Identification
Table of Contents
The goal here is to make an identification of the micro-station in order to compare the model with the measurements on the real micro-station.
In order to do so:
- Decide where to virtually excite the station and where to measure its motion
- Extract transfer functions from the excitation forces to the measured motion
- Compare those transfer functions with the modal analysis
For the excitation, we can choose the same excitation points as the one used for the modal test. For the measurement points, we can choose the Center of Mass of each solid body. The center of mass of each solid body is not easily defined using Simscape. Indeed, we can define the center of mass of any solid body but not of multiple solid bodies. However, one solid body is composed of multiple STEP files. One solution could be to use one STEP file for one solid body. However, the position of the center of mass can be exported using simulink and then defined on Simscape.
1 Identification of the Micro-Station
1.1 Compute the transfer functions
We first define some parameters for the identification.
The simulink file for the identification is sim_micro_station_id.slx
.
open('identification/matlab/sim_micro_station_id.slx')
%% Options for Linearized options = linearizeOptions; options.SampleTime = 0; %% Name of the Simulink File mdl = 'sim_micro_station_id';
%% Micro-Hexapod % Input/Output definition io(1) = linio([mdl, '/Micro-Station/Fm_ext'],1,'openinput'); io(2) = linio([mdl, '/Micro-Station/Fg_ext'],1,'openinput'); io(3) = linio([mdl, '/Micro-Station/Dm_inertial'],1,'output'); io(4) = linio([mdl, '/Micro-Station/Ty_inertial'],1,'output'); io(5) = linio([mdl, '/Micro-Station/Ry_inertial'],1,'output'); io(6) = linio([mdl, '/Micro-Station/Dg_inertial'],1,'output');
% Run the linearization G_ms = linearize(mdl, io, 0); % Input/Output names G_ms.InputName = {'Fmx', 'Fmy', 'Fmz',... 'Fgx', 'Fgy', 'Fgz'}; G_ms.OutputName = {'Dmx', 'Dmy', 'Dmz', ... 'Tyx', 'Tyy', 'Tyz', ... 'Ryx', 'Ryy', 'Ryz', ... 'Dgx', 'Dgy', 'Dgz'};
%% Save the obtained transfer functions save('./mat/id_micro_station.mat', 'G_ms');
1.2 Plots the transfer functions
1.3 Compare with the measurements
2 Modal Analysis of the Micro-Station
2.1 Simscape Model
open('identification/matlab/sim_micro_station_modal_analysis.slx')
%% Options for Linearized options = linearizeOptions; options.SampleTime = 0; %% Name of the Simulink File mdl = 'sim_micro_station_modal_analysis';
%% Micro-Hexapod % Input/Output definition io(1) = linio([mdl, '/Micro-Station/F_hammer'],1,'openinput'); io(2) = linio([mdl, '/Micro-Station/acc9'],1,'output'); io(3) = linio([mdl, '/Micro-Station/acc10'],1,'output'); io(4) = linio([mdl, '/Micro-Station/acc11'],1,'output'); io(5) = linio([mdl, '/Micro-Station/acc12'],1,'output');
% Run the linearization G_ms = linearize(mdl, io, 0); % Input/Output names G_ms.InputName = {'Fx', 'Fy', 'Fz'}; G_ms.OutputName = {'x9', 'y9', 'z9', ... 'x10', 'y10', 'z10', ... 'x11', 'y11', 'z11', ... 'x12', 'y12', 'z12'};
2.2 Plot Results
figure; hold on; plot(freqs, abs(squeeze(freqresp(G_ms('x9', 'Fx'), freqs, 'Hz')))); set(gca, 'XScale', 'log'); set(gca, 'YScale', 'log'); ylabel('Amplitude [m/N]'); hold off;
2.3 Compare with measurements
load('../meas/modal-analysis/mat/frf_coh_matrices.mat', 'FRFs', 'COHs', 'freqs');
dirs = {'x', 'y', 'z'}; n_acc = 9; n_dir = 1; % x, y, z n_exc = 1; % x, y, z figure; hold on; plot(freqs, abs(squeeze(FRFs(3*(n_acc-1) + n_dir, n_exc, :)))./((2*pi*freqs).^2)'); plot(freqs, abs(squeeze(freqresp(G_ms([dirs{n_dir}, num2str(n_acc)], ['F', dirs{n_dir}]), freqs, 'Hz')))); set(gca, 'XScale', 'log'); set(gca, 'YScale', 'log'); ylabel('Amplitude [m/N]'); hold off;
3 Compare with measurements at the CoM of each element
3.1 Init
initializeGround(); initializeGranite(); initializeTy(); initializeRy(); initializeRz(); initializeMicroHexapod(); initializeAxisc();
3.2 TODO Center of Mass of each solid body
[ ]
Verify that this is coherent with the simscape and with the measurements
granite bot | granite top | ty | ry | rz | hexa | |
---|---|---|---|---|---|---|
X [mm] | 45 | 52 | 0 | 0 | 0 | -4 |
Y [mm] | 144 | 258 | 14 | -5 | 0 | 6 |
Z [mm] | -1251 | -778 | -600 | -628 | -580 | -319 |
open('identification/matlab/sim_micro_station_modal_analysis_com.slx')
3.3 Simscape Model
%% Options for Linearized options = linearizeOptions; options.SampleTime = 0; %% Name of the Simulink File mdl = 'sim_micro_station_modal_analysis_com';
%% Micro-Hexapod % Input/Output definition io(1) = linio([mdl, '/Micro-Station/F_hammer'],1,'openinput'); io(2) = linio([mdl, '/Micro-Station/acc_gtop'],1,'output'); io(3) = linio([mdl, '/Micro-Station/acc_ty'],1,'output'); io(4) = linio([mdl, '/Micro-Station/acc_ry'],1,'output'); io(5) = linio([mdl, '/Micro-Station/acc_rz'],1,'output'); io(6) = linio([mdl, '/Micro-Station/acc_hexa'],1,'output');
% Run the linearization G_ms = linearize(mdl, io, 0); % Input/Output names G_ms.InputName = {'Fx', 'Fy', 'Fz'}; G_ms.OutputName = {'gtop_x', 'gtop_y', 'gtop_z', 'gtop_rx', 'gtop_ry', 'gtop_rz', ... 'ty_x', 'ty_y', 'ty_z', 'ty_rx', 'ty_ry', 'ty_rz', ... 'ry_x', 'ry_y', 'ry_z', 'ry_rx', 'ry_ry', 'ry_rz', ... 'rz_x', 'rz_y', 'rz_z', 'rz_rx', 'rz_ry', 'rz_rz', ... 'hexa_x', 'hexa_y', 'hexa_z', 'hexa_rx', 'hexa_ry', 'hexa_rz'};
3.4 Compare with measurements
load('../meas/modal-analysis/mat/frf_coh_matrices.mat', 'freqs'); load('../meas/modal-analysis/mat/frf_com.mat', 'FRFs_CoM');
dirs = {'x', 'y', 'z', 'rx', 'ry', 'rz'}; stages = {'gbot', 'gtop', 'ty', 'ry', 'rz', 'hexa'} n_stg = 2; n_dir = 5; % x, y, z, Rx, Ry, Rz n_exc = 2; % x, y, z f = logspace(0, 3, 1000); figure; hold on; plot(freqs, abs(squeeze(FRFs_CoM(6*(n_stg-1) + n_dir, n_exc, :)))./((2*pi*freqs).^2)'); plot(f, abs(squeeze(freqresp(G_ms([stages{n_stg}, '_', dirs{n_dir}], ['F', dirs{n_exc}]), f, 'Hz')))); set(gca, 'XScale', 'log'); set(gca, 'YScale', 'log'); ylabel('Amplitude [m/N]'); hold off; xlim([1, 200]);
dirs = {'x', 'y', 'z', 'rx', 'ry', 'rz'}; stages = {'gtop', 'ty', 'ry', 'rz', 'hexa'} f = logspace(1, 3, 1000); figure; for n_stg = 1:2 for n_dir = 1:3 subplot(3, 2, (n_dir-1)*2 + n_stg); title(['F ', dirs{n_dir}, ' to ', stages{n_stg}, ' ', dirs{n_dir}]); hold on; plot(freqs, abs(squeeze(FRFs_CoM(6*(n_stg) + n_dir, n_dir, :)))./((2*pi*freqs).^2)'); plot(f, abs(squeeze(freqresp(G_ms([stages{n_stg}, '_', dirs{n_dir}], ['F', dirs{n_dir}]), f, 'Hz')))); set(gca, 'XScale', 'log'); set(gca, 'YScale', 'log'); ylabel('Amplitude [m/N]'); if n_dir == 3 xlabel('Frequency [Hz]'); end hold off; xlim([10, 1000]); ylim([1e-12, 1e-6]); end end
dirs = {'x', 'y', 'z', 'rx', 'ry', 'rz'}; stages = {'ry', 'rz', 'hexa'} f = logspace(1, 3, 1000); figure; for n_stg = 1:2 for n_dir = 1:3 subplot(3, 2, (n_dir-1)*2 + n_stg); title(['F ', dirs{n_dir}, ' to ', stages{n_stg}, ' ', dirs{n_dir}]); hold on; plot(freqs, abs(squeeze(FRFs_CoM(6*(n_stg+2) + n_dir, n_dir, :)))./((2*pi*freqs).^2)'); plot(f, abs(squeeze(freqresp(G_ms([stages{n_stg}, '_', dirs{n_dir}], ['F', dirs{n_dir}]), f, 'Hz')))); set(gca, 'XScale', 'log'); set(gca, 'YScale', 'log'); ylabel('Amplitude [m/N]'); if n_dir == 3 xlabel('Frequency [Hz]'); end hold off; xlim([10, 1000]); ylim([1e-12, 1e-6]); end end
dirs = {'x', 'y', 'z', 'rx', 'ry', 'rz'}; stages = {'hexa'} f = logspace(1, 3, 1000); figure; for n_stg = 1 for n_dir = 1:3 subplot(3, 1, (n_dir-1)*2 + n_stg); title(['F ', dirs{n_dir}, ' to ', stages{n_stg}, ' ', dirs{n_dir}]); hold on; plot(freqs, abs(squeeze(FRFs_CoM(6*(n_stg+4) + n_dir, n_dir, :)))./((2*pi*freqs).^2)'); plot(f, abs(squeeze(freqresp(G_ms([stages{n_stg}, '_', dirs{n_dir}], ['F', dirs{n_dir}]), f, 'Hz')))); set(gca, 'XScale', 'log'); set(gca, 'YScale', 'log'); ylabel('Amplitude [m/N]'); if n_dir == 3 xlabel('Frequency [Hz]'); end hold off; xlim([10, 1000]); ylim([1e-12, 1e-6]); end end