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- [ ] [[file:~/Cloud/work-projects/ID31-NASS/matlab/nass-simscape/org/nano_hexapod.org][nano_hexapod]] (it seems this report is already after the detailed design phase: yes but some parts could be interesting)
- [ ] Look at the [[file:~/Cloud/work-projects/ID31-NASS/documents/state-of-thesis-2020/index.org][NASS 2020 report]]
Sections 5.1, 5.4
- [ ] [[file:~/Cloud/work-projects/ID31-NASS/matlab/nass-simscape/org/amplified_piezoelectric_stack.org][amplified_piezoelectric_stack]] (Just use 2DoF here)
- [ ] [[file:~/Cloud/work-projects/ID31-NASS/matlab/nass-simscape/org/nano_hexapod.org][nano_hexapod]] (it seems this report is already after the detailed design phase: yes but some parts could be interesting)
- [ ] Should the study of effect of flexible joints be included here?
Maybe no sections, just a review discussing several aspect of the platforms.
1. Review of active vibration platforms (focused on Synchrotron applications)
2. Serial and Parallel Architecture: advantages and disadvantages of both
3. Which architecture => Parallel manipulator? Why *Stewart platform*?
*2 - The Stewart Platform*:
Introduction: some history about Stewart platform and why it is so used
1. Architecture (plates, struts, joints)
2. Kinematics and Jacobian
4. Static Analysis
5. Dynamic Analysis: very complex => multi-body model
For instance, compute the plant for massless struts and perfect joints (will be compared with Simscape model).
But say that if we want to model more complex cases, it becomes impractical (cite papers).
*3 - Multi-Body model of the Stewart platform*:
Introduction: Complex dynamics => analytical formulas can be complex => Choose to study the dynamics using a multi-body model
1. Model definition: (Matlab Toolbox), frames, inertias of parts, stiffnesses, struts, etc...
2. Joints: perfect 2dof/3dof (+ mass-less)
3. Actuators: APA + Encoder (mass-less)
4. Nano-Hexapod: definition of each part + Plant with defined inputs/outputs (force sensor, relative displacement sensor, etc...)
Compare with analytical formulas (see number of states)
*4 - Control of the Stewart Platform*:
Introduction: MIMO control => much more complex than SISO control because of interaction. Possible to ignore interaction when good decoupling (important to have tools to study interaction)
1. Centralized and Decentralized Control
2. Decoupling Control / Choice of control space file:~/Cloud/research/matlab/decoupling-strategies/svd-control.org
Estimate coupling: RGA
- Jacobian matrices, CoK, CoM, control in the frame of the struts, ...
- Discussion of cubic architecture (quick, as it is going to be in detailed in chapter 2)
- SVD, Modal, ...
3. Active Damping: decentralized IFF
Guaranteed stability?
For decentralized control: "MIMO root locus"
How to optimize the added damping to all modes?
4. HAC-LAC
Stability of closed-loop: Nyquist (main advantage: possible to do with experimental FRF)
*Conclusion*:
- Configurable Stewart platform model
- Will be included in the multi-body model of the micro-station => nass multi body model
** DONE [#A] Location of this report in the complete thesis
CLOSED: [2025-02-05 Wed 16:04]
*Before the report* (assumptions):
- Uniaxial model: no stiff actuator, HAC-LAC strategy
- Rotating model:
Soft actuators are problematic due to gyroscopic effects
Use moderately stiff (1um/N).
IFF can be applied with APA architecture
- Model of Micro-station is ready
*In this report*:
- Goal: build a flexible (i.e. configurable) multi-body model of a Stewart platform that will be used in the next section to perform dynamical analysis and simulate experiments with the complete NASS
- Here, I propose to work with "perfect" stewart platforms:
- almost mass-less struts
- joints with zero stiffness in free DoFs (i.e. 2-DoF and 3-DoF joints)
- Presentation of Stewart platforms (Literature review about stewart platforms will be done in chapter 2)
- Presentation of the Simscape model
*After the report* (NASS-Simscape):
- nano-hexapod on top of micro-station
- control is performed
- simulations => validation of the concept
** TODO [#C] First time in the report that we speak about MIMO control ? Or maybe next section!
Maybe should introduce:
- "MIMO" Root locus
- "MIMO" Nyquist plot / characteristic loci
Or should this be in annexes?
Maybe say that in this phd-thesis, the focus is not on the control.
I tried multiple architectures (complementary filters, etc.), but the focus is not on that.
** QUES [#C] Cubic architecture should be the topic here or in the detailed design?
I suppose that it should be in the detailed design phase.
(Review about Stewart platform design should be made in Chapter two.)
Here, just use simple control architecture for general validation (and not optimization).
** QUES [#C] Should I make a review of control strategies?
Yes it seems to good location for review related to control.
Jacobian matrix.
Control is the frame of the struts, in the cartesian frame (CoM, CoK), modal control, etc...
- Talk about flexible joint? Maybe not so much as it should be topic of second chapter.
Just say that we must of flexible joints that can be defined as 3 to 6DoF joints, and it will be optimize in chapter 2.
- [[cite:&taghirad13_paral]]
- For some systems, just XYZ control (stack stages), example: holler
- For other systems, Stewart platform (ID16a), piezo based
- Examples of Stewart platforms for general vibration control, some with Piezo, other with Voice coil. IFF, ...
Show different geometry configuration
- DCM: tripod?
** Active vibration control of sample stages
[[file:~/Cloud/work-projects/ID31-NASS/phd-thesis-chapters/A0-nass-introduction/nass-introduction.org::*Review of stages with online metrology for Synchrotrons][Review of stages with online metrology for Synchrotrons]]
- [ ] Talk about external metrology?
- [ ] Talk about control architecture?
- [ ] Comparison with the micro-station / NASS
** Serial and Parallel Manipulators
*Goal*:
- Explain why a parallel manipulator is here preferred
- Compact, 6DoF, higher control bandwidth, linear, simpler
- Show some example of serial and parallel manipulators
- A review of Stewart platform will be given in Chapter related to the detailed design of the Nano-Hexapod
- linked to the sensor position relative to the actuators
- linked to the fact that sensors and actuators pairs are "independent" or each other (related to the control architecture, not because there is no coupling)
- When can decentralized control be used and when centralized control is necessary?
- Jacobian matrices, CoK, CoM, control in the frame of the struts, SVD, Modal, ...
- Combined CoM and CoK => Discussion of cubic architecture ? (quick, as it is going to be in detailed in chapter 2)
- Explain also the link with the setpoint: it is interesting to have the controller in the frame of the performance variables
Also speak about disturbances? (and how disturbances can be mixed to different outputs due to control and interaction)
- Table that summarizes the trade-off for each strategy
- Say that in this study, we will do the control in the frame of the struts for simplicity (even though control in the cartesian frame was also tested)
For decentralized control: "MIMO root locus" can be used to estimate the damping / optimal gain
Poles and converging towards /transmission zeros/
How to optimize the added damping to all modes?
- [ ] Add some papers citations
Compute:
- [ ] Plant dynamics
- [ ] Root Locus
** MIMO High-Authority Control - Low-Authority Control
<<ssec:nhexa_control_hac_lac>>
Compute:
- [ ] compare open-loop and damped plant (outputs are the encoders)
- [ ] Implement decentralized control?
- [ ] Check stability:
- Characteristic Loci: Eigenvalues of $G(j\omega)$ plotted in the complex plane
- Generalized Nyquist Criterion: If $G(s)$ has $p_0$ unstable poles, then the closed-loop system with return ratio $kG(s)$ is stable if and only if the characteristic loci of $kG(s)$, taken together, encircle the point $-1$, $p_0$ times anti-clockwise, assuming there are no hidden modes
- [ ] Show some performance metric? For instance compliance?
