Table 3.

The average and standard deviation of RMS errors for the system with maximum muscle strength variations in degrees and percentile error. Each muscle maximum strength decreases randomly with uniform distribution between 25% and 75% and a total of 50 random trials were tested for each of four different total activation level in (a) type I control and (b) type n control. The reference trajectories are pseudo-random signals in Fig. 6-(b). The results show that the effect of the maximum muscle strength change on the output tracking error is not significant indicating the robustness of the proposed control

Angles	Total activation level
	0.25	0.50	0.75	1.00
Type I control
Ankle joint (before change)	1.2 (2.4%)	0.9 (1.8%)	0.7 (1.4%)	0.5 (1.4%)
Ankle joint (after change)	1.6 ± 0.3 (3.2%)	1.4 ± 0.2 (2.8%)	1.1 ± 0.2 (2.2%)	0.9 ± 0.3 (1.8%)
Subtalar joint (before change)	0.8 (2.0%)	0.7 (1.8%)	0.7 (1.8%)	0.6 (1.5%)
Subtalar joint (after change)	1.1 ± 0.3 (2.8%)	1.0 ± 0.2 (2.8%)	1.0 ± 0.2 (2.5%)	1.0 ± 0.2 (2.5%)
Type II control
Ankle joint (before change)	0.8 (1.6%)	0.7 (1.4%)	0.6 (1.2%)	0.5 (1.0%)
Ankle joint (after change)	1.1 ± 0.1 (2.2%)	1.0 ± 0.1 (2.0%)	0.9 ± 0.1 (1.8%)	0.8 ± 0.1 (1.6%)
Subtalar joint (before change)	0.6 (1.5%)	0.5 (1.3%)	0.5 (1.3%)	0.5 (0.5%)
Subtalar joint (after change)	0.9 ± 0.2 (2.3%)	0.8 ± 0.1 (2.0%)	0.8 ± 0.2 (2.0%)	0.9 ± 0.2 (2.3%)