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General Programming Strategy

• We use various functions to run our programs (so we can reuse code and change parameters, as required)
• We have created a selection program which allows us to quickly and efficiently choose missions (or even re-run missions quickly) during matches. Audible sounds and meaningful EV3 screen messages allow the user to select programs with ease
• By using gear lash removal before each movement, the acceleration and deceleration movements when starting and stopping a movement, our own error-corrected move block, and Proportional Integral Derivative line following, we are able to achieve more consistent and repeatable robot movement
• We regularly use functions, also known as subroutines, which allows us to reuse code whenever possible and to keep our program sizes manageable.
• We annotate our work to help us debug programs and to better understand the purpose of each line of code
• We make frequent use of our square up function which allows the robot to position itself perpendicularly to any line (from virtually any angle of attack)
• Our functions and parameters are given descriptive and meaningful names to allow us to easily understand what our programs are doing
• Within all of our major movement functions (such as our error-corrected move block and PID line following block), we have a function inside that is constantly checking if a certain exit condition is met. When that exit condition is met, the program immediately exits that loop causing the robot to advance to the next robot maneuver. For example, stop the robot when one of the light sensors a black line.
• Our "Check-Abort" function constantly checks whether the EV3 up arrow button is pressed. The robot operator can interrupt missions at any time and still stay within the overall selection program to avoid the need to exit the program and find the next program or mission.
• When accelerating from a stationary position, our robot uses Ctrl-Z-designed acceleration and deceleration feature s to minimize the likelihood of wheel slip. This provides for greater repeatability of the robot’s movements.
• As well, instead of using standard calibrated values, we use raw light sensor values for more granularity. Our calibration program collects the lowest and highest light readings the robot would see. Then, based on those, we scale any light readings to a usable range where 0 is black and 100 is white.

Program Hierarchy

In the interest of maximizing programming efficiency, we use subroutines whenever possible. Subroutines are used for typical robot movements, like line following, squaring to a line, error-corrected movements, etc., as well as for entire missions. The use of subroutines allows us to re-use programming code and enjoy the benefits of an efficient mission selection program. This diagram to the left illustrates the great extent to which Ctrl-Z re-uses programming code.

Function Examples

Main Selection Program

This selection program allows us to quickly and efficiently switch programs/missions during the two-and-a-half minute match. Our selection program contains functions, each containing one of our missions. The user of the robot simply starts the selection program and clicks the centre button to start the first mission. Then, when the mission finishes, the robot automatically advances to the next mission and waits for the user to click the centre button to run the appropriate mission. In case one needs to go backwards or forwards through the list of missions, the program accommodates that by allowing the user to navigate with the left and right arrow buttons.

Square Up

We have created a function that makes the robot completely perpendicular to the edge of a black line. Each light sensor corresponds with a motor. The robot drives up to the line and has the light sensor check the reflected light values. If the light sensor sees a value of less than 50 (black), it will tell the motor to move towards a value greater than 50 (white). It does this for both motors while for a set amount of time while slowly decreasing in power, until the robot becomes completely perpendicular to the edge of the line.

Full Programming Documentation (Click to See Full Code!)