The Control System For Horizontal Displacement Measurement Of The Ground

Landslide appears when hill collapses because of it's deforming gradually and up to a critical point threshold. When Landslide comes, ground displacement becomes greater than before, so measurement for them is effective and also difficult to monitor and forecast landslide.A technique displacement by using quasi-static frame of reference is introduced in this dissertation. This technique can achieve real time monitor landslide displacement, which has excellence performance on high precision, large dynamic range, sensitive response to landslide displacement and strong stability. The construction and control of a long period conical pendulum as a quasi-static frame of reference was studied, the dynamics equitation of conical pendulum was built in terms of analysis mechanics and the transfer function was derived; the principle of seismic isolation by using conical pendulum was analyzed in detail. In order to measure displacement exactly, a high precision photoelectrical displacement sensor was designed and tested. How to fix and adjust the mechanical device was also explained. During the instrument was set up, its performance was tested and close to theoretic calculation. At last isolating capability of the whole system was tested under simulated environment of ground oscillation. The conclusion as follow:-1. The most important part of system, which is conical pendulum as quasi-static frame of reference, was studied. We brought forward a new style of long period pendulum and built up its dynamic equation. The transfer function in response to displacement was also obtained and the principle of low frequency isolator was expounded.2. We designed a high precision photoelectric displacement sensor. The principle of sensor is to utilize photovoltaic nature, which insures high precision, linearity and fast response. The sensor possesses micrions of precision and 1 millimeter of dynamic range and 10ns of response time. The sensor run stability and the concordance of result are excellent.3. Mechanical structure of the conical pendulum system is introduced in detail. The shape of frame is rectangle. Test mass is connected to the pole with a blade and rabbet which is fixed on two pieces of steel wire fastened on the frame. All weight of pole and conical pendulum are carried on the wires. Because of elasticity of the wire, the rabbit at the bottom of pendulum can move up and down but does not on horizontal. One dimension free motion of the conical pendulum is obtained and difficulty of mechanical process is reduced.4. The character of conical pendulum was tested when instrument was fixed and adjusted. The longest period of pendulum was 3s. It could run stably. The conical pendulum rang down slowly with 2s period as its damping factor was very small.5. We tested the signal response of system under simulated environment. The transfer function curve of the system was calm for high frequency inspiriting. We also observed the resonances of system which coincided with these of theoretical conclusion.6. The control conical pendulum is introduced. We designed electromagnetic damper. The principle of damping and driving circuit are introduced. Because of widely signal response, if dealing with the data and converting to the geometrical construction, the conical pendulum system can also measure ground tilt and monitor earthquake.