androidbasedgreenhousemonitoring(and harvesting ...devendra/pres114050004.pdf · 2 system design 3...

IntroductionSystem Design

Functional RequirementsRisk Analysis

Android Based Greenhouse Monitoring (And

Harvesting) Using Accurate And Automated BotGuidance System

Devendra Bhave (114050004)Mohd Vasimuddin (114050007)Meenakshi Verma (123050014)Mukund Lahoti (123050018)

September 28, 2012

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Contents

1 Introduction

2 System Design

3 Functional Requirements

4 Risk Analysis

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Wish List

Automated greenhouse monitoring

Automated harvesting

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Requirements

Bot guidance system

Battery charging facility

Right tools

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Environment Description

Greenhouse Greenhouse

Android Phone

In

t

e

r

n

e

t

WiFi Access Points

WiFi has speed and range advantage over ZigBee and Bluetooth.

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Bot Description

Android Phone

FireBird Bot

Greenhouse

Robotic Arm

Circular Saw

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Bot Guidance System

Location Error: Difference between physical location of the Bot inreal world and location known to Bot guidance system

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Bot Guidance System


Desired properties of the Bot guidance system:

1 Accurate: Fixed known bound on Bot location error

2 Automated: No human intervention needed for Bot navigation

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Bot Guidance System


Desired properties of the Bot guidance system:

1 Accurate: Fixed known bound on Bot location error

2 Automated: No human intervention needed for Bot navigation

Our design is both accurate and automated.

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Bot Guidance System

Guidance System knows precise location of the Bot.

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Bot Guidance System

Guidance System knows precise location of the Bot.

Design offers mathematical guarantee that location error will neverexceed constant bound δmax no matter how long you use it.

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Relevant Terminologies

Accuracy: the degree of closeness of measurements of a quantityto that quantity’s actual (true) value [1]

Precision: the degree to which repeated measurements underunchanged conditions show the same results [1]

bb

bb

bb b

b

High accuracy, Low accuracyLow precision High precision

Accuracy

Precision

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Characterizing Location Error

Sources of location error:

Quantization error in wheel counter

Missed wheel counts

Wheel circumference measurement error

Slight differences in wheel diameters

Small errors accumulate over time to catastrophic level.

Location error, E

= f (distance travelled)= κ · d

Distance

Loc

atio

nE

rror

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Design of Bot Guidance System

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Design summary:

Map of arena is precisely known

Use white line to follow path

Add checkpoints to mitigate location errors

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Design summary:




Checkpoint: A co-ordinate on the map whose location is accuratelyknown.

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Design summary:




Checkpoint: A co-ordinate on the map whose location is accuratelyknown.

Bot senses checkpoint when it passes over it and updates itscurrent location eliminating location error.

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Source of Error in Detecting Checkpoint

Checkpoint sensing is not perfect. It introduces small amount oflocation error ǫ.

This error is due to delay between instant when the Bot passesover checkpoint and the instant when guidance system updatesBot location.

If Bot is moving with speed 10 cm/sec and delay in updating itslocation is 20 msec, error ǫ is 2 mm.

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Error Characteristics Of Bot Guidance System

b b bb

Loc

atio

nE

rror

Path

ǫ

δmax

Minimum location error present at any time is constant ǫ

Maximum location error that may occur is constant δmax

ǫ ≪ δmax

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Precision Of Bot Guidance System

Let, Dmax be maximum distance between two consecutivecheckpoints along any path

∴ δmax = κ · Dmax

Note that δmax is constant for given placement of checkpoints.Thus, upper bound on error is constant.

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Error Tolerance Of Bot Guidance System

Let, Dmin be minimum distance between two consecutivecheckpoints along any path

b b b

Dmin

Error tolerance is upto Dmin.

Maximize Dmin to increase error tolerance, but minimize Dmax toimprove accuracy.Dmax = Dmin is optimal design choice.

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Correctness Parameters of Bot Guidance System

Accuracy: ǫ

Precision: δmax

Error Tolerance: < Dmin

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Implementation of Checkpoints

Desired properties of checkpoint:

Should be immovable

Should be inexpensive

Should need minimum additional hardware for detection

Should consume as low power as possible

Bot must detect it reliably

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Should be immovable





Recall that for white line follower, left sensor = White, middlesensor = Black, right sensor = White is impossible entry.

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Should be immovable






That’s our checkpoint!

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Should be immovable






That’s our checkpoint!

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Implementation of Bot Guidance System

Bot Guidance System has

the map

precise current location of the Bot

initial orientation of the Bot - E, W, N, S

We build automated Bot guidance system based on graphalgorithms to move the Bot to any desired location along the white

line.

It is possible to implement service primitive goto(x, y).

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Implementation of Recharge Station

HornTail

Metallic Wool Contact Pads

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Bot Operation Modes

Bot operates in one of the three operation modes:

1 Automatic - Automatic Bot guidance system controls the Bot

2 Manual - User controls the Bot remotely (Project exists one-yantra)[2]

3 Transition - Intermediate mode when switching from manualto automatic

Bot status known to automatic guidance system:

1 Automatic - guidance system knows location and orientationof the Bot

2 Manual - neither location nor orientation of Bot is known toguidance system

3 Transition - guidance system takes user’s help to learn currentBot location and orientation

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FSM for Bot Operation Modes

Automatic

TransitionManual

Error or user request

User request

Checkpoint detection

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FSM for Bot Operation Modes

Automatic

TransitionManual

Error or user request

User request

Checkpoint detection

In transition mode, user manually maneuvers the Bot to nearestcheckpoint. User tells Bot guidance system which checkpoint itshould expect next. As the Bot passes over the checkpoint,guidance system knows current location and orientation and takesthe control of the Bot to itself, switching to automatic mode.

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Functional Requirements

Automated Bot Guidance System:

1 Maneuver the Bot automatically

2 Support goto(x, y) primitive

3 Guarantee accuracy

Bot Recharge Station:

1 Reliable electrical contact with the Bot

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Functional Requirements

Greenhouse Management:

1 Semi automatic greenhouse monitoring: Take photos of alltroughs periodically and send them to user

2 Semi automatic harvesting:

2.1 User points out location on the map on one’s phone. Botshould go there automatically.

2.2 Switch the Bot in manual mode and let user harvest the cropremotely.

2.3 Bot returns to automated mode with user assistance.

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Risk Mitigation

Risk #1 Error in checkpoint detection

Automated guidance system knows location of nextcheckpoint in the path (Say D units away)

Location error is bounded by constant δmax

Next checkpoint must be detected within the range[D − δmax ,D + δmax ]

No checkpoint detected till distance > (D + δmax) ⇒Missed checkpoint

checkpoint detected distance < (D − δmax) ⇒ Falsecheckpoint detection

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Risk Mitigation

Risk #2 Error in white line following Certain cases in whilefollowing white line are errors. (e.g. all sensors detect black)

For Risk #1 and Risk #2, switch the Bot in manual mode andalert user remotely.

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Risk Mitigation

Risk #3 Battery is lowGo to recharge station and wait there till battery is completelycharged.

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Risk Mitigation

Risk #4 Unauthorized user controls greenhouse

Use secure network protocol and authenticate user beforeconnection.

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Obeservations

Problem of designing accurate and automated Bot guidancesystem is fundamental in nature for greenhouse applications.

All future greenhouse projects can use this system to avoid costlyor complex solutions.

Applications who need very accurate Bot positioning just need toplace extra checkpoints at desired places.

Thank You!

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References

Accuracy and precision.http://en.wikipedia.org/wiki/Accuracy_and_precision.

E-yantra website.http://www.e-yantra.org.

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http://en.wikipedia.org/wiki/Accuracy_and_precision

http://www.e-yantra.org

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