Magnetic Suspension System Control Using Position and Current Feedback

Magnetic Suspension System Control Using Position and

Current Feedback

Team: Gary Boline and Andrew Michalets

Advisors: Dr. Anakwa and Dr. Schertz

Applications of a Magnetic Suspension System

Electromagnetic Suspension Train

Frictionless Magnetic Bearings

Determine if Current Feedback can be utilized to improve performance No success with Current Feedback

Develop New Position Controller Design Methods Implement: xPC & Coldfire

Summary

Outline Magnetic Suspension System Overview High Level Block Diagram Current Modeling Current Controller Attempts Position Controller Development Microcontroller Implementation Future Suggestions References Questions

System Overview

Outline Magnetic Suspension System Overview High Level Block Diagram Current Modeling Current Controller Attempts Position Controller Development Microcontroller Implementation Future Suggestions References Questions

High Level Block Diagram

Control System

Magnetic Suspension

Plant

Photo Sensor

Current Sensor

Set Point

Reference Signal

A/D Converter D/A Converter

Outline Magnetic Suspension System Overview High Level Block Diagram Current Modeling Current Controller Attempts Position Controller Development Microcontroller Implementation Future Suggestions References Questions

Current Modeling Experimental Simulink

Transfer Function Rate Limiter

(nonlinear)

Outline Magnetic Suspension System Overview High Level Block Diagram Current Modeling Current Controller Attempts Position Controller Development Microcontroller Implementation Future Suggestions References Questions

Current Controller Attempts State-space Current with Lag, Lead, or Lag/Lead

Noise Problems Current Feed-forward Current Error Feed-forward

Based on Proportion to Position Position Integrator ‘integrates’ current

term out

Outline Magnetic Suspension System Overview High Level Block Diagram Current Modeling Current Controller Attempts Position Controller Development Microcontroller Implementation Future Suggestions References Questions

Position Controller Development

Root Locus Attempts Block Diagram Simulation Data Scope Plots Performance Data vs. Specs

Position Controller Development

Root Locus Open Loop Poles:

1.0321, 0.9689 Closed Loop

Poles: 0.9704+/-0.0077j, 0.8550, 0.3888

Expanded

Position Controller Development

Block Diagram

Position Controller Development

StepResponse

(simulation)

28% OS

Position Controller Development

StepResponse

(xPC) ~30% OS

Outline Magnetic Suspension System Overview High Level Block Diagram Current Modeling Current Controller Attempts Position Controller Development Microcontroller Implementation Future Suggestions References Questions

Microcontroller Implementation

Improvements Input/Output Configuration System Timing

Scope Plots Performance Data vs. Specs

Input/Output Configuration

A/D

MicroController

Con

trol

Sig

nal

D/A

Error Signal

D/A Converter Setup

Volts (mV) Controller Output +2047 FFF

: : 0 800 -1 7FF

: :-2047 000

Software Flowchart Initialize Timer

Read in A/D Error Signal

Scale A/D

Controller Implementation

Scale D/A

Timer Overflow at 1ms?

Write Data from D/A to Control Signal

Yes

Reset Timer Overflow

No

Start

Timing Improvements

Step Response

Our Controller Past Controller

Step Response Results

Our ControllerMax Amplitude : 0.2VppOvershoot : 47%Settling Time : 240 ms

Past ControllerMax Amplitude : 0.5VppOvershoot : 36%Settling Time : 560 ms

Advantages: Faster System

Disadvantages: Larger overshoot, Less input amplitude, Less stability

Outline Magnetic Suspension System Overview High Level Block Diagram Current Modeling Current Controller Attempts Position Controller Development Microcontroller Implementation Future Suggestions References Questions

Future Suggestions

Lab bench space Modularize Code Design to realistic specs Anti-aliasing filters Design System Bottom Up, Current

and Voltage Control Independently

References Jose A Lopez and Winfred K. N. Anakwa, “Identification and Control of a Magnetic Suspension System using

Simulink and Dspace Tools”, Proceedings of the ASEE Illinois/Indiana 2003 Sectional Conference, March 27, 2004, Peoria, Illinois, U.S.A.

Feedback Inc., 437 Dimmocks Mill Road, Hillsborough, North Carolina 27278. http://www.fbk.com

Simulink, Version 6.1 (R14SP1), The MathWorks Inc., Natick, MA 01760, 2004.

xPC Target Box, The MathWorks Inc., Natick, MA 01760, 2003.

Conclusion Determined Current Feedback not viable

State Space Classical

Designed New Position Controller Root Locus Simulation and xPC

Implemented Design on Microcontroller Timer Driven Faster System

Bring back focus Step back up from lower level Project importance at beginning Balance additional content

Conclusion

Questions?