Abstract
Error measurement of a rotary axis is the key to error compensation and to improving motion accuracy. However, only a few instruments can measure all the motion errors of a rotary axis. In this paper, a device based on laser collimation and laser interferometry was introduced for simultaneous measurement of all six degrees-of-freedom motion errors of a rotary axis. Synchronous rotation of the target and reference rotary axes was achieved by developing a proportional–integral–derivative algorithm. An error model for the measuring device was established using a homogeneous transformation matrix. The influences of installation errors, manufacturing errors, and error crosstalk were studied in detail, and compensation methods for them were proposed. After compensation, the repeatability of axial and radial motion errors was significantly improved. The repeatability values of angular positioning error and of tilt motion error around the y axis and x axis were 28.0″, 2.8″, and 3.9″. The repeatability values of translational motion errors were less than 2.8 μm. The comparison experiments show that the comparison errors of angular positioning error and tilt motion error around the y axis were 2.3″ and 2.9″, respectively. These results demonstrate the effectiveness of our method and the error compensation model.
Highlights
Rotary axes are widely applied in computer numerical control machining, robotics, aerospace, and other fields
These results demonstrate the effectiveness of our method and the error compensation model
Detector D1 records the changes in the interference signals, which correspond to the radial motion error along the x axis
Summary
Rotary axes are widely applied in computer numerical control machining, robotics, aerospace, and other fields. Chen’s apparatus, using three lasers, is a rare method that can measure the six DOF motion errors of a rotary axis simultaneously and directly [8]. Most of these indirect measurement methods need to determine each error using complex function-fitting algorithms Unlike these existing methods, our method can measure the six DOF errors directly at the same time. Two important methods—a servo-tracking strategy and error model analysis—are used to realize and improve the functions of the measuring device. A device for the simultaneous measurement of the six DOF errors of a rotary axis is introduced, and a method to improve the measurement accuracy is proposed based on our previous research for five DOF errors [2,12]. The repeatability and comparison results were obtained after compensation and demonstrate the effectiveness of our method and the error compensation model
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