Compensator design for non-minimum phase systems

[maverick280857]

Hi

Given an open loop non-minimum phase transfer function, what in general are the approaches preferable to design a compensator for it? Suppose one is given the location of the desired closed loop poles, is it a standard practice to use complementary root locus (or negative root locus) for design, assuming a negative value of the gain?

Thanks.

 

[maverick280857]

Anyone?

 

[oswaler]

Hello,

Thank you for your question. Compensator design for non-minimum phase systems is a challenging task as these systems have complex dynamics and can exhibit unstable behavior. In general, there are several approaches that can be used to design a compensator for a non-minimum phase system. These include pole placement, input-output decoupling, and robust control techniques such as H-infinity and mu-synthesis.

If the desired closed loop poles are known, it is possible to use the complementary root locus (CRL) or negative root locus (NRL) method for designing a compensator. This method involves plotting the root locus of the open loop transfer function with a negative value of the gain, which effectively shifts the poles to the desired location in the closed loop. However, it is important to note that this method may not always result in a stable closed loop system, especially for non-minimum phase systems.

In addition to the CRL/NRL method, other techniques such as pole placement and robust control methods can also be used to design a compensator for a non-minimum phase system. These methods take into account the inherent instability of these systems and aim to achieve stability and performance requirements simultaneously.

In summary, designing a compensator for a non-minimum phase system requires careful consideration and the use of appropriate techniques. The CRL/NRL method can be used if the desired closed loop poles are known, but it is important to also consider other methods to ensure stability and performance of the closed loop system. I hope this helps answer your question.