# Frequently Asked Questions

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This page contains links to the Frequently Asked Questions (FAQ) database. Most FAQ entries have been created base on questions asked as part of Caltech CDS 101/110. If you are a registered user, you can also add a FAQ.

## FAQs by Chapter

- FAQ: Can we get more information about state space formulation?
- FAQ: How can I go from a continuous linear ODE to a discrete representation?
- FAQ: How can we tell from the phase plots if the system is oscillating?
- FAQ: How do we learn how to translate MATLAB equations into the Simulink diagrams?
- FAQ: How do you know when your model is sufficiently complex?
- FAQ: In Exercise 2.10, what do the variables phi represent?
- FAQ: In the predator prey example, where is the fox birth rate term?
- FAQ: What is a state? How does one determine what is a state and what is not?
- FAQ: What is a stochastic system?
- FAQ: What is closed form?
- FAQ: What is the advantage of having a model?
- FAQ: Why does the effective service rate f(x) go to zero when x = 0 in Example 2.10 on queuing systems?
- FAQ: Why is the parameter "a" in the predator-prey problem used as both death of rabbit and birth of foxes?
- FAQ: Why isn't there a term for the rabbit death rate besides being killed by the foxes?

- FAQ: In the predator prey example, where is the fox birth rate term?
- FAQ: In the two compartment model, what does q0 represent?
- FAQ: What are the parameters for the Whipple bicycle model?
- FAQ: Why do the two terms for the rate of change of the congestion control window size in equation (3.16) have different units?
- FAQ: Why isn't there a term for the rabbit death rate besides being killed by the foxes?

- FAQ: Does a stable system have a stable equilibrium point? a limit cycle?
- FAQ: How do we choose epsilon in the definition of stability?
- FAQ: How do you plot a 3D phase portrait?
- FAQ: If every equilibrium point can be transformed to the origin and then analyzed using a Lyapunov function, how can a system have both stable and unstable equilibrium points?
- FAQ: What do the double vertical bars mean at the end of Section 4.1?
- FAQ: Who is Lyapunov?

- FAQ: Are the percentages in the definition of rise time, overshoot measured from the final value, or the size of the input change?
- FAQ: How do you show that exp(T S inv(T)) = T exp(S) inv(T)?
- FAQ: In Example 5.3, why is the A matrix in the given form?
- FAQ: What is an example of a system with Re(λ)=0 that is not stable? What if Im(λ) is not zero?
- FAQ: What is steady state error?

**Chapter 8 - Transfer Functions**

**Chapter 9 - Frequency Domain Analysis**

**Chapter 11 - Frequency Domain Design**

**Chapter 12 - Robust Performance**