allwpilib/eclipse-plugins/edu.wpi.first.wpilib.plugins.cpp/resources/templates/examples/UltrasonicPID/src/Robot.cpp

#include "WPILib.h"

/**
 * This is a sample program to demonstrate the use of a PID Controller with an ultrasonic
 * sensor to reach and maintain a set distance from an object.
 *
 * WARNING: While it may look like a good choice to use for your code if you're inexperienced,
 * don't. Unless you know what you are doing, complex code will be much more difficult under
 * this system. Use IterativeRobot or Command-Based instead if you're new.
 */
class Robot: public SampleRobot {
	AnalogInput ultrasonic; //ultrasonic sensor
  RobotDrive myRobot;
	PIDController pidController;

public:
	const int ultrasonicChannel = 3; //analog input

	//channels for motors
	const int leftMotorChannel = 1;
	const int rightMotorChannel = 0;
	const int leftRearMotorChannel = 3;
	const int rightRearMotorChannel = 2;

	int holdDistance = 12; //distance in inches the robot wants to stay from an object

	//proportional, integral, and derivative speed constants
	//DANGER: when tuning PID constants, high/inappropriate values for pGain, iGain,
	//and dGain may cause dangerous, uncontrollable, or undesired behavior!
	const double pGain = 7, iGain = .018, dGain = 1.5;

	//conversion factor specific to the sensor being used. For this sensor,
	//the sensor returned values from 0.0V to 5.0V with a resolution of 9.8mV/in.
	const double VoltsToInches = 0.0098;

	//internal class to write to myRobot (a RobotDrive object) using a PIDOutput
	class MyPIDOutput: public PIDOutput {
	public:
    RobotDrive &rd;
		MyPIDOutput(RobotDrive &r) : rd(r)
		{
			rd.SetSafetyEnabled(false);
		}
		void PIDWrite(float output) {
			rd.Drive(output, 0); //write to myRobot (RobotDrive) by reference
		}
	};

	Robot() :
		//make objects for sensor and drive train
		ultrasonic(ultrasonicChannel),
		myRobot(new CANTalon(leftMotorChannel), new CANTalon(leftRearMotorChannel),
						new CANTalon(rightMotorChannel), new CANTalon(rightRearMotorChannel)),
		//ultrasonic (AnalogInput) can be used as a PIDSource without modification,
		//PIDOutput is an instance of the internal class MyPIDOutput made earlier
		pidController(pGain, iGain, dGain, &ultrasonic, new MyPIDOutput(myRobot)) {}

	/**
	 * Runs during autonomous.
	 */
	void Autonomous()
	{

	}

	/**
	 * Drives robot to set distance from an object using PID control and the ultrasonic
	 * sensor.
	 */
	void OperatorControl() {
		pidController.SetSetpoint(holdDistance * VoltsToInches); //set setpoint to 12 inches

		//set expected range to 0-24 inches; e.g. at 24 inches from object go full
		//forward, at 0 inches from object go full backward.
		pidController.SetInputRange(0, 24 * VoltsToInches);

		while (IsOperatorControl() && IsEnabled()) {
			pidController.Enable(); //begin PID control
		}
	}

	/**
	 * Runs during test mode.
	 */
	void Test()
	{

	}
};

START_ROBOT_CLASS(Robot)