Virtual Plant Tour

• Stamping– http://www.infinitelooper.com/?

v=bYCc3toOHdc&p=n#/27;109– http://www.youtube.com/watch?v=bYCc3toOHdc

• Vision– http://www.youtube.com/watch?

v=QXbpxHeeBAE

SE-3910 - Dr. Josiah YoderSlide style: Dr. Hornick

Much Material: Dr. Schilling1

SE-3910Real-time Systems

• Week 1, Class 3 [DRAFT]– Virtual Plant Tour– Introductions– Quiz 1 – The first real quiz!– Real-Time System Terminology (cont.)

• Classifications

– Response Time & Latency– Common Approaches & Misconceptions

SE-3910 - Dr. Josiah YoderSlide style: Dr. Hornick

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Real-Time SystemTerminology

• Soft– Not destroyed by failure to meet response time

• Hard– Destroyed by failure to meet a single deadline

• Firm– Destroyed by failure to meet multiple deadlines

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Discussion• On your own: Write which kind of real-time system is being used• With your partner, discuss & fill in the explanations

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System Classification Explanation

Video Surveillance System for Car Dealership

Laser welding robot to construct car frames

2 player air hockey game on game console

Timing Terminology

• Event– A jump in the program counter

• Synchronous– Predicatable. Scheduled. In sync with other events

• Asynchronous– Unpredictable. Unscheduled. External requests

• Aperiodic – No fixed period, asynchronous• Sporadic – Extremely infrequent and aperiodic• Punctual – Neither early nor late

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Digibot Circuitry

• A deterministic system

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Five Misconceptions(paraphrased from Laplante and

Ovaske)• Real-time Systems are fast• All you need is

– a real-time OS– a rate-monotonic scheduler– lots of scheduling theory

• We’ve figured out how to make real-time systems

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Muddiest Point

• What was the muddiest point in this lecture? (least clear point)

• Would you like to have an outcomes slide at start/end of lecture notes?

• How about online? (Which do you prefer more?)

SE-3910 - Dr. Josiah YoderSlide style: Dr. Hornick

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Response Time & Latency

• Response time– The time between input events and all possible

output events

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Measure your class-mate’s response time

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Instructions• Part 1

– One partner should hold the stick while the other partner places their hand around the tape at the end of the stick. Hands should be approximately 1” from the stick.

– At some point in the future, the partner drops the stick. Read the numbers off of the stick for response time and record them in the GoogleDoc.

– Repeat the experiment 3 times

• Part 2– One partner should hold the stick while the other partner places their hands

around the tape at the end of the stick. Hands should be approximately shoulder width apart.

– At some point in the future, the partner drops the stick. Read the numbers off of the stick for response time and record them in the GoogleDoc.

– Repeat the experiment 3 times

• Partners swap roles…SE-3910 - Dr. Josiah Yoder

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Human Systems• Sensory:

Inputs: Both external & internalOutputs: Nerve signals

• Nervous:Inputs: Nerve signalsOutputs: Intelligent nerve signals

• Motor:Inputs: Nerve signalsOutputs: Precise & powerful motion

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Human Nervous System

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Nerve Speeds

• Speed of signal transmission along nerve fibers– depends on diameter of fiber & presence of myelin– large fibers have more surface area for signals

• Speeds– small, unmyelinated fibers = 0.5 - 2.0 m/sec– small, myelinated fibers = 3 - 15.0 m/sec– large, myelinated fibers = up to 120 m/sec

• Functions– slow signals supply the stomach & dilate pupil– fast signals supply skeletal muscles & transport sensory signals

for vision & balanceSE-3910 - Dr. Josiah Yoder

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System Diagram

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DelaysDistance from stick to eyes

Speed of lightNeuron distance between eyes and brain stem

.1 metreNeuron distance between brain and hands

1 metreTime for hands to close

Hands can move up to 100 mph (44 metres per second)

Rest of time will be latency in the brain

299 792 458 m / s (google)

Latency vs. Processing Time?

• http://javidjamae.com/2005/04/07/response-time-vs-latency/

• Latency + Processing Time = Response Time(One view)

• What response time can we guarantee with our system?– What is epsilon?

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