Ultrasonic roller on-line detection system based on double threshold method

I. INTRODUCTION For the acquisition of milk surface information, the traditional domestic method is to judge the condition of the roll by rolling the surface condition of the steel plate, and change the roll regularly or irregularly. Because it is not an online operation, it will inevitably lead to a part of rolling stock that does not meet the requirements, which will waste resources and waste human resources. Because this method cannot detect the roller type on line, it is impossible to grasp the true condition of the roller surface and the true roller type, and it is impossible to realize the closed-loop control grinding. The online roller can only be performed based on experience, so roller-type online inspection must be performed.

The measurement methods include ultrasonic distance measurement ceremonies, eddy current ranging ceremonies, laser distance measurement ceremonies, and roll pressing. The ultrasonic distance measurement ceremonies are not interfered by ambient light and electromagnetic fields, have working gaps, have a certain adaptability to harsh environments, non-contact measurement, high precision, and moderate prices. Due to the above advantages, this detection method has developed rapidly and is currently the most widely used one. At the same time, the development of related technologies in China is relatively mature. Therefore, it is feasible to measure the roller type on the basis of ultrasonic waves.

Second, the test principle Ultrasonic waves in the same uniform medium, the longitudinal wave sound velocity is a constant, when the ultrasonic wave from one medium to another medium, the total reflection occurs at the interface of the two media, ultrasonic rangefinder is to use This kind of work. The working principle of the ultrasonic roller type detection is the same as that of the ultrasonic distance meter. It is also measured by the pulse reflection method. Its principle formula is skW. According to the different times of reflection, it is divided into a pulse reflection method and multiple pulse reflection method. Because the ultrasonic probe is close to the roller, about 5060mm, while the ultrasonic wave in the German famous film type platinum resistance large bursts, large quantity of excellent stupid - sensor world research dynamics based on â–¡-ultrasonic warming s in the special early evening Wen Shuhui Duan Huifang Zheng Dezhong saliva The propagation speed is about 1450m/s. Therefore, the multi-reflection method can improve the accuracy of the system and the reliability of the circuit.

Ultrasonic waves vary greatly in speed in different media. Even in the same medium, the speed of sound varies with temperature. Changes in pressure, viscosity, or composition. The deviation generated in the accurate measurement cannot be ignored. To do this, channels can be set in the system to compensate for the distance between the probe and the roller surface to a fixed value. Since the ultrasonic probe uses high-pressure water jet to purify the detection medium, the temperature, pressure and other conditions in the water circulation system are the same, and the measurement channels and channels are under the same working conditions. The sound speeds in the two channels are the same, so no need to consider the temperature, pressure, etc. The impact on speed of sound. Then the distance from the measuring probe to the roller can be expressed by the corresponding value measured in the channel. The expression is as follows: - the distance of the channel, the distance of a measuring channel, the propagation time of the ultrasonic wave in the channel, and the propagation time of the ultrasonic wave in the measuring channel. .

Ultrasonic waves propagate in the medium. Due to its own attenuation and absorption of the medium, the amplitude and waveform of the received wave will change. If the simplest rising edge detection method, single threshold method, is adopted, the actual counting moment occurs after the theoretical value due to the presence of the threshold value, ie there is a deviation between the actual arrival time and the measured value, which changes with the ultrasonic wave. The distance between the device and the roller surface to be tested changes. Therefore, we use a more sophisticated rising edge detection method and a double threshold technique to measure the ultrasonic propagation time of the channel. As shown, the rising edge of the echo is approximately linear and can be expressed as follows: Ar-pulse start time, V, one frame Value, the time when the ultrasonic amplitude reaches K.

In the dual threshold technique, the two threshold voltages can be expressed as follows: Given F, F2, can be derived directly from two thresholds: Since the synchronization pulse has a large delay in the line, two echoes can be used. Zero crossings determine the propagation time of the sound waves. As shown, the two zero-crossings are respectively the heart and /20, which is obtained by the formula (3):, =V2'n~v\\210" Roll type ultrasonic testing feasibility study, METER, manufactured by Mitsubishi Heavy Industries, Ltd., Hiroshima Institute, No.1 Wen Shuhui, Hebei Province, Qinhuangdao, Hebei Province, School of Electrical Engineering, Yanshan University, Telephone Reader Service Card No. 004 Sensor World No. 0 Tong Suochuan specializing in the production of pressure, degree, level, wash, speed and other sensors and Various measurements, control instruments, environmental conditions, state monitors, temperature concentration detectors, and self-controlled data acquisition systems.

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