RESUMEN
Rotor-stator axial clearance plays a pivotal role in ensuring the safety and efficiency of major rotating machinery. This paper introduces an innovative clearance measurement method based on wavelength division multiplexing (WDM) combined with all-fiber microwave photonic mixing. The method is distinguished by large measurement range, high accuracy and low drift. The WDM-based common optical path structure is established. A comprehensive theoretical model of axial clearance drift determined by wavelength and temperature is developed based on the thermo-optic effect of optical fiber material. To efficiently separate measurement and reference light at the probe, the optical design for a compact optical bandpass filter (OBPF) fiber sensor probe is proposed. The performance of the method is substantiated by simulations and experiments. The results demonstrate an accuracy of better than 2.8µm over a 23.5 mm range, surpassing existing methods. The method's capability to mitigate temperature-induced drift is further confirmed through high-temperature drift and comparative experiments.
RESUMEN
In the domain of frequency sweeping interferometry, the accurate extraction of distance information from nonlinear frequency scanning signals holds paramount significance in ensuring meticulous measurements of high precision. This paper presents a novel, to the best of our knowledge, high-speed distance extraction algorithm based on the table lookup method and validates its feasibility through theoretical models, simulations, and practical experiments. The proposed algorithm achieves comparable accuracy to traditional methods involving resampling and Hilbert transform. However, it outperforms them in robustness against noise and variations in sampling points. This method can accurately process signals sampled even below the Nyquist sampling rate. The simplicity and computational efficiency of the proposed approach make it suitable for various nonlinear sampling applications, promising broad applicability in scientific and engineering contexts.
RESUMEN
Rotor-stator axial clearance is a crucial design parameter affecting rotating machines' efficiency and safety. To accurately measure the dynamic axial clearance in high-speed machinery, a precise method based on time division multiplexing with frequency domain interferometry has been proposed. This method has proven robust and accurate through simulations and experiments. The inclusion of an optical switch enables the utilization of dispersive interferometry(DPI) and time division multiplexing for multiple channels of the light source. It achieves a static accuracy of 1.5â µm for a 15 mm range and a dynamic accuracy of 9â µm at 3000â rpm.
RESUMEN
In this paper, a high-accuracy measurement method for rotor-stator axial clearance in narrow spaces is proposed. The optical path structure based on all-fiber microwave photonic mixing is established. To improve the accuracy and expand the measurement range, the total coupling efficiency over the entire measurement range at different working distances of fiber probe was evaluated by Zemax analysis tool and theoretical model. The performance of the system was verified by experiments. The experimental results show that the measurement accuracy of axial clearance is better than 10.5 um within the range of 0.5-20.5 mm. The measurement accuracy has been effectively improved compared to previous methods. Additionally, the probe size is reduced to a mere diameter of 2.78 mm, which is more suitable for axial clearance measurement in narrow spaces inside rotating machines.
RESUMEN
A robust five-degree-of-freedom (5-DOF) measurement system is proposed in this paper. The compact optical configuration with high resolution is designed based on lens combination and multiple reflections. Beam drift and dual-beam parallelism are monitored and compensated by autocollimator units and a polarizer unit respectively. In addition, a protection method is proposed to reduce the intensity of air turbulence by reducing the Reynolds number of the beam path. The performance of the system is verified by experiments. The experimental results show that the self-compensation methods and air turbulence protection can effectively improve the accuracy and stability of the system under the long-term interference of external environments. The proposed system has high precision, desirable robustness, and convenient pre-calibration, which can be used for error measurement of precision machines.
RESUMEN
Frequency scanning interferometry using state-of-the-art high-speed frequency-swept laser source can be utilized to measure absolute distance on the order of micrometers to centimeters. Current distance demodulation methods based on fast Fourier transform (FFT) or fringe counting cannot achieve satisfactory accuracy when the number of sampling points within a frequency-sweeping period is small; the conventional Hilbert transform is more accurate, but it needs arctangent calculation and phase unwrapping, which is time consuming. So we propose a fast algorithm based on the conventional Hilbert transform to recover the distance from the interference signal. The algorithm is implemented by first performing a Hilbert transform and then solving the phase and the distance from the Hilbert signal with a novel, to the best of our knowledge, method that eliminates the need for arctangent calculation and phase unwrapping. The whole process took only 40 µs, and it is almost 2 times faster than the conventional Hilbert algorithm with little accuracy lost. Simulation results demonstrate that the proposed algorithm is more accurate than the FFT algorithm, and it achieved a standard deviation of 0.062 µm, which was less than that of the FFT, in our experiment at a distance of approximately 16 mm and measurement speed of 1 kHz.