K-infinity in 'ncfsyn' command for loop shaping design procedure
14 views (last 30 days)
Show older comments
siti fadilah on 23 Jan 2013
Hi... Currently I'm trying to simulate a system that using Loop shaping design procedure as robust controller. Since this is McFarlane n Glover's, I use the command 'ncfsyn' in order to get the K.
So, I've tried the example in HELP. There is one paragraph for the HELP that I don't understand: "The closed-loop H∞-norm objective has the standard signal gain interpretation. Finally it can be shown that the controller, K∞, does not substantially affect the loop shape in frequencies where the gain of W2GW1 is either high or low, and will guarantee satisfactory stability margins in the frequency region of gain cross-over. In the regulator set-up, the final controller to be implemented is K=W1K∞W2."
MY questions: 1) What does this mean that K-inf does not substantially affect the loop shape? 2) Can we calculate K-inf? How? Please show me how.
James Whidborne on 4 May 2013
1) What does this mean that K-inf does not substantially affect the loop shape?
Not at high or low frequencies (if you have got the loop shape right, i.e. high gain at low frequencys, low gain at high frequencies). The shape will be changed near cross-over, usually by the addition of phase advance that will improve the stability margins.
2) Can we calculate K-inf? How? Please show me how.
It is returned in INFO.Ks - see the help file.
There is an interactive gui on the File Exchange that can help perform the loop-shaping (lsdptool): http://www.mathworks.co.uk/matlabcentral/fileexchange/1285-lsdptool
Control Systems Control System Toolbox Control System Design and Tuning Multiloop, Multiobjective Tuning Loop-Shaping Design
Find more on Loop-Shaping Design in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!Start Hunting!