1. A method for non-linear (fractional dynamics) modeling of physiological behavior measured by an implantable device, comprising the steps of: measuring the physiological behavior; determining magnitude of deviation between the measured physiological behavior and a reference value y ref ; modeling dynamics of the measured physiological behavior with continuous time fractional differential equations to identify parameters of a non-linear fractal model; selecting a constrained fractal optimal control problem; deriving optimality conditions for the constrained fractal optimal control problem when the magnitude of deviation exceeds a predetermined threshold; discretizing the optimality conditions for the constrained fractal optimal control problem; and solving the constrained fractal optimal control problem corresponding to the optimality conditions to identify an optimal physiological behavior to operate the implantable device.