application solution
Using NI's LabVIEW image control toolkit and IMAQ visualization software, we develop a test kit for building blocks that use laptop computers as the main body, insert the corresponding DAQ data acquisition card, and integrate with various sensors in a variety of forms. Test the system .
Introduction
For a long time, the national compulsory verification project for the safety testing line of the automotive industry has used engineering vehicles as a means of delivery and carried a large number of various special testing instruments for automobiles to meet the measurement verification of different parameters of the first-line instruments produced by the automobile manufacturing industry.
The newly developed virtual instrument verification and test system is designed using National Instruments' LabVIEW virtual instrument software package, which has the characteristics of simple pages and easy operation. The hardware also uses the company's multi-functional data acquisition card, which has a high degree of integration , Superior performance, good stability and other advantages, the sensors use products of famous brands from various countries (such as: the force sensor uses the US METTLER TOLEDO company product, the photoelectric sensor uses the German DATRON company product, the displacement sensor uses the German HBM company product, the accuracy of each sensor is controlled at 0.3 ‰), so that the system is excellent, and the credibility of data processing is slightly higher than similar products.
LabVIEW software programming
(1) Efficient and fast design
The "Search Example" and "SoluTIon Wizard" columns in the LabVIEW Picture Control Toolkit of NaTIonal Instruments provide users with a thoughtful programming idea, and at the same time, it is a convenient and quick to use In this way, many examples are reversed, and on this basis, a slight change can easily become the material required by the user, so you can get twice the result with half the effort. For example, in the “Frequency Measurement†custom data acquisition solution wizard, add the “Wheel Diameter Input†function and frequency / vehicle speed conversion formula, and connect the German DATRON to the CLKB1 port of the data acquisition card The company's photoelectric sensor products are pasted with reflective paper on the side of the wheel under test to measure the rotation speed of the wheel, and can be made into an instrument for measuring the instantaneous speed of the car. With some appropriate changes, it can be adapted into a highly sophisticated vehicle speed verification test system.
When creating a virtual instrument block diagram program, you can also directly access the ready-made VI subroutine that is closer to the user in the "Open VI" (open virtual instrument), find "Examples" (example) "AcTIvity" (control) and other columns, On this basis, make appropriate changes. In this way, mature block diagram programs can be referenced immediately, less detours in the programming process, and speed up the entire development cycle. For example, the test system of automobile brake pedal force and hand brake pulling force test, using the "Single-Point Strain Gauge Measurement" example, and make some appropriate adaptations, select the US METTLER TOLEDO force sensor products, you can Transformed into a highly sophisticated automotive braking force verification test system.
Compared with the development of single-chip microcomputer, the hardware workload of the virtual instrument is significantly reduced, a large number of electronic components can be saved, the difficulty of printed circuit board design is simplified, the instrument used in the installation and debugging process is greatly reduced, and the entire development cycle is shortened by many times . In addition, the instrument has great plasticity. It can increase or decrease the function according to the actual situation anytime, anywhere, and improve the design scheme. Its superiority is incomparable. The instrument developed by the single-chip microcomputer has been used for several years. The original design function cannot be adapted because of new requirements from users. The changing environment is eliminated; after several years of application of virtual instruments, the accumulated functions can be continuously improved at any time and any place, so the more complete the use and the closer to the user; especially when the single-chip microcomputer develops a single special instrument, the development of special new products The perceptual knowledge accumulated by the designer was limited to a certain range at the time, from design to instrumentation, and was limited to a certain extent by time span and expenditure. Its reliability and stability often caused congenital deficiencies, which were also difficult to make up afterwards. solve. The hardware and software of virtual instruments are the wisdom of a set of institutions and a group year after year, and are the products of batches. Their maturity, reliability and stability are beyond doubt. Moreover, if there is any dissatisfaction in the software, it will be easy to make up for it afterwards. It is also a zero programming design, modular integration, intuitive, even non-computer professional counterparts can be easily modified through simple training. The advantages of this application solution in reducing development time and reducing costs seem that the superiority of applying LabVIEW is accurate.
(2) Intelligent design
The intelligent data processing of traditional instruments is almost impossible, and the virtual instrument analyzes the collected data through the built-in powerful signal processing software, which is extremely intuitive. The software package is easy to be finished in Chinese, and can be easily connected with Word word processing and Excel spreadsheets in Office. It can carry out scientific calculations and word processing according to the designer's ideas at will, and store and print out standardized test and verification reports. The layout format can also be improved in time as needed.
The effect of the penetration of virtual instruments from practicality to interest is also obvious. The application of picture and sound functions makes the virtual instrument verification system not only meet the conventional measurement performance index design requirements, but also meet the measurement verification timing, humanized and friendly Platform interface. For this reason, it can be linked with graphic files, so that various chart files can be output in a graphic manner. The pictures can also be made into cartoons, and then dubbed according to the use scene to give play to the charm of the voices of men, women, old and young, making colorful and lively pictures to set off conventional notices, fault alarms, etc., so as to make it more It has a kind and friendly humanity, making users feel that it is not only a testing instrument, but also a fun "partner". When problems are encountered during the testing and verification process, enthusiastic prompts are added according to the scene, which will make you suddenly realize and be inspired; the page alarm display is clear at a glance, making you think and have no time to sigh; when the test is completed, the innocent and lively cartoon The pictures and the eloquent language make you enter into a real and relaxed situation. But even so, users will feel tired and tired after a long time of use. Fortunately, the capacity of computer hard disks is developing rapidly, and there is no need to worry about the lack of hard disk capacity. For this reason, colorful and trendy pictures, cartoons and voices are produced for users of different levels to choose and output in random ordering, thereby avoiding monotonous depreciation Sense of smell.
The file input and output functions are ingeniously applied, which provides convenience for users to learn to use the virtual instrument. You can check the relevant performance indicators, concise usage methods and technical services from the help bar.
In short, try to avoid leaving the various types of functions of NI products, and make full use of the potential to make perfect instruments.
(3) Flexible and changeable input and output design
The use of virtual instruments is extremely wide, the types of sensors are endless, the shape of the coupling parts is varied, and most of them are original standard parts, which can be connected to the conventional instruments of related series products. This shape of the connector is also unrealistic. If a variety of sockets are made on an interface board for compatibility, I am afraid that it is necessary to design a "mass" interface board that is several times larger than the size of the virtual instrument in order to cope with it.
To this end, we use two schemes to make up for the above defects:
1. The most commonly used typical socket is configured on the virtual instrument, designed on multiple printed circuit boards, so as to avoid the messy connection between the traditional process and the instrument chassis, and directly inserted into the input and output card slots, and Can be freely combined according to different needs.
2. If the sensor cannot be directly connected to any interface board of the virtual instrument, use a special connection plug cable to transition between the instrument and the sensor. Therefore, the connection between sensor and virtual instrument is solved. The virtual instrument has handily constructed the measurement scheme defined by the user, and truly turned the thought into reality.
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