phd-simscape-nass/simscape-nass.org

Simscape Model - Nano Active Stabilization System

• Introduction
• Control Kinematics
  • Introduction
  • Micro Station Kinematics
  • Computation of the sample's pose error
  • Position error in the frame of the nano-hexapod
• Decentralized Active Damping
  • Introduction
  • IFF Plant
  • Controller Design
  • Sensitivity to disturbances
• Centralized Active Vibration Control
  • Introduction
  • HAC Plant
  • Effect of Payload mass
  • Controller design
  • Sensitivity to disturbances
  • Tomography experiment
• Conclusion
• Bibliography

Introduction   ignore

From last sections:

• Uniaxial: No stiff nano-hexapod (should also demonstrate that here)
• Rotating: No soft nano-hexapod, Decentralized IFF can be used robustly by adding parallel stiffness

In this section:

• Take the model of the nano-hexapod with stiffness 1um/N
• Apply decentralized IFF
• Apply HAC-LAC
• Check robustness to payload change
• Simulation of experiments

Control Kinematics

<<sec:nass_kinematics>>

Introduction   ignore

• Explain how the position error can be expressed in the frame of the nano-hexapod
• positioning_error: Explain how the NASS control is made (computation of the wanted position, measurement of the sample position, computation of the errors)
• Control architecture, block diagram
• Schematic with micro-station + nass + metrology + control system
• Zoom in the control system with blocs
• Then explain all the blocs
• Say that there are many control strategies. It will be the topic of chapter 2.3. Here, we start with something simple: control in the frame of the struts

Micro Station Kinematics

• from ref:ssec:ustation_kinematics, computation of the wanted sample pose from the setpoint of each stage.

Computation of the sample's pose error

From metrology (here supposed to be perfect 6-DoF), compute the sample's pose error. Has to invert the homogeneous transformation.

Position error in the frame of the nano-hexapod

Explain how to compute the errors in the frame of the struts (rotating)

Decentralized Active Damping

<<sec:nass_active_damping>>

Introduction   ignore

• How to apply/optimize IFF on an hexapod? ()
• Robustness to payload mass
• Root Locus
• Damping optimization
• [ ]control_active_damping
• [ ]active damping for stewart platforms
• [ ]Vibration Control and Active Damping

IFF Plant

%% Identify the plant dynamics using the Simscape model

% Initialize each Simscape model elements
initializeGround();
initializeGranite();
initializeTy();
initializeRy();
initializeRz();
initializeMicroHexapod();
initializeSimplifiedNanoHexapod();
initializeSample('type', 'cylindrical');

initializeSimscapeConfiguration('gravity', false);
initializeDisturbances('enable', false);
initializeLoggingConfiguration('log', 'none');
initializeController('type', 'open-loop');
initializeReferences();

% Input/Output definition
% clear io; io_i = 1;
% io(io_i) = linio([mdl, '/Controller'],     1, 'openinput');             io_i = io_i + 1; % Actuator Inputs [V]
% io(io_i) = linio([mdl, '/Micro-Station'],  3, 'openoutput', [], 'Vs');  io_i = io_i + 1; % Force Sensors voltages [V]
% io(io_i) = linio([mdl, '/Tracking Error'], 1, 'openoutput', [], 'EdL'); io_i = io_i + 1; % Position Errors [m]

% % With no payload
% Gm = exp(-1e-4*s)*linearize(mdl, io);
% Gm.InputName  = {'u1', 'u2', 'u3', 'u4', 'u5', 'u6'};
% Gm.OutputName = {'Vs1', 'Vs2', 'Vs3', 'Vs4', 'Vs5', 'Vs6', ...
%                  'eL1', 'eL2', 'eL3', 'eL4', 'eL5', 'eL6'};

• Show how it changes with the payload mass (1, 25, 50)
• Effect of rotation (1rpm, 60rpm)

Controller Design

• Apply IFF
• Show Root Locus
• Choose optimal gain. Here in MIMO, cannot have optimal damping for all modes. (there is a paper that tries to optimize that)
• Show robustness to change of payload (loci?)
• Reference to paper showing stability in MIMO for decentralized IFF

Sensitivity to disturbances

• Compute transfer functions from spindle vertical error to sample vertical error with IFF (and compare without the NASS)
• Same for horizontal
• Maybe noise budgeting, but may be complex in MIMO…

Centralized Active Vibration Control

<<sec:nass_hac>>

Introduction   ignore

• uncertainty_experiment: Effect of experimental conditions on the plant (payload mass, Ry position, Rz position, Rz velocity, etc…)
• Effect of micro-station compliance
• Effect of IFF
• Effect of payload mass
• Decoupled plant
• Controller design

From control kinematics:

• Talk about issue of not estimating Rz from external metrology? (maybe could be nice to discuss that during the experiments!)
• Show what happens is Rz is not estimated (for instance supposed equaled to zero => increased coupling)

HAC Plant

• Compute transfer function from u to dL (with IFF applied)

Effect of Payload mass

• Show effect of payload mass + rotation

Controller design

• Show robustness with Loci

Sensitivity to disturbances

• Compute transfer functions from spindle vertical error to sample vertical error with HAC-IFF Compare without the NASS, and with just IFF
• Same for horizontal
• Maybe noise budgeting, but may be complex in MIMO…

Tomography experiment

• With HAC-IFF, perform tomography experiment, and compare with open-loop
• Take into account disturbances, metrology sensor noise. Maybe say here that we don't take in account other noise sources as they will be optimized latter (detail design phase)
• Tomography + lateral scans (same as what was done in open loop here)
• Validation of concept

Conclusion

<<sec:nass_conclusion>>

Bibliography   ignore