1.IMU Introduction
The Inertial Measurement Unit (Inertial Measurement Unit) is usually composed of 3 accelerometers and 3 gyroscopes. The accelerometers and gyroscopes are installed on mutually perpendicular measurement axes. Here, their outputs can be regarded as three The acceleration and angular velocity in the direction, expressed as:
2. Introduction to GPS (RTK)
The Global Positioning System (Global Positioning System) should be familiar to everyone. Its output is commonly: longitude, latitude, and altitude, and some also have the speed of North East Sky [VN;VE;VU]. Expressed as:
The integration strategy of the two (two independent systems use loose coupling):::
Loose combination
Loose combination means that the GPS receiver uses the navigation filter to process the pseudorange and carrier phase observations into independent position and velocity navigation solutions, and directly inputs the GPS position and velocity data into the Kalman filter as observations. Perform recursive least squares estimation, and perform navigation correction on inertial navigation; GPS and inertial navigation are input into the integrated navigation framework as two independent sets of position and attitude parameters, and there is a feedback loop between the integrated navigation framework and GPS and inertial navigation, and finally Generate a single combined navigation solution.
Its characteristics are: use GPS observation value to correct the navigation solution output by the system; use inertial navigation error state feedback to correct the inertial navigation solution of the next epoch.
The combined positioning results calculated from the position and velocity observations of the GPS receiver will be subject to some restrictions. If the GPS solution is interrupted, the system can still generate combined GPS/IMU results (reverse smoothing algorithm), but the position accuracy will degrade over time until the GPS solution converges again. If the GPS receiver only receives three satellites, but at least 4 satellites are required in differential mode, then the GPS receiver cannot calculate the navigation solution, and the data received by the Kalman filter of the GPS-aided inertial navigation is that there is no GOS receiver Auxiliary data; also outputs pseudorange and carrier phase observations regardless of whether the receiver is tracking the satellite or not.
1: The state estimation space uses the mean value of the IMU to calculate the position
2: Calculate the RTK data in segments:
