ME375 Intro - 1

ME 375System Modeling and Analysis

Prof. Cagri SavranSchool of Mechanical EngineeringPurdue UniversityME 1087, 494-8601, savran@purdue.edu

System Dynamics & Control

It’s everywhere… How do you balance a vertical stick?

School of Mechanical EngineeringPurdue University

ME375 Intro - 2

Basic “block diagram” model

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SystemController(Stick)(Brain)

Actuator(Hand)

Sensor(Eye)Σ

Feedback(Nerves)

+

-

Desired response(Brain)

Comparison of desiredand actual response

(Brain)

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ME375 Intro - 4

Course Objectives

1) Introduce systematic and unified modeling of lumped dynamic systems using first principles.

2) Provide mathematical tools for analysis and performance prediction of engineered systems.

3) Provide introduction to design of feedback controllers to achieve closed-loop stability and specified system performance.

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ME375 Intro - 5

Course Overview

• Integrating Modeling, Analysis and Control of Machines and Physical Systems

• Multi-Energy Domain System Modeling• Standard Format and Procedure • System Analysis (in time and frequency domains)• Feedback Control

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Course Overview

• Text – System Dynamics, by Palmavailable via CourseSmart on-line: http://www.coursesmart.com/

• References - see syllabus• Homework - must be individual effort• Matlab - necessary to complete homework• Exams - two midterm exams and one final• Grading - see syllabus• Course Web site:

http://www.itap.purdue.edu/tlt/blackboard/index.cfmlogin using Career Account username and password, then select ME 375

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What is a Model?

• A set of assumptions?• A diagram?• A set of equations?• A set of plots?• A simulation?

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Why do we need a Model?

• To ensure reliable performance• To prevent failures• To apply feedback control

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Example

• Blood Sampler (Lancet)

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System Characteristics

• Simple vs. Complex• Lumped vs. Distributed• Linear vs. Nonlinear• Time-invariant vs. Time-varying• Continuous vs. Discrete

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ME375 Intro - 11

Dynamic Systems

• Models are the same regardless of the physical domain:

• We only have to understand one model, but we have four different systems!

= = =

euy Charge

fuy displ. Transl.

uy displ.Angular

dtdqu

y

Pressure

y y y u(t)

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Course OutlineIntroduction

Components/elements

Connections/interconnects

Mechanical

Electromech.

Electrical

HydraulicThermal

Input/output vs.state-variable

models

Time-frequencytools of

system analysis

Feedbacksystem design