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Active mechanical stabilisation

Active mechanical stabilisation. LAViSta L aboratories in A nnecy working on Vi bration Sta bilisation. Catherine ADLOFF Andrea JEREMIE Jacques LOTTIN Benoît BOLZON Yannis KARYOTAKIS Laurent BRUNETTI

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Active mechanical stabilisation

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  1. Active mechanical stabilisation LAViSta Laboratories in Annecy working on Vibration Stabilisation Catherine ADLOFF Andrea JEREMIE Jacques LOTTIN Benoît BOLZON Yannis KARYOTAKIS Laurent BRUNETTI Franck CADOUX Claude GIRARD Fabien FORMOSA Yan BASTIAN Nicolas GEFFROY

  2. Introduction • Future linear collider : vertical beam size of 1 nm  Movements of the two final focus quadrupoles : smaller than 0.3 nm • Problem : nanodisplacement due to ground motion • Goal of our study : active mechanical stabilisation of the final focus quadrupoles  Study sensors and actuators to measure nanodisplacements and achieve the required stabilisation  Model different mechanical structures because of the resonances induced by ground motion  Development of a feedback loop to stabilise the whole system

  3. Outline • Measurements - Sensor characteristics - Ground motion - Structure vibration 2. Modal analysis - Measurements - Simulation 3. Dynamic response - Comparison measurements/simulation - Fixed-free beam - Addition of boundary conditions 5. Future prospects - New structure design - Simulation of the whole system 4. Feedback loop - Mock up - Results

  4. 1. Measurements • Measurements - Sensor characteristics - Ground motion - Structure vibration 2. Modal analysis - Measurements - Simulation 3. Dynamic response - Comparison measurements/simulation - Fixed-free beam - Addition of boundary conditions 5. Future prospects - New structure design - Simulation of the whole system 4. Feedback loop - Mock up - Results

  5. Introduction Sensors characteristics Stabilisation of the ground Beam vibration study 1. Measurements • Goal : Sensor study and ground motion study •  Signal analysis : • Coherence : Coherence between two sensors versus frequency • Resolution : Sensor accuracy versus frequency • Signal/Noise ratio • PSD :Normalized signal power versus frequency • RMS displacement :Displacement versus a range of frequency

  6. Introduction Sensors characteristicsStabilisation of the ground Beam vibration study 1. Measurements 2 types of sensors :  Seismic sensors :Measurement of the ground velocity  Accelerometers :Measurement of the ground acceleration Non magnetic

  7. Introduction Sensors characteristics Stabilisation of the ground Beam vibration study 1. Measurements Very low amplitude of ground acceleration below 7Hz : Rate Signal/Noise low  Only noise is being measured Good coherence between velocity sensors High amplitude of ground velocity below 7Hz : Rate Signal/Noise high  Signal is being measured Good coherence between accelerometers 7Hz 100Hz 0.2Hz - Conclusion : Velocity sensors can be used to measure low frequency ground motion whereas accelerometers measure ground motion only above 7Hz

  8. Introduction Sensors characteristics Stabilisation of the ground Beam vibration study 1. Measurements Resolution 0.6nm 0.2nm 4Hz

  9. Introduction Sensors characteristics Stabilisation of the ground Beam vibration study 1. Measurements Stabilisation of the ground motion with the STACIS 2000 Stable Active Control Isolation System Isolator Honeycomb support structure User Interface Controller :to provide communications with and diagnostics of the STACIS 2000 system Isolators :contain all the necessary electronics, vibration detection and correction devices, along with passive Isolators.

  10. Introduction Sensors characteristics Stabilisation of the ground Beam vibration study 1. Measurements Guralp sensor Velocity PSD Passive table Accelerometers Passive table Active table Active table

  11. Introduction Sensors characteristics Stabilisation of the ground Beam vibration study 1. Measurements RMS Active table Passive table 10nm Good reduction 1nm Active bandwidth 4Hz 0.5Hz 50Hz

  12. Introduction Sensors characteristics Stabilisation of the ground Beam vibration study 1. Measurements Excitation of the beam measured • Resonances induced by the excitation of the beam : • Need to use a feedback loop to damp eigenfrequencies • Usefulness of modal analysis

  13. 2. Modal analysis • Measurements - Sensors characteristics - Ground motion - Structure vibration 2. Modal analysis - Measurements - Simulation 3. Dynamic response - Comparison measurements/simulation - Fixed-free beam - Addition of boundary condition 5. Future prospects - New structure design - Simulation of the whole system 4. Feedback loop - Mock up - Results

  14. Excitation spectrum Why? Experimental Numerical Experimental/Simulation Ground motion Cooling system Air flows Power supply system… 2. Modal analysis Structural resonances ( Amplified motions) Develop a know-how concerning modal analysis

  15. Why? Experimental Numerical Experimental/Simulation 2. Modal analysis beam Acquisition system Hammer Accelerometers

  16. ME' scope Why? Experimental Numerical Experimental/Simulation 2. Modal analysis • PULSE Mode shape Fourier transform Torsion 280.5Hz

  17. Why? Experimental Numerical Experimental/Simulation 2. Modal analysis - SAMCEF - • Identify eigen frequencies • Display mode shapes Mode 2: 101 Hz Mode 1: 16 Hz Mode 2: 101 Hz Modal tests on the free-fixed beam

  18. Why? Experimental Numerical Experimental/Simulation 2. Modal analysis Good relative accuracy !

  19. 3. Dynamic response • Measurements - Sensors characteristics - Ground motion - Structure vibration 2. Modal analysis - Measurements - Simulation 3. Dynamic response - Comparison measurements/simulation - Fixed-free beam - Addition of boundary condition 5. Future prospects - New structure design - Simulation of the whole system 4. Feedback loop - Mock up - Results

  20. Principle Free-fixed beam Fixed-simple supported-free beam External perturbation Ground motion Structure Equations of motion Accelerations Displacements Stresses … Dynamic Response 3. Dynamic response

  21. PrincipleFree-fixed beamFixed-simple supported-free beam Data used as input for the simulation Data used for the comparisonwith simulation 3. Dynamic response Mock-up Check the accuracy of the numerical prediction

  22. PrincipleFree-fixed beamFixed-simple supported-free beam 1000 mm Clamping system 20 mm Beam parameters : 100 Young modulus = 74000 MPa  = 0.34 (Poisson’s ratio) Volumic mass = 2825 kg/m3 Damping : ε = 0.1 % Lumped mass : M = 830 g Structure modeled with “shell” elements 3. Dynamic response Simulation parameters Model used : M

  23. PrincipleFree-fixed beamFixed-simple supported-free beam 3. Dynamic response Comparison Simulation/Measurements

  24. Principle Free-fixed beam Fixed-simple supported-free beam 3. Dynamic response Mock-up Goal of the study : change boundary conditions to change eigenfrequencies  Results shown : block Z-displacements of the structure to damp Z-flexion modes

  25. Principle Free-fixed beam Fixed-simple supported-free beam 3. Dynamic response The value of the first eigenfrequency goes up when the simple support moves away from the clamping 34Hz 34Hz 18Hz 20cm 50cm We expect amplitude of first eigenfrequency to decrease when the simple support moves away from the clamping 18Hz 34Hz

  26. Principle Free-fixed beam Fixed-simple supported-free beam 3. Dynamic response Resonance Big resonance Excitation Pick of excitation 18 Hz: Eigenfrequency when support is located at 20cm 22.5 Hz: Eigenfrequency when support is located at 30cm Conclusion : In a general way, the best option is to prevent modes to be much excited, by shifting them. Obviously, the excitation spectrum must be well known…

  27. 4. Feedback loop • Measurements - Sensors characteristics - Ground motion - Structure vibration 2. Modal analysis - Measurements - Simulation 3. Dynamic response - Comparison measurements/simulation - Fixed-free beam - Addition of boundary condition 5. Future prospects - New structure design - Simulation of the whole system 4. Feedback loop - Mock up - Results

  28. Mock upPrinciple of rejection Results 4. Feedback loop Experiments Accelerometer 2 loudspeakers 2 opposite PZT « a steel beam »

  29. Mock upPrinciple of rejection Results 4. Feedback loop Algorithm of feedback loop developed to allow the simultaneous elimination of several resonance peaks

  30. Mock upPrinciple of rejectionResults 4. Feedback loop Rejection of 6 resonances : (without and with rejection) Resonances of : -beam-support

  31. 5. Future prospects • Measurements - Sensors characteristics - Ground motion - Structure vibration 2. Modal analysis - Measurements - Simulation 3. Dynamic response - Comparison measurements/simulation - Fixed-free beam - Addition of boundary condition 5. Future prospects - New structure design - Simulation of the whole system 4. Feedback loop - Mock up - Results

  32. FF quad. PredictionNew test bench Whole system simulation Computer Aided Design – 1st version Φ=8cm Φ=14cm Conical shape - 2.5 meter long 5. Future prospects

  33. FF quad. PredictionNew test bench Whole system simulation Propose new design (inner supports …) Propose new materials (composite materials …) 5. Future prospects Prototype close to FF quadrupole design : fixed-free structure 2.5 m • Representative prototype : eigen frequencies • Easy Boundary Conditions : square section • Adaptability to get closer and closer to the FF quadrupole: Hollow core Goal : Simulate modal analysis of the future FF quadrupole

  34. FF quad. PredictionNew test bench Whole system simulation Improve efficiency of feedback loop • Type of sensors / actuators • Location of sensors / actuators along the structure • Reliability of the feedback algorithm • … Simulation could be a great help !... 5. Future prospects

  35. Conclusion • Velocity sensors can measure ground motion down to 0.1Hz • Next generation of SP500 non-magnetic sensor soon available : smaller, better sensitivity (20000V/m/s!!)  May be the sensor used for our prototype • We are able to predict the response of a structure  New adaptative prototype close to the future FF quadrupole design  Propose new design and new materials of the future FF quadrupole • Feedback loop allows the simultaneous elimination of several resonance peaks on a reduced-size mock-up  Goal : elimination of all vibration frequencies • Simulation of the whole system Mock up of the whole system

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