Zhao Jianhui

An Effective Approach for the Noise Removal of Mud Pulse Telemetry System

Mud pulse telemetry is a method used for measurement-while-drilling (MWD) in the oil industry. Information (tool-face orientation, temperature, pressure etc.) which is modulated by means of pulse positioning modulation (PPM) is sent from the bottom of the well to the surface by means of pressure waves in the drilling fluid (the drilling mud). Due to the influence of kinds of noise, the noise removal before decoding is of great importance. Considering the drilling fluid pulses depending on the position and the width of the pulse to transmit the information, after the description of the mud pulse telemetry system and the analysis of the received signal, a new method based on the digital filter to process the signal received from the down-hole to recover the useful signal is applied. The result and the decoding process indicate that all of the pump noise, the reflection noise and other random noise can be wiped off, and the received signal can be recovered effectively and decoded with low error rate.

Research on the method of suppressing sun and moon's interference on infrared conical earth sensor

To measure the attitude of a satellite, conical earth sensor is usually used on the low- and medium Earth orbit satellite. By detecting the infrared radiation at the horizon using infrared detectors, the conical earth sensor gives a measure of the attitude of a satellite. However, when light from the moon or sun comes into the field of view of the conical earth sensor, it will capture unexpected pulse signals that will induce measurement errors and finally bring about attitude fluctuation of the satellite. In this article, the mechanism of such an interference has been analyzed in depth. By detecting and discriminating the pulse widths of the sun, the moon, and the Earth, a novel method was presented and new software was developed to eliminate the interference. Furthermore, a special ground test platform was set up to verify the proposed method and software. Some real on-orbit flight data were applied as well. Both results showed that the sun and moon’s interference was identified and rejected without corrupting the horizon crossing.

The digital control implementation of swing scanning system on infrared earth sensor

Swing scanning infrared earth sensor brought forward special requirements (wide swing amplitude: ±15°, narrow swing amplitude: ±5°, frequency: 5~10Hz) to the swing scanning control system. Analog scanning control system has some shortages, such as: inflexible to adjust control parameters, hard to implement complex control algorithm and low control accuracy, etc. This paper proposed a digital control method based on FPGA to improve the flexibility and control accuracy of the system. Due to the key problem of low precision of optical grating for the swing scanning control system, this paper proposed a novel method of FPGA based subdivision for optical grating to improve the control accuracy. Experiments showed that the method could meet the requirements of low speed and high precision control for the swing scanning control system.

An Open-Loop Characteristic Testing System of Coriolis Mass Flowmeter Based on Virtual Instrument Technology

Coriolis mass flowmeter (CMF) is becoming a research hotspot in flow measurement for its high accuracy and multi-parameter measurement. Through the dynamic study on CMF’s vibrating model, get the conclusion that the key factors of close-loop system design is the open-loop characteristic parameters such as natural frequency and mechanical quality factor (Q value) et al. An open-loop testing system specialized for CMF is designed based on virtual instrument technology using Graphical Programming Language (LabVIEW). The algorithm adopts the rescanning sweep-frequency activating method. Experiment results show that the system has high frequency resolution, can analyze the open-loop characteristic of CMF rapidly and accurately, and also reduces the hardware cost to the full extent.

Auto Calibration Test Method and Device for Swing Scanning Earth Sensor

Swing scanning Earth sensor (SSES) is one of the key components in Middle Earth Orbit (MEO) satellites and High Earth Orbit (HEO) satellites for attitude sensing. Traditional calibration and test method could only be used in completely installed SSES. According to analysis of the calibration and test task in the uninstalled SSES, a new method and device which constitutes a closed-loop calibration test system in different development stage of SSES is proposed. The experiment and application results show that the method and device presented in this article constitute a better calibration test system for developing and producing the SSES.