A microcomputer-based gait analysis system
A microcomputer-based video vector system has been developed to display the resultant foot-ground reaction force vector on a television image of the subject in real-time. The system consists of a strain gauged force platform, 12-bit ADC, a video camera, and an Archimedes microcomputer. The output of the computer is synchronised and overlaid on the video image of the camera by a video GENLOCK board. For each television field the resultant force vector is correctly positioned relative to the image of the force platform and superimposed on the TV image at 50 times/sec. A television/computer interface has been designed to detect the position of markers using the real-time video signals. Passive optical markers are used on the subject as a means of identifying regions of interst and a glass plate/light arrangement is used to enhance reflection signals from these markers. A threshold detector extracts marker peaks from the rest of the video and digital counters determine the spatial coordinates of the markers. A hardware video window selector has been designed which is selected prior to data collection to exclude the irrelevant areas in the video field. A 16-bit input/output system has been designed dedicated to data transfer between the TV/computer interface and the Archimedes microcomputer. The system has been tested in all of its aspects to verify its ability to produce repeatable and accurate results. Some of the typical results obtained from the system are presented for both normal and pathological gait. The aim to produce a simple to use and flexible instrument was maintained throughout the design phase. The result is an instrument which can be used to record the various useful gait parameters and be a valuable tool in routine gait evaluation in the clinic.