Adapting Semi-Active Prostheses to Real-World Movements: Sensing and Controlling the Dynamic Mean Ankle Moment Arm with a Variable-Stiffness Foot on Ramps and Stairs

. 2021 Sep 8;21(18):6009. doi: 10.3390/s21186009

DMAMA	Dynamic mean ankle moment arm
DOF	Degrees of freedom
DR	Down ramp
DS	Down stairs
$D M A M A_{a d j u s t e d}$	DMAMA value adjusted for random effect
$D M A M A_{a v e r a g e}$	Average adjusted DMAMA value
$D M A M A_{p r e d i c t e d}$	DMAMA value predicted by linear mixed-effects model
${\vec{F}}_{s a g i t t a l}$	Force in sagittal plane
${\bar{F}}_{s a g i t t a l}$	Magnitude of mean force in sagittal plane
${\vec{F}}_{x}$	Force in x-direction
${\vec{F}}_{y}$	Force in y-direction
${\vec{F}}_{z}$	Force in z-direction
GRF	Ground reaction force
IMU	Inertial measurement unit
$I$	Magnitude of ground reaction force impulse
$J$	Magnitude of ankle moment impulse
LC	Load cell
LDA	Linear discriminant analysis
LG	Level ground
${\vec{M}}_{a n k l e}$	Ankle moment
${\vec{M}}_{k n e e}$	Knee moment
${\vec{M}}_{s a g i t t a l}$	Moment in sagittal plane
${\bar{M}}_{s a g i t t a l}$	Mean ankle moment in sagittal plane
${\vec{M}}_{x}$	Moment in x-direction
${\vec{M}}_{y}$	Moment in y-direction
${\vec{M}}_{z}$	Moment in z-direction
${\vec{r}}_{L C}^{}$	Vector from joint center to center of load cell
${\bar{R}}_{L C}^{S h a n k}$	Rotation matrix from load cell coordinate system to shank coordinate system
$R S S$	Residual sum of squares
$T S S$	Total sum of squares
UR	Up ramp
US	Up stairs
VSF	Variable-stiffness foot