Synergy-Based Sensor Reduction for Recording the Whole Hand Kinematics

Abstract

Simultaneous measurement of the kinematics of all hand segments is cumbersome due to sensor placement constraints, occlusions, and environmental disturbances. The aim of this study is to reduce the number of sensors required by using kinematic synergies, which are considered the basic building blocks underlying hand motions. Synergies were identified from the public KIN-MUS UJI database (22 subjects, 26 representative daily activities). Ten synergies per subject were extracted as the principal components explaining at least 95% of the total variance of the angles recorded across all tasks. The 220 resulting synergies were clustered, and candidate angles for estimating the remaining angles were obtained from these groups. Different combinations of candidates were tested and the one providing the lowest error was selected, its goodness being evaluated against kinematic data from another dataset (KINE-ADL BE-UJI). Consequently, the original 16 joint angles were reduced to eight: carpometacarpal flexion and abduction of thumb, metacarpophalangeal and interphalangeal flexion of thumb, proximal interphalangeal flexion of index and ring fingers, metacarpophalangeal flexion of ring finger, and palmar arch. Average estimation errors across joints were below 10% of the range of motion of each joint angle for all the activities. Across activities, errors ranged between 3.1% and 16.8%.

Comparison and Improvement of CyberGlove III Calibration Methods

“…We did not investigate the wrist sensors and the palm arch has shown to be difficult to calibrate. Even though the findings in this work need to be confirmed for arthritis patients as well, it already shows that using the CyberGlove III for objective hand monitoring of healthy subjects is feasible, supporting previous findings ( [2], [6], [8], [11], [12], [22]). Furthermore, the CyberGlove III was already used to discriminate between healthy individual and patients suffering from osteoarthritis with an accuracy of 80 % [8].…”

“…Additionally, the concept of an across-subject calibration [11] is considered, as it reduces the number of measurements required for the calibration with each person, making it suitable for large clinical studies or even regular clinical routine. Another approach worth mentioning is the concept of dimensionality reduction, i. e., kinematic synergies that establish a relation between joint angles [22]. This approach has to be used with care, as it deduces all joint angles by measuring only reduced number after kinematic synergies were found.…”

Using Sensorized Gloves and Dimensional Reduction for Hand Function Assessment of Patients with Osteoarthritis

“…The errors in estimating the hand joint angles from the measurement of only five joint angles (flexion and abduction of thumb carpometacarpal joint, flexion of metacarpophalangeal joint of the middle finger and proximal interphalangeal joint of the ring finger, and abduction between ring and little fingers) are small (7.0° ± 2.7°). The errors found are of the same order of magnitude as the errors from the recording technique [ 40 ]. Despite being only a preliminary exploration, the results obtained suggest the feasibility of acquiring entire hand kinematics from the recording of only a few angles.…”

“…Despite being only a preliminary exploration, the results obtained suggest the feasibility of acquiring entire hand kinematics from the recording of only a few angles. Further studies are required to make it clear whether the proposed angles are the most suitable ones or if more sophisticated methods for looking for the most appropriate ones [ 40 ] would be needed. Searching for indicators of kinematic dysfunction based only on the recordings of these few angles would, therefore, be interesting.…”

“…Furthermore, the observed kinematic synergies could also be applied to reconstruct entire hand kinematics from the recording of only a few joint angles by estimating the remaining angles from the coordination established by those synergies. This has already been proven to be feasible in healthy subjects [ 40 ] but needs to be studied in patients. Lowering the number of hand joints to be recorded would reduce the investment required.…”