Dynamic Calibration of Force Platforms by Means of a Parallel Robot

Abstract

Force platforms are the basic equipment to measure ground reaction forces and moments in biomechanical studies. So, accurate in situ calibration of force platforms is critical for ensuring the accuracy and precision of the results of experimental studies. Although there are different avaliable approaches for in situ calibration, most of the existing methods do not use realistic and repeteable force patterns to calibrate platforms. In this paper, a new technique based on the use of a 3PRS parallel robot for applying a predefined dynamical load is proposed, where force patterns can be reproduced in a similar way as the used during actual experimental measures. This robot can be programmed to apply force patterns simulating the conditions of human gait, running or jumping. Calibration is performed by comparing the forces measured by the platform and the ones measured by a calibrated load cell. A new algorithm was developed for correcting the sensitivity coefficients, including an estimation of errors in the orientation of the load cell. This method has been validated by means of an specific experiment.