Estimation of Relative Hand-Finger Orientation Using a Small IMU Configuration

Abstract

Relative orientation estimation between the hand and its fingers is important in many applications, such as virtual reality (VR), augmented reality (AR) and rehabilitation. It is still quite a big challenge to do the estimation by only exploiting inertial measurement units (IMUs) because of the integration drift that occurs in most approaches. When the hand is functionally used, there are many instances in which hand and finger tips move together, experiencing almost the same angular velocities, and in some of these cases, almost the same accelerations are measured in different 3D coordinate systems. Therefore, we hypothesize that relative orientations between the hand and the finger tips can be adequately estimated using 3D IMUs during such designated events (DEs) and in between these events. We fused this extra information from the DEs and IMU data with an extended Kalman filter (EKF). Our results show that errors in relative orientation can be smaller than five degrees if DEs are constantly present and the linear and angular movements of the whole hand are adequately rich. When the DEs are partially available in a functional water-drinking task, the orientation error is smaller than 10 degrees.

Wearable Movement Sensors for Rehabilitation: From Technology to Clinical Practice

“…Yang et al (2020) [ 9 ] developed a sensor-based method to estimate relative 3D orientations between finger tips and the dorsal side of the hand with inertial motion sensors but without magnetometers to avoid magnetic disturbance. The method consists of one sensor on the dorsal side of the hand, and one on the most distal finger segment.…”

Estimate Hand–Finger Position With One Magnetometer and Known Relative Orientation

“…As the strength of the magnet is much stronger than the geomagnetic field, it may cause unwanted forces if it is used near iron objects, such as iron tables or chairs. For a next step, the method to estimate relative positions using a permanent magnet and TAM, assuming known relative orientations, is to be combined with an estimate of relative orientation, as presented in our previous paper [18], in which the relative orientation was estimated based on IMUs only.…”

“…Third, the intermediate IMMUs are neglected, which makes the volume smaller and more convenient for users. The relative orientation can be estimated by only exploiting IMUs, placed on the dorsal side of the hand and the fingertips of interest, which can be found in our previous research [18] or the relative orientation can also be estimated with only IMUs if we assume finger movement as 2DOF [19], [20], such as index finger movements. The aim of this study is to investigate the possibility of estimating relative positions between the hand and several fingertips including thumb and index finger using one magnet on the hand and a single magnetometer on each fingertip of interest, assuming that their relative orientations are known.…”

A Systematic Review of Diagnostic Accuracy and Clinical Applications of Wearable Movement Sensors for Knee Joint Rehabilitation

“…Additionally, potential use cases of telemonitoring in the aging population were discussed. Sensing technology and biomedical markers are commonly used nowadays in various fields of medicine, such as stroke rehabilitation [22] or ankle joint power [23], and rehabilitation issues, such as hand-finger orientation, have already been considered [24].…”