Inertial system used to analyze normal and pathological human gait Robert Ciobanu, Octavian Dontu, Daniel Besnea, Iulian Avarvarei; Departament. of Mechatronics; University “Politehnica” of Bucharest; Bucharest, Romania; robert.ciobanu185@yahoo.com. Ionelia Voiculescu; Departament of Materials and Welding Technology; Faculty of Materials Science and Engineering, University “Politehnica” of Bucharest; Bucharest, Romania; decanat@sim.pub.ro. Abstract - Human motion analysis is one of the research directions which shows an increased interest worldwide due to the complete information we can get on human walking, normal or pathological, in order to confirm or exclude a diagnosis or to monitor patients who are receiving motor recovery program. In accordance with these new requirements a number of facilities were developed that provide information about variables, parameters and determinants of human gait allowing a complete analysis of it, but most are dependent on laboratory use, so we designed a device that can be used both laboratory and ambulatory, with a high degree of portability due to its small size and autonomy of the battery for several hours. Keywords : kinematic analyses of gait, accelerometer sensor. I. Introduction Information on the behavior of a patient with a pathological gait as speed of walking, distance, gait phases and events are important for medical diagnosis. Description, analysis and evaluation of human movement have outlined a new inter-discipline, biomechanics, with kinetic and kinematics as main sub domains, which represents a new research field of great interest for medicine and for the leading industries that aim the drafting of new materials and new technologies. The main types of equipment used in the analysis of motion kinematic characteristics are: a) electrogoniometers b) accelerometers c) ultrasound systems, d) imaging systems. Of these, imaging systems made a very thorough analysis of human gait, but are limited to laboratory use and very high priced, so we designed a portable device that provides information about basic features of human gait, recording in internal memory signals from two accelerometers in three axes, one mounted inside the central unit which is fixed at the center of gravity of the patient and one mobile that can attach to points of interest (hip, knee, ankle) depending on the patient investigated patient gait pathology. Using signals recorded from accelerometers, a more detailed analysis was attempted, making some comparative experiments to determine the characteristics of gait. II. Presentation of the suggested solution Out of the need to obtain a complete and comprehensive analysis of human gait that can be achieved both laboratory and ambulatory a small electronic device was designed with a very low power consumption, with a battery life of approximately 3 hours and an internal memory capable of storing data acquired from the two sensors that record acceleration, figure 1 in which: 1 - system of command, control and data storage, 2 - peripheral accelerometer, 3 - computer used in processing data gathered by system 1. Fig.1 Inside the system 1 a second accelerometer is installed that records the accelerations of the center of gravity for the subject monitored during the recovery program. The user interface is very simple, being formed by a conventional keyboard with 5 buttons with return and a display on which the device menu can be viewed structured in four main submenus: -acquisition - internal accelerometer; -external accelerometer; - internal + external; -transfer - data transfer home; -calibration - accelerometer calibration - internal - home; -external - home; -stand-by.