1. Using Encoders to go Straight
Limit drifting when trying to go straight
In this section we will look at if
else
Variables and types
Applying all of this to help the robot go straight

2. Pseudo Code (What we are trying to get the robot to do)
While the robot has not reached the destination
If the left motor has gone farther, slow the left motor and have right motor go at speed
If the right motor has gone farther, slow the right motor and have the left motor go at speed
If the motors are the same, have both motors go at speed

3. If Statements
When your robot reaches an if Statement in the program, it evaluates the condition contained between the parenthesis.
If the condition is true, any commands between the braces are run.
If the condition is false, those same commands are ignored.
Very similar to how a while loop works, but does not repeat the code!

4. Going Straight: Translating to Code
Pseudo Code While the robot has not reached the destination If the left motor has gone farther, slow the left motor and have right motor go at speed If the right motor has gone farther, slow the right motor and have the left motor go at speed If the motors are the same, have both motors go at speed

5. If-else statements
The if-else Statement is an expansion of the basic if Statement.
The “if” section still checks the condition and runs the appropriate commands when it evaluates to true
Using the “else” allows for specific code to be run only when the condition is false.
Either the “if” or the “else” branch is always run; no more, no less.

6. Chaining if..else if ..else

7. Implementing if..else

8. But…
If the motors are not close in their Power to Speed then the difference between 50 and 63 might not be sufficient.
So it will take some tweaking.
Rather than changing the 63 to another value when modifying the ‘at speed’ needed, you can use variables.

9. RobotC Variables int float string char bool
Stores integer values: 5, 0, -100
float
Stores floating point (real) values: 3.01, -5.21, 0
string
Stores words: “Hello World”
char
Stores single characters: “A”,
bool
Stores Boolean (true, false) values

10. Code After Using Variables for Speed Values
Declaring the variables.
type name
Initialize the variables.
Try modifying the fullSpeed and slowerSpeed values to see how if changes the robot behavior.

11. Summary motor[] SensorValue[] wait1Msec() while if if..else Conditions
Conjunctions
Motors and Sensor
Quadrature Encoder
Strategies on going straight
Timing vs. distance

12. Driving Straight Activity
Use the Clawbot
Driving Straight II using encoders
When complete, demo to Smith, continued on Physical Movement Challenges, and installing Shaft Encoders.