Estimating Hand Kinematics in Reaching Tasks using RFID - A Preliminary Study

Impairments of the upper limbs have significant impact on patients with neuromotor disease and require physical rehabilitation to reduce their effects. A RFID (Radio Frequency IDentification) system has been adapted to the use in occupational therapy aimed at improving the performance of Activities of Daily Living (ADLs). This system could be used to drive and monitor the performance of the patient during specific exercises by computing kinematic variables leveraging on the available RF parameters. In order to ascertain the feasibility of the project, we have developed and tested a method to estimate the length of the path covered by a moving RFID antenna, representing the patient’s hand, with respect to a fixed RFID tag, representing the target to be reached. Simple rotational and translational movements of the RFID antenna were performed and recorded with a movement analysis system. Simultaneously, the RSSI and phase signals were acquired from the RFID system. The phase variations were used to compute the variations of the antenna-tag distance and the path length. The measures obtained from the two systems were compared. The results show that the measure of the path length was reliable in translational movements when there was no relative antenna-tag angle, and in rotational movements. In case of translational movements with relative antenna-tag angle, inaccurate measurements are obtained.