·Home ·Table of Contents ·Methods and Instrumentation

The Research for the Measurement of the Moving and Vibration of the Dam System Zhao Jiyin Zhao Jingrong Huang Ting Gai Shuang School of Information Science & Engineering, Jilin University of Technology, Changchun, China 130025 Contact

Abstract

The moving and vibration of the dam in the hydraulic power station is an important factor effecting the security of the dam, which should be measured and monitored on real time. In this paper, we introduce a measurement system for the moving and vibration of the dam. It includes optical system, linear array CCD image sensors measuring unit, microprocessor unit and computer control system. This system works well and the minimum measuring error is less than 7 µm.
key words: moving and vibration of the dam , measurement system, CCD image sensor

1.Introduction

The dam is one of the most important parts of facilities of hydraulic power station. The safety of the dam directly affect the people's live and property. The tremendous thrust and pressure of the river, lake and sea make the dam produced micro-moving and vibration. Although the dam seemed to stand firm, it is possible for the dam would be landslip because of the pressure for long time. It will lead economic losses and misfortune for people. So the dam should be measured and monitored on real time[1]. The paper introduce a measure system which include CCD(Charge Coupled Device)image sensor, MCS-51 single-chip system and industrial controlling computer system. The system detects the moving and vibration of dam through CCD image sensor, the data processing and communication is done by single chip. The industrial controlling computer can monitor, record and store the status of the dam automatically. The data communication between single chip system and industrial controlling computer is performed by RS-485 agreement.

II. Measuring Principle

Fig 1: The principle of the measurement

The moving of dam has following two status:

1. horizontal moving along the direction of current;
2. Vertical moving(axis direction of dam).
So the moving measurement of the dam is a kind of two-dimensional measuring method. The first status will be discussed mainly because of the measuring principles of these two conditions are basically the same. The measuring principle is shown in figure 1.

No.1, No.2, and No.3 are three poles, and they are connected through float mechanism. No.2 pole does not move as the dam moving or vibrating. No.1 and No.3 poles produces proportional moving as the dam moving or vibrating, but the distance between No.1 and No.3 poles does not change. The three measuring poles will be projected on CCD image sensor (it is shown in figure 1(a)). The output signal in figure 1(c) is produced by CCD under the action of CCD frame alignment signal which is shown in figure 1(b). The moving signal is produced after the signal is processed (it is shown in figure 1(d)). So we can get four positions of three levers as follows:




L1=N1+D1/2	(1)
L2=N2+(D1+D2)/2	(2)
L3=N3+(D2+D3)/2	(3)
L4=N4+D3/2	(4)

Where L2 and L3 are horizontal moving of the dam along the direction of current. L1 and L4 measure ranges of the measuring system. The vibration of the dam can be calculated according to formulas (2) and (3). It is showing in following formula

DL=(L2-L3)/2=(N2-N3) / 2 + (D1-D3) /4

(5)

In a word, After the formulas (1), (2), (3), (4) and (5) are carried out data processing and calculated by MCS-51 signal chip, the moving and vibration can be measured on-line and be monitored continuously.

III. Selection of CCD Image Sensor

TCD106C linear array CCD image sensors are employed in moving measuring system of dam. It's main technical parameters are as follows:


(1) Effective image element:	5000
(2) The area of image element:	7mm´7mm
(3) Drive mode:	2 phases
(4) Whole length of photosensitive unit array:	35mm
(5) Feature of spectrum response is shown in figure 2

Fig 2: Spectrum response feature of TCD106C

Considering measure range in system of displacement measurement, we adopt two pieces TCD106C for displacement measurement along the dam of orientation of current. And we adopt one piece TCD106C for displacement measurement across the dam of orientation of current.

IV. Designed parallel tube of light

We make use of parallel illumination of common parallel tube of light, it will put up displacement measurement to shadow of measure pole in CCD. Due to demanding about tube of light, and crowed in the field and so on, it is difficult to carry out high precision measurement. So we must process designing the system of light[2].
Firstly, we think about the selection of source of light for designing the system of light. TCD106C is CCD used P type silicon as underlay. As the figure 2 show, the best range of light spectrum of TCD106C is about 500 - 800A^o . It's range is belong to the visible light. So the system of light adopt the light of halid tungsten as light source. The light source is supplied power by constant current power supply. It can restrain non-linearity of light of halid tungsten and enhance the video signal of CCD.
We design the way of light about parallel light system is shown in figure 3

Fig 3: light track of parallel light system

In the above figure: 1: reflector, 2: lamp-house, 3: diaphragm, 4: grating 5: field lens .

The light, which is eradiated by lamp-house of halide tungsten , is made through focus-glass, diaphragm, and field lens to pool parallel beam in order to make shadow of needle imaged in CCD surface. The system of parallel light both possesses higher degree of parallel and improves the rate of use. Under the conditions of satisfying CCD light intension at fact power, lamp-house of halide tungsten can be used at low-power and advance the life-span of use. For decreasing optical discrepancy, field lens adopt double-glued lens. Movable protect-shell in this system both keeps the system of parallel light and imaging system, and decreases pollution of dust for the system of measuring pathway. The bulk of photo-machinery structure is very small. It is resolved that the key problem to the dam displacement measurement[3] .

V The main structure of the system

According to the measuring principle put forward above, we design the main structure as follows:

Fig 4: The main structure of the system

The three measuring poles will be projected on CCD image sensor because of the irradiation by the parallel light. Then we can get the video signal from CCD driven by phase impulse f₁ and f₂, reset impulse RS and frame synchronization impulse SH.
And we can get the digital signal of the displacement from the video signal by amplification, demodulation, compare circuit and signal-locked process. Under the control of the SCM the video signal goes through WR generation circuit, address generation circuit and data generation circuit, and then the digital signal would be saved in double-ports RAM IDT7032 by itself. SCM 8031 processes data and displays the result after the measurement period controlled by SH. At the same time SCM transmit the measurement data and status to the industrial controlling computer by RS-485 communication agreement. Then we can realize the on-line monitoring and recording. We mixing the digital signal of dam displacement and 32MHz standard clock signal to increase the distinguish-rate and measurement precision of the system.

VI Conclusion

This article put forward a on-line monitoring system to measure the displacement of dam. The system includes optics, electronic and MPU. The system has simple structure, high precision and strong anti-jamming capacity. Examined in practice, the precision of the system is less than 7um. So, it can be used in many domains, such as water power plant etc.

Reference

1. Zhao Jiyin, Dai Yisong, A New Instrument for On-Line Wire Auto-Weighting and a New Metod for On-Line Dynamic Data Processing, The 5^th Multinational Instrument station Conference, MICONEX'92, Beijing, pp.130-135.
2. Shi D Xing, Influence of Vibration on Microdiameter Measurement Using a Laser CCD System, App. Opt, 1993, Vol.32. No13:pp.2304-2311.
3. G.F.Engen, On-Line accuracy assessment for the dual six-port ANA:Background and theory, IEEE Trans. Instrum.Meas. , vol. IM-36, pp.501-506,June 1987.

© AIPnD , created by NDT.net

|Home|    |Top|