Chapter 7

Question 1

What is the idea behind input design?

Answer 1

To excite the dynamic system in a way that the data contain sufficient information for accurate modeling, subject to the practical constraints of the experiment.

Question 2

What is the goal behind experiment design?

Answer 2

“To maximize the information content in the data subject to
practical constraints.“

Question 3

What are the two types of input design?

Answer 3

• Single input design
• Multiple Input design

Question 4

What are examples of single input?

Answer 4

• Impulse
• Frequency sweeps
• Doublet
• 3211 and 211
• Multisines

Question 5

What is standard practice for sampling rate?

Answer 5

To do sampling much higher than theoretical minimum rate

Question 6

What is a six step experiment design technique?

Answer 6

1. Start with a full factorial or a fractional design
2. Conduct experiments
3. Estimate model
4. Test model accuracy
5. Add additional terms and data points
6. Iterate

Question 7

What are error increases with too many variables and too few variables?

Answer 7

Variance with too many

Bias with too few

Question 8

What is forward selection for model determination?

Answer 8

Forward Selection starts with the easiest model and successively adds regressors until adding does not significantly improve the fit anymore

Question 9

What is backward elimination for model determination?

Answer 9

Backward Elimination starts with an over parameterized model and successively deletes regressors, until a significant degradation would result

Question 10

What is Stepwise regression?

Answer 10

Combination of forward and backward steps

Question 11

What are two basic principles of Input design?

Answer 11

• Inputs must be designed such that they significantly excite a range of frequencies around the Eigen modes which are to be modeled.
• Independent input on every control is necessary.

Question 12

What is an impulse input?

Answer 12

• Shape is a simple spike or sudden bump
• Best suited for prediction cases
• Has power in wideband but low amplitude

Question 13

What are frequency sweeps?

Answer 13

• The shape of the input is a continuous sinusoid with the frequency increasing in time

Question 14

What are Doublets?

Answer 14

Doublet inputs are two-sided pulse.

Question 15

What are 3211 and 211 inputs?

Answer 15

• Common for aircraft design
• Consists of alternating pulses with widths in the ratio 3-2-1-1

Question 16

What are multisines?

Answer 16

Multisine is a sum of sinusoids with various frequencies, amplitudes, and phase angles.

Question 17

What is Aliasing?

Answer 17

Aliasing arises when a signal is discretely sampled at a rate that is insufficient to capture the changes in the signal.

Question 18

What is hypothesis testing?

Answer 18

Hypothesis Testing tests the significance of each regressor’s contribution in the model structure