Project-Based Control Education · 2006. 6. 30. · Industrial applications of control are increasingly large-scale, ... A Kalman filter. 10 IFAC Symposium on Advances in Control

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Project-Based Control Education

“All learning is in the learner, not in the teacher” — Plato

Mark W. SpongDonald Biggar Willett Professor

Department of Electrical and Computer Engineeringand The Coordinated Science Laboratory

University of Illinois at Urbana-Champaign, [email protected]

IFAC Symposium on Advances in Control Education, June 21-23, 2006, Madrid, Spain


IntroductionIn the book, Engineering in History*, one finds the following chronology of

the major developments in engineering:``[T]he presentation [of this book] is oriented about eight of the great events

of history which totally changed the ways of human life. These are:Food-producing revolution (ca. 6000-3000 B.C.)Appearance of urban society (ca. 3000-2000 B.C.)Birth of Greek science (600-300 B.C.)Revolution in power (middle ages)Rise of modern science (seventeenth century)Steam and the Industrial Revolution (eighteenth century)Electricity and the beginnings of applied science (nineteenth century)Age of automatic control (twentieth century) (Italics mine)

*Kirby, et.al. Dover Publications, New York, 1990.

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The 21st CenturyThe importance of Automatic Control will continue to increase in this century due to:

advances in theory, computation, sensingnew application domains in biological sciences, nanotechnology, roboticschanging demographics, the need to secure critical infrastructure, the need for energy efficiencyconsumer demands in automotive, aerospace, electronics, home appliances


Component Design vs. Systems Engineering

"To develop a complete mind, study the science of art, study theart of science. Learn how to see. Realize that everything connects to everything else." — Leonardo da Vinci

A recent National Academy of Engineering report cites interdisciplinary systems engineering as an increasingly important aspect of modern engineering and the education of future engineers. Industrial applications of control are increasingly large-scale, complex, and interdisciplinaryHow does this impact the way we teach control?

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Component Design vs. Systems Engineering

The reductionist approach to engineering and applied science has served us well and will continue to serve us.However, it is insufficient to prepare engineering students for industrial projects that are increasingly being conducted by multi-disciplinary teams of engineersMoreover, control is important enough that all engineering students and, indeed, all students should be exposed to it’s fundamental concepts.My premise is that we generally do a good job preparing control engineers but we should think more broadly.


Interdisciplinary EducationInterdisciplinary engineering education can be addressed through projects that integrate elements of mechanical design, electronics design, modeling, control system design, and software implementation.Projects can also be used to motivate and teach concepts of control to non-engineering students and to education the general public about technology.Robotics and Mechatronics projects seem to be the most popular way to accomplish this.

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Undergraduate Systems and Control Education at Illinois

FEEDBACKCONTROL SYSTEMS

SYSTEMS AND ENTREPRENEURIAL

ENGINEERINGROBOTICS MECHATRONICS


Mechatronics Projects

Mechatronics Lab

Introduction to Mechatronics is a

fourth year elective course that

culminates in a team-based project

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The Mechatronics Course

Concepts of Mechatronicsputting intelligence onto physical systemssensing, actuation, design

Real-Time ProgrammingElectronics

serial and parallel communication, I/O, interruptsboard design

Noise and filteringModeling and Control

PID, State SpaceFinal Project


First Example:The Segbot Project

The Segbot design team, David Chen, Erik Bettini, Chris Graesser, Andy Block, Carlos Montesinos

The Segbot is a small, two-wheeled self-balancing robot

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Some Features of the Segbot

The Segbot incorporates:

•On-board DSP board/encoder interface board/PWM amplifier board

•CCD camera

•IR distance sensor

•Accelerometer

•Inclinometer

•motors and encoder


Design,Modeling and ControlThe design team considered:

standardization of components to reduce coststructural rigiditysensor and board placement

A CAD model was created and inertia parameters determinedA Model-Based Control was designed and implemented

balance control using rate gyro and inclinometervelocity and heading controlwall-following using IR sensors

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generalized coordinates

equations of motion

where

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Linearized Model and LQR Balance Control


One of the more interesting aspects of this project, and one that is rarely if ever taught in control courses, is the sensingof the vertical angle of the Segbot. This angle was determined by using two sensors: a tilt sensor and a solid-state rate gyro. The tilt sensor is a Crossbow CXTLA01, which is a single axis sensor with an accuracy of ±20 degrees.The rate gyro is a Silicon VSG CRS02 with an accuracy of ±150 degrees/sec. Either device alone can be used to sense the vertical angle in theory. However, in practice, both sensors are necessary to achieve acceptable performance.

Vertical Angle Measurement and Sensor Fusion: The Complementary Filter

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Sensor Issues

The tilt sensor measures an angle relative to the direction of gravity. It has excellent steady state characteristics, however, it develops significant phase lag with increasing frequency. The slow response of the tilt sensor is problematic for this system because of the need for accurate dynamic as well as static measurements.The rate gyro measures angular rate; the vertical angle is then determined by integration. While the gyroscope has excellent dynamic response, a problem with all gyroscopes is that there is a bias near DC that causes drift in the angularmeasurement.


Sensor FusionA sensor-fusion solution used by the students was to combine the measurements of the two sensors, taking advantage of the low frequency characteristics of the tilt sensor and the high frequency characteristics of the gyroscope. Two methods were used to determine the vertical angle from the two sensor measurements:

A complementary filterA Kalman filter.

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Complementary Filter


Motion Control

In order to control heading and speed the wheel variables are mapped to the linear and angular speeds and angular orientation:

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These expressions can be inverted to yield offsets to the wheel variables to control speed and heading:


The Results

Spin in Place Wall Following using IR Sensor

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Network of Second-Generation Segbots


Tracking Using the CCD Camera

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Second Example: The Segmonster

The Segmonster is a robot designed to ride a SegwayHuman Transporter (SHT)


The Design Team and Design Philosophy

•The Segmonster project was begun by two undergraduate students as a summer project following the mechatronics course and completed as an MS thesis project.

•The design philosophy is that the Segmonster should have access to only the information that is available to a human rider.

•Therefore no special instrumentation was added to the SHT

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• The robot rider controls the Segway HT just as a human rider, by inclining its torso to control forward and reverse velocity and by rotating the handle grip to turn. • This led to several important design constraints

Segmonster


Design Constraints

• Attaching the robot firmly to the Segway so that it does not fall off or damage the Segway

There are three standard mounting points on either side of the operator's platform of the Segway. These are normally used to hang bags or other Segway accessories over the wheels. These were the only mounting points that could be used so as not to void the manufacturer's warranty.

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• Engaging and disengaging the foot pressure sensors

The footpads on the Segway contain pressure sensors that indicate the presence (or absence) of a rider. The Segway cannot be turned on if any weight is on these footpads. Therefore the Segmonstercould not be designed simply to sit on the Segway footpads, but had to be mounted on a platform over the footpads, attached to the standard mounting point as above, in such a way that it could engage the pressure sensors (with sufficient weight) after power to the Segway is turned on.

Design Constraints


• Selecting and placing sensors to obtain feedback on position and velocityThe Segmonster is equipped with

• Four optical encoders• One infrared (IR) range sensor• One CCD color camera

Two of the optical encoders are mounted to dummy wheels that ride on the Segway wheels to determine velocity and relative orientation of the Segway. A third encoder is mounted on the robot arm to determine its position and the fourth is used for the motor that actuates the handle grip for turning. The IR range sensor is used for obstacle detection and the CCD camera is used to collect visual data for navigation and terrain following.

Design Constraints

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Segmonster Control

•The Segmonster controller resides on a TI C6713 Digital Signal Processor. •A pair of daughter cards designed at the University of Illinois Control Systems Lab provide interface to all sensors as well as digital-to-analog output to the motor amplifiers. •The Segmonster can be controlled manually through a wireless communication card, or autonomously using it's on-board vision system.


Segmonster ControlThe Segmonster has several integrated controllers

A modified PID-velocity control loopA PID turning controllerA sidewalk tracking controller using a vision sensor

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Some Segmonster Videos

Fast Turn Slow Turn

Inside


Some Conclusions

Undergraduate students are an extremely capable and often untapped resourceSolving real control problems rather than textbook problems is a tremendous motivator and well within the grasp of many studentsProject-Based Control is a holistic method of education that offers advantages that cannot be obtained in the classroom.

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QUESTIONS?

THANK YOU!

Documents

Project-Based Control Education · 2006. 6. 30. · Industrial applications of control are increasingly large-scale, ... A Kalman filter. 10 IFAC Symposium on Advances in Control