1

DIFFERENTIAL POLARIZATION DELAY LINE Controller

FINAL REPORT

D0215D0215

Supervisor :Supervisor :Mony OrbachMony Orbach

Performed by:Performed by:Maria TerushkinMaria Terushkin

Guy OvadiaGuy Ovadia

Technion – Israel Institute of TechnologyDepartment of Electrical EngineeringHigh Speed Digital Systems Lab

2

Project GoalsProject Goals

The ultimate goal of the project isThe ultimate goal of the project is

providing digital control for providing digital control for the DDLthe DDL

3

DDL overviewDDL overview splits light within a splits light within a

fiber into orthogonal fiber into orthogonal polarizationspolarizations

actively varies the actively varies the time that one time that one polarization travels polarization travels compared to the other compared to the other polarizationpolarization

combines the two combines the two polarizations together polarizations together againagain

•Delay range ±50psec

•Delay Resolution 0.0017 pSec

4

Project DescriptionProject Description Previous usage of the DDLPrevious usage of the DDL Current usage of the DDLCurrent usage of the DDL

PC

controller

Tunable laser source

optical spectrum analyzer

DDL

Function generator

Manual control

5

The world as we see itThe world as we see it DDL contains:DDL contains:

DC brush motorDC brush motor EncoderEncoder Limit switchesLimit switches

-50 0 +50

6

Controller IOsController IOs Inputs:Inputs:

Encoder signals A,BEncoder signals A,B Limit indicatorsLimit indicators Commands from PC (via USB)Commands from PC (via USB)

controller DDL

Output:Output: PWM varying duty-cyclePWM varying duty-cycle Reports to PC (via USB)Reports to PC (via USB)

PCUSB

PWM

Encoder feedback + limits

7

System requirements System requirements

1.1. Maximal travel beyond the home/end Maximal travel beyond the home/end indications – 2mmindications – 2mm

2.2. Steady state error – not greater than a single Steady state error – not greater than a single encoder countencoder count

3.3. No cumulative positional error No cumulative positional error

4.4. Up to 3 sec convergence to the required set Up to 3 sec convergence to the required set point after reaching itpoint after reaching it

5.5. No closed loop control after reaching desired No closed loop control after reaching desired positionposition

8

Theoretical backgroundTheoretical background Digital PID Digital PID

Continuous time domainContinuous time domain

Discrete time domainDiscrete time domain

WhereWhere

0

0

)()()()( u

dt

tdeTKdtte

T

KteKtu dc

t

i

cc

00

))1()(()()()( u

T

teteTKie

T

TKteKtu

s

dct

ii

scc

tconstimealdifferentiegralTT

timesamplingT

gainK

positioncurrentpositiondesirederrorte

conditioninitialu

signalcontroltu

di

s

c

tan/int,

)(

)(

0

P Plant

I

D

++

-

9

ImplementationImplementation

HardwareHardware MMC (PCB) + Driver (wire-wrap board) MMC (PCB) + Driver (wire-wrap board)

FPGA LogicFPGA Logic PID algorithmPID algorithm Communication with PC via DLPCommunication with PC via DLP

SoftwareSoftware GUIGUI Command line interfaceCommand line interface

10

Hardware overviewHardware overview

MMC wire-wrap

Altera

Cyclone

tran

scei

ver

tran

scei

ver

tran

scei

ver

H

bridge

HIP4020

Power

management

Power

management

DLP

USB245M

11

FPGA logic overviewFPGA logic overview

Synchronization

Debouncing

Filtering

Of signals

Position

DecodingPID

PWM

Duty-cycle

homing

Limit

protection

Communication

Main Controller

mux

Control lines

to all blocks

12

Application SoftwareApplication Software

Two versions:Two versions: GUI version for interactive useGUI version for interactive use Command line version for automationCommand line version for automation

Both versions save the last known Both versions save the last known delay, and load it on controller delay, and load it on controller power-up.power-up.

13

GUI Application GUI Application commandscommands

User commandsUser commands Set delaySet delay Redefine current delayRedefine current delay Immediate stopImmediate stop

Service commandsService commands Manual PWM override + direction Manual PWM override + direction

controlcontrol PID constants calibrationPID constants calibration Initiate Homing procedureInitiate Homing procedure Record internal dataRecord internal data

14

Command line Command line applicationapplication

Contains a subset of commands Contains a subset of commands useful for automationuseful for automation Set delay (in pSec or encoder counts)Set delay (in pSec or encoder counts) Load windup constant (controls speed)Load windup constant (controls speed)

Compatible with VEE Pro and MatlabCompatible with VEE Pro and Matlab

15

Discussion and conclusionsDiscussion and conclusions

Meeting system requirementsMeeting system requirements

Position vs. Position vs. TimeTime

go to 10 pSecgo to 10 pSec

12121 encoder12121 encoder

countscounts

16

Discussion and conclusions cont.Discussion and conclusions cont.

Use of a model:Use of a model: Differences between the model and the Differences between the model and the

DDL and their consequencesDDL and their consequences Use of work previously done in the Use of work previously done in the

lab – pros and cons.lab – pros and cons. Power upPower up Chip safetyChip safety

Implementation alternativesImplementation alternatives MicrocontrollerMicrocontroller

17

What’s next ?What’s next ? Algorithm improvement / additional featuresAlgorithm improvement / additional features

Trajectory planningTrajectory planning Dual loop (velocity control)Dual loop (velocity control) Notch filter (mechanical resonance)Notch filter (mechanical resonance) Backlash compensation algorithmBacklash compensation algorithm User defined software limitsUser defined software limits

Hardware improvementHardware improvement Custom PCB, no wire-wrapCustom PCB, no wire-wrap

Tighter integration with the equipment at the EO labTighter integration with the equipment at the EO lab Automatic zero detection / calibrationAutomatic zero detection / calibration

18

Demonstration – EO lab.Demonstration – EO lab. Short demonstration:Short demonstration:

Homing procedureHoming procedure ““go to” 20 pSec delay positiongo to” 20 pSec delay position Return to 10 pSecReturn to 10 pSec Find zero manually and set it thereFind zero manually and set it there Power off the controllerPower off the controller Turn back on – last known position is retrievedTurn back on – last known position is retrieved

19

The enDThe enD

Just follow the yellow optical fiber !Just follow the yellow optical fiber !(to the land of OZ optics)(to the land of OZ optics)