dan chena b c d e - decigo · 2020. 2. 4. · concept of design test mass module ×2 capacitive...
TRANSCRIPT
1. Abstract
Dan ChenA, Tomotada AkutsuB, Masaki AndoC , Shuichi SatoD, Seiji KawamuraE , Masa-Katsu FujimotoA B,DPF WG
Department of Astronomy, Univ. of TokyoA, National Astronomical Obsevatory of JapanB, Kyoto Univ.C, Housei Univ.D, Institute for Cosmic Ray Research, Univ. of TokyoE
4. Control of Test Mass with Capacitive sensors and Electrostatic actuators
2. DECIGO Pathfinder (DPF)
2012/05/21-25 LISA Symposium @Paris
1V 2V
3V4V
1V 2V
3V4V
4.2 Experiment system
3.Control
X
θ
X
θ
d1 d2
d3 d4
F F
V(d2-d1)
V(d4-d3)
Matrix
xV
V
*30
0
*30
0
*30
0
*30
0
Differen
tial C
urren
t circuit
F.P. cavity
~
V
5. Conclusion
We have controlled the translational and yaw motions of a suspended test mass which is the same size as a test mass of DPF. We could suppress the fluctuation of the test mass under 0.1Hz.
4.3 Two DOFs control
We could suppress two DOFs fluctuations of the test mass
via our feedback control system.
Test Mass (50mm squares)
Electrodes
No
ise
Tran
sfer
Fu
nct
ion
Transitional motion (X) Yaw motion (θ)
Suppressed Suppressed
Phase margin~45 degrees
UGF~0.2Hz UGF~0.2Hz
Frequency [Hz] Frequency [Hz]
Frequency [Hz] Frequency [Hz]
Dis
pla
cem
ent
no
ise
[m/r
tHz]
An
gle
no
ise
[rad
/rtH
z]
Gai
n
Gai
n
Ph
ase
[deg
]
Ph
ase
[deg
]
The noise of the transitional motion and that of the yaw motion were suppressed in the same time period.
These transfer functions (transitional motion and yaw motion) have gains under 0.2Hz.The phase margins are approximately 45 degrees.
This article reports on the development of inertial sensors for DECIGO Pathfinder (DPF), which is the precursor of DECIGO, spaceborne gravitational-wave (GW) antenna of Japan in future. To achieve drag-free control, DPF will have micro thrusters and inertial sensors which sense external force on the satellite structure. The inertial sensor comprises a proof mass (test mass : T.M.) and position controllers which consist of capacitive sensors and electrostatic actuators. The position controller will sense the relative position between the proof mass and its housing, and control the proof mass motion with the actuator. We achieved the control of translational motion and yaw motion. We will report on the feedback.
Purpose Technology demonstration for DECIGO Gravitational‐wave detection (0.1‐1Hz) Earth gravity monitoring
Main Interferometer
Test Mass
Test Mass
Concept of design Test mass module ×2
Capacitive sensors Electrostatic actuators
Capacitive sensor T.M. Electrostatic actuator
Thruster Satellite
Filter
This part is tested.
There two loops: Signal from capacitive sensors will 1. feed back to T.M. with electrostatic actuators. 2. feed back to Satellite with thrusters. We will report the loop which feed back to T.M.
~
V +++
+++
- -
- -
+ +
+ +
- -
- -
- -
- -
C1
C2 electrostatic induction
+ +
+ +
ー
ー
ー
ー
ー
ー
Differential current
C1 C2
C3 C4
V1 V2
V3 V4
Te
st Ma
ss
1V 2V
3V4V
1V 2V
3V4V
4.1 Principle
Capacitive sensor
Electrostatic actuator
We can sense the displacement of the T.M. as the difference of the capacitance.
We can actuate the T.M.’s DOFs by charging the electric filed around the T.M.
Lo
ck in
Phase margin~45 degrees