Vibration Measurement and Analysis Using Image Processing Method

A large number of people are exposed to whole body vibration in their occupational life. Measuring vibration is an important tool in rehabilitation and biomechanical fields of research. We have proposed image processing as a new method to record and determine the frequency response of human body. The arranged set up for forced vibration consisted of an AC motor, a variable speed drive unit and a shaking table for producing one directional sinusoidal vibration. Volunteers were asked to stand on the shaking table at a relaxed posture. Two digital camcorders were used to capture the motion of colored pencil-dot markers on the skin of human body (forehead) and on the edge of the shaking table. After color spotting each frame, the binary image results were processed using new circle factor criteria proposed in this work, for fast finding circles based on second order statistics. The extracted points were calibrated using our own extended version of the direct linear transformation (DLT) method. Subsequently Vibration measuring software has been completely developed in Borland Delphi 5.0. Finally obtained displacement function of the body and the shaking table has been used in conjunction with Matlab 6.5 to prepare a proper algorithm for analyzing human body vibration. We discussed mechanical characteristics of the body by obtaining mechanical impedance and transmissibility from the shaking table to the head as example applications of the conducted software. The important point is the fact that all devices used in our developed measurement system are usually available in a biomechanics laboratory where a Gait system is functioning. This gives the opportunity for such laboratory to add vibration measurement to its capabilities without much excessive costs. The system has the advantage of lower noise sensitivity in comparison to accelerometer. The main advantage of this method is working with a simple user-familiar hardware with no external device attached to the subject and also a user-friendly-software.