Page 68: of Offshore Engineer Magazine (Oct/Nov 2014)

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the fractional exponent is the analytical solution of the diffusion equation for a semi-in? nite medium. This parameter is used as the optimization parameter during

Subsea the identi? cation process.

Step 3 - Synthesizing: Once the fractional transfer functions are identi- ? ed, it is necessary to synthesize them as an integer order. Real (integer) systems typically have non-integer behavior over a given frequency band. The non-integer integrator is in fact limited to a de? ned frequency range (fmin-fmax). The syn-

FEM versus “Identi? ed Equivalent Reduced Order-Model” simulation results.

thesis of non-integer order integrator is then based on a recursive distribution of a ? nite number of poles and zeroes (eq.1 right-side expression). The nonlinearities such as large air gap variation and high

SamSon takes the current level inducing a large magnetic saturation are taken in account. These physical quantities have a signi? cant out of

HEAVY impact on the representativeness and model accuracy.

heavylift

Results obtained using identi? ed nonlinear fractional model slings

The total magnetic ? ux response to a maximum step of current (with ? xed rotor position 50% of the total air gap / canned bearing) was recorded, as was the position response to a pro? le of a speci? c external force perturbation.

Data showed that the total magnetic ? ux converged with the same dynamics of its steady state value, while the position reacted properly to the external force perturbation.

These results showed that the method proposed in this paper predicts with

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response of the thrust magnetic bearing.

Moreover, one of the most interesting bene? ts is the simulation time ef? ciency, which opens the way to implement this model in a Hardware-in-the-Loop pro- cess for real-time simulation purpose.

LIGHt SaFE FaSt EFFICIEnt

Conclusion

Talk to the experts at Samson and put their experience and extensive

The collaborative design approach testing to work on your next heavylift project.

applied to oil and gas motor-compressors equipped with AMBs, in particular for

Visit SamsonRope.com for the full case study on the subsea application is a powerful and ef? -

Seaway Heavy Lifting/Greater Gabbard project.

cient tool to collect and consolidate the speci? cation of the project among the dif- ferent project partners and key players.

By limiting iterations in design as well as identifying clearly the technology readi- ness levels needed for each of the single components and subsystems, it offers ® the opportunity to de? ne better design

Dyneema is a registered trademark of Royal DSM N.V. Dyneema is DSM’s high-performance polyethylene product.Dyneema is DSM’s high-performance polyethylene product.Dyneema is DSM’s high-performance polyethylene product.

speci? cations, reduce the time for testing and quali? cation and ultimately reduce

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