Table 2.

The average and standard deviation of RMS errors for the sinusoidal reference trajectories with four different phase difference between ankle and subtalar joint reference trajectories: 0°, 90°, 180° and 270°. The magnitude of the reference trajectory is the same as the one in Fig. 7. As the frequency component of the reference trajectory increases, the output tracking error increases too

Frequency (Hz)	Total activation level
	0.25	0.50	0.75	1.00
Ankle joint with type I control
0.5	1.5 ± 0.5 (3.0%)	1.5 ± 0.3 (3.0%)	0.9 ± 0.2 (1.8%)	0.8 ± 0.2 (1.6%)
1.0	3.8 ± 1.2 (7.6%)	3.6 ± 1.4 (7.2%)	3.2 ± 0.9 (6.4%)	3.0 ± 0.3 (6.0%)
1.5	8.2 ± 1.5 (16.4%)	7.4 ± 3.0 (14.8%)	6.0 ± 1.2 (12.0%)	6.1 ± 1.4 (12.2%)
Subtalar joint with type I control
0.5	1.2 ± 0.4 (3.0%)	0.7 ± 0.1 (1.8%)	0.8 ± 0.4 (2.0%)	0.7 ± 0.3 (1.8%)
1.0	2.2 ± 0.6 (5.5%)	1.4 ± 0.1 (3.5%)	2.1 ± 0.9 (5.3%)	1.9 ± 0.5 (4.8%)
1.5	4.1 ± 0.8 (10.3%)	2.9 ± 0.9 (7.3%)	3.6 ± 1.3 (9.0%)	3.2 ± 1.2 (8.0%)
Ankle joint with type II control
0.5	1.0 ± 0.1 (2.0%)	1.2 ± 0.3 (2.4%)	0.8 ± 0.1 (1.6%)	0.8 ± 0.1 (1.6%)
1.0	2.0 ± 0.3 (4.0%)	2.6 ± 0.5 (5.2%)	2.2 ± 0.5 (4.4%)	2.5 ± 0.3 (5.0%)
1.5	5.8 ± 0.5 (11.6%)	5.4 ± 1.1 (10.8%)	5.3 ± 0.3 (10.6%)	5.2 ± 0.3 (10.4%)
Subtalar joint with type II control
0.5	1.0 ± 0.2 (2.5%)	0.8 ± 0.1 (2.0%)	0.7 ± 0.2 (1.8%)	0.6 ±0.1 (1.5%)
1.0	2.0 ± 0.3 (5.0%)	1.7 ± 0.3 (4.3%)	1.6 ± 0.2 (4.0%)	1.5 ± 0.5 (3.8%)
1.5	4.1 ± 0.5 (10.3%)	3.8 ± 0.8 (9.5%)	3.4 ± 0.6 (8.5%)	3.3 ± 0.9 (8.3%)