Non-contacting monitor for bridges and civil structures
A system for monitoring the movement of objects, structures, models of structures, cables and the like provides for the acquisition of images with an optical sensing device such as a video camera fixedly mounted at a selected distance from the item studied, in which the images are arranged into frames divided into pixels which are characterized by an intensity reflected or emitted over a selected time interval, and a data processing system to calculate a physical displacement as function of time of the item being studied or a portion of the item being studied based on an output from the video camera, and in some embodiments the system visually distinguishes one or more locations in the frame to indicate a difference in the phase of motion for multiple objects appearing in the frame.
1. A system for monitoring a condition of a structure, the structure having at least one surface that reflects light from an environment surrounding the structure and having a capacity to store and emit heat from said environment, comprising:
a video camera that obtains sampling data as a plurality of video images of the structure, with the video images being divisible into individual video image frames comprising at least a first video image frame and a second video image frame, and with each video image frame being divisible into a plurality of pixels;
a data processing system configured to monitor said structure using images of the structure obtained from the video camera, wherein the video image frames comprise images of the structure which include at least a first moving part and a second moving part;
wherein the data processing system monitors said structure by:
sensing a change in a measurement of intensity of at least one of the plurality of pixels in the first video image frame compared to the second video image frame, the intensity resulting from one or both of visible light energy resulting from light reflected from the at least one surface of the structure or infra-red energy emitted from thermal heating of the structure over a selected time interval;
calculating a physical parameter related to movement of said selected portion of said structure as a function of time;
establishing a continuum of operation for said structure during a first period that is referred to as a learning period which is characterized as a condition of baseline operation of the structure, and a second period referred to as a monitoring period when one or more deviations a learned baseline operation condition are sensed and reported; and
displaying at least one image from at least one of the video image frames containing the first moving part of the structure and the second moving part of the structure wherein the at least one image has been modified to indicate a difference in phase of motion between the first moving part and the second moving part.