1. Design of the Control Strategy
Environmental Disturbances
Control
Strategy
System
Dynamics
Goal
Output
Sensors
Feedback

2. Nursebot Control Strategy
Environmental Disturbances
System
Dynamics
Goal
motion_control
Output
decision
Feedback
Task decision() monitors the sensors and issues a control signal
dir to 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.

3. Design of the Control Strategy
Goal2
Environmental Disturbances
navigate
line_follow
System
Dynamics
Output
Goal1
feedback
Goal 1: Follow the line
Goal 2: Navigate to desired position

4. Task Structure
line_follow() This is the old motion_control used in linebot to control the lateral line-following motion.
navigate() a new task that takes over at an intersection. It decides which way to turn and executes the motion control to effect turning.
feedback() is the old decision() task. It measures the sensors and changes the dir variable.

5. Task Structure Continued
The tasks navigate and line_follow cannot function at the same time. If task feedback signals that the bot has reached an intersection, line_follow must be stopped and navigate must be started.

6. Variables
What variables do we need? We already have one which we called dir-- it is issued by feedback() 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 be kept as a variable.
What intersection are we at? Our decision to turn right or left at an intersection depends upon: Where we are and Where we want to go.

7. Navigation Strategy Suppose we can count the intersections.
Depending upon the intersection number, certain destinations will only be achieved if we turn right, others if we turn left.
We could use a bunch of if statements to branch to the decision rules for each intersection, or we could use a switch control structure.

8. The switch control structure
switch(x) {
case 1:
// do something when x is 1
break;
case 2:
// do something when x is 2
case 3:
// do something else when x is 3
default:
// do this when x is not 1,2,or 3
break ; }

9. 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