Researchers develop sensor system to assess how blasts impact human body

Improvised explosive devices (IEDs) are becoming a global problem for the U.S. armed forces. To prevent injuries to soldiers and provide better care to those who are injured, the U.S. military is striving to better understand how blasts impact the human body.

In 2011 the Army’s Rapid Equipping Force (REF) approached the Georgia Tech Research Institute (GTRI) to develop a system that measures the physical environment of an explosion and collects data that can be used to correlate what the soldier experienced with long-term medical outcomes, especially traumatic brain injury. The solution: the Integrated Blast Effect Sensor Suite (IBESS). IBESS is the first system to acquire integrated, time-tagged data during an explosive event – whether soldiers are on the ground or riding in a vehicle – and can later help recreate a holistic picture of what happened.

System of systems
There are two parts to a blast: a shock wave that travels at supersonic speed, and compressed air, which travels in front of the shock wave. Both can cause considerable damage to the human body, but the exact effects are unclear.

“No one knows to what extent overpressure or acceleration causes injuries,” said Marty Broadwell, a principal research scientist at GTRI who manages the institute’s projects with REF. “Nor do we know how quickly an injury will show up, how long it will last or which soldiers are more resistant to harm than others. The only way to understand the impact of a blast is to collect data, which is precisely what IBESS does.”

How it works
IBESS features two major subsystems: a unit worn by the soldier and a vehicle sensor suite. The soldier system is contained in a canvas pouch, which attaches to a soldier’s armor between his or her shoulder blades. A recorder in the pouch connects to four pressure sensors, two on the back and two on straps that hang over the front of the shoulders. Because these sensors face different quadrants, the unit captures directionality and more information than previous blast gauges.

“Soldiers already carry considerable gear, so reducing the weight of the body unit and power consumption of its batteries drove many design decisions,” said Brian Liu, a GTRI research engineer who served as technical lead on the project. For example, the recorder in the soldier body unit remains in sleep mode until pressure or shock waves hit a certain threshold, causing it to wake and begin recording data. This allows the system to have longer battery life and remain relatively transparent to the wearer.

The vehicle system serves a dual purpose: It records blast events that affect the vehicle, but also interacts and automatically links with the soldier system. When a soldier enters a vehicle, a base station installed in seats transmits RFID signals. If the soldier system has stored any data, these signals initiate a Bluetooth connection that enables two-way communication and data transfer. This semi-passive RFID technology is proximity based; transmission and reception occur only at very close range, so IBESS can identify a soldier’s precise location in the vehicle.

Sensors are also installed on the vehicle’s interior frame and seats. If an explosion or rollover occurs, these sensors collect linear acceleration and angular rotation data. The soldier system also wakes up and begins to record and transmit data. A single board computer aggregates data from both the vehicle and soldier systems and then passes it on to a rugged black box for final storage.

IBESS is specifically designed to withstand tremendous forces of an IED explosion.

“Materials, mounting strategies and mechanical isolation strategies have been used to ensure the devices successfully capture data in ‘survivable’ events,” Liu explained. “We first conducted research on what kinds of magnitudes of blasts were survivable for mounted and dismounted operations and then performed many tests at those levels for verification.”

IBESS is innovative on many fronts:

• Synchronized data: Unlike earlier generations of blast gauges, all data in IBESS is time-tagged, using GPS time as common time source. “Using this data we can rebuild an event,” Liu explained. “Even though soldiers aren’t wired together, we’ll know they were in the same vehicle and experienced the same event — and can assess how an event propagated through.”

• Scalability: GTRI researchers used as many off-the-shelf and standard components as possible. “This open architecture makes it easier to expand the system,” observed Douglas Woods, GTRI research scientist and IBESS program manager.

• Anonymity: By leveraging the Department of Defense’s Common Access Card (CAC) system’s Personal Key Identifier (PKI), IBESS can collect information uniquely tied to individual soldiers. Use of the PKI makes the data virtually anonymous so other researchers can study it without compromising privacy or containing personally identifiable information.

Another hallmark of the project was its rapid completion schedule. REF awarded the contract to GTRI in July 2011. Researchers wrapped up preliminary designs in September, and by early 2012 they were testing and refining the system. IBESS units began to ship overseas in August, and now the system has been issued to more than 650 troops and will be installed on 42 vehicles in Afghanistan.

“Our work with GTRI has been outstanding,” said Joe Rozmeski, REF’s deputy chief of technology management. “Originally chosen for its sensor expertise, GTRI has proven to be an ideal partner for us. They understand their role perfectly and are in tune with the REF’s objectives for integrated blast effect research and collection.”

Understanding the challenge
At its peak, the project involved more than 50 researchers with expertise ranging from electronics to mechanical engineering to health systems. This diversity in disciplines was critical to IBESS’ success.

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