3자유도 위치결정시스템의 위치오차 보정에 관한 연구

Abstract

A method to compensate position errors of a 3-D.O.F. positioning machine is proposed and studied to evaluate the feasibility of the method. Conventionally, the moving part such as a carriage and a linear slide is defined as rigid-body assumption to study the error evaluation. However, this conventional method is not suitable to compensate the position errors of the end-point on the machine. This method is only effective to analyze the errors of the individual moving part because these errors propagate to the position of the end-point. For this reason, we proposed a new method that includes a concept to identify a relationship between machine and sensor coordinate systems. Since identification of the relationship is inherently unattainable, an alternative machine coordinate system is needed. This alternative coordinate system is easy to establish since this needs only three actuated positions on the machine. Assessments to confirm the capability of the proposed method were performed. Factors that affect uncertainties of the method were studied and the final uncertainties of the compensation values were estimated. From the results, we confirmed that the uncertainty of the measurement system is only affected to the performance of the proposed method. Optimal conditions to minimize the uncertainty were also acquired and the uncertainty was estimated from linear interpolation to establish the usable conditions. Finally, performances of the conventional compensation method and the proposed method were compared quantitatively. Serial and parallel high precision positioning machines are proposed to apply the proposed compensation method. These machines consist of three PZT actuators and flexure hinge mechanisms for high precision actuation. Kinematic analysis, stiffness design and performance test of driving ranges and resolutions were studied. The position errors of both machines were measured and the errors of the serial positioning machine are much larger than that of the parallel machine. All the errors of the machines were compensated to the level of nanometers successfully within several compensating iteration steps. Therefore, these successful compensating experiments of the positioning errors showed the feasibility and availability of the proposed method.