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 the condition of a structure, the structure having at least one surface that reflects light from an environment surrounding the structure and having the 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, 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 images are arranged in a plurality of frames comprising at least a first frame and a second frame;
wherein the data processing system monitors said structure by:
sensing a change in a measurement of an intensity of at least one pixel in the first frame compared to the second 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; and
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 from a learned baseline condition are sensed and reported.
2. The system of claim 1 , wherein said structure is selected from the group consisting of buildings, models of buildings, beams, cables, actuators, mechanical support structures, towers, rotating equipment, reciprocating equipment, piping, ducts, conveyors, and presses.
3. The system of claim 1 , wherein said physical parameter related to movement of said selected portion of said structure is selected from the group consisting of: physical displacement; frequency; phase; maximum displacement; and damping rate.
4. The system of claim 1 , wherein said continuum of operation is established over a range of time having one or more noncontiguous time periods and wherein said structure is exposed to a normal range of service duty and external environmental conditions during such range of time.
5. The system of claim 1 , wherein said continuum of operation is established by comparing measurements from one or more similar elements on the structure to determine at least one change in a dynamic property of the structure based on at least one change in a symmetry of measurements for the one or more similar elements.
6. The system of claim 1 , wherein said data processing system is further configured to locate a user-selected region of interest on the structure and wherein said physical parameter is measured at multiple locations on the structure with the region of interest identified by a user using a GUI.
7. The system of claim 1 , wherein said measured parameter is made at multiple locations on the structure identified by a user using one or more fiducial marks mounted on the structure.
8. The system of claim 1 , wherein the data processing system is further configured to calibrate a position of a video camera with respect to the structure based on a positioning of one or more fiducial marks mounted on the structure.
9. The system of claim 1 , wherein the data processing system is configured to perform in response to said one or more deviations at least one of trigger an alert, generate a time stamp, or save recorded data to permanent storage.
10. The system of claim 9 , further comprising a second video camera for obtaining the images, wherein the second video camera is capable of being mounted to view the structure from a different perspective than the first video camera, wherein the second video camera is triggered by the alert to acquire and save a recording which can be used to identify a current duty cycle or said one or more deviations.
11. The system of claim 1 , wherein the data processing system is triggered by an external alert from a sensor that detects one or more events, whereby the data processing system generates a time stamp, and saves recorded data to permanent storage along with any metadata which provides supporting documentation related to the one or more events.
12. The system of claim 11 , wherein the sensor is an optical sensor, an audio sensor, or an accelerometer.