Intelligent clamping control method and device of engine end cover three-point linkage clamp

Abstract

The application relates to an intelligent clamping control method and device of an engine end cover three-point linkage clamp, and relates to the technical field of machining clamp control. The scheme comprises the following steps: acquiring real-time clamping force parameters of three clamping points and determining minimum and maximum clamping forces, generating control criteria for continuous clamping and stop clamping according to the minimum and maximum clamping forces; in the clamping process, whether the minimum clamping force meets the standard is taken as the lower limit basis of the continuous action, and whether the maximum clamping force is over the limit is taken as the upper limit basis of the stop action, and the driving motor is controlled to execute the continuous clamping, keeping or stop action. The application can effectively solve the problem that it is difficult to consider the contact integrity and local anti-overload when a single motor links multiple points for clamping, and improves the stability and safety of the clamping control.

Description

Technical Field

[0001] This invention belongs to the field of machining fixture control technology, specifically an intelligent clamping control method and device for a three-point linkage fixture for an engine end cover. Background Technology

[0002] As a key component of internal combustion engines, the engine end cover typically features a thin-walled structure, mounting bosses, complex hole systems, and irregularly shaped structures, placing extremely high demands on positioning accuracy and clamping stability during CNC machining. To prevent workpiece displacement or vibration under cutting forces, and to avoid elastic deformation or even permanent damage to the thin-walled structure due to excessive clamping force, the industry commonly employs multi-point linkage mechanical clamping solutions. Current mainstream technologies often use a single drive source in conjunction with linkages, toothed belts, or cam mechanisms to achieve synchronous movement of multiple clamping points, forming a surrounding fixation of the workpiece. In such systems, the control logic usually relies on current feedback from the drive motor or a preset time stroke to determine the clamping completion status. Some advanced solutions introduce force sensors to monitor the overall load and adjust the motor output accordingly to achieve the desired clamping effect.

[0003] As a specific mechanical implementation, CN116652644A discloses a clamping fixture for machining engine end covers. Its three arc-shaped disc components are linked by a T-shaped toothed belt. A direct drive (DD) motor drives three clamping rods and positioning rollers via a screw and an inner rotating ring to jointly clamp the end cover. It also includes a telescopic pin, a hexagonal pin, and a clamping cylinder that can switch the locking state of the positioning rollers. This fixture achieves three-point linkage clamping driven by a single DD motor, mechanically securing the end cover in a surrounding manner, providing a complete mechanical clamping execution mechanism for end cover machining.

[0004] The control schemes for the aforementioned mechanical clamping actuators still face the following technical challenges: Due to the backlash in the mechanical transmission chain, minor deviations in the workpiece clamping position, and inconsistencies in the surface conditions of various contact points, some clamping points often contact the workpiece before others, making it difficult for the system to distinguish between overall clamping and local overload. This situation can easily lead to localized stress concentration causing workpiece damage, or be misjudged as clamping completion due to a point not actually making contact, resulting in workpiece loosening during processing. Furthermore, existing general control strategies lack effective dynamic discrimination mechanisms for distinguishing between transmission mechanism jamming and effective clamping, as well as for the timing interlocking with other safety actuators after clamping, making it difficult to ensure absolute safety and reliability of the processing under complex working conditions. Summary of the Invention

[0005] To address the above problems, this invention provides an intelligent clamping control method and device for a three-point linkage clamp for engine end caps. This method solves the long-standing technical problems in practical application scenarios where multiple clamping points are driven by a single motor, such as inaccurate clamping status judgment and difficulty in ensuring process safety. In particular, it is difficult to distinguish between overall clamping and local overload, and it is impossible to effectively identify transmission jamming and lack of dynamic safety interlocking mechanisms.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A first aspect of the present invention provides an intelligent clamping control method for a three-point linkage clamp on an engine end cover. The method includes: acquiring real-time clamping force parameters at three clamping points on the three-point linkage clamp; determining a minimum clamping force and a maximum clamping force at the three clamping points based on the real-time clamping force parameters; generating a continue clamping control criterion based on the minimum clamping force and a preset clamping requirement; and generating a stop clamping control criterion based on the maximum clamping force and a preset clamping upper limit. During the clamping control process of the drive motor, the continue clamping control criterion is used to determine whether to continue clamping. The lower limit for executing the clamping action is determined, and the upper limit for limiting the continued execution of the clamping action is determined by the stop clamping control criterion. If the minimum clamping force does not reach the preset clamping requirement and the maximum clamping force does not exceed the preset clamping upper limit, the drive motor is controlled to continue executing the clamping action. If the minimum clamping force reaches the preset clamping requirement and the maximum clamping force does not exceed the preset clamping upper limit, the drive motor is controlled to maintain the current clamping state. If the maximum clamping force reaches the preset clamping upper limit, the drive motor is controlled to stop the clamping action.

[0008] A second aspect of the present invention provides an intelligent clamping control device for a three-point linkage clamp on an engine end cover. The device includes: a clamping force information acquisition module for acquiring real-time clamping force parameters at three clamping points on the three-point linkage clamp; an extremum determination module for determining the minimum and maximum clamping forces among the three clamping points based on the real-time clamping force parameters; a criterion generation module for generating a continuing clamping control criterion based on the minimum clamping force and a preset clamping requirement, and generating a stopping clamping control criterion based on the maximum clamping force and a preset clamping upper limit; and a control decision module for, during the clamping control of the drive motor, using the continuing clamping force information acquisition module to acquire ... and an extremum determination module for determining the minimum and maximum clamping forces among the three clamping points based on the maximum clamping force and a preset clamping upper limit. The clamping control criterion serves as the lower limit for determining whether to continue the clamping action, and the clamping stop control criterion serves as the upper limit for restricting the continued execution of the clamping action. The drive control module is used to control the drive motor to continue the clamping action if the minimum clamping force does not reach the preset clamping requirement and the maximum clamping force does not exceed the preset clamping limit; if the minimum clamping force reaches the preset clamping requirement and the maximum clamping force does not exceed the preset clamping limit, control the drive motor to maintain the current clamping state; and if the maximum clamping force reaches the preset clamping limit, control the drive motor to stop the clamping action.

[0009] Compared with the prior art, the technical effects of the present invention are as follows:

[0010] By acquiring the real-time clamping force parameters of the three clamping points and determining the minimum and maximum clamping forces, an accurate data foundation is provided for subsequent control logic. Based on this, the continuing clamping control criteria and stopping clamping control criteria are generated respectively, realizing the quantitative discrimination of the clamping state and avoiding the uncertainty caused by the traditional solution that only relies on motor current or time stroke to determine the completion of clamping.

[0011] By using the clamping control criterion as the lower limit and the clamping stop criterion as the upper limit, the clamping process of the drive motor is subject to dual boundary constraints, which strictly limits the operating range of the drive motor to a safe and effective range. When the minimum clamping force is not met and the maximum clamping force is not exceeded, clamping continues; when the minimum clamping force is met and the maximum clamping force is not exceeded, the state is maintained; and when the maximum clamping force reaches the upper limit, it stops immediately. This achieves refined segmented control of the entire clamping process and avoids the problems of blind clamping or premature stopping that may be caused by single threshold control.

[0012] By using the minimum clamping force to characterize the contact state of the weakest link among the three points, and using whether this force meets the standard as the criterion for continuing clamping, it is ensured that all three clamping points can establish effective contact with the workpiece, thereby eliminating the hidden danger of "misjudging clamping completion upon single-point contact" caused by individual clamping points contacting the workpiece before other points, and ensuring the integrity of clamping.

[0013] By characterizing the single-point limit load with the maximum clamping force and using whether the force reaches the preset upper limit as the criterion for stopping clamping, independent overload protection for any clamping point is achieved; when the force at any clamping point reaches the upper limit, clamping stops immediately and unconditionally, effectively preventing local stress concentration caused by workpiece clamping deviation or uneven transmission, and avoiding elastic deformation or even permanent damage to the thin-walled end cap structure.

[0014] The coordinated monitoring of minimum and maximum clamping forces enables the system to achieve a dynamic balance between ensuring reliable contact at all three points and preventing single-point overload damage. The two work together to solve the technical problem of not being able to balance clamping integrity and safety in traditional solutions. Attached Figure Description

[0015] Figure 1 A flowchart of an intelligent clamping control method for a three-point linkage clamp for an engine end cover provided by the present invention;

[0016] Figure 2 The flowchart illustrates the process of zero-point calibration of the clamping force sensor and the determination of abnormalities in the intelligent clamping control method for the three-point linkage clamp of the engine end cover provided by the present invention.

[0017] Figure 3 The flowchart shows the process of determining the maximum and minimum values ​​and generating criteria after determining that all three clamping points have formed clamping contact in the intelligent clamping control method for the three-point linkage clamp of the engine end cover provided by the present invention.

[0018] Figure 4 The flowchart illustrates the calculation of force difference and determination of clamping imbalance faults in the intelligent clamping control method for the three-point linkage clamp of the engine end cover provided by this invention.

[0019] Figure 5 The flowchart illustrates the intelligent clamping control method for the three-point linkage clamp of the engine end cover provided by this invention, which determines effective clamping or transmission jamming based on the changing trends of current, position, and clamping force.

[0020] Figure 6 The flowchart illustrates the intelligent clamping control method for the three-point linkage clamp of the engine end cover provided by this invention, which controls the drive motor to continue performing the clamping action, maintain the current clamping state, or stop the clamping action.

[0021] Figure 7 The flowchart of the intelligent clamping control method for the three-point linkage clamp of the engine end cover provided by the present invention, which confirms the output of the locking drive signal after the motor is at zero speed and confirms the completion of locking;

[0022] Figure 8 The flowchart illustrates the intelligent clamping control method for the three-point linkage fixture of the engine end cover provided by this invention, which drives the solenoid valve based on the auxiliary claw activation signal and comprehensively judges and outputs a processing permission signal.

[0023] Figure 9 The flowchart illustrates the intelligent clamping control method for the three-point linkage fixture of the engine end cover provided by this invention, which involves revoking the allow machining signal and executing the feed hold and reset logic when monitoring multiple parameter anomalies.

[0024] Figure 10 The present invention provides a structural block diagram of an intelligent clamping control device for a three-point linkage clamp on an engine end cover. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solution, the present invention will be described in detail below with reference to embodiments. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0026] like Figure 1 The diagram shows a flowchart of an intelligent clamping control method for a three-point linkage clamp on an engine end cover according to an embodiment of the present invention. The method specifically includes:

[0027] Step S110: Obtain the real-time clamping force parameters of the three clamping points on the three-point linkage fixture, and determine the minimum and maximum clamping forces among the three clamping points based on the real-time clamping force parameters.

[0028] Real-time clamping force parameters reflect the magnitude of the interaction force between the three clamping points and the contact surface of the engine end cover, and are collected by force sensing devices integrated at the three clamping points of the fixture. In this embodiment, the three-point linkage fixture uses a direct drive motor as the power source, which synchronously drives the three positioning rollers to perform clamping actions via a mechanical transmission mechanism. Elastic strain gauges are respectively set at the clamping rod positions near the positioning roller shafts. Four strain gauges are attached to each elastic strain gauge and connected to form a full-bridge circuit, constituting three independent force detection units. During the clamping process, a unified reference excitation source provides a reference voltage for the three strain bridges. The differential signals output by each bridge are clamped, amplified by instruments, and low-pass filtered to form three comparable clamping force signals with the same reference, amplification factor, and filtering characteristics.

[0029] Specifically, the strain gauge bridge output signal can be amplified using a three-channel instrumentation amplifier group, and high-frequency noise can be filtered out using a low-pass filter group with the same cutoff frequency to obtain three analog voltage signals; alternatively, a thin force sensor can be installed between the positioning roller bearing housing and the clamping rod to directly read its output standard current or voltage signal. The system compares and calculates the above three signals to extract the minimum clamping force with the smallest value and the maximum clamping force with the largest value. This extraction process can be achieved by comparing the three force signals in real time using an analog minimum / maximum value selector and outputting the extreme values, or by converting the analog signals into digital signals and having the microprocessor execute a sorting algorithm to calculate the values. The minimum clamping force represents the weakest point under current stress, and the maximum clamping force represents the location of the local maximum stress; both serve as the input basis for subsequent control logic.

[0030] It should be noted that, as Figure 2 As shown, this embodiment of the invention provides a flowchart for sensor zero-point calibration and anomaly detection. Specifically, before determining the minimum and maximum clamping forces among the three clamping points based on real-time clamping force parameters, the invention further includes:

[0031] Step S210: Perform zero-point calibration on the clamping force sensors corresponding to the three clamping points, and determine whether the zero-point drift of each clamping force sensor exceeds the preset drift threshold.

[0032] Before powering on, resetting, or starting a new clamping cycle, the three positioning rollers are first controlled to be in an unloaded state without contacting the workpiece. The initial output values ​​of each clamping force sensor (i.e., the force sensing devices installed at each clamping point as described in step S110) are collected at this time, and these initial output values ​​are configured as the reference zero point. During the zero-point calibration process, power is supplied to the bridge reference excitation source in the three-point clamping force bridge sampling circuit, and the current voltage value output by the three-channel instrumentation amplifier group is read. The current voltage value is normalized by a hardware zeroing circuit or a digital subtraction algorithm to correct it to the zero reference, thereby eliminating the systematic errors introduced by the circuit static bias and the initial stress of the sensor.

[0033] After zero-point reference setting is completed, the output stability of each sensor under no-load conditions is continuously monitored, and the deviation between the actual output value and the reference zero point is calculated. This deviation is determined as the zero-point drift. To filter out instantaneous noise interference, this calculation process can, for example, be an averaging of the output values ​​from multiple consecutive sampling periods. A preset drift threshold is used as a criterion for determining the reliability of the sensor measurement loop. Its value is set comprehensively based on the sensor accuracy level, amplifier gain, and clamping force control accuracy requirements. For example, for high-precision clamping scenarios, this threshold can be set to 0.5% or 1% of full scale; or, by statistically analyzing the zero-point fluctuation data under historical normal operating conditions, three times the standard deviation can be selected as the threshold.

[0034] Step S230: If any zero-point drift exceeds the preset drift threshold, the clamping action is prohibited and a sensor abnormality signal is output.

[0035] The calculated zero-point drift is compared with a preset drift threshold in real time. When the zero-point drift is within the range defined by the preset drift threshold, the sensor zero point is determined to be normal. When the zero-point drift exceeds the range, abnormal drift is determined to exist. This comparison logic can be implemented, for example, using a window comparator.

[0036] Given that the engine end cover is a thin-walled component, accurate control of the clamping force is directly related to machining quality and workpiece safety. Any zero-point anomaly of any sensor may lead to distortion of the subsequently acquired minimum or maximum clamping force. If a sensor experiences positive drift, the system may misjudge that the clamping force at that point is too large and stop clamping prematurely, resulting in insufficient clamping force at other clamping points. If negative drift occurs, it may cause actual overload at that point, and the system may fail to trigger the stop protection in time.

[0037] Therefore, once the zero-point drift of any sensor at the three clamping points exceeds the preset drift threshold, the subsequent clamping control process is immediately locked. Specifically, any clamping commands are prohibited from being sent to the drive motor, ensuring that the motor cannot perform the clamping action, thereby preventing potential risks before the action is executed.

[0038] Simultaneously, a sensor anomaly signal is generated and output. This signal may manifest as illuminating a fault indicator light on the control panel, sending an alarm code to the CNC system, or displaying a specific sensor fault number on the human-machine interface. This sensor anomaly signal is used to alert the operator that the current clamping force detection circuit is unreliable and requires repair or recalibration. This avoids blindly performing machining operations when measurement data is unreliable, effectively solving the technical problems of inaccurate force measurement, false triggering of clamping control, or missed overload risks caused by zero-point drift.

[0039] Step S130: Generate a continuing clamping control criterion based on the minimum clamping force and the preset clamping requirements, and generate a stopping clamping control criterion based on the maximum clamping force and the preset clamping upper limit.

[0040] Preset clamping requirements refer to the minimum clamping force threshold required to ensure that the engine end cover does not loosen or shift during machining. These requirements are typically based on physical parameters such as workpiece weight, cutting force, and friction coefficient. Preset clamping upper limits refer to the maximum safe force threshold that the fixture's mechanical structure or the thin-walled structure of the engine end cover can withstand. These limits are typically based on factors such as the material's yield strength, the fixture's rated load, and a safety factor to prevent workpiece crushing. These two preset parameters can be determined, for example, through statistical analysis of successful clamping cases from historical machining data; or, alternatively, through finite element simulation analysis of workpiece deformation under different forces, combined with calculations based on engineering safety specifications.

[0041] The continued clamping control criterion is a logical judgment condition generated based on the minimum clamping force and preset clamping requirements, used to determine whether clamping force needs to continue to be applied. When the minimum clamping force does not reach the preset clamping requirements, it indicates that at least one of the three clamping points has not reached the force value required for reliable contact, and the motor must continue to be driven for clamping. The stop clamping control criterion is a logical judgment condition generated based on the maximum clamping force and preset clamping upper limit, used to prevent damage caused by excessive clamping force. When the maximum clamping force reaches or exceeds the preset clamping upper limit, it indicates that even if the contact force at other points is insufficient, the point currently under the greatest force is approaching the safety limit, and the clamping action must be stopped immediately. By generating these two criteria, the system constructs a dual-threshold control framework, using the minimum force as the lower limit constraint and the maximum force as the upper limit constraint, thereby clarifying the feasible domain of the clamping action at the control logic level.

[0042] Furthermore, such as Figure 3 The diagram shows a flowchart of a method for determining the maximum and minimum values ​​and generating criteria after all three clamping points have formed clamping contact, according to an embodiment of the present invention. Specifically, before determining the minimum and maximum clamping forces among the three clamping points based on real-time clamping force parameters, the method further includes:

[0043] Step S310: Determine whether all three clamping points are in clamping contact with the engine end cover.

[0044] Before determining the minimum and maximum clamping forces, it is first necessary to confirm that all three clamping points have established physical contact with the engine end cover. During the specific judgment process, real-time clamping force parameters corresponding to the three clamping points are acquired, and each clamping force parameter is compared with a preset contact threshold. The three clamping points correspond to three positioning rollers on the three-point linkage fixture of the engine end cover. When any positioning roller makes physical contact with the engine end cover and undergoes a slight deformation, the corresponding clamping force sensor output signal will exceed the contact threshold. By setting independent contact comparison logic for each clamping force signal, the single-point contact state can be accurately identified.

[0045] In practice, a first contact comparator, a second contact comparator, and a third contact comparator are used to distinguish the three clamping force signals. When the clamping force signal continuously exceeds the contact threshold and is confirmed by the debounce circuit, it is determined that the clamping point has formed a valid clamping contact. In this way, the timing process of the three clamping points contacting the engine end cover can be captured in real time, avoiding single-point suspension or false contact caused by mechanical linkage errors.

[0046] Step S330: Only after all three clamping points have formed clamping contact are the minimum clamping force and the maximum clamping force determined, and the criteria for continuing clamping control and stopping clamping control generated.

[0047] In practical applications, the state where all three clamping points are in clamping contact can be defined as the full contact state. The judgment results from the preceding steps are summarized and confirmed using full contact AND gate logic. A full contact confirmation signal is generated only when the outputs of the first, second, and third contact comparators are simultaneously valid. This full contact confirmation signal serves as a necessary permission condition to trigger the subsequent force closed-loop control process, unlocking the determination process of the minimum and maximum clamping forces, as well as the generation logic for continuing clamping control criteria and stopping clamping control criteria. If the full contact state is not achieved, for example, if only some clamping points are in contact, the calculation of control criteria based on force values ​​is prohibited to prevent misjudgment of clamping completion due to a surge in force at a single point. This design strictly isolates the contact confirmation stage from the force control stage, ensuring that the subsequently determined minimum clamping force accurately reflects the weak points of the clamping system, while ensuring that the maximum clamping force accurately characterizes the actual load state of the system, thereby effectively avoiding workpiece positioning offset or local overload deformation caused by incomplete contact.

[0048] By confirming the contact status of the three clamping points separately and only entering the force control stage after the full contact condition is met, the method provided by this embodiment of the invention effectively solves the misjudgment problem caused by differences in contact timing in three-point mechanical linkage clamps. This control logic of confirming contact first and then determining force value eliminates the interference of sudden changes in force signal on control decisions when a single point makes initial contact, ensuring the physical validity of the minimum and maximum clamping force parameters, and making the clamping process of the engine end cover more stable and reliable.

[0049] In one alternative implementation, such as Figure 4 As shown in the figure, this embodiment of the invention provides a flowchart for over-limit protection of three-point clamping force difference. The method includes:

[0050] Step S410: Calculate the force difference between the maximum clamping force and the minimum clamping force. The force difference is used to characterize the degree of force balance in the three-point clamping.

[0051] During the clamping process of the engine end cover, although the three clamping points are synchronously driven by the same drive motor through a mechanical linkage mechanism, the actual force applied to the three clamping points often varies significantly due to factors such as workpiece surface shape and position errors, inconsistent wear of the fixture positioning rollers, or uneven distribution of mechanical transmission clearance. If dual threshold control is applied based solely on the minimum and maximum clamping forces, a seemingly acceptable state may occur where the maximum clamping force does not exceed the upper limit while the minimum clamping force meets the requirements. However, in this case, the force on the three points is extremely uneven; for example, one point may experience excessive force while the other two points experience insufficient force. This state can easily lead to deformation, processing vibration, or localized crushing damage in thin-walled end covers.

[0052] To quantify the uniformity of this force distribution, the maximum and minimum clamping forces are extracted from three real-time acquired clamping force parameters, and the difference between them is calculated. This force difference serves as a key indicator, intuitively representing the degree of force balance in the current three-point clamping. This calculation process can be implemented at the circuit level, for example, using a differential amplifier. The electrical signals representing the maximum and minimum clamping forces are input to the non-inverting and inverting inputs of the differential amplifier, respectively, resulting in a voltage signal proportional to the difference between the two. This force difference reflects the dynamic force state of the mechanical linkage system when facing non-ideal workpieces and complex working conditions, providing a dimension other than force for subsequent judgment on whether continued clamping is permissible.

[0053] Step S430: Determine whether the force difference exceeds the preset imbalance threshold.

[0054] The preset imbalance threshold is a boundary condition defining whether the force applied during three-point clamping is within an acceptable uniform range. The determination of this preset imbalance threshold is based on factors including the material properties of the engine end cover, such as the deformation resistance of thin-walled aluminum alloy parts, machining accuracy requirements, and the stiffness characteristics of the fixture's mechanical structure. During system initialization or parameter configuration, the preset imbalance threshold can be obtained, for example, through experimental calibration: using standard specimens to conduct multiple clamping tests, statistically analyzing the maximum allowable force difference fluctuation range under the safe premise of ensuring machining quality without deformation or vibration, thereby determining the specific value of the preset imbalance threshold.

[0055] For example, the preset imbalance threshold can be set to 20% to 30% of the target force value corresponding to the preset clamping requirement, or it can be an absolute force value set according to the specific end cap model (such as 500N). The obtained force difference value is compared with the preset imbalance threshold. This comparison logic can be implemented, for example, through a window comparator or a conditional statement in the software. When the force difference value is less than or equal to the preset imbalance threshold, it indicates that the force difference of the three clamping points is within the allowable range of engineering, and is considered to be force balanced, meeting the preliminary conditions for continuing processing or maintaining the state; while when the force difference value is greater than the preset imbalance threshold, it indicates that there is a serious force imbalance in the current clamping state, and there is an abnormality in the mechanical system or workpiece position, and the corresponding protection mechanism must be triggered.

[0056] Step S450: If the force difference exceeds the preset imbalance threshold, the clamping action is unconditionally prohibited from continuing and a clamping imbalance fault signal is output.

[0057] Furthermore, when the judgment result indicates that the force difference has exceeded the preset imbalance threshold, it means that the current three-point linkage clamping mechanism has fallen into a state of severe force imbalance. At this time, even if the minimum clamping force has not reached the preset clamping requirement, or the maximum clamping force has not reached the preset clamping upper limit, the conventional dual-threshold control logic may incorrectly determine to continue clamping or holding the state. Such continued action will further aggravate the uneven force distribution, and will very likely lead to permanent deformation of the workpiece or local damage to the fixture.

[0058] Therefore, a priority rejection logic is introduced to address force difference exceeding limits. Once the force difference is detected to exceed a preset imbalance threshold, a highest-priority stop command is immediately generated, unconditionally prohibiting any further action that increases clamping force. At the execution level, this command forcibly cuts off the current output of the drive motor or puts it into a braking state, locking the current mechanical position.

[0059] Meanwhile, to prompt operator intervention, the system outputs a clamping imbalance fault signal. This signal can, for example, illuminate a fault indicator light on the control panel, display an alarm prompt on the human-machine interface, or send an interlocking pause request to the CNC system. This rigid constraint based on force difference effectively avoids quality hazards and equipment risks caused by simply pursuing force compliance while neglecting force balance. It complements the threshold control of minimum and maximum clamping forces, constructing a dual safety barrier that includes both force compliance and balanced force distribution.

[0060] Step S150: During the clamping control of the drive motor, the continuing clamping control criterion is used as the lower limit for deciding whether to continue the clamping action, and the stopping clamping control criterion is used as the upper limit for restricting the continued execution of the clamping action.

[0061] The drive motor, as the power source for performing the clamping action, provides the driving force to move the three positioning rollers towards the engine end cover and apply pressure. During the clamping control process, the system monitors the two control criteria generated above in real time. The "continue clamping" control criterion serves as the lower limit, meaning that as long as this criterion determines that the current minimum clamping force is insufficient, the system tends to maintain or initiate the clamping action to ensure that all clamping points eventually effectively contact the workpiece. The "stop clamping" control criterion serves as the upper limit, meaning that regardless of the state of the lower limit criterion, once this criterion determines that the maximum clamping force has reached its limit, the system will forcibly interrupt the clamping process to prioritize the safety of the workpiece and the fixture.

[0062] This control process can be implemented using state machine logic, for example: In the initial state, the system checks the clamping control criterion; if the condition is met, it enters the clamping state. During the clamping process, the system cyclically checks the stopping clamping control criterion in each control cycle; once triggered, it immediately jumps to the stopping state. Alternatively, it can be implemented using a dual comparator hardware circuit. The minimum clamping force signal and the lower threshold are connected to a hysteresis comparator, and the maximum clamping force signal and the upper threshold are connected to a window comparator. The output of the logic gate directly drives the enable or direction control terminal of the motor. Through this upper and lower limit coordinated control strategy, the system ensures sufficient clamping while strictly limiting the force range, avoiding the blind clamping or premature stopping problems that may occur with single threshold control.

[0063] In one alternative embodiment, such as Figure 5 The diagram shows a flowchart illustrating a method for determining effective clamping or transmission jamming based on the changing trends of current, position, and clamping force, according to an embodiment of the present invention. The method further includes:

[0064] Step S510: Obtain the operating status information of the drive motor of the three-point linkage fixture. The operating status information includes the drive motor current change information and the drive motor position change information.

[0065] Specifically, the operating status information of the drive motor can be collected in real time by a detection unit integrated into the drive motor control circuit. The drive motor current change information reflects the dynamic load condition of the motor's output torque. The acquisition process involves, for example, using a current sampling resistor connected in series in the drive motor phase circuit to collect the voltage signal and converting it into the current value via a differential amplifier. The drive motor position change information reflects the angular displacement of the motor rotor or the linear displacement of the linear actuator. The acquisition process involves, for example, reading the pulse count of an orthogonal encoder coaxially connected to the motor rotor and calculating the encoder position increment. The changing trends of these two physical quantities constitute the key dynamic basis for judging the load nature (such as elastic deformation contact or rigid mechanical blockage) during the clamping process, and the data acquisition frequency must be higher than the frequency of clamping force changes to accurately capture the instantaneous state.

[0066] Step S530: Within the same sampling period, simultaneously acquire the minimum clamping force change, the drive motor current change, and the drive motor position change.

[0067] Within a preset discrete time window (e.g., every 10 milliseconds or 50 milliseconds as a sampling period), the above three physical quantities are simultaneously sampled and differentially calculated. The change in minimum clamping force is obtained based on the difference between the minimum clamping force determined in the above embodiment and the value of the previous period in the current period. This data directly characterizes the force increase at the weakest clamping point in the fixture. The change in drive motor current is the difference between the motor current in the current period and the current in the previous period, used to characterize the change in load torque. The change in drive motor position is the difference between the current encoder count value and the count value in the previous period, used to characterize the mechanical feed. By analyzing the correlation of these three changes at the same time section, the specific physical source of the increase in motor load can be identified, thereby distinguishing whether the load originates from the reaction force generated by the contact of the workpiece or from the frictional resistance inside the transmission mechanism.

[0068] Step S550: When the change in drive motor current shows an increasing trend, the change in drive motor position is within a preset change window, and the change in minimum clamping force shows an increasing trend, the current clamping action is determined to be effective clamping.

[0069] The system uses multi-dimensional parameter-based collaborative logic to identify effective clamping processes. The preset change window is a pre-defined range for determining whether the motor displacement is reasonable. Its lower limit is used to exclude static or jammed states with insufficient displacement, while its upper limit is used to exclude states with excessive displacement leading to free travel or slippage.

[0070] The judgment logic requires three conditions to be met simultaneously: First, the change in drive motor current shows an increasing trend, indicating that the motor is working against the load; second, the change in drive motor position is within a preset change window, indicating that the motor is generating the expected and appropriate mechanical displacement, rather than being completely stationary or abnormally running away; finally, the change in minimum clamping force shows an increasing trend, indicating that the force on the third point (i.e., the point with the least force), which is the weakest link in the clamping system, is actually increasing with the motor's movement, eliminating the possibility of virtual contact where only one point is in contact while other points are not. The current clamping action is determined to be effective only when all three conditions are met simultaneously within the same sampling period, confirming that all three positioning rollers have established stable mechanical contact with the engine end cover and that the transmission mechanism is operating normally.

[0071] Step S570: When the change in drive motor current shows an increasing trend, the change in drive motor position is lower than the lower limit of the preset change window, and the change in minimum clamping force does not show an increasing trend, the current clamping action is determined to be transmission jamming, and the clamping action is stopped immediately.

[0072] Mechanical jamming faults in the transmission system are identified through specific combinations of abnormal patterns. The judgment logic focuses on the characteristic combination of motor output but mechanical transmission obstruction: on the one hand, the change in drive motor current shows an increasing trend, indicating that the motor controller has output a drive command and the motor is increasing its output in an attempt to overcome the resistance; on the other hand, the change in drive motor position is lower than the lower limit of the preset change window, indicating that although the current increases, the actual displacement of the motor shaft or actuator is extremely small or even close to zero, indicating that mechanical energy has not been effectively converted into kinetic energy; at the same time, the change in minimum clamping force does not show an increasing trend, indicating that the force at the clamping end does not increase with the increase in motor current, further confirming that the motor output power is not transmitted to the workpiece, but is obstructed by a link in the transmission chain (such as the screw, inner rotating ring, or T-shaped toothed belt).

[0073] When all three characteristics mentioned above occur simultaneously, the current clamping action is determined to be a transmission jam. At this time, in order to avoid motor burnout or mechanical damage due to continuous stalling, the drive motor is immediately controlled to stop the clamping action, thereby triggering the safety protection.

[0074] The aforementioned discrimination mechanism, which uses a cross-interlocking of three parameters—current, position, and minimum clamping force—upgrades static monitoring, which previously relied solely on a single threshold, to intelligent identification based on dynamic trends and multi-dimensional coupling relationships. This synergistic effect not only accurately identifies the true effective clamping state but also keenly detects hidden faults such as mechanical transmission jamming in the initial or during clamping process. This allows for timely intervention and protection before the motor overheats due to stall or the transmission components are damaged by overload, significantly improving the safety and reliability of the clamping process.

[0075] Step S170: If the minimum clamping force does not meet the preset clamping requirements and the maximum clamping force does not exceed the preset clamping limit, control the drive motor to continue performing the clamping action; if the minimum clamping force meets the preset clamping requirements and the maximum clamping force does not exceed the preset clamping limit, control the drive motor to maintain the current clamping state; if the maximum clamping force reaches the preset clamping limit, control the drive motor to stop the clamping action.

[0076] In practical applications, when no abnormal sensor signal or clamping imbalance fault signal is received, this step executes specific control actions on the drive motor based on the aforementioned criteria. The system divides the control process into three states according to the logical relationship between the minimum clamping force, the maximum clamping force, and two preset thresholds.

[0077] The first state is continued clamping, triggered when the minimum clamping force does not meet the preset clamping requirements and the maximum clamping force does not exceed the preset clamping limit. This indicates that at least one clamping point is under insufficient force and no point is overloaded. The system controls the drive motor to continue performing the clamping action, for example, by driving the motor to rotate at a preset low speed and constant current, and further compressing the workpiece through the transmission mechanism to increase the clamping force.

[0078] The second type is the holding state, triggered when the minimum clamping force reaches the preset clamping requirement and the maximum clamping force does not exceed the preset clamping upper limit. In this case, it indicates that the force on all clamping points meets the reliability requirements and is within the safe range. The system controls the drive motor to stop outputting drive torque and maintain the current state, for example, by turning off the three-phase inverter bridge output and relying on the self-locking property of mechanical transmission to maintain the clamping force.

[0079] The third state is the stopped clamping state, triggered when the maximum clamping force reaches the preset clamping limit. This indicates that the local force has reached the safety threshold. To prevent workpiece damage, the system immediately controls the drive motor to stop the clamping action, for example, by cutting off the motor power and triggering the brake, while simultaneously outputting a fault signal.

[0080] This segmented control strategy effectively solves the problem of local overload caused by single-point initial contact in the three-point linkage fixture, ensuring clamping reliability while maximizing the protection of the thin-walled structure of the engine end cover from damage.

[0081] Specifically, such as Figure 6 The diagram shows a flowchart of a method for controlling a drive motor to continue performing a clamping action, maintain the current clamping state, or stop the clamping action, according to an embodiment of the present invention. The method specifically includes:

[0082] Step S610: When the minimum clamping force does not meet the preset clamping requirements and the maximum clamping force does not exceed the preset clamping limit, control the drive motor to perform clamping at the first speed.

[0083] In the initial stage of the clamping process, the primary objective is to quickly bring the clamp close to the engine end cover to establish initial contact. The system monitors the minimum and maximum clamping forces in real time. When it is determined that the minimum clamping force has not yet met the preset clamping requirements, and the maximum clamping force, which serves as a safety boundary, has not reached the preset clamping upper limit, a control command for the first speed is output to the drive motor. The first speed is configured to a relatively high rotational speed, for example, 60% to 80% of the rated speed of the DD motor, aiming to shorten the idle travel approach time.

[0084] This stage focuses on quickly eliminating the gap between the positioning rollers and the workpiece, rather than finely adjusting the force value. Using a higher initial speed can significantly improve clamping efficiency. At the same time, the initial speed setting must ensure that the inertial impact of the mechanical transmission components during acceleration and braking is within a safe range to avoid damage to the thin-walled structure of the engine end cover.

[0085] Step S630: When the minimum clamping force reaches the preset clamping requirement for the first time, switch the clamping speed of the drive motor to a second speed that is lower than the first speed.

[0086] The moment the minimum clamping force is detected to first touch or exceed the preset clamping requirement, the speed switching logic is triggered, marking the transition of the clamping process from the rapid approach phase to the fine and stable phase. To avoid the actual clamping force far exceeding the target value due to inertial overshoot caused by high-speed operation, the clamping speed of the drive motor is reduced to a second speed. The second speed is strictly set to a value lower than the first speed, for example, it can be 10% to 30% of the first speed, or even an extremely low crawling speed.

[0087] By reducing the motor speed, the kinetic energy of the transmission system is significantly reduced, resulting in minimal mechanical inertial force when the motor stops. This keeps the overshoot of the clamping force within acceptable tolerances. This graded speed control strategy effectively solves the problem of balancing efficiency and accuracy in a single high-speed clamping mode, avoiding workpiece deformation or loss of positioning accuracy due to violent impacts.

[0088] Step S650: At the second speed, if the minimum clamping force falls below the preset clamping requirement again and the maximum clamping force does not exceed the preset clamping limit, then continue clamping at the second speed; if the minimum clamping force reaches the preset clamping requirement again and the maximum clamping force does not exceed the preset clamping limit, then control the drive motor to stop outputting and enter the holding state.

[0089] After switching to the second speed, the minimum clamping force may briefly drop due to the release of elastic deformation in the mechanical system, minor unevenness on the workpiece surface, or system damping oscillations. During this phase, closed-loop monitoring continues. When the minimum clamping force is detected to have fallen below the preset clamping requirement again, and the maximum clamping force is confirmed to be within the safe upper limit, it is determined that the current clamping force has not yet truly stabilized, and continued clamping force is required. At this point, the drive motor is controlled to maintain the second speed to continue the clamping action. This process involves fine compensation at low speed, gradually eliminating mechanical backlash and workpiece elastic rebound by continuously and minutely advancing the positioning rollers until the clamping force truly stabilizes within the target range.

[0090] During the continued clamping process at the second speed, when the minimum clamping force is detected to reach the preset clamping requirement again, and the maximum clamping force never exceeds the preset clamping upper limit, it is confirmed that all three clamping points have established stable and compliant contact, with balanced force and no overload. At this point, a stop command is sent to the drive motor, cutting off the motor output, allowing the clamp to enter the holding state relying on the self-locking characteristics of the mechanical transmission system or the motor's own holding torque. Through the dual confirmation mechanism of initial speed switching upon first achieving the target and subsequent confirmation of holding, false signals of achieving the target due to transient disturbances can be effectively filtered out, ensuring that the drive stops only after the clamping force is truly stable, thereby greatly improving the reliability of the final clamping state. Compared to the single-judgment start-up holding method, this control logic has stronger anti-interference capabilities and can adapt to the complex mechanical environment during engine end cover processing.

[0091] By introducing a re-compliance confirmation mechanism in the low-speed precision stage, the abstract motor speed control is combined with the specific clamping force feedback, making the clamping judgment process, which is originally easily affected by mechanical vibration and signal noise, logically rigorous and reliable, thus providing a solid positioning foundation for subsequent high-precision machining.

[0092] Furthermore, such as Figure 7 The diagram shows a flowchart illustrating how, according to an embodiment of the present invention, a locking drive signal is output after confirming the motor has reached zero speed, and the locking is confirmed to be complete. Specifically, after controlling the drive motor to maintain the current clamping state, the method further includes:

[0093] Step S710: Obtain the position feedback signal of the drive motor to confirm that the drive motor is in a zero-speed state.

[0094] The position feedback signal of the drive motor is the fundamental data characterizing the current angular position and motion state of the motor shaft. It originates from a high-resolution encoder installed at the end of the motor shaft or on the load side. Dynamic judgment is performed based on this position feedback signal, detecting whether the change in the position feedback value within a preset observation window converges to zero or falls below a preset motion-stationary threshold. If the position feedback value no longer shows incremental changes, and this stationary state persists for more than a preset debouncing time to rule out false judgments caused by low-speed motor crawling or mechanical vibration, then the drive motor is determined to be in a zero-speed state. Using motor stationarity as a rigid enable condition for the locking action effectively avoids mechanical collisions caused by the locking pin mechanism forcibly inserting during motor inertial sliding or micro-motion, thereby eliminating the risk of mechanical interference.

[0095] Step S730: After confirming that the drive motor is at zero speed, output a locking drive signal to the locking actuator.

[0096] After the prerequisite safety condition of the drive motor being at zero speed is met, an electrical command is sent to the locking actuator responsible for physically moving the positioning roller locking pin (such as a hexagonal pin or telescopic pin). This locking drive signal can be a pulse signal of specific voltage or current, a high-low level switching signal, or a bus communication command, used to drive locking actuators of the bistable micro electric actuator or electromagnetic actuator type. The output of the locking drive signal marks the switch of the control flow from the clamping force maintenance stage to the mechanical locking stage. Using the stationary state of the motor as the sole basis for triggering locking ensures the accuracy of the locking action initiation timing and the reliability of the system timing.

[0097] Step S750: Obtain the locking position feedback signal. When the locking position feedback signal is valid, confirm that locking is complete and output a locking completion signal.

[0098] After issuing the locking drive signal, the locking position feedback signal from the position sensor (such as a limit switch, proximity switch, or encoder) installed on the locking mechanism is acquired in real time. This signal indicates whether the locking pin has physically moved to the predetermined locking position. When a valid locking position feedback signal is detected, i.e., the sensor triggers an action or returns a specific position code to indicate that the locking pin is in place, the locking action is determined to be complete, and a locking completion signal is generated to notify the host computer or relevant control loop. Through the dual confirmation mechanism of drive command issuance and position feedback return, it is ensured that the locking action is actually executed at the physical level, rather than just remaining at the control command level. This improves the determinism and safety of the locking action and provides the necessary foundation for subsequent processing permission output.

[0099] One possible implementation is, such as Figure 8 The diagram shows a flowchart illustrating how an auxiliary gripper activation signal drives a solenoid valve, and a machining permission signal is output based on a comprehensive judgment, according to an embodiment of the present invention. After outputting a lock-up completion signal, the method further includes:

[0100] Step S810: Determine whether an auxiliary claw enable signal has been received.

[0101] In the machining of engine end caps, different workpieces have different requirements for clamping assistance. The auxiliary jaw activation signal is used to indicate whether the workpiece to be machined needs the intervention of the auxiliary jaw. For example, for machining a conventional arc end cap, the auxiliary jaw activation signal is usually in an invalid state; while for irregularly shaped end caps with bosses or reinforcing ribs, the system will send a high level or a specific communication message as a valid auxiliary jaw activation signal. Reading the state of this input port allows the method provided in this embodiment of the invention to automatically adapt to different workpiece shapes and avoid performing invalid actions when auxiliary jaws are not needed.

[0102] Specifically, the status of this signal can be determined by reading the machining process configuration information of the CNC system or the host controller. If the process parameters include an auxiliary gripper command, it is determined that an auxiliary gripper activation signal has been received; otherwise, it is determined that it has not been received. This judgment process realizes the automatic differentiation of machining modes, providing a basis for the execution of subsequent differentiated control logic.

[0103] Step S820: If no auxiliary claw enable signal is received, output an auxiliary claw qualified signal directly.

[0104] For workpieces with simple structures or those requiring no auxiliary grippers for fixation, the system enters a gripper-free mode. In this mode, the auxiliary gripper pass signal is assumed to be valid (e.g., logic high level), bypassing the auxiliary gripper detection process. This approach ensures that, without the need for auxiliary grippers, the processing permission generation conditions can be met solely by the main clamping force and locking status, avoiding disruption of the normal processing flow due to unnecessary auxiliary gripper status checks and improving system response efficiency.

[0105] Step S830: If an auxiliary claw activation signal is received, the auxiliary claw clamping solenoid valve is activated, and the auxiliary claw cylinder pressure feedback signal and the auxiliary claw clamping position feedback signal are obtained respectively.

[0106] When the workpiece has irregular protrusions or requires additional lateral support, the auxiliary jaw is used. A drive signal is output to the clamping solenoid valve of the auxiliary jaw, controlling the reversing valve to switch the air path direction, thereby driving the auxiliary jaw cylinder to extend and push the auxiliary jaw towards the workpiece surface. The drive signal can be in the form of a specific voltage pulse or level signal, the duration of which matches the response time of the solenoid valve to ensure that the cylinder receives a sufficient and stable air pressure source to complete the initial clamping action.

[0107] During the auxiliary claw's movement, the pressure state inside the cylinder and the physical position of the gripper are monitored in real time to establish a dual feedback mechanism. Specifically, the auxiliary claw cylinder pressure feedback signal comes from a pressure sensor installed in the cylinder's intake or return air path, characterizing the current chamber pressure value; the auxiliary claw gripper closing position feedback signal comes from a position sensor (such as a magnetic switch or proximity switch) installed on the gripper's key movement path, characterizing whether the gripper has reached the predetermined closed contact position.

[0108] The acquisition process of the two feedback signals mentioned above may include, for example, reading the 4mA-20mA current signal output by the pressure sensor through the analog input module and converting it into a gas pressure value, and scanning the level state of the limit switch at high frequency through the digital input module to capture the completion moment of the closing action. Through this coordinated mechanism of drive response + status reading, open-loop solenoid valve control can be transformed into closed-loop process monitoring.

[0109] Step S840: When the pressure feedback signal is within the preset pressure window and the closed position feedback signal is valid, output the auxiliary claw qualified signal.

[0110] The preset pressure window is a set pressure range used to determine whether the cylinder pressure meets the requirements for establishing a stable clamping force without overload. The lower limit of the preset pressure window is determined by converting the minimum thrust required to overcome the friction of the auxiliary claw mechanism and maintain claw closure using the cylinder piston area. The upper limit of the preset pressure window is set comprehensively based on the cylinder's rated working pressure and the maximum clamping force that the workpiece can withstand, to avoid excessive clamping force damaging the irregular structure of the end cap. As an example, and not a limitation, for an auxiliary claw cylinder with a cylinder diameter of 20mm, the pressure window can be set from 0.3MPa to 0.6MPa.

[0111] Alternatively, statistical analysis can be performed on pressure fluctuation data under historical normal working conditions, and the mean ± 3 times the standard deviation can be selected as the window boundary.

[0112] The closed position feedback signal is used to indicate whether the gripper has physically closed. For example, a magnetic switch or proximity sensor can be installed at the gripper's closed limit position, and the sensor outputs a high-level active signal when the gripper moves to that position.

[0113] By using this logic of pressure and position, abnormal situations such as insufficient air pressure but no contact between the gripper and the workpiece (virtual clamping) or insufficient air pressure (insufficient clamping force) can be effectively filtered out, thus improving the accuracy of clamping status judgment.

[0114] Step S850: When the pressure feedback signal exceeds the preset pressure window or the closed position feedback signal is invalid, cancel the auxiliary claw qualified signal.

[0115] When the auxiliary gripper is activated, if the cylinder pressure is detected to be lower than the lower limit of the preset pressure window, it indicates a possible air leak or insufficient air supply; if the pressure is higher than the upper limit of the window, it indicates a possible mechanical jam or overload; if the closed position feedback signal remains invalid, it indicates that the gripper has failed to reach the expected position. Any of these situations indicates that the auxiliary gripper is in an abnormal or malfunctioning state. In this case, the output of the auxiliary gripper pass signal should be immediately revoked or rejected (e.g., set to a logic low level) to prevent the generation of machining permission. This safety mechanism prevents the machining process from starting when the fixture is unreliable, effectively avoiding workpiece drift or the generation of machining defects.

[0116] Step S860: Output a machining permission signal only when both the locking completion signal and the auxiliary jaw pass signal are valid.

[0117] The locking completion signal, generated by the preceding steps, indicates that the mechanical locking mechanism of the main positioning roller is in place. The machining permission signal is the final start authorization command sent to the CNC equipment. By incorporating the locking completion signal and the auxiliary jaw pass signal into the safety condition AND gate for logical operations, the machining permission signal is generated and output only when both signals are simultaneously valid, thereby removing the restriction on the cyclic start end of the CNC equipment. This dual interlocking mechanism ensures that failure of either the main clamping path (locked state) or the auxiliary clamping path (auxiliary jaw state) will be safely intercepted, achieving full-dimensional confirmation of the engine end cover clamping status and guaranteeing the safety of the machining process.

[0118] Furthermore, such as Figure 9 As shown, after outputting the machining enable signal, this embodiment of the invention provides a flowchart of canceling the machining enable signal and executing feed hold and reset logic when monitoring for multiple parameter anomalies. The method further includes:

[0119] Step S910: During the processing, continuously monitor the minimum clamping force, maximum clamping force, locking completion signal, and auxiliary jaw pass signal.

[0120] During the cutting operation of the CNC equipment, key status parameters of the clamping system are tracked through a real-time sampling loop. The monitored objects include the minimum and maximum clamping forces at the three clamping points determined in the aforementioned steps, as well as the locking completion signal and the auxiliary jaw pass signal.

[0121] Among them, the minimum clamping force characterizes the reliability of the weakest link in the clamping system and is used to prevent the workpiece from loosening as a whole due to single-point loosening; the maximum clamping force is used to monitor whether there is local overload or workpiece deformation accumulation caused by cutting force; the locking completion signal is used to confirm whether the mechanical locking mechanism is effectively locked to resist the risk of locking pin withdrawal caused by machining vibration; the auxiliary jaw qualified signal is used to confirm the air pressure and position status of the auxiliary clamping mechanism to prevent the auxiliary jaw from being accidentally released.

[0122] The synchronous monitoring of the above four types of state variables constructs a full-dimensional logical image of the fixture's physical state within the machining cycle, ensuring that any abnormality in any stage can be captured in a timely manner. The sampling frequency of this continuous monitoring process is no less than the interpolation cycle of the CNC equipment, for example, set to sample once every 10 milliseconds to ensure the real-time nature of abnormal response.

[0123] Step S930: When the minimum clamping force drops below the under-force threshold of the machining state, or the maximum clamping force exceeds the overload threshold of the machining state, or the lock-up completion signal fails, or the auxiliary jaw pass signal fails, immediately cancel the allow machining signal and output a feed hold signal to the CNC equipment to stop the feed action.

[0124] Based on real-time acquired status parameters, anomaly detection logic is executed. The under-force threshold and overload threshold for machining are set according to the machining process safety boundary, and their values ​​are calculated based on the cutting force simulation results and the safety margin of the material's yield strength. For example, the under-force threshold for machining can be set to 80% of the nominal clamping force to identify clamping loosening tendencies caused by cutting forces; the overload threshold for machining can be set to 110% of the preset clamping upper limit or the stress value of the workpiece material's allowable compressive stress, aiming to prevent plastic deformation of thin-walled end caps.

[0125] It should be noted that the under-force threshold in the machining state is lower than the preset clamping requirement in step S130, and the overload threshold in the machining state is higher than the preset clamping upper limit in step S130. That is, the clamping force is allowed to fluctuate within a wider range during the machining process to avoid frequent triggering of protection due to normal cutting force disturbances, which would affect machining efficiency. At the same time, when the tolerance window is exceeded, it indicates that the clamping state has substantially deteriorated, triggering feed hold to ensure safety.

[0126] Specifically, the anomaly determination uses an OR logic operation, meaning that if any of the above four conditions is triggered, it is determined that the machining safety conditions have been lost. Specifically, if the minimum clamping force is lower than the under-force threshold in the machining state, it indicates that the fixture may become partially loose due to workpiece vibration or cutting force impact; if the maximum clamping force exceeds the overload threshold in the machining state, it indicates that the clamping deformation is close to or exceeds the safety limit, posing a risk of crushing the workpiece or damaging the fixture; if the locking completion signal fails, it indicates that the mechanical locking mechanism may experience unlocking displacement under severe vibration; if the auxiliary claw qualified signal fails, it indicates that the clamping force or position of the pneumatic auxiliary claw deviates from the safe range.

[0127] Once any abnormal condition is detected, the previously output processing permission signal is immediately revoked. This revocation is achieved by disconnecting the dry contact of the processing permission output terminal or setting the permission level signal low. Since this signal is directly connected to the cyclic start permission terminal of the CNC machine, it forcibly cuts off the CNC machine's continued operation permission.

[0128] Simultaneously, a feed hold signal is output to the CNC equipment. This signal is latched and output through a feed hold latch and connected to the feed hold terminal of the CNC equipment. This allows for the immediate interruption of the feed motion of each axis without cutting off the spindle power. This dual interlocking mechanism ensures that the relative movement between the tool and workpiece is forcibly frozen at the first moment of abnormal clamping, preventing safety accidents such as workpiece ejection, tool breakage, or dimensional deviations due to clamping failure. This process can be triggered by a high-priority hardware interrupt signal to ensure that software-level control commands do not delay the activation of the feed hold signal.

[0129] Step S950: Obtain the spindle stop status signal of the CNC equipment.

[0130] After outputting the feed hold signal, the safety confirmation and reset process begins. The spindle stop status signal, as a key safety signal internally fed back by the CNC equipment, is used to confirm that the spindle rotation has completely stopped. This signal can be obtained by reading the spindle zero speed flag in the CNC system's programmable logic controller interface, or by detecting the toggle state of the spindle driver's Ready Signal.

[0131] The core purpose of acquiring this signal is to ensure that the rotary tool has come to a complete stop before re-executing the clamping action. If the spindle is still rotating while driving the fixture, the rotary tool may collide with the workpiece being repositioned, or scratch the workpiece surface during the fixture's re-clamping process. Therefore, the validity of the spindle stop status signal is a prerequisite for allowing subsequent reset operations. This step continuously polls the spindle status until an acknowledgment signal indicating that the spindle speed is zero or below a safe threshold is received.

[0132] Step S970: The clamping action is only allowed to be re-executed after the spindle stop status signal is valid and a manual reset signal is received.

[0133] The final recovery logic of the safety interlock relies on two core conditions: first, the spindle stop status signal obtained in the aforementioned steps is valid, confirming that the physical hazard has been eliminated; second, a manual reset signal is received, confirming that the operator has intervened and that the site is safe. The manual reset signal can be input via a physical button, a human-machine interface confirmation touch, or an authorized remote reset command. For example, the level signal generated when the operator presses the fault reset / allow reclamp button on the control panel after inspecting the site and troubleshooting.

[0134] The system employs an AND gate logic condition: the internal feed hold latch is reset only when both the spindle stop signal (indicating physical safety) and the manual reset signal (indicating personnel confirmation of safety) are simultaneously satisfied, thereby re-enabling the clamping action. The manual reset signal mandates operator intervention to inspect and confirm the fault location, preventing the system from automatically restarting without troubleshooting. This combined mechanism of spindle zero-speed interlock and manual confirmation ensures that any clamping abnormality can only be resolved under conditions of complete stillness and human confirmation before the machining restriction is lifted, thus eliminating the risk of catastrophic accidents caused by the fixture moving while the spindle is rotating.

[0135] Through the above process, this invention establishes a complete closed-loop safety system, from real-time monitoring to emergency braking and interlock reset, after the processing permit takes effect. This system utilizes the rigid constraints of the feed holding signal and the spindle state to dynamically block and safely release potential clamping faults during processing, significantly improving the inherent safety level of the engine end cover processing.

[0136] The specific working principle of this invention is as follows: This invention collects real-time clamping force parameters at three clamping points using a force sensing device, extracts the minimum and maximum clamping forces, and generates continued clamping control criteria and stopped clamping control criteria based on these. During clamping, the system uses the continued clamping criterion as the lower limit: when the minimum clamping force is insufficient, the motor is allowed to continue advancing; and the stopped clamping criterion as the upper limit: once the maximum clamping force reaches the preset upper limit, it is unconditionally forced to stop, regardless of the lower limit status. Simultaneously, the system cross-compares the increments of the minimum clamping force, motor current, and position within the same sampling period. When all three increase synchronously, it is determined to be effective clamping; when the current increases but the position and force do not change accordingly, it is determined to be transmission jamming and immediately stops. Furthermore, the system also calculates the difference between the maximum and minimum forces in real time; when the difference exceeds the imbalance threshold, clamping is unconditionally prohibited. After clamping is completed, the locking pin and auxiliary jaw status are sequentially executed; only when both are effective is a processing permission signal output. During the machining process, the clamping force and various safety signals are continuously monitored. In case of any abnormality, the feed holding latch is immediately triggered, and re-clamping is only allowed after the spindle stops and is manually reset. Thus, this invention achieves intelligent clamping control of a three-point linkage fixture through dual threshold coordination of "lower limit drive and upper limit cutoff", three-dimensional cross-verification discrimination, and multi-level safety interlocking.

[0137] Furthermore, an exemplary embodiment of the present invention also provides an intelligent clamping control device for a three-point linkage clamp for an engine end cover.

[0138] Figure 10 This diagram schematically illustrates the structural block diagram of an intelligent clamping control device for a three-point linkage clamp on an engine end cover according to an exemplary embodiment of the present invention. (Refer to...) Figure 10 According to an exemplary embodiment of the present invention, the intelligent clamping control device 1000 for the three-point linkage clamp of the engine end cover may include: a clamping force information acquisition module 1010, an extreme value determination module 1030, a criterion generation module 1050, a control decision module 1070, and a drive control module 1090.

[0139] Specifically, the clamping force information acquisition module 1010 can be used to acquire real-time clamping force parameters of the three clamping points on the three-point linkage fixture; the extreme value determination module 1030 can be used to determine the minimum and maximum clamping forces among the three clamping points based on the real-time clamping force parameters; the criterion generation module 1050 can be used to generate a continuing clamping control criterion based on the minimum clamping force and preset clamping requirements, and to generate a stopping clamping control criterion based on the maximum clamping force and preset clamping upper limit; the control decision module 1070 can be used to continue clamping during the clamping control process of the drive motor. The control criterion serves as the lower limit for deciding whether to continue the clamping action, and the clamping stop control criterion serves as the upper limit for restricting the clamping action from continuing. The drive control module 1090 can be used to control the drive motor to continue the clamping action if the minimum clamping force does not reach the preset clamping requirement and the maximum clamping force does not exceed the preset clamping limit; control the drive motor to maintain the current clamping state if the minimum clamping force reaches the preset clamping requirement and the maximum clamping force does not exceed the preset clamping limit; and control the drive motor to stop the clamping action if the maximum clamping force reaches the preset clamping limit.

[0140] Since the functional modules of the intelligent clamping control device for the three-point linkage clamp of the engine end cover in this embodiment of the invention are the same as those in the above method embodiment, they will not be described again here.

[0141] It should be noted that, in this document, the terms "comprising," "including," and any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Specific examples have been used in this document to illustrate the principles and implementation methods of the present invention. These examples are merely for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be pointed out that, due to the limitations of written expression and the objective existence of infinite specific structures, those skilled in the art can make several improvements, modifications, or variations without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the concept and technical solution of the present invention to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. An intelligent clamping control method for a three-point linkage clamp on an engine end cover, characterized in that, The method includes: Obtain the real-time clamping force parameters of the three clamping points on the three-point linkage fixture, and determine the minimum and maximum clamping forces among the three clamping points based on the real-time clamping force parameters; A continuing clamping control criterion is generated based on the minimum clamping force and the preset clamping requirement, and a stopping clamping control criterion is generated based on the maximum clamping force and the preset clamping upper limit. During the clamping control of the drive motor, the continued clamping control criterion is used as the lower limit for deciding whether to continue the clamping action, and the stopped clamping control criterion is used as the upper limit for restricting the continued execution of the clamping action. If the minimum clamping force does not meet the preset clamping requirement and the maximum clamping force does not exceed the preset clamping limit, the drive motor is controlled to continue performing the clamping action; if the minimum clamping force meets the preset clamping requirement and the maximum clamping force does not exceed the preset clamping limit, the drive motor is controlled to maintain the current clamping state; if the maximum clamping force reaches the preset clamping limit, the drive motor is controlled to stop the clamping action.

2. The method according to claim 1, characterized in that, Before determining the minimum and maximum clamping forces among the three clamping points based on the real-time clamping force parameters, the method further includes: Zero-point calibration is performed on the clamping force sensors corresponding to the three clamping points, and it is determined whether the zero-point drift of each clamping force sensor exceeds a preset drift threshold. If any of the zero-point drift amounts exceeds the preset drift threshold, the clamping action is prohibited and a sensor abnormality signal is output.

3. The method according to claim 1, characterized in that, Before determining the minimum and maximum clamping forces among the three clamping points based on the real-time clamping force parameters, the method further includes: Determine whether each of the three clamping points forms clamping contact with the engine end cover; The minimum clamping force and the maximum clamping force are determined only after all three clamping points have formed clamping contact, and the continued clamping control criterion and the stop clamping control criterion are generated.

4. The method according to claim 1, characterized in that, The method further includes: Calculate the force difference between the maximum clamping force and the minimum clamping force, and the force difference is used to characterize the degree of force balance in the three-point clamping. Determine whether the force difference exceeds a preset imbalance threshold; If the force difference exceeds the preset imbalance threshold, the clamping action is unconditionally prohibited from continuing and a clamping imbalance fault signal is output.

5. The method according to claim 1, characterized in that, The method further includes: Obtain the operating status information of the drive motor that drives the three-point linkage fixture, the operating status information including drive motor current change information and drive motor position change information; Within the same sampling period, the minimum clamping force change, the drive motor current change, and the drive motor position change are simultaneously acquired. When the change in the current of the drive motor shows an increasing trend, the change in the position of the drive motor is within a preset change window, and the change in the minimum clamping force shows an increasing trend, the current clamping action is determined to be effective clamping. When the change in the drive motor current shows an increasing trend, the change in the drive motor position is lower than the lower limit of the preset change window, and the change in the minimum clamping force does not show an increasing trend, the current clamping action is determined to be a transmission jam, and the clamping action is stopped immediately.

6. The method according to claim 1, characterized in that, Controlling the drive motor to continue performing the clamping action, maintain the current clamping state, or stop the clamping action includes: When the minimum clamping force does not reach the preset clamping requirement and the maximum clamping force does not exceed the preset clamping limit, the drive motor is controlled to perform clamping at the first speed; Once the minimum clamping force reaches the preset clamping requirement for the first time, the clamping speed of the drive motor is switched to a second speed, which is lower than the first speed. At the second speed, if the minimum clamping force falls below the preset clamping requirement again and the maximum clamping force does not exceed the preset clamping limit, then clamping continues at the second speed; if the minimum clamping force reaches the preset clamping requirement again and the maximum clamping force does not exceed the preset clamping limit, then the drive motor is controlled to stop outputting and enter the holding state.

7. The method according to claim 1, characterized in that, After controlling the drive motor to maintain the current clamping state, the method further includes: Obtain the position feedback signal of the drive motor to confirm that the drive motor is at zero speed; After confirming that the drive motor is at zero speed, a locking drive signal is output to the locking actuator; Obtain the locking position feedback signal. When the locking position feedback signal is valid, confirm that locking is complete and output a locking completion signal.

8. The method according to claim 7, characterized in that, After the output latch-up completion signal, the following is also included: Determine whether an auxiliary claw activation signal has been received; If the auxiliary claw activation signal is not received, the auxiliary claw qualified signal will be output directly. If the auxiliary claw activation signal is received, the auxiliary claw clamping solenoid valve is driven to operate, and the auxiliary claw cylinder pressure feedback signal and the auxiliary claw clamping position feedback signal are obtained respectively. When the pressure feedback signal is within the preset pressure window and the closed position feedback signal is valid, the auxiliary claw qualified signal is output. When the pressure feedback signal exceeds the preset pressure window or the closed position feedback signal is invalid, the auxiliary claw qualified signal is cancelled. A machining permission signal is output only when both the locking completion signal and the auxiliary jaw pass signal are valid.

9. The method according to claim 8, characterized in that, After the output processing permission signal, it also includes: During the processing, the minimum clamping force, the maximum clamping force, the locking completion signal, and the auxiliary claw qualification signal are continuously monitored. When the minimum clamping force drops below the under-force threshold of the machining state, or the maximum clamping force exceeds the overload threshold of the machining state, or the locking completion signal fails, or the auxiliary jaw qualified signal fails, the allow machining signal is immediately revoked, and a feed holding signal is output to the CNC equipment to stop the feed action. Acquire the spindle stop status signal of the CNC equipment; The clamping action is only allowed to be re-executed after the spindle stop status signal is valid and a manual reset signal is received.

10. An intelligent clamping control device for a three-point linkage clamp on an engine end cover, characterized in that, The device includes: The clamping force information acquisition module is used to acquire the real-time clamping force parameters of the three clamping points on the three-point linkage fixture; The extreme value determination module is used to determine the minimum and maximum clamping forces among the three clamping points based on the real-time clamping force parameters. The criterion generation module is used to generate a continuing clamping control criterion based on the minimum clamping force and the preset clamping requirements, and to generate a stopping clamping control criterion based on the maximum clamping force and the preset clamping upper limit. The control decision module is used to determine whether to continue the clamping action during the clamping control process of the drive motor, using the continued clamping control criterion as the lower limit basis for deciding whether to continue the clamping action, and using the stop clamping control criterion as the upper limit basis for limiting the continued execution of the clamping action. The drive control module is configured to: control the drive motor to continue performing the clamping action if the minimum clamping force does not meet the preset clamping requirement and the maximum clamping force does not exceed the preset clamping limit; control the drive motor to maintain the current clamping state if the minimum clamping force meets the preset clamping requirement and the maximum clamping force does not exceed the preset clamping limit; and control the drive motor to stop the clamping action if the maximum clamping force reaches the preset clamping limit.

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