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8 results on '"Yaohuan Lu"'

1. Distance Measurement of Contra-Rotating Rotor Blades with Ultrasonic Transducers

Author

Shan Zhang, Yaohuan Lu, Zhen Qiu, Wenchuan Hu, Zewen Dong, Zurong Qiu, and Yongqiang Qiu

Subjects
rotor blade distance, ultrasonic ranging, bandpass filtering, TOF estimation, Mechanical engineering and machinery, TJ1-1570
Abstract

Coaxial rotor helicopters have great potential in civilian and commercial uses, with many advantages, but challenges remain in the accurate measurement of rotor blades’ distance to prevent blade collision. In this paper, a blade tip distance measurement method based on ultrasonic measurement window and phase triggering is proposed, and the triggering time of the transmitter is studied. Due to the complexity of the measured signal, bandpass filtering and a time-of-flight (TOF) estimation based on the power density of the received signal are utilised. The method is tested on an experimental test platform with a pair of 200 kHz ultrasonic transducers. The experimental results show that the maximum ranging error is less than 1.0% for the blade tip distance in a range of 100–1000 mm. Compared with the amplitude threshold method, the proposed TOF estimation method works well on the received signal with a low SNR and improves the ranging accuracy by about 5 mm when the blade tip distance is larger than 500 mm. This study provides a good reference for the accurate measurement of rotor blade tip distance, and gives a solution for ranging high-speed rotating objects.

Published
2024
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2. Review of Ultrasonic Ranging Methods and Their Current Challenges

Author

Zurong Qiu, Yaohuan Lu, and Zhen Qiu

Subjects
ultrasonic ranging, transducer, pulse echo, time of flight, error compensation, Mechanical engineering and machinery, TJ1-1570
Abstract

Ultrasonic ranging has been widely used in automobiles, unmanned aerial vehicles (UAVs), robots and other fields. With the appearance of micromachined ultrasonic transducers (MUTs), the application of ultrasonic ranging technology presents a more extensive trend. This review focuses on ultrasonic ranging technology and its development history and future trend. Going through the state-of-the-art ultrasonic ranging methods, this paper covers the principles of each method, the signal processing methodologies, the overall system performance as well as key ultrasonic transducer parameters. Moreover, the error sources and compensation methods of ultrasonic ranging systems are discussed. This review aims to give an overview of the ultrasonic ranging technology including its current development and challenges.

Published
2022
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4. Research on wingtip distance measurement of high-speed coaxial helicopter based on 77 GHz FMCW millimeter-wave radar

Author

Zhiyuan Zhang, Zurong Qiu, Wenchuan Hu, Yaohuan Lu, and Wenjie Zheng

Subjects
Applied Mathematics, Instrumentation, Engineering (miscellaneous)
Abstract

Aiming at the requirements of short-range, high-precision, and high-speed measurement of coaxial helicopter wingtip distance measurement, a millimeter-wave radar wingtip distance measurement scheme is proposed, and the ranging accuracy of frequency-modulated continuous wave millimeter-wave radar is improved by optimizing the frequency estimation method and the beat-frequency signal processing process. The multi-antenna data coherent superposition method and the correlation search for the estimated frequency are used to shorten the measurement period, and at the same time, the ranging accuracy of the millimeter-wave radar can be improved, and the single measurement time can be guaranteed. Based on frequency refinement, frequency offset method, phase method, amplitude method and fitted approximation method, the frequency estimation of millimeter wave radar differential frequency signal is combined with the influence of bandwidth, measured target shape and material on ranging to improve millimeter wave radar ranging performance comprehensively. Through simulations and experiments, the accuracy, stability, time consuming and application conditions of the optimized algorithm are comprehensively evaluated, and the feasibility of millimeter wave radar wingtip ranging is verified.

Published
2023

8. On English Adverbials: An English Teacher’s View

Author

Yaohuan Lu

Subjects
Structure (mathematical logic), Absolute structure, Grammar, media_common.quotation_subject, Path (graph theory), Mathematics education, Duration (project management), Psychology, Term (time), media_common, Style (sociolinguistics)
Abstract

For Grade two students in Senior High School, what is of vital importance is that students establish clear grammar networks at least after the second term to prepare themselves well for the first-round review of the third year and the following College Entrance Examination. With the scattered language points such as “with complex structure”, “participles used as adverbials”, or “absolute structure” learned by students in a gradual style, it is essential for them to clear out a main thinking path or thinking framework to make connections between knowledge points. The author finds in her years of teaching duration the relations between English adverbials, making it easier for students to know the know-how of learning English in a much scientific and reasonable way. Here are the findings.

Published
2020

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