Research on NC Embedded PC Type Open CNC System

At present, various advanced manufacturing technologies have been rapidly developed, and most of them require the support of numerical control technology. However, since the traditional numerical control system is almost closed, at the same time, most machine tool manufacturers use standard numerical control devices to configure the machine tool, which makes it difficult to flexibly configure the function and user interface of the numerical control device under different use conditions. Because standard controls do not reflect the experience of the machine tool builder, it is difficult to meet the special requirements of the end user. Therefore, new requirements are put forward for the numerical control system. At the same time, with the diversification of user needs, the production mode is moving towards small and medium-sized batches, and the CNC system is required to be more flexible, flexible and versatile. Therefore, the research on the structure of open CNC system has emerged. Many countries in the world have invested a lot of manpower, material and financial resources to study it, and have achieved great results. For example, the open CNC system has software openness and hardware openness, which enables people to freely choose CNC. Devices, servo amplifiers, sensors, actuators, and more. In general, an open CNC system should have the following characteristics: It consists of logically independent components.

Provide a standard and specification to ensure that the conforming components of different manufacturers can form a complete CNC system.

The topology of the CNC system can be dynamically changed.

Interoperability with other systems or software modules.

Provide a consistent and consistent human-machine interface.

Due to the rapid development of computer technology and its standardization and openness, a PC-based open CNC system has emerged. At the same time, the CNC system is popular because of its high performance/price ratio and strong market competitiveness.

1 PC-based open CNC system PC-based open CNC system can make full use of computer hardware and software resources, can use the general high-level language to easily program, users can easily combine standardized peripherals, application software and use. Using a computer is also easy to network. PC-based open CNC systems can be roughly divided into four types, namely PC-connected CNC, PC-embedded CNC, NC-embedded PC (NC embedded PC), full-software NC. PC-connected CNC: this type of system It is composed of a common serial cable connecting an existing prototype CNC to a PC. The system is easy to implement, and the prototype CNC can be used almost without modification. General-purpose software can also be used, but the prototype CNC cannot be opened, and the communication and response speed of the system is slow.

PC embedded type CNC: This type of system is to load the PC into the CNC, and the PC and the CNC are connected by a dedicated bus. The system data transmission is fast and the response is rapid. At the same time, the prototype CNC system can be utilized without modification, but the general purpose PC cannot be directly used, and the openness is limited.

NC embedded PC (NC embedded PC type): This type of system is composed by inserting a dedicated CNC card into the expansion slot of the general-purpose PC.

It can fully guarantee system performance, software versatility, and flexible programming, but prototype CNC resources are difficult to use.

Full software type NC: This type of system means that all functions of the CNC are handled by the PC, and the servo drive is controlled by the servo interface card installed in the expansion slot of the PC. The software has good versatility and flexible programming. However, the implementation of real-time processing is difficult, and it is difficult to ensure the performance of the system, while the prototype CNC resources are difficult to use.

2NC embedded PC type open CNC system 21NC embedded PC type open CNC system application platform as PC-based open CNC system, NC embedded PC type open CNC system application platform can be understood as composed of open motion control card + PC . Open motion control cards generally use high-speed DSP as the CPU, with powerful motion control and logic control capabilities, and provide a set of CNC kernel APIs for users to develop and build the required CNC system. PCs usually use industrial computers to take full advantage of their rich hardware and software resources. Users can choose from many popular programming software such as DELPHI, VISUALC++, C++BUILDER and so on. This can greatly improve the user interface, graphic display, dynamic simulation and network communication functions of the CNC system. The typical structure of the NC embedded PC type open CNC system application platform is given.

System K sets I application i to the factory numerical control kernel AH communication system 丨 operating system hardware industrial computer 1 open motion controller NC embedded PC type open CNC system application platform typical structure 22NC and PC communication problems can be seen from When applying development on this CNC system platform, the first thing that must be solved is the communication problem between the NC and the PC. That is to say, the NC and the PC should be able to exchange data smoothly. The communication between them can be realized by different communication mechanisms, such as bus communication and dual-port RAM communication. The bus communication adopts the ISA/PCI bus structure, and the open motion control card is inserted in the bus interface slot of the PC, and the communication between the PC and the NC is established by using the corresponding control register and protocol, which can use the query mode or the interrupt mode. . Dual-port RAM communication uses a special type of memory. The memory has two ports that can be connected to the CPU of the PC and the NC. The two CPUs can read and write to each other without interference. Can significantly improve the speed of data exchange.

In order to make the communication system not depend on the specific communication mechanism, the above communication method is abstracted to obtain a consistent application program interface.

Ensure that users only need to access the application interface without having to care about the underlying communication mechanism to establish the required communication. The communication system is described.

The application software is compiled using COM component technology. COM components are actually small binary executables that serve applications, system programs, and other COM components. COM component objects are accessed through standard COM component interfaces and are linked together to form a complete application.

Using COM component architecture applications have a number of advantages: application customization, by replacing COM component objects with the same COM component interface, to achieve different application functions.

The application's rapid architecture, which selects the required components from the component library and quickly assembles the applications required for the architecture, shortens the application development cycle.

The application's dynamic architecture dynamically removes or replaces components without recompiling, dynamically changing application functionality.

It can be seen that COM component technology is very suitable for developing open CNC application systems.

According to the different functions of the numerical control system, the modules are divided, such as logic control, motion control, dynamic simulation, human-machine interface and other modules. These modules are then packaged using COM component technology and the corresponding CNC kernel API, whereby each module has a uniform COM component interface, so that the CNC application modules of different vendors can be interchanged. Make user customization possible.

The 24 system configuration software combines the scattered individual COM components into a numerical control application system that meets the user's requirements by the system configuration software. The system configuration software can instantiate the COM components in the COM component library according to the user's choice, and combine and assemble them into an application system with specific functions. When the user's needs change, the corresponding COM component can be replaced by the system configuration software or the COM component with some required functions can be added to adapt to the change of demand.

3 Case Study This paper developed an manipulator interface and an operation panel for NC embedded PC type open CNC application system. The application platform of this example adopts the open motion control card MWIPMAC of the American DELTATAU company. The MWI-PMAC can control two axes at the same time. It has strong motion control and logic control capability, and it is inserted in the ISA bus interface slot of the microcomputer. The system also uses two fully digital AC servo drives (MR-2) and AC servo motors. Plus a CNC interface chassis with I/O interface and analog output/feedback interface terminal board. The operating system on the microcomputer is Wiodows95, which uses DELPHI as the development language. The structure of the entire platform system is as shown.

The human-machine interface application system developed by the operation panel application system platform block diagram provides the user with an operation interface, and the user completes the corresponding operation by clicking the mouse. The function modules realized are programming, automatic machining, manual operation and motion trajectory drawing. The overall framework of the application system is as shown.

I programming automatic processing I 丨 manual operation 丨 I track tracing I operation panel user interface application system overall framework 3.1 communication module communication module is a necessary module for information exchange between the microcomputer and the PMAC motion control card, it realizes the query-based method Bus communication and dual port RAM communication. The two-port RAM communication is discussed more specifically here. There is a dual port RAM on the PMAC motion control card. The microcomputer and PMAC motion control card can share this dual port RAM. In order to use the dual port RAM, 16K of unoccupied storage space is selected on the microcomputer, and the storage space is The starting address is set to the starting address of the dual port RAM on the microcomputer. Then, the segment address of the starting address is written into the memory of the PMAC motion control card in the X storage space with the address values ​​of 786 and 787, and the PMAC motion control card can use the two memories to determine the address of the dual port RAM, thereby realizing Dual port RAM communication.

3.2 Programming Module The programming module provides the user with a graphical interface, which allows the user to quickly and easily program the NC program. It mainly has the function of inserting, deleting and modifying the NC program.

3.3 Manual Operation Module The manual operation module implements functions such as zero return and incremental feed. Their implementation is mainly through the use of PMAC online commands. The corresponding online command is sent to the PMAC through the bus communication, and the PMAC receives the command and executes it.

3.4 Automatic Machining Module The automatic processing module is relatively simple to implement by starting the motion program stored on the PMAC board. However, the position and speed of the motion axis must be acquired in real time and displayed.

3.4 Track Drawing Module The tool path drawing function is implemented by using the powerful logic control capability of PMAC, running the PLC program on the PMAC board, reading the current tool position information in real time, and then dynamically drawing the tool position information with curves. Come out, so that the change of the tool path can be visually observed on the screen. The tool path is drawn using a control PAINTBOX of DELPHI. When the motion program runs 0 inch, PMAC has a PLC program to read the current position information, store the information in the dual port RAM, and the microcomputer reads the dual port RAM through the TIMER control. After the above position information, the pixel point of the current position of the tool is drawn on the PAINTBOX control, thus realizing the dynamic depiction of the tool path.

It is the window of the human interface application system.

(Go to page 37) The Boolean operation is used to obtain the solid model of the plug-in and the plug-in. Then, the calculated intersecting lines are drawn on the theoretical reference object with different colors. The calculation is well tested by comparison. Whether the intersecting line is consistent with the intersecting line in the solid model, that is, the correctness of the digital model is tested, see the intersecting line verification. The function of the 3NC command generation NC command generation module is to generate the NC command corresponding to the CNC machine tool and its machine tool adjustment file. The machine tool adjustment file contains the pipe fitting design parameters, the blanking size, the process parameters to be adjusted during the machining process, and the tool setting position. The file is printed and sent to the CNC operator. The CNC command file is transmitted to the CNC machine by floppy disk or RS232C communication. The system generates four data files at a time: the plug-in NC program file and the machine tool adjustment file, and the plug-in NC program file and the machine tool adjustment file.

3.4 Machining Simulation Machining simulation is realized by reverse simulation, that is, by reading the NC program generated by the previous step and the machine adjustment file. The machining process is validated to validate the future machining process, ensuring the correct machining of the workpiece. The idea of ​​machining simulation of the system is to simulate the mechanism of the experimental cutting process. The process of cutting all the pipe fittings (flame, plasma arc, laser) in the process is to form the hole first, and the machine tool moves according to the specified trajectory to make the hole continuous and narrow. Cut the seams. Machining simulation is done using this. First read the NC program file and the machine adjustment file, automatically draw the cutting head and the tube hair, and then let the cutting head automatically enter the tool setting point according to the size of the tool position. Then control the MDT command on the pipe point at the tool point. The hole (hole) is then read through the program loop, and the command data is obtained to make the pipe rotate, the cutting head moves AX, AZ goes to the next cutting point, and then a hole is punched. Since the step size is small and there is no interpolation motion and a continuous cut is formed, the entire simulation process is completed.

In order to show this process, a process simulation process diagram with a large step size is drawn.

4 Conclusion The key to NC cutting of the intersecting line of pipe fittings is to establish a mathematical model of the NC cutting intersecting line corresponding to the principle of CNC cutting. This paper combines the actual situation of the factory to provide a complete solution for the NC machining of the pipe-like intersecting line. The graphical interactive automatic programming system developed enables the programmer to get rid of the complicated mathematical processing. The system has the characteristics of straightforward, vivid image, convenient use and simple operation, which greatly facilitates the programmers and operators, and has strong practical value and promotion value. In addition, the slightly improved algorithm of this paper is also applicable to the generation of CAD and unfolding CNC cutting program for pipe-like sheet metal.

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