Flexible and automatic milling system for complex and precise metal parts of spacecraft

Abstract

The invention discloses a flexible and automatic milling system for complex and precise metal parts of a spacecraft. The flexible and automatic milling system is composed of a numerical control machining center, a feeding and discharging subsystem, a function changing module, a cache subsystem, a master control subsystem and a management and control subsystem. The management and control subsystem receives a production plan and then performs intelligent production scheduling, the management and control subsystem sends a numerical control machining program to the numerical control machining center and starts machining, the numerical control machining center calls the master control subsystem for discharging, and the master control subsystem drives the feeding and discharging subsystem to automatically transmit function changing modules bound with parts to be machined to the numerical control machining center. And after machining is completed, the numerical control machining center calls the master control subsystem to take materials, and the master control subsystem drives the feeding and discharging subsystem to convey the function exchange modules to the cache subsystem and feeds back the completion state to the management and control subsystem. The system has an intelligent production scheduling function, and the utilization rate of equipment is greatly improved; and meanwhile, the capability of simultaneous mixed line machining of various different parts is achieved, and the requirement for multi-variety and small-batch flexible production of spacecrafts is greatly met.

Description

Technical Field

[0001] The present invention relates to the fields of mechanical engineering and electronic engineering, and more specifically, to a flexible and automatic milling system for complex and precise metal parts of a spacecraft. Background Art

[0002] With the rapid development of national defense and military industry, automobile manufacturing, rail transit, shipbuilding and marine engineering, etc. towards high-end and high-tech, especially the strategic emerging industries in the aerospace field represented by deep space exploration, manned space flight, Beidou navigation, and unmanned aerial vehicles, the demand for high-end equipment for complex precision parts processing is developing in the direction of flexibility, digitalization, networking and gathering points into lines, and gradually realizing the transformation from single CNC machining centers to intelligent flexible manufacturing production lines, with the characteristics of high efficiency, high precision, high reliability, high stability, high degree of intelligence and flexibility, greenness and low processing cost. The domestic and foreign technological competition is extremely fierce, and blockades and frictions continue.

[0003] Large heterogeneous spacecraft space mechanisms are required to work in harsh environments with constantly changing working conditions. They require higher precision, higher reliability, longer life, and lower energy consumption for precision parts of space mechanisms. The flexible and automatic processing of complex precision parts of the mechanism still has the following problems:

[0004] 1) At present, the precision parts processing equipment for large heterogeneous spacecraft mechanisms has long been dependent on imports and single-machine production. There is a lot of manual intervention in the production process and the processing software system data is subject to the risk of theft, tampering or even deactivation. At the same time, it brings problems such as poor system confidentiality and security, inconvenient maintenance and high cost of use.

[0005] 2) my country's high-end equipment and domestic precision parts processing equipment have problems such as single-machine production, low processing efficiency, poor precision, poor reliability, poor stability, low yield rate, and long changeover time. Its comprehensive performance, production efficiency, automation, intelligence, flexibility, product consistency, stability and reliability are far behind the international advanced level. Summary of the invention

[0006] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and provide a flexible and automatic milling processing system for complex precision metal parts of spacecraft, thereby solving the bottleneck problem of high-precision, high-efficiency, high-reliability and high-stability processing of complex structural precision parts of spacecraft.

[0007] The technical solution of the present invention is: a flexible and automatic milling processing system for complex precision metal parts of spacecraft, including: a CNC machining center, a loading and unloading subsystem, a changing function module, a cache subsystem, a general control subsystem and a management and control subsystem; the CNC machining center completes the milling processing operation of the precision metal parts of the spacecraft by communicating with the general control subsystem and the management and control subsystem; the loading and unloading subsystem is used to undertake the automatic distribution operation of the changing function module between the CNC machining center and the cache subsystem; the changing function module is used to lock the precision metal parts of the spacecraft to be processed and the precision metal parts of the spacecraft that have been processed; the cache subsystem is used to store the changing function module; the general control subsystem is used to complete the transmission of instructions with the CNC machining center, the driving of the actions of the loading and unloading subsystem, and the issuance of production tasks and feedback of production status between the management and control subsystem.

[0008] The CNC machining center is equipped with an automatic door, an automatic probe and a zero-point positioning device, has a recording function, and is deployed with a remote module for communicating with the general control subsystem; the CNC machining center and the general control subsystem realize IO communication through the remote module, and the interactive signals include automatic door opening / closing in place, material discharge call, material discharge completion, material collection call, material collection completion, lock signal, zero-point locking / relaxing, start, and stop signals; the CNC machining center and the management and control subsystem communicate through the network port to realize the reception of CNC machining programs, as well as idle, working, and fault status information feedback.

[0009] After the CNC machining center receives the CNC machining program and obtains the start-up command, it activates the automatic door to open, sends the working status to the management and control subsystem, sends the automatic door opening and material discharge call signal to the general control subsystem, controls the locking of each spindle after receiving the lock signal, and locks the function module changer on the zero point positioning device after the CNC machining center receives the zero point locking signal; when the material feeding completion signal is received, the automatic door is called to close, and the automatic probe is enabled to carry out the positioning accuracy detection of the function module changer, and the CNC machining program is started after the positioning accuracy is better than the preset value; after executing the CNC machining program, the CNC machining center calls the automatic door to open and sends the automatic door opening and material collection call signal to the general control subsystem, and controls the zero point positioning device to release after receiving the zero point release command, and the function module to be replaced leaves the CNC machining center and receives the material collection completion signal, calls the automatic door to close, and sends the idle status to the management and control subsystem.

[0010] The loading and unloading subsystem consists of a loading station, a ground rail, a robot and an end effector; the robot moves back and forth on the ground rail, and the robot's motion trajectory covers the CNC machining center, all storage locations of the cache subsystem and the loading station work positions. The end effector can pick up and place functional modules to complete the automatic transfer of complex and precise metal parts of the spacecraft within the unit.

[0011] The loading station provides a human-machine interactive operation terminal and is equipped with an RFID radio frequency card reader, which is used to complete the clamping of the replacement function module of the complex and precise metal parts of the spacecraft to be processed and the disassembly of the replacement function module of the complex and precise metal parts of the spacecraft after processing; the operator can drive the RFID card reader to read the electronic tag information of the replacement function module through the human-machine interactive operation terminal, bind the tag information of the replacement function module with the part information and upload it to the management and control subsystem, so as to realize the out-of-warehouse and in-warehouse operations of the replacement function module.

[0012] The specific working process of the loading and unloading subsystem is as follows:

[0013] The operator calls the replacement function module through the human-machine interactive operation terminal of the loading station. The management and control subsystem sends the replacement function module at the storage position of the cache subsystem to the general control subsystem. The general control subsystem drives the ground rail and the robot to move to the cache subsystem. The robot's end effector grabs the replacement function module and transports it to the loading station work position. The operator places the complex and precise metal parts of the spacecraft on the replacement function module and locks it. The operator drives the RFID card reader on the human-machine interactive operation terminal of the loading station to read the electronic tag information of the replacement function module and bind the complex and precise metal parts information of the spacecraft. The bound information is fed back to the management and control subsystem. The operator starts the warehousing operation at the human-machine interactive operation terminal of the loading station. The management and control subsystem selects the storage position in the cache subsystem and sends it to the general control subsystem. The general control subsystem drives the ground rail and the robot to move to the loading station work position. The robot's end effector grabs the replacement function module and transports it to the storage position of the cache subsystem.

[0014] After the complex and precise metal parts of the spacecraft are put into storage, the control subsystem automatically starts the corresponding production task according to the preparation of the parts in the production task, the idleness of the CNC machining center and the availability of the CNC machining program; after starting, the control subsystem sends the CNC machining program to the CNC machining center through network communication and the general control subsystem provides the start command, the CNC machining center mobilizes the automatic door to open and sends the automatic door opening signal to the general control subsystem, the general control subsystem sends a lock signal to the CNC machining center and then queries the control subsystem for the storage position of the exchange function module bound to the complex and precise metal parts of the spacecraft to be processed in the cache subsystem, the general control subsystem drives the ground rail and the robot to the position, the robot end effector grabs the exchange function module and transports it to the CNC machining center; the robot places the exchange function module on the zero-point positioning device, the general control subsystem sends a zero-point locking command to the CNC machining center, and drives the robot away from the CNC machining center and then sends a feeding completion signal to the CNC machining center; the CNC machining center mobilizes the automatic door to close and automatically executes the CNC machining program;

[0015] After the processing is completed, the CNC machining center mobilizes the automatic door to open, and sends the automatic door opening position and material picking call signal to the general control subsystem. The general control subsystem drives the robot and the ground rail to move to the position of the CNC machining center and grabs the replacement function module through the end of the robot, and sends a zero-point release command to the CNC machining center at the same time; after detecting the release, the general control subsystem drives the robot away from the CNC machining center and sends a material picking completion signal, and drives the robot and the ground rail to put the replacement function module back to the original storage position and feedback the production task completion signal to the control subsystem. The CNC machining center mobilizes the automatic door to close and sends an idle state to the control subsystem;

[0016] When the number of complex and precise metal parts for spacecraft processed in the cache subsystem reaches 20% of the inventory, the inventory warning function of the management and control subsystem is triggered, prompting the operator to take the parts away; the operator selects the replacement function module that needs to be shipped out through the human-computer interaction operation terminal of the loading station and starts the shipping operation; the general control subsystem responds to the shipping operation instruction and retrieves the location of the replacement function module from the management and control subsystem, and drives the robot and ground rail to take the replacement function module to the loading station. The operator unbinds the electronic tag information of the replacement function module from the part information through the human-computer interaction operation terminal of the loading station to complete the part shipping operation.

[0017] The replacement function module is composed of a bottom rivet and positioning pin, a side end effector and positioning pin, and a universal mounting and positioning device; the bottom positioning rivet is used in conjunction with the internal zero-point positioning device of the CNC machining center; the bottom positioning pin is used in conjunction with the cache subsystem and each storage position of the loading station, and the side end effector and positioning pin are used in conjunction with the end effector mechanism; a universal mounting and positioning device is provided on the top for installing a vise, a mechanical pressure plate or a positioning block to realize the mounting of complex and precise metal parts of the spacecraft.

[0018] The cache subsystem is composed of multiple groups of shelves, and the information management of parts entry, storage, and exit is realized through the management and control subsystem, realizing the correlation between the storage location of the replacement function module and the part information.

[0019] The master control subsystem is composed of a master control cabinet and a remote module, which provides an abnormal protection mechanism for the zero-point positioning device and a communication timeout protection mechanism; the remote module is deployed on the CNC machining center, the ground rail and the robot end, and the remote module communicates with the CNC machining center, the ground rail and the robot for IO to complete the transmission of the command signal. The master control cabinet is connected to each remote module and the control subsystem through the EtherCAT bus to realize the issuance and uploading of commands and production tasks; the master control cabinet is equipped with a PLC and yellow / green / red three-color lights to convert the production tasks issued by the control subsystem into process interpretations, and a minimum task unit database is established in combination with the task unit database and splicing rules. Multi-source data coupling decisions are realized through the feedback signals of the CNC machining center, the ground rail and the robot status, and the scheduling priority and unilateral coordination strategy of pick-and-place are configured to perform automatic indexing and splicing of tasks, so as to realize the arbitrary splicing and path reorganization of the robot to the task-driven cache library, CNC machining center, loading station, and ground rail pick-and-place multiple independent points during the operation of the production line, and drive the spatiotemporal linkage control of multiple machines.

[0020] The abnormal protection mechanism of the zero-point positioning device specifically includes a material discharge abnormal protection mechanism and a material collection abnormal protection mechanism;

[0021] Abnormal material discharge protection mechanism: When the CNC machining center calls for material discharge, the automatic door of the CNC machining center opens, the master control subsystem controls the zero-point positioning device to release, and dispatches the robot to enter the CNC machining center to detect the status of the zero-point positioning device. If the zero-point positioning device is locked abnormally at this time, the master control subsystem will drive the robot to automatically return the replacement function module to the cache subsystem, and send a zero-point abnormality alarm to the management and control subsystem. The master control subsystem will continue to respond to other call tasks to ensure that the production process is not affected;

[0022] Abnormal material picking protection mechanism: When the CNC machining center calls for material picking, the automatic door of the CNC machining center opens, and the general control subsystem directs the robot to enter the CNC machining center to grab the change function module, and controls the zero-point positioning device to release. If the zero-point locking is detected to be abnormal at this time, the general control subsystem will control the robot to stop moving and send a zero-point abnormality alarm to the management and control subsystem. At this time, the operator needs to intervene and manually release the zero-point positioning device while ensuring safety, and manually control the robot to continue to run automatically until the part is taken out of the CNC machining center and placed in the cache subsystem.

[0023] The timeout protection mechanism refers to the communication timeout and failure to respond between the master control subsystem and the management and control subsystem; the master control subsystem sends a production task call instruction to the management and control subsystem at regular intervals, and the management and control subsystem uses multiple threads to decompose the query instructions. One thread specifically listens to the task call message of the master control subsystem and puts it into multiple other threads, and the multiple threads are used to process the received task calls; and replies to the feedback instructions one by one to realize the timely issuance and response of the production tasks of the management and control subsystem and the master control subsystem. The master control subsystem verifies the task number of each feedback instruction, and executes it if the task number is consistent, otherwise stops the current call and starts the call of the next task; when the master control subsystem does not receive the feedback instruction of the current query instruction, the master control subsystem considers that the current call task has failed, and will also stop the current call task and turn to poll and call other tasks that need to be processed in turn until the management and control subsystem can correctly respond to the call task; when the master control system has exceeded the time threshold and still has not received any feedback instruction from the management and control subsystem, it considers that the communication has timed out, and drives the yellow indicator light of the master control cabinet to indicate the timeout status.

[0024] The control subsystem consists of an inventory management system, an intelligent production scheduling module, a human-computer interaction terminal interface, a display interface, and a monitoring interface; the intelligent production scheduling module receives the production plan from the company's information system and then indexes the corresponding number of parts in the inventory management system, and at the same time receives the CNC machining program created by the human-computer interaction terminal and associates the production plan, giving priority to the production plan that has completed production preparation, and providing priority management, allowing flexible scheduling for insertion orders; production tasks are issued according to the idleness of the CNC machining center, and the control subsystem has the interactive capability of simultaneous machining of multiple CNC machining centers and the management capability of simultaneous execution of multiple tasks, providing the ability to produce multiple different parts on mixed lines at the same time; the display interface provides the working status information of all CNC machining centers, robots, ground rails and master control PLCs, equipment utilization and scheduling information; the monitoring interface provides the internal processing screen of each CNC machining center for operators to use for remote monitoring.

[0025] The advantages of the present invention compared with the prior art are:

[0026] 1. The traditional complex automated processing system relies on foreign equipment. This system is developed using domestic CNC processing centers, building a local area network and the Internet for physical isolation to improve the confidentiality and security of the system.

[0027] 2. By independently developing a set of management and control subsystems, we can realize intelligent interaction between production scheduling, production preparation, and equipment working status, optimize production scheduling, and improve equipment utilization. We can also increase judgment and early warning mechanisms, carry out production preparation work in advance, and reduce the risk of production suspension and waiting.

[0028] 3. Traditional master control PLCs generally use IO communication to interact with various devices. The number of IO communication cables required to be laid is the same as the number of communication signals between the master control cabinet and various devices. The on-site construction workload is large, and signal troubleshooting and measurement after a fault is difficult. This system is designed using a master control PLC and a remote module. The remote module and various devices use IO communication and are integrated at the equipment manufacturer. At the debugging site, you only need to connect the network cable to achieve communication between the master control PLC and various devices. It has strong anti-interference capabilities, is easy to implement on site, and can quickly and clearly locate faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the schematic diagram of the flexible and automatic milling system for complex and precise metal parts of spacecraft.

[0030] Figure 2 This is the workflow diagram of the flexible and automatic milling system for complex and precise metal parts of spacecraft. DETAILED DESCRIPTION

[0031] like Figure 1 As shown, the present invention provides a flexible and automatic milling processing system for complex and precise metal parts of spacecraft. The system includes a CNC machining center, a loading and unloading subsystem, a changing function module, a cache subsystem, a general control subsystem, and a management and control subsystem. The system can undertake flexible and mixed-line milling processing of complex and precise metal parts made of two materials: aluminum alloy and aluminum-based silicon carbide.

[0032] The metal parts that can be processed by the system are mainly suitable for the processing of small and medium-sized structural parts with a size of 400mm×400mm×400mm and a processing cycle of more than 30min. Typical products include plate beams, boxes, simple brackets, and complex bracket parts.

[0033] The control subsystem mainly manages the more specific and detailed production task arrangement of the automation unit, production task display, parts and tool management combined with specific production tasks, operation status information display of each CNC machining center, and the issuance of machining programs according to production tasks. The general control subsystem is used to undertake functions such as part calling between the CNC machining center and the loading and unloading subsystem, the transmission of the automatic door status of the CNC machining center and the completion of part delivery, part location query between the warehouse management system (WMS), and part pick-and-place management.

[0034] CNC machining center

[0035] The CNC machining center is the main body of the system, which can carry out automatic machining of various parts and has three-axis, four-axis and five-axis machining capabilities. The machining center in the unit has automatic door management and can exchange information with the general control subsystem and production line control subsystem.

[0036] As a CNC machining center for automated processing, it should be seamlessly connected with the management and control subsystem and the general control subsystem, have good data command reception and feedback capabilities, and carry out automated interface and function design.

[0037] 1) Automatic door management function

[0038] In order to realize the automatic picking and placing of complex parts in the workstations of CNC machining centers, research and design of automatic doors for CNC machining centers were carried out to realize automatic control of side windows and doors of CNC machining centers as well as detection of opening and closing status.

[0039] 2) High-precision positioning function of the replacement function module

[0040] In the process of automated CNC machining, the position of the parts sent to the CNC machining center for processing each time on the workbench of the CNC machining center needs to be highly consistent. This requires precision constraints on the entire part transfer process, the consistency of part clamping, the consistency of the storage position and posture in the entire transfer path when the robot transfers the parts, and the consistency of the part posture after being placed in the CNC machining center all require targeted design.

[0041] In order to realize the rapid positioning of the replacement function module of the clamped parts in the CNC machining center, the zero-point positioning interface of the CNC machining center is developed, and a gas-liquid drive is provided. It has the functions of zero-point release, clamping control, opening and closing detection, and gas detection alarm for the presence or absence of the replacement function module. It is also equipped with a specified model of zero-point positioning device, which can adapt to the processing method of replacing the function module for clamping.

[0042] 3) Communication interface development

[0043] The control system of the CNC machining center has the following external output signals: material discharge call, material pickup call, function module change fixed in place, function module change loose in place, automatic door open in place, CNC machining center alarm, milling fluid low level prompt, milling fluid high level prompt, etc. It should also be able to receive robot discharge completion signal, robot pickup completion signal, zero point tension control signal and lock signal, etc. Each signal provides an independent IO point.

[0044] 4) Automated measurement technology

[0045] CNC machining centers should be equipped with high-precision infrared probes that can be called by CNC programs to achieve automated measurement during the machining process and improve machining precision and accuracy.

[0046] 5) Control system M instruction development

[0047] The CNC machining center has the ability to provide M instructions to CNC programming, including but not limited to CNC program control of automatic door opening, closing, calling for material pickup and placement, tool setting control, air blowing, etc.

[0048] Loading and unloading subsystem

[0049] The loading and unloading subsystem consists of a loading station, a ground rail, a robot and an end effector. The robot moves back and forth on the ground rail, covering the cache subsystem, the loading station and the CNC machining center to complete the automatic transfer of parts within the unit. The cache subsystem is used to temporarily store parts to be processed and parts to be shipped out after processing. The operator completes the clamping of the blank parts for processing and the disassembly of the finished parts at the loading station, and performs the binding / unbinding operations of the electronic tags of the functional modules and the part information and the entry and exit operations at the human-computer interaction operation terminal of the loading station. The WMS+RFID management method is adopted in the management of the cache subsystem and the loading station. The WMS is used to realize the information management of the warehousing, storage and shipment of parts. The RFID technology is used to realize the tracking of part information, which ensures the flexible mixed line and line change production of the processing unit.

[0050] The specific working process of the loading and unloading subsystem is as follows:

[0051] 1) The operator calls the replacement function module through the human-machine interactive operation terminal of the loading station. The control subsystem sends the replacement function module from the storage position of the cache subsystem to the general control subsystem. The general control subsystem drives the ground rail and the robot to move to the cache subsystem. The robot end effector grabs the replacement function module and transports it to the loading station work position. The operator places the complex and precise metal parts of the spacecraft on the replacement function module and locks it. The operator drives the RFID card reader on the human-machine interactive operation terminal of the loading station to read the electronic tag information of the replacement function module and bind the complex and precise metal parts information of the spacecraft. The bound information is fed back to the control subsystem. The operator starts the warehousing operation at the human-machine interactive operation terminal of the loading station. The control subsystem selects the storage position in the cache subsystem and sends it to the general control subsystem. The general control subsystem drives the ground rail and the robot to move to the loading station work position. The robot end effector grabs the replacement function module and transports it to the storage position of the cache subsystem.

[0052] 2) After the complex and precise metal parts of the spacecraft are put into storage, the control subsystem automatically starts the corresponding production task according to the preparation of the parts in the production task, the idleness of the CNC machining center, and the availability of the CNC machining program. After starting, the control subsystem sends the CNC machining program to the CNC machining center through network communication, and the general control subsystem provides the start command. The CNC machining center mobilizes the automatic door to open and sends the automatic door opening signal to the general control subsystem. The general control subsystem sends a lock signal to the CNC machining center and then queries the control subsystem for the storage position of the exchange function module bound to the complex and precise metal parts of the spacecraft to be processed in the cache subsystem. The general control subsystem drives the ground rail and the robot to this position, and the robot end effector grabs the exchange function module and transports it to the CNC machining center. The robot places the exchange function module on the zero-point positioning device, and the general control subsystem sends a zero-point locking command to the CNC machining center, and drives the robot away from the CNC machining center and sends a feeding completion signal to the CNC machining center. The CNC machining center mobilizes the automatic door to close and automatically executes the CNC machining program.

[0053] 3) After the processing is completed, the CNC machining center activates the automatic door to open, sends the automatic door opening and material picking call signals to the general control subsystem, and the general control subsystem drives the robot and the ground rail to the CNC machining center position and grabs the replacement function module through the robot end, and sends a zero-point release command to the CNC machining center. After detecting the release, the general control subsystem drives the robot away from the CNC machining center and sends a material picking completion signal, and drives the robot and the ground rail to put the replacement function module back to the original storage position and feedback the production task completion signal to the control subsystem. The CNC machining center activates the automatic door to close and sends an idle state to the control subsystem.

[0054] 4) When the complex and precise metal parts of the spacecraft processed in the cache subsystem reach 20% of the inventory, the inventory warning function of the control subsystem is triggered, prompting the operator to take the parts away. The operator selects the replacement function module that needs to be shipped out through the loading station human-computer interaction operation terminal and starts the outbound operation. After responding to the outbound operation instruction, the general control subsystem retrieves the location of the replacement function module from the control subsystem, and drives the robot and the ground rail to take the replacement function module to the loading station. The operator unbinds the electronic tag information of the replacement function module from the part information through the loading station human-computer interaction operation terminal. The parts outbound operation is completed.

[0055] WMS has upgraded the parts management mode and management level by building modules such as warehouse management, warehouse management, warehouse outgoing management, and comprehensive management and control, and using algorithms and other technologies. By combing and improving the work process, supplemented by RFID technology terminals, data from each stage such as product warehouse in and out and process matching is collected and managed, achieving seamless connection with the company's MES and ERP, ensuring the synchronization of information flow and logistics, and integrating with the company's existing information system, making information transparent, and improving work efficiency and production site management level.

[0056] Change function module

[0057] In the process of automated CNC machining, the position of the parts sent to the CNC machining center for processing each time on the workbench of the CNC machining center needs to be highly consistent. This requires precision constraints on the entire part transfer process, the consistency of part clamping, the consistency of the storage position and posture in the entire transfer path when the robot transfers the parts, and the consistency of the part posture after being placed in the CNC machining center all require targeted design.

[0058] In order to meet the above requirements, multiple interface gap size constraints were carried out for the card-loading and changing function module, loading station, in-line slow subsystem, robot end effector and zero-point positioning device. The vise was mainly used to ensure the consistency of the installation position of the parts on the changing function module. Secondly, the zero-point positioning device was used to ensure the consistency of the posture of the changing function module on the workbench of the CNC machining center. The interface design of the pallet placed on the loading station and the in-line slow subsystem of the changing function module ensured the consistency of the robot's pick-and-place position. The gaps between the robot end effector and the changing function module interface, the changing function module and the pallet stored in the in-line slow subsystem, and the changing function module and the loading station pallet storage interface were all controlled within 0.5mm. After the changing function module and the zero point were fastened, the multiple constraints shown in the figure below were adopted. The positioning piece realized the anti-rotation function through the design of the zero-point cross protrusion and the cross groove of the changing function module. The close cooperation between the rivet of the changing function module and the zero-point locking steel ball finally achieved an effect better than 0.005mm.

[0059] Master control subsystem

[0060] The master control subsystem consists of a master control cabinet and a remote module. The master control cabinet is equipped with a power supply and distribution system, a master control PLC module, an EtherCAT bus coupler, and green / yellow / red lights. As an intermediate system between the control subsystem and the execution unit, the master control subsystem is mainly responsible for the rapid transmission of information flow between the control subsystem, the ground rail, the robot, and the CNC machining center. It specifically realizes the response to the call tasks of the CNC machining center, the decomposition of production tasks, robot motion control, the control of the zero-point positioning device of the CNC machining center, the operation control of the CNC machining center, parts inspection, external manual key response, and process equipment status detection and upload. During the construction of the production line, there are many equipments with poor integration and obstructed multi-data communication. Through the design of the master control architecture, task multi-threaded resource allocation and EtherCAT bus coupling, the integrated control of robots, ground rails, end effectors, zero points, etc. is realized, the equipment operation space is expanded, the reconfigurability is enhanced, and the flexible and fast assembly of the production line is supported.

[0061] In terms of the hardware interconnection interface of each device, the remote module IO terminal is combined with the Ether CAT bus, and the remote module IO terminal module is directly deployed inside each CNC machining center, and the functions of each interface are constrained. It is directly integrated in the production and manufacturing process of the CNC machining center. After the CNC machining center enters the factory, it only needs to connect one network cable when communicating with the master control PLC. This technology is different from the traditional master control PLC and each CNC machining center. IO communication is carried out through intermediate relays, avoiding the need to connect a large number of cables, greatly shortening the on-site construction and debugging time, and using IO and communication dual power supply equipment to increase the reliability and stability of the system.

[0062] In order to solve the problem of multi-machine collaborative control caused by complex constraints of flexible processing technology, the general control subsystem establishes a task unit database and splicing rules for process interpretation, and innovatively establishes a minimum task unit database. It automatically indexes and splices tasks through multi-source data coupling decision-making, scheduling priority and unilateral coordination strategies, and realizes arbitrary splicing and path reorganization of a total of 327 independent points such as task-driven cache libraries, CNC machining centers, loading stations, and ground rail pick-and-place during production line operation, thereby driving multi-machine spatiotemporal linkage control.

[0063] Fault-Tolerant Design of Master Control Subsystem

[0064] 1) Design of protection measures for zero point abnormality

[0065] Due to the large number of zero-point anomalies that occurred in the early stage, targeted designs were carried out for the zero-point anomalies in the two states of unloading and picking up materials in the CNC machining center.

[0066] When the CNC machining center calls for material discharge, the automatic door of the CNC machining center opens, the master control subsystem controls the zero-point positioning device to release, and the robot will detect the zero-point status before entering the CNC machining center. If the zero-point positioning device is locked abnormally at this time, the master control subsystem will command the robot to automatically return the parts to the cache, and send a zero-point abnormality alarm to the management and control subsystem. The master control subsystem will continue to respond to other tasks to ensure that the production process is not affected.

[0067] When the CNC machining center calls for material collection, the automatic door of the CNC machining center opens, and the general control subsystem directs the robot to enter the CNC machining center to grab the change function module and control the zero point to release. If the zero point locking is detected to be abnormal at this time, the general control subsystem will control the robot to stop moving and send a zero point abnormality alarm to the management and control subsystem. At this time, the operator needs to intervene and manually release the zero point while ensuring safety, and control the robot to continue to run automatically through the teach pendant until the part is taken out of the CNC machining center and placed in the cache.

[0068] 2) Design of protection measures for communication timeout between the master control and control subsystems

[0069] When the communication time between the on-site master control subsystem and the management and control subsystem deployed on the server side of the computer room is too long or the communication is stuck, it will not work for a long time, and the management personnel need to intervene to deal with it, which affects the automatic processing efficiency. In order to deal with the malfunction caused by long-term lack of feedback or communication anomalies during the communication process, a timeout check and information check mechanism are added to the master control and management and control communication.

[0070] When the communication line is unstable or the control subsystem is unable to process the current task call of the master control subsystem due to the long-term occupation of the main process by processing other tasks, it is mainly manifested as when there is a CNC machining center that needs to pick up and place materials or parts that need to be put in and out of the warehouse, the robot will not work for a long time. To solve this problem, the master control subsystem has added a timeout detection mechanism. The master control subsystem detects that the control subsystem does not respond to the call task. The master control subsystem believes that the current call task has failed, and will stop the current call task and poll other tasks that need to be processed in turn until the control subsystem can respond to the call task correctly. When the control subsystem still does not receive feedback instructions for 30s, it determines that the communication has timed out, and the yellow light of the drive master control cabinet is on, indicating a communication timeout fault. The addition of this mechanism can automatically restore the system to normal operation in the event of a short-term communication timeout, avoiding frequent standby and requiring manual intervention, and reducing the impact on the automated processing process.

[0071] The master control PLC is a real-time system based on hardware, which can process information at high speed; the management and control subsystem runs on the server and depends on the server's operating system. It is a non-real-time system, but its advantage is that it can process various information synchronously in multiple threads. When the real-time system and the non-real-time system are interacting with each other at high speed, communication timeout will bring some additional problems. When the master control subsystem controls the robot to discharge materials to the CNC machining center, the master control subsystem needs to initiate a discharge request to the control subsystem and inquire about the storage location of the parts processed by the CNC machining center. For example, the master control subsystem asks the control subsystem for the discharge call of CNC machining center No. 3. After the timeout, the master control subsystem will stop the discharge call of CNC machining center No. 3 and re-initiate a new task for the discharge call of CNC machining center No. 1. At this time, the control subsystem has just processed the discharge call No. 3 due to blocking, and feedbacks the storage location of the parts of CNC machining center No. 3. If the master control subsystem does not verify the task information of the control response, the parts processed by CNC machining center No. 3 will be placed in CNC machining center No. 1, resulting in the wrong parts. Based on the above considerations, the master control subsystem needs to verify the task number of the feedback information of the control subsystem to avoid performing wrong actions.

[0072] Control subsystem

[0073] As the management system of the entire processing unit, the control subsystem undertakes various functions such as production task scheduling, processing task management, WMS management, CNC program management, equipment management, tool management, shift management, and authority management, and provides a human-computer interactive operation terminal interface, display interface, and monitoring interface. In order to save development time, the control subsystem adopts a mature software architecture and deploys various functional modules in a microservice manner. During the design and development of the control subsystem, the following technologies have been explored.

[0074] 1) Data collection and automatic program distribution of CNC machining centers

[0075] Through the investigation of Siemens CNC machining center, the OPC UA communication method is used to interact with the CNC machining center to realize the automatic distribution of CNC programs, the acquisition of CNC machining center files and the internal data of the CNC machining center.

[0076] In the early stage, the three-axis CNC machining center was tested through the OPC UA standard client to gradually master the variable information that needs to be collected. By comparing the two ways of sending CNC programs, FTP and OPC UA communication, the convenience and high reliability of OPC UA communication were finally determined.

[0077] 2) Design of WMS parts storage algorithm

[0078] According to the processing tasks assigned to each CNC machining center, the optimal path algorithm for parts storage is designed. The empty exchange function module, ordinary parts, super-high parts, super-wide parts, and super-high and super-wide parts are distinguished. The priority is set in the algorithm for placing the cache library. Super-wide parts, super-high and super-wide parts are the first priority, super-high parts are the second priority, and ordinary parts and empty exchange function modules are the third priority. When placing parts in the cache library, it is necessary to judge the specifications of the current parts and the position and specifications of the parts that already exist in the shelf to be placed. Different logical judgments are made for parts of different specifications to prevent collisions of placed parts.

[0079] 3) High-speed data interaction design between real-time system and non-real-time system

[0080] The data interaction between the control subsystem and the master control subsystem needs to solve the problem of reliability of interaction between real-time and non-real-time systems. In order to adapt to the millisecond-level message sending and receiving instructions of the master control subsystem, the control subsystem uses multi-threading for action disassembly. One thread specifically listens to the task request message of the master control subsystem and puts it into multiple other threads. These multiple threads are specifically used to process the received task requests. And reply one by one to achieve close linkage between the control subsystem and the master control subsystem. When the master control system does not receive the feedback signal from the control subsystem for more than 30 seconds, it considers that the communication has timed out, and drives the yellow indicator light of the master control cabinet to indicate the timeout status.

[0081] like Figure 2 FIG. 1 shows the workflow of the flexible and automatic milling system for complex precision metal parts of a spacecraft according to an embodiment of the present invention, and the steps are as follows:

[0082] (1) Create a production task in the control subsystem through the loading station human-computer interaction operation terminal, and split the production plan received by the control subsystem in the company information system into system processing orders according to the process to form a production task;

[0083] (2) Clamp the parts at the loading station and clamp the blank parts to be processed on the function module;

[0084] (3) The replacement function module with the parts to be processed is sent into the unit, and the storage operation is performed through the corresponding interface of the control subsystem. The general control subsystem calls the robot and the ground rail to move the parts to be processed to the in-line cache subsystem;

[0085] (4) The control subsystem automatically sends the production task to the CNC machining center. The CNC machining center opens the automatic door and calls the general control subsystem to deliver the material. The general control subsystem calls the robot and the ground rail to move the parts to be processed to the CNC machining center according to the call signal and the location of the storage area of ​​the functional module.

[0086] (5) Start automatic processing. The control subsystem starts the processing task of the CNC machining center in a timely manner according to the task completion status of the general control subsystem, the CNC machining center, and the loading and unloading subsystem. The CNC machining center executes the processing process according to the CNC program until the processing is completed;

[0087] (6) After processing is completed, the CNC machining center calls the master control subsystem to pick up the parts. The master control subsystem calls the robot and ground rail of the loading and unloading subsystem to take the processed parts out of the CNC machining center and place them on the in-line slow-down subsystem;

[0088] (7) The control subsystem sends a warehouse-out instruction, and the robot sends the pallet back to the loading station. The operator operates the warehouse-out instruction through the human-machine interface of the loading station, and the general control subsystem calls the robot and ground rail of the loading and unloading subsystem to take the processed parts out of the in-line slow-down subsystem and place them on the loading station;

[0089] (8) Parts are disassembled. The operator removes the processed parts from the self-replacement function module, and the processing of the parts is completed.

[0090] The present invention solves the bottleneck problem of high-precision, high-efficiency, high-reliability and high-stability processing of complex structural precision parts of spacecraft, and improves the technical maturity of major national special tasks such as manned spaceflight and deep space exploration. The main research and development goal of the present invention is to focus on the milling processing of complex metal structural parts, mainly to overcome the precision processing accuracy of CNC machining centers, domestic substitution and post-processing quality measurement and evaluation technology, and focus on solving the most critical processing link automation improvement in the workshop production process. Compared with the goal of the smart processing factory, the production line is driven by process data, intelligent scheduling and decision-making, and develops a full-workshop intelligent production control platform, focusing on the information management of parts and processing equipment, production plan task decomposition, scheduling and decision-making, combining the information chain constructed by the general control subsystem and each processing equipment, opening up the entire vertical link from demand management to task production in the smart workshop, and the virtual model simulation results are fed back to each link in the production process, realizing the interconnection and real-time integration of virtual model information and actual physical information, realizing immediate solution of production process problems, making production predictions in advance and making intelligent production decisions based on data analysis, and ensuring efficient and reliable operation of the intelligent production line.

[0091] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A flexible and automatic milling system for complex and precise metal parts of spacecraft, characterized in that: include: CNC machining center, loading and unloading subsystem, changing function module, cache subsystem, general control subsystem and management and control subsystem; the CNC machining center completes the milling processing operation of spacecraft precision metal parts by communicating with the general control subsystem and the management and control subsystem; the loading and unloading subsystem is used to undertake the automated distribution operation of the changing function module between the CNC machining center and the cache subsystem; the changing function module is used to lock the spacecraft precision metal parts to be processed and the processed spacecraft precision metal parts; the cache subsystem is used to store the changing function module; the general control subsystem is used to complete the transmission of instructions with the CNC machining center, the driving of the loading and unloading subsystem, the issuance of production tasks and the feedback of production status with the management and control subsystem.

2. A flexible and automatic milling system for complex and precise metal parts of spacecraft according to claim 1, characterized in that: The CNC machining center is equipped with an automatic door, an automatic probe and a zero-point positioning device, has a recording function, and is deployed with a remote module for communicating with the general control subsystem; the CNC machining center and the general control subsystem realize IO communication through the remote module, and the interactive signals include automatic door opening / closing in place, material discharge call, material discharge completion, material collection call, material collection completion, lock signal, zero-point locking / relaxing, start, and stop signals; the CNC machining center and the management and control subsystem communicate through the network port to realize the reception of CNC machining programs, as well as idle, working, and fault status information feedback.

3. A flexible and automatic milling system for complex and precise metal parts of spacecraft according to claim 2, characterized in that: After the CNC machining center receives the CNC machining program and obtains the start-up command, it activates the automatic door to open, sends the working status to the management and control subsystem, sends the automatic door opening and material discharge call signal to the general control subsystem, controls the locking of each spindle after receiving the lock signal, and locks the function module changer on the zero point positioning device after the CNC machining center receives the zero point locking signal; when the material feeding completion signal is received, the automatic door is called to close, and the automatic probe is enabled to carry out the positioning accuracy detection of the function module changer, and the CNC machining program is started after the positioning accuracy is better than the preset value; after executing the CNC machining program, the CNC machining center calls the automatic door to open and sends the automatic door opening and material collection call signal to the general control subsystem, and controls the zero point positioning device to release after receiving the zero point release command, and the function module to be replaced leaves the CNC machining center and receives the material collection completion signal, calls the automatic door to close, and sends the idle status to the management and control subsystem.

4. A flexible and automatic milling system for complex and precise metal parts of spacecraft according to claim 2, characterized in that: The loading and unloading subsystem consists of a loading station, a ground rail, a robot and an end effector; the robot moves back and forth on the ground rail, and the robot's motion trajectory covers the CNC machining center, all storage locations of the cache subsystem and the loading station work positions. The end effector can pick up and place functional modules to complete the automatic transfer of complex and precise metal parts of the spacecraft within the unit.

5. A flexible and automatic milling system for complex precision metal parts of spacecraft according to claim 4, characterized in that: The loading station provides a human-machine interactive operation terminal and is equipped with an RFID radio frequency card reader, which is used to complete the clamping of the replacement function module of the complex and precise metal parts of the spacecraft to be processed and the disassembly of the replacement function module of the complex and precise metal parts of the spacecraft after processing; the operator can drive the RFID card reader to read the electronic tag information of the replacement function module through the human-machine interactive operation terminal, bind the tag information of the replacement function module with the part information and upload it to the management and control subsystem, so as to realize the out-of-warehouse and in-warehouse operations of the replacement function module.

6. A flexible and automatic milling system for complex and precise metal parts of spacecraft according to claim 5, characterized in that: The specific working process of the loading and unloading subsystem is as follows: The operator calls the replacement function module through the human-machine interactive operation terminal of the loading station. The management and control subsystem sends the replacement function module at the storage position of the cache subsystem to the general control subsystem. The general control subsystem drives the ground rail and the robot to move to the cache subsystem. The robot's end effector grabs the replacement function module and transports it to the loading station work position. The operator places the complex and precise metal parts of the spacecraft on the replacement function module and locks it. The operator drives the RFID card reader on the human-machine interactive operation terminal of the loading station to read the electronic tag information of the replacement function module and bind the complex and precise metal parts information of the spacecraft. The bound information is fed back to the management and control subsystem. The operator starts the warehousing operation at the human-machine interactive operation terminal of the loading station. The management and control subsystem selects the storage position in the cache subsystem and sends it to the general control subsystem. The general control subsystem drives the ground rail and the robot to move to the loading station work position. The robot's end effector grabs the replacement function module and transports it to the storage position of the cache subsystem. After the complex and precise metal parts of the spacecraft are put into storage, the control subsystem automatically starts the corresponding production task according to the preparation of the parts in the production task, the idleness of the CNC machining center and the availability of the CNC machining program; after starting, the control subsystem sends the CNC machining program to the CNC machining center through network communication and the general control subsystem provides the start command, the CNC machining center mobilizes the automatic door to open and sends the automatic door opening signal to the general control subsystem, the general control subsystem sends a lock signal to the CNC machining center and then queries the control subsystem for the storage position of the exchange function module bound to the complex and precise metal parts of the spacecraft to be processed in the cache subsystem, the general control subsystem drives the ground rail and the robot to the position, the robot end effector grabs the exchange function module and transports it to the CNC machining center; the robot places the exchange function module on the zero-point positioning device, the general control subsystem sends a zero-point locking command to the CNC machining center, and drives the robot away from the CNC machining center and then sends a feeding completion signal to the CNC machining center; the CNC machining center mobilizes the automatic door to close and automatically executes the CNC machining program; After the processing is completed, the CNC machining center mobilizes the automatic door to open, and sends the automatic door opening position and material picking call signal to the general control subsystem. The general control subsystem drives the robot and the ground rail to move to the position of the CNC machining center and grabs the replacement function module through the end of the robot, and sends a zero-point release command to the CNC machining center at the same time; after detecting the release, the general control subsystem drives the robot away from the CNC machining center and sends a material picking completion signal, and drives the robot and the ground rail to put the replacement function module back to the original storage position and feedback the production task completion signal to the control subsystem. The CNC machining center mobilizes the automatic door to close and sends an idle state to the control subsystem; When the number of complex and precise metal parts for spacecraft processed in the cache subsystem reaches 20% of the inventory, the inventory warning function of the management and control subsystem is triggered, prompting the operator to take the parts away; the operator selects the replacement function module that needs to be shipped out through the human-computer interaction operation terminal of the loading station and starts the shipping operation; the general control subsystem responds to the shipping operation instruction and retrieves the location of the replacement function module from the management and control subsystem, and drives the robot and ground rail to take the replacement function module to the loading station. The operator unbinds the electronic tag information of the replacement function module from the part information through the human-computer interaction operation terminal of the loading station to complete the part shipping operation.

7. A flexible and automatic milling system for complex precision metal parts of spacecraft according to claim 4, characterized in that: The replacement function module is composed of a bottom rivet and positioning pin, a side end effector and positioning pin, and a universal mounting and positioning device; the bottom positioning rivet is used in conjunction with the internal zero-point positioning device of the CNC machining center; the bottom positioning pin is used in conjunction with the cache subsystem and each storage position of the loading station, and the side end effector and positioning pin are used in conjunction with the end effector mechanism; a universal mounting and positioning device is provided on the top for installing a vise, a mechanical pressure plate or a positioning block to realize the mounting of complex and precise metal parts of the spacecraft.

8. The flexible and automatic milling system for complex and precise metal parts of spacecraft according to claim 1 is characterized in that: The cache subsystem is composed of multiple groups of shelves, and the information management of parts entry, storage, and exit is realized through the management and control subsystem, thereby realizing the correlation between the storage location of the replacement function module and the part information.

9. The flexible and automatic milling system for complex and precise metal parts of spacecraft according to claim 4 is characterized in that: The master control subsystem is composed of a master control cabinet and a remote module, which provides an abnormal protection mechanism for the zero-point positioning device and a communication timeout protection mechanism; the remote module is deployed on the CNC machining center, the ground rail and the robot end, and the remote module communicates with the CNC machining center, the ground rail and the robot for IO to complete the transmission of the command signal. The master control cabinet is connected to each remote module and the control subsystem through the EtherCAT bus to realize the issuance and uploading of commands and production tasks; the master control cabinet is equipped with a PLC and yellow / green / red three-color lights to convert the production tasks issued by the control subsystem into process interpretations, and a minimum task unit database is established in combination with the task unit database and splicing rules. Multi-source data coupling decisions are realized through the feedback signals of the CNC machining center, the ground rail and the robot status, and the scheduling priority and unilateral coordination strategy of pick-and-place are configured to perform automatic indexing and splicing of tasks, so as to realize the arbitrary splicing and path reorganization of the robot to the task-driven cache library, CNC machining center, loading station, and ground rail pick-and-place multiple independent points during the operation of the production line, and drive the spatiotemporal linkage control of multiple machines.

10. A flexible and automatic milling system for complex precision metal parts of spacecraft according to claim 9, characterized in that: The abnormal protection mechanism of the zero-point positioning device specifically includes a material discharge abnormal protection mechanism and a material collection abnormal protection mechanism; Abnormal material discharge protection mechanism: When the CNC machining center calls for material discharge, the automatic door of the CNC machining center opens, the master control subsystem controls the zero-point positioning device to release, and dispatches the robot to enter the CNC machining center to detect the status of the zero-point positioning device. If the zero-point positioning device is locked abnormally at this time, the master control subsystem will drive the robot to automatically return the replacement function module to the cache subsystem, and send a zero-point abnormality alarm to the management and control subsystem. The master control subsystem will continue to respond to other call tasks to ensure that the production process is not affected; Abnormal material picking protection mechanism: When the CNC machining center calls for material picking, the automatic door of the CNC machining center opens, and the general control subsystem directs the robot to enter the CNC machining center to grab the change function module, and controls the zero-point positioning device to release. If the zero-point locking is detected to be abnormal at this time, the general control subsystem will control the robot to stop moving and send a zero-point abnormality alarm to the management and control subsystem. At this time, the operator needs to intervene and manually release the zero-point positioning device while ensuring safety, and manually control the robot to continue to run automatically until the part is taken out of the CNC machining center and placed in the cache subsystem.

11. The flexible and automatic milling system for complex and precise metal parts of spacecraft according to claim 9, characterized in that: The timeout protection mechanism refers to the communication timeout and failure to respond between the master control subsystem and the management and control subsystem; the master control subsystem sends a production task call instruction to the management and control subsystem at regular intervals, and the management and control subsystem uses multiple threads to decompose the query instructions. One thread specifically listens to the task call message of the master control subsystem and puts it into multiple other threads, and the multiple threads are used to process the received task calls; and replies to the feedback instructions one by one to realize the timely issuance and response of the production tasks of the management and control subsystem and the master control subsystem. The master control subsystem verifies the task number of each feedback instruction, and executes it if the task number is consistent, otherwise stops the current call and starts the call of the next task; when the master control subsystem does not receive the feedback instruction of the current query instruction, the master control subsystem considers that the current call task has failed, and will also stop the current call task and turn to poll and call other tasks that need to be processed in turn until the management and control subsystem can correctly respond to the call task; when the master control system has exceeded the time threshold and still has not received any feedback instruction from the management and control subsystem, it considers that the communication has timed out, and drives the yellow indicator light of the master control cabinet to indicate the timeout status.

12. A flexible and automatic milling system for complex precision metal parts of spacecraft according to claim 11, characterized in that: The control subsystem consists of an inventory management system, an intelligent production scheduling module, a human-computer interaction terminal interface, a display interface, and a monitoring interface; the intelligent production scheduling module receives the production plan from the company's information system and then indexes the corresponding number of parts in the inventory management system, and at the same time receives the CNC machining program created by the human-computer interaction terminal and associates the production plan, giving priority to the production plan that has completed production preparation, and providing priority management, allowing flexible scheduling for insertion orders; production tasks are issued according to the idleness of the CNC machining center, and the control subsystem has the interactive capability of simultaneous machining of multiple CNC machining centers and the management capability of simultaneous execution of multiple tasks, providing the ability to produce multiple different parts on mixed lines at the same time; the display interface provides the working status information of all CNC machining centers, robots, ground rails and master control PLCs, equipment utilization and scheduling information; the monitoring interface provides the internal processing screen of each CNC machining center for operators to use for remote monitoring.

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