Upgrading the Data Acquisition System for a Climatic Wind Tunnel Using CompactRIO and LabVIEW

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"Using the flexible, adaptable, and modular architecture of CompactRIO, we can customize the test to meet each customer’s needs."


The Challenge:
Replacing our data acquisition system with a wind tunnel for greater test flexibility.

The Solution:
Creating a system based on distributed measurement modules that each integrate an NI CompactRIO system with data centralization in the supervisor PC using standard VASCO software integrated with NI LabVIEW software.


The Wind Tunnel Climate Île de France offers an environment to help customers, primarily in the automotive sector, test vehicle characteristics such as cooling, heating, and ventilation.

The company contracted us to upgrade its system by increasing the number of measurement channels and their frequency of acquisition, integrating digital channels, and updating software and hardware.

4 Measurement Module Suitcases for Maximum Flexibility

The tests may require a highly variable number of channels. We needed adaptable acquisition hardware and a fixed-position distributed data acquisition system in the supervision room, along with four independent mobile systems for vehicles.

Because the customer frequently moves the systems, we integrated them into industrial sealed suitcases for easy storage, for example, in the trunk of the vehicle. Depending on the number of channels required to test, it is possible to use one to four suitcases to instrument the vehicles.

We wired the terminal blocks of the acquisition modules to connectors inside the suitcases. The cable strands connect to the bags and to the other end of the thermocouple sensors, the output voltage of the apparatus, or the diagnostic socket of the vehicle for the digital communication.

We chose CompactRIO for its autonomy and installed a CompactRIO chassis in a bay of the supervision room and in each of the four suitcases.

Voltage, Temperature, and Numerical Measurements

From the bay, the CompactRIO chassis manages 64 voltage inputs. Each case acquires signals from 16 voltage channels and 64 channels via type K thermocouples. In addition, we equipped two of the four cases with modules to retrieve the information circulating on the bus of the vehicle, according to the standard protocol OBD-II (92 channels) or via DBC file type (up to 250 channels). The supervision PC also retrieves via a DLL around 20 data points from another device. In addition, depending on the test performed, it may be necessary to define calculation by power, speed, or performance, for example. The CompactRIO architecture can simultaneously acquire up to 750 channels in test.

The voltage acquired is carried out at 100 Hz, and the temperature and DLL acquisitions to 2 Hz digital channels are acquired at 2 Hz, but the frequency of communication on the CAN bus speed is 500 kHz.

The input voltage range is 0 V to 300 V (provided for electric vehicles). We selected the NI 9206 C Series modules for their accuracy and connected a voltage divider upstream of each channel of each module. The divider bridges are grouped together on a circuit board, and each bridge has a switch to activate the deck for greater system flexibility with respect to the input signals. For signals at 300 V, an additional voltage divider connects to the outside of the suitcase.

Multiple PCs: Configuration, Supervision, Monitoring, and Postprocessing

We used LabVIEW to integrate the VASCO suite with the system. We usually configure a test in the workshop during the preparation and instrumentation of the vehicle. However, with this system, configuration is accessible to any PC on the network running VASCO.

Users administer the test with the fixed-monitoring PC equipped with two screens for ease of use, but they can also use laptops to deliver the test to customers. Customers can track the test in real time from inside the vehicle using laptops.

For the sake of privacy, the customer can access only data on the current trial and information authorized by the supervisor. At the end of the test, a dialog box provides the option to delete the VASCO data recorded during the test.

Regarding the centralized data acquisition, each CompactRIO chassis connects to the bench and writes shared variables read by the program running on the supervision PC. There is no synchronization with the CompactRIO chassis; the system uses the timestamp of the PC. A test is clocked by different sequences composed of arrangements and operating points. We can validate, add, delete, or change data during the test.

Multiple Record Types

When launching a test, the system automatically saves the parameters of the specific equipment, such as customer name and vehicle reference model. The system stores data in several types of files: raw data, data averaged above one second, the operating points (recording a single value averaged by a specific time), and the file that refreshes the data displayed on a secure web page.

During the test, if recording is in progress, users can record the events that they noticed, which are then integrated into the data file result.

After a trial, if calculation channels are modified in the configuration, users can recalculate the routes in question. It is also possible, through an executable, to merge multiple data files.

Fault Management

The number of channels used during a test can be relatively large. The system includes a function to replace defective track data with correct data from another channel. This is useful when, for example, there is a broken wire on the thermocouple, and this value (which is then the upper range of thermocouple measurement and not the actual value) is an input parameter of a calculation.

The state of the connection between the supervision PC and CompactRIO displays in a window that automatically appears during connection loss. If, during the test, a path goes into alarm, the indicator lights inform users. This information is updated in real time so users can quickly react.

Flexible, Adaptable Architecture

Using the flexible, adaptable, and modular architecture of CompactRIO, we can customize the test to meet each customer’s needs.

Author Information:
1480, avenue d’Arménie - Pôle d’Activités Yvon Morandat
13120 Gardanne
Tel: +33 (0)4 42 25 52 02

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