Design of semi active knee joint orthosis with magnetorheological (MR) damper

In this thesis, an electromechanical design of a knee orthosis in which a custom designed magnetorheological (MR) cylinder is used as a damper is presented. Subsequently, gait phase detection algorithm and related control procedures were also developed for an embedded system. In details, the design includes an electronic card with a microcontroller that collects data from the sensors, performs the phase detection and controls the knee orthosis accordingly. A current source is designed and verified for the desired current levels to activate MR damper during control stages. Its performance is compared with an industrial product available in the market. In the first phase of this study, the MR damper specially designed for this study is allowed to move freely and the operation examined without control appliance. It is verified that the phase detection algorithms operating in real time on the microcontroller of the knee orthosis perform as expected. In the final stage of the thesis, the MR damper and knee orthosis are used under control algorithm along with gait phases estimated real time by the microcontroller, and the obtained results are discussed. As a part of the thesis, motion analysis systems which are aimed to be used during the knee joint orthosis design are also investigated and an appropriate system is arranged in the laboratory. This motion analysis system is used as a verification mechanism for the collected data, and as a reference platform in the gait phase detection studies. The system collects data from healthy subjects through the passive skeleton system over which gait phase detection studies are also performed. As the obtained results are examined, it is seen that even though the success rate of phase detection evaluations are measured just on the passive skeleton system using filtered knee joint angle, the correctness of some phase detections may reach up to 95% and the average success rate is around 68%. On the other hand, the studies resulted in 76% of success rate for the phase detection evaluations which are performed only for filtered shin angle. The average success rate of the phase detection evaluations performed using knee joint orthosis is recorded as 93% when the MR damper is in relaxed mode and left uncontrolled. However, when the MR damper is controlled through proper current levels, the average success rate went up to 88%.