Embedded control and softwarefor Autonomous System

8/3/2019 Embedded control and softwarefor Autonomous System

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Content

ECS Introduction

Embedded control system design and

algorithm

Embedded software

Timing constraints with embedded

software


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Embedded control systemy Control physical systems output

y By setting physical systems input (cause-effect relationship)

y Tracking

y E.g.

y Cruise c

ontr

ol

y Thermostat control

y Disk drive control

y Aircraft altitude control

y Difficulty due to

y Disturbance: wind, road, tire, brake; opening/closing door

y Human interface: feel good, feel right


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Tracking

Embedded control system divided into mainly 2 categories:1. Open loop control system

2. Close loop control system


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Open loop control systemy Plant

y Physical system to be controlledy Car, plane, disk, heater,

y Actuator

y Device to control the planty Throttle, wing flap, disk motor,

y Controller

y Designed product to control the plant


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Open loop control systemy

Outputy The aspect of the physical system we are interested in

y Speed, disk location, temperature

y Reference

y The value we want to see at outputy Desired speed, desired location, desired temperature

y Disturbance

y Uncontrollable input to the plant imposed by environmenty Wind, bumping the disk drive, door opening


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Characteristics ofOpen loop systemy Feed-forward control.

y Delay in actual change of the output.

y Controller doesnt know how well thing goes.

y Simple.

y Best use for predictable systems.


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Characteristics ofClose loop system

y Feed-Back control.

y Delay in actual change of the output.

y Controller know how well thing goes.

y Typical.y Mostly use for real time systems.


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Embedded control system design

y Design of control system is a specific example of engineering design.

y The goalof control engineering design is toobtain.....

a) Configuration

b) Specification

c) Identification of key Parameter.. To meet an actual need.

y Design arranged into 3 groups

a) Establishment of goals and variable to be controlled, and definitionof specification against which to measure performance.

b) System definition and modeling.c) Control system design and integrated system simulation and analysis


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Control system design process (Algorithm)

Establish the c

ontr

olgo

als

Identify the variables to be controlled

Write the specification

Establish the system configuration

Obtain a modelof process, the

actuator, and the sensor

Describe a controller and select key

parameter to be adjusted

Optimize the parameters and analyze

the performance

3) Control

system design,

simulation, and

analysis .

2) System

definition and

modeling.

1) Establishment

of goals, variables

to be controlled,

and specification.

If the

performance

does not meetthe

specification,

then iterate the

configuration

If meet then finalize the design


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General control system analysis

y Objective

Causing output to track a reference even in the presenceof

Measurement noise

Model error

Disturbancesy Metrics

Stability

Output remains bounded

PerformanceHow well an output tracks the reference

Disturbance rejection

Robustness

Ability to tolerate modeling error of the plant


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Performance (generally speaking)

y Rise time

Time it takes form 10% to 90%

y Peak time

y Overshoot

Percentage by which Peak exceed final value

y Settling time

Time it takes to reach 1% of final value


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Future evolution of control system

robotics

FixedautomationHigh

HighFlexibility

Autonomy

Low

Low

Extended tools Control system programmable

Digital

control

system

Improvements

Vision

Human-machine

interface

supervisory

control

Improvements

Vision

Sensor

Language

Artificial

intelligence

Extensive flexibility

and autonomy

Power tool

Hand tool


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Goal of control system

y Extensive flexibility.y High levelof autonomy.

y Adaptability.

y Improved performance of a system.

y Increased productivity.

y Reliable

Some functional research areas concentrating on Artificial

intell

igence, senso

r integratio

n, co

mputer visio

n will

makesystem more universal and economical.


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Embedded software and Timing

constraint


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Embedded software

y Software with a principal role of interacting with the

physical world must, of necessity, acquire some properties

of the physical world. It takes time. It consumes power. It

does not terminate (unless it fails). It is not the idealized

procedures of Alan Turing.

y An arrogant view of embedded software is that it is just

software on small computers.

y Embedded software = RTOS + Application program.


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Embedded programming abstraction

y Timeliness

y Concurrency

y Interfaces

y

Livenessy Reactivity

y Heterogeneity

They are essential to the correctness of a program. But notsufficient to realize the right mapping from input data to

output data.


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y Timelines : The issue is not just that execution takes time.

Even with infinitely fast computers, embedded software

would still have to deal with time because the physicalprocesses, with which it interacts, evolve over time.

y Concurrency : Embedded systems rarely interact with

only a single physical process. They must simultaneouslyreact to stimulus from a network and from a variety of

sensors, and at the same time, retain timely control over

actuators. This implies that embedded software is

concurrent.

y Interface : For embedded software to benefit from a

component technology, that component technology will

have to include dynamic properties in interface definitions.


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y Liveness : In embedded systems, liveness is a critical

issue. Programs must not terminate or block waiting for

events that will never occur. In embedded computing,however, terminating programs are defective. The term

deadlock pejoratively describes premature termination

of such systems. It is to be avoided at all costs.

y Reactivity : Reactive systems are those that react

continuously to their environment at the speed of the

environment.

y Heterogeneity : Heterogeneity is an intrinsic part of

computation in embedded systems. They mix

computational styles and implementation technologies.


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Programming Languages Used in

New Embedded Designs

0.00% 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00%

Others

Assembly

Java

C#

C++

C


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Commercial operating system used

in embedded software design

0.00% 5.00% 10.00% 15.00% 20.00% 25.00% 30.00%

Others

Palm

Green Hills

Symbian

Wind River

Microsoft Emb.


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Embedded software: Modeling

Timing constraint

A timing constraint:

Defined with respect to some event.

An event:

Can occur at an instant of time May also have duration

Generated either by the system or its environment

Events in real time system

Stimulus Events

Response Events


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Classification ofTimingConstraints

Different timing constraints can broadly be classified into:

Performance constraints.

Behavioural constraints.

Both performance and behavioural constraints can be

classified into:

Delay Constraints

Deadline Constraints

Duration Constraints


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252503/08/10 2525

Timing Constraints

Behavioural ConstraintsPerformance Constraints

Delay Deadline Duration

RR SR RR SR

Delay Deadline Duration

RS SS RS SS


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References

y To appear in Advances in Computers (M. Zelkowitz, editor),

Vol. 56, Academic Press, London, 2002.

y E Balarin, M. Chiodo, E Giusto, H. Hsieh, A. Jurecska, L.

Lavagno, C. Passerone, A. Sangiovanni-Vincentelli, E.

Sentovich, K. Suzuki, and B.Tabbara. Hardware-SoftwareCo-Design of Embedded Systems: The Polis Approach.

Kluwer Academic Press, 1997.

y G. Berry, P. Couronne, and G. Gonthier, The synchronous

approach to reactive and real-time systems, Proc. IEEE,vol. 79, Sept. 1991.

y Real time system Prof. Rajib Mall

y Modern control system Dorf,Bishop

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Embedded control and softwarefor Autonomous System