1 / 21

Behavior of an inverted pendulum in the Kamioka mine

Behavior of an inverted pendulum in the Kamioka mine. R. Takahashi (NAOJ), A. Takamori (ERI), E. Majorana (INFN). We are investigating behavior of an inverted pendulum ( IP ) in the Kamioka mine where is the site of LCGT.

reina
Download Presentation

Behavior of an inverted pendulum in the Kamioka mine

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Behavior of an inverted pendulum in the Kamioka mine R. Takahashi(NAOJ), A. Takamori (ERI), E. Majorana (INFN) We are investigating behavior of an inverted pendulum (IP) in the Kamioka mine where is the site of LCGT. IP is employed as pre-isolator of the seismic attenuation system (SAS) for LCGT. GWADW2010

  2. Seismic Attenuation System (SAS) for LCGT IP 2

  3. Contents Unsealed IP with a geophone Setup of apparatus Geophone Results Ground tilt Sealed IP with a small accelerometer Setup of apparatus Accelerometer Results Vertical ground vibration Summary

  4. 1. Unsealed IP with a geophone Aug. 19-20, 2009 @CLIO site One-leg IP Geophones (Horizontal2, Vertical 2)

  5. 1-a. Setup of apparatus 1. Unsealed IP Load (50mHz) Geophone (horizontal) Geophone (vertical) Flex joint “Roughly” enclosed to avoid air flow

  6. 1-b. Geophone 1. Unsealed IP Vertical Velocity response of 1Hz geophone(L-4C) Ground 1 Ground 2 Differential Sensitivity limit by CMR： 5x10-11m/Hz1/2 @1Hz It is possible to sense the level less than 1/10 of ground vibration in 0.2-2Hz.

  7. 1-c. Results (1) 1. Unsealed IP Ground IP Noise limit Horizontal The displacement of IP reached the sensitivity limit at 3Hz. The displacement of IP was larger than ground vibration around 0.2Hz.

  8. 1. Unsealed IP 1-c. Results (2) Ground IP 1st Q~35 IP 2nd IP 3rd settled The excess around 0.2Hz is not due to harmonics of fundamental mode. Ring down of IP unchanged What is this gap? Prediction

  9. 1. Unsealed IP 1-d. Ground tilt (1) • We supposed that the excess is due to ground tilt. • IP is very sensitive to ground tilt. IP with natural frequency of 50mHz corresponds to 100m pendulum. • Actually Virgo group pointed out ground tilt is dominant source of the IP displacement in the SA at frequencies less than 0.1Hz.

  10. 1. Unsealed IP 1-d. Ground tilt (2) The excess around 0.2Hz in IP spectrumis not due to ground tilt. The excess is due to residual air flow? Blue line： Ground tilt supposing that displacement of IP is due to ground tilt Red line： Ground tilt estimated by differential signal between two vertical geophones

  11. 2. Sealed IP with a small accelerometer Jan. 28-29 & Feb. 24-25, 2010 Small accelerometer

  12. 2-a. Setup of apparatus 2. Sealed IP 12

  13. 2. Sealed IP 2-b. Accelerometer (1) 65mm f0=1.98Hz Q=20 60mm Folded pendulum MakerUFT Material A7075 Size 60 x 30 x 65 Hinge 20mm A servo type accelerometer consist of this pendulum and a position sensor.

  14. 2. Sealed IP 2-b. Accelerometer (2) Commercial photo sensor

  15. 2. Sealed IP Ground IP Ground IP Ground IP 2-c. Results Natural frequency of IP was tuned to 70mHz. Notch at 2Hz is due to the resonance of the folded pendulum. Prediction (Q=69) Though measured displacement was close to sensitivity limit, displacement of IP was still larger than ground vibration around 0.2Hz.

  16. 2. Sealed IP 2-d. Vertical ground motion Sensitive zone for both sensor Vertical ground vibration had not correlation with IP displacement. IP resonance is excited by vertical vibration? (out of sensitive zone)

  17. 3. Summary We investigated behavior of an IP in the Kamioka mine. The displacement of IP was larger than ground vibration around 0.2Hz. The excess is not harmonics of fundamental mode of the IP. The excess is not due to ground tilt. The excess is not due to vertical vibration directly. Though we could not specify the origin, it might be non-linear vertical coupling. We need more investigations.

  18. Long term stability 2/24 16:22 – 2/25 7:53 IP was stable without glitch for 15.5 hours.

  19. IP tilt meter Since 70mHz IP corresponds to 50m pendulum. Ground tilt→Displacement of IP→Tilt of accelerometer→DC signal of accelerometer The drift of ~0.5mrad was observed for 15.5 hours. The application of IP to tilt meter may be useful.

  20. Measured transfer function of IP Measured isolation ratio of the SAS prototype (IP was tuned to 220mHz.) Measured transfer function from force to displacement of the SAS in TAMA

  21. Displacement of IP in TAMA • Controlled by LVDT with different band width • Measured by ACC Broad band: following the ground motion Narrow band: free at > natural frequency (~0.05Hz) IP motion > ground motion at 0.16Hz

More Related