Customer SolutionsLightWave Computing Develops Innovative Fuel Cell Test Software
Author(s):Rob Taylor, LightWave Computing Ltd.
Industry:Automotive
Product:CAN, FieldPoint, GPIB & Instrument Control, LabVIEW
The Challenge:Building a highly responsive R&D proton exchange membrane fuel cell testing system that has the capacity for various stack geometries and I/O requirements.
The Solution:Integrating National Instruments LabVIEW, SCXI, GPIB, FieldPoint, NI-CAN, and TCP/IP into a configurable, high-performance fuel cell testing environment.
The Need for Instant Power Researchers perform automotive fuel cell testing all over the world in an effort to deliver the next generation of vehicle power. A key requirement for an automotive fuel cell is its ability to operate under cold startup conditions, as well as delivering power instantly when required. Delivering instant power requires a test station with adequately responding mass flow controllers, and software that can respond quickly to stabilize pressures under these dynamic flow conditions. In order to properly characterize fuel cell efficiencies, researchers need to take cell voltage (CV) measurements on each individual fuel cell. The test stand requirements dictate software that can be scaled from single cells to more than 500 cells. Furthermore, while some tests require only stack testing, others require testing of complete fuel cell modules comprising the stack as well as ancillary NI-CAN and TCP/IP-based control systems. Researchers need one unified testing environment to use the same test software with stations that run all stack sizes and formats. This requires an adaptable I/O architecture as well as a software model that tunes tests with radically different flow, pressure, and loading requirements. Building a System Using NI LabVIEW, PID Control Toolkit, and SCXI We were asked to write a custom-built LabVIEW program comprising more than 700 virtual instruments using the adaptability of the test station to meet all these test requirements. The main program contains two main loops: one operates the test hardware and the other operates the user interface. In the future with this structure, researchers can migrate the test hardware loop to an NI LabVIEW Real-Time target for a more deterministic response. Splitting off the hardware control into a highly optimized, timed loop along with the use of the PID control toolkit, we met the requirements of a fast, stable response under dynamic load conditions. We developed the system so that three SCXI 12- and 4-slot chassis could be ganged together to access up to 512 CV measurements along with other signals for controlling pressure and test loads. For fuel cell module testing, we connected the software to a proprietary NI CAN or TCP/IP-based module control system to read larger CV banks and allow ancillary control through the CAN bus. We selected cooling, heating, and humidification controls using NI FieldPoint I/O and SCXI. We ran a separate LabVIEW maintenance application on each test station that identifies the hardware capabilities of the station, which is saved in an INI file format for when the test station software is launched. We used the NI LabVIEW Enterprise Connectivity Toolkit so the database tracks the UUT history and test parameters. Automation and Simulation In the LabVIEW software, we included the capability to record test macros in progress to show the repeat of key test sequences. With one button, the operator can record subsequent control changes on the interface and save these test changes to a macro file. In playback mode, the user interface controls move in the same timed sequence as if an operator set the controls. While a macro is executing, the operator has the option of pausing the test and making adjustments before continuing. The operator can record multiple test sequences as macros and then concatenate or arrange them in complex loops to perform test sequences with many thousands of test steps. Additionally, if an event is detected during a test (for instance, a cell voltage drops below a minimum value) the operator can execute a special recovery macro. The operator can later edit these macros in Microsoft Excel. Using this rich automation functionality, researchers can quickly identify strategies to improve fuel cell testing. The operator can run the LabVIEW fuel cell test software either on a test station PXI chassis or in a special simulation mode on any PC desktop. In the simulation mode, the operator safely records and tests macros from a PC with no external devices connected. Simulated analog feedback from the test device gives the researcher a good feel for how the test station is likely to perform. By doing so, the researcher runs one test on the test hardware while the subsequent test is being simulated in the engineering office, thus saving valuable test time while speeding up the development cycle. The operator is also able to remotely monitor tests from anywhere on the network through a LabVIEW data socket-based applet that tracks the vital signs of all running tests in the test lab. When test failures need to be tracked after an operator has left the test facility, the software can e-mail specific failure information to a fan-out list of text pagers. The operator can log data either to an InSQL database or to a CSV formatted file, which can be imported into Excel or NI DIAdem for post-test analysis and reporting. The operator can log data only when a low-cell-voltage event has occurred or by a fixed time interval. NI System Replicates True Conditions of an Automotive Fuel Cell System Using LabVIEW and the NI wide array of I/O products, we were able to provide a complete software solution to all of these requirements. Through the seamless integration of hardware devices, we developed this system in much less time and without the headaches often associated with developing multivendor solutions. The end users benefit from an efficient, scalable testing environment that replicates the true operating conditions of an automotive fuel cell system. For more information, contact: Rob Taylor LightWave Computing Ltd. Tel: (604) 522-1786 Fax: (604) 522-1726 Email: rob.taylor@lightwavecomputing.com Web: lightwavecomputing.com |
