Perpendicularity measurement method of 3-D large guideway with theodolite

Based on the mechanism that theodolite leads to a moving line, a new method of measuring the perpendicularity of guideway was presented. Firstly, a theodolite is installed on the horizontal linear moving base of Y guideway and a crosshair target is fixed on the foundation. When the theodolite is on different positions and pointed to the target as the level guideway is moving, the horizontal angles of the target are acquired. So two horizontal angles of the theodolite can be computed using least square method twice when the two collimation axis lines of the theodolite are parallel to the moving lines of X and Y guideways respectively, then the perpendicularity between X and Y guideways is calculated. After that, the theodolite is fixed on the foundation, the slight vertical angle changes of the target fixed on the horizontal linear moving guideway are observed, and the levelness errors of X and Y guideways are fitted respectively using least square method. Later on, the horizontal angle changes of the target fixed on the vertical Z guideway are measured with the theodolite, and the 2-D plumb errors of the Z guideway are achieved also using least square method. Finally, all the X-Y, Y-Z, Z-X three guideway perpendicularities are obtained, and the measurement error analysis is conducted. This method was applied in adjusting and measuring the perpendicularities of a lunar soft landing simulation system. Results show that this method can meet the requirement of the measurement accuracy.