Marker-based motion capture for measuring joint kinematics in leg swing simulator

Implementation of motion capture systems have attracted the attention of researchers in biomedical science and engineering. Motion capture system has a function to capture and record the movement of the marker placed on an object. This paper describes the marker-based motion capture for measuring joint kinematics in leg swing simulator. The forward and inverse kinematics are used for calculating and measuring leg movement in simulation. Markers are placed on three points of joint of leg. The calibrated camera captures the movement of the position of points in a Cartesian coordinates and stored in the database. Markers are detected by camera as the input where every point encodes the pose of the leg model to be measured. The simulation process is implemented in a model of a robotic leg with sagittal position which has three joint that is hip, knee and ankle. Three markers joint kinematics are estimated and compared with the calculated joint rotations. The results show the data accuracy of system with an average of hip joint estimation has average error 1.46°, knee joint has average error 1.66° and ankle joint has 0.46°.