cascaded multiloop feedback design -凯发k8网页登录

decoupling loops in multiloop systems

the typical design procedure for cascaded feedback systems is to first design the inner loop and then the outer loop. in control system designer, it is possible to design both loops simultaneously; by default, when designing a multi-loop feedback system the coupling effects between loops are taken into account. however, when designing two feedback loops simultaneously, it can be necessary decouple the feedback loops; that is, remove the effect of the outer loop when tuning the inner loop. in this example, you design the inner feedback loop (q) with the effect of the outer loop (az) removed.

configure control system designer

to design a controller using control system designer, you must:

for this example, you can:

to open control system designer, in the simulink model, in the apps gallery, click control system designer.

in the edit architecture dialog box, on the blocks tab, click add blocks. in the select blocks to tune dialog box, select the following blocks, and click ok.

on the signals tab, the analysis points defined in the simulink model are automatically added as locations.

to use the selected blocks and signals, click ok.

in control system designer, in the data browser on the, the responses section contains the following open-loop responses, which control system designer automatically recognizes as potential feedback loops for open-loop design.

open graphical bode editors for each of the following responses. in control system designer, select tuning methods > bode editor. then, in the select response to edit dialog box, in the select response to plot drop-down list, select the corresponding open-loop responses, and click plot.

to view the closed-loop response of the feedback system, create a step plot for a new input-output transfer function response. select new plot > new step. then, in the new step dialog box, in the select response to plot drop-down list, select new input-output transfer response.

add scdairframectrl/step az/1 as an input signal and scdairframectrl/airframe model/1 as an output signal.

click plot.

remove effect of outer feedback loop

in the outer-loop bode editor plot, bode editor for looptransfer_scdairframectrl_az_control_az_dtf, increase the gain of the feedback loop by dragging the magnitude response upward. the inner-loop bode editor plot, bode editor for looptransfer_scdairframectrl_q_control_q_gain, also changes. this change is a result of the coupling between the feedback loops. a more systematic approach is to first design the inner feedback loop, with the outer loop open.

to remove the effect of the outer loop when designing the inner loop, add a loop opening to the open-loop response of the inner loop.

in the data browser, in the responses area, right-click the inner loop response, and select open selection.

in the open-loop transfer function dialog box, specify scdairframectrl/az control/az dtf/1 as the loop opening. click ok.

in the outer-loop bode editor plot, increase the gain by dragging the magnitude response. since the loops are decoupled, the inner-loop bode editor plot does not change.

you can now complete the design of the inner loop without the effect of the outer loop and simultaneously design the outer loop while taking the effect of the inner loop into account.

tune compensators

control system designer contains several methods tuning a control system:

complete design

the following compensator parameters satisfy the design requirements:

      k_q = 2.7717622

      k_az = 0.00027507

      numerator = [100.109745 -99.109745]
      denominator = [1 -0.88893]

the response of the closed-loop system is shown in the following figure.

update simulink model

to write the compensator parameters back to the simulink model, click update blocks. you can then test your design on the nonlinear model.