A television/computer system for human locomotion analysis
The literature review, Chapter One , is in three parts. The first part concerns the development of locmotion analysis, placing particular emphasis on the methods of measurment used. The second part is a review of kinematic measurement systems in which the attributes and limitations of each method are fully discussed. The final part of the review describes other television/computer systems that have been used or developed for locomotion measurement and discusses the limitations of these systems. Chapter Two discusses methods of detecting the spatial position of body segments using a television camera and justifies the use of a passive marker system to indicate anatomical landmarks. A suitable material for markers and its response is described. Methods of identifying the signals produced by the markers in the camera video output are suggested, and the circuits for the marker detectors used are presented. The principles of operation of a television/computer interface designed to generate the spatial co-ordinates of markers are descrlbed in Chapter Three. A simple scheme to obtain these co-ordinates is first of all presented and the limitations of this method are shown and used to justify the development of a more complex digitaI system. A description is presented of the functional elements of this system, which generates the co-ordinates of markers detected in the video signals from up to six television cameras. The basic principles of television referred to in this chapter will be found in Appendix A1; similarly those aspects of the PDP 12 computer system which directly concern the interface are described in Appendix A2. Chapter Four presents the logic of the interface in the form of a description and a set of logic drawings. The nomenclature used to describe the logic is first of all discussed and then a detailed description with the aid of timing diagrams and tables is presented for each drawing. Computer programming of the interface is described in Chapter Five. The instruction set created to control the interface is listed, and two programming examples are provided to show how the instruction set may be used. A method of decoding the interface data, to relate the co-ordinates to the camera which generated them, is also presented. A summary of the computer software written and listed in Appendix A3 is given. Chapter Six describes how the system was tested in all aspects of its design and in its suitability for human locomotion measurerment. Errors and methods of calibrating the data are discussed. The co-ordinates generated by the interface for the trajectories of markers placed on a walking subject are presented and a means of identifying markers from co-ordinate data is described. Some modifications to the basic design are suggested to give improved performance. The performance of the system is summarised and comparisons are made with other methods. Clinical and other applications of the system are discussed and recommendations for future work are given.