SRS : SRS UGV Components : COMPASS

COMPACT OUTDOOR MULTIPURPOSE POSE ASSESSMENT SYSTEM (COMPASS)

COMPASS aids teleoperation control by providing a display of a vehicle's coordinates on the Operator Control Unit in vehicle position estimation applications. COMPASS is available as an off-the-shelf item and has been sold commercially, as well as to multiple government agencies. COMPASS is ideal as a teleoperation system driving aid or an autonomous navigation position estimation subsystem. For this application, COMPASS has already been purchased, and it is described here to illustrate how it can fit into the proposed effort.

The COMPASS sensor suite is an integrated system that provides a continuous update of a robotic vehicle's position using position and orientation estimation (POSE) sensor. These sensors are fused into a single best estimate using a proprietary Kalman filter technique developed by ORI. This POSE estimation sensor suite is packaged as a “Black Box”, with a single RS-232 or CAN interface to communicate the pose estimate to the Vehicle Control Unit.

Omnitech’s COMPASS system can be fitted with different types and qualities of sensors to meet the specific criteria of the application to be solved. When COMPASS is used as an actual position feedback reference for a closed loop vehicle position servo application, the parameters are very similar to conventional servo system applications. Typically there is a trade off between three major factors: accuracy, vehicle speed, and cost effectiveness. Thus the system can be designed to optimize one of these parameters, or trade off between two parameters, but optimizing all three simultaneously is not easy given a fixed level of funding, and sensor and processing technology.

Based on the top-level design parameters desired for this applications, ORI uses a suite of sensors for the COMPASS system that will meet the most difficult specifications. This approach uses a state-of-the-art GPS system to obtain the primary position estimate with very high accuracy.

Differential, Carrier-based GPS specifications:

• 12-channel C/A, 12-channel P code (L1)
• Full wavelength carrier on L1
• Real-time kinematic measurements with on-the-fly initialization
• Horizontal accuracy: 20 cm Circular Error Probability (CEP) RMS with good satellite constellations
• Vertical accuracy: 30 cm RMS
• Cold start to first data: 70 seconds
• Warm start to first data: <30 seconds
• 3-axis inertial grade accelerometers
• 3-axis rate/position gyroscopes
• 1-axis fluxgate magnetometer compass
• Odometry from water speed indicator (pitot tube) for vehicle velocity feedback
• 2-axis inclinometer

These sensors are combined with an onboard computer, executing an Omnitech proprietary Kalman filter sensor fusion algorithm to provide a statistically optimal pose estimate from the sensor suite.

COMPASS Datasheet in PDF format (426k)