Racelogic VBOX 3iV2 User Manual

VBOX 3i User GuidePage 31 of 4628/08/2013IMU IntegrationIMU integration should not be enabled for measurement of Braking distancesThe main purpose of integrated navigation systems is to take advantage of the complementary attributes of two or more navigation systems (GPS and Inertialmotion unit) to achieve far better performance than through the use of either system on its own.GPS derives data through two separate methods, Doppler (speed, vertical speed and heading) and Triangulation (latitude longitude and height). The Triangulationcalculated position data is bounded by an error (CEP value), which depends on the quality of the GPS receiver and its environment. GPS measurements are stablebut rely on weak signals, which are subject to signal blockage and interference from the surrounding environment, resulting in poor performance. The quality of theDoppler derived channels are also affected in a similar way by the same influential factors.Inertial sensor measurements on the other hand are continuously available but suffer from long-term drift due to the accumulation of integration errors of theaccelerometer and gyro measurements. As a result the IMU derived position error increases without bounds. IMU‟s of a higher accuracy are available but tend to belarge, bulky and expensive.These complementary properties of IMU and GPS data make them ideal candidates for integration and can accurately compensate for GPS dropouts or noise.The VBOX 3i has the capability of integrating the GPS data with inertial data from the IMU02 Inertial Measurement Unit allowing accurate smoothing of the followingparameters: Latitude Longitude Velocity Heading Height Vertical VelocityTo use the data from a connected IMU to perform integrated Kalman filtering the VBOX 3i first needs to be set up using VBox Tools.The screen shots here show the new IMU integrated Speed in blue and the non-integrated raw speed in red.In these screen shots you can see how the IMU integrated Speed has continued to be produced perfectly through noisy and full dropout conditions