Section 3 demonstrated how the step

Section 3 demonstrated how the step response of the magnetic coupling can rapidly deteriorate from the ideal optimized linear response as the input approaches 100%. Utilizing a linearized model of the nonlinear characteristics is valid at, or close to, the chosen operating point. This section proposes a nonlinear control approach that will provide a uniform step response over the entire input range, i.e., 0% to 100%. This implies that the error surface of Fig.7 must be a zero flat plane for any input within the specified range of the input. This can be achieved with feedback linearization, an entirely different technique to conventional linearization via system approximation[28]. The objective of feedback linearization is to determine both a nonlinear control law and a nonlinear state transformation that produces an exact linearization, from input-output of the nonlinear system. However, the analysis is restricted by two important considerations: 1) No account is taken of external load-side torque disturbances, this essentially restricts the nonlinear model to single input single output (SISO). 2) The condition of pole-slipping[27] is not considered, restricting the magnetic coupling to be within the principal mechanical displacement angle range −30◦ < θD < 30◦.