The most popular open software CNC system with hig

2022-07-26
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A high-performance, open software CNC system and its application

the first CNC machine tool was born in 1952. The development of CNC machine tools has experienced two stages: digital control (NC) and computer digital control (CNC). From the first generation of electronic tubes, the CNC system has gone through the use of transistors, small-scale integrated circuits and small computer technology to the special NC stage of microprocessors around 1974. In the early 1990s, the CNC system entered the stage based on PC. PC based numerical control systems (CNC) are divided into the following types:

(1) PC embedded in NC type

PC technology is simply embedded in the traditional special NC. NC can share some computer software and hardware resources, while computers only participate in auxiliary programming, analysis, monitoring, production management and process preparation. Because the NC part of this CNC system is still a special structure, users cannot enter the core of the CNC system, so it belongs to a preliminary open CNC system

(2) NC embedded PC type

this is a numerical control system that completely uses PC as the hardware platform. The motion control (including axis control and machine tool logic control) function is completed by an independent motion controller equipped with a special control chip. It is usually realized by hardware in the form of PC plug-in (conforming to isa or PCI bus standard) or by an embedded system connected through the network. The motion control software is designed by the NC manufacturer. The user has bundled the Utilization Oriented top-level research in the UK and cannot modify it. Only the upper software of NC (NC language interpreter/man-machine interface, etc.) is based on PC operating system (such as windows), so this NC system is only open at the upper computer level

(3) full software type

this is a numerical control system completely controlled by PC software. It realizes the motion controller in the form of application software. This is a numerical control system with the latest open architecture, which can provide users with the greatest choice and flexibility. It has become the mainstream of the new generation of CNC

as we all know, the most commonly used Windows desktop operating system is a 32-bit operating system with multithreading and preemptive multitasking, which has poor real-time performance. And real-time control is the key of CNC system, which determines the processing speed and precision of CNC machine tools. Therefore, some CNC systems use the original DOS operating system as the software platform, which can meet the general real-time requirements. However, the 16 bit single task DOS operating system running in real mode does not give full play to the advantages of 32-bit PC, and the application program is limited by 640K memory and can operate directly on the hardware, so the system reliability is difficult to guarantee. At present, the real-time operating system (or software) based on windows in the market, such as windowsce Net is more expensive, which is not conducive to the popularity in the NC machine tool industry. The hi-800 series PC based CNC system developed by Hong Kong hydemun CNC Technology Co., Ltd. introduced in this paper introduces the real-time control kernel of German power automation (hereinafter referred to as PA), which makes up for the poor real-time performance of Windows desktop operating system. It is a real full software open CNC system, which can be widely used in the complex control of various CNC machine tools, machining centers and some special-purpose machine tools

hi-800 CNC system composition

hi-800 series CNC system is a high-performance CNC manufactured by PC technology according to industrial standards. The system adopts Windows NT operating system and PA real time kernel, so that the user can have a window type man-machine interface that is easy to operate. At the same time, it is possible to use the hard disk as the NC memory. And it can be applied from simple serial port to complex communication network

hi-800 CNC system hardware design

since the motion control and logic control functions are realized by software, the hi-800 series CNC system hardware is composed of only controller, keyboard and display, NC operation panel and corresponding extended version card. Its outline structure is shown in Figure 1

Figure 1 outline structure diagram of hi-800 series CNC system

the main controller is an industrial standard PC installed with Micrsoft Windows NT operating system. It can connect the devices required by the system through the standard slots and buses on the PC motherboard, such as axis control card, digital or analog input/output (i/o) interface, communication card, etc. The hi-800 system is equipped with a control card that can control 4 analog axes and 1 spindle through PCI bus; 16 digital input and output channels and 5 analog output channels. Users can also control more axes and i/o through multi axis expansion boards or i/o expansion modules as required. A typical external device connected to the hi-800 main controller is shown in Figure 2

Figure 2 CNC controller external device interface

hi-800 series operating system is also configured with an Ethernet card (tcp/ip protocol); 4 serial communication interfaces to build a chemical fiber efficient flexible manufacturing technology innovation platform (one of which can be configured as RS-485 interface); One parallel communication interface and one USB communication interface can flexibly realize networking control. There is also a sound card that can realize dual channel stereo control and a display card that can connect TFT and CRT at the same time. Users can also select other hardware configurations as required

the system adopts 10.4 ″ ultra-thin LCD and thin-film keys, which is more suitable for industrial field applications. It can monitor and realize various operations professionally and conveniently in its visual interface, such as curve graph of machining process and various information of machined parts; PLC program written according to user's needs, monitoring PLC and CNC signals and program modification; Some important operation information such as machine coordinates and program coordinates can be observed during machining

The

nc operation panel can be used to control the start and stop operations of the system and programs. It can also be used to realize the manual control of control objects (such as machine tools), such as the manual feeding of X, y and Z axes; Forward and reverse rotation control of spindle; Lubrication and cooling system control are convenient for machine tool commissioning

system software structure

the software structure of hi-800 CNC system is shown in Figure 3. As the NT real-time kernel of PA is embedded in the system, the motion control tasks and logic control tasks with high real-time requirements are completed by CNC software and software PLC, and directly control the relevant hardware equipment, which can also meet the requirements of real-time control of CNC system. Other tasks that do not require high real-time performance, such as human-computer interface (HMI), computer-aided manufacturing (CAM) and other tasks that need to be realized by PC, are still realized by Windows NT operating system

Figure 3 software structure of hi-800 series CNC system

pa NT real-time kernel enables the CNC system to execute real-time tasks at fixed time intervals, and when executing real-time tasks, it prohibits the execution of other non real-time tasks, and can directly obtain system related hardware resources. Only when there are no real-time tasks to be executed can Windows NT obtain CPU resources to execute applications based on NT system

the system CNC software includes all functions related to motion control, such as compiling and interpreting the user's NC program; Interpolation operation of motion track; Position ring control of the shaft and communication with software PLC and external equipment

cnc compiler

the main task of the CNC compiler is to interpret the user's NC program and convert it into a format that can be recognized by the interpolator in the servo task. In addition, the compiler has the following 3 Fixture selection will also affect the measurement function of the pressure testing machine:

control the CNC operation mode

system diagnosis

exchange information with servo system

transmit information to MMI for display

binary i/o data exchange with PLC

offset setting and path correction during machining

cnc interpolator

interpolator is the executive unit of CNC. The following functions of CNC are related to interpolation tasks:

path interpolation

axis interpolation, including linear, spline, arc and helix interpolation, with mirror and parallel follow-up axis functions

position axis control

diagnosis and monitoring management

communication connection with location task

read input signal from CNC-PLC

transmit BCD code signal to PLC

real time conversion (polar coordinates, 5 axes)

real time self correction, including clearance compensation, backlash error compensation, zero drift compensation, etc

sinusoidal oscillator

spindle output

read the new program segment from the FIFO register

quickly output digital signals

cnc position loop

position task is used to realize the position control function of the axis. All real-time tasks of CNC and PLC are controlled by hardware timing interrupts related to the control axis. Each interrupt executes the position task, mainly to complete the following operations:

read the position value from the gate array or SERCOS interface

detect encoder signal (analog axis)

update the machine position

computer bed position error value

calculate the corresponding internal position according to the position of the machine tool

calculate the deviation between the command position value and the actual mechanical position

calculate the output value of the corresponding position control

output to d/a converter (analog control axis)

output to SERCOS interface (SERCOS control axis)

hi-800's built-in high-speed soft PLC conforms to IEC standards. Users can use ladder diagram, function program segment, instruction table, flow chart, structural text and other PLC languages to complete various complex logic control of machine tools. The system also has built-in machine tool parameter controller and logic analyzer (a very useful debugging tool), which makes the installation, debugging and maintenance of the machine tool control system very simple

as a PC based Open CNC system, hi800 allows users to integrate third-party professional technology and special software (such as various CAM software) in a safe and reliable manner. The system control functions are realized by software, and the corresponding function modules can be opened according to the type of machine tool and different applications, providing users with the greatest choice and flexibility

hi-800 series CNC system performance and characteristics

the main performance indicators of the system are shown in the attached table: the main performance indicators of the attached table system

hi-800 system has the following characteristics because of its unique software and hardware structure:

openness

hi-800 system makes full use of the openness of Windows NT operating system, allowing the integration of CNC and other application software on the same system. In addition, a series of open software tools are provided. For example, compile cycles allows users to customize their own special processing functions to realize the control of various complex machine tools; The visual interface enables users to customize the special man-machine interface based on the original MMI; The VMI function of virtual human-machine interface can customize a new human-machine interface according to user needs

high speed

hi-800's "adaptive read ahead function" can preprocess hundreds of NC program segments in real time, and can automatically adjust the acceleration and deceleration control according to the corresponding feed rate. The speed change curve of the adaptive read ahead function is shown in Figure 4. The abscissa in the figure is the NC program segment, and the ordinate f represents the execution speed. G08 represented by the blue curve has no read ahead function, so each program segment must perform acceleration and deceleration operations; The speed of G09 indicated by the red curve changes continuously, which not only enhances the efficiency of the machine tool, but also improves the surface finish of the machined workpiece

Figure 4 Comparison of speed change curve of adaptive pre reading function "curvature optimization function" of

system

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