FEATURE MILITARY, AEROSPACE & DEFENCE


Imperial College London’s challenge was: To develop a data acquisition system to


synchronously record data from sensors attached to postmortem human limbs and a test rig to simulate the impulse transferred to a soldier’s leg during an underbelly vehicle explosion


established at the LabVIEW Core 1 course, National Instruments support engineers and the LabVIEW VI library helped us complete our first LabVIEW code iteration within two weeks, and it was just one month before we had the final software,” explained Newell. Using LabVIEW it is possible to define


AIMING FOR military personnel safety


Data acquisition technology from National Instruments is proving to be a reliable solution for military systems. In one example we take a look at the development of a test rig which aims to understand the mechanisms of IED (improvised explosive device) injuries. In the second we examine how a company has improved the performance of its shooter detection system which is capable of detecting the direction of incoming small-arms fire


mprovised explosive devices (IEDs) – homemade bombs – are the leading cause of fatalities in Iraq and Afghanistan. If a vehicle is struck by an antivehicle (AV) mine, the floor rapidly deforms, and occupants who have their feet resting on the floor experience an axial impact that frequently leaves them with injuries so severe that their lower extremities cannot be salvaged. Research is therefore being carried out


I


at Imperial College London which aims to understand the mechanisms of IED injuries in order to develop technologies to mitigate this threat and to perform appropriate reconstruction. The research involves an injury simulator that replicates AV mine blast loading in a repeatable, controlled environment, using multiple sensors to monitor the events of the short-duration incident. The AV underbelly injury simulator


(ANUBIS) is a pneumatic test rig capable of accelerating a 40kg steel plate to 20m/sec and back to rest within 20ms, simulating vehicle floor deformation in a typical AV mine blast. By mounting and


26 JULY/AUGUST 2014 | INSTRUMENTATION


impacting an instrumented postmortem human specimen1


on this rig, it is possible


to gain a comprehensive understanding of how the body reacts to the short- duration impact, explains Nicholas Newell from Imperial College’s Bioengineering Department, Royal School of Marines. Newell commented: “The injury


simulator includes a pressure sensor, an accelerometer and an acoustic sensor. During each test, we bond strain gauges to various bony cadaver parts and sample all of the synchronised sensors at a 25kHz frequency. We manually trigger data acquisition with a push button moments after the rig fires. The recorded data is then converted to results analysis format.” For ethical and financial reasons the


data acquisition had to be reliable and accurate, so NI-DAQmx with LabVIEW system design software and PXI Express high-specification hardware was chosen to create the test rig. “We put the LabVIEW system code through many iterations before we used it for cadaveric test data analysis. Skills we


Research is being carried out at Imperial College London which aims to understand the mechanisms of IED injuries in order to develop technologies to mitigate this threat and to perform appropriate reconstruction


the total number of samples, sample rate, number of pretrigger samples and file location and name for the data to write in the GUI before the test begins. LabVIEW is designed so that once the software runs, the buffer fills with data from each of the sensors and the code waits for an analogue falling-edge trigger into one of the PXI Express modules. After the system receives this trigger, the data is synchronously recorded from every channel on the PXI Express chassis. The recorded data is presented graphically and written to a file to export for further analysis. LabVIEW flexibility and the modular PXI Express system gave the research team the option to alter the code and hardware for future experiments. The National Instruments setup was, for example, used to acquire data from similar impact tests with instrumented car crash test dummies and drop-rig tests. Newell adds: “Recreating battlefield


injuries in a controlled laboratory environment requires a complex engineering solution. With state-of-the- art National Instruments diagnostics, we gain unprecedented, high-resolution insight into the mechanisms of an event that lasts less than 5ms.”


SHOOTER DETECTION Data acquisition technology has also been selected by Raytheon BBN, a high- technology company that provides research and development services, for its Boomerang shooter detection system. Using an array of seven microphones, Boomerang detects the direction of incoming small-arms fire from the shock wave and muzzle blast, indicating the azimuth, range and elevation of the shooter in less than one second. A clock face display shows the direction of fire and a recorded voice announces the direction and range. Azimuth, range and elevation are displayed on an LED screen display. Algorithms in the Boomerang system suppress return fire events by users. In addition, Boomerang does not generate false alerts commonly caused by non-ballistic events such as road bumps, door slams and wind noise, or other extraneous noise events such as vehicle traffic or firecrackers. The system requires extensive signal processing and testing of algorithms to provide reliable and robust performance over a wide


/ INSTRUMENTATION


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