Research On Ultrasonic Thickness Measurement System Based On DSP

Through the study on the real-time thickness measurement technology of some composite material used in space technology in impacting and ablative situation, this paper analyzes the present situation and problem of composite material thickness measurement, and then mainly studies ultrasonic thickness measurement based on DSP technology and introduces the scheme design of the thickness measurement system. And further, this paper establishes simulation model of echo basing on the propagation and echoing property of ultrasonic in some composite material anomalous object, and according to this, analyzes the feasibility of applying Wavelet Modulus Maximum Algorithm and correlation algorithm to thickness measurement. Finally, correlation algorithm is chosen as the kernel algorithm of this paper. Threshold Detection and Subsection Conic Interpolation are added to correlation algorithm to improve its precision, because seriously distorted echo will lead to low precision of correlation algorithm, as can be seen from computer simulation result that the echo under the influence of surface waviness.To fulfill the need of real-time detecting, this paper adopts DSP chip, which works with CPLD to control transducer to send and receive pulse signal and A/D transform and etc, as the central processing chip in the scheme design of the thickness measurement system. It is introduced in detail in digital signal processing section that transducer is excited by D Push-pull Amplifier to launch ultrasonic pulse and sample the echo. Modular design is used in the system software design. This paper presents not only the main idea about primary framework of the system, but also program flow of DSP algorithm, parabolic interpolation algorithm and thickness measurement, and finally analyze the result of testing composite material sample and point out the reasons that may lead to error. It is proved that this system has achieved the preconcerted target by analyzing the effectiveness of improved correlation algorithm, and stability and effectiveness of thickness measurement system.