A non-linear tunable PI block for improvement of closed-loop control response

Fuzzy logic has been used to create nonlinear transfer functions for one or more input variables. For example, an input variable e and its derivative delta e may be used in conjunction with rules and membership functions to create a non-linear PD controller. Integrating the result yields a non-linear fuzzy PI controller. Under the assumption that monotonic behavior is needed for a stable control, the nonlinear PI may be implemented much simpler and more predictable with algebraic equations. This technique allows to adjust the gain of the P and the I portions separately while maintaining conventional stable conditions.