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Proceedings Paper

Use of hardware-in-the-loop (HWIL) testing from early software development through final system test to mitigate risk and to assure mission success for the Hera targets program
Author(s): Michael Marcin
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Paper Abstract

The CRC Hera targets program integrates Government Furnished Equipment, that includes Pershing II flight computers and Minuteman boosters, to provide threat representative targets to the U.S. Government in support of theater missile defense interceptor test programs. Hardware-in-the-Loop (HWIL) and Computer-in-the-Loop (CIL) testing is used, from initial software development through system and software qualification, to evaluate Hera target vehicle performance. The CIL and HWIL closed loop test methods differ not only in the amount of hardware needed for the test but also in the level of system validation. CIL flights using only a real- time simulation computer and a flight computer to create a closed loop test environment for the airborne software. We use this method for the development, validation and certification of the flight software. HWIL flight testing employs both actual missile flight computers and inert booster motors with actuators. The flight computer, actuator controller, and two reaction control systems from the actual flight missile are connected to lab shop queen equipment. This equipment includes first and second stage motor nozzle actuators, battery and ordnance simulators, raceway cables and the telemetry system. The HWIL test not only verifies proper airborne software operation but also verifies the flight computer interfaces with raceway cabling and the missile subsystems. The HWIL test demonstrates the flight readiness of the airborne software and several key pieces of flight hardware. Both nominal and stacked tolerance simulation runs are used to validate the flight code and to provide stressful conditions to verify the robustness of the flight control system. Monte Carlo runsets using known CIL/HWIL interface errors, such as scale factor, bias and noise, are used to create minimum-maximum boundary value plots. These boundary value plots provide guidelines to verify and validate the airborne software tested by the CIL/HWIL simulated flights. Comparisons of flight data from three of our test flights and corresponding CIL/HWIL runs show an excellent match of flight performance to pre-flight predictions. The CIL/HWIL testing on the HERA targets program made it possible to have a high degree of confidence in the flight software and hardware before our first mission. We achieved first flight success due in part to the extensive software and hardware testing in the CIL/HWIL environment from software development through system qualification.

Paper Details

Date Published: 24 May 1996
PDF: 13 pages
Proc. SPIE 2741, Technologies for Synthetic Environments: Hardware-in-the-Loop Testing, (24 May 1996); doi: 10.1117/12.241119
Show Author Affiliations
Michael Marcin, Coleman Research Corp. (United States)


Published in SPIE Proceedings Vol. 2741:
Technologies for Synthetic Environments: Hardware-in-the-Loop Testing
Robert Lee Murrer, Editor(s)

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