Simple frequency-dependent tools for control system analysis, structure selection and design

Al~ t rKt -The paper presents results on frequencydependent tools for analysis, structure selection and design of control systems. This includes relationships between the relative gain array (RGA) and right half plane zeros, and the use of the RGA as a sensitivity measure with respect to individual element uncertainty and diagonal input uncertainty. It is also shown how frequency-dependent plots of the closely related performance relative gains (PRGA) and a new proposed disturbance measure, the closed-loop disturbance gains (CLDG), can be used to evaluate the achievable performance (controllability) of a plant under decentralized control. These controller-independent measures give constraints on the design of the individual loops, which when satisfied guarantee that the overall system satisfies performance objectives with respect to setpoint tracking and disturbance rejection.