Monocular vision-based decoupling measurement method for multi-degree-of-freedom motion

The most common forms of target multi-degree-of-freedom (MDOF) motion include plane and space motions, whose accurate measurement is crucial for the fields of pose estimation, inertial navigation, and structural health monitoring of buildings. Currently, the primary methods used for the MDOF motion measurement are laser interferometry, grating ruler-based method, and sensor-based method. However, the laser interferometry is operationally complex, costly, and it requires strict environmental conditions. Although the grating ruler-based method is low-cost and accurate, its applicable frequency range is limited. Moreover, the sensor-based method suffers from limited accuracy and dynamic range. To achieve accurate measurement of MDOF motion across a wide frequency range, a new monocular vision (MV)-based decoupling measurement method is investigated. This method utilizes a specially designed measurement mark, combined with an improved Harris corner positioning algorithm with sub-pixel accuracy and decoupling models for plane and space motions, which has the advantages of high measurement accuracy, simple algorithm, and strong robustness. Comparison experiments with the current methods demonstrated that the investigated method can simultaneously accomplish the decoupling measurements of plane and space motions, which achieved the accuracy of 0.66% and 1.29% in the range of 0.1-2 Hz.