Fundamental Research On Fieldbus Based Intelligent Valve And Its Failure Detection Method And Two-wire Transmission Mode

As an important executive device, the hydraulic valve's safe and stable operation is of momentous significance. So real-time monitoring of the valve's running status and dynamically setting of its running parameters are needed. Also the valve should alarm and handle failure when error occurs. With the expanding of the whole control system, the control network structure is becoming more and more complex. The demand for simplify network topology, enhance the control intelligence and system compatibility, distribute the control function is growing. Under such background, we propose a new intelligent two-wire valve system based on power-line carrier communication and CEBUS.The key techniques involved in the intelligent two-wire valve are valve information abstraction, valve development, application research of CEBUS, power-line modeling and research of power-line communication technique.We first analysis and model the stick failure of hydraulic valve and propose a new non-sensor detection method. We verify its validity by simulation and practical experiments. The experiment shows that this method can well identify the stick failure and do pre-diagnose. The method also can be used to detect oil pollution degree.Then the MCU based intelligent two-wire valve hardware design is studied. A hardware platform combining MCU, CEBUS and power-line communication module is described, and several technical issues are discussed and their practical solutions are provided. The practical experiments of the designed intelligent two-wire valve present a good preferment.We model the power-line channel in chapter 4 as the experimental result shows that the power-line channel condition has civilizing influence upon the valve's communication performance. Here, we establish power-line resistance model base on theory of transmission line. We also establish power-line fading model refer to the wireless channel model. The simulation results and the experimental results indicate the model is well fit to the real power-line.Based on the power-line channel model, we analysis and simulate the performance of the varies communication technique under the real power-line circumstance. We point out that the high voltage power-line carrier communication technique is not fit to the low-power carrier communication circumstance. We also derive and analysis the BER performance of FSK modulation system with different amplitude narrow band disturbance under different SNR. Analysis of // non-linear frequency modulation is provided corresponds to our practical experiment.