Estimated frequency response and coherence functions of the closed-loop system ( H
). From top: magnitude, phase and coherence functions of the EMG- (blue), force- (green) and joystick-based (red) control interfaces, all as function of frequency. The solid lines indicate the mean values and the area in faded colors indicate ±1 SD. The vertical lines in the magnitude plot indicate the mean estimated gain margin crossover frequencies of each interface.