Fast calibration for parameters of an inertial measurement unit fixed to a standard walker

A system consisting of an inertial measurement unit (IMU) mounted on a walker is proposed. The objective of this system is to monitor a user's walking. The relationship between the walker and the IMU, which cannot be easily measured manually, plays an important role in the system. There are various relationships because of the different types of walkers, as well as adjustments made to the height of the walker legs for comfortable usage. In this study, we propose a simple procedure for fast calibration, which consists of the attitude and the position of the IMU with respect to the walker coordinate system. The procedure includes slightly tilting the walker to the front, back, right, and left. A Kalman filter based on the inertial navigation system is used to estimate the trajectory of the IMU during tilting movements. The relationship can be calibrated using the estimated trajectory and geometric characteristics of walkers. The results of the experiments show that the proposed method achieves acceptable accuracy (97% of distance and position) and convenience.