Fig. 2
From: Physiological and kinematic effects of a soft exosuit on arm movements
Admittance controller for transparency and gravity compensation. An outer torque loop (orange) tracks a reference profile equal and opposite to gravity, computing a motion reference as an interaction torque is sensed, according to the admittance specified by a PID controller. The inner velocity loop (light blue) is tuned to be as stiff as possible, to reject force disturbances like stiction and backlash. The green arrow indicates a positive feedback path, introduced to improve transparency