Generalized sensitivity decoupling for dual-stage servo systems

In this paper, we present a new method for designing a dual-stage compensator. Sensitivity decoupling, decoupling the output sensitivity into the product of two sensitivities, is used as the starting point. This paper extends the idea of sensitivity decoupling so that optimization methods can be used to adjust the closed loop responses of the system while maintaining a pre-specified output sensitivity function. The set of all sensitivity decoupling controllers is derived by using the Youla parameterization and this set is used to formulate an optimization problem to shape the closed loop response of the system. A design example shows how decoupling can be maintained while changing the other system responses.