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FRF measurement (non-parametric identification)

FRF measurement (non-parametric identification)

FRF measurement (non-parametric identification)

I am a control engineer, and I want to measure the Frequency Response Function (FRF) of my plant.
Basically, the plant is a motor-driven linear mechanism, ie. a linear carriage is moved by a PMDC motor through timing belt and pulley.
I understand that in practice, normally the auto- and cross- power spectrum method is used (H1, or H2)

The questions are:
1. What signal should I excite the plant (motor) input? White noise? But the motor would barely move with pure white noise
2. Should I excite the plant (motor) with only a specific speed profile (e.g trapezoidal profile)? Or should the excitation signal be (trapezoidal profile + white noise)?

Assumption is that there is no undesired noise (no measurement noise, no input noise due to surrounding, etc.)

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