

[0096] When the status control module has switched to contact monitoring, it indicates that the system has entered the operating range where contact judgment is the primary function. In these cases, the parameter correction module stops updating and retains the last valid parameter determined when the update conditions were most recently met.

[0097] After this processing, the contact force calculation module still uses the filtered valid parameters in subsequent stages, rather than temporary results affected by contact or abnormal sampling.

[0098] To ensure that the friction parameter correction process has a definite data source and execution order, when the update conditions are met, the parameter correction module first adopts a unified symbol convention for the synchronized driving force, inertial thrust, and friction thrust according to the positive and negative directions of the mover velocity, and then uses the remaining thrust after deducting the inertial thrust from the driving force as the friction identification input.

[0099] Within the same speed direction and the same speed range, the parameter correction module averages the remaining thrust in the preset continuous sampling window and determines the average result as the friction thrust amplitude of the corresponding speed range; when the speed direction changes, friction parameters corresponding to forward and reverse operation are established respectively.

[0100] For sampling points whose absolute velocity value is lower than the preset minimum velocity threshold, they are not used for updating new friction parameters. Instead, the previous effective friction parameters are retained to avoid directional jitter near zero velocity affecting the identification results.

[0101] The friction parameter update must also meet the following conditions: the identification error does not exceed the preset error threshold, the friction thrust amplitude is within the preset friction parameter range, and the state control module is still in the free pitch stage.

[0102] If any condition is not met, only the friction parameters that were most recently met are retained. Thus, the equivalent mass is corrected according to the ratio of the driving force minus the friction thrust to the target acceleration, and the friction parameters are corrected according to the average result of the remaining thrust window in different velocity directions and velocity ranges. The input, update conditions and retention rules of both correspond to each other, and they all stop updating after entering contact monitoring.

[0103] In some possible implementations, the risk assessment module filters the external contact force estimate and determines the risk level based on the filtered external contact force estimate and preset warning thresholds and safety thresholds. The risk level includes warning status and over-limit protection status.

[0104] The trajectory adjustment module reduces the subsequent acceleration or speed limit in the warning state, and executes at least one of the deceleration trajectory, buffer trajectory or rollback trajectory according to the preset protection strategy in the over-limit protection state.

[0105] When in contact monitoring and over-limit protection mode, the status control module stops updating and maintains the previous valid parameters of equivalent mass and friction parameters; when communication interruption, data out-of-bounds, or sampling loss occurs, the output signal is in an abnormal state.

[0106] Please see Figure 2 An industrial control method for flexible variable pitch conveyors, applied to flexible variable pitch conveyors including a driver, a mover connected to the driver, and an encoder, comprising:

[0107] Obtain the product specifications, current product spacing, target pitch, conveying cycle time, and the position of the mover and the position of the mover adjacent to the mover from the host computer.

[0108] Verify the communication status of the encoder, current acquisition link, and driver;

[0109] Based on the verification results, current product spacing, target pitch, and conveying cycle time, determine the variable pitch transition trajectory and output the target position, target speed, and target acceleration;

[0110] Based on the target position and the position feedback from the encoder, position closed-loop control is performed to control the driver to drive the actuator.

[0111] The current of the driver is collected and converted into driving force based on the driver thrust constant;

[0112] Time synchronization and filtering are performed on the driving force, the velocity of the mover and the target acceleration to obtain the synchronized driving force, the velocity of the mover and the target acceleration.

[0113] During the non-contact free pitch phase, the equivalent mass and friction parameters are corrected based on the synchronized driving force, target acceleration, and friction thrust.

[0114] When the current product spacing is reduced to the preset contact monitoring area, the estimated value of the external contact force is obtained by subtracting the inertial thrust determined according to the equivalent mass and target acceleration, and the frictional thrust determined according to the friction parameters and the velocity of the mover from the synchronized driving force.

[0115] The risk level is determined by comparing the estimated external contact force with the warning threshold and the safety threshold, and the subsequent variable pitch trajectory is adjusted according to the risk level.

[0116] The steps of acquiring the driver current and converting it into driving force, as well as synchronous filtering, include:

[0117] The current is collected according to the sampling period corresponding to the position and target acceleration fed back by the encoder;

[0118] The current is converted into driving force based on the driver thrust constant;

[0119] The converted driving force, mover velocity, and target acceleration are time-synchronized and low-pass filtered to obtain the synchronized driving force, mover velocity, and target acceleration.

[0120] Flexible variable pitch conveyors undertake the transfer task between multiple packaging stations in the same production line. The output cycle frequency of the previous station is greater than the first preset threshold, and the receiving cycle frequency of the next station is less than the second preset threshold. Therefore, it is necessary to continuously compress or widen the product spacing during the conveying process.

[0121] This embodiment discloses a control method for matching risk status with trajectory processing actions, and further describes the corresponding industrial control method;

[0122] In this method, the system first receives the product specifications, current product spacing, target pitch and conveying cycle from the host computer, and at the same time reads the position of the mover fed back by the encoder and the position of the adjacent mover.

[0123] Based on this data, the system first determines whether the current task has the basic conditions to enter variable pitch control; the verification process covers the communication status of the encoder, current acquisition link and driver. Only when the above links are in a valid state will the variable pitch transition trajectory be generated based on the current product spacing, target pitch and conveying cycle time.

[0124] The variable pitch transition trajectory refers to the subsequent running trajectory that gradually transitions from the current product pitch to the target pitch. It corresponds to the target position, target velocity and target acceleration sequence that will be executed sequentially in multiple subsequent control cycles, rather than just the target value at a single moment.

[0125] The generated target position, target velocity, and target acceleration are sent to the driver side as control quantities for this cycle and are stored in the current task record for continuous use in subsequent cycles.

[0126] To ensure a defined implementation path for the trajectory generation process, the preferred method is to first calculate the pitch difference between the current product spacing and the target pitch, then calculate the total number of cycles allowed for this pitch-changing task based on the conveying cycle time. Starting from the current position and ending at the positional relationship corresponding to the target pitch, a trapezoidal velocity curve planning algorithm is used to generate the target position, target velocity, and target acceleration sequence for subsequent cycles in the order of remaining displacement, current velocity, and upper limit of allowable acceleration. During the uniform acceleration phase, the target velocity for the next cycle is calculated using the formula:

[0127]

[0128] The target location is determined by the formula:

[0129]

[0130] in, Number the system control cycle. The target speed for the next cycle, The target speed for the current cycle, To allow for a maximum acceleration, The target position for the next cycle. The target position for the current period. This refers to the duration of the system control cycle;

[0131] When the position of an adjacent mover is updated, only the remaining trajectory sequence that has not yet been executed is recalculated, while the target value already issued in the current cycle remains unchanged. This makes the determination of the variable pitch transition trajectory based on the current product spacing, target pitch and conveying cycle time no longer just a result description.

[0132] During the operation of the mover, the position control drives the driver to execute the trajectory according to the deviation between the target position and the encoder feedback position; at the same time, the system continuously collects the driver current and converts it into driving force, and then unifies the driving force with the mover speed and target acceleration into the same system cycle for synchronization and filtering.

[0133] The processed data enters the subsequent calculation link to determine whether it is still in the non-contact free-range stage or has entered the monitoring area where product contact needs to be closely monitored.

[0134] The current product spacing can be determined by the difference between the position of this mover and the position of the adjacent mover, combined with the preset reference zero position direction; when the spacing is greater than the upper boundary of the preset monitoring interval, the system determines that it is still in the free pitch stage.

[0135] When the distance enters the preset monitoring range, the system switches to the processing flow corresponding to the contact monitoring area, so that the stage switching basis is consistent with the current product distance, the position of adjacent moving parts and the contact monitoring area.

[0136] In this embodiment, the terms "contact monitoring zone," "contact monitoring," and "preset monitoring zone" have the same meaning; they all refer to the zone where the product spacing is reduced to the point where external contact force estimation and risk assessment are required.

[0137] The over-limit protection status corresponds to the status output of the status control module after entering the protection phase, and is used to distinguish it from the warning status and the signal abnormal status.

[0138] The preset monitoring interval can be set based on the minimum allowable distance corresponding to the target pitch and the current product specification: when the theoretical distance between adjacent products is greater than the minimum allowable distance plus the preset monitoring margin, it is determined to be the free pitch stage;

[0139] When the theoretical distance between adjacent products is less than or equal to the minimum allowable distance plus the preset monitoring margin, and greater than or equal to the minimum allowable distance minus the preset recovery margin, it is determined that the product has entered the preset monitoring range.

[0140] Among them, the preset monitoring margin is preferably selected at 5% to 15% of the target pitch, and the preset recovery margin is preferably smaller than the preset monitoring margin, so that there are different boundaries when switching and exiting the stage, reducing repeated switching at the edge of the interval.

[0141] If the system confirms that it is still in the non-contact free pitch stage, it will correct the equivalent mass and friction parameters according to the saved friction thrust. If the product spacing has been reduced to the preset monitoring range, the system will no longer write new equivalent mass and friction parameters, but will directly call the most recent effective parameters, and calculate the estimated value of external contact force based on the synchronized driving force minus the inertial thrust and friction thrust.

[0142] This estimated value is compared with the warning threshold and the safety threshold to determine the current risk level. Once the risk level is determined, the unexecuted portion of the variable-distance trajectory will be reprocessed according to that level: if it is in a normal state, it will continue to be executed according to the original trajectory.

[0143] When in a warning state, the upper limit of subsequent acceleration or speed is lowered; when in an over-limit protection state, at least one of a deceleration trajectory, a buffer trajectory, or a reversal trajectory is executed on the remaining trajectory to stop further reducing the product spacing or reduce the established contact trend.

[0144] To make the state switching conditions clearer, the warning state corresponds to the situation where the filtered external contact force estimate reaches the warning threshold and continues to meet the preset time, and the over-limit protection state corresponds to the situation where the filtered external contact force estimate exceeds the safety threshold, or although it does not exceed the safety threshold, the rise rate reaches the preset change criterion within a continuous system cycle.

[0145] When the filtered external contact force estimate falls back to the range corresponding to the recovery criterion and continues to meet the preset time, the system will lift the warning state or over-limit protection state and continue to run according to the adjusted subsequent trajectory.

[0146] The aforementioned warning threshold, safety threshold, recovery criterion, and mutation criterion can be set jointly according to the allowable contact capacity and conveying cycle time corresponding to the current product specifications. The warning threshold is less than the safety threshold, and the recovery threshold corresponding to the recovery criterion is less than the warning threshold.

[0147] For the same product specification, the safety threshold can be calculated first based on the allowable static contact load or allowable deformation, and then the warning threshold can be set to 60% to 90% of the safety threshold, and the recovery threshold can be set to 70% to 95% of the warning threshold.

[0148] When the rigidity of the product material is lower than the preset rigidity threshold or there is a risk of surface damage, the preset lower limit ratio is taken first; when the rigidity of the product is greater than or equal to the preset rigidity threshold and the cycle frequency is lower than the preset frequency threshold, the preset upper limit ratio is taken first; the change rate threshold corresponding to the mutation criterion can be set according to the ratio of the equivalent growth amount of the safety threshold in 3 to 10 system cycles to the corresponding duration, so as to trigger protection in advance when the change rate is greater than or equal to the preset change rate threshold but the absolute value has not yet reached the safety threshold;

[0149] The selection of the above-mentioned proportional ranges is based on the following: setting the warning threshold and recovery threshold proportionally to the safety threshold ensures that a margin matching the product's permissible contact capability is maintained between the warning trigger point and the safety trigger point; when the warning threshold is lower than 60% of the safety threshold, the driving force fluctuation during normal pitch change is easily misjudged as a contact trend; when the warning threshold is higher than 90% of the safety threshold, the warning trigger is delayed, and the reserved trajectory convergence time is insufficient; the recovery threshold is set to 70% to 95% of the warning threshold to form a hysteresis interval between the warning entry and cancellation, avoiding repeated switching of risk status when the estimated value fluctuates near the warning threshold; the above ranges have been verified through equipment debugging under different product specifications, and can retain sufficient trajectory adjustment time without increasing the misjudgment rate;

[0150] To make the correspondence between the risk assessment module and the trajectory adjustment module clearer, the risk assessment can be performed in a fixed order: first, read the filtered external contact force estimate for the current cycle, then compare it with the safety threshold; if it is greater than the safety threshold, directly output the over-limit protection status.

[0151] If it is not greater than the safety threshold, it continues to be compared with the warning threshold. Only when the cumulative number of consecutive cycles reaching the warning threshold is not less than the number of cycles corresponding to the preset warning time will the warning status be output.

[0152] If neither of the above two conditions is met at the same time, the normal state is maintained. For the over-limit protection state triggered by the rate of change, it is preferable to determine the difference between the filtered external contact force estimates of two adjacent system cycles by the system cycle duration. When the system cycle is fixed, the difference between the filtered external contact force estimates of two adjacent system cycles can also be directly compared with the preset sudden change threshold.

[0153] After receiving the risk status, the trajectory adjustment module performs trajectory processing according to the pre-stored status correspondence table. The normal status corresponds to the original trajectory identifier, the warning status corresponds to the acceleration limit identifier or speed limit identifier, and the over-limit protection status corresponds to the deceleration identifier, buffer identifier or back off identifier. This makes the mapping relationship from risk status to trajectory action have definite inputs and outputs in the control flow.

[0154] Furthermore, to avoid timing conflicts between lowering the upper limit of subsequent acceleration and extending the pitch change time, the trajectory adjustment module preferably recalculates only the remaining trajectory sequence for the next system cycle and thereafter, while keeping the target value already issued in the current system cycle unchanged.

[0155] For the same remaining trajectory sequence, it is preferable to first determine a new upper limit of acceleration or upper limit of velocity, and then recalculate the corresponding target velocity, target position and remaining pitch time in this order, so that only one set of recalculated trajectory parameters is used in the position closed-loop control within the same cycle.

[0156] Furthermore, the pre-stored state correspondence table preferably includes at least five fields: state identifier, acceleration upper limit adjustment ratio, speed upper limit adjustment ratio, trajectory processing type, and execution duration period number; wherein, the acceleration upper limit adjustment ratio and speed upper limit adjustment ratio corresponding to the normal state are both zero, the trajectory processing type is original trajectory maintenance, and the execution duration period number is the current remaining trajectory period number;

[0157] The acceleration limit adjustment ratio corresponding to the warning state is preferably a preset value between 10% and 30%, or the speed limit adjustment ratio is preferably a preset value between 5% and 20%. The trajectory processing type is acceleration limit or speed limit, and the execution duration period is the number of periods corresponding to the remaining trajectory after recalculation.

[0158] The trajectory processing type corresponding to the over-limit protection state is deceleration, buffering, or rollback, and the execution duration is the number of cycles corresponding to the protection strategy. After receiving the risk state, the trajectory adjustment module executes in the following order first: read the remaining displacement, current speed, and current risk state at the end of the current cycle.

[0159] Then, look up the acceleration upper limit adjustment ratio, velocity upper limit adjustment ratio, and trajectory processing type corresponding to the current state from the state correspondence table; only the remaining trajectory sequence of the next system cycle and thereafter is recalculated, and the recalculation result is written to the trajectory buffer of the subsequent cycle;

[0160] If the trajectory processing type is limited acceleration, the new acceleration upper limit is obtained by multiplying the original planned acceleration upper limit by the corresponding adjustment coefficient, and then the subsequent target velocity, target position and remaining pitch time are recalculated in sequence under the new acceleration upper limit.

[0161] If the trajectory processing type is speed-limited, the new speed limit is obtained by multiplying the original planned speed limit by the corresponding adjustment coefficient, and then the subsequent target position and remaining drift time are recalculated under this new speed limit; the calculation formula for the target speed sequence is:

[0162]

[0163] in, Number the system control cycle. For the target speed of the next cycle, For the current cycle speed, For a constant deceleration, This refers to the duration of the system control cycle;

[0164] The target position is recalculated based on the kinematic integral; if the trajectory processing type is buffered, the formula for calculating the target acceleration step size is:

[0165]

[0166] in, Number the system control cycle. For the target acceleration step size, Accelerate the target for the current cycle. The preset buffer cycle number is used; the recalculation formula for the target position is:

[0167]

[0168] in, Number the system control cycle. The target position for the next cycle. , , These represent the target position, velocity, and acceleration for the current cycle. This refers to the duration of the system control cycle;

[0169] If the trajectory processing type is backtracking, it is preferable to first freeze the target displacement component that continues to shrink the product spacing, and then increase the target position by a preset backtracking displacement in the opposite direction to the current compression direction.

[0170] The preset backoff displacement is preferably 10% to 50% of the current remaining compression displacement, and does not exceed 20% of the target pitch; after this processing, a definite data flow relationship is formed between the risk status, the status correspondence table and the subsequent trajectory recalculation, and the trajectory adjustment is no longer just a functional description;

[0171] After this processing, the time sequence of risk assessment output, trajectory adjustment execution and driver receiving control quantities remains consistent, avoiding the simultaneous use of two sets of trajectory parameters before and after adjustment within the same system cycle; in order to avoid cross-cycle mixing of driving force, speed and target acceleration in cache attribution, in this embodiment, all data are assigned a unique identifier based on the same system control cycle number.

[0172] Only after obtaining the driver current, encoder feedback speed and target acceleration simultaneously under the same cycle number will the set of data be sent as valid input to the subsequent conversion and filtering link;

[0173] If a piece of data arrives after the end time of the current cycle, it is assigned to its corresponding cycle and is not written back to the previous cycle that has ended. This means that time synchronization corresponds to the alignment of data within the same control cycle, rather than requiring physical sampling to be completely overlapping at an instant.

[0174] Furthermore, in order to control the flow order when multi-cycle trajectory recalculation and synchronous calculation occur in parallel, the system preferably marks the target sequence participating in position closed-loop control in the current cycle as the execution state, and marks the recalculation results of the next system cycle and thereafter as the switching state; the trajectory in the switching state is only allowed to be transferred to the execution state when the current cycle ends and the next cycle begins.

[0175] If a new risk status is received before the state to be switched to the execution state, it is preferable to retain only the set of trajectories with a higher risk level or the same risk level but a later update time, and the remaining ineffective trajectories will not be sent out, thereby avoiding multiple sets of subsequent trajectories corresponding to the same remaining displacement from occupying the control link in parallel.

[0176] Furthermore, when the trajectory adjustment module recalculates the trajectory sequence for the next system cycle and the remaining trajectory sequence thereafter, it preferably generates a target sequence that satisfies continuity only within the range of the current position, current velocity, remaining displacement, and newly set acceleration upper limit or velocity upper limit. This ensures that the recalculated target velocity and target acceleration maintain limited variation at the boundary between adjacent system cycles, avoiding timing mismatch between the driving force conversion value and the trajectory command value due to parameter mutations within a single cycle.

[0177] Further restrictions are placed on risk assessment and protection measures; if threshold comparisons are made directly based on the unprocessed external contact force estimate, transient fluctuations may trigger misjudgments during driver current fluctuations, speed reversals, or trajectory switching.

[0178] Therefore, the risk assessment module first filters the estimated external contact force, and then determines the state based on the filtered result and the preset warning threshold and safety threshold. In the warning state, the trajectory adjustment module lowers the subsequent acceleration limit or speed limit. In the over-limit protection state, at least one of the deceleration trajectory, buffer trajectory or retreat trajectory is executed according to the preset protection strategy.

[0179] The preferred retraction trajectory is one that increases the product spacing in a preset increment in the opposite direction to the current compression direction. The deceleration trajectory and the buffer trajectory are used to reduce the approach speed without immediately reversing the direction. Therefore, the three correspond to different levels of risk handling actions, but all aim to limit the further aggravation of contact.

[0180] After this processing, the risk assessment result does not directly rely on the instantaneous value of a single cycle, but is controlled based on the processed contact force estimate; to avoid the trajectory adjustment remaining only at the level of general description, the subsequent acceleration limit under the warning state is preferably reduced by 10% to 30% based on the current planned value, or the subsequent speed limit is reduced by 5% to 20%, and the remaining pitch change time is extended accordingly by 5% to 25%;

[0181] Under over-limit protection conditions, the deceleration trajectory preferably reduces the speed to 20% to 60% of the current speed within 1 to 5 system cycles; the buffer trajectory preferably transitions the target acceleration to zero or a reverse acceleration less than a preset acceleration threshold cycle by cycle; and the retraction trajectory preferably increases the product spacing along the retraction direction by no more than 5% to 20% of the target pitch.

[0182] For the same risk event, the three protective actions can be selected and executed in the order of deceleration, buffering, and retraction, or in combination. The selection is based on whether the filtered external contact force estimate continues to rise and whether it has exceeded the safety threshold.

[0183] Furthermore, to facilitate the direct generation of executable subsequent trajectories, in the warning state, the trajectory adjustment module prioritizes keeping the target positions issued in the current cycle unchanged, and only lowers the upper limit of target acceleration or target velocity in the remaining trajectory sequence from the next system cycle, and recalculates the remaining trajectory sequence according to the adjusted upper limit;

[0184] Under over-limit protection, the trajectory adjustment module preferably freezes the target displacement component that continues to reduce the product spacing first, and then recalculates the target position, target velocity and target acceleration sequence of the remaining cycle according to the selected deceleration, buffering or backtracking strategy. This ensures that the processing objects of reducing the subsequent acceleration upper limit or velocity upper limit and executing the deceleration trajectory, buffering trajectory or backtracking trajectory fall on the subsequent trajectory sequence itself, rather than remaining at the level of principle description.

[0185] In this implementation, the state control module also handles parameter freezing and abnormal output processing; once the system enters the contact monitoring or over-limit protection state, it stops updating the equivalent mass and friction parameters and continues to maintain the previous effective parameters to ensure the stability of the inertial thrust and friction thrust sources on which subsequent calculations are based.

[0186] If a communication interruption, data out-of-bounds error, or sampling failure occurs during operation, the status control module will output an abnormal signal. Here, data out-of-bounds error means that the encoder feedback position, mover speed, driver current, or the driving force calculated from them exceeds the preset reasonable range.

[0187] Sampling loss refers to the failure to obtain a valid sample value for the corresponding item within the current system cycle. In this case, the parameter update for the current cycle will not continue, but the previous valid parameters and the currently generated protection trajectory will be maintained to avoid the entire variable pitch task calculation link being disconnected due to data interruption in individual cycles.

[0188] If the feedback conditions required for position closed-loop control are still available, the system will maintain controlled operation according to the running trajectory corresponding to the preset safe speed; if the feedback conditions required for position closed-loop control are not available, the system will switch to shutdown processing, so that the control actions and risk handling actions under abnormal signal conditions can be distinguished from each other and are consistent.

[0189] The above-mentioned reasonable range can be limited by the rated parameters of the equipment and the current task parameters. The change in the encoder feedback position shall not exceed the theoretical maximum displacement plus position tolerance within the corresponding system cycle, the mover speed shall not exceed 110% of the rated speed, the driver current shall not exceed the rated continuous current or the preset short-time overload current limit, and the converted driving force shall not exceed the maximum allowable driving force determined by the aforementioned current limit and thrust constant.

[0190] The position tolerance is preferably selected as 5% to 10% of the theoretical displacement of a single cycle or the allowable error of mechanical installation, so that the judgment of data out of bounds has a clear basis; for sampling loss, it is preferred to judge whether the corresponding item has obtained a valid sample value before the end of the current system cycle; if a certain item is missing for a continuous system cycle, the output signal is in an abnormal state and the parameter update of that cycle is stopped. If the valid sampling is restored in subsequent cycles, the corresponding calculation process is restored after re-verification of communication status.

[0191] Furthermore, the control priority under abnormal signal conditions is higher than that under early warning conditions, but lower than that under triggered over-limit protection conditions; when risk triggering and sampling abnormality occur simultaneously within the same cycle, if a protection trajectory has been generated before the current cycle, the protection trajectory will be kept running instead of switching back to the original trajectory.

[0192] If a protection trajectory has not been generated before the current cycle, the system will directly switch to the running trajectory corresponding to the preset safe speed. After this processing, communication interruption, data out-of-bounds and sampling loss can all be judged with directly executable criteria, and there is a clear cascading order between anomaly control and risk control.

[0193] Each step is connected through the current task parameters, the current valid parameters, and the current trajectory parameters; after the trajectory is generated, it is not necessary to request the host computer task parameters again in each subsequent cycle, but to use the target pitch and conveying cycle in the current task record as the basis for continuous calculation.

[0194] The correction results for equivalent mass and friction parameters do not directly cover all historical parameters. Instead, they are first used as the current cycle results in subsequent thrust calculations and then updated to the current effective parameters when the stage conditions are met. With this processing, trajectory control, contact force estimation and risk handling each rely on their own confirmed data, without having to backtrack all the original inputs in each step.

[0195] The method is used to further constrain the current acquisition and synchronous filtering process; if the driver current and encoder feedback speed and target acceleration are not obtained with the same sampling period, the calculated driving force, speed and acceleration may correspond to different system periods, and the external contact force estimation will deviate accordingly.

[0196] Therefore, the current acquisition is performed according to the sampling period corresponding to the encoder feedback data and the target acceleration data, and then converted into driving force based on the driver thrust constant; the converted driving force is synchronized with the mover speed and the target acceleration under the same time reference, and after low-pass filtering, the synchronized driving force, mover speed and target acceleration are formed.

[0197] The synchronized data is then used in the equivalent mass correction and contact force estimation process to ensure that the basic data of each calculation stage is consistent. In order to avoid time synchronization only being described in the results, the following processing order is preferred in this embodiment: First, the system control cycle is used as a unified time reference to record the start time of each system cycle.

[0198] Then, the driver current, encoder feedback speed, and trajectory output target acceleration collected in the current cycle are written into the cycle buffer corresponding to the starting time.

[0199] If a piece of data arrives earlier or later than the current cycle, it is written to the most recent cycle buffer to which it belongs. After all three pieces of data in the same cycle buffer are complete, the data of that cycle is converted, read after synchronization, and low-pass filtered. The filtering result is then marked as a valid input for the system cycle.

[0200] Unified reading refers to retrieving data from the same cycle buffer, first performing phase advance compensation on the target acceleration based on the pre-calibrated inductor delay, or performing phase lag alignment on the driver current and encoder feedback speed, and then processing the phase-aligned parameters in the order of first converting the driving force, then filtering, and finally writing them into the valid input area, thereby avoiding the mixing of adjacent cycle data within the same system cycle;

[0201] To further clarify the execution rules of low-pass filtering, a first-order recursive filtering method is preferred to process the converted driving force according to the formula:

[0202]

[0203] in, Number the system control cycle. As the original driving force of the current system cycle, The driving force after periodic filtering of the current system. The driving force after periodic filtering of the previous system. The preset filter coefficients, and ;

[0204] The filtering of the mover velocity and the target acceleration preferably adopts the same recursive structure as described above, except that the input quantities are replaced with the velocity and the target acceleration of the current cycle, respectively;

[0205] Filter coefficients The preferred settings are based on the conveying cycle and system control cycle: when the conveying cycle frequency is greater than the preset cycle threshold, a value between 0.3 and 0.6 is used; when the conveying cycle frequency is less than or equal to the preset cycle threshold, a value between 0.6 and 0.9 is used, so as to achieve a balance between response speed and suppression of high-frequency fluctuations.

[0206] If the current system cycle is the first effective cycle after the start of the mission, it is preferable to use the original driving force, original velocity and original target acceleration of this cycle as the initial values ​​of the corresponding filtering results. In order to maintain the consistency of dimensions, the corresponding calibration value of force and current is preferably adopted for the driver thrust constant, so that the driving force converted by current and the estimated values ​​of inertial thrust, friction thrust and external contact force use the same force unit.

[0207] After this processing, there are clear data collection rules for collecting current according to the corresponding sampling period and for time synchronization of driving force, mover speed and target acceleration. The low-pass filter also has directly executable input, output and update order.

[0208] Furthermore, to avoid situations where the target acceleration has switched but the encoder feedback speed still reflects the mechanical response of the previous cycle within the same system cycle after time synchronization, this embodiment preferably uses the synchronized target acceleration, synchronized driving force, and synchronized mover speed as calculation inputs under the same cycle number. This set of inputs is only used for the estimation calculation of inertial thrust, frictional thrust, and external contact force in this cycle, and is not reused across cycles, so that the command quantity, feedback quantity, and conversion quantity in the control link maintain consistent time assignment when used.

[0209] If a valid sample value is not obtained in the current cycle, for example, if the current acquisition link has a missing duration of less than the preset duration, or if the encoder feedback value exceeds the reasonable range, then in this embodiment, the cycle data is not directly used to participate in the driving force conversion and trajectory risk judgment. Instead, the status control module outputs an abnormal status signal and maintains the previous valid parameter and the current protection strategy. This can avoid abnormal sampling being directly transmitted to the trajectory adjustment module, causing unnecessary trajectory fluctuations.

[0210] In some possible implementations, the steps of correcting the equivalent mass and friction parameters during the contactless free pitch phase include: when the estimated external contact force is continuously less than or equal to a preset identification threshold for a preset duration, the target acceleration is greater than or equal to a preset acceleration threshold, and the current of the driver is not saturated, correcting the equivalent mass based on the ratio of the result of the synchronized driving force minus the friction thrust to the target acceleration.

[0211] The identification error is determined by the difference between the driving force after the current cycle synchronization and the driving force calculated based on the equivalent mass, target acceleration and friction thrust. When the identification error exceeds the preset error threshold, the equivalent mass exceeds the preset mass range or enters the contact monitoring zone, the correction is stopped and the previous valid parameter determined when the update conditions were most recently met is retained.

[0212] The sign of the friction thrust is determined by the direction of the velocity of the mover, and the magnitude of the friction thrust is determined by the magnitude of the velocity, thus determining the friction thrust.

[0213] The steps for obtaining an estimate of the external contact force within the contact monitoring zone include: determining the estimate of the external contact force based on the synchronized driving force, equivalent mass, target acceleration, frictional thrust, and a pre-calibrated compensation term used to compensate for the zero bias of the actuator or the steady-state error of the model;

[0214] The risk status is determined based on the filtered external contact force estimate, its duration, and rate of change, combined with pre-set warning thresholds, safety thresholds, and recovery thresholds.

[0215] When the filtered external contact force estimate is greater than or equal to the warning threshold and less than the safety threshold, and remains greater than or equal to the preset warning time, a warning status is output; when the filtered external contact force estimate is greater than or equal to the safety threshold, or when the rate of change of the filtered external contact force estimate is greater than or equal to the preset sudden change threshold, an over-limit protection status is output.

[0216] The steps for adjusting subsequent pitch trajectory based on risk level include: continuing the current pitch trajectory under normal conditions; and reducing the subsequent acceleration or speed limit and extending the pitch change time under warning conditions.

[0217] When the product spacing is reduced further under the over-limit protection state, at least one of the following is executed according to the preset protection strategy: deceleration trajectory, buffer trajectory, or retraction trajectory.

[0218] In the event of an abnormal signal, updates will be stopped and the previous valid parameters of the equivalent mass and friction parameters will be retained. If the conditions for closed-loop operation are still met, the operation trajectory at the preset safe speed will be executed; otherwise, the machine will be stopped. The abnormal signal state is triggered by communication interruption or data out of bounds.

[0219] When the variable pitch task is completed, the contact risk is eliminated, and the signal is valid, update the equivalent mass and friction parameters that have passed the identification error and range constraint verification. Otherwise, retain the previous valid parameters and record the risk data, which includes at least the estimated external contact force, risk level, and trigger time.

[0220] The flexible variable pitch conveyor continuously transports packaging that is susceptible to compression. The mover closes the product spacing at a rate greater than the preset frequency threshold in the front section, and matches the required pitch with the downstream workstation in the rear section.

[0221] This embodiment further defines the parameter correction during the free pitch stage, the contact force estimation within the contact monitoring zone, and the subsequent trajectory processing under risk conditions;

[0222] Further convergence was made for the parameter correction conditions in the free pitch stage; if the equivalent mass is continuously updated based solely on the synchronized driving force and target acceleration, the obtained mass result may deviate from the current target load parameter when the product is close to contact, the driver current is close to saturation, or the trajectory excitation is insufficient.

[0223] To avoid this situation, in this embodiment, the equivalent mass is corrected only when the estimated external contact force is continuously lower than the preset identification threshold within a preset time period, the target acceleration is greater than the preset acceleration threshold, and the driver current is not saturated. The ratio of the result of the synchronized driving force minus the friction thrust to the target acceleration is used.

[0224] The sign of the frictional thrust is determined by the direction of the mover's velocity, and its magnitude is determined by the velocity magnitude, so that the friction term can remain consistent with the current direction of motion when moving in the forward direction, in the reverse direction, and near zero speed.

[0225] For the range close to zero speed, the friction direction determined in the previous cycle can be maintained until the absolute value of the speed exceeds the preset minimum speed threshold again before updating according to the current speed direction. This is to avoid the friction thrust sign jittering due to frequent direction switching near zero speed, which would further affect the equivalent mass correction result.

[0226] To ensure that the aforementioned update conditions have a clear basis, the preset identification threshold is preferably set at 10% to 30% of the safety threshold, the preset acceleration threshold is preferably set at 20% to 50% of the rated acceleration, and the current non-saturation is preferably defined as the sampled current being no higher than 80% to 95% of the rated continuous current or no higher than 90% of the short-time overload current threshold. The preset duration is preferably 3 to 20 continuous system cycles.

[0227] Among them, the two criteria for current non-saturation are selected and executed according to the current operating mode of the driver: when the driver is in continuous operation, the criterion that the sampled current is not higher than 80% to 95% of the rated continuous current is used; when the driver is in high dynamic operation that allows short-term overload, the criterion that the sampled current is not higher than 90% of the short-term overload current threshold is used; the two criteria are judged according to one of the current operating modes, and it is not required that they be met at the same time.

[0228] The preset duration and the warning time used for risk assessment are two different types of duration parameters: the preset duration is used to confirm that no contact has been formed between products, and is accumulated by the parameter correction module according to an independent identification counter; the warning time is used to confirm that the contact risk continues to exist, and is accumulated by the risk assessment module according to an independent warning accumulation counter. The two are counted separately and do not reuse each other, so no judgment conflict will occur when their numerical ranges partially overlap.

[0229] The selection principle for the above thresholds is: to ensure that the contact effect has not significantly entered the estimation link, so that the equivalent mass correction still has sufficient excitation and the driver is in the linear conversion range.

[0230] To ensure that the determination of the friction thrust amplitude based on the speed has a clear rule, the friction thrust amplitude is preferably determined in a segmented manner: when the absolute value of the speed is less than the preset minimum speed threshold, the static friction thrust amplitude corresponding to the previous effective parameter is used;

[0231] When the absolute value of the speed is greater than or equal to the preset minimum speed threshold and less than the preset switching speed threshold, the friction thrust amplitude corresponding to the low-speed zone friction parameters is used.

[0232] When the absolute value of the speed is greater than or equal to the preset switching speed threshold, the friction thrust amplitude corresponding to the friction parameters in the high-speed zone is adopted. Therefore, the order of determining the friction thrust is to first assign a positive or negative sign according to the speed direction, and then select the corresponding amplitude according to the speed range, thereby forming an input-output relationship that can be directly executed, without needing to infer the friction term temporarily during contact monitoring.

[0233] Furthermore, in order to clarify the sources of friction parameters in the low-speed zone and the high-speed zone, when the update conditions are met during the free pitch change stage, the system preferably divides the current cycle into the low-speed zone or the high-speed zone according to whether the absolute value of the speed is lower than the preset switching speed threshold.

[0234] Within the corresponding interval, the remaining thrust after deducting the inertial thrust from the driving force in multiple consecutive system cycles is read, and the remaining thrust in the same direction is averaged. The average result is used as the friction thrust amplitude in that speed interval.

[0235] When the dispersion of the remaining thrust within the continuous sampling window exceeds the preset fluctuation range, the current friction parameter update is abandoned and the previous valid friction parameter is retained. After this processing, the friction thrust amplitude is no longer given by name alone, but has a determination process corresponding to the velocity range, direction and continuous sampling window.

[0236] It should be noted that the aforementioned segmented determination of friction thrust amplitude based on velocity magnitude and the averaging of the remaining thrust within the preset continuous sampling window are two sequential steps: when the update conditions are met during the free pitch stage, the friction parameters corresponding to each velocity range and velocity direction are first obtained and updated through continuous sampling window averaging; when the friction thrust is called in the parameter correction and contact force estimation stages, the corresponding friction thrust amplitude is selected according to the current velocity direction and the velocity range; that is, window averaging is used as the source for updating friction parameters, and segmented selection is used for real-time calling of friction thrust, and the two do not constitute a parallel substitution relationship; the preset fluctuation range is preferably set at 10% to 25% of the average value of the remaining thrust within the corresponding continuous sampling window, and the degree of dispersion is determined by the ratio of the difference between the maximum and minimum values ​​of the remaining thrust within the window to the average value. When this ratio exceeds the preset fluctuation range, it is determined that the data in this window is not suitable for updating friction parameters;

[0237] The corrected equivalent mass is not directly regarded as the final parameter for this cycle, but continues to be subject to validity constraints. If the error corresponding to the identification result of the current cycle exceeds the preset error threshold, it indicates that the matching relationship between the driving force, acceleration or friction thrust in this cycle is insufficient to support parameter updates.

[0238] If the equivalent mass exceeds the preset mass range, it indicates that the estimated result has deviated from the reasonable load range of the mover and its supported products; if the system has entered the contact monitoring zone, it indicates that the driving force in this cycle may already include the contact effect between products; in any of the above cases, the system stops correction and retains the previous valid parameter determined when the update conditions were most recently met.

[0239] The contact monitoring zone corresponds to the contact monitoring mentioned above, and both are used to characterize that the product spacing has entered the range where external contact force estimation and risk assessment need to be performed;

[0240] It should be noted that the contact monitoring zone and the protection phase are two sequential stages: the correction of equivalent mass and friction parameters stops immediately after the system enters the contact monitoring zone, and the protection phase is the subsequent stage after the over-limit protection state is determined in the contact monitoring zone and the trajectory adjustment results are executed; therefore, when entering the contact monitoring zone is used as the condition for stopping correction, the stopping time is earlier than and covers the situation in the protection phase. The two expressions correspond to the same parameter freezing point, that is, the equivalent mass and friction parameters remain the previous effective parameters from the time of entering the contact monitoring zone and are no longer updated.

[0241] The previous valid parameter refers to the equivalent mass and friction parameters that were retained when the identification threshold, acceleration threshold, current unsaturation, and error and range constraints were met most recently.

[0242] After this processing, the equivalent mass and friction parameters called upon when entering the contact monitoring zone are derived from the valid results confirmed during the free torque stage, rather than the fluctuation values ​​near contact.

[0243] The aforementioned identification error can be determined by the difference between the driving force after synchronization in the current cycle and the driving force calculated based on the equivalent mass, target acceleration and friction thrust. The preset error threshold is preferably set at 5% to 15% of the amplitude of the calculated driving force.

[0244] The equivalent mass range is preferably set between 0.8 and 1.2 times the equivalent mass of the unloaded mover and the equivalent mass of the corresponding product specification under full load, or it can be set between the minimum and maximum load parameters obtained from the equipment calibration.

[0245] The applicable conditions for the above two methods of determining the preset mass range are as follows: When the product specification issued by the host computer includes the corresponding full-load equivalent mass parameter, the range from the unloaded mover equivalent mass to 0.8 to 1.2 times the full-load equivalent mass of the product specification shall be used first; when the product specification does not include the full-load equivalent mass parameter and the equipment has completed calibration covering the minimum load to the maximum load, the range between the minimum load parameter and the maximum load parameter obtained from the equipment calibration shall be used; when the ranges determined by the two methods are available at the same time, the intersection of the two shall be taken as the preset mass range so that the range constraint simultaneously meets the limitations of both the theoretical value of the product specification and the measured value of the equipment.

[0246] After this processing, the error threshold and mass range have clear sources, rather than just qualitative limitations; furthermore, in order to ensure that the process of correcting the equivalent mass based on the ratio of the result after deducting the frictional thrust from the synchronized driving force to the target acceleration has a definite order, the parameter correction module preferably reads the synchronized driving force and frictional thrust of the current cycle first, and calculates the result after deducting the frictional thrust from the driving force.

[0247] When the target acceleration is greater than the preset acceleration threshold, the aforementioned result is divided by the target acceleration to obtain the candidate equivalent mass for the current period. Identification error verification and mass range verification are performed in sequence. Only when both verifications pass is the candidate equivalent mass written into the current valid parameter area; otherwise, the previous valid parameter is retained. After this processing, the input, calculation order, and update conditions of the equivalent mass correction can be directly mapped to the control flow.

[0248] Furthermore, to avoid the ratio from being amplified when the target acceleration is close to zero, parameter correction is only performed when the absolute value of the target acceleration is greater than a preset acceleration threshold.

[0249] When the direction of the target acceleration changes but the velocity has not yet stabilized and exceeded the preset minimum velocity threshold, the friction thrust remains in the previous effective direction. The sign is updated only after the velocity direction stabilizes. After this processing, the driving force, friction thrust and target acceleration maintain the same direction judgment basis when participating in the ratio calculation, avoiding abnormal amplification of candidate equivalent mass caused by sign jitter near zero velocity or acceleration below the preset threshold.

[0250] Furthermore, to avoid ambiguity in the units of equivalent mass correction and subsequent contact force estimation, the synchronized driving force, frictional thrust, inertial thrust, external contact force estimation and pre-calibrated compensation terms all use the same force unit, the target acceleration uses the acceleration unit of length divided by the square of time, and the equivalent mass uses the mass unit.

[0251] Therefore, the equivalent mass is obtained by dividing the result of the driving force after deducting the frictional thrust by the target acceleration. The external contact force estimate is still obtained by subtracting the thrust terms in the contact monitoring area from each other, so that each calculation link is consistent in physical dimensions.

[0252] Furthermore, when correcting the equivalent mass based on the ratio of the result of the driving force after deducting the frictional thrust after synchronization to the target acceleration, it is preferable to use the absolute value of the target acceleration as the denominator criterion, and use the algebraic quantity of the driving force and frictional thrust agreed upon in a unified direction in the calculation; when the absolute value of the target acceleration does not reach the preset acceleration threshold, the correction for this cycle is directly abandoned.

[0253] After this treatment, the abnormal increase in candidate equivalent mass caused by an excessively small denominator is suppressed, and the unit correspondence between force and acceleration remains clear.

[0254] Furthermore, to avoid jitter caused by direct overwriting of candidate parameters across multiple consecutive cycles during the free pitch stage, the system preferably places the candidate equivalent quality obtained in each cycle in a pending confirmation state, and only updates the cumulative count value of consecutive system cycles when the update conditions are met. And the absolute value of the difference between candidate equivalent masses of adjacent system periods hour, For the current period, the candidate equivalent quality is... The candidate equivalent quality for the previous cycle. The latest candidate value is only selected based on a pre-defined quality convergence threshold parameter. Write to the currently valid parameter area;

[0255] The quality convergence threshold parameter is preferably set to 1% to 5% of the current effective equivalent quality, so that when the absolute value of the difference between the candidate equivalent quality of adjacent system cycles is less than the threshold, the fluctuation of the candidate parameter has fallen within the acceptable range of load disturbance; the cumulative count value of continuous system cycles that meet the update conditions is preferably 3 to 10 system cycles; it should be noted that the convergence determination combining the continuous count and the quality convergence threshold is the preferred implementation. In other implementations, the convergence determination layer may not be set, and when the update conditions are met in a single cycle and the identification error verification and quality range verification are passed, the candidate equivalent quality of that cycle is written into the current effective parameter area;

[0256] If the contact monitoring area is entered during the confirmation period, current saturation occurs, or the identification error exceeds the limit, the candidate results that have not yet been transferred to the current valid parameters should be immediately abandoned and the previous valid parameter should be maintained.

[0257] After this processing, the data life cycle and state switching path in the parameter correction process are clearer, avoiding the direct change of the basis for subsequent contact force estimation by a single periodic disturbance;

[0258] This is used to further explain the estimation of external contact force and the assessment of risk status within the contact monitoring zone; after entering the contact monitoring zone, the system reads the synchronized driving force, the currently effective equivalent mass, the target acceleration and friction thrust, and calculates the estimated value of external contact force in conjunction with the pre-calibrated compensation terms;

[0259] This compensation term is used to compensate for the zero bias of the driver or the steady-state error of the model, so that the estimation result when no contact occurs is kept near a reasonable benchmark. The compensated contact force estimate is then filtered and compared with the pre-set warning threshold, safety threshold and recovery threshold in combination with its duration and rate of change.

[0260] The rate of change is preferably determined based on the difference between the filtered external contact force estimates of adjacent system periods, and is used to characterize how fast the contact force rises or falls.

[0261] The recovery threshold is set below the warning threshold so as to distinguish it from the warning entry condition when the risk is cleared. The aforementioned compensation item is a pre-calibrated compensation item in this embodiment. It means that the compensation amount is pre-determined and stored for the zero bias of the driver or the steady-state error of the model under standard no-load or known reference load conditions. It is directly called in the subsequent contact force estimation process, instead of being recalculated temporarily in the contact monitoring area, so that the source and purpose of the compensation item are clear.

[0262] Pre-calibrated compensation items are preferably determined based on the baseline operation process after equipment installation: Under the baseline operating condition without product contact, synchronous driving force, target acceleration and friction thrust are collected in multiple system cycles, the average offset of the uncompensated external contact force estimate is calculated, and the average offset is stored as a compensation item.

[0263] When a product specification change causes a change in the load range greater than a preset change threshold, a compensation item corresponding to that product specification or load range can be invoked. After this processing, the compensation item is not given in an abstract way, but has a repeatable and definite path.

[0264] It should be noted that the determination of friction thrust during the above calibration process does not depend on the friction parameter identification results during normal operation: the calibration stage uses the no-load friction parameters measured and stored during equipment installation, or directly uses the fixed friction experience values ​​of the corresponding speed range to participate in the calculation of the uncompensated external contact force estimate, so there is no interdependent cyclic calculation between the calibration stage and the normal operation stage; after calibration is completed and normal operation begins, the friction parameters identified in the free pitch stage are only used for contact force estimation and parameter correction, and are not written back to the compensation item; when the compensation item needs to be updated after the product specification is switched, the calibration is re-executed according to the above benchmark conditions; the preset change threshold is preferably set at 5% to 15% of the difference in the full-load equivalent mass of the product specification before and after the switch, or at 10% to 30% of the absolute value of the current compensation item, to determine whether the load range change reaches the level that requires switching the compensation item;

[0265] To further clarify the relationship for obtaining the external contact force estimate, the external contact force estimate for the current cycle is preferably determined in the order of subtracting the inertial thrust, frictional thrust, and pre-calibrated compensation term from the synchronized driving force. The inertial thrust is determined by the current effective equivalent mass and the target acceleration, and the frictional thrust is determined by the current effective frictional parameters confirmed before entering the contact monitoring zone.

[0266] After this processing, each component of the driving force is deducted in sequence, and the estimated value in the contact monitoring area is clearly derived and forms a connection with the free pitch stage.

[0267] To make the directional relationship between the compensation term and the remaining quantities clearer, the compensation term is preferably pre-calibrated to use the same force unit as the estimated value of the external contact force, and participates in the deduction calculation according to the same sign convention as the driving force after synchronization. This way, the compensation term is only used to correct zero bias or steady-state offset, without changing the physical meaning of the inertial thrust and friction thrust.

[0268] Furthermore, the estimated external contact force for the current cycle is preferably calculated according to the formula:

[0269]

[0270] in, This is the estimated external contact force for the current system cycle. The driving force after periodic filtering of the current system. For the current effective equivalent quality, The current system cycle is the current running acceleration obtained by differential calculation and filtering of the encoder feedback velocity. The frictional thrust for the current system cycle. To pre-determine compensation items, Number the system control cycle;

[0271] It should be noted that the acceleration used for inertial thrust calculation in this embodiment is differentiated by stage as follows: In the parameter correction stage, the inertial thrust is determined according to the target acceleration output by the trajectory generation module, so that the equivalent mass correction directly corresponds to the trajectory planning quantity; in the contact force estimation stage, in order to suppress the interference of trajectory command abrupt changes and the deviation between the planning quantity and the execution quantity on the estimation results, the inertial thrust is determined according to the current running acceleration obtained by differential calculation and filtering of the encoder feedback velocity; under steady-state conditions with good trajectory tracking, the deviation between the current running acceleration and the target acceleration is within the preset error range, and the selection of the two acceleration references does not change the calculation structure of the inertial thrust; accordingly, the statement of determining the inertial thrust based on the target acceleration in this embodiment is specifically implemented by the feedback velocity differential result after periodic filtering of the current system in the contact force estimation stage;

[0272] To avoid duplicate deductions due to different signs for compensation items, friction thrust, or inertial thrust, this embodiment preferably defines the conveying direction as the positive direction. The driving force, inertial thrust, friction thrust, and compensation items acting along this positive direction are taken as positive signs, while those acting in the opposite direction are taken as negative signs. This directional convention is uniformly used for calculation within the same system cycle.

[0273] After this processing, the input quantities, calculation order, and directional conventions of the external contact force estimation values ​​all have clear rules;

[0274] Furthermore, the compensation term is preferably maintained as a constant term corresponding to the product specifications or load range, and is not rewritten in real time with the single-cycle contact force estimation results during the same task after entering the contact monitoring zone. This avoids erroneously absorbing the additional force caused by physical contact into the compensation term, ensuring... The meanings of each item in the middle are stable;

[0275] In risk status assessment, if the filtered external contact force estimate reaches the warning threshold and continues to exceed the preset warning time, the system outputs a warning status, indicating that the current situation has not yet reached the point where it is necessary to immediately stop compressing the gap, but the subsequent trajectory needs to start converging.

[0276] If the estimated external contact force exceeds the safety threshold, or if the rate of change exceeds the preset mutation threshold even though it does not exceed the safety threshold, the system outputs an over-limit protection status, indicating that the contact risk should be dealt with first in the current cycle and subsequent cycles; the recovery threshold is used to determine the risk removal, so that there is a clear backoff condition before the status returns to normal, and avoids repeated switching near the threshold.

[0277] It should be noted that in this embodiment, all external contact force estimates and their rates of change that are compared with the warning threshold, safety threshold, recovery threshold, or mutation threshold refer to the filtered external contact force estimates and the rates of change determined therefrom; only in the original calculation stage of the contact force calculation module does it refer to the external contact force estimates before filtering; thus, the comparison objects in each stage of risk assessment refer to the same thing before and after filtering.

[0278] Specifically, when the filtered external contact force estimate falls below the recovery threshold and continues for a preset recovery time, the system will release the warning state or over-limit protection state and resume execution according to the new subsequent trajectory, so that entering the risk state and exiting the risk state are constrained by different thresholds respectively.

[0279] The duration is the length of time that the same risk judgment condition is continuously met; the warning time is the shortest continuous time required to maintain the state after the external contact force estimate reaches the warning threshold; and the preset recovery time is the shortest continuous time required to remove the risk state after the external contact force estimate falls below the recovery threshold. All three are accumulated over the system control cycle to avoid single-cycle fluctuations directly triggering state switching.

[0280] To make the basis for determining the duration and rate of change clearer, the duration is obtained by accumulating the system cycles that continuously meet the same judgment condition; the rate of change is determined by the ratio of the difference between the filtered external contact force estimates of two adjacent system cycles to the corresponding cycle duration. When the system cycle is fixed, the rate of change can be directly compared with the preset mutation threshold based on the difference between the filtered external contact force estimates of two adjacent system cycles.

[0281] The warning time is preferably 2 to 10 system cycles, the preset recovery time is preferably not less than the warning time, and the mutation threshold is preferably set according to the ratio of the equivalent increase of the safety threshold in 1 to 3 system cycles to the corresponding duration. This setting enables the system to use the warning state to converge the trajectory in advance for a continuously slowly increasing contact trend, and to directly enter the over-limit protection state for a contact trend with a change rate greater than or equal to the mutation threshold.

[0282] Furthermore, the preferred order for judging the risk status is as follows: first, determine whether the filtered external contact force estimate exceeds the safety threshold; if so, output the over-limit protection status directly; if not, then determine whether its rate of change exceeds the preset mutation threshold; if so, output the over-limit protection status; if not, then determine whether it reaches the warning threshold and continuously meets the warning time; if so, output the warning status.

[0283] If none of the aforementioned conditions are met, the normal state is maintained. For the risk-relief state, under the premise that the state is already in the warning state or the over-limit protection state, the state will only be restored to normal when the filtered external contact force estimate is continuously lower than the recovery threshold for a preset recovery time. Thus, the risk judgment no longer rests on a general comparison, but has a fixed order of judgment.

[0284] Furthermore, to ensure that the duration and rate of change have a defined data caliber during program execution, the system preferably sets up an early warning cumulative counter, a recovery cumulative counter, and a rate of change buffer.

[0285] The system includes a warning cumulative counter that increments periodically when the filtered external contact force estimate is greater than or equal to the warning threshold but has not reached the safety threshold, and is reset to zero if the aforementioned conditions are not met in any cycle; a recovery cumulative counter that increments periodically when the system is in a warning state or over-limit protection state and the filtered external contact force estimate is lower than the recovery threshold, and is reset to zero if the aforementioned conditions are not met in any cycle; and a rate of change buffer that stores the filtered external contact force estimate for at least the previous system cycle.

[0286] When assessing risk, it is preferable to first read the filtered external contact force estimate from the rate of change buffer of the previous system cycle, and then compare it with the filtered external contact force estimate of the current system cycle to determine whether the rate of change exceeds the preset mutation threshold.

[0287] Then, based on whether the cumulative early warning counter has reached the number of cycles corresponding to the preset early warning time, it is determined whether to output an early warning status; after this processing, a clear execution order is formed between the method of obtaining the duration and rate of change and the output of the risk status;

[0288] Furthermore, to avoid control conflicts when the warning state, over-limit protection state, and signal abnormal state are triggered concurrently in the same cycle, the system preferably performs the judgment in the order of signal validity, contact safety, and trajectory continuity: first, it is determined whether there is a communication interruption, data out-of-bounds, or sampling loss; if so, and it has affected the closed-loop operation conditions, then the signal abnormal state is directly output and the current risk level increase judgment is stopped.

[0289] If a risk exists but has not yet affected the closed-loop operating conditions, the risk status confirmed in the previous cycle is maintained, and it is prohibited to remove the existing warning status or over-limit protection status based on incomplete data in this cycle; the comparison process of safety threshold, mutation threshold and warning threshold is only continued when the signal is valid; after this processing, the priority and jump path when multiple states occur concurrently are clearer.

[0290] Rules for defining subsequent trajectory processing and parameter retention at the end of the task under different risk levels; in the normal state, the system continues to execute the current variable pitch trajectory without additional shrinking of the original trajectory; in the warning state, the system lowers the upper limit of subsequent acceleration or speed and extends the variable pitch time accordingly, so that the subsequent product spacing changes tend to be smoother.

[0291] When in over-limit protection state, the system stops further reducing the product spacing and executes at least one of the deceleration trajectory, buffer trajectory or retreat trajectory according to the preset protection strategy to reduce the current contact trend or release the contact that has been formed;

[0292] To ensure the feasibility of subsequent trajectory processing, the preferred reduction ratio for the upper limit of acceleration under the warning state is 10% to 30%, the preferred reduction ratio for the upper limit of speed is 5% to 20%, and the preferred extension ratio for the corresponding pitch change time is 5% to 25%.

[0293] The selection of the above-mentioned proportion range is based on the following: when the acceleration upper limit is reduced by less than 10% or the speed upper limit is reduced by less than 5%, the convergence of the subsequent trajectory is insufficient to change the established contact trend; when the acceleration upper limit is reduced by more than 30% or the speed upper limit is reduced by more than 20%, the remaining pitch change time is significantly extended, which will affect the conveying cycle time matching the downstream workstation; the pitch change time extension ratio is limited to 5% to 25% to achieve a balance between contact trend convergence and cycle time loss; the deceleration trajectory decreases to 20% to 60% of the current speed within 1 to 5 system cycles, which enables the mover to quickly reduce the approach speed before the contact continues to intensify, while avoiding mechanical impact caused by single-cycle emergency stop; the retraction amount of the retraction trajectory is limited to no more than 5% to 20% of the target pitch, which is used to remove the established slight contact while avoiding excessive retraction that would require replanning of the pitch change task;

[0294] Under over-limit protection conditions, if the filtered external contact force estimate is only slightly higher than the safety threshold, the deceleration trajectory or buffer trajectory will be executed first. If the filtered external contact force estimate continues to rise or the rate of change continues to exceed the sudden change threshold, the retreat trajectory will be executed.

[0295] After this processing, the control actions and selection conditions corresponding to different risk levels all have clear boundaries; in order to further clarify the steps of adjusting the subsequent variable trajectory according to the risk level, under normal conditions, it is preferable to keep the remaining trajectory sequence in the current task record unchanged; under the warning state, it is preferable to start from the next system cycle, recalculate the remaining trajectory sequence with the lowered acceleration upper limit or velocity upper limit, and replace the original end time with the recalculated end time;

[0296] Under over-limit protection conditions, the preferred approach is to first set the target displacement component that will continue to reduce the product spacing to zero, and then generate the corresponding remaining trajectory sequence according to the deceleration, buffering, or backoff strategies respectively; thus, a one-to-one correspondence is formed between the risk level and the subsequent trajectory recalculation object;

[0297] Furthermore, in order to make stopping the reduction of product spacing have a clear control meaning, under the over-limit protection state, the system preferably locks the pitch reduction amount set along the compression direction in the subsequent trajectory sequence to zero, or rewrites the compression displacement that has not yet been executed to a holding displacement that is no greater than the product spacing at the end of the current cycle;

[0298] When executing the rollback trajectory, an additional rollback displacement along the anti-compression direction is added to the existing displacement. After this processing, the displacement constraint corresponding to the product spacing that can be directly written to the trajectory buffer is stopped during the protection phase, instead of just the control target description.

[0299] In the event of an abnormal signal, the system will no longer update the equivalent mass and friction parameters, but will retain the previous valid parameters. If communication is interrupted or data exceeds the limit, and the system still has the closed-loop operating conditions required for position control, it will execute the operating trajectory according to the preset safe speed. If the closed-loop operating conditions are no longer met, the system will be shut down.

[0300] Data out of bounds has the same meaning as mentioned above, referring to the estimated values ​​of position, speed, current, driving force, or external contact force exceeding the preset reasonable range;

[0301] The purpose of this approach is to prioritize ensuring that the equipment operates within a controllable range when an anomaly occurs in the sampling link, rather than continuing to make contact judgments and replan the trajectory based on incomplete data.

[0302] When the pitch change task is completed, the contact risk is eliminated, and the signal is valid, the system verifies the equivalent mass and friction parameters obtained in this cycle. Only the parameters that pass the identification error and range constraint verification are updated as new valid parameters.

[0303] If an over-limit protection, signal abnormality, or parameter failure occurs during this cycle, the previous valid parameter will be retained, and the corresponding risk data will be recorded. The recorded risk data will include at least the estimated external contact force, risk level, and trigger time, which will be used to call historical valid parameters and verify the occurrence of risks when similar product tasks are restarted in the future.

[0304] For the trigger time, it is preferable to record it as the system cycle number or system clock time corresponding to the first confirmation of the risk status; for the risk level, it is preferable to record it as one of the status identifiers: normal, warning, over-limit protection, and signal abnormality.

[0305] For the external contact force estimate, it is preferable to record the filtered external contact force estimate corresponding to the trigger cycle; after this processing, the recorded content of the risk data can directly correspond to the content called in the subsequent calls.

[0306] In this embodiment, each stage of processing revolves around the same delivery task: the free pitch stage is used to obtain available parameters, the contact monitoring zone is used to calculate and judge the contact force, the risk handling stage is used to modify the subsequent pitch trajectory, and the task end stage is used to submit or retain parameters.

[0307] Each stage is connected by the previous valid parameters, the current trajectory parameters, and the current risk status, so there is no need to reinterpret the original sampling source of the previous stage in subsequent stages, thus enabling the whole method to be executed stably under continuous transportation conditions.

[0308] Furthermore, compared to contact detection schemes that add physical force sensors to the conveyor line, this embodiment does not increase sensor hardware or its wiring, calibration, and maintenance. The contact force estimation fully reuses existing signals such as driver current and encoder feedback, enabling the system to obtain contact trend judgment capabilities without changing the mechanical structure. Compared to conventional schemes that directly compare thresholds based on driver current or current change rate, this embodiment first deducts the inertial thrust and friction thrust determined by the current effective equivalent mass and friction parameters from the driving force, and then compares it with the warning threshold and safety threshold. This prevents the driving response during the pitch acceleration and deceleration phase from directly entering the risk judgment, reducing the misjudgment rate under normal pitch conditions. Compared to the commonly used force observation method that continuously identifies load parameters online, this embodiment limits parameter correction to the non-contact free pitch phase and freezes the parameters after entering the contact monitoring zone. This prevents the additional thrust caused by contact from being absorbed into the equivalent mass or friction parameters, thereby maintaining a stable comparison benchmark for the external contact force estimate before and after contact formation.

Claims

1. An industrial control system for a flexible variable-pitch conveyor, applied to a flexible variable-pitch conveyor including a driver, a mover connected to the driver, and an encoder, characterized in that, include: The trajectory generation module is used to generate a variable pitch trajectory based on the product specifications, target pitch and conveying cycle time sent by the host computer, combined with the position of the mover and adjacent movers, and output the target position, target velocity and target acceleration. The position control module is communicatively connected to the encoder to obtain the position and velocity of the mover fed back by the encoder, and determines the position error in combination with the target position; A current acquisition module is used to acquire the current of the driver and convert it into driving force according to the driver thrust constant; The thrust calculation module is used to determine the inertial thrust based on the equivalent mass and the target acceleration, and to determine the friction thrust based on the friction parameters and the velocity of the mover. The signal processing module is used to perform time synchronization and filtering on the driving force, the velocity of the mover, and the target acceleration; The parameter correction module is used to correct the equivalent mass and the friction parameters based on the synchronized driving force, the target acceleration, and the friction thrust during the non-contact free pitch change phase. The contact force calculation module is used to subtract the inertial thrust and the frictional thrust from the driving force to obtain an estimated value of the external contact force; The risk assessment module is used to determine the risk level based on the comparison results between the estimated external contact force and the warning threshold and safety threshold. The trajectory adjustment module is used to output instructions to adjust the subsequent variable-pitch trajectory according to the risk level; The status control module is used to control the execution and switching of each module according to the trajectory generation stage, free pitch stage, contact monitoring stage and protection stage.

2. The industrial control system for the flexible variable-pitch conveyor according to claim 1, characterized in that, The current acquisition module acquires the current according to a sampling period corresponding to the position and velocity fed back by the encoder and the target acceleration; The signal processing module is also used to perform low-pass filtering on the converted driving force, the velocity of the mover, and the target acceleration.

3. The industrial control system for the flexible variable-pitch conveyor according to claim 2, characterized in that, When the estimated external contact force value is continuously less than or equal to a preset identification threshold within a preset time period, the target acceleration is greater than or equal to a preset acceleration threshold, and the current of the driver is not saturated, the parameter correction module corrects the equivalent mass based on the ratio of the result of the driving force minus the friction thrust to the target acceleration. The identification error is determined by the difference between the driving force in the current cycle and the driving force calculated based on the equivalent mass, target acceleration, and friction thrust. When the identification error exceeds the preset error threshold, the equivalent mass exceeds the preset mass range, or the state control module enters the contact monitoring stage, the update stops and the last valid parameter determined when the update conditions were met is retained.

4. The industrial control system for the flexible variable-pitch conveyor according to claim 3, characterized in that, The risk assessment module filters the estimated external contact force and determines the risk level based on the filtered estimated external contact force and the preset warning threshold and safety threshold. The risk level includes a warning state and an over-limit protection state. The trajectory adjustment module reduces the subsequent acceleration limit or speed limit in the warning state, and executes at least one of the deceleration trajectory, buffer trajectory or retreat trajectory according to the preset protection strategy in the over-limit protection state. The state control module stops updating and maintains the previous valid parameters of the equivalent mass and friction parameters when the contact monitoring and over-limit protection are in effect; when communication interruption, data out-of-bounds, or sampling is missing, it outputs an abnormal signal state.

5. An industrial control method for a flexible variable-pitch conveyor, applied to a flexible variable-pitch conveyor comprising a driver, a mover connected to the driver, and an encoder, characterized in that, include: The system obtains the product specifications, current product spacing, target pitch, and conveying cycle time issued by the host computer, as well as the position of the mover and the position of the mover adjacent to the mover fed back by the encoder. Verify the communication status of the encoder, current acquisition link, and driver; The variable pitch transition trajectory is determined based on the verification results, the current product spacing, the target pitch, and the conveying cycle time, and the target position, target speed, and target acceleration are output. Based on the target position and the position fed back by the encoder, position closed-loop control is performed to control the driver to drive the mover to run; The current of the driver is collected and converted into driving force based on the driver thrust constant; The driving force, the velocity of the mover, and the target acceleration are time-synchronized and filtered to obtain synchronized driving force, velocity of the mover, and target acceleration. During the non-contact free pitch phase, the equivalent mass and friction parameters are corrected based on the synchronized driving force, the target acceleration, and the friction thrust. When the current product spacing is reduced to a preset contact monitoring zone, the estimated value of the external contact force is obtained by subtracting the inertial thrust determined according to the equivalent mass and the target acceleration, and the frictional thrust determined according to the friction parameters and the velocity of the mover, from the synchronized driving force. The risk level is determined based on the comparison between the estimated external contact force and the warning threshold and safety threshold, and the subsequent variable pitch trajectory is adjusted according to the risk level.

6. The industrial control method for the flexible variable-pitch conveyor according to claim 5, characterized in that, The steps of acquiring the current of the driver and converting it into driving force, as well as synchronous filtering, include: The current is acquired according to a sampling period corresponding to the position fed back by the encoder and the target acceleration; The current is converted into the driving force based on the driver thrust constant; The converted driving force, the velocity of the mover, and the target acceleration are time-synchronized and low-pass filtered to obtain the synchronized driving force, the velocity of the mover, and the target acceleration.

7. The industrial control method for the flexible variable-pitch conveyor according to claim 6, characterized in that, The steps for correcting the equivalent mass and friction parameters during the non-contact free-torsion phase include: When the estimated external contact force value is continuously less than or equal to a preset identification threshold within a preset time period, the target acceleration is greater than or equal to a preset acceleration threshold, and the current of the driver is not saturated, the equivalent mass is corrected based on the ratio of the result of the synchronized driving force minus the frictional thrust to the target acceleration. The identification error is determined by the difference between the driving force after the current cycle synchronization and the driving force calculated based on the equivalent mass, target acceleration and friction thrust. When the identification error exceeds the preset error threshold, the equivalent mass exceeds the preset mass range or enters the contact monitoring area, the correction is stopped and the previous valid parameter determined when the update conditions were most recently met is retained. The sign of the friction thrust is determined based on the direction of the velocity of the mover, and the magnitude of the friction thrust is determined based on the magnitude of the velocity, thereby determining the friction thrust.

8. The industrial control method for the flexible variable-pitch conveyor according to claim 7, characterized in that, The steps for obtaining an estimate of the external contact force within the contact monitoring area include: The estimated value of the external contact force is determined based on the synchronized driving force, the equivalent mass, the target acceleration, the frictional thrust, and the pre-calibrated compensation term used to compensate for the zero bias or steady-state error of the driver model. The risk status is determined based on the filtered external contact force estimate, its duration, and rate of change, combined with the pre-set warning threshold, safety threshold, and recovery threshold. When the filtered external contact force estimate is greater than or equal to the warning threshold and less than the safety threshold, and remains greater than or equal to the preset warning time, a warning state is output; when the filtered external contact force estimate is greater than or equal to the safety threshold, or the rate of change of the filtered external contact force estimate is greater than or equal to the preset sudden change threshold, an over-limit protection state is output.

9. The industrial control method for the flexible variable-pitch conveyor according to claim 8, characterized in that, The steps for adjusting subsequent pitch trajectories based on the risk level include: continuing to execute the current pitch trajectories under normal conditions; In the aforementioned warning state, the subsequent acceleration limit or speed limit is reduced and the pitch change time is extended; Under the over-limit protection state, the product spacing is stopped from decreasing further, and at least one of the deceleration trajectory, buffer trajectory, or retraction trajectory is executed according to the preset protection strategy; In the event of an abnormal signal, updates are stopped and the previous valid parameters of the equivalent mass and friction parameters are retained. If the closed-loop operation conditions are still met, the operation trajectory at the preset safe speed is executed; otherwise, a shutdown process is executed. The abnormal signal state is triggered by communication interruption or data out of bounds. When the variable pitch task is completed, the contact risk is eliminated, and the signal is valid, update the equivalent mass and the friction parameters that have passed the identification error and range constraint verification; otherwise, retain the previous valid parameters and record the risk data, which includes at least the estimated external contact force, the risk level, and the trigger time.

Images