Multilateration measurement using laser trackers suffers from a cumbersome solution method for high-precision measurements. Errors are induced by the self-calibration routines of the laser tracker software. This paper describes an optimization solution model for laser tracker multilateration measurement, which effectively inhibits the negative effect of this self-calibration, and further, analyzes the accuracy of the singular value decomposition for the described solution model. Experimental verification for the solution model based on laser tracker and coordinate measuring machine (CMM) was performed. The experiment results show that the described optimization model for laser tracker multilateration measurement has good accuracy control, and has potentially broad application in the field of laser tracker spatial localization.
In order to investigate the influence of velocity circulation on the hydraulic performance of large axial-flow pumping stations, an accurate prediction method is necessary to be built. In this paper, vortex flows of pumps with internal cavitation and non-cavitation are firstly described by the velocity circulation theory. And then a CFD model, i.e., SST k-omega turbulence model is used to calculate the two different working conditions of the pump system with cavitation and non-cavitation. In addition, experiment is conducted to investigate the external characteristic curve of the real machine model pumps, which verifies the si mulation results. The influence of velocity circulation on hydraulic characteristics is revealed. The research shows that under the optimal condition, the error of head of the pump between numerical calculation and experimental measurement is 3.58%, while the error of efficiency of pump is 3.31%, which indicate the accuracy of SST k omega turbulence model. Furthermore, the external cha racteristics and cavitation characteristics of pumps are predicted, and the critical cavitation pressure (Pc) and fracture cavitation pressure (Pt) are obtained. By compar ing the liquid flow deviation angle (y) of the two condi tions, it is shown that the angle (y) velocity circulation and hydraulic loss of the pump internal passage increase as the pumps cavitation occurs. And by comparing the angle (y) under different flow coefficient, �, which is defined as the ratio of operating f10wrate (Q) and design f10wrate (Q), it is shown that the values of y increase rapidly as the oper ating conditions of the pump deviate from the design one, and the maximum of y appears when the pump operates under small flow coefficient; and when cavitation occurs in the pump, the values of y increase, which changes the velocity circulation and increases the pump internal pas sage hydraulic loss.
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