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Control Systems in Practice, Part 3: What is Feedforward Control?

A control system has two main goals: get the system to track a setpoint, and reject disturbances. Feedback control is pretty powerful for this, but this video shows how feedforward control can make achieving those goals easier. Temperature Control in a Heat Exchange Example: The error in a feedback control system is the summation of three different error sources: setpoint changes, disturbances into the system, and noise within the system. Feedforward can be used to remove a lot of the setpoint and disturbance error before it ever gets to the controller. In this way, the feedback controller can be tuned to correct for the small modeling errors in the feedforward path while still ignoring the higher-frequency noise in the system. In some systems, this combined feedforward/feedback architecture is a better system than feedback on its own. After watching this video, you’ll have a better understanding of what feedforward control is and why it is used. If you would like to practice the concepts from this video, this is a good tutorial that covers designing a feedforward system to control temperature in a heat exchanger.

Part 1 - What Control Systems Engineers Do Part 2 - What is Gain Scheduling? Part 4 - Why Time Delay Matters
Part 5 - A Better Way to Think About a Notch Filter

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