Horizontal five-axis cam rotary table system with double closed-loop full-working-condition error compensation and control method

Abstract

This application discloses a horizontal five-axis cam rotary table system and control method with dual closed-loop full-condition error compensation, belonging to the technical field of core functional components of high-end CNC machine tools. The system includes a mechanical execution unit, a dual closed-loop detection unit, a full-condition error compensation control unit, a servo drive unit, a safety protection unit, and a digital operation and maintenance subsystem. It adopts a dual symmetrical arc surface cam roller zero-backlash transmission structure, and pioneers a dual closed-loop detection architecture of transmission inner ring + machining outer ring. It has a built-in multi-dimensional full-condition error compensation model and is equipped with a hydraulic normally closed safety brake mechanism. This invention solves the pain points of poor accuracy retention and insufficient dynamic compensation of existing rotary tables. The product repeatability accuracy is ≤4arc.sec, and the accuracy decay after 1000 hours of operation is ≤1arc.sec, which meets production requirements and is suitable for high-end processing scenarios such as aerospace and precision molds.

Description

Technical Field

[0001] This invention relates to the technical field of core functional components of high-end CNC machine tools, specifically to a horizontal five-axis cam rotary table system and control method with dual closed-loop full-condition error compensation. Background Technology

[0002] The five-axis CNC rotary table is a core functional component of high-end CNC machine tools, providing the machine tool with the rotary indexing and linkage machining capabilities of the fourth and fifth axes, directly determining the machining accuracy and efficiency of complex curved surface parts. Currently, the mainstream CNC rotary table transmission structures are divided into two categories: worm gear transmission and cam roller transmission. Among them, the cam roller transmission structure, with its advantages of zero backlash, high rigidity, low wear, and long service life, is gradually replacing the traditional worm gear structure and has become the core technology direction of high-end five-axis rotary tables.

[0003] In the existing technology, some progress has been made in the research and development of cam-type five-axis rotary tables: the volume of the rotary table has been reduced through structural optimization, but the problem of dynamic error compensation under all working conditions has not been solved; optimization is only made for the backlash of single-axis rotary tables, which cannot adapt to the complex working conditions of five-axis linkage; only the brake rigidity has been improved, but the problem of compensation for thermal deformation and cutting force deformation has not been solved; only a single temperature sensor is used for coarse compensation, which has limited accuracy; error compensation design has been carried out for machine tools, but it has not been extended to the rotary table itself; the rotary table structure has been optimized, but the full-link closed-loop detection and digital operation and maintenance capabilities are lacking.

[0004] Existing cam-type five-axis rotary tables still have the following core technical defects in practical engineering applications: 1. Insufficient accuracy retention: Existing single cam drive structures have problems with asymmetrical force and eccentric load. After long-term operation, the wear of the cam roller pair leads to an increase in back clearance. At the same time, the temperature rise generated by high-speed operation and continuous cutting will cause thermal deformation of the camshaft and housing, resulting in a decrease in positioning accuracy. Existing technology cannot achieve coordinated compensation of thermal error and wear error. 2. Lack of dynamic error compensation capability under all working conditions: The existing turntable only uses single-loop position control of the encoder at the motor end, which cannot monitor the actual position error at the machining end in real time. It lacks effective closed-loop compensation methods for cutting force deformation, posture error caused by workpiece center of gravity shift, and dynamic following error of five-axis linkage during heavy cutting process, making it difficult to guarantee the yield rate of complex curved surface machining. 3. Insufficient braking safety and rigidity: Most existing rotary table braking mechanisms are single-sided end face locking, which results in insufficient braking torque under heavy cutting conditions and is prone to machining vibration; at the same time, most adopt an electric braking structure, and when the machine tool suddenly loses power, the rotary table cradle frame is prone to fall due to gravity, causing workpiece scrap, equipment damage or even safety accidents. 4. Lack of digital operation and maintenance and predictive maintenance capabilities: Existing turntables can only achieve passive failure shutdown repair, and cannot predict potential failures such as wear of transmission pairs and failure of bearings in advance, resulting in long unplanned downtime and high maintenance costs, which cannot meet the needs of intelligent factories in the Industry 4.0 era. Summary of the Invention

[0005] The purpose of this invention is to provide a horizontal five-axis cam rotary table system and control method with dual closed-loop full-condition error compensation, which solves the problems of poor accuracy retention, lack of dynamic error compensation capability under full-condition conditions, insufficient braking safety, and weak digital operation and maintenance capability of existing cam-type five-axis rotary tables. It achieves high precision, high rigidity, high safety, long service life and stable operation of the five-axis rotary table, breaks the technological monopoly of foreign high-end five-axis rotary tables, and realizes import substitution.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A horizontal five-axis cam rotary table system with dual closed-loop full-condition error compensation includes a mechanical execution unit, a dual closed-loop detection unit, a full-condition error compensation control unit, a servo drive unit, and a safety protection unit. The mechanical actuator includes a base, a cradle-type A-axis rotary mechanism, a C-axis rotary mechanism, a double-symmetrical arc-surface cam roller transmission assembly, an integrated hydraulic brake locking mechanism, and an integrated thermal management lubrication assembly. The A-axis rotary mechanism and the C-axis rotary mechanism are arranged perpendicularly and orthogonally, forming a five-axis linkage with two rotational degrees of freedom. The double-symmetrical arc-surface cam roller transmission assembly drives the rotational motion of the A-axis and C-axis respectively, realizing zero-backlash rolling transmission. The integrated hydraulic brake locking mechanism is integrated at the output ends of the A-axis and C-axis respectively, providing the locking torque and safe braking capability required for heavy cutting. The integrated thermal management lubrication assembly is connected to the oil circuit of the double-symmetrical arc-surface cam roller transmission assembly, realizing constant temperature lubrication and temperature rise control. The dual closed-loop detection unit includes an inner loop position detection subunit and an outer loop machining end detection subunit. The inner loop position detection subunit includes absolute encoders installed on the A-axis and C-axis servo motor ends, respectively, and a circular grating installed on the end of the camshaft, realizing position data acquisition of the entire transmission chain. The outer loop machining end detection subunit includes laser displacement sensors symmetrically arranged at both ends of the cradle worktable, and an online laser interferometer installed in the machine tool machining area, realizing real-time monitoring of the actual position and attitude of the machining end. The full-condition error compensation control unit is electrically connected to the dual closed-loop detection unit, servo drive unit, and safety protection unit, respectively. It has built-in thermal error compensation model, dynamic cutting force error compensation model, center of gravity offset compensation model, and backlash preload compensation algorithm to realize the collaborative calculation and real-time compensation of multi-source errors. The backlash preload compensation algorithm is based on forward and reverse operation conditions and adjusts the preload of the cam drive in real time to eliminate backlash error when switching between forward and reverse directions. The safety protection unit includes a normally closed hydraulic braking subunit, an overload protection subunit, and an abnormal vibration early warning subunit, which are linked with the integrated hydraulic brake locking mechanism to achieve safety protection in all scenarios.

[0007] In a preferred embodiment, the double-symmetric arc-surface cam roller transmission assembly includes an A-axis drive assembly and a C-axis drive assembly. The A-axis drive assembly adopts a double-arc-surface cam symmetrical arrangement structure, with two sets of arc-surface cams coaxially connected in series on the output shaft of the A-axis drive motor. The phase difference between the curved surfaces of the two sets of cams is 180°, and they mesh with the needle roller bearing assemblies on both sides of the cradle frame without backlash, eliminating the eccentric load of single-cam drive, improving the support rigidity and motion stability of the cradle frame, and reducing the backlash error during forward and reverse rotation switching. The C-axis drive assembly adopts a single-arc-surface cam meshing structure with a full complement needle roller bearing indexing plate. The needle roller bearing adopts a forged blank integrated precision grinding structure, with the concentricity of the rollers and bushings ≤0.5μm, ensuring indexing accuracy and load-bearing capacity.

[0008] In a preferred embodiment, the integrated hydraulic brake locking mechanism includes an A-axis brake assembly and a C-axis brake assembly. The A-axis brake assembly adopts a double-end disc spring hydraulic normally closed structure, including a brake seat, a floating brake disc, multiple sets of disc springs, and a hydraulic oil chamber. The floating brake disc is interference-fitted with the A-axis output shaft. In the power-off state, the disc springs push the floating brake disc to lock against the brake seat on both sides. When hydraulic oil is supplied, the disc springs are compressed to release the lock, realizing power-off safety protection and heavy cutting locking. The C-axis brake assembly adopts a circumferential multi-plate hydraulic brake structure with a braking torque ≥4600 N·m and a braking response time ≤0.05s, meeting the locking requirements of heavy-duty machining.

[0009] In a preferred embodiment, the integrated thermal management lubrication assembly includes a constant-temperature lubricating oil tank, a circulating oil pump, an oil distributor, a temperature sensor, and a differential pressure sensor. The lubrication oil circuit runs through the cam engagement pair, bearing assembly, and brake mechanism of the A-axis and C-axis. The oil distributor is equipped with independent throttling orifices for each lubrication point to achieve precise lubrication. The temperature sensor collects the temperature rise data of the lubricating oil and camshaft in real time and transmits it to the thermal error compensation model of the full-condition error compensation control unit to provide data support for thermal error compensation. The differential pressure sensor monitors the oil circuit pressure in real time and predicts lubrication failures and wear of the transmission pair.

[0010] In a preferred embodiment, the inner loop position detection subunit of the dual closed-loop detection unit collects angle data from the servo motor encoder and actual rotation data from the camshaft circular grating to form an inner closed loop of the transmission chain, compensating for backlash and cumulative errors in the transmission chain. The outer loop machining end detection subunit collects real-time posture, runout, and deformation data of the cradle worktable through a laser displacement sensor and collects actual position data of the workpiece machining end through an online laser interferometer, forming an outer closed loop of the machining chain to compensate for comprehensive errors under all working conditions, thereby achieving full-link closed-loop control from "transmission control" to "machining result".

[0011] In a preferred embodiment, the thermal error compensation model of the full-condition error compensation control unit is based on the temperature data of the camshaft, bearing, housing, and ambient temperature collected by multiple temperature sensors. It uses a BP neural network algorithm to fit the mapping relationship between temperature rise and positioning error, and outputs compensation values ​​to the servo drive unit in real time to eliminate accuracy errors caused by thermal deformation. The dynamic cutting force error compensation model is based on spindle cutting force data and turntable vibration data, and adjusts the position loop gain and feedforward compensation values ​​of the A-axis and C-axis in real time to suppress cutting chatter and compensate for deformation errors caused by cutting force. The center of gravity offset compensation model is based on the workpiece weight and weight distribution changes during the cutting process, and adjusts the balance compensation torque of the cradle frame in real time to eliminate attitude errors and motion deviations caused by center of gravity offset.

[0012] In a preferred embodiment, the normally closed hydraulic braking subunit of the safety protection unit has a built-in energy accumulator. When the machine tool experiences a sudden power outage, the energy accumulator maintains the hydraulic system pressure and, in conjunction with the disc spring, locks the cradle within 0.02 seconds to prevent it from falling. The overload protection subunit collects servo motor torque and brake mechanism pressure data in real time and immediately stops the machine when the threshold is exceeded. The abnormal vibration early warning subunit collects turntable vibration data through vibration sensors, predicts wear and faults in the transmission pair, and issues early warning signals to achieve predictive maintenance.

[0013] In a preferred embodiment, the curved surface of the double-symmetric arc surface cam is processed by a pendulum grinding process, with a surface finish Ra≤0.4μm, a contour error≤2μm, a repeatability of A-axis and C-axis ≤4arc.sec, a positioning accuracy ≤15arc.sec, and an accuracy decay of ≤1arc.sec after 1000 hours of continuous operation.

[0014] A preferred embodiment further includes a digital operation and maintenance and predictive maintenance subsystem, which is electrically connected to the full-condition error compensation control unit. The subsystem has a built-in transmission pair wear prediction model, remaining life assessment model, and fault diagnosis knowledge base. By collecting the full life cycle operation data of the dual closed-loop detection unit, temperature sensor, vibration sensor, and pressure sensor, the subsystem analyzes the wear status of the transmission pair, the remaining life of the bearing, and potential fault risks in real time, generates graded maintenance suggestions, and pushes them to the cloud platform, supporting remote condition monitoring and batch equipment cluster management.

[0015] This application also provides a control method for a horizontal five-axis cam rotary table with dual closed-loop full-condition error compensation, applied to the aforementioned horizontal five-axis cam rotary table system with dual closed-loop full-condition error compensation, comprising the following steps: S1. System initialization: complete the zero-point calibration of the dual closed-loop detection unit, the parameter calibration of each sensor, and the initialization of the full-condition error compensation model. S2. During the machining process, the inner ring position detection subunit collects the transmission chain position data of the A-axis and C-axis in real time, and the outer ring machining end detection subunit collects the worktable posture and workpiece machining end position data in real time, and transmits them synchronously to the full working condition error compensation control unit. S3, the full-condition error compensation control unit synchronously calls the thermal error compensation model, the dynamic cutting force error compensation model, and the center of gravity offset compensation model, and combines the data collected by the dual closed loop to calculate the comprehensive error compensation value and send it to the servo drive unit in real time. S4. The servo drive unit adjusts the motion trajectory of the A-axis and C-axis based on the compensation value to complete the dual closed-loop real-time compensation. S5. The safety protection unit monitors the system status in real time. In the event of a sudden power outage, overload, or abnormal vibration, it immediately triggers the corresponding protection action and stops processing simultaneously.

[0016] Due to the application of the above technical solution, the beneficial effects of this application compared with the prior art are as follows: 1. Significantly improves the accuracy retention and long-term operational stability of the turntable: The double-symmetrical arc-shaped cam transmission structure eliminates the eccentric load and uneven force distribution problems of single cam drive. Combined with integrated thermal management lubrication components, it reduces cam pair wear and temperature rise deformation. At the same time, through double closed-loop full-condition error compensation, it achieves coordinated compensation of thermal error, wear error and backlash error. The accuracy decay after 1000 hours of continuous operation is ≤1 arc.sec, which is far superior to the industry standard and solves the pain point of rapid accuracy decay of existing turntables during long-term operation.

[0017] 2. Achieve dynamic closed-loop control of errors under all working conditions and improve the yield rate of complex curved surface machining: The pioneering "transmission inner loop + machining outer loop" dual closed-loop detection architecture breaks through the limitation of existing single-loop control that can only monitor the transmission position and cannot control the machining results; the built-in multi-dimensional error compensation model can compensate for multi-source errors under all working conditions in real time, such as thermal deformation, cutting force deformation, center of gravity offset, linkage following error, etc. The contour accuracy of five-axis linkage machining is improved by more than 30%, and the yield rate of complex curved surface machining is improved by more than 40%.

[0018] 3. Comprehensive improvement in braking safety and structural rigidity: The integrated hydraulic normally closed brake mechanism combines high locking torque for heavy cutting with power failure safety protection. The double-end face brake structure on the A-axis solves the problem of stress deformation when the cradle frame is locked on one side, while the multi-plate brake structure on the C-axis achieves high torque locking. The braking response time is ≤0.05s, and it can lock within 0.02s in the event of a sudden power failure, completely eliminating the safety hazard of the cradle frame falling. At the same time, the double symmetrical cam structure increases the rigidity of the cradle frame support by more than 50%, and significantly improves the vibration resistance under heavy cutting conditions.

[0019] 4. Achieve deep integration of mechanical structure and control algorithm, taking into account both high precision and high dynamic response: Based on the mechanical characteristics of cam roller drive, match the corresponding backlash preload compensation algorithm and servo feedforward control algorithm to achieve deep synergy between mechanical transmission, servo control and error compensation. The turntable rapid traverse speed is increased by 50%, while the repeatability accuracy is stable at ≤4arc.sec, reaching the advanced level of similar international products.

[0020] 5. Possesses complete digital operation and maintenance and predictive maintenance capabilities: Through the digital operation and maintenance subsystem with edge computing + cloud architecture, it realizes the full life cycle status monitoring and fault prediction of the turntable, reduces unplanned downtime by more than 60%, extends the average service life of equipment by 30%, and reduces maintenance costs by 40%, perfectly adapting to the needs of Industry 4.0 intelligent factories. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a block diagram of the overall architecture of the horizontal five-axis cam rotary table system of the present invention; Figure 2 This is a schematic cross-sectional view of the mechanical execution unit of the present invention; Figure 3This is a flowchart of the dual closed-loop detection and error compensation control process of the present invention; Figure 4 This is a cross-sectional schematic diagram of the integrated hydraulic brake locking mechanism of the present invention; Figure 5 This is a schematic flowchart of the control method of the present invention; 1. Mechanical Actuation Unit; 11. Base; 12. Cradle-type A-axis Rotary Mechanism; 13. C-axis Rotary Mechanism; 14. Double-symmetrical Arc-surface Cam Roller Drive Assembly; 15. Integrated Hydraulic Brake Locking Mechanism; 151. Brake Seat; 152. Floating Brake Disc; 153. Disc Spring; 154. Hydraulic Oil Chamber; 155. A-axis Output Shaft; 16. Integrated Thermal Management Lubrication Assembly; 2. Dual closed-loop detection unit; 3. Full-condition error compensation control unit; 4. Servo drive unit; 5. Safety protection unit; 6. Digital operation and maintenance and predictive maintenance subsystem. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0024] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0025] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0026] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain situations to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0027] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] Example 1 See appendix Figure 1-5 This embodiment provides a horizontal five-axis cam rotary table system and control method with dual closed-loop full-condition error compensation, which is adapted to a horizontal five-axis machining center. The target product is an AC-axis horizontal five-axis cam rotary table with a maximum horizontal load of 100kg, an A-axis swing range of ±120°, a C-axis 360° continuous rotation, and a rapid traverse speed of 60rpm.

[0030] This system includes a mechanical actuator unit 1, a dual closed-loop detection unit 2, a full-condition error compensation control unit 3, a servo drive unit 4, a safety protection unit 5, and a digital operation and maintenance and predictive maintenance subsystem 6.

[0031] The base 11 of the mechanical actuator 1 is made of HT300 cast iron and is subjected to two artificial aging treatments to eliminate internal stress. The cradle-type A-axis rotary mechanism 12 adopts a double-sided support structure, and the cradle frame is made of titanium alloy material, which takes into account both lightweight and high rigidity. The C-axis rotary mechanism 13 is integrated in the center of the cradle frame. The worktable diameter is 250mm, and it adopts a high-strength alloy steel structure with a T-slot spacing of 50mm.

[0032] The A-axis drive assembly of the double-symmetric arc-surface cam roller transmission assembly 14 employs two sets of coaxial, series-connected arc-surface cams with a 180° phase difference. The cam material is 40CrNiMoA, carburized and quenched to a surface hardness of HRC58-62, and machined using a pendulum grinding process, achieving a surface finish of Ra0.4μm and a contour error of 2μm. The two sets of cams engage with needle roller bearing assemblies on both sides of the cradle frame with zero backlash and preload. The needle roller bearings are made from GCr15SiMn bearing steel forged blanks, precision ground, with a roller-sleeve concentricity of 0.5μm and a bearing accuracy of 1μm after assembly. The C-axis drive assembly uses a single-arc-surface cam meshing structure with a full complement needle roller bearing indexing plate. 24 sets of needle roller bearings are evenly distributed around the circumference of the indexing plate, achieving zero-backlash transmission.

[0033] The A-axis brake assembly of the integrated hydraulic brake locking mechanism 15 adopts a double-end disc spring hydraulic normally closed structure, with 12 sets of disc springs 153 built in. The brake seat 151 is integrally cast with the cradle frame housing, and a hydraulic oil chamber 154 is provided in the middle. The floating brake disc 152 is interference-fitted with the A-axis output shaft 155. The locking torque is 2800 N·m in the power-off state, and the locking can be released by passing 6 MPa of hydraulic oil. The C-axis brake assembly adopts a circumferential 8-piece friction plate hydraulic brake structure. The friction plates are made of copper-based powder metallurgy material, with a braking torque of 4600 N·m and a braking response time of 0.05s.

[0034] The integrated thermal management lubrication assembly 16 uses a 20L constant temperature lubrication oil tank with a temperature control accuracy of ±0.5℃ and a circulating oil pump flow rate of 5L / min. The oil distributor has independent throttling orifices for eight lubrication points, corresponding to the cam meshing pair, front and rear bearings, and brake mechanism, to achieve precise lubrication. PT100 temperature sensors are arranged at both ends of the camshaft, the housing, the lubrication oil circuit, and the environment to collect temperature rise data in real time. A differential pressure sensor is installed at the oil circuit inlet to monitor the oil circuit pressure and filtration status. When the differential pressure exceeds 0.3MPa, a filter element replacement warning is issued.

[0035] The A-axis and C-axis servo motors of the inner ring position detection subunit are equipped with 23-bit absolute encoders. 0.5 arcsecond precision circular gratings are installed at the ends of the A-axis dual camshaft and the C-axis camshaft, respectively, to collect the actual rotation angle of the camshaft in real time, compare it with the motor encoder data, calculate the backlash and cumulative error of the transmission chain, and compensate for the resolution of 0.1 arcsecond.

[0036] The outer ring machining end detection subunit has two sets of laser displacement sensors symmetrically arranged at both ends of the cradle worktable, with a sampling frequency of 10kHz and a measurement accuracy of 0.1μm, to collect the pitch, yaw, and radial runout data of the cradle frame in real time; a Renishaw XL-80 online laser interferometer is installed in the machine tool machining area to collect the actual position data of the workpiece machining end in real time, compare it with the command position of the CNC system, and calculate the comprehensive machining error.

[0037] The full-condition error compensation control unit 3 adopts an FPGA+ARM dual-core architecture. The FPGA is responsible for high-speed data acquisition and real-time control, while the ARM is responsible for complex algorithm calculation and system management. It has a built-in CNC system interface, which can be seamlessly connected with mainstream CNC systems such as FANUC, Siemens, and Huazhong CNC. It also has built-in thermal error compensation model, dynamic cutting force error compensation model, center of gravity offset compensation model, and backlash preload compensation algorithm.

[0038] The thermal error compensation model is based on data collected from five temperature sensors. Through a pre-trained BP neural network algorithm, it fits the mapping relationship between temperature rise and positioning error in real time, with a compensation resolution of 0.1 arcseconds. The dynamic cutting force error compensation model is connected to the force sensor of the machine tool spindle and combines it with the data from the rotary table vibration sensor to adjust the position loop and speed loop gain of the servo axis in real time to suppress cutting chatter. The center of gravity offset compensation model is based on the changes in workpiece weight and cutting allowance to calculate the center of gravity offset in real time and output the balance torque compensation value. The backlash preload compensation algorithm is based on forward and reverse rotation commands to adjust the preload angle of the servo motor in advance to eliminate backlash error during forward and reverse rotation switching.

[0039] The power-off normally closed hydraulic brake subunit of safety protection unit 5 has a built-in 0.5L hydraulic accumulator. When the machine tool suddenly loses power, the accumulator can maintain the hydraulic system pressure and lock within 0.02s with the disc spring 153. The overload protection subunit collects servo motor torque data in real time and sets 120% of the rated torque as the overload threshold. If the threshold is exceeded, the machine will stop immediately and trigger an emergency stop. The abnormal vibration early warning subunit arranges three-axis vibration sensors in the A-axis and C-axis housings respectively, with a sampling frequency of 20kHz. Based on big data algorithms, it identifies the characteristic frequencies of transmission pair wear and bearing failure and issues an early warning signal 72 hours in advance.

[0040] The Digital Operation and Predictive Maintenance Subsystem 6 adopts an edge computing + cloud architecture. The edge terminal is deployed on the turntable using an STM32H7 controller, which is responsible for real-time data acquisition and preprocessing. The data sampling frequency is 1kHz, and the preprocessed data compression rate reaches 80%. The cloud platform uses Alibaba Cloud ECS servers, which support the simultaneous access and management of more than 1,000 devices.

[0041] The transmission pair wear prediction model is based on vibration spectrum characteristics and operating load data, and adopts the Long Short-Term Memory (LSTM) network algorithm, achieving a prediction accuracy of over 92%. The remaining life assessment model is based on wear amount, operating time, and historical load data, and adopts the Weibull distribution model, with a remaining life prediction error of ≤10%. The fault diagnosis knowledge base contains the characteristic frequencies, causes, and handling methods of 120 common faults, supporting automatic fault diagnosis and maintenance guidance, with a fault identification accuracy of over 95%.

[0042] Users can remotely view the turntable's real-time operating status, historical operating data, and maintenance suggestions via mobile app or computer web interface. It supports cluster management and data analysis of batch devices, and generates equipment operation reports and maintenance plans.

[0043] The control method in this embodiment includes the following steps: S1. The system is powered on and initialized, and the zero-point calibration of the dual closed-loop detection unit 2 and the parameter calibration of each sensor are completed. The thermal error compensation model is initialized based on the ambient temperature. The CNC system completes the communication docking with the turntable system, and the digital operation and maintenance subsystem completes the connection with the cloud platform. S2. During the processing, the inner ring position detection subunit collects motor encoder and circular grating data of A-axis and C-axis in real time at a frequency of 1kHz, and the outer ring processing end detection subunit collects laser displacement sensor and laser interferometer data in real time at a frequency of 500Hz, and transmits them synchronously to the full working condition error compensation control unit 3. S3, the full-condition error compensation control unit 3 synchronously calls the four major compensation models, combines the multi-source data collected by the dual closed loop, calculates the comprehensive error compensation value of the A-axis and C-axis, and sends it to the servo drive unit 4 synchronously at the interpolation cycle; S4 and servo drive unit 4, based on the compensation value, correct the motion trajectory of the A-axis and C-axis in real time through feedforward control and PID adjustment, and complete the dual closed-loop real-time error compensation. S5 and safety protection unit 5 monitor the system status in real time throughout the process. In the event of a sudden power failure, the brake lock is triggered immediately. In the event of overload or abnormal vibration, an emergency stop signal is sent to the CNC system to stop processing and ensure the safety of equipment and personnel.

[0044] The S6 digital operation and maintenance and predictive maintenance subsystem continuously collects full lifecycle operation data, performs real-time preprocessing at the edge, and uploads it to the cloud platform. The cloud platform runs the transmission pair wear prediction model and remaining life assessment model once per hour, generates graded maintenance suggestions, and pushes them to the user's mobile APP. When a serious fault risk is detected, an emergency warning is immediately issued and maintenance personnel are notified.

[0045] Example 2 This embodiment provides a horizontal five-axis cam rotary table system and control method with dual closed-loop full-condition error compensation, which is suitable for heavy-duty high-precision horizontal five-axis cam rotary tables and is intended for heavy-duty machining of molds and aerospace structural parts.

[0046] I. Mechanical Actuation Unit 1: Base 11: HT350 high-strength cast iron, three-dimensional ribbed structure, 40% heavier than the standard type, and 35% more rigid.

[0047] A-axis cradle mechanism: Double-sided box support, cradle frame made of high-strength cast steel, A-axis swing range ±110°.

[0048] Double-symmetric arc-shaped cam drive: A-axis: Double-arc cam, material 18CrNiMo7-6, carburized and quenched HRC60-64, yaw grinding Ra≤0.3μm.

[0049] C-axis: Large diameter indexing plate, the number of needle roller bearings increased to 36, and the load capacity increased to 200kg.

[0050] Needle roller bearings: Forged blanks + ultra-precision grinding, concentricity ≤0.3μm, bearing accuracy after assembly ≤0.8μm.

[0051] Integrated hydraulic brake: A-axis: Double-end disc spring + hydraulic unlocking, locking torque 4200 N·m.

[0052] C-axis: 12 copper-based powder metallurgy friction plates, braking torque 7500 N·m, response ≤0.04s.

[0053] Integrated thermal management lubrication assembly 16: 30L constant temperature oil tank, oil temperature controlled within ±0.3℃.

[0054] 12-point independent lubrication, including brake cooling oil circuit, reducing temperature rise by ≤4℃.

[0055] II. Dual Closed-Loop Detection Unit 2: Inner ring inspection: Servo motor: 24-bit absolute encoder.

[0056] Camshaft end: 0.3 arcsecond high-precision circular grating.

[0057] Function: Real-time compensation for transmission chain backlash and elastic deformation, with an error resolution of 0.05″.

[0058] Outer ring inspection: Both ends of the worktable: high-precision laser displacement sensors, sampling at 20kHz, with a resolution of 0.05μm.

[0059] Processing area: Dual-frequency laser interferometer, real-time monitoring of the actual position of the workpiece.

[0060] Function: To form a closed loop of the entire chain from "motor-camshaft-worktable-workpiece".

[0061] III. Full-condition error compensation control unit 3: Hardware: FPGA+DSP+ARM triple core, control cycle 125μs.

[0062] Thermal error compensation: 8-channel PT100 temperature acquisition, BP neural network model, compensation accuracy ±0.2″.

[0063] Dynamic cutting force compensation: Connect to the machine tool spindle force gauge to correct servo gain in real time and suppress chatter.

[0064] Center of gravity offset compensation: Automatically outputs A-axis balancing torque based on workpiece weight / clamping position.

[0065] Backlash preload compensation: Automatically applies a preload angle during forward and reverse rotation to eliminate zero backlash transmission clearance.

[0066] IV. Safety Protection Unit 5: Normally closed braking upon power failure: 1.0L large-capacity energy storage device, locking in 0.015s upon power failure.

[0067] Overload protection: If the torque threshold reaches 130%, the machine will stop immediately and the shaft will be locked.

[0068] Abnormal vibration warning: A triaxial vibration sensor identifies bearing / cam wear characteristics and provides an early warning 72 hours in advance.

[0069] V. Digital Operations and Predictive Maintenance: Real-time acquisition of local edge data: temperature, vibration, oil pressure, torque, and accuracy data.

[0070] Cloud platform: Wear prediction: LSTM model, accuracy ≥94%.

[0071] Lifetime assessment: Weibull distribution, error ≤8%.

[0072] Fault database: 150 fault modes, automatically diagnosed and push repair solutions.

[0073] Supports: remote monitoring, data traceability, and batch cluster management.

[0074] Final performance metrics for this embodiment: C-axis repeatability: ≤2.5 arc.sec C-axis positioning accuracy: ≤10 arcsec A-axis repeatability: ≤3.0 arc.sec Maximum load capacity: 200kg Accuracy degradation after 1000 hours of continuous operation: ≤0.6 arc.sec Braking response time: ≤0.04s

[0075] Example 3 This embodiment provides a horizontal five-axis cam rotary table system and control method with dual closed-loop full-condition error compensation, which is suitable for high-speed and high-precision horizontal five-axis cam rotary tables and is geared towards high-speed linkage processing of 3C, medical devices and small precision parts.

[0076] I. Mechanical Actuation Unit 1: Lightweight cradle frame structure, made of aluminum alloy and high-strength steel composite.

[0077] Double-arc cam optimized curve, maximum C-axis speed: 100rpm.

[0078] Needle roller bearings: Ultra-lightweight design, reducing friction by 15%.

[0079] Brakes: Ultra-thin hydraulic normally closed structure, which does not increase inertia.

[0080] Lubrication: Precise lubrication with micro-flow, temperature rise control ≤3℃.

[0081] II. Dual Closed-Loop Detection Unit 2: Inner loop: High-speed response encoder + circular grating, tracking error ≤0.5″.

[0082] Outer ring: Miniature laser sensor for real-time monitoring of high-speed vibrations.

[0083] III. Full-condition error compensation control unit 3: High-speed thermal error model, high-speed dynamic response compensation, and high-speed backlash compensation.

[0084] High-speed linkage machining improves contour accuracy by ≥40%.

[0085] IV. Security Protection Unit 5 and Digital Operation and Predictive Maintenance:

[0086] High-speed overload protection and high-speed vibration monitoring.

[0087] Digitalized operation and maintenance is adapted to high-speed production lines, and predictive maintenance reduces downtime by ≥70%.

[0088] Indicators for this embodiment: Repeatability accuracy: ≤2.2 arc.sec Positioning accuracy: ≤8arc.sec Maximum speed: 100 rpm Noise level: ≤62dB The horizontal five-axis cam rotary table system of this embodiment, after third-party testing, has an A-axis repeatability of 3.2 arc.sec and a positioning accuracy of 12 arc.sec; a C-axis repeatability of 2.8 arc.sec and a positioning accuracy of 10 arc.sec; after 1000 hours of continuous operation, the accuracy decay is 0.8 arc.sec, the braking response time is 0.03s, the power failure locking time is 0.018s, and the unplanned downtime is reduced by 65%. All indicators meet production requirements and are suitable for high-end five-axis machining needs in aerospace, medical devices, precision molds and other fields.

[0089] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A horizontal five-axis cam rotary table system with double closed-loop full-working-condition error compensation, characterized in that, It includes a mechanical actuator, a dual closed-loop detection unit, a full-condition error compensation control unit, a servo drive unit, and a safety protection unit; The mechanical actuator includes a base, a cradle-type A-axis rotary mechanism, a C-axis rotary mechanism, a double-symmetric arc-surface cam roller transmission assembly, an integrated hydraulic brake locking mechanism, and an integrated thermal management lubrication assembly. The A-axis rotary mechanism and the C-axis rotary mechanism are arranged perpendicularly and orthogonally. The double-symmetric arc-surface cam roller transmission assembly drives the A-axis and C-axis rotary motion respectively. The integrated hydraulic brake locking mechanism is integrated at the output ends of the A-axis and C-axis respectively. The integrated thermal management lubrication assembly is connected to the oil circuit of the double-symmetric arc-surface cam roller transmission assembly. The dual closed-loop detection unit includes an inner loop position detection subunit and an outer loop machining end detection subunit; the inner loop position detection subunit includes absolute encoders installed on the A-axis and C-axis servo motor ends respectively, and a circular grating installed on the end of the camshaft; the outer loop machining end detection subunit includes laser displacement sensors symmetrically arranged at both ends of the cradle worktable, and an online laser interferometer installed in the machine tool machining area; The full-condition error compensation control unit is electrically connected to the dual closed-loop detection unit, servo drive unit, and safety protection unit, and has built-in thermal error compensation model, dynamic cutting force error compensation model, center of gravity offset compensation model, and backlash preload compensation algorithm. The safety protection unit includes a normally closed hydraulic braking subunit for power failure, an overload protection subunit, and an abnormal vibration early warning subunit, which are linked with the integrated hydraulic brake locking mechanism.

2. The horizontal five-axis cam table system with double closed-loop full-working-condition error compensation according to claim 1, characterized in that, The dual-symmetric arc-surface cam roller transmission assembly includes an A-axis drive assembly and a C-axis drive assembly. The A-axis drive assembly adopts a dual-arc-surface cam symmetrical arrangement structure, with two sets of arc-surface cams coaxially connected in series on the output shaft of the A-axis drive motor. The phase difference between the curved surfaces of the two sets of cams is 180°, and they mesh with the needle roller bearing assemblies on both sides of the cradle frame without backlash. The C-axis drive assembly adopts a single-arc-surface cam meshing structure with a full complement needle roller bearing indexing plate. The needle roller bearing adopts a forged blank integrated precision grinding structure, and the concentricity of the roller and the bushing is ≤0.5μm.

3. The horizontal five-axis cam table system with double closed-loop full-working-condition error compensation according to claim 1, characterized in that, The integrated hydraulic brake locking mechanism includes an A-axis brake assembly and a C-axis brake assembly. The A-axis brake assembly adopts a double-end disc spring hydraulic normally closed structure, including a brake seat, a floating brake disc, multiple sets of disc springs, and a hydraulic oil chamber. The floating brake disc is interference-fitted with the A-axis output shaft. In the power-off state, the disc springs push the floating brake disc to fit and lock the brake seat on both sides. When hydraulic oil is supplied, the disc springs are compressed to release the lock. The C-axis brake assembly adopts a circumferential multi-plate hydraulic brake structure with a braking torque ≥4600 N·m and a braking response time ≤0.05s.

4. The horizontal five-axis cam table system with double closed-loop full- working-condition error compensation according to claim 1, characterized in that, The integrated thermal management lubrication assembly includes a constant temperature lubricating oil tank, a circulating oil pump, an oil distributor, a temperature sensor, and a differential pressure sensor; the lubricating oil circuit runs through the cam meshing pairs, bearing assemblies, and brake mechanisms of the A-axis and C-axis; the oil distributor is equipped with independent throttling orifices for each lubrication point; the temperature sensor collects the temperature rise data of the lubricating oil and camshaft in real time and transmits it to the thermal error compensation model of the full-condition error compensation control unit.

5. The horizontal 5-axis cam table system with double closed-loop full- working-condition error compensation according to claim 1, characterized in that, The inner loop position detection subunit of the dual closed-loop detection unit collects the angle data of the servo motor encoder and the actual rotation data of the camshaft circular grating to form an inner closed loop of the transmission chain, compensating for the backlash and cumulative error of the transmission chain. The outer loop machining end detection subunit collects the real-time posture, runout and deformation data of the cradle worktable through a laser displacement sensor, and collects the actual position data of the workpiece machining end through an online laser interferometer, forming an outer closed loop of the machining chain to compensate for the comprehensive error under all working conditions.

6. The horizontal 5-axis cam table system with double closed-loop full- working-condition error compensation according to claim 1, characterized in that, The thermal error compensation model of the full-condition error compensation control unit is based on the temperature data of the camshaft, bearing, housing, and ambient temperature collected by multiple temperature sensors. It fits the mapping relationship between temperature rise and positioning error through a BP neural network algorithm and outputs the compensation value to the servo drive unit in real time. The dynamic cutting force error compensation model is based on the spindle cutting force data and turntable vibration data. It adjusts the position loop gain and feedforward compensation value of the A-axis and C-axis in real time. The center of gravity offset compensation model is based on the workpiece weight and the weight distribution change during the cutting process. It adjusts the balance compensation torque of the cradle frame in real time.

7. The horizontal 5-axis cam table system with double closed-loop full- working-condition error compensation according to claim 1, characterized in that, The power-off normally closed hydraulic braking subunit of the safety protection unit has a built-in energy accumulator. When the machine tool experiences a sudden power failure, the energy accumulator maintains the hydraulic system pressure and, in conjunction with the disc spring, locks the cradle within 0.02 seconds to prevent it from falling. The overload protection subunit collects servo motor torque and brake mechanism pressure data in real time and stops the machine immediately when the threshold is exceeded. The abnormal vibration early warning subunit collects turntable vibration data through vibration sensors, predicts wear and faults in the transmission pair, and issues early warning signals in advance.

8. The horizontal five-axis cam table system with double closed-loop full working condition error compensation according to claim 2, characterized in that, The curved surface of the double symmetrical arc surface cam is processed by a pendulum grinding process, with a surface finish Ra≤0.4μm, a contour error≤2μm, a repeatability of A-axis and C-axis ≤4arc.sec, a positioning accuracy ≤15arc.sec, and an accuracy decay of ≤1arc.sec after 1000 hours of continuous operation.

9. The horizontal 5-axis cam table system with double closed-loop full- working-condition error compensation according to claim 1, characterized in that, It also includes a digital operation and maintenance and predictive maintenance subsystem, which is electrically connected to the full-condition error compensation control unit and has a built-in transmission pair wear prediction model, remaining life assessment model and fault diagnosis knowledge base; By collecting operational data throughout the entire lifecycle of dual closed-loop detection units, temperature sensors, vibration sensors, and pressure sensors, the wear status of transmission pairs, remaining bearing life, and potential failure risks are analyzed in real time. Graded maintenance suggestions are generated and pushed to the cloud platform, supporting remote condition monitoring and batch equipment cluster management.

10. A control method of horizontal five-axis cam rotary table with double closed-loop full-working-condition error compensation, applied to the horizontal five-axis cam rotary table system with double closed-loop full-working-condition error compensation according to any one of claims 1-9, characterized in that, Includes the following steps: S1. System initialization: complete the zero-point calibration of the dual closed-loop detection unit, the parameter calibration of each sensor, and the initialization of the full-condition error compensation model. S2. During the machining process, the inner ring position detection subunit collects the transmission chain position data of the A-axis and C-axis in real time, and the outer ring machining end detection subunit collects the worktable posture and workpiece machining end position data in real time, and transmits them synchronously to the full working condition error compensation control unit. S3, the full-condition error compensation control unit synchronously calls the thermal error compensation model, the dynamic cutting force error compensation model, and the center of gravity offset compensation model, and combines the data collected by the dual closed loop to calculate the comprehensive error compensation value and send it to the servo drive unit in real time. S4. The servo drive unit adjusts the motion trajectory of the A-axis and C-axis based on the compensation value to complete the dual closed-loop real-time compensation. S5. The safety protection unit monitors the system status in real time. In the event of a sudden power outage, overload, or abnormal vibration, it immediately triggers the corresponding protection action and stops processing simultaneously.

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