The Power Ring Energy Storage Flywheel
The Power Ring Energy Storage Flywheel
The Power Ring Energy Storage Flywheel
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<strong>The</strong> <strong>Power</strong> <strong>Ring</strong><br />
<strong>Energy</strong> <strong>Storage</strong><br />
<strong>Flywheel</strong><br />
Mike Ricci<br />
10-16-2007<br />
www.launchpnt.com<br />
1
Conventional High Speed <strong>Flywheel</strong><br />
Conventional High Speed <strong>Flywheel</strong><br />
Carbon fiber rim<br />
Spokes or hub connect rim to shaft<br />
Small diameter, small gap bearings<br />
on shaft<br />
Motor/generator on shaft<br />
Difficult to scale design up:<br />
Hub must be flexible to allow for centrifugal stretching of rim, yet<br />
must support large rim mass<br />
Resonances in rim-flexible hub structure can be excited by rotor and<br />
lead to unstable operation<br />
2
<strong>Power</strong> <strong>Ring</strong> Architecture<br />
Hub-Less Rim<br />
Patented “Shear force” PM bearing on inner surface<br />
Upper VCA coils<br />
Upper VCA magnets<br />
Radial Displacement<br />
sensor (1 of 2)<br />
Top Touchdown Bearing<br />
elements<br />
Upper Bearing<br />
Magnetic rings<br />
Nominal 2 mm<br />
levitation gap<br />
Motor Stator<br />
2 kW/Hr technology<br />
demonstrator<br />
Motor<br />
Rotor Pole<br />
Hubless<br />
Carbon<br />
Fiber Rim<br />
40 cm OD, 28 kg carbon<br />
fiber rim<br />
Axial Displacement<br />
Sensor (1 of 3)<br />
Bottom touchdown<br />
Bearing elements<br />
Bottom VCA coils and magnets<br />
Bottom Magnetic<br />
Bearing<br />
3
Eventual Goal<br />
Eventual Goal<br />
2000 to 3000 kg rim<br />
2 m in diameter, 1 m tall<br />
250 kW/Hr storage<br />
4
Launchpoint Design Process<br />
Launchpoint Design Process<br />
Concept Evaluation<br />
Model analytically<br />
Verify/Validate with FEA/simulation tools<br />
Iterate analysis optimization and FEA validation<br />
Experimental Validation of Subsystems<br />
Further optimize (nonlinear, difficult to analyze<br />
situations) with FEA or other simulation tool<br />
5
Concept Evaluation<br />
Concept Evaluation<br />
Quick evaluation of different design solution<br />
concepts<br />
Analytical equations / basic physics<br />
Simple simulation/FEA models at non-optimal design<br />
points<br />
“Proof of concept” calculations and simulations<br />
6
Analytical Models<br />
Analytical Models<br />
Model analytically<br />
search design space, evaluate different conceptual<br />
designs<br />
get design starting point<br />
Fast optimization possible<br />
understand basic relationships, physics, constraints<br />
on problem<br />
7
Simulation-- Verification<br />
Simulation-- Verification<br />
Verify/Validate analysis with FEA/simulation tools<br />
since equations usually not right first time (or even<br />
second!)<br />
Identify incorrect approximations<br />
Identify phenomena not modeled in analysis<br />
8
Concept Design Iteration<br />
Concept Design Iteration<br />
Iterate between analysis optimization and FEA<br />
validation<br />
Debug/refine analytical models<br />
Parametric features of Ansoft Maxwell extremely useful<br />
here…<br />
9
Final Design Optimization<br />
Final Design Optimization<br />
Further optimize (nonlinear, difficult to analyze<br />
situations) with FEA or other simulation tools<br />
Slow optimization possible since starting near optimum<br />
Toroidal motor design, optimize magnet ID<br />
Optimum in this case has saturated iron core, which was a<br />
“disallowed” solution for analytical models<br />
10
Permanent Magnet Levitation<br />
Permanent Magnet Levitation<br />
�Unstable / Not passively stable– Earnshaw’s Law<br />
UNSTABLE<br />
STABLE<br />
.UNSTABLE<br />
.UNSTABLE<br />
UNSTABLE<br />
STABLE<br />
STABLE<br />
STABLE<br />
11
Active Stabilization of Unstable System<br />
Active Stabilization of Unstable System<br />
Inverted pendulum dynamics (unstable system) control<br />
Standard “text book” controls problem<br />
Routinely solved in PM bearings for rotors<br />
<strong>Power</strong> <strong>Ring</strong> has multiple degrees of freedom which<br />
complicates matters substantially<br />
12
Halbach Array of PM<br />
Halbach Array of PM<br />
Halbach* array doubles field strength by focusing all field on<br />
one side<br />
NdFeB magnet prices have exponentially dropped since the<br />
invention of NdFeB in the 1980’s<br />
Short pole pitch gives stiff suspension<br />
* Invented by Klaus Halbach of Lawrence Berkeley National Laboratory<br />
13
Bearing Design<br />
Mathcad initial design analysis<br />
FEA Validation<br />
Passive Suspension Magnetics<br />
7.43<br />
6.19<br />
4.95<br />
3.71<br />
2.48<br />
1.24<br />
0<br />
1.24<br />
2.48<br />
3.71<br />
Vertical Dimensions (mm)<br />
4.95<br />
6.19<br />
245 247.14 249.29 251.43 253.57 255.71257.86 260<br />
7.43<br />
Radial Dimensions (mm)<br />
Stator Suspension magnets<br />
Rotor Suspension Magnets<br />
trace 5<br />
trace 6<br />
14
PM Bearing Design Validation<br />
PM Bearing Design Validation<br />
Maxwell 2D FEA<br />
Experiment<br />
Predicted Array forces using Hc = 4850 Oe for Reance F65<br />
5<br />
0<br />
5<br />
Force (N)<br />
0 2 4 6 8 10 12 14<br />
10<br />
Offset (mm)<br />
MathCad Axial Force<br />
MathCad Radial Force<br />
FEA prediction Axial<br />
FEA prediction Radial<br />
Experimental Axial<br />
Experimental Radial<br />
15
Voice Coil Actuator Design<br />
MathCAD initial design optimization<br />
Maxwell 3D validation<br />
Suspension Voice Coil Actuator Design<br />
22.28<br />
14.56<br />
6.84<br />
Axial Dimension (mm)<br />
0.88<br />
8.6<br />
190 195 200 205 210 215 220<br />
16.32<br />
Radial Dimension (mm)<br />
Rotor Permanent Magnets<br />
Rotor Magnetization Direction<br />
Stator Coil Sections<br />
Stator Current Direction<br />
Vert Actuator Coil Sect<br />
Vert Actuator Current Direction<br />
16
Voice Coil Actuator<br />
Voice Coil Actuator<br />
Subsystem testing<br />
17
Suspension Dynamics<br />
Suspension Dynamics<br />
Translation to height coupling<br />
Translation to tilt coupling<br />
18
Suspension Dynamics<br />
Suspension Dynamics<br />
System “Launch” is design driver for control system<br />
“Launch” from power-off position is peak power for<br />
actuators<br />
Largest displacement/travel is also during launch<br />
Nonlinear bearing effects will complicate the launch<br />
dynamics<br />
Need to reduce risk/uncertainty associated with<br />
control system<br />
19
Control Design<br />
Control Design<br />
Start with simple model for feasibility<br />
Linear controller model<br />
Mathcad analytical model of bearings<br />
Linearized cross coupling<br />
<strong>The</strong>n move to full non-linear system simulation<br />
Can hope that simple linear controller will still work<br />
If not, design non-linear control system<br />
Use non-linear system simulation to validate<br />
controller design<br />
20
System Simulation<br />
System Simulation<br />
Use Simplorer for system dynamimcs simulation<br />
Initially use simple linear math model for bearing forces<br />
For nonlinear model, link Maxwell 3D force data with time<br />
domain Simplorer dynamics simulation<br />
Eventually power electronics will be included in model for<br />
analysis of component stresses during transient event<br />
simulations (such as launch).<br />
21
Non-Linear Bearing Model<br />
Non-Linear Bearing Model<br />
Parametric Ansoft Maxwell 3D model<br />
Gap Offset<br />
Base Model<br />
Z offset<br />
Tilt<br />
22
DSO – Distributed Solve Option<br />
DSO – Distributed Solve Option<br />
Host<br />
…<br />
Nodes<br />
…<br />
Number of Variations: 252<br />
Complete Solution Time : 13.6 days<br />
Computation Characteristics<br />
HP Cluster: 8 cpu’s<br />
41 Hr 30 min<br />
Real time<br />
CPU type: Intel Xeon<br />
2.6 GHz<br />
8 Gig RAM<br />
5.3<br />
Speed-up factor<br />
700,000 elements<br />
Mesh size<br />
OS: Windows XP<br />
23
Distributed Solve<br />
Distributed Solve<br />
24
Simplorer System Dynamics Model<br />
Simplorer System Dynamics Model<br />
®<br />
Axis Forces<br />
Actuator<strong>Power</strong><br />
EQU<br />
ICA:<br />
Simulation properties:<br />
Step width max 5u<br />
Step width min 5n<br />
Simulation end time 0.5<br />
Actuaators<br />
Coil Command<br />
Generation<br />
with Lo-Pass<br />
CONST<br />
Rigid Body<br />
with<br />
PM Bearing<br />
CONST<br />
CONST<br />
CONST<br />
Actuator F<br />
(Inputs)<br />
CONST<br />
Axis Force<br />
Command<br />
CONST<br />
CONST<br />
CONST<br />
Disturbance<br />
CONST<br />
State Output<br />
Kgain<br />
25
Simplorer Linearized PM Bearing Model<br />
Bearing is simulated as simple linear gains for coupling and cross<br />
coupling of motions and forces.<br />
MathCad used to derive gain values.<br />
GAIN<br />
10<br />
Kxx/2<br />
R<br />
10<br />
GAIN<br />
Fr<br />
Kfx/2<br />
GAIN<br />
GAIN<br />
Kxf/2<br />
Hb<br />
10<br />
GAIN<br />
10<br />
Tphi<br />
Kffx/2-Hb^2*Kxx/2<br />
Phi<br />
10<br />
GAIN<br />
10<br />
Fz<br />
Kzz/2<br />
Z<br />
CONST<br />
CONST<br />
gravity*R_mass/2<br />
.00252<br />
26
Simplorer Nonlinear PM Bearing<br />
Simplorer Nonlinear PM Bearing<br />
Lookup table from Maxwell DSO solution– returns forces and torques<br />
from displacement and tilt input<br />
X displacement, Y tilt<br />
10 Fx<br />
10<br />
Xbrg<br />
10 Ty<br />
Fr<br />
Tphi<br />
R<br />
Phi<br />
10<br />
PhiY<br />
Fz<br />
Z<br />
10<br />
Z<br />
GAIN<br />
Y displacement, X tilt<br />
10 Fy<br />
Fr<br />
R<br />
10<br />
Ybrg<br />
10 Tx<br />
Tphi<br />
Phi<br />
GAIN<br />
10<br />
PhiX<br />
10 Fz<br />
GAIN<br />
Fz<br />
Z<br />
-1<br />
0.5<br />
27
Linearized Model Results<br />
Simulation of launch from 2mm startup offset<br />
100.00<br />
4.00m<br />
75.00<br />
3.00m<br />
50.00<br />
2.00m<br />
25.00<br />
PhiX<br />
Actuator<br />
Forces<br />
PhiY<br />
0<br />
1.00m<br />
-25.00<br />
0<br />
-50.00<br />
-80.00<br />
-1.00m<br />
0 100.00m 200.00m 300.00m 400.00m 500.00m<br />
Time (s)<br />
0 100.00m 200.00m 300.00m 400.00m 500.00m<br />
Time (s)<br />
4.00m<br />
1.00m<br />
800.00u<br />
3.00m<br />
600.00u<br />
2.00m<br />
X<br />
Z<br />
400.00u<br />
Y<br />
1.00m<br />
200.00u<br />
0<br />
0<br />
-1.00m<br />
-200.00u<br />
0 100.00m 200.00m 300.00m 400.00m 500.00m<br />
Time (s)<br />
0 100.00m 200.00m 300.00m 400.00m 500.00m<br />
Time (s)<br />
28
Nonlinear Model Results<br />
Simulation for small offset -- Controller still worked (shown)<br />
Controller failed to remain stable and launch with a full 2mm startup offset<br />
30.00u<br />
17.20<br />
-50.00u<br />
10.00<br />
-100.00u<br />
PhiX<br />
5.00<br />
-150.00u<br />
PhiY<br />
0<br />
-200.00u<br />
Actuator<br />
Forces<br />
-250.00u<br />
-5.00<br />
-10.00<br />
-324.00u<br />
0 100.00m 200.00m 300.00m 400.00m 500.00m<br />
Time (s)<br />
-16.40<br />
0 100.00m 200.00m 300.00m 400.00m 500.00m<br />
Time (s)<br />
2.42m<br />
24.00u<br />
2.42m<br />
2e-020<br />
-20.00u<br />
2.42m<br />
X<br />
Z<br />
Y<br />
-40.00u<br />
2.41m<br />
-60.00u<br />
2.41m<br />
-80.00u<br />
2.41m<br />
-100.50u<br />
5.00n 100.00m 200.00m 300.00m 400.00m 500.00m<br />
Time (s)<br />
0 100.00m 200.00m 300.00m 400.00m 500.00m<br />
Time (s)<br />
29
Small Scale Prototype<br />
PM Bearings successfully tested<br />
Active Control system electronics being fabricated<br />
30
Conclusions<br />
Naïve linear controller will not be adequate for<br />
system startup/launch transient<br />
Nonlinear system model will be used to evaluate<br />
and test proposed controller designs before<br />
implementing in hardware.<br />
31
Thanks:<br />
This work has been supported by grants from<br />
US Navy<br />
NYSERDA (New York State <strong>Energy</strong> Research and<br />
Development)<br />
NSF<br />
DOE<br />
OSD (US Navy Office of Scientific Development)<br />
Thanks to Ansoft for their support<br />
Liyan Qu<br />
Julius Saitz<br />
32
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