Objectives

• Design a feedforward controller integrated with a feedback (PID) controller for a dynamic process.

• Evaluate and compare the performance of feedback-only vs. combined feedforward-feedback control strategies for setpoint tracking and disturbance rejection.

• Implement the control strategies in MATLAB Simulink using the PID Tuner and the idealized feedforward design method.

Process information

The process and disturbance dynamics are described by the following transfer functions:

$$\begin{array}{}\text{(1)}& \begin{array}{rl}\text{ Process: }{G}_p(s)& =\frac{10\exp (-2s)}{(10s+1)(1.5s+1)}\\ \text{ Disturbance: }{G}_d(s)& =\frac{-8\exp (-3s)}{20s+1}\end{array}\end{array}$$

To simplify controller design, the process second order model can be approximated using Skogestad’s half-rule (Skogestad 2003):

$$\begin{array}{}\text{(2)}& G(s)=\frac{K_p{e}^{-{\theta }_{p}s}}{({\tau }_{1}s+1)({\tau }_{2}s+1)}\cong \frac{K_p{e}^{-{\theta }_{e}s}}{{\tau }_{1}s+1}\end{array}$$

where ${\theta }_e={\theta }_p+{\tau }_2$, and ${\tau }_1>{\tau }_2$.

Simulation Tasks

• Develop Simulink models for:
  • Feedback-only control using a tuned PID controller.
  • Combined feedforward-feedback control using the idealized feedforward design.
• Evaluate both configurations for:
  • Setpoint tracking
  • Rejection of both input and output disturbances

Report Format

Your report (5 pages maximum) should include the following:

0. Submission Details

   Include a brief table at the beginning of the report with the following information:

   Lab Title:	Lab 01 – Feedforward Control	Student Name	ID
   Unit:	CHEN4011	Student 1	12345678
   Date:	12 August 2025	Student 2	87654321

1. Objective and Problem Statement

   • Clearly describe the purpose of combining feedforward and feedback control.
   • Briefly outline the process being controlled and its disturbance characteristics.

2. Methodology and Implementation

   • Describe how each control strategy (feedback-only and feedforward-feedback) was implemented in MATLAB Simulink.
   • Include screenshots of the Simulink models with relevant annotations.
   • Explain PID tuning and derivation of the feedforward controller.

3. Results

   • Show the system response for both control strategies under:

     • Setpoint tracking
     • Input and output disturbance rejection

   • Include well-labeled plots and relevant performance data.

4. Analysis and Discussion

   • Compare and interpret the performance of the two control strategies: feedback-only vs. combined feedforward-feedback.

   • Address the following points:

     • Does the addition of a feedforward controller improve setpoint tracking or disturbance rejection? Why?
     • How does the control system respond under ±10% process model mismatch?
     • Quantitatively assess and compare the performance (e.g., rise time, overshoot, IAE) of Feedback-only control, and feedback with idealized feedforward control

5. Conclusion

   • Summarize your key findings.
   • Reflect on the practical implications of your results.

Assessment Rubric (20 Marks Total)

No	Section	Marks	Evaluation basis
1.	Objectives & Problem	2	Clarity of problem definition; articulation of objectives
2.	Methodology and Implementation	4	Correctness and clarity of Simulink models; explanation of PID and feedforward controller
3.	Results	4	Quality, relevance, and labeling of plots; completeness of performance data
4.	Analysis and Discussion	6	Insightful interpretation; answers to robustness, performance, and design method comparisons
5.	Conclusion and Presentation	4	Coherent summary; quality of writing, formatting, and visual presentation

References

Skogestad, Sigurd. 2003. “Simple Analytic Rules for Model Reduction and PID Controller Tuning.” Journal of Process Control 13 (4): 291–309. https://doi.org/10.1016/S0959-1524(02)00062-8.