Pneumatic brake detection device and method of numerical control machine tool direct drive rotary table

Abstract

The invention belongs to the technical field of numerical control machine tools, and particularly relates to a pneumatic brake detection device and method for a numerical control machine tool direct drive rotary table, and the device comprises a brake housing, a brake disc, a brake seat, a piston rear cover, a rotary table connecting shaft, and a control box. The brake base and the piston rear cover are fixedly installed on the brake shell through bolts, and the brake shell, the brake base and the piston rear cover are rotationally connected with the rotary table connecting shaft through ball bearings. A gap of 0.5 mm to 2 mm and parallelism are kept between the magnetic ruler and the reading head, the brake gas circuit pipe and the loosening gas circuit pipe are independently connected and can respectively monitor pressure changes of a brake cavity and a loosening cavity in real time, and the digital pressure sensor is electrically connected with the control box and converts physical pressure into digital signals to be transmitted to the control box.

Description

Technical Field

[0001] This invention relates to the field of CNC machine tool technology, and in particular to a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool. Background Technology

[0002] Direct-drive rotary tables for CNC machine tools use torque motors to directly drive the spindle, eliminating mechanical transmission links such as gears. They have significant advantages such as zero backlash, fast response, and high precision, making them a core component for high-end precision machining. However, direct-drive rotary tables do not have a self-locking function when the power is off or in non-cutting states. Therefore, they usually need to be equipped with a pneumatic brake. This brake uses compressed air to push a piston to press against the brake disc to lock the rotary table spindle, ensuring positioning accuracy and safety during machining.

[0003] In the existing technology, the detection of the pneumatic brake status of a direct-drive turntable mainly relies on a simple pressure switch to monitor the air pressure in the air circuit. However, this single detection method cannot truly reflect the wear condition of the brake pads or the actual displacement state of the piston, and there is a detection blind spot. If the brake pads are worn and the gap increases, even if the air pressure is normal, the actual braking force may be insufficient, thus causing safety hazards. Summary of the Invention

[0004] In the existing technology, relying on simple pressure switches to monitor air pressure in the air circuit cannot accurately reflect the wear condition of the brake pads or the actual displacement state of the piston, resulting in a detection blind spot. If the brake pads wear and the gap increases, even if the air pressure is normal, the actual braking force may be insufficient, thus causing a safety hazard. This invention proposes a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool.

[0005] This invention proposes a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool, comprising a brake housing, a brake disc, a brake seat, a piston rear cover, a rotary table connecting shaft, and a control box. The brake disc is fixedly installed to the rotary table connecting shaft by bolts. The brake seat and the piston rear cover are both fixedly installed to the brake housing by bolts. The brake housing, the brake seat, and the piston rear cover are all rotatably connected to the rotary table connecting shaft by ball bearings.

[0006] The brake housing is equipped with a pneumatic braking mechanism, which includes a main piston. The main piston, after moving, cooperates with the brake seat to press the brake disc and stop its rotation.

[0007] A detection system is provided on the surface of the piston rear cover. The detection system is correspondingly set with the pneumatic brake mechanism and is used to detect the working status of the pneumatic brake mechanism in real time. The detection system includes a piston displacement detection unit and an air pressure unit. The piston displacement detection unit includes a reading head and a magnetic scale. The reading head reads the displacement signal of the magnetic scale in a non-contact manner to accurately measure the actual displacement of the piston of the pneumatic brake mechanism. The air pressure unit includes a digital pressure sensor. The digital pressure sensor is used to collect the pressure signals of the brake air path and the release air path in the piston chamber of the piston rear cover.

[0008] Preferably, the pneumatic brake mechanism further includes a connecting rod, which is slidably connected to the groove of the piston rear cover connecting block via a sealing ring. One end of the connecting rod is fixedly installed with the main piston, and the other end of the connecting rod is fixedly installed with a secondary piston. The secondary piston is slidably connected to the groove of the piston rear cover connecting block via a sealing ring, and the main piston is slidably connected to the groove of the brake seat connecting block via a sealing ring.

[0009] Through the above technical solution, the connecting rod is a rigid connecting component between the main piston and the auxiliary piston. Its function is to accurately and synchronously transmit the linear movement of the auxiliary piston in the piston chamber to the main piston. This rigid connection ensures that the movements of the two pistons are completely consistent, avoiding mechanical jamming or efficiency loss caused by asynchronous movements. A sealing ring is used to slide and seal between the connecting rod and the piston rear cover connecting block, ensuring that the connecting rod can slide freely while effectively preventing high-pressure gas from leaking from the piston chamber, thus ensuring the airtightness and working pressure stability of the braking mechanism. By adding an auxiliary piston next to the main piston, in which the auxiliary piston is slidably connected to the piston rear cover through a sealing ring, and the main piston is also sealed to the brake seat through a sealing ring, the airtightness is ensured. At the same time, the two are connected by the connecting rod to form a double-piston structure, which optimizes the axial dimension of the entire braking mechanism and makes the structure more compact. At the same time, the double-piston structure can distribute the force on a single piston, improving the reliability and service life of the entire braking mechanism.

[0010] Preferably, a piston measuring rod is fixedly installed on the outer side of the auxiliary piston. One end of the piston measuring rod passes through the piston rear cover and extends to its outside. The circumferential surface of the piston measuring rod is slidably connected to the inner wall of the groove of the piston rear cover through a sealing ring. A baffle is fixedly installed on the outer surface of the piston measuring rod. The baffle is located outside the piston rear cover and is used to limit the displacement distance of the piston measuring rod.

[0011] Through the above technical solution, the piston measuring rod is a rigid rod connected to the auxiliary piston. Its function is to amplify and transmit the small linear displacement of the auxiliary piston to the outside of the piston rear cover so that the magnetic scale can easily detect the movement of the piston. By installing non-contact sensors such as the magnetic scale on the outside of the piston rear cover, the sensors are prevented from directly contacting the moving parts, thereby reducing wear, improving measurement accuracy and sensor lifespan. The baffle is a limiting device at the end of the piston measuring rod. Its function is to prevent the piston measuring rod from excessively extending or retracting during movement, thereby protecting the sensor and mechanical structure from damage. When the piston moves to its limit position, the baffle will physically contact the piston rear cover, limiting its further movement.

[0012] Preferably, the piston displacement detection unit further includes a connecting seat, which is fixedly installed on the outer surface of the piston rear cover by bolts. The reading head is fixedly installed on the support plate of the connecting seat, and the magnetic scale is fixedly installed on the outer surface of the piston measuring rod. The magnetic scale is located outside the baffle. The magnetic scale and the reading head maintain a gap of 0.5mm to 2mm and parallelism. The signal input terminal of the control box is electrically connected to the signal output terminal of the reading head through a wire.

[0013] Through the above technical solution, the connector provides a stable and robust mounting platform for the reading head, ensuring that the reading head will not loosen or shift during machine tool operation. Maintaining a gap of 0.5mm to 2mm and parallelism between the magnetic scale and the reading head is crucial for the normal operation of the non-contact magnetic grating sensor. The appropriate gap ensures that the sensor will not make physical contact, while good parallelism ensures the accuracy and linearity of the measurement signal. Connecting the signal output terminal of the reading head to the signal input terminal of the control box through wires realizes the digital transmission of displacement signals, facilitating subsequent signal processing and analysis by the control box.

[0014] Preferably, the air pressure unit further includes a brake air pipe, which is fixedly connected to the brake air line of the piston chamber of the piston rear cover. The release air line of the piston chamber of the piston rear cover is fixedly connected to the release air pipe. The ends of the brake air pipe and the release air pipe are threadedly connected to the digital pressure sensor through sealant. The signal input terminal of the control box is electrically connected to the signal output terminal of the digital pressure sensor through a wire.

[0015] Through the above technical solution, the independent connection of the brake air line and the release air line allows for real-time monitoring of pressure changes in the brake chamber and the release chamber, and can more sensitively detect malfunctions of the electromagnetic reversing valve, such as incomplete reversal or leakage in one side of the air line. The pressure sensor is connected to the brake air line and the release air line respectively with sealed threads using sealant, ensuring the airtightness of the air line connection and guaranteeing the convenience of disassembly and maintenance. At the same time, the use of sealant eliminates the risk of micro-leakage at the thread gap, ensuring that the collected pressure signal truly reflects the pressure inside the chamber, rather than a false value caused by leakage. Through the electrical connection between the digital pressure sensor and the control box, the physical pressure is converted into a digital signal and transmitted to the control box. The control box can establish a spatiotemporal correlation model of pressure-displacement, providing multi-dimensional data support for intelligent health diagnosis.

[0016] Preferably, a method for detecting the pneumatic brake of a CNC machine tool direct-drive rotary table includes the following steps: S1: Mechanical installation and displacement reference self-test: Fix the brake housing to the stationary base of the machine tool, connect the turntable connecting shaft to the power output end of the direct drive turntable, and after the device is powered on, the control box controls the pneumatic brake mechanism to drive the piston measuring rod to extend until the auxiliary piston touches the limit surface of the piston rear cover. Use the reading head to read the first limit position signal of the magnetic scale, and use this as a reference to calibrate the zero point and full scale of the piston displacement, and confirm that the signal communication between the reading head and the magnetic scale is normal. S2: Air circuit sealing and pressure reference calibration: The brake air circuit pipe and the release air circuit pipe are respectively connected to the external air source and the solenoid reversing valve controlled by the control box. The control box switches the air circuit direction by controlling the solenoid reversing valve. The preset test pressure is injected into the piston chamber of the piston rear cover through the brake air circuit pipe or the release air circuit pipe. During the pressure holding period, the pressure change is monitored by the digital pressure sensor, and the pressure holding pressure drop rate is calculated. If the pressure drop rate is lower than the preset leakage threshold, the air circuit sealing test is deemed qualified. At the same time, based on the current pressure values ​​of the brake air circuit and the release air circuit, the zero drift and gain error of the pressure sensor are calibrated to complete the initialization of the air circuit detection system. S3: Synchronous Timing Data Acquisition and Standardization: Upon receiving a braking or releasing action trigger command, the control box synchronously acquires the brake air circuit pressure signal, the release air circuit pressure signal, and the piston displacement signal, converting the acquired raw signals into a time-series standardized sequence of actual pressure values. and standardized actual displacement value sequence ; S4: Dynamic Process Feature Extraction: For braking actions, extract features from pressure value sequences. and displacement value sequence Extract the following feature groups: Feature group F1: Stable pressure value Displacement stability value And the pressure rises from the initial value to the preset pressure threshold. Time required ; Feature group F2: Displacement changes from the initial value to a preset displacement threshold Time required And the time difference between the pressure stabilization moment and the displacement stabilization moment. ; For the release action, from the pressure value sequence and displacement value sequence Extract the following feature groups: Feature group F3: Stable pressure value Displacement stability value And the pressure drops from the initial value to the preset pressure threshold. Time required ; Feature group F4: Displacement reverts from the initial value to a preset displacement threshold. Time required And the time difference between the pressure stabilization moment and the displacement stabilization moment. ; Among them, the preset pressure threshold , and preset displacement threshold , These are fixed or proportional values ​​preset based on the normal operating parameters of the system; S5: State health assessment based on multi-feature fusion: The extracted dynamic correlation features are input into the pre-trained state assessment model; The condition assessment model outputs a health score. and the corresponding status labels; among which, ,when Greater than or equal to the first health threshold When the status is successful, the status label is: Success; when Less than the first health threshold but greater than or equal to the second health threshold At that time, the status label is: Warning; When the health level is below the second health threshold, the status label is: Failure; The condition assessment model is obtained by training historical normal action data and historical abnormal action data through machine learning algorithms. It is used to learn the nonlinear mapping relationship between multiple features and the health status of the braking system. S6: Result Output and Decision Execution: Based on the status label output in step S5, control the CNC machine tool direct drive rotary table to perform the corresponding operation. If successful, continue running; if an alarm is triggered, log is recorded and the speed can be selectively reduced; if a failure occurs, an alarm is immediately triggered and the machine is safely stopped.

[0017] Preferably, the pressure value at the start of the pressure holding process is obtained. and the pressure value at the end of the pressure holding period Calculate the pressure change: ; Calculate the holding time: ; Pressure drop rate Through the formula: The calculation yielded the result.

[0018] Through the above technical solutions This refers to the absolute pressure loss during the pressure holding period. The absolute time for maintaining pressure. The pressure leakage rate per unit time is calculated by... Establish a time-independent standardized indicator that triggers an alarm when the leakage rate exceeds a threshold. This eliminates interference from the pressure holding time setting and improves the scientific rigor and robustness of airtightness testing.

[0019] Preferably, in step S4, the extracted correlation features further include benchmark error features, and the calculation logic is as follows: The pressure value sequence of the current action and displacement value sequence Compared with the pre-stored reference pressure curve and reference displacement curve Align the curves and calculate the difference between the current curve and the baseline curve at the corresponding time points. Calculate the square of the difference, and then take the square root of the average of the sum of all the squared differences to obtain the root mean square value of the pressure error. and root mean square value of displacement error .

[0020] Using the above technical solutions, the moment of action triggering is taken as the zero point, or alignment is achieved through the Dynamic Time Warping (DTW) algorithm, thereby calculating the difference between the current curve and the reference curve at the corresponding time point, and the reference pressure curve. and reference displacement curve Typically, this data is generated after the equipment has undergone factory testing or maintenance, by collecting signals from multiple normal braking / releasing actions and taking the average value. This is the square root of the average squared deviation of the current motion curve from the standard curve at each time point. The focus is on shape differences throughout the entire dynamic process. Even if the final braking pressure and displacement are normal, if abnormal shaking, crawling, or response lag occurs during the process, It can also detect these issues sensitively, which helps in the early detection of progressive faults such as uneven piston wear and minor blockages in the air passage.

[0021] Preferably, in step S5, the health score The calculation employs a weighted fusion approach, combining model probability with physical error correction, as detailed below: The probability value output by the state assessment model that belongs to the success category is... Then the health score Calculated using the following formula: in, , , The preset weighting coefficients, and ; and These are the preset maximum allowable pressure error and displacement error thresholds, respectively.

[0022] The above technical solution, which combines data-driven and mechanistic models to calculate a comprehensive health score, is highly reliable. The fusion formula utilizes both AI intelligence and physical rules as a safety baseline, adjusting weights accordingly. - Engineers can flexibly adjust the sensitivity of the evaluation model according to the actual application scenario, thereby improving the adaptability of the algorithm.

[0023] Preferably, in step S4, feature extraction further includes time lag features: time lag Displacement value sequence The moment when the mid-displacement first exceeds the preset displacement noise threshold , and pressure value sequence The moment when the medium pressure first exceeds the preset pressure noise threshold The difference, that is .

[0024] The above technical solution can be specifically used to test the mechanical transmission efficiency and friction characteristics of braking mechanisms, wherein if An increase usually indicates an increase in static friction, such as due to insufficient lubrication, hardened seals, or increased mechanical resistance. This is related to slow pressure build-up in the air path. There is a difference, and also before the braking torque drops significantly or the displacement is insufficient, Wear and tear often changes first, and monitoring this characteristic can provide early warning of wear and tear, preventing minor problems from developing into serious mechanical failures.

[0025] The beneficial effects of this invention are as follows: 1. By setting up a pneumatic braking mechanism to press the brake disc and stop its rotation, an auxiliary piston is added next to the main piston and connected to it by a connecting rod, forming a double-piston structure. This disperses the force on a single piston, improving the reliability and service life of the entire braking mechanism. The piston measuring rod amplifies the small linear displacement of the auxiliary piston and transmits it to the outside of the piston rear cover, so that the reading head can easily detect the piston's movement through a magnetic scale. The baffle is a limiting device at the end of the piston measuring rod, which prevents the piston measuring rod from excessively extending or retracting during movement, thereby protecting the sensor and mechanical structure from damage. When the piston moves to its limit position, the baffle will make physical contact with the piston rear cover, limiting its further movement. This solves the technical problem of relying on a simple pressure switch to monitor the air pressure in the air circuit, which cannot accurately reflect the wear of the brake pads or the actual displacement state of the piston, resulting in a detection blind spot. If the brake pads wear and the gap increases, even if the air pressure is normal, the actual braking force may be insufficient, thus causing safety hazards.

[0026] 2. By setting up a detection system, the connector provides a stable and robust mounting platform for the reading head, ensuring that the reading head will not loosen or shift during machine tool operation. A gap of 0.5mm to 2mm and parallelism are maintained between the magnetic scale and the reading head to ensure the accuracy and linearity of the measurement signal. A wire connects the signal output end of the reading head to the signal input end of the control box, realizing the digital transmission of displacement signals and facilitating subsequent signal processing and analysis by the control box. Independent connections between the brake air circuit and the release air circuit allow for real-time monitoring of pressure changes in the brake chamber and release chamber respectively. The electrical connection between the digital pressure sensor and the control box converts physical pressure into digital signals, which are then transmitted to the control box. The control box can establish a spatiotemporal correlation model of pressure and displacement, providing multi-dimensional data support for intelligent health diagnosis. This solves the technical problem of relying on simple pressure switches to monitor air circuit pressure, which cannot accurately reflect the wear condition of brake pads or the actual displacement state of the piston, resulting in detection blind spots. If brake pad wear leads to increased gaps, even if the air pressure is normal, the actual braking force may be insufficient, thus causing safety hazards. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool, as proposed in this invention. Figure 2 This is a perspective view of the piston rear cover structure of a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool proposed in this invention. Figure 3 This is an exploded view of the main piston structure of a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool, as proposed in this invention. Figure 4This is a perspective view of the brake disc structure of a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool, as proposed in this invention. Figure 5 This is a perspective view of the auxiliary piston structure of a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool, as proposed in this invention. Figure 6 This is a perspective view of the reading head structure of a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool, as proposed in this invention. Figure 7 This is a flowchart of the pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool proposed in this invention. Figure 8 This is a flowchart of the system initialization and calibration of a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool, as proposed in this invention. Figure 9 This is a flowchart illustrating the dynamic feature extraction of a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool, as proposed in this invention. Figure 10 This is a flowchart illustrating the health assessment and decision-making process of a pneumatic brake detection device and method for a direct-drive rotary table of a CNC machine tool, as proposed in this invention.

[0028] In the diagram: 1. Brake housing; 11. Brake disc; 12. Brake seat; 13. Piston rear cover; 14. Turntable connecting shaft; 15. Control box; 2. Connecting rod; 21. Main piston; 22. Secondary piston; 3. Piston measuring rod; 31. Baffle; 4. Connecting seat; 41. Reading head; 42. Magnetic scale; 5. Brake air line; 51. Release air line; 52. Digital pressure sensor. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] Reference Figures 1-10 A pneumatic brake testing device and method for a direct-drive rotary table of a CNC machine tool includes a brake housing 1, a brake disc 11, a brake seat 12, a piston rear cover 13, a rotary table connecting shaft 14, and a control box 15. The brake disc 11 is fixedly installed to the rotary table connecting shaft 14 by bolts. The brake seat 12 and the piston rear cover 13 are both fixedly installed to the brake housing 1 by bolts. The brake housing 1, the brake seat 12, and the piston rear cover 13 are all rotatably connected to the rotary table connecting shaft 14 by ball bearings.

[0031] like Figure 2-4As shown, in order to press down the brake disc 11 and stop its rotation, a pneumatic braking mechanism is provided inside the brake housing 1. The pneumatic braking mechanism includes a main piston 21. After the main piston 21 moves, it cooperates with the brake seat 12 to press down the brake disc 11 and stop its rotation.

[0032] Specifically, to ensure the airtightness and working pressure stability of the braking mechanism, the pneumatic braking mechanism also includes a connecting rod 2. The connecting rod 2 is slidably connected to the groove of the connecting block of the piston rear cover 13 via a sealing ring. One end of the connecting rod 2 is fixedly installed with the main piston 21, and the other end of the connecting rod 2 is fixedly installed with the auxiliary piston 22. The auxiliary piston 22 is slidably connected to the groove of the connecting block of the piston rear cover 13 via a sealing ring. The main piston 21 is slidably connected to the groove of the connecting block of the brake seat 12 via a sealing ring. The connecting rod 2 is a rigid connecting component between the main piston 21 and the auxiliary piston 22. Its function is to accurately and synchronously transmit the linear movement of the auxiliary piston 22 in the piston chamber to the main piston 21. This rigid connection ensures that the movements of the two pistons are completely consistent, avoiding asynchronous movements. To prevent mechanical jamming or efficiency loss, a sealing ring is used to slide between the connecting rod 2 and the piston rear cover 13 connecting block. This ensures that the connecting rod 2 can slide freely while effectively preventing high-pressure gas from leaking from the piston chamber, thus ensuring the airtightness and working pressure stability of the braking mechanism. By adding a secondary piston 22 next to the main piston 21, the secondary piston 22 is slidably connected to the piston rear cover 13 through a sealing ring. The main piston 21 is also sealed to the brake seat 12 through a sealing ring to ensure airtightness. At the same time, the two are connected by a connecting rod to form a double piston structure, which optimizes the axial dimension of the entire braking mechanism and makes the structure more compact. In addition, the double piston structure can distribute the force on a single piston, improving the reliability and service life of the entire braking mechanism.

[0033] Specifically, to prevent the piston measuring rod 3 from excessively extending or retracting during operation, a piston measuring rod 3 is fixedly installed on the outer side of the auxiliary piston 22. One end of the piston measuring rod 3 penetrates the piston rear cover 13 and extends to its outside. The circumferential surface of the piston measuring rod 3 is slidably connected to the inner wall of the groove of the piston rear cover 13 through a sealing ring. A baffle 31 is fixedly installed on the outer surface of the piston measuring rod 3. The baffle 31 is located outside the piston rear cover 13 and is used to limit the displacement distance of the piston measuring rod 3. The piston measuring rod 3 is a rigid rod connected to the auxiliary piston 22, and its function is to amplify and... The movement of the piston is transmitted to the outside of the piston rear cover 13 so that the magnetic scale 42 can easily detect the movement of the piston. By installing non-contact sensors such as the magnetic scale 42 on the outside of the piston rear cover 13, the sensors are prevented from directly contacting the moving parts, thereby reducing wear, improving measurement accuracy and sensor lifespan. The baffle 31 is a limiting device at the end of the piston measuring rod 3. Its function is to prevent the piston measuring rod 3 from excessively extending or retracting during movement, thereby protecting the sensor and mechanical structure from damage. When the piston moves to the limit position, the baffle 31 will make physical contact with the piston rear cover 13, limiting its further movement.

[0034] like Figure 5-6 As shown, in order to accurately measure the actual displacement of the piston of the pneumatic brake mechanism, a detection system is provided on the surface of the piston rear cover 13. The detection system is set in correspondence with the pneumatic brake mechanism and is used to detect the working status of the pneumatic brake mechanism in real time. The detection system includes a piston displacement detection unit and an air pressure unit. The piston displacement detection unit includes a reading head 41 and a magnetic scale 42. The reading head 41 reads the displacement signal of the magnetic scale 42 in a non-contact manner to accurately measure the actual displacement of the piston of the pneumatic brake mechanism.

[0035] Specifically, to ensure that the reading head 41 does not loosen or shift during machine tool operation, the piston displacement detection unit also includes a connecting seat 4. The connecting seat 4 is bolted to the outer surface of the piston rear cover 13. The reading head 41 is fixedly mounted on the support plate of the connecting seat 4. The magnetic scale 42 is fixedly mounted on the outer surface of the piston measuring rod 3. The magnetic scale 42 is located outside the baffle 31. A gap of 0.5mm to 2mm and parallelism are maintained between the magnetic scale 42 and the reading head 41. The signal input terminal of the control box 15 is electrically connected to the signal output terminal of the reading head 41 through a wire. The connecting seat 4 provides support for the reading head 41. A stable and robust mounting platform is provided to ensure that the reading head 41 will not loosen or shift during machine tool operation. A gap of 0.5mm to 2mm and parallelism are maintained between the magnetic scale 42 and the reading head 41. This is the key to the normal operation of the non-contact magnetic grating sensor. The appropriate gap ensures that the sensor will not make physical contact, while good parallelism ensures the accuracy and linearity of the measurement signal. The signal output terminal of the reading head 41 is connected to the signal input terminal of the control box 15 through wires, realizing the digital transmission of displacement signal, which facilitates the subsequent signal processing and analysis of the control box 15.

[0036] The air pressure unit includes a digital pressure sensor 52, which is used to collect pressure signals of the brake air passage and the release air passage in the piston chamber of the piston rear cover 13.

[0037] Specifically, to monitor the pressure changes in the brake chamber and release chamber in real time, the air pressure unit also includes a brake air pipe 5. The brake air pipe 5 is fixedly connected to the brake air path of the piston chamber in the piston rear cover 13. The release air path of the piston chamber in the piston rear cover 13 is fixedly connected to a release air pipe 51. The ends of both the brake air pipe 5 and the release air pipe 51 are sealed to the digital pressure sensor 52 via sealant. The signal input terminal of the control box 15 is electrically connected to the signal output terminal of the digital pressure sensor 52 via a wire. The independent connection of the brake air pipe 5 and the release air pipe 51 allows for real-time monitoring of the pressure changes in the brake chamber and release chamber separately, and can provide more sensitive detection. If a fault is found in the electromagnetic reversing valve, such as incomplete reversal or leakage in one side of the air circuit, the pressure sensor is connected to the brake air circuit pipe 5 and the release air circuit pipe 51 respectively through a threaded sealant to ensure the airtightness of the air circuit connection and to ensure the convenience of disassembly and maintenance. At the same time, the use of sealant eliminates the risk of micro-leakage at the thread gap, ensuring that the collected pressure signal truly reflects the pressure inside the cavity, rather than a false value caused by leakage. Through the electrical connection between the digital pressure sensor 52 and the control box 15, the physical pressure is converted into a digital signal and transmitted to the control box 15. The control box 15 can establish a spatiotemporal correlation model of pressure-displacement, providing multi-dimensional data support for intelligent health diagnosis.

[0038] like Figure 7-10As shown, a method for testing the pneumatic brake of a CNC machine tool direct-drive rotary table includes the following steps: S1: Mechanical installation and displacement reference self-test: Fix the brake housing 1 to the stationary base of the machine tool, connect the turntable connecting shaft 14 to the power output end of the direct drive turntable, and after the device is powered on, the control box 15 controls the pneumatic brake mechanism to drive the piston measuring rod 3 to extend until the auxiliary piston 22 touches the limiting surface of the piston rear cover 13. Use the reading head 41 to read the first limit position signal of the magnetic scale 42, and use this as a reference to calibrate the zero point and full scale of the piston displacement, and confirm that the signal communication between the reading head 41 and the magnetic scale 42 is normal. S2: Air circuit sealing and pressure reference calibration: The brake air circuit pipe 5 and the release air circuit pipe 51 are respectively connected to the external air source and the solenoid reversing valve controlled by the control box 15. The control box 15 switches the air circuit direction by controlling the solenoid reversing valve, and fills the piston chamber of the piston rear cover 13 with the preset test pressure through the brake air circuit pipe 5 or the release air circuit pipe 51. During the pressure holding period, the pressure change is monitored by the digital pressure sensor 52, and the pressure holding pressure drop rate is calculated. If the pressure drop rate is lower than the preset leakage threshold, the air circuit sealing test is deemed qualified. At the same time, based on the current pressure values ​​of the brake air circuit and the release air circuit, the zero drift and gain error of the pressure sensor are calibrated to complete the initialization of the air circuit detection system. S3: Synchronous Timing Data Acquisition and Standardization: Upon receiving a braking or releasing action trigger command, the control box 15 synchronously acquires the brake air circuit pressure signal, the release air circuit pressure signal, and the piston displacement signal, converting the acquired raw signals into a time-series standardized actual pressure value sequence. and standardized actual displacement value sequence ; S4: Dynamic Process Feature Extraction: For braking actions, extract features from pressure value sequences. and displacement value sequence Extract the following feature groups: Feature group F1: Stable pressure value Displacement stability value And the pressure rises from the initial value to the preset pressure threshold. Time required ; Feature group F2: Displacement changes from the initial value to a preset displacement threshold Time required And the time difference between the pressure stabilization moment and the displacement stabilization moment. ; For the release action, from the pressure value sequence and displacement value sequence Extract the following feature groups: Feature group F3: Stable pressure value Displacement stability value And the pressure drops from the initial value to the preset pressure threshold. Time required ; Feature group F4: Displacement reverts from the initial value to a preset displacement threshold. Time required And the time difference between the pressure stabilization moment and the displacement stabilization moment. ; Among them, the preset pressure threshold , and preset displacement threshold , These are fixed or proportional values ​​preset based on the normal operating parameters of the system; S5: State health assessment based on multi-feature fusion: The extracted dynamic correlation features are input into the pre-trained state assessment model; The condition assessment model outputs a health score. and the corresponding status labels; among which, ,when Greater than or equal to the first health threshold When the status is successful, the status label is: Success; when Less than the first health threshold but greater than or equal to the second health threshold At that time, the status label is: Warning; When the health level is below the second health threshold, the status label is: Failure; The condition assessment model is obtained by training historical normal action data and historical abnormal action data through machine learning algorithms. It is used to learn the nonlinear mapping relationship between multiple features and the health status of the braking system. S6: Result Output and Decision Execution: Based on the status label output in step S5, control the CNC machine tool direct drive rotary table to perform the corresponding operation. If successful, continue running; if an alarm is triggered, log is recorded and the speed can be selectively reduced; if a failure occurs, an alarm is immediately triggered and the machine is safely stopped.

[0039] Specifically, obtain the pressure value at the start of the pressure holding process. and the pressure value at the end of the pressure holding period Calculate the pressure change: ; Calculate the holding time: ; Pressure drop rate Through the formula: Calculated; This refers to the absolute pressure loss during the pressure holding period. The absolute time for maintaining pressure. The pressure leakage rate per unit time is calculated by... Establish a time-independent standardized indicator that triggers an alarm when the leakage rate exceeds a threshold. This eliminates interference from the pressure holding time setting and improves the scientific rigor and robustness of airtightness testing.

[0040] Specifically, in step S4, the extracted correlation features also include the baseline error features, and the calculation logic is as follows: The pressure value sequence of the current action and displacement value sequence Compared with the pre-stored reference pressure curve and reference displacement curve Align the curves and calculate the difference between the current curve and the baseline curve at the corresponding time points. Calculate the square of the difference, and then take the square root of the average of the sum of all the squared differences to obtain the root mean square value of the pressure error. and root mean square value of displacement error ; Using the moment of action triggering as the zero point, or aligning it using the Dynamic Time Warping (DTW) algorithm, the difference between the current curve and the baseline curve at the corresponding time point is calculated, resulting in the baseline pressure curve. and reference displacement curve Typically, this data is generated after the equipment has undergone factory testing or maintenance, by collecting signals from multiple normal braking / releasing actions and taking the average value. This is the square root of the average squared deviation of the current motion curve from the standard curve at each time point. The focus is on shape differences throughout the entire dynamic process. Even if the final braking pressure and displacement are normal, if abnormal shaking, crawling, or response lag occurs during the process, It can also detect these issues sensitively, which helps in the early detection of progressive faults such as uneven piston wear and minor blockages in the air passage.

[0041] Specifically, in step S5, the health score The calculation employs a weighted fusion approach, combining model probability with physical error correction, as detailed below: The probability value output by the state assessment model that belongs to the success category is... Then the health score Calculated using the following formula: in, , , The preset weighting coefficients, and ; and These are the preset maximum allowable pressure error and displacement error thresholds, respectively; By combining data-driven and mechanistic models to calculate a comprehensive health score, the system demonstrates high reliability. The fusion formula leverages the intelligence of AI while using physical rules as a safety baseline, adjusting weights accordingly. - Engineers can flexibly adjust the sensitivity of the evaluation model according to the actual application scenario, thereby improving the adaptability of the algorithm.

[0042] Specifically, in step S4, feature extraction also includes time lag features: time lag Displacement value sequence The moment when the mid-displacement first exceeds the preset displacement noise threshold , and pressure value sequence The moment when the medium pressure first exceeds the preset pressure noise threshold The difference, that is ; It can be specifically used to test the mechanical transmission efficiency and friction characteristics of braking mechanisms, where if An increase usually indicates an increase in static friction, such as due to insufficient lubrication, hardened seals, or increased mechanical resistance. This is related to slow pressure build-up in the air path. There is a difference, and also before the braking torque drops significantly or the displacement is insufficient, Wear and tear often changes first, and monitoring this characteristic can provide early warning of wear and tear, preventing minor problems from developing into serious mechanical failures.

[0043] Working principle: Command triggering and air circuit switching: When the CNC machine tool needs to brake, the control system sends a braking command to the control box 15. The control box 15 controls the internal electromagnetic reversing valve to switch the high-pressure gas from the external air source to the piston chamber of the piston rear cover 13 through the brake air circuit pipe 5. The high-pressure gas enters the chamber and pushes the auxiliary piston 22 to move towards the brake disc 11. Due to the rigid connection of the connecting rod 2, the movement of the auxiliary piston 22 is accurately and synchronously transmitted to the main piston 21, ensuring that the two move in unison without lag or jamming. The auxiliary piston 22 transmits the displacement to the outside through the piston measuring rod 3. Braking and Displacement Detection: The main piston 21 moves and eventually contacts the brake disc 11, pressing it down and creating friction between it and the brake disc 11 fixed on the turntable connecting shaft 14, thus braking and preventing the turntable from rotating. Simultaneously, the piston measuring rod 3 retracts inward with the auxiliary piston 22. The reading head 41 reads the displacement signal of the magnetic scale 42 fixed on the piston measuring rod 3 in real time using a non-contact method, accurately measuring the actual stroke of the piston and transmitting this displacement signal, i.e., the displacement value sequence. The signal is transmitted to the control box 15. The digital pressure sensor 52 collects the brake pressure signal, i.e., the pressure value sequence, in real time through the brake air pipe 5. It is also transmitted to the control box 15; Status assessment and decision-making: The control box 15 synchronously collects pressure and displacement signals, extracts features such as pressure stability value, displacement stability value, response time, etc., inputs the features into the pre-trained model, calculates the health score H. If H is determined to be successful, the brake is effective and the turntable stops. If it is a warning or failure, the speed reduction or shutdown protection is executed according to the preset strategy. Command triggering and air circuit switching: When the brake needs to be released, the control system sends a release command to the control box 15. The control box 15 controls the electromagnetic reversing valve to switch the high-pressure gas through the release air circuit pipe 51 to the other side of the piston chamber. The pressure in the piston chamber is released or reversed and built up. The auxiliary piston 22 moves back under the action of air pressure. The connecting rod 2 and the main piston 21 retract synchronously, driving the piston measuring rod 3 to extend. Brake release and displacement detection: When the main piston 21 disengages from the brake disc 11, the pressure on the brake disc 11 disappears, the brake is released, and the turntable can rotate freely. The reading head 41 and the digital pressure sensor 52 also collect displacement and pressure signals in real time during the release process and transmit them to the control box 15. Status assessment and decision-making: Control box 15 analyzes the characteristics of the release process, such as pressure drop time and displacement return time, and also conducts a health assessment to ensure that the release action is normal and there is no jamming or incomplete release. During the pressure holding test, the system records the initial and final pressures and calculates the pressure change. and holding time Then, the pressure reduction rate can be obtained. This rate index eliminates the interference of time factors and accurately determines whether the gas circuit sealing meets the standard by quantifying the degree of leakage per unit time. In the dynamic feature extraction stage, the system aligns the collected current pressure and displacement curves with the pre-stored reference curves in time, calculates the root mean square difference between the two at each time point, and by comparing the waveform similarity, this step can effectively capture jitter or distortion in the data and discover early progressive faults that cannot be reflected by a single value. The system performs in-depth analysis of the action details and calculates the time difference between the start of displacement and the establishment of pressure. This hysteresis feature is specifically used to quantify the transmission efficiency and friction characteristics of mechanical systems, and sensitively reflects potential mechanical wear hazards such as poor lubrication or increased resistance. During the evaluation phase, the system integrates the above indicators and performs a fusion calculation, fusing the success probability, pressure error term, and displacement error term output by the machine learning model according to preset weights to generate a health score between 0 and 1. This method, which combines AI-powered intelligent judgment with physical error correction, can more comprehensively reflect the health status of the system and provide a scientific basis for final decision-making.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A pneumatic brake detection device for a direct-drive rotary table of a CNC machine tool, comprising a brake housing (1), a brake disc (11), a brake seat (12), a piston rear cover (13), a rotary table connecting shaft (14), and a control box (15), characterized in that: The brake disc (11) is fixedly installed to the turntable connecting shaft (14) by bolts. The brake seat (12) and the piston rear cover (13) are both fixedly installed to the brake housing (1) by bolts. The brake housing (1), the brake seat (12) and the piston rear cover (13) are all rotatably connected to the turntable connecting shaft (14) by ball bearings. The brake housing (1) is provided with a pneumatic brake mechanism, which includes a main piston (21). After the main piston (21) moves, it cooperates with the brake seat (12) to press the brake disc (11) and stop it from rotating. A detection system is provided on the surface of the piston rear cover (13). The detection system is correspondingly set with the pneumatic brake mechanism and is used to detect the working status of the pneumatic brake mechanism in real time. The detection system includes a piston displacement detection unit and an air pressure unit. The piston displacement detection unit includes a reading head (41) and a magnetic ruler (42). The reading head (41) reads the displacement signal of the magnetic ruler (42) in a non-contact manner to accurately measure the actual displacement of the piston of the pneumatic brake mechanism. The air pressure unit includes a digital pressure sensor (52). The digital pressure sensor (52) is used to collect the pressure signals of the brake air path and the release air path of the piston chamber of the piston rear cover (13).

2. The pneumatic brake detection device for a direct-drive rotary table of a CNC machine tool according to claim 1, characterized in that: The pneumatic brake mechanism also includes a connecting rod (2), which is slidably connected to the groove of the connecting block of the piston rear cover (13) through a sealing ring. One end of the connecting rod (2) is fixedly installed with the main piston (21), and the other end of the connecting rod (2) is fixedly installed with a secondary piston (22). The secondary piston (22) is slidably connected to the groove of the connecting block of the piston rear cover (13) through a sealing ring, and the main piston (21) is slidably connected to the groove of the connecting block of the brake seat (12) through a sealing ring.

3. The pneumatic brake detection device for a direct-drive rotary table of a CNC machine tool according to claim 2, characterized in that: A piston measuring rod (3) is fixedly installed on the outer side of the auxiliary piston (22). One end of the piston measuring rod (3) passes through the piston rear cover (13) and extends to its outside. The circumferential surface of the piston measuring rod (3) is slidably connected to the inner wall of the groove of the piston rear cover (13) through a sealing ring. A baffle (31) is fixedly installed on the outer surface of the piston measuring rod (3). The baffle (31) is located outside the piston rear cover (13) and is used to limit the displacement distance of the piston measuring rod (3).

4. The pneumatic brake detection device for a direct-drive rotary table of a CNC machine tool according to claim 3, characterized in that: The piston displacement detection unit also includes a connecting seat (4), which is fixedly installed on the outer surface of the piston rear cover (13) by bolts. The reading head (41) is fixedly installed on the support plate of the connecting seat (4). The magnetic scale (42) is fixedly installed on the outer surface of the piston measuring rod (3). The magnetic scale (42) is located outside the baffle (31). The magnetic scale (42) and the reading head (41) maintain a gap of 0.5 mm to 2 mm and parallelism. The signal input terminal of the control box (15) is electrically connected to the signal output terminal of the reading head (41) through a wire.

5. A pneumatic brake detection device for a direct-drive rotary table of a CNC machine tool according to claim 4, characterized in that: The air pressure unit also includes a brake air pipe (5), which is fixedly connected to the brake air path of the piston chamber of the piston rear cover (13). The release air path of the piston chamber of the piston rear cover (13) is fixedly connected to the release air pipe (51). The ends of the brake air pipe (5) and the release air pipe (51) are both connected to the digital pressure sensor (52) by sealant thread. The signal input terminal of the control box (15) is electrically connected to the signal output terminal of the digital pressure sensor (52) by wire.

6. A method for detecting the pneumatic brake of a CNC machine tool direct-drive rotary table, using the pneumatic brake detection device for a CNC machine tool direct-drive rotary table as described in any one of claims 1-5, characterized in that: S1: Mechanical installation and displacement reference self-test: Fix the brake housing (1) on the machine tool stationary base, connect the turntable connecting shaft (14) to the power output end of the direct drive turntable, after the device is powered on, the control box (15) controls the pneumatic brake mechanism to drive the piston measuring rod (3) to extend until the auxiliary piston (22) touches the limit surface of the piston rear cover (13), use the reading head (41) to read the first limit position signal of the magnetic scale (42), and use this as a reference to calibrate the zero point and full scale of the piston displacement, and confirm that the signal communication between the reading head (41) and the magnetic scale (42) is normal; S2: Air circuit sealing and pressure reference calibration: The brake air circuit pipe (5) and the release air circuit pipe (51) are respectively connected to the external air source and the electromagnetic reversing valve controlled by the control box (15). The control box (15) switches the air circuit direction by controlling the electromagnetic reversing valve, and fills the piston chamber of the piston rear cover (13) with the preset detection pressure through the brake air circuit pipe (5) or the release air circuit pipe (51). During the pressure holding period, the pressure change is monitored by the digital pressure sensor (52), and the pressure holding pressure drop rate is calculated. If the pressure drop rate is lower than the preset leakage threshold, the air circuit sealing test is qualified. At the same time, according to the current pressure values ​​of the brake air circuit and the release air circuit, the zero drift and gain error of the pressure sensor are calibrated to complete the initialization of the air circuit detection system. S3: Synchronous timing data acquisition and standardization: Upon receiving a braking or releasing action trigger command, the control box (15) synchronously acquires the brake air circuit pressure signal, the release air circuit pressure signal, and the piston displacement signal, and converts the acquired raw signals into a time-series standardized actual pressure value sequence. and standardized actual displacement value sequence ; S4: Dynamic Process Feature Extraction: For braking actions, extract features from pressure value sequences. and displacement value sequence Extract the following feature groups: Feature group F1: Stable pressure value Displacement stability value And the pressure rises from the initial value to the preset pressure threshold. Time required ; Feature group F2: Displacement changes from the initial value to a preset displacement threshold Time required And the time difference between the pressure stabilization moment and the displacement stabilization moment. ; For the release action, from the pressure value sequence and displacement value sequence Extract the following feature groups: Feature group F3: Stable pressure value Displacement stability value And the pressure drops from the initial value to the preset pressure threshold. Time required ; Feature group F4: Displacement reverts from the initial value to a preset displacement threshold. Time required And the time difference between the pressure stabilization moment and the displacement stabilization moment. ; Among them, the preset pressure threshold , and preset displacement threshold , These are fixed or proportional values ​​preset based on the normal operating parameters of the system; S5: State health assessment based on multi-feature fusion: The extracted dynamic correlation features are input into the pre-trained state assessment model; The condition assessment model outputs a health score. and the corresponding status labels; among which, ,when Greater than or equal to the first health threshold When the status is successful, the status label is: Success; when Less than the first health threshold but greater than or equal to the second health threshold At that time, the status label is: Warning; When the health level is below the second health threshold, the status label is: Failure; The condition assessment model is obtained by training historical normal action data and historical abnormal action data through machine learning algorithms. It is used to learn the nonlinear mapping relationship between multiple features and the health status of the braking system. S6: Result Output and Decision Execution: Based on the status label output in step S5, control the CNC machine tool direct drive rotary table to perform the corresponding operation. If successful, continue running; if an alarm is triggered, log is recorded and the speed can be selectively reduced; if a failure occurs, an alarm is immediately triggered and the machine is safely stopped.

7. The method for detecting the pneumatic brake of a CNC machine tool direct-drive rotary table according to claim 6, characterized in that: Obtain the pressure value at the start of the pressure holding process. and the pressure value at the end of the pressure holding period Calculate the pressure change: ; Calculate the holding time: ; Pressure drop rate Through the formula: The calculation yielded the result.

8. A method for detecting the pneumatic brake of a CNC machine tool direct-drive rotary table according to claim 6, characterized in that: In S4, the extracted correlation features also include the baseline error feature, and the calculation logic is as follows: The pressure value sequence of the current action and displacement value sequence Compared with the pre-stored reference pressure curve and reference displacement curve Align the curves and calculate the difference between the current curve and the baseline curve at the corresponding time points. Calculate the square of the difference, and then take the square root of the average of the sum of all the squared differences to obtain the root mean square value of the pressure error. and root mean square value of displacement error .

9. A method for detecting the pneumatic brake of a CNC machine tool direct-drive rotary table according to claim 8, characterized in that: In S5, the health score The calculation employs a weighted fusion approach, combining model probability with physical error correction, as detailed below: The probability value output by the state assessment model that belongs to the success category is... Then the health score Calculated using the following formula: in, , , The preset weighting coefficients, and ; and These are the preset maximum allowable pressure error and displacement error thresholds, respectively.

10. A method for detecting the pneumatic brake of a CNC machine tool direct-drive rotary table according to claim 6, characterized in that: In S4, feature extraction also includes time lag features: time lag Displacement value sequence The moment when the mid-displacement first exceeds the preset displacement noise threshold , and pressure value sequence The moment when the medium pressure first exceeds the preset pressure noise threshold The difference, that is .

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