Typical example of the working principle of the impedance-shaping algorithm in a stroke survivor. Graph A demonstrates how the stiffness shapes from a constant stiffness of 1200 N/m to a personal stiffness profile after around 30 steps for stroke survivor A3. Note that the step-height VMC is only active during the double stance, with the non-paretic leg in front, and the paretic swing phase (approximately 50–100 percent of the gait cycle), and that the stiffness has a lower limit of 0. Graph B shows the course of the deviation from the reference pattern over multiple steps. The black area shows the error before the controller is switched on.