Muscle Synergy and Musculoskeletal Model-Based Continuous Multi-Dimensional Estimation of Wrist and Hand Motions

Figure 6

2D wrist joint angle estimation in 5 different trials. Angle X corresponds to flexion-extension dimension taking extension as positive. Angle Y corresponds to radial-ulnar deviation having radial deviation as positive. The blue-colored line represents the IMU-reference angle derived from two IMU sensors by differentiating relative orientation in the Euler angle. The red-colored estimate is a musculoskeletal model- (MSM-) based estimation having 5 input signals. Yellow-colored estimate stands for synergy-based linear regression model- (SLRM-) based estimation deriving synergy derived separately per trial. An example of (a) a comfortable maximum limit trial, (b) half of a comfortable maximum trial, (c) a stiffened movement trial, (d) a grip-trial having twelve times gripping, and (e) combined movement of a comfortable maximum limit with grip.