under.
Industrial CT is an advanced instrument developed on the basis of medical CT for non-destructive testing and flaw detection of industrial products. It is the abbreviation of industrial computed tomography. The products to be evaluated are as small as a millimeter and as large as several meters. It is the best non-destructive testing in the handicraft industry. Compared with medical CT, the CT has a significant difference in structure. Modern medical CT is to keep the patient still, so it is quite large. Moving parts with complex electromechanical devices 21. Industrial CT is to keep the source and detector system stationary or to make a small amount of movement, and the necessary scanning motion is performed by the workpiece to be tested. This saves some trouble, but because industrial inspection often requires high precision, the sample scanning table is still a very precise key component.
The performance of tomographic motion control directly affects the operation of the CT device and the reliability of the acquired data, and ultimately affects the imaging quality. Therefore, scanning motion control systems are a very important part of industrial CT.
1 system overall structure The scanning and translational motion of the scanning platform adopts periodic variable speed continuous motion, and the shifting period should be designed so that the motion of one cycle includes two parts: the first part is fast rotation or translation, and the stepping is realized; the second part is slow. Speed ​​rotation or translation to complete the integral sampling of the ray projection. From the angle that the spatial expansion of the projection unit of the guarantee member is small during the integral sampling process and the exposure time (integration) of the probe is long, it is desirable that the motion speed of the scanning platform is as small as possible during the integral sampling. The above movement requirements, and to ensure the reliability and stability of the movement, Koimorgen's products were selected to complete the motion control of the scanning platform. Direct drive linear servo motor (DDL), direct drive rotary motor (DDR), servo motor, driver and multi-axis control card (ServoStarMC) were selected.
The multi-axis control card MC selected for this project is a four-axis control card. It communicates with each motor directly driving the rotary motor, linear motor and AC servo motor through the SERCOS bus. The communication with the stepper motor driver is realized by the digital I/O port on the MC card. The hardware connection structure of the system is as follows.
According to the system design, the network communication about the upper and lower machines should be completed by the host to the 'motion platform initialization' of the scanning computer, the positioning control, and the motion control for each scanning mode. Therefore, the specification of the parameter description is separately determined. Represents from the host to the motion control computer, and returns from the motion control computer to the host.
Axis marks: 1 is vertical motion, 2 is rotational motion, 3 is horizontal motion, and 4 is step motion.
Is the line sweep DR. For example, motion control reception for each scan mode: "mode flag - motion distance mm (angle) speed (mm / s) measurement step trigger mode rotation angle J rotation speed rotation step angle 15 / 6360 return: Successful execution of the motion "0'2 open motion control system has been developed since the late 1980s when the United States proposed the concept of an open CNC system. The open CNC system has experienced more than 20 years of development. There are many research plans in the country from the research results of open CNC systems, due to a series of problems such as real-time operating system, standard uniformity and system stability, "PC + motion controller" is TCP / IP protocol and network communication applications The relationship is currently a realistic and effective way to implement an open CNC system. It is made up of an open architecture 'motion control card + PC'. This motion control card uses high-speed DSP as the CPU. It has strong motion control and PLC control capability. It is a CNC system and can be used alone. For example, DeltaTau uses the PMAC-NC control system constructed with the PMAC control card. At present, "PC+ motion controller" belongs to the mainstream system of the application. The non-real-time part is processed by the PC, and the real-time control is carried out by the motion controller inserted into the expansion slot of the PC. The CNC system thus constructed has both the flexibility of the front-end PC and the stability and reliability of the original dedicated CNC system.
Select the servo motor and the drive to calculate the required maximum torque and drive power according to the static and dynamic load conditions of the equipment.
Each axis motor, drive and reducer is selected taking into account the safety factor and installation space.
Determine the type of motion controller you need.
Determine position detection, feedback mode, and choose whether to use photoelectric encoder or scale.
Determine the number of input and output switches and how they operate.
Connect the motion controller, driver, motor and equipment according to the terminal arrangement description and the driver control signal wiring instructions, and properly connect the control signal line and the encoder feedback signal line between the controller and the driver.
Connect the switch, indicator light and all the travel switch, proximity switch, stepper motor driver output of the operation panel to the universal digital I/O terminal of the motion controller terminal.
Apply the dynamic response test function in the debugging environment program to test and analyze the dynamic response characteristics of each axis of the device and select reasonable control parameters.
Design flow chart of each axis work process control. According to the application software development language selected by the user, such as C++, select the corresponding dynamic link library DLL of the appropriate operating system environment, and master the calling method of the motion controller command function. Write a device-controlled application.
3 network communication to truly achieve remote control based on the Internet, not only must consider the characteristics of the original network technology and control technology, but also consider the new features of the existing system. For example, the reliability and accuracy of data transmission, the accuracy of data communication is the primary requirement of remote control systems, and it is impossible to control without reliable data. The system adopts the TCP (TransftrContiolPiotocol)/IP (Internet Protocol) protocol and the compatibility of the fieldbus protocol to truly achieve unimpeded data. The following mainly discusses the network communication mechanism.
TCP/IP is a widely used protocol on the Internet that can be used to interconnect heterogeneous machines. The TCP/IP protocol itself is very complicated. However, in network programming, the programmer does not have to consider the implementation details of TCP/IP, and only needs to use the protocol network programming interface Socket (also known as socket). The Sockets API communicates directly with the TCP/IP core. Together with network physical media (such as network cards), the TCP/IP core protocol provides facilities for communication between network applications. The relationship is as shown.
The Socket was originally a network communication interface developed by the University of California at Berkeley for the UNIX operating system and is one of the most popular network communication application interfaces. There are many such hosts on the Internet that run multiple service software and provide several services. Each service opens a Socket and binds to a port. Socket is like a porous socket, as it was originally intended. A host is like a room full of sockets, each with a number, some sockets provide 220 volts AC, some provide 110 volts AC, and some offer cable TV programs. The client software plugs the plug into a different number of outlets to get different services.
In the application of the /IP network protocol, the main mode of interaction between Windows Sockets network communication programs on each network node computer is the client/server mode. That is, the client sends a service request to the server, and after receiving the request, the server provides the corresponding service.
3.2 WindowsSockets communication program works The communication principle of ets is: the server and the client must establish a communication socket, and the server should enter the listening state first, then the client socket sends a connection request, and the client receives the connection request. After the request, another socket is established to communicate, and the socket that was originally responsible for monitoring is still listening. If another client sends a connection request, a socket is created.
It is a process block diagram of using Sockd for communication connection. It can be seen that the relationship between the client and the server is asymmetric. The server starts up first, then starts the client to establish a connection with the server at some point. Both the server and the client must start by calling socket() to create a socket socket, then the server calls bind() to bundle the socket with a local network address, and then calls listen() to make the socket in a passive state. Ready to receive state, while specifying its request queue length, the server can then call ac (ept () to receive the client connection. After the client opens the socket, you can establish a connection with the server by calling connect(). After the connection is established, The client and the server can send and receive data over the connection. After the data transfer ends, both parties call cl) sesockel() to close the socket. The above process is implemented by VC6.
4 Precision motion controller application development Further development of the PC-based machine tool motion control system can realize many functions that cannot be realized by the interactive interface provided by the developer, such as the 1' user interface' and 'I/0' implemented by the system. The machine control 'function' can be precisely embedded motion control function embedded in the CT application system.
Kollmorgen provides two ways to develop, simple to call the Task program directly, the sample program is as follows: create a MC motion controller device handle can also directly set or extract system variables, generate motion control commands, and determine the state of motion Do the corresponding control: extract the system variable while(valueL!=2)// to judge the motion state, whether the motion is stable and stable, send the pulse to the OUT port. 5 Conclusion This paper mainly introduces the technical route adopted by the industrial CT precision motion control. And several key technical issues, including the construction of open motion control systems, network communication of control commands, and development techniques for motion controllers. The constructed system has been developed and is operating normally to meet the technical requirements of CT scanning. All the programs were developed by VC6, and the results were verified by practice and the work was stable.
Zhang Chaozong, Guo Zhiping, Lu Junzhen. Overview of the progress of industrial CT research. Http://裴葆é’, æ¨è´ºæ¥,陈五一. Research and application of open motion control system based on network. Manufacturing Automation, 2003, 25 (2): 1~3 Liu Li. Industrial CT scanning dynamics analysis and motion control research. Beijing University of Aeronautics and Astronautics, 2002 Department of Dynamic Control Lecturer.
(Editor Li Xiumin) (Continued from page 61) The composition of the user interface; the tool selection module consists of the tool library and tool parameters; the cutting amount recommendation module consists of the cutting amount inference engine and the knowledge base, and the cutting depth and cutting are inferred based on the process information. Speed ​​and feed rate; the cutting amount optimization module consists of a common coefficient table, index table and optimization module. It is automatically based on constraints such as cutting amount, tool, machine tool and machining accuracy, and user-interacted optimization model. The preliminary optimized cutting amount is calculated, and then the optimal combination of cutting amount is optimized according to the linear programming method. The neural network is used for multi-objective optimization in the optimization process, and the optimization result is finally obtained.
2.3 Post processing module The purpose is to form a CNC machining file. Due to the different CNC systems used in various machine tools, the CNC machining programs used have different instruction codes and formats.
In order to solve this problem, the pre-edited file is post-processed, so that the NC processing file that meets the requirements of the CNC machining format can be output.
The module consists of five parts, and its structural block diagram is as shown. The block diagram of the post-processing module of the input control module is used to input the tool position data and auxiliary function information calculated in the pre-processing stage and stored in the data files CLD and WRK into the post-processing program. Then judge, control, and call other modules; the role of the motion module is to process the motion record type code, which is formed by the motion definition statement in the NC source program; the function of the auxiliary function module mainly judges and processes the auxiliary function code and F, S, The T command; the output module converts the post-processing operation result into the NC code format required by the specific machine tool, and outputs it to the graph, and performs a graphical simulation check of the machining process before processing to ensure the accuracy of the NC program. The CNC machining simulation module uses OpenGL as a development tool to simulate the whole process of CNC machining. Through the dynamic simulation of the machining process, it can be checked whether the tool position calculation is correct, whether the machining process has been cut, whether the selected tool, the path of the tool, the advance and retraction mode are reasonable, whether the tool path is correct, whether the knife and the constraint surface interfere with each other. collision. The main simulation process of NC machining is as follows: (1) Translating the NC code into the motion data of the tool, and translating the code of the code in the code into the motion data of the tool, and checking the syntax errors in the code; 2 Blanks and parts Graphic input and display; 3 tool definition and graphic display; 4 dynamic display of tool movement track; check interference between tool and profile of cut workpiece, motion collision between tool, fixture, machine tool and workpiece, including specific interference position And the amount of interference. The simulation processing module uses VC6.0 and OpenGL as development tools to realize the 3D dynamic simulation test of NC code.
3 Conclusion Based on the CAD/CAM system of graphic automatic programming technology, it can realize the plane design of simple parts, the automatic generation of NC code and the simulation processing of code. This system uses VC visual programming tools, which is easy to integrate CAD/CAM. Using this system can make great advantages in product design and innovation, product manufacturing and so on.
Liu Rongzhong. Sihong. Research and development of graphical automatic programming systems. Sichuan Dasheng is set high. Introduction to modern manufacturing technology. Beijing: Mechanical Industry Press, NC program files.
2.4 Simulation Processing Module (Editor Jiang Fu) Applying computer simulation technology to CNC machining, instead of or reducing the actual Hong Kong Institute lecturer's trial cutting work, is the most economical and effective way to solve CNC machining problems. Simply
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