Bus interface enhances data acquisition for auto/aero applications
Greg Reed, Contributing Technical Editor -- Test & Measurement World, 11/9/2006 4:24:00 PM
The summer release of a new network interface by United Electronics Industries (UEI) highlighted the company's commitment to in-vehicle physical and electrical testing requirements. The new product—the DNA-CAN-503—is a four-port, high-speed CAN (controller area network) bus interface layer that works with the company's PowerDNA (distributed networked automation) Cube, an Ethernet-based, data-acquisition system designed for a variety of industrial, aerospace, and laboratory applications.
Alex Ivchenko, director of engineering at UEI, recently explained why the products are appropriate for automotive and aerospace applications.
Q: The DNA-CAN-503 network bus interface serves several automotive and aerospace applications. Why these specific applications?
A: DNA-CAN layers are designed to meet physical and electrical requirements for in-vehicle (automotive and aerospace) networks based on CAN. CAN-503 uses an industry-adopted and widely used CAN chipset compatible with almost every CAN device on the market.
Q: Which automotive and aerospace testing, diagnostics, and prototype design exercises are best solved by this type of data-acquisition product?
A: There are three major classes of applications where a CAN layer is used:
Data monitoring/logging. The layer monitors activity on the CAN bus, and the application stores data into the file. Packet filters can be set up in the hardware or can be applied during post-processing. Post-processing is a standard part of the data-analysis procedure. It is performed to convert CAN messages into human-readable format and align them with other types of data collected by the PowerDNA Cube (data from analog and digital layers).
A typical application of this class consists of attaching the CAN layer to an in-vehicle network and monitoring engine parameters from installed sensors and then comparing that information with the data delivered from an ECU (electronic control unit) and vehicle sensors. Sometimes an application requires the CAN layer to send specific messages to an ECU on a predefined time base and store ECU replies. This mode is used to collect data during road tests, mainly for the purpose of tuning up parameters of vehicle control units and validating them for production.
Control application. The CAN layer is used to control the behavior of a device under test (the ECU, for example), apply digital and analog stimuli, and read back analog and digital data. This setup is used for prototyping, research, and diagnostic phases of the vehicle development.
ECU/BCU certification. The PowerDNA is used to exercise a unit as well as simulate a load for the purpose of long-term tests. In many cases, this is a required procedure imposed by a car manufacturer to certify control units for each model year. The duration of such tests can be anywhere from days to months.
Q: What are some primary considerations for developing data-acquisition products specifically for automotive or aerospace applications?
A: In no particular order, here are specific considerations based on customer needs: The product should:
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have a compact and robust form factor;
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tolerate shock and vibration well;
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make it easy to mount, easy to access, and easy to connect signals;
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provide effective heat dissipation within wide temperature range and altitudes, preferably without moving parts (fans);
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tolerate abusive technicians;
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have a set of I/Os that covers high-voltage, low-voltage, and specific sensors and interfaces without the need of external signal conditioning; be very flexible in terms of I/O selection and I/O granularity;
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offer selectable signal conditioning, digital filtering, and improved noise rejection;
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isolate I/Os from the vehicle ground and protected them against electrostatic discharge (ESD), transients, and overvoltage;
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make available real-time and buffered data-acquisition protocols;
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support third-party software, protocols, and libraries of customer preference;
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offer a wide input power range to power directly from automotive and avionics power buses; work on "dirty" power;
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have a high mean time between failure (MTBF); and
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be a commercial off-the-shelf (COTS) product with a competitive price per I/O point.
Q: What are the special challenges presented by auto/aero harsh environments?
A: Harsh environments are a given for both automotive and aerospace applications, so all parameters must be satisfied to the greatest degree possible. Superior units have all-aluminum construction and are designed to withstand shocks and vibration. These units are tested and certified for operations within -45°C to +85°C, 50-g shocks, 5-g vibration, and elevations of up to 70,000 ft. All connectors need lock-in or screw-in design.
PowerDNA units are compact in size and have low power consumption. Their thermal design effectively dissipates heat. They can be powered with DC power from 9 V to 36 V. This range covers automotive (12 V), trucks and off-road equipment (26 V), and aerospace (27 V) applications. In the future, units will be able to work from a 42-V in-vehicle power bus.
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