HIL drives real-time test requirements
As system designs involve increasingly complex devices and subsystems, engineers can face challenges applying the HIL technique.
Rick Nelson, Editor in Chief -- Test & Measurement World, 3/1/2010 12:00:00 AM
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Design and test functions are inextricably linked in today's complex system-level electrical and mechanical designs, where simulations stand in for prototype hardware during many phases of the design process. Model-based design is an enabling technique for HIL (hardware-in-the-loop) testing, in which, for example, a physical ECU (electronic control unit) prototype interacts with a software simulation of the rest of the vehicle in which the ECU will ultimately be deployed. In a MotoTron ECU application (figure), National Instruments hardware and software products simulate and respond to sensor feedback and actuator commands to verify that the unit under test performs as it should in a closed-loop system. Model-based design and HIL testing have found success in medical-device, industrial-machine, power-generation, aerospace, and even white-goods applications as well as in automotive and other industries (Ref. 1).
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But as system designs involve increasing numbers of increasingly complex devices and subsystems, engineers can face challenges applying the HIL technique. Chris Washington, a senior product manager at NI, explained that new HIL interfacing is becoming difficult because, for example, units under test are increasingly incorporating the sensors that measure parameters—such as temperature, pressure, and acceleration—that a simulation would normally provide in the HIL process. Consequently, real temperatures, pressures, and accelerations must be provided—in real time—during the HIL process. Washington called the approach “real-time testing” and said it has been applied to wind-tunnel, environmental, and dynamometer testing applications.
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Requirements for real-time test, Washington said, include configurable I/O, a run-time editable user interface, multichannel synchronization, and stimulus generation and datalogging capability. NI supports real-time test with its NI VeriStand software in conjunction with LabView and other software as well as PXI and other hardware. Multicore-ready VeriStand, introduced last August, implements the common functionalities of a real-time test system to help developers configure a real-time system. In addition to supporting NI hardware and software, VeriStand supports third-party data-acquisition and FPGA-based I/O interfaces and third-party modeling environments including The MathWorks' Simulink and ITI SimulationX.
Washington said several customers have successfully applied the NI-based real-time test approach: Siemens, for example, applied it to HIL testing of wind-turbine control-system software, and MicroNova used it in the real-time thermodynamic simulation of combustion engines.
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