CLOSING THE LOOPCLOSING THE LOOP

Teaching Control System Teaching Control System Theory and Design ThroughTheory and Design Through

ExperimentationExperimentation

Project Design Engineer Project Mentors

Mark Kapsch Dr. Brian Hodgkin

Mr. Steve Innes

PreliminariesPreliminaries

Purpose of ProjectPurpose of Project Overview of Control System Overview of Control System

TheoryTheory Antenna Azimuth Model Antenna Azimuth Model

ConstructionConstruction Parts and Labor Parts and Labor ScalabilityScalability

Reason for DesignReason for Design

Experimental Model Experimental Model for Control Systems for Control Systems Design Course, Design Course, ELE425ELE425• Commonly Commonly

Encountered Control Encountered Control System Design System Design ProblemProblem

• Experimentation and Experimentation and Analysis Enhances Analysis Enhances the Learning the Learning ExperienceExperience

70m Deep Space Tracking AntennaGoldStone Complex, CaliforniaPhoto Courtesy of NASA JPL

Basic Control System Theory Basic Control System Theory

Control Systems Use Feedback Control Systems Use Feedback Loops to Manipulate the Circuit Loops to Manipulate the Circuit OutputOutput

o s

potK

potK

K m

m

K

s s a gK

Motor and Load

aE s eV s iV s i s

Input Potentiometer

Position Sensor

Differential Amplifier

m s

Gears Desired Azimuth

Angle

Antenna Azimuth

Angle

Transfer Function for the Model Transfer Function for the Model Antenna Azimuth SystemAntenna Azimuth System

2

pot m g

m g m pot

KK K K

s a s KK K K

is

os

sT

Building the Experimental ModelBuilding the Experimental Model

Center Pin, Slip Ring Assy and Thrust Bearing

Feedback Potentiometer

Antenna Azimuth Control Mechanical System Side View

Motor

Input Potentiometer Handy Board

(Power Amplifier) Differential Pre-Amp

Not to Scale

Drive Train

Initial Concept

As ConstructedAs Constructed

Center Pin, Slip Ring Assy and Thrust Bearing

Feedback Potentiometer

Antenna Azimuth Control System Side View

Motor

Input Potentiometer

Differential Amplifier Not to Scale

Drive Train

+_

Model Antenna Azimuth System assembled and ready for testing

Analog System Schematic DiagramAnalog System Schematic Diagram

U1

LM741CN

3

2

4

7

6

51Vin

50%

Vfb 50%

VSS12 V

VEE12 V

RG_10 60%

RG_90

4.7kOhm_5%

RG

5.1kOhm_5%

RF

10kOhm_5%

RF210kOhm_5%

Rcomp 50%

S1

MOTOR

M

Antenna Azimuth Control System

University of Southern Maine

Mark Kapsch 04 May 2007

Gain = RF/RG

Proposed 2006 2007

SEP OCT NOV DEC JAN FEB MAR APR MAY

Programming

Pre-Proposal Due

Parts on Order

Project Proposal Due

Unit Built

Building

Algorithm Complete

Control System Design Analysis and Specification

Presentation

Test and Adjustment

Produce Classroom Materials T

I

M

E

L

I

N

E

Actual 2006 2007

SEP OCT NOV DEC JAN FEB MAR APR MAY

Test and Adjustment

First Pre-Proposal Complete

Project Proposal Complete

Building

Control System Design Analysis and Specification

Presentation

Project Not Unique

Second Pre-Proposal

Complete

HandyBoard Motor Outputs Are Stepped

Design Analog Control System

10 56

56 56

Power Supply

Inadequate Preamp Not

Working

All Parts On-Hand

Motor Torque

Parts and LaborParts and Labor

Initial Budgetary Initial Budgetary AllocationAllocation• $1000 or less$1000 or less

Part CostsPart Costs• EstimatedEstimated

$745.60$745.60

• ActualActual $909.64$909.64

• OverrunOverrun $164.04$164.04

Labor CostsLabor Costs• 217.5 Hours X 217.5 Hours X

$16.00/Hour = $16.00/Hour = $3480$3480

• Total $4353.86Total $4353.86

Scalability of DesignScalability of Design

Built-in Option for Digital Control Built-in Option for Digital Control System ImplementationSystem Implementation

Ability to add Sensors or Motors Ability to add Sensors or Motors above the Rotating Pedestalabove the Rotating Pedestal

Modular DesignModular Design• Allows alternate components to be Allows alternate components to be

easily implementedeasily implemented

Antenna System Antenna System Phase 2Phase 2

Project has been selected by Project has been selected by Gabe Garza for enhancementGabe Garza for enhancement

Elevation system to be addedElevation system to be added Modification scheduled for Fall Modification scheduled for Fall

07 to Spring 0807 to Spring 08

SummarySummary

Need for ProjectNeed for Project Control System TheoryControl System Theory Development and ConstructionDevelopment and Construction Project CostProject Cost Future GrowthFuture Growth

Questions?Questions?

Center Pin, Slip Ring Assy and Thrust Bearing

Feedback Potentiometer

Antenna Azimuth Control System Side View

Motor

Input Potentiometer

Differential Amplifier Not to Scale

Drive Train

BackupBackup

Block Diagram ReductionBlock Diagram Reduction

potK

potK

m g

m

KK K

s s a

os

eV s

iV s

is

Potentiometer

Potentiometer

potK

potK

K m

m

K

s s a

gK

Power Amp

Motor and Load

aE s

os

eV s

iV s

is

Potentiometer

Potentiometer

ms

Gears

potK

m g

m

KK K

s s a

os

is

pot m g

m

K KK K

s s a

os

is

sG

2

pot m g

m g m pot

KK K K

s a s KK K K

is

os

sT

1

G sT s

G s H s

UnknownsUnknowns

Motor 1N

2N LJ

LD ,a aJ D

Mechanical System

1

t

m m a m

a m t bm

m a

Ks K R J

E s s s a K Ks s D

J R

2

1

2m a L

NJ J J

N

2

1

2m a L

ND D D

N

The value t

a

K

R is the motors torque constant divided by the motor armature resistance and

is equal to the rated stall torque of the motor divided by the motor armature input voltage

Stall

a

T

e.

Armature input voltage divided by the no-load speed of the motor results in the back

EMF constant of the motor or ab

no load

eK

.

The Mechanical System Problem

The Electrical System Problem

243.82

2volts

potrad

K

RFK

RG

This calculation makes two assumptions. First that saturation is never reached and second that the response of the amplifier is fast enough to neglect delay effects. If it is determined through experimentation that the response has been delayed the transfer

function for the amplifier will need to be modified to K

s a where

RFK

RG and

Rfa

RG .