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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
