Research On Non-intrusive Pressure Measurement Technology Based On Multiple Regression Algorithms

Pressure vessels are widely used in all aspects of industrial production and our daily life. To guarantee that they are operating safely and stably, it is essential to detect and control the internal pressure in time. Traditional methods for pressure measurement are intrusive and require drilling holes in the vessel wall. However, the operation process is complex and will easily lead to new security risks. Therefore, non-intrusive pressure measurement method has attracted great attention of scholars at home and abroad, which has become a hot research topic in the field of pressure measurement. On the basis of the relevant literature and the latest achievements, a method for pressure measurement based on multiple regression algorithms is proposed. Experimental results show that, compared with the measurement model based on converted waves, the method proposed in this thesis can effectively reduce the effect of residual stress. The measurement accuracy has been significantly improved at the range of 0-2MPa, and the repeatability performance is better. The main contents and innovations of this thesis include the following aspects:(1) A new method for pressure measurement based on multiple regression algorithms is proposed. According to the previous method based on converted waves, at the range of 0-6MPa, the relative-average error (RAE) is less than 7% and the root-mean-square error (RMSE) is within 0.3MPa. But the error of the pressure measurement is still relatively large at low pressure. Although the measurement model based on converted waves effectively lower the influence of temperature, the accuracy is still to be improved due to the residual stress. Therefore, a method based on multiple regression algorithms is proposed to solve the nonlinear problems of model at the range of 0-2MPa, which can restrain the influence of residual stress, and has a smaller measurement error.(2) The effect of the fixed characteristics of probe on the detection performance is investigated. A mechanical device which can precisely measure the probe load is utilized. The effect of the fixed characteristics of receiving probes on the ultrasonic signal amplitude and the travel-time change is also discussed. Experimental results show that the amplitude of received ultrasonic signal will increase with the probe load and stay at a stable level when the load increases to a certain extent. Besides, the travel-time change of the ultrasonic wave will be influenced by the fixed load variation. The travel-time change caused by the fixed characteristics and the travel-time change induced by the pressure are in the same order of magnitude. Therefore, in practical application, it is necessary to ensure the fixed characteristics of the two receiving probes consistent, which can obviously improve the accuracy of the pressure measurement.(3) An experimental system for pressure measurement is established. A water vessel is chosen as specimens, the correctness of measuring model is tested and the performance of different measuring models is evaluated. Experimental results show that the method proposed by this thesis can reduce the influence of residual stress and gain higher accuracy of the pressure measurement under low pressure environment.