An Experimental Characterisation of Developed Knee Joint Mechanism Prototypes

The paper is focused on characterisation and experimental testing of two developed and built preliminary prototypes of human knee joint mechanisms. Mechanical systems of research prototypes, in the form of kinematic schemes and 3D CAD drawings, are designed with the aim to reproduce the knee joint’s complex movement in the assumed range and limitations. Especially the flexion/extension in sagittal plane taking into account the joint’s instantaneous centre of rotation trajectory. The first prototype is based on linearly adjustable crossed 4-bar mechanism and can modify its dimensions in real time to mimic various required motions. The second prototype uses cooperating interchangeable elements, with cam profiles, that can be adapted for individual needs. Both devices are built using 3D printed elements and characterised using results obtained from initial experiments. In order to carry out the tests an experimental layout is planned and arranged in a laboratory. Testing in couple modes was performed, but in this paper particular emphasis is placed on trials executed with human volunteers. The mechanisms’ movements are measured by IMU sensors, but mainly are elaborated by analysing video recordings and tracking colour markers. Postprocessing is performed with Matlab resulting in obtaining the outcomes, as plots and numerical values. These are presented as movement trajectories of selected tibia points and calculated knee joint’s flexion/extension angle to characterise the prototypes’ capabilities.