Feedforward Control Process NMBU Dec 2017 April 2018

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Explore the course on Feedforward Control by Finn Aakre Haugen, focusing on faster disturbance compensation and setpoint tracking. Learn about implementing feedforward controllers in temperature and level control systems with the help of simulators.

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Course: Process Control, NMBU Dec 2017 - April 2018 Feedforward Control By Finn Aakre Haugen, PhD, TechTeach (finnhaugen@hotmail.com) F. Haugen. Process Control. NMBU. 2018. 1

Why? Faster disturbance compensation and/or Faster setpoint tracking (important only with time-varying setpoint) How? Connecting disturbance measurement signal directly to the actuator (the control signal) What is needed? Measurement of disturbance(s) and Process knowledge in the form of some mathematical model F. Haugen. Process Control. NMBU. 2018. 2

Control system with both feedforward and feedback: Controller Feedforward controller function Sensor for disturbance d Disturbance dm Ff Sd Natural coupling uff Technical coupling yr e ufb y u PID Process controller Sp Feedback Sensor for process output F. Haugen. Process Control. NMBU. 2018. 3

Example 1: Feedforward control in a temperature control system (We will run a simulator of this example.) F. Haugen. Process Control. NMBU. 2018. 4

Example 1 cont.: How to derive the feedforward controller: (1) Process modelling: Energy balance: (2) The feedforward controller is obtained by solving for the control variable, and substituting the process variable by its setpoint: Can it be implemented? Find out by inspecting the right-hand side! All terms must have known values. Which sensors are needed? 5 F. Haugen. Process Control. NMBU. 2018.

Example 1 cont.: Simulator: Feedforward control in temperature control system F. Haugen. Process Control. NMBU. 2018. 6

Example 2: Feedforward in level control system Simulator Let's derive the feedforward controller (it is quite easy). 7 Skala: LTLine brukerforum, 9.1.18: Minikurs i regtek. F. Haugen.

8 Experimental feedforward F. Haugen. Process Control. NMBU. 2018. 8

9 Structure of control system: dm Disturbance Feedforward control function: Sd d Sensor for disturbance Experimental relation between dm and uf Table lookup uff yr e ufb y u PID Process controller Sp Feedback F. Haugen. Process Control. NMBU. 2018. 9

10 Relation between disturbance measurement and steady-state control signal (with PID controller): Feedback control signal to be used as feedforward control signal, uff u6 u5 u4 u3 Piecewise linear interpolation u2 u1 d1 d2 d3 d4 d5 d6 d Measured disturbance F. Haugen. Process Control. NMBU. 2018. 10

11 Example: Temperature control Temperature sensor 2 Air pipe PWM indicator Pulse Width Modulator (PWM) AC/DC converter Electrical heater Pt100/ milliampere transducer Temperature sensor 1 Fan PC with LabVIEW Air Mains cable (220/110 V) On/Off switch USB cable Fan speed adjustment 3 x Voltage AI (Temp 1, Temp 2, Fan indication) 1 x Voltage AO (Heating) NI USB-6008 for analog I/O F. Haugen. Process Control. NMBU. 2018. 11