Estimation of ground reaction forces and ankle moment with multiple, low-cost sensors

Table 3 Fit metrics for the ankle moment estimation

Multi-task, Intra-day	Calf raise		Walking 1.0 m/s		Walking 1.5 m/s
ankle joint torque	RMSE	NRMSE	RMSE	NRMSE	RMSE	NRMSE
features	(% BWL)	(%)	(% BWL)	(%)	(% BWL)	(%)
Angle	3.42	53.06	2.56	15.83	3.01	16.42
Tendon	3.01	46.02	3.33	20.47	4.34	23.54
Angle+Tendon	3.35	51.77	2.34	14.46	2.94	16.03
Insole	1.04	16.52	1.39	8.72	1.70	9.21
Insole+Tendon	0.90	13.78	1.17	7.42	1.30	7.04
Angle+Insole	0.98	15.57	1.27	8.04	1.36	7.29
Angle+Insole+Tendon	0.91	13.78	1.17	7.51	1.27	6.85

Root mean squared error (RMSE) and normalized root mean squared error (NRMSE) for the right ankle moment for the calf raise, walking at 1.0 m/s, and walking at 1.5 m/s trials. The angle and tendon sensors individually have low accuracy (NRMSE > 10 %) in all three tasks. The insole sensor has high accuracy for the walking tasks but not for the calf raise tasks. Combining redundant measurements from the insole sensor and the tendon sensor improves accuracy on all three tasks. Units: Body Weight * Leg Length (BWL)

ISSN: 1743-0003