Keeping America's borders secure is a top priority with regard to several challenging issues facing the U.S., drug trafficking and terrorism to name just two. To that end, the United States Border Patrol (U.S.B.P.) is America's frontline against these and other social ills. With violence on the rise and as many as 850,000 people unlawfully entering the United States each year since 2000, the U.S.B.P. has their hands full. In 2006, the Department of Homeland Security's (DHS) Customs and Border Protection (CBP) agency built a “virtual fence” using steel towers equipped with infrared sensors, remotely operated cameras, communications devices, and radar.

Aiding the U.S.B.P is the Night Hawk High Torque Surveillance Platform developed by PVP Advanced Electro-Optical Systems Inc. (PVP), Tustin, Calif., in cooperation with L3-CE, Mason, Ohio. An off-the-shelf DMC-4020 two-axis Ethernet motion controller from Galil Motion Control Inc., Rocklin, Calif., handles the azimuth and elevation motors with positioning accuracy of 0.05°, so each Night Hawk HT is capable of providing 24/7, 360° surveillance for ranges up to 20 miles.

“The Galil controller allows users to point sensors at targets or regions of interest,” says Geoff Miller, program manager at PVP. “The sensors are used to locate and track targets at long range using narrow fields of view. This requires the ability to make very small and accurate movements to keep the targets within the field of view. Also, we are sometimes cued with radar or other sensors, so precise pointing is required to locate targets.”

In addition to its torque limit, tracking error, and modulo position features, PVP uses the DMC-4020 for both the servo controller and motor drivers. Not having to purchase and integrate two separate components allows PVP to save space, wiring, programming time, and cost. The chosen controller also sped production, helping PVP move from concept to prototype within four months, and to shipping fully operational production units in just six weeks. According to an August 2009 article in Photonics Spectra, the DHS expects the virtual fence to help border patrol agents identify and intercept 70 to 85% of all illegal passages in the U.S.