Anchor Calibration for Real-Time-Measurement Localization Systems

This article investigates the effect of additional calibration modules (CMs) in a 3-D real-time localization system during the calibration of the anchor position. A quick calibration is desirable for new anchors that are positionally undetermined in the working coordinate system. Three localization methods were tested for the anchor calibration: multidimensional scaling, semidefinite programming, and iterative trilateration. First, the accuracy of the anchor localization was studied by simulating a change in the number of additional CMs and their positions. Second, tests on a real system with ultrawideband modules were performed to validate the improvements in the anchor calibration when using the additional CMs. The experimental results revealed an improvement in the anchor localization for all three methods, where the average positional error was improved by 0.01 m in the first scenario and 0.30 m in the second scenario. The MDS method had the best absolute performance, with an average positional error that was as much as two times less in comparison with the other two methods. This investigation demonstrates that the positional error can be successfully reduced by using additional CMs. The calibration of anchor positions in the working coordinate system using additional CMs resulted in a 3-D error of less than 0.32 m.