Design of Disturbance Rejection Controllers for a Magnetic

Suspension System

By: Jon DunlapAdvisor: Dr. Winfred K.N. Anakwa

Bradley UniversityDecember 6, 2005

Summary Multiple Controllers

for Multiple Disturbances

Created In Simulink

xPC Target Box Serving as “Controller Container”

Minimize Steady-State Error, Overshoot and Setting Time

Develop Controller Switching Method

Summary

Goals Functional Description Block Diagram Datasheet Preliminary Lab Work Schedule of Tasks Additional Goals

Goals Previous Work

Classical Controller Without Rejection

Works With Step

To Do Multiple Controllers

For Various Inputs

Use Internal Model Principle

Automatic Controller Selection

Functional Description Host PC using Simulink and xPC software xPC Target Box with Controllers Magnetic Suspension System

Controller and Plant

Set Point

Reference Signal

Disturbance

Block Diagram Magnetic Suspension System xPC Target Box

+Reference

Se

t Po

int

Error Controller on xPC

Target BoxControl Signal ‘U’ +

Dis

turb

an

ce

Disturbance Model

Magnetic Suspension

System

Photo sensor

Ball Position

Position Signal

Magnetic Suspension System Control and Disturbance Drives Current Current Induces Magnetic Field Field Suspends Ball Sensor Translates Location into Voltage

xPC Target Box and Host PC Using ±10 V ADC and DAC Download Controllers, Upload Commands Process Position Data and Passes Control

Datasheet Disturbance Classes

Step Ramp Sinusoidal Square – Triangular

Steady-State Error 50mv

% Overshoot 18%

Settling Time 60ms

Previous Work Shows “Useable” Values

Preliminary Lab Work Disturbance

Classes with Plant SS Equations Using Controller

Canonical Form

Disturbance State Space Equation

k*Cos(a*T)

k*Sin(a*T)

k-unit step

k-unit ramp

kxy

ux

xky

uxx

0

0

1

01

00

xky

uxa

x

0

0

1

01

0 2

xkay

uxa

x

0

0

1

01

0 2

Preliminary Lab Work

Tested Classical Controller With Disturbance

Researched Internal Model Principle with Disturbance Rejection Focus

0 0.5 1 1.5 2 2.5 30

0.05

0.1

0.15

0.2

0.25

0.3

0.35

.25 Input Reference

input w/.1sin(pi*t) disturbance

input w/ .1 unit-step disturbance

Major Tasks List Utilize Internal Model Principle To Design Controllers

Implement Controllers In Simulink

Process Simulink Controllers On xPC Target Box

Fine Tune Controllers To Optimize Stability Specifications

Schedule Of Tasks12/8/2005 - 1/15/2006 Develop Paper

Controllers Implement Controllers

In Simulink

1/19/2006 - 2/9/2006 Research xPC

Implementation Test Controllers on

MSS Fine Tune Controllers

2/16/2006 - 3/9/2006 Continue Development

of Additional Controllers

Documentation of Controller Methods

Research Disturbance Detection Methods

3/11/2006 - 3/19/2006 Spring Break Begin Final

Presentation

Additional Goals Design Disturbance Detection

Hardware/Software For Automation Of Controller Usage

Simulink using FFT Determine Maximum Time Delay Allowable for

Stability Implement on xPC?

Questions?