What is the difference between feedback control feed forward control and concurrent control?

Answer 1

1) Use ONLY feedforward control if:

• The physics/chemistry of the application are well known
• You can easily measure or calculate the variables in the equations
• There are no significant process disturbances
• The accuracy of the measurements used is an order of magnitude better than the application specifications

2) Use ONLY feedback control if:

• Significant un-modeled process disturbances exist
• You cannot measure or calculate variables in the equations describing the physics/chemistry of the application.
• The accuracy of the measurements used is NOT an order of magnitude better than the application specifications.

3) Use both when:

• The physics/chemistry of the application are well known
• You can easily measure or calculate the variables in the equations
• The accuracy of the measurements used is on the order of the application specifications
• You want to prevent saturation of the controller integrators
• You want to improve trajectory tracking, but 2nd and higher order dynamics in the plant limit your controller bandwidth

Answer 2

Feedback control involves making adjustments based on monitoring outputs and comparing them to a desired goal. Feedforward control anticipates potential issues and takes proactive measures to prevent them before they occur. Concurrent control involves monitoring activities as they happen to ensure they are on track with the overall plan or goal.