EC 17; May 9 20121FADIS diplexer functionality *Operational point at output power curves
* see Kasparek, Bongers this conference
Controlled Mirror MotionFADIS system requirement
For proper operation the FADIS resonant diplexer needs to have the correct round-trip length L, despite all disturbances
DisturbancesGyrotron frequency variationsExpansion of diplexer cavity due to temperature gradientsStructural vibrations
EC 17; May 9 20122Controlled Mirror MotionDisturbances / Gyrotron frequency variations
EC 17; May 9 20123Note resonance width (FWHM) is in the order of 10-20 MHz
Controlled Mirror MotionDisturbances / Thermal effects
EC 17; May 9 20124Uncontrolled system; mirror motion depends on mount stiffness
Disturbances / Structural vibrations
Diplexer resonator length expansionAluminium casing under DTDL ~ 5e-5 DT
Controlled Mirror MotionActively controlled mirror motion system
Main requirements
Active control of single mirrorPositioning resolution: 1 - 10 m (few % transmission)Positioning stroke> 1.5 mm (1 period)Mirror rotation(3 DOF)< 1 mradLateral motion< 1 mmBandwidth > 10 100 Hz (in closed-loop)Linear response characteristics
EC 17; May 9 20125Controlled Mirror MotionEC 17; May 9 20126Mechanics of mirror motion
Main principlesLinear motion: voice-coil actuatorLeaf springs as elastic guiding mechanism; free of frictionInternal optical encoder as position sensor
flangevoice coil actuatorelastic guiding mechanismmirrorflangeCavityMirrorFactSensorFrameControlled Mirror MotionMovable Mirror mechanism implemented
EC 17; May 9 20127
Controlled Mirror MotionMirror motion in action
Scanning motion
EC 17; May 9 20128Test IPF StuttgartJanuary 2012
Controlled Mirror MotionIncreasing the systems bandwidth
Position sensor feedback
Low order feedback controller gives higher effective stiffnessHigher bandwidth -> faster response -> higher performanceFunctions as inner control-loop for main power control approach
EC 17; May 9 20129
Controlled Mirror MotionControlling the mirror motion
Output powers are the controlled variablesFeedback of power signals is most direct approach
EC 17; May 9 201210
Controlled Mirror Motion
EC 17; May 9 201211
Controlled Mirror MotionGradient-type optimisation
Given a cost function J(x), to be minimisedRecursive minimisation by gradient search
In case of FADIS, cost function J(x) could be the output power OUT 1However, the gradient of the power curves is unknown.
EC 17; May 9 201212
Controlled Mirror MotionEC 17; May 9 201213Controlled Mirror MotionDither-based gradient optimization (2)
Add sinusoidal perturbation to current mirror positionUse small amplitude, typically 1 mmStep-size of gradient algorithm is limited to have proper estimation => possibly slow convergenceThe higher the dither frequency, the faster the convergenceVery robust approach; performs irrespective of shape of cost function
Also referred to as Extremum Seeking ControlEC 17; May 9 201214Controlled Mirror Motion
EC 17; May 9 201215Controlled Mirror MotionExperiment (0)The effect of a stationary mirror position
EC 17; May 9 201216
Test IPP GreifswaldJune 2010Controlled Mirror MotionEC 17; May 9 201217
Test IPP GreifswaldJune 2010Controlled Mirror MotionExperiments (1)
Mirror motion follows the frequency variationsEC 17; May 9 201218Test IPP GreifswaldJune 2010
Controlled Mirror MotionEC 17; May 9 201219Test AUG GarchingApril 2012
Controlled Mirror MotionaliasingExperiments (3)
Power switching by mirror motionPower trajectory is a 32 Hz sinusoidEC 17; May 9 201220Test AUG GarchingApril 2012
Controlled Mirror MotionEC 17; May 9 201221Test IPP GreifswaldJune 2010
Controlled Mirror MotionExperiments (5)
Resonance control for in-line ECEMinimisation of P1 powerCombined frequency feedforward and power feedbackEC 17; May 9 201222Test AUG GarchingApril 2012
Controlled Mirror MotionExperiments (5)
Combined frequency feedforward and power feedback Fast initialisation by feedforwardFine adjustment by power feedbackEC 17; May 9 201223Test AUG GarchingApril 2012
Controlled Mirror Motion
Experiments (6)
Low power test using Magic-T based interferometric set-upEC 17; May 9 201224Test IPF StuttgartJanuary 2012
W. Kasparek, EC-17Controlled Mirror MotionConclusions
Mirror motion system to keep diplexer at required resonator length
Linear, friction-free actuation and guidanceWeight of mirror limits motion speedNon-linear power curves complicate controlSeveral approaches possible:Control at 1 slope of the curves (50% coverage)Small perturbation based adaptive control (100% coverage)Frequency signal feedforwardInterferometric Magic-T set-up Combinations of the above
Generic controlled motion concept for active manipulation of mm-waves..(?)
EC 17; May 9 201225Controlled Mirror MotionEnd of presentation
EC 17; May 9 201226Controlled Mirror Motion
Controlling the mirror motion
Response of mirror position sensor to actuator voltage is slow but highly linear
The response of both output powers to mirror position is fast but not linearEC 17; May 9 201227
Controlled Mirror Motion
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