Human walking is associated with exertion that results in muscle fatigue. This fatigue is a key parameter in determining deviation of an abnormal gait. But, accurate forces to an abnormal gait using robots can correct the muscle fatigue and the gait deviation. This active control of the ankle assisting device features a variable impedance controller. Experiments suggest variable stiffness during the stance phase and variable damping during the swing phase. Forces at all instances are determined by the user. Stability of human-robot interaction dynamics compared to constant impedance control schemes. Muscle activity at various robot control schemes are also compared with this novel scheme.