Filter Kinematic Constraints

A selection of kinematic constraints is available that can improve Estimation Filter performance under certain dynamic conditions. When enabling these kinematic constraints, it is important to consider the typical motion profile of the application and ensure that the assumption underlying each constraint is satisfied most of the time.

 

Zero velocity update (velocity ZUPT)

This constraint helps stabilize the navigation solution during prolonged stationary periods. This constraint is useful for vehicles which make frequent to occasional stops.

Assumption

The platform is stationary when the reported velocity falls below the user provided threshold.

Command 

 

Zero angular rate update (angular rate ZUPT)

This constraint helps reduce gyro bias errors on the vertical (yaw) axis. This constraint is useful for ground vehicles which make prolonged stops, especially when no heading aid is available.

Assumption

The platform is not rotating when the angular rate estimate falls below a user provided threshold.

Command

Zero Angular Rate Update Control (0x0D,0x20)

 

Wheeled vehicle constraint

This constraint helps maintain a more accurate platform heading, especially during periods of low acceleration and poor . It is not advisable to use this constraint in applications where the platform velocity and heading routinely diverge, such as with aircraft.

Assumption

Components of velocity perpendicular to the primary axis of the platform (as indicated by the mounting transformation) are zero.

Command