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1、精选优质文档-倾情为你奉上Building Programmable Automation Controllers with LabVIEW FPGAOverviewProgrammable Automation Controllers (PACs) are gaining acceptance within the industrial control market as the ideal solution for applications that require highly integrated analog and digital I/O, floating-point proce

2、ssing, and seamless connectivity to multiple processing nodes. National Instruments offers a variety of PAC solutions powered by one common software development environment, NI LabVIEW. With LabVIEW, you can build custom I/O interfaces for industrial applications using add-on software, such as the N

3、I Module.With the LabVIEW FPGA Module and reconfigurable I/O (RIO) hardware, National Instruments delivers an intuitive, accessible solution for incorporating the flexibility and customizability of FPGA technology into industrial PAC systems. You can define the logic embedded in FPGA chips across th

4、e family of RIO hardware targets without knowing low-level hardware description languages (HDLs) or board-level hardware design details, as well as quickly define hardware for ultrahigh-speed control, customized timing and synchronization, low-level signal processing, and custom I/O with analog, dig

5、ital, and counters within a single device. You also can integrate your custom NI RIO hardware with image acquisition and analysis, motion control, and industrial protocols, such as CAN and RS232, to rapidly prototype and implement a complete PAC system.Table of Contents1. 2. 3. 4. 5. 6. 7. Introduct

6、ion You can use graphical programming in LabVIEW and the Module to configure the FPGA (field-programmable gate array) on NI RIO devices. RIO technology, the merging of LabVIEW graphical programming with FPGAs on NI RIO hardware, provides a flexible platform for creating sophisticated measurement and

7、 control systems that you could previously create only with custom-designed hardware.An FPGA is a chip that consists of many unconfigured logic gates. Unlike the fixed, vendor-defined functionality of an ASIC (application-specific integrated circuit) chip, you can configure and reconfigure the logic

8、 on FPGAs for your specific application. FPGAs are used in applications where either the cost of developing and fabricating an ASIC is prohibitive, or the hardware must be reconfigured after being placed into service. The flexible, software-programmable architecture of FPGAs offer benefits such as h

9、igh-performance execution of custom algorithms, precise timing and synchronization, rapid decision making, and simultaneous execution of parallel tasks. Today, FPGAs appear in such devices as instruments, consumer electronics, automobiles, aircraft, copy machines, and application-specific computer h

10、ardware. While FPGAs are often used in industrial control products, FPGA functionality has not previously been made accessible to industrial control engineers. Defining FPGAs has historically required expertise using HDL programming or complex design tools used more by hardware design engineers than

11、 by control engineers.With the LabVIEW FPGA Module and NI RIO hardware, you now can use LabVIEW, a high-level graphical development environment designed specifically for measurement and control applications, to create PACs that have the customization, flexibility, and high-performance of FPGAs. Beca

12、use the LabVIEW FPGA Module configures custom circuitry in hardware, your system can process and generate synchronized analog and digital signals rapidly and deterministically. Figure 1 illustrates many of the NI RIO devices that you can configure using the LabVIEW FPGA Module.Figure 1. VI Block Dia

13、gram and RIO Hardware Platforms NI RIO Hardware for PACs Historically, programming FPGAs has been limited to engineers who have in-depth knowledge of VHDL or other low-level design tools, which require overcoming a very steep learning curve. With the Module, NI has opened FPGA technology to a broade

14、r set of engineers who can now define FPGA logic using LabVIEW graphical development. Measurement and control engineers can focus primarily on their test and control application, where their expertise lies, rather than the low-level semantics of transferring logic into the cells of the chip. The Lab

15、VIEW FPGA Module model works because of the tight integration between the LabVIEW FPGA Module and the commercial off-the-shelf (COTS) hardware architecture of the FPGA and surrounding I/O components.National Instruments PACs provide modular, off-the-shelf platforms for your industrial control applic

16、ations. With the implementation of RIO technology on PCI, PXI, and Compact Vision System platforms and the introduction of RIO-based , engineers now have the benefits of a COTS platform with the high-performance, flexibility, and customization benefits of FPGAs at their disposal to build PACs. Natio

17、nal Instruments PCI and PXI R Series plug-in devices provide analog and digital data acquisition and control for high-performance, user-configurable timing and synchronization, as well as onboard decision making on a single device. Using these off-the-shelf devices, you can extend your NI PXI or PCI

18、 industrial control system to include high-speed discrete and analog control, custom sensor interfaces, and precise timing and control. NI CompactRIO, a platform centered on RIO technology, provides a small, industrially rugged, modular PAC platform that gives you high-performance I/O and unpreceden

19、ted flexibility in system timing. You can use NI CompactRIO to build an embedded system for applications such as in-vehicle data acquisition, mobile NVH testing, and embedded machine control systems. The rugged NI CompactRIO system is industrially rated and certified, and it is designed for greater

20、than 50 g of shock at a temperature range of -40 to 70 C.NI Compact Vision System is a rugged machine vision package that withstands the harsh environments common in robotics, automated test, and industrial inspection systems. NI CVS-145x devices offer unprecedented I/O capabilities and network conn

21、ectivity for distributed machine vision applications.NI CVS-145x systems use IEEE 1394 (FireWire) technology, compatible with more than 40 cameras with a wide range of functionality, performance, and price. NI CVS-1455 and NI CVS-1456 devices contain configurable FPGAs so you can implement custom co

22、unters, timing, or motor control in your machine vision application.Building PACs with LabVIEW and the LabVIEW FPGA ModuleWith LabVIEW and the Module, you add significant flexibility and customization to your industrial control hardware. Because many PACs are already programmed using LabVIEW, progra

23、mming FPGAs with LabVIEW is easy because it uses the same LabVIEW development environment. When you target the FPGA on an NI RIO device, LabVIEW displays only the functions that can be implemented in the FPGA, further easing the use of LabVIEW to program FPGAs. The LabVIEW FPGA Module Functions pale

24、tte includes typical LabVIEW structures and functions, such as While Loops, For Loops, Case Structures, and Sequence Structures as well as a dedicated set of LabVIEW FPGA-specific functions for math, signal generation and analysis, linear and nonlinear control, comparison logic, array and cluster ma

25、nipulation, occurrences, analog and digital I/O, and timing. You can use a combination of these functions to define logic and embed intelligence onto your NI RIO device.Figure 2 shows an FPGA application that implements a PID control algorithm on the NI RIO hardware and a host application on a Windo

26、ws machine or an RT target that communicates with the NI RIO hardware. This application reads from analog input 0 (AI0), performs the PID calculation, and outputs the resulting data on analog output 0 (AO0). While the FPGA clock runs at 40 MHz the loop in this example runs much slower because each c

27、omponent takes longer than one-clock cycle to execute. Analog control loops can run on an FPGA at a rate of about 200 kHz. You can specify the clock rate at compile time. This example shows only one PID loop; however, creating additional functionality on the NI RIO device is merely a matter of addin

28、g another While Loop. Unlike traditional PC processors, FPGAs are parallel processors. Adding additional loops to your application does not affect the performance of your PID loop.Figure 2. PID Control Using an Embedded VI with Corresponding LabVIEW Host VI. FPGA Development Flow After you create th

29、e VI, you compile the code to run on the NI RIO hardware. Depending on the complexity of your code and the specifications of your development system, compile time for an FPGA VI can range from minutes to several hours. To maximize development productivity, with the R Series RIO devices you can use a

30、 bit-accurate emulation mode so you can verify the logic of your design before initiating the compile process. When you target the FPGA Device Emulator, LabVIEW accesses I/O from the device and executes the VI logic on the Windows development computer. In this mode, you can use the same debugging to

31、ols available in LabVIEW for Windows, such as execution highlighting, probes, and breakpoints.Once the LabVIEW FPGA code is compiled, you create a LabVIEW host VI to integrate your NI RIO hardware into the rest of your PAC system. Figure 3 illustrates the development process for creating an FPGA app

32、lication. The host VI uses controls and indicators on the FPGA VI front panel to transfer data between the FPGA on the RIO device and the host processing engine. These front panel objects are represented as data registers within the FPGA. The host computer can be either a PC or PXI controller runnin

33、g Windows or a PC, PXI controller, Compact Vision System, or controller running a real-time operating system (RTOS). In the above example, we exchange the set point, PID gains, loop rate, AI0, and AO0 data with the LabVIEW host VI.Figure 3. Development FlowThe NI RIO device driver includes a set of

34、functions to develop a communication interface to the FPGA. The first step in building a host VI is to open a reference to the FPGA VI and RIO device. The Open FPGA VI Reference function, as seen in Figure 2, also downloads and runs the compiled FPGA code during execution. After opening the referenc

35、e, you read and write to the control and indicator registers on the FPGA using the Read/Write Control function. Once you wire the FPGA reference into this function, you can simply select which controls and indicators you want to read and write to. You can enclose the FPGA Read/Write function within

36、a While Loop to continuously read and write to the FPGA. Finally, the last function within the LabVIEW host VI in Figure 2 is the Close FPGA VI Reference function. The Close FPGA VI Reference function stops the FPGA VI and closes the reference to the device. Now you can download other compiled FPGA

37、VIs to the device to change or modify its functionality.The LabVIEW host VI can also be used to perform floating-point calculations, data logging, networking, and any calculations that do not fit within the FPGA fabric. For added determinism and reliability, you can run your host application on an R

38、TOS with the LabVIEW Real-Time Module. LabVIEW Real-Time systems provide deterministic processing engines for functions performed synchronously or asynchronously to the FPGA. For example, floating-point arithmetic, including FFTs, PID calculations, and custom control algorithms, are often performed

39、in the LabVIEW Real-Time environment. Relevant data can be stored on a LabVIEW Real-Time system or transferred to a Windows host computer for off-line analysis, data logging, or user interface displays. The architecture for this configuration is shown in Figure 4. Each NI PAC platform that offers RI

40、O hardware can run LabVIEW Real-Time VIs. Figure 4. Complete PAC Architecture Using , LabVIEW Real-Time and Host PCWithin each R Series and device, there is flash memory available to store a compiled LabVIEW FPGA VI and run the application immediately upon power up of the device. In this configurati

41、on, as long as the FPGA has power, it runs the FPGA VI, even if the host computer crashes or is powered down. This is ideal for programming safety power down and power up sequences when unexpected events occur.Using NI SoftMotion to Create Custom Motion Controllers The NI SoftMotion Development Modu

42、le for LabVIEW provides VIs and functions to help you build custom motion controllers as part of NI PAC hardware platforms that can include NI RIO devices, DAQ devices, and Compact FieldPoint. NI SoftMotion provides all of the functions that typically reside on a motion controller DSP. With it, you

43、can handle path planning, trajectory generation, and position and velocity loop control in the NI LabVIEW environment and then deploy the code on LabVIEW Real-Time or -based target hardware.NI SoftMotion includes functions for trajectory generator and spline engine and examples with complete source

44、code for supervisory control, position, and velocity control loop using the PID algorithm. Supervisory control and the trajectory generator run on a LabVIEW Real-Time target and run at millisecond loop rates. The spline engine and the control loop can run either on a LabVIEW Real-Time target at mill

45、isecond loop rates or on a LabVIEW FPGA target at microsecond loop rates.Applications Because the Module can configure low-level hardware design of FPGAs and use the FPGAs within in a modular system, it is ideal for industrial control applications requiring custom hardware. These custom applications

46、 can include a custom mix of analog, digital, and counter/timer I/O, analog control up to 125 kHz, digital control up to 20 MHz, and interfacing to custom digital protocols for the following: Batch control Discrete control Motion control In-vehicle data acquisition Machine condition monitoring Rapid

47、 control prototyping (RCP) Industrial control and acquisition Distributed data acquisition and control Mobile/portable noise, vibration, and harshness (NVH) analysisConclusion The Module brings the flexibility, performance, and customization of FPGAs to PAC platforms. Using NI RIO devices and LabVIE

48、W graphical programming, you can build flexible and custom hardware using the COTS hardware often required in industrial control applications. Because you are using LabVIEW, a programming language already used in many industrial control applications, to define your NI RIO hardware, there is no need

49、to learn VHDL or other low-level hardware design tools to create custom hardware. Using the LabVIEW FPGA Module and NI RIO hardware as part of your NI PAC adds significant flexibility and functionality for applications requiring ultrahigh-speed control, interfaces to custom digital protocols, or a custom I/O mix of analog, digital, and counters. FPGA（现场可编程门阵列）模块开发可编程自动化控制器综述 工业控制上的应用要求高度集成的模拟和数字输入输出、浮点运算和多重处理