Timeline for Closed loop response of a discrete system
Current License: CC BY-SA 3.0
9 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Apr 14, 2016 at 14:31 | vote | accept | Somanna Thapanda | ||
| Apr 14, 2016 at 14:31 | vote | accept | Somanna Thapanda | ||
| Apr 14, 2016 at 14:31 | |||||
| Apr 14, 2016 at 13:30 | answer | added | Suba Thomas | timeline score: 2 | |
| Apr 14, 2016 at 13:29 | comment | added | Suba Thomas | I did the calculations using Mathematica. Things work as expected. As I initially suspected, there is something wrong with your calculations. You can now compare your results with mine. | |
| Apr 14, 2016 at 8:52 | comment | added | Somanna Thapanda | i checked the closed loop poles and open loop poles. Both are stable but to my surprise I can observe from nyquist that it is not stable. From time domain analysis, the system is stable. For a given step response the system is stable with good steady state and transient response. Here is the plant model, $\frac{4700 s^2 + 4393 s + 3.245e08}{ s^4 + 7.574 s^3 + 1.202e05 s^2}$ and the controller is $Ctrl = pid(0.287, 0.5, 0.008)$. I am not sure what is going wrong. Can you please help me sort it out. | |
| Apr 13, 2016 at 14:39 | comment | added | Suba Thomas | If 'zoh', 'foh', and 'matched' are giving an unstable approximation of a stable system there is something wrong in what you are doing. Did you look at the poles of the continuous-time and discrete-time systems. | |
| Apr 13, 2016 at 14:33 | comment | added | Somanna Thapanda | Do you mean using zoh or foh methods while transforming from continuous to discrete? I did include. | |
| Apr 13, 2016 at 13:48 | comment | added | Suba Thomas | With zero-order hold it should be stable. Did you check the closed-loop poles? What if you use the first-order hold or zero-pole mapping methods? | |
| Apr 13, 2016 at 12:34 | history | asked | Somanna Thapanda | CC BY-SA 3.0 |