What is the idea behind input design?
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.
What is the goal behind experiment design?
“To maximize the information content in the data subject to
practical constraints.“
What are the two types of input design?
- Single input design
- Multiple Input design
What are examples of single input?
- Impulse
- Frequency sweeps
- Doublet
- 3211 and 211
- Multisines
What is standard practice for sampling rate?
To do sampling much higher than theoretical minimum rate
What is a six step experiment design technique?
- Start with a full factorial or a fractional design
- Conduct experiments
- Estimate model
- Test model accuracy
- Add additional terms and data points
- Iterate
What are error increases with too many variables and too few variables?
Variance with too many
Bias with too few
What is forward selection for model determination?
Forward Selection starts with the easiest model and successively adds regressors until adding does not significantly improve the fit anymore
What is backward elimination for model determination?
Backward Elimination starts with an over parameterized model and successively deletes regressors, until a significant degradation would result
What is Stepwise regression?
Combination of forward and backward steps
What are two basic principles of Input design?
- 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.
What is an impulse input?
- Shape is a simple spike or sudden bump
- Best suited for prediction cases
- Has power in wideband but low amplitude
What are frequency sweeps?
- The shape of the input is a continuous sinusoid with the frequency increasing in time
What are Doublets?
Doublet inputs are two-sided pulse.
What are 3211 and 211 inputs?
- Common for aircraft design
- Consists of alternating pulses with widths in the ratio 3-2-1-1
What are multisines?
Multisine is a sum of sinusoids with various frequencies, amplitudes, and phase angles.
What is Aliasing?
Aliasing arises when a signal is discretely sampled at a rate that is insufficient to capture the changes in the signal.
What is hypothesis testing?
Hypothesis Testing tests the significance of each regressor’s contribution in the model structure
