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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