The capabilities of a Volkswagen-sized robot to find and track locations of meteorites was tested in the Antarctica ice field by meteorite hunters from Antarctic Search for Meteorites (ANSMET), a National Science Foundation polar program, and robotic scientists from Carnegie Mellon University's Robotic Institute. Ralph Harvey, a planetary geologist at Case Western Reserve University, directs ANSMET's exploration operations in Antarctica.

Nomad, a four-wheeled robot, was developed with support from NASA's Cross Enterprise Technology Development Program. The Robotic Institute developed Nomad for NASA to undertake planetary science research on Earth as an analog to exploring Mars or the Moon.

The independent robot that can autonomously maneuver through difficult terrain and study the composition of rocks and other materials would be a boon to exploration of areas where humans cannot be sent.

Moving at about 1.5 feet (0.5 meters) per second, Nomad uses a high-resolution digital camera to identify rocks and scan them for characteristic signs of meteorites, such as charred surfaces and a aerodynamic shape. It then uses two sets of tools to help it decide whether the rock's origins are indigenous or in outer space.

The first tool, a reflection spectrometer, shines light on the rock and analyzes the reflection. That analysis shows which elements make up the rock. Then, Nomad uses its metal detector to sense whether the rock is composed partly of iron, a sure sign that the rock is a meteor. Nomad's computer processes this data and makes a conclusion on the origin of the rock. If the mission succeeds, project scientists hope a robot like Nomad could be used by NASA -- which is supporting the project -- on a planetary mission.

Transforming Chassis

The transforming chassis enables skid steering as well as explicit steering by using the same motors to deploy the wheels and affect wheel heading. The transforming chassis is based on the motion of four bar linkages connected to each wheel. The wheels are actuated in pairs such that the two right wheels move synchronously (as do the two left wheels) to achieve double Ackerman steering.

Steering

Less wheel power is required in explicit steering, which involves activating both steering mechanisms to allow the robot to arc in a particular direction. Nomad's explicit steering is like that of car except only a car's front wheels actually steer. This method therefore gives the robot greater steering control than skid steering. Finally, the transforming chassis can move both steering mechanisms past deployed mode to allow the robot to perform a point turn. This allows Nomad to stop and change direction to avoid an obstacle.

Internal Body Averaging

The central pivot of the averaging mechanism has a degree of freedom in the vertical direction, which is needed to allow the link to follow the bogies through a maximum wheel excursion of 50 cm. Body averaging of pitch and roll allows Nomad to have greater mobility while maintaining a high level of stability for accurate sensor readings.

In Wheel Propulsion

Nomad features individual propulsion drive units that reside inside the wheel. This is unlike typical all-terrain vehicles, which have a central drive unit that distributes power to each of the wheels. The advantages of in-wheel propulsion include: sealed drive units, identical drive components, simplicity, and improved motion control.

The in-wheel propulsion unit is independent of the steering and suspension systems; no geometric or operational interferences occur between the systems. No electromechanical components are needed for propulsion beyond those enclosed in the wheel (with the exception of the motor wires, which are routed to the body fuselage through the deployment/steering linkages). This allows the drive components to be sealed within the wheel.

The motor and drivetrain assembly is at an offset distance below the wheel axle, which lowers the center of gravity of the wheel and simplifies its structural design and bearing selection. Triangular brackets suspend the drive assembly from the stationary axle. The motor is accessible for ease of removal and replacement if necessary. In the drive unit a brushless DC motor transmits torque and power to the wheel hub through a harmonic drive and a single stage gearing reduction. The output gear is mounted on the inside face of the outward facing wheel hub.

Eliminating mechanical transmission components and coupling assemblies encourages simplicity and thus reliability. Only two bearings are needed to decouple the stationary wheel parts from the moving parts. The simplicity of the propulsion system also imposes fewer constraints on the design of the chassis and the steering mechanism.

Cameras

Stereo Camera

High Resolution Pan/Tilt Camera

Panoramic Camera

Laser Rangefinder

Spectrometer

Reflection spectroscopy is a powerful technique for deducing the chemistry of a rock sample. The sample is lit by incandescent light, and the reflected spectrum is recorded over a fiber optic cable. However, it is necessary to get close to a sample in order that good quality spectra may be obtained. This year, the spectrometer will be manually deployed. A sample therefore requires a much larger amount of effort to acquire than a camera image.

The spectrometer projects light from a small Tungsten-halogen bulb through a reflection probe onto the surface of a target. The same probe collects the light and transmits it via optical fibers to the spectrometer. Inside the spectrometer, a special diffraction grating spreads the light's spectrum onto a CCD chip. The chip then generates electrical signals with strengths proportional to the amount of light that hits its surface. This raw signal is then passed through an analog to digital converter (ADC) that translates it into information a computer can understand.

Raw signals are not very useful to scientists because sampling conditions can vary. Therefore software is used to callibrate the spectrometer that provides scientists and computers with standardized data regardless of what sampling conditions.