Using NI DIAdem to Develop an Occupant Restraint System

Author(s):
Jeff Blackburn - Takata

Industry:
Automotive

Products:
DIAdem

The Challenge:
Improving dynamic and static testing procedures for vehicle occupant protection systems.

The Solution:
Using National Instruments DIAdem to design a highly accurate testing system that significantly reduces development time and cost.

Takata is a global manufacturer of automotive safety systems, producing a full line of seatbelt systems, airbag modules, electronic sensor units, and steering wheels. With a focus on research and development, our systems meet the highest performance standards and help automakers meet stringent government requirements. Takata’s strength is rooted in the company’s early involvement in airbag development. Initial research began in 1976, and the company started supplying airbags to the global automotive market in 1984. Since that time, investments in textile and inflator technologies have made us one of the few vertically integrated companies supplying today’s market.

We use both static and dynamic testing during occupant protection system development. Typically, several design variations are tested in a development series. Our existing data collection and reporting system generated a report for each individual test, and we manually compiled data from each report using a Microsoft Excel spreadsheet to compare multiple tests. This was a very time-consuming process due to the sheer volume of data (40 to 160 channels for a single test), taking up to several hours depending on the type and number of tests. Furthermore, individual test data was stored in flat files organized by test number in a folder located on a server. If an engineer needed to look back at earlier tests and did not have the actual test number to reference, it was nearly impossible to search the historical records.

In an effort to improve our development process, we implemented a new system based on National Instruments DIAdem 10 that allows us to quickly compare the results of multiple tests, letting us make informed decisions about changes in design, inflator output, and other conditions. The data (forces, accelerations, times, displacements, and pressures) generated during tests are evaluated with respect to industry and governmental injury assessment reference values (IARV) contained in customer specifications and federal regulations. The add-on NI DIAdem Crash Toolkit provides a set of pre-programmed algorithms that can calculate the required injury criteria for comparison to IARVs, eliminating the need for custom coding.

We developed a number of reusable functions using the built-in VBScript programming language and scriptable user dialogs. These functions perform simple tasks like loading and filtering raw channel data, calculating injury criteria like HIC or Nij values, and plotting charts. We have automated virtually all of our analysis and reporting tasks by simply linking various functions in a user dialog. The modularity of the functions also lets us quickly automate new analysis routines as required. We have automated all of the analysis and reporting for our frontal sled, side impact, static, linear impact, torso, and steering wheel tests.

The new system is easy to use and requires very little training. From a single menu, the user loads data files, runs analyses, and generates reports by simply clicking the appropriate buttons and answering a series of questions presented in pop-up windows. The system also reduces errors, because data does not have to be manually entered into a spreadsheet. Tests performed using test dummies of various types and sizes require different analysis time intervals and IARVs; our system automatically recognizes the type of test and the dummy used and applies the correct time interval and set of reference values, eliminating another potential source of error.

We can also easily accommodate non-standard analyses. For example, the result of a typical crash analysis calculation is a number like the HIC₁₅ value. This single number represents the probability of skull fracture. An alternative way of evaluating the forces exerted on the dummy is to calculate the load duration during the crash event and then plot the resulting curve against an established limit curve. This analysis incorporates the idea that high loads can be tolerated for very short periods, while lower loads applied over a longer time can also cause injury. The DIAdem Crash Toolkit provides a function to calculate the load duration curve, which is then automatically plotted against the correct limit curve for the dummy size being evaluated.

Our time savings have been substantial. We benchmarked our new system against our old method using a series of 10 sled tests. The old method required about four hours for one engineer to compile the data, verify accuracy, perform the analysis, and generate a report. Using our new system based on DIAdem, one engineer can perform this same task in less than five minutes. As we perform more than several thousand tests annually, we anticipate savings of thousands of man hours per year.

We store our completed analyses as TDM files and we can easily query the historical data using the DIAdem DataFinder. The DataFinder continually indexes the data files so we can structure searches using multiple filtering criteria. For example, we can search out historical test data for all frontal sled tests at a speed of 25 mph, with a fifth percentile female test dummy in the driver seat, and where the HIC₁₅ value was less than 700. With this ability to look back in time, we can quickly eliminate non-productive design ideas or configurations as we develop future products, saving both time and money.

We also benefit from other features of the DIAdem system, specifically the video-viewing feature, PDF file export, and the TDM import into Excel. We previously had no easy method to synchronize a test video to a data plot. With DIAdem, we know exactly when a peak force or acceleration occurs while reviewing a test video. Further, DIAdem can export reports as PDF files with the click of a button – very useful when data needs to be reported in a form that cannot be changed or modified. An add-on for Excel is also available making it easy to import TDM files into a spreadsheet, giving us the ability to create time history files in an ASCII format for customers or users who want to use the data in another program or application.

With DIAdem, we have greatly reduced the amount of time required to evaluate multiple tests, resulting in significant cost and time savings. Future development will focus on automating the report-writing process. Eventually, we anticipate being able to go from raw data files to analysis to finished engineering reports in a matter of minutes.

For more information, contact:

Jeff Blackburn,

2500 Takata Dr.

Auburn Hills, MI 48326

Tel: (248) 475-6611

E-mail: jeff.blackburn@takata.com

 

 

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