SubscribeThe ICx™ Technologies Fido® is an extremely sensitive, portable explosives detector.
It is comparable in performance to trained bombsniffing dogs - the gold standard by which trace chemical vapor sensors are detected. The sensor has been widely deployed among U.S. and Allied forces in Iraq and Afghanistan, where it is making a positive contribution in the fight against improvised explosive devices (IEDs), the greatest threat currently facing our troops.
Due to this success, the Fido XT, a handheld configuration of the sensor, was named one of the US Army's "Top 10 Greatest Inventions for 2005." In 2006, the robotic version, the Fido OnBoard™, was recognized with the same award. In the words of General Paul Kern (U.S. Army, Ret.),
“...one could easily estimate that hundreds of individuals have avoided serious injury or death," because of the Fido technology.
Augmented Standoff Detection
Standoff detection is the "holy grail" in the fight against IEDs. While many technologies have appeared promising, they have been completely impractical in the real world. Until a revolutionary new technology is discovered and matured, combat planners and homeland security strategists need to make better use of the assets currently available to help detect explosive threats at safe distances.
The Fido sensor, integrated onto robotic vehicles, is a combat-proven detection method. This version, known as Fido OnBoard, has been integrated onto unmanned ground vehicles (UGVs) and remotely piloted aircraft for IED detection. The Fido SeaPup™ has been integrated onto underwater robots for sea mine and underwater unexploded ordnance detection. This 3 Figure 3 - Demonstration of the chemical sensing mechanism behind Fido. The vial at right contains a minute amount of explosive material.
Specialized version of the sensor has radically different integration and operational requirements and is not discussed in detail in this paper.
Core Technology
The basis of the Fido system is an amplifying fluorescent polymer (AFP), originally synthesized at the Massachusetts Institute of Technology and exclusively licensed to ICx Technologies. AFP fluoresces when exposed to light. However, when a molecule of explosive material attaches to the polymer, the fluorescing response of the material decreases. This response is magnified by the structure of the polymer. This reduction in fluorescence can be detected by the system's photodetector.
The sensitivity of the Fido sensor results from the design of the polymers. Each polymer consists of individual fluorescent monomers that are linked in a molecular wire configuration. This allows efficient electronic transfer between polymer repeat units. In this way, when a single molecule of explosives binds to a monomer and quenches its fluorescence, the effect is transferred along many interconnected polymer repeat units. This amplifies the quenching response relative to traditional fluorescence quenching, in which a single fluorophore is quenched upon binding of a molecule of target analyte is a schematic of the Fido sensor.
The sensor is a serial AFP array utilizing two sensor channels. The same polymer, or different polymers, can be deployed on each channel. Samples are drawn into the sensor from ambient air through a glass capillary that has discrete bands of AFP coated inside the bore of the capillary. In this example, two bands of polymer are deployed.
A separate laser diode excitation source is used to excite each polymer band. The lasers are modulated at different frequencies, enabling the emission of each band to be measured with a single photodetector. The capillary is utilized as a waveguide, directing the light emitted from each polymer band onto the photodetector. A digital signal processor (DSP) is used to control the output of the laser diodes, and to process the signal from the photodetector.
Integration Methodologies
To date, the Fido has been successfully integrated with more than a dozen different manufacturer's robotic platforms. Integration is generally very straightforward, and basic robot-to-Fido communications are quickly established.
The Fido OnBoard can be integrated onto robotic platforms in three different configurations. In the first, only the Fido sensor head and a separate communications box are typically attached to the robot. In the second configuration, the entire handheld Fido system is inserted as a payload. A third set-up features a wireless or tethered interface (up to 60') for use on long robotic arms such as can be found on some MRAP (Mine Resistant Ambush Protected) vehicles.
The first integration uses a special Fido robotic interface attached to the sensor head (Figure 5).
Direct connection is preferred, although cables with lengths up to 20' (6.1 m) can be used. Data output is via the auxiliary port, with USB, RS-232, RS-485, or I2C as interface options. External power (9V to 28V DC) is required. The sensing head is approximately 5" x 3" x 1.5" (12.7 cm x 7.6 cm x 3.8 cm) and weighs less than 1 pound (0.5 kg). This version is the most compact method currently in production, but does not allow for data logging of detections. This means the transmitter on the robotic platform must transmit the Fido data back to the controller and be formatted for proper display.
The second method is to use the handheld controller directly connected to the sensor head, or via a cable with lengths up to 10' (3.0 m). Data output is transmitted by the auxiliary port interface of the controller. Communications' options are the same as listed above. The unit is powered by internal batteries or by external power as noted above. This version requires somewhat more space, but allows for data logging. While data logging stores the information
obtained during inspection, no real-time data is transmitted unless the robotic platform is configured as in the first method above.
Either variant operates using 10 watts at startup and 4 watts continuous power. The standard Fido head requires a camera mount-style attachment (1/4" x 20"). The robotic interface box mounting bracket can be provided without standard mounting holes pre-drilled to allow mounting-hole customization. Additional options include incorporation of a video overlay (NTSC) and audio output. Audio output can include warning tones, mono or stereo signals, analog via audio out (handheld only), or algorithms to optionally produce audio signal from information in Fido digital data stream.
A third configuration, known as Fido Remote™, has recently been prototyped. In this method, the Fido is used as in the first configuration and is connected to an additional small interface box. A cable of up to 60' (18 m) connects a remote display box that routes power for the system and provides data logging and real-time information of Fido responses. A small weather station can also be connected to this interface box, allowing meteorological information to also be displayed and logged. Using wind direction data, the Fido can be placed in the optimum location for vapor detection. Power can be from standard 12V- or 24V-vehicle power, or battery for the display box to power the system. A wireless version with the same components is in the design phase and will only require the addition of battery power at the Fido sensor location.
Data Communications and Interfacing
Data flow is unidirectional and streams automatically upon power-up. It has fixed-length packets, with a packet rate of approximately 20Hz. Error and status bits are included.
Bandwidth usage is ~400 bytes/second. RS-232 can be 9600 baud. The system generates status/warning bits. At a minimum, display status bits (binary or hex format) are required. Optimally, decode status bits would be included to display user-readable messages. There are 8 status bits, contained in a single byte of the data packet. With optional
audio, the system will transmit analog information from the handheld Fido or recreate the audio from the digital data stream.
User interface elements include a dual channel Fido percent quench. Readings include a display in a simple bar graph form, current readings, and maximum reading (user resettable). The user can optionally set a threshold and there is a threshold alarm (with visual and/or audible feedback).
Operational Considerations
Fido is relatively easy to integrate onto robotic vehicles. However, simply bolting a Fido onto a robot and establishing a communications protocol will not ensure success. For example, while there are times when a large amount of explosives can produce a signature from a distance, the sensing tip typically needs to be close to the suspect item. Other operational factors to be considered include the following:
The robot must have an articulated arm with a wide range of motion for best exploration
of the scent path.
- The robot and arm must operate at low speeds.
- The sensing tip is heated (90° C/194° F) and is NOT suitable for direct sniffing of people.
- Sensing Elements are rated for 8 hours of operation.
- Many explosives do not have high vapor pressures. If no vapor is present, there is nothing
for Fido to detect. - The operator must have keen understanding of scent, wind direction, and other environmental considerations (e.g., reduced chance for detection in air at low temperatures).
We emphasize that customer expectations must be kept reasonable. When considering the effectiveness of a Fido-Robot combination, we suggest thinking in terms of what could be expected of a well-trained bomb-sniffing dog. For example:
- Could a dog be strapped onto the front of a vehicle, driven down the road at 90 km/h and be expected to let out a bark when it caught a whiff of a bomb? No
- Can a dog interrogate specific places and be expected to make a detection? Yes
- If the ambient temperature is 0° F? No
- Could you hand the bomb dog to a new recruit and expect to find threats? No
- Will the dog be able to find every kind of improvised explosive mixture? No
We believe that asking such questions helps to frame integrator and user expectations.
Summary:
As robots grow in importance in combat and homeland-security roles, their use as sensor platforms will also grow. The Fido sensor is a small, lightweight, extremely sensitive explosives detector that is uniquely qualified for quick integration onto virtually any capable robotic vehicle. Nevertheless, it is not a "silver bullet," and operational capabilities and limitations must be clearly understood for successful deployment.