Connecting Autotuner Block with Plant and Controller
Insert the Closed-Loop PID Autotuner block between the PID block and the plant, as
shown in the boost converter model. The start/stop signal starts and stops the closed-loop
experiment. When no experiment is running, Closed-Loop PID Autotuner block behaves
like a unity gain block, where the u signal directly passes to u+Δu.
There are a few things to be aware of when using the Closed-Loop PID Autotuner block in
both simulation and real time application:
- The plant must be either asymptotically stable (i.e. all the poles are strictly stable) or
integrating. The autotuner block does not work with an unstable plant. - The feedback loop with the existing controller must be stable.
- To estimate plant frequency responses more accurately in real time, minimize the
occurrence of any load disturbance in the plant during the experiment. The autotuner
block expects the plant output to be the response to the injected perturbation signals
only, and load disturbance distorts this output. - Because the feedback loop is closed during the experiment, the existing controller
suppresses the injected perturbation signals as well. The advantage of using closed-
loop experiment is that the controller keeps the plant running near the nominal
operating point and maintains safe operation. The disadvantage is that it reduces the
accuracy of frequency response estimation if your target bandwidth is far away from
the current bandwidth.
Configuring Autotuner Block
After properly connecting the Closed-Loop PID Autotuner block with the plant model and
PID block, use the block parameters to specify tuning and experiment settings.
There are two main tuning settings in the Tuning tab:
- Target bandwidth: Determines how fast you want the controller to respond. In this
example, choose 10000 rad/sec, which is typical for a boost converter. - Target phase margin: Determines how robust you want the controller to be. In this
example, choose the default value of 60 degrees.
Tune PID Controller in Real Time Using Closed-Loop PID Autotuner Block