Measurements
Table of Contents
1 Experimental conditions
Date | 2018-01-12 |
Sensors | Geophones |
Excitation | Instrumented Hammer |
Location | Laboratory |
Notes | Unglued Granite |
- The granite is not glued to the floor
- FS = 512Hz
- Made by Marc Lesourd on the 12 of January 2018
Goal: Obtain better coherence at low frequency.
2 Measurements procedure
Geophones L-28LB geophones (table 1) are placed on
- Marle
- Tilt Stage
- Top of Hexapod
Natural Frequency [Hz] | 4.5 |
Weight [g] | 140 |
Sensitivity [V/(m/s)] | 31.3 |
The structure is excited using an instrumented hammer with impacts on
- Marble X-Y-Z
- Hexapod X-Y-Z
3 Measurement Channels
Ch. nb | Element | Location | Direction |
---|---|---|---|
1 | Hammer | variable | |
2 | Geophone | Marble | X-Y-Z |
3 | Geophone | Tilt stage | X-Y-Z |
4 | Geophone | Top of Hexapod | X-Y-Z |
4 Experiments
Meas. nb | Location | Direction |
---|---|---|
1 | Marble | X |
2 | Hexapod | X |
3 | Marble | Y |
4 | Hexapod | Y |
5 | Marble | Z |
6 | Hexapod | Z |
5 Data Analysis
5.1 Loading and pre-processing of the data
The Geophone sensitivity is defined below:
w0 = 4.5*2*pi; % [rad/s] ksi = 0.38; G0 = 31.3; % [V/(m/s)] G = G0*(s/w0)^2/((s/w0)^2 + 2*ksi*(s/w0) + 1); % [V/(m/s)]
We then:
- load the data
- add a minus sign when needed
- integrate the signal to have displacement instead of velocity
- scaled with the sensitivity of the Geophone
load('./raw_data/freq_frf.mat') % freq_frf w = j*2*pi*freq_frf; % j.omega in [rad/s] scaling = squeeze(freqresp(G, 2*pi*freq_frf))/G0; load('./raw_data/frf_marble_x.mat') % ReIm1 frf_marble_x = zeros(size(ReIm1, 1), 3); frf_marble_x(:, 1) = -ReIm1(:, 2)./w./scaling; % marble_x frf_marble_x(:, 2) = -ReIm1(:, 3)./w./scaling; % tilt_x frf_marble_x(:, 3) = -ReIm1(:, 4)./w./scaling; % hexa_x load('./raw_data/frf_hexa_x.mat') % ReIm2 frf_hexa_x = zeros(size(ReIm2, 1), 3); frf_hexa_x(:, 1) = -ReIm2(:, 2)./w./scaling; % marble_x frf_hexa_x(:, 2) = -ReIm2(:, 3)./w./scaling; % tilt_x frf_hexa_x(:, 3) = -ReIm2(:, 4)./w./scaling; % hexa_x load('./raw_data/frf_marble_y.mat') % ReIm3 frf_marble_y = zeros(size(ReIm3, 1), 3); frf_marble_y(:, 1) = -ReIm3(:, 2)./w./scaling; % marble_y frf_marble_y(:, 2) = -ReIm3(:, 3)./w./scaling; % tilt_y frf_marble_y(:, 3) = -ReIm3(:, 4)./w./scaling; % hexa_y load('./raw_data/frf_hexa_y.mat') % ReIm4 frf_hexa_y = zeros(size(ReIm4, 1), 3); frf_hexa_y(:, 1) = ReIm4(:, 2)./w./scaling; % marble_y frf_hexa_y(:, 2) = ReIm4(:, 3)./w./scaling; % tilt_y frf_hexa_y(:, 3) = ReIm4(:, 4)./w./scaling; % hexa_y load('./raw_data/frf_marble_z.mat') % ReIm5 frf_marble_z = zeros(size(ReIm5, 1), 3); frf_marble_z(:, 1) = ReIm5(:, 2)./w./scaling; % marble_z frf_marble_z(:, 2) = ReIm5(:, 3)./w./scaling; % tilt_z frf_marble_z(:, 3) = ReIm5(:, 4)./w./scaling; % hexa_z load('./raw_data/frf_hexa_z.mat') % ReIm6 frf_hexa_z = zeros(size(ReIm6, 1), 3); frf_hexa_z(:, 1) = ReIm6(:, 2)./w./scaling; % marble_z frf_hexa_z(:, 2) = ReIm6(:, 3)./w./scaling; % tilt_z frf_hexa_z(:, 3) = ReIm6(:, 4)./w./scaling; % hexa_z
load('./raw_data/coher_marble_x.mat') % coh1 coh_marble_x = zeros(size(coh1, 1), 3); coh_marble_x(:, 1) = coh1(:, 2); % marble_x coh_marble_x(:, 2) = coh1(:, 3); % tilt_x coh_marble_x(:, 3) = coh1(:, 4); % hexa_x load('./raw_data/coher_hexa_x.mat') % coh2 coh_hexa_x = zeros(size(coh2, 1), 3); coh_hexa_x(:, 1) = coh2(:, 2); % marble_x coh_hexa_x(:, 2) = coh2(:, 3); % tilt_x coh_hexa_x(:, 3) = coh2(:, 4); % hexa_x load('./raw_data/coher_marble_y.mat') % coh3 coh_marble_y = zeros(size(coh3, 1), 3); coh_marble_y(:, 1) = coh3(:, 2); % marble_y coh_marble_y(:, 2) = coh3(:, 3); % tilt_y coh_marble_y(:, 3) = coh3(:, 4); % hexa_y load('./raw_data/coher_hexa_y.mat') % coh4 coh_hexa_y = zeros(size(coh4, 1), 3); coh_hexa_y(:, 1) = coh4(:, 2); % marble_y coh_hexa_y(:, 2) = coh4(:, 3); % tilt_y coh_hexa_y(:, 3) = coh4(:, 4); % hexa_y load('./raw_data/coher_marble_z.mat') % coh5 coh_marble_z = zeros(size(coh5, 1), 3); coh_marble_z(:, 1) = coh5(:, 2); % marble_z coh_marble_z(:, 2) = coh5(:, 3); % tilt_z coh_marble_z(:, 3) = coh5(:, 4); % hexa_z load('./raw_data/coher_hexa_z.mat') % coh6 coh_hexa_z = zeros(size(coh6, 1), 3); coh_hexa_z(:, 1) = coh6(:, 2); % marble_z coh_hexa_z(:, 2) = coh6(:, 3); % tilt_z coh_hexa_z(:, 3) = coh6(:, 4); % hexa_z
5.2 X-direction FRF
Figure 1: Response to a force applied on the marble in the X direction
Figure 2: Response to a force applied on the hexa in the X direction
5.3 Y-direction FRF
Figure 3: Response to a force applied on the marble in the Y direction
Figure 4: Response to a force applied on the hexa in the Y direction
5.4 Z-direction FRF
Figure 5: Response to a force applied on the marble in the Z direction
Figure 6: Response to a force applied on the hexa in the Z direction
5.5 Save the processed data
Finally, we save the processed data.
save('./data/id31_microstation_2018_01_12_frf.mat', ... 'freq_frf', ... 'frf_marble_x', ... 'frf_marble_y', ... 'frf_marble_z', ... 'frf_hexa_x', ... 'frf_hexa_y', ... 'frf_hexa_z'); save('./data/id31_microstation_2018_01_12_coh.mat', ... 'freq_frf', ... 'coh_marble_x', ... 'coh_marble_y', ... 'coh_marble_z', ... 'coh_hexa_x', ... 'coh_hexa_y', ... 'coh_hexa_z');
6 Results
- Resonances at 42Hz, 70Hz and 125Hz have been identified
- The coherence is much better than when using accelerometers