How Crusher Works

There are three primary focus areas in Crusher's development:

Crusher's skeleton is made of aluminum and titanium. Its hull is an aluminum space frame (an open structure of connecting rods) with ultra-sturdy titanium nodes joining the rods for added strength in the likely event of collisions with large, hard objects. Immediately below the hull is a skid plate - basically a suspended, shock-mounted steel "bumper" that stands as a first-defense, protecting the hull from initial contact with the likes of boulders, tree stumps and steps.

To keep it moving over obstacles and generally unfriendly terrain, Crusher sports a six-wheel, all-wheel-drive system powered by a hybrid diesel-electric setup that allows for nearly silent operation - a handy characteristic in recon work. A 78-horsepower, turbo-diesel engine acts as a generator in the system, outputting a continuous 58 kilowatts (kW) of power to charge Crusher's 300-volt, 18.7-kW, lithium-ion battery pack. The batteries in turn run six 210-kW electric motors, one situated in each of the six wheel hubs. Each motor produces 282 horsepower. Like most hybrid-electric power systems, Crusher makes use of regenerative braking to return some power to the batteries each time it slows down (see How Hybrid Cars Work to learn about regenerative braking). The vehicle can run on silent battery power alone for 2 to 10 miles (3 to 16 km) depending on speed and cargo load.

Since each wheel is independently powered, if one or two die, Crusher can keep going. It needs only four of the six wheels to maintain its capabilities. And if it finds itself in sudden need of a turnaround -- say, surrounded on three sides by unpassable barriers - it can use its skid-steer ability, a turning radius of zero, to quickly about-face with no wiggle room at all.

To fit under low-hanging obstacles, face rocky terrain or better hide from the enemy, Crusher has a zero-to-30-inch (76-cm) adjustable ride height. In addition to height adjustment, Crusher's suspension can travel a full 30 inches to absorb shock, and it features adjustable stiffness for varying ground conditions. We were able to locate an under-the-hood view of Spinner, Crusher's predecessor - remember that Crusher is an upgraded version of Spinner 1.0:

Crusher's powerful frame, six-wheel-drive setup and extreme suspension capabilities enable the UGV to travel at high speeds, currently up to 26 mph (42 kph), over difficult terrain, facing obstacles like ditches, boulders, steep inclines and vertical barriers up to 4 feet, all without missing a beat.

Sturdiness, power and silence make Crusher an ideal scouting tool, but it's primarily the UGV's autonomy system that DARPA has so far shelled out $35 million to develop. The NREC hasn't released much detailed information about the UPI system, but says that "this technology spreads sensing abilities across the entire vehicle to help balance its perception and also support vehicle areas that may be less adept at sensing the environment. The [sensing] software will also let Crusher 'learn' and apply previously gathered information to new obstacles."

We do know that the perception hardware consists mainly of LADAR (laser detection and ranging) units and camera arrays. A LADAR unit sends out a laser beam to scan an area and measures how long it takes for the beam to be reflected back to the unit's laser sensor. Crusher has eight of these units - four scanning the environment horizontally and four scanning vertically. It uses six pairs of stereo-vision cameras for depth perception and four color cameras to apply a color pixel to each point of distance determined by the LADAR sensor.

The most recent incarnation of Crusher features an 18-foot telescoping mast for collecting data from a higher vantage point. The mast may incorporate parts of the LADAR and camera assembly seen above, or it may simply add an additional set of sensors to the perception system.

With all of the LADAR and camera data combined, Crusher's onboard CPU creates a 3-D picture of the landscape in which Crusher is traveling. The CPU is a 700-MHz Pentium 3 that controls Crusher's mechanical activities and runs the navigation software that handles sensor-data processing. An inertial measurement unit (IMU) detects Crusher's altitude, position and direction of movement using a combination of accelerometers (tilt sensors) and gyroscopes, so Crusher is always aware of its own motion and position relative to the landscape. The UGV also has a built-in GPS receiver and computer-based GPS database that includes pre-programmed terrain data.

So far, field experiments have shown that Crusher is well on its way to true autonomy. In testing, Crusher moved from GPS waypoint to GPS waypoint spaced more than 0.6 miles (1 km) apart without any outside control. Using its perception and navigation systems, Crusher can react to obstacles on the fly - it doesn't need an operator to tell it what to do when it hits something. It can climb an incline greater than 40 degrees, drive right over a 4-foot step and cross an 80-inch trench using its own decision-making capabilities. The trench-crossing ability is especially cool - Crusher's tires are mounted in such a way that they can drop down to support the vehicle while it's crossing a gap.

Crusher Specs:

The size and weight specifications mean that a single C-130H cargo plane can carry two Crushers into battle anywhere in the world. As of August 2006, Crusher has been fitted with a Rafael Mini Typhoon mount that holds a .50 caliber rifle, pointing to the possibility that combat roles may become an increasingly prominent focus in the development of autonomy technology for military vehicles. In the next section, we'll take a look at the future of the Crusher prototype and find out how it fits in with the overall trend in military research and development.

As of 2006, the U.S. military has deployed approximately 4,000 battle robots for active duty. The military uses these robots primarily to "sniff out" bombs and clear buildings and other enclosed structures. The Army's Future Combat Systems (FCS) program is looking to spend about $300 million to fund updates to expand the roles of battlefield robots. The FCS seeks robotic mules that can carry cargo alongside troops over uneven terrain and much larger unmanned vehicles that can operate with no human input to scout areas and patrol borders, sending crucial data back to troops. If these large, autonomous vehicles can also carry huge payloads over difficult terrain without losing speed, that'd be an added bonus. Crusher or something like it would be ideal in the latter roles.

Crusher itself will probably not see deployment. It's mostly a research project and will be in testing and experimentation until 2008. At that time, the NREC will turn the Crusher technology over to DARPA so it can be applied to related projects, most of which fall under the domain of the Future Combat System. The FCS is running development programs like the Armed Reconnaissance Vehicle (ARV), which aims to realize a fully autonomous, battle-ready vehicle for reconnaissance missions; and the Autonomous Navigation System (ANS), an overarching program to develop common-platform autonomy capabilities for a wide range of military robots. The overall goal of FCS is seamless integration of both manned and unmanned vehicles, ground and air, into a structure that can be managed via a single, web-like control system.

By way of FCS, we may see Crusher-like vehicles supporting troops in battle operations in five to 10 years. They'll most likely start out in reconnaissance roles and then transition into combat, supporting troops as opposed to replacing them. But Crusher's cutting-edge autonomy technology is not military specific. The NREC envisions – and has in the works – research projects that utilize the systems developed for Crusher in civilian applications. In a decade, we could see autonomous vehicles performing risky tasks in areas like farming, mining and construction, ultimately transferring some of the danger faced by humans in these fields onto replaceable robotic counterparts that feel no pain.

For more information on Crusher, UGVs and related topics, check out the links on the next page.