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CRY payload actuator upgrade in 2020

Project definition

Deliverables of the work

A document to answer the following questions

  1. Does the expected actuator and sensor noise level satisfy the KAGRA requirement ?
  2. Can we lock the interferometer with the modified actuators ?
    1. Is lock acquisition possible ? (ignore noise)
    2. Can we keep the lock with weak damping ? i.e., not injecting excess control noise from strong damping
  3. Can we damp all the resonant modes of the CRY payload within reasonable time (like 1 minutes) ?

Methods

  • Create a combined model of SUMCON and Simulink for the Type-A suspension.
    • The model includes a LTI version of suspension mechanical model and feedback loops around it.
  • Copy the current control topology into the baseline model
  • Try to reproduce the current behavior of the suspensions (validation)
  • Update the baseline model to the modified CRY payload
  • Optimize the control topology and filters to find a configuration which allows us to control the suspension without saturating the actuators and not injecting excess noise to DARM

Assignment

  • Create a baseline model: Shoda, Ushiba, Miyo
  • Optimization of the control topology and filters: Ushiba, Yamada, Nakano, Shoda, Miyo, Terrence
  • Give advice from the viewpoint of interferometer: Nakano, Michimura

Deadlines

  • End-of-June: Create a base model
  • End-of-July: Make a recommendation for the CRY payload modification


Kick-off meeting

2020/5/27 10:30 - 12:00 Zoom: KAGRA Zoom2

Minutes

  • The main work of this project is to create a simulation model of the suspension including the control loops, then optimize the control topology.
  • We also identified additional tasks related to this project

Simulation of the Type-A suspension to find optimum control strategy

  • We will create a model (SUMCON + Simulink) to simulate the current Type-A suspension, called the baseline model.
  • Using the baseline model, we will try to reproduce the current suspension behavior:
    • Close the local damping loops with the current control topology and filteres
    • Inject known noises, such as sensor noise, actuator noise, seismic noise, green laser noise.
    • Check the actuator loads (saturated or not) and find out what is limiting the current performance.
  • After validating the baseline model, update it to the modified actuators and sensors
  • Optimize the control topology and filters to find a configuration which allows us to control the suspension without saturating the actuators and not injecting excess noise to DARM

Additional tasks

Largest magnet possible ?
  • It is relatively easy to modify the coil drivers, but not easy to change magnets in the vacuum.
  • Therefore, it may be better to install magnets as large as possible into the suspensions
  • We need to identify what is the limit, and is there any drawback from this.
  • Will start email discussion on this.

Actuator efficiency of the currently installed actuators
  • Measure the in-situ actuation efficiency and compare it with the theoretical predictions or ex-situ measurements using scales
  • We can probably take the measurements by CAL of the actuation efficiency, which is in the unit of m/V, then convert it into N/A using the suspension mechanical model.

Seismic noise coupling of the PF actuator
  • Coils for the new PF actuators will be mounted on the ground.
  • We need to estimate the seismic motion coupling of this actuator.
  • Measurement of the coupling using a scale will be necessary
  • Probably an action item for CRY


Meeting Materials

Current status and plan of CRY payload by Ushiba

Slides

Goal of the meeting

Decide the followings

Deliverables of the work

A document to answer the following questions

  1. Does the expected actuator noise level satisfy the KAGRA requirement ?
  2. Can we lock the interferometer with the modified actuators ?
    1. Is lock acquisition possible ? (ignore noise)
    2. Can we keep the lock with weak damping ? i.e., not injecting excess control noise from strong damping
  3. Can we damp all the resonant modes of the CRY payload within reasonable time (like 1 minutes) ?

Methods

  • Create a SUMCON model of modified CRY payload
  • Implement local damping loops on simulation
    • Check the damping efficiency of resonant modes
  • Implement a hierarchical control scheme on simulation
    • Check the controllability of the suspension
    • How can you evaluate the feasibility of lock acquisition ?

Assignment

  • Create a SUMCON model: Shoda, Ushiba, Miyo
  • Damping and hierarchical control: Ushiba, Yamada, Nakano, Shoda, Miyo, Terrence
  • Set requirements from IFO: Nakano, Michimura

Deadline

  • Mid-June: intermediate report on the progress at a meeting
  • End-of-June: final report (too aggressive ?)

KAGRA/Upgrades/PostO3Upgrades/CRYActuators (last edited 2020-05-27 14:27:01 by YoichiAso)