Introduction to COMSOL based Modeling of

Levitated Flywheel Rotor

Adam Piłat, ap@agh.edu.pl

Faculty of Electrical Engineering, Automatics, Computer Science and ElectronicsDepartment of Automatics

Ludwigsburg, October 26th, 2011

Agenda

• Active Magnetic Levitation• Kinetic energy storage system• Active Magnetic Suspension & Active Magnetic Bearing –

laboratory equipment• Flywheel optimization• Components integration• Eigenfrequency analysis• Other aspects and future work• Conclusions

Active Magnetic Levitation

• Non-contact operation• No mechanical friction• Dynamics control • On-line monitoring and

supervisory control

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emFaN S

Object

A

N

gF

gigu

di du

emgF

emdF

aaag ∆−=

aadad ∆+−=

a∆d

a

gF

Kinetic energy storage system

• Flywheel energy storage (FES) works by accelerating a rotor (flywheel) to a very high speed and maintaining the energy in the system as rotational energy. When energy is extracted from the system, the flywheel's rotational speed is reduced as a consequence of the principle of conservation of energy;

• System components: rotor, bearings, motor/generator, control system, energy transmission system

• Research towards optimal structure by analysis and study on materials, bearings, rotor dynamics, aerodynamical friction, safety, economical aspects

AGH - Active Magnetic Suspension & Active Magnetic Bearing – laboratory equipment

• Experience in Design, Prototyping, Modelling, Simulation, Identification and Control System

• AMS and AMB prototypes• Custom controller• Custom methods for

integrated prototyping including control tasks

Active Magnetic Bearing (AMB)

PAC - Hard real-time Controller

Active Magnetic Suspension(AMS)

Towards optimal flywheel

Towards flat disk and rigid bodyTypical constructions

Motor/generator

Bearing

Bearing

Radial stress[Pa]

Radius [m]

Optimization of Flywheel profile

• Aluminum

0.04 0.06 0.08 0.1 0.120

0.005

0.01

0.015

0.02

r [m]

h [m

]

300050001000015000

0.04 0.06 0.08 0.1 0.120

0.005

0.01

0.015

0.02

r [m]

h [m

]

300050001000015000

• Steel

Flywheel profiles for a different rotational speeds given in rpms. a) aluminum; b) steel.

Optimization of Flywheel profile

• Aluminum • Steel

0.04 0.06 0.08 0.1 0.120

1

2

3

4

5

6x 10

7

Radial coordinate [m]

Stre

ss σ

[Pa]

σ rσ φ

σ rσ φ

0.04 0.06 0.08 0.1 0.120

5

10

15

x 107

Radial coordinate [m]

Stre

ss [P

a]

σ rσ φ

σ rσ φ

Radial (blue) and azimuthal (red) stress components for initial (dashed line) and optimized (solid line) flywheel profiles calculated at 1500 rpm. a) aluminum; b) steel

Kinetic energy stored vs rotational speed

2000 4000 6000 8000 10000 12000 14000

2000

4000

6000

8000

10000

12000

ω [rpm]

E k [J

]

AluminumSteel

Towards complex prototyping

Custom MATLAB/COMSOL function

MATLAB/COMSOL/LiveLink

Flywheel profile optimization +

export

rotor generator and assembly

rotor analysis AMB construction

generator

1

2

3

Rotor

AMB Path

Rotor Stator

Coils

Rotor eigenfrequency analysis

Surface displacement in nanometers for rotational speeds: a) 3000 rpm; b) 15000 rpm.

Other aspects and future work

• Components to be included:– motor/generator– AMB control– Rotor dynamics

• Extension of current study stage:– Model of the complete system– Thermal, Magnetic and Aerodynamic

aspects• Multiobjective optimization

Conclusions

• COMSOL allows to perform a number of required analysis

• Custom methods for design, optimisation, integration and AMB generation

• On the base of construction properties the AMB and rotor dynamics can be considered

• It is possible to build the complete 3D virtual prototype?

Thank you for your attention