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Design of the Control Strategy

System

Dynamics

Environmental Disturbances

Control

StrategyGoal Output

Feedback

Sensors

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Linebot Control Strategy

System

Dynamics

Environmental Disturbances

motion_controlGoal Output

Feedback

decision

Task decision() monitors the sensors and issues a control signal

dirto task motion_control(). The signal dir is a code -1,0,1,2 to

represent turn left, go straight, turn right, or stop. Task

motion_control() issues the steering commands to the bot.

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Design of the Control Strategy

SystemDynamics

Environmental DisturbancesGoal2

Output

feedback

navigate

line_follow

Goal1

Goal 1: Follow the line

Goal 2: Navigate to desired position

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Task Structure line_follow() This is the old

motion_control used in linebot to controlthe lateral line-following motion.

navigate() a new task that takes over at

an intersection. It decides which way toturn and executes the motion control toeffect turning.

feedback() is the old decision() task. Itmeasures the sensors and changes thedir variable.

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Task Structure Continued The tasks navigate and line_follow

cannot function at the same time. Iftask feedbacksignals that the bot hasreached an intersection, line_follow

must be stopped and navigate must bestarted.

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Variables

What variables do we need? We alreadyhave one which we called dir-- it is issued byfeedback() which assigns values to indicate:turn right, turn left, go straight, and at an

intersection. The master control is issuing a command to

go to some final destination. This must bekept as a variable.

What intersection are we at? Our decision toturn right or left at an intersection dependsupon: Where we are and Where we want togo.

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Navigation Strategy Suppose we can count the

intersections. Depending upon the intersection

number, certain destinations will only beachieved if we turn right, others if weturn left.

We could use a bunch of if statementsto branch to the decision rules for each

intersection, or we could use a switchcontrol structure.

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The switch control structureswitch(x)

{case 1:

// do something when x is 1

break;

case 2:

// do something when x is 2

break;

case 3:

// do something else when x is 3

break;

default:

// do this when x is not 1,2,or 3

break ;

}

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This is equivalent to the following

if statements

//put default statement if x is not 1,2, or 3

if(x==1) //add statement executed when x is 1

if(x==2) //add statement executed when x is 2

if(x==3) //add statement executed when x is 3