For autonomous navigation, a mobile robot needs to consider its position and orientation within a certain working coordinate frame. The so-called localization problem is usually solved by a mixture of different principles contributing to the state variables of position and orientation, called “pose” in the following. Generally two different approaches are being considered: absolute pose determination and relative pose determination. For each time step, the incremental observation of velocities, angular velocities, forces, or visual characteristics give an information update for the pose variables. Absolute information derived from global landmarks like GPS, however, directly provides position information. In the following, the important variants of pose measurement as well as the required principles of selected sensor systems are described. Also some exemplary implementations are explained in more detail. There are several possibilities to group the different techniques, such as regarding absolute or incremental information or position and orientation sensors. However, it seems most logical to present the measurement principles in an order they can be put together as a whole localization system, supplementing each other.
KeywordsGlobal Position System Mobile Robot Inertial Measurement Unit Inertial System Visual Odometry
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