1. Combined April and May 2007 Monthly Report
B5.1 Development of a Reliable, Efficient, Lightweight and Compact Cryocooler
Combined April and May 2007 Monthly Report
PI: Dr. Louis Chow
Co-PIs: Drs. Jayanta Kapat, Thomas Wu and Faissal Moslehy
Postdoc: Dr. Lei Zhou
Graduate Students: Shaohua Lin and Gavin Barnes
Principal Authors: Dr. Lei Zhou and Shaohua Lin

2. Project overview Compressor Rotor design completed
Rotor with attached impeller and embedded magnet.
Rotor-dynamic analysis confirms critical speed > 160k RPM
Motor design completed
Stator, magnet and winding are ordered
Motor controller hardware is acquired
Motor controller software development has started
Compressor test rig structure design completed
Detailed compressor structural design completed in 3-D model with Pro/E
Prepare detailed 2-D drawings of parts for machine shop

3. Motor and controller design
SECTION I
Motor and controller design

4. Digital Control Design of PMSM
Principles
Implementation

5. Principles Open Loop V/f Control Block Diagram of the V/f Controller
Driver Circuit
Conclusion

6. Main Idea of V/f Control
Neglect the winding resistance
is flux linkage per phase
The goal is to maintain a constant voltage to frequency ratio

7. Ideal V/f Control Profile

8. Actual V/f Control Profile

9. Block Diagram of Controller

10. Driver Circuit
DC to AC inverter Va
M1 on t
M2 on

11. Pros and Cons of open loop control
easy to implement
Cons:
no feedback, unstable compared to closed loop control

12. Implementation of Open Loop V/f control Using SD Ez DSP 2812 board

13. Hardware Features
TMS320F2812 Digital Signal Processor in socket operating at 150 Mhz.
18 K on chip RAM
128 K on chip FLASH ROM
64 K words on board RAM
Expansion Connectors (unpopulated)
Onboard embedded IEEE JTAG controller
+5 volt operation with supplied adapter
Onboard IEEE JTAG emulation connector
Compatible with eZdsp Wire Wrap Prototype Card

14. Software Features
Compatible with C2000 Code Composer from Texas Instruments (Includes 'C' compiler, assembler, linker, debugger) 
Compatible with SD Flash programming utility from Spectrum Digital

15. Program Flow Chart

16. Code Composer Studio Setup

17. Code Composer Studio Setup Workspace

18. Main Function of the Control Program

19. SECTION II
Compressor design

20. Compressor assembly appearance
Top cover
Inlet
Base Board

21. Compressor assembly appearance
Outlet
Bearing support
Bearing

22. Compressor structure De-swirler and diffuser Impeller Bearing
Outlet volute chamber
Motor wire and cooling channel
Intake volute chamber
stator

23. Base board and frames (I)
Dwelling hole
Outlet frame
Inlet frame
Bolt holes

24. Base board and frames (II)
Compressor base holes
Frame bolts
Dwelling hole

25. Base board and frames (III)
Material: carbon steel
Functions:
Provide sturdy support of compressor rotor
Provide accurate tip-gap controls
Features:
High stiffness support
Self-aligned
Dwelling holes and pins provide high assembling accuracy

26. Rotor design Material: Impeller attachment: Total length: 107mm
High stress stainless steel
Impeller attachment:
Tight fit
Total length: 107mm
Span length: 99mm
Shaft diameter: 18mm
Impeller diameter: 51mm
Critical speed: >160k RPM
Permanent Magnet

27. Threaded for seal cover
Bearing housing
Threaded for seal cover
Material: Brass
Features:
Dwelling holes ensure high alignment accuracy
Brass provides good heat spreading and wear resistance
Side threads for seal cover to ensure compressor’s complete sealing
Attach water cooling accessory for bearings if necessary
Dwelling hole
Bolt holes

28. Main sub-assembly (I) Bolt hole dwelling hole
Main sub-assembly includes all the major functional components of the compressor
This sub-assembly will be installed into the base-frame with dwelling pins and bolts
Bolt hole
dwelling hole

29. Main sub-assembly (II)
Inner structure of the main sub-assembly
Motor stator and wire
Diffuser
Impeller
Intake volute
Outlet volute
Rotor and bearing 5 4 2 1 3 6

30. Assembling procedure (I)
Fixing the frames on the base board is the first step to assemble the compressor
Base bolts

31. Assembling procedure (II)
Insert the main sub-assembly into frame and insert the bearing support at both sides
Insert the dwelling pins and tighten the bolts

32. Final assembly 5.9 inch 6.1 inch 4.9 inch
Place the top cover with bolts to finish the assembling

33. Future work Develop and test open-loop controller codes
Deliver compressor parts drawings to machine shop
Develop new de-swirler and diffuser