Vivek Raju, MathWorks
Learn how to design a digital PID controller for a DC-DC converter. As the simulation model contains high-frequency switching and thus cannot be linearized, the transfer function is obtained by using system identification on measured input-output data. The transfer function is then used by the PID Tuner app from Simulink Control Design™ to automatically compute PID gains. PID controller design is verified in nonlinear simulation.
The example starts with a controller that has not been tuned. Simulation of a step response of output voltage shows that the controller does not provide desired response time. To tune the controller, PID Tuner app is used. The example shows how to open the feedback loop and inject a step signal into the plant. The simulation results are then collected and used for system identification to identify a transfer function of the converter at the current operating condition.
Once the transfer function has been obtained, PID Tuner automatically computes PID Controller gains to meet bandwidth and phase margin requirements. The computed gains are used to update the gains of PID Controller block in the Simulink® model. The full nonlinear simulation is used to verify the improved controller performance that meets response time requirements.
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