Series solution approach for designing the approximate input-output linearization controller

A new approach to an approximate input-output (I/O) linearization controller for nonlinear processes that exhibit non-minimum phase behavior is presented. The I/O feedback controller is formulated in the form of the series solution. The Taylor series method is applied to truncate the time derivatives of outputs around the steady state pair corresponding to the desired set-point. The reduced-order state observer is used to estimate the unmeasured process states. The series solution of the feedback controller is more applicable to implement into the digital control hardware that has limitations on the memory and instruction capability. To illustrate the control performance, the proposed method is applied to an example of a continuous stirred tank reactor (CSTR) that exhibits non-minimum phase behavior. The simulation results show that the controller can force the output to the desired set-point asymptotically.