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//core of the PID loop here, calculate the necessary motor power
motorPower = kP * error + kI * integral + kD * derivative;
///keep motor power variable in proper range, 0-1
if (motorPower > 1) motorPower = 1;
if (motorPower < 0) motorPower = 0;
//control the slew rate (dampen voltage differences), limits harsh acceleration
float slewRate = 0.05f;
if (motorPower > prevMotorPower + slewRate) {
motorPower = prevMotorPower + slewRate;
}
if (motorPower < prevMotorPower - slewRate) {
motorPower = prevMotorPower - slewRate;
}
//apply motor voltages
LeftMotors.spin(forward, 12 * motorPower, volt);
RightMotors.spin(reverse, 12 * motorPower, volt);
//update final variables
prevMotorPower = motorPower;
prevError = error;
//don't hog CPU
wait(20, msec);
}
return 0;
}
int drivePID() {
//drive straightforward with driveDistance as the distance, in degrees (for now)
//forward PID constants:
float kP1 = 0.0048;//.003 and 0 for other two
float kI1 = 0.00003;
float kD1 = 0.013;
//turning PID constants:
float kP2 = 0.001;
float kI2 = 0.00;
float kD2 = 0.00;
//other variables for forward PID
float error1 = 0;
float integral1 = 0;
float derivative1 = 0;
float prevError1 = 0;
//other variables for turn PID
float error2 = 0;
float integral2 = 0;
float derivative2 = 0;
float prevError2 = 0;
//motor power variables
float motorPower = 0;
float prevMotorPower = 0;
//lists
std::vector<int> errorHistory; //keep track of error over time
std::vector<float> powerHistory; //keep track of motor power over time
int time = 0;
float currentDist = 0; //the distance the robot is from its starting point
RightMotors.setPosition(0, degrees);
LeftMotors.setPosition(0, degrees);
while(true) {
currentDist = (RightMotors.position(degrees) + LeftMotors.position(degrees)) / 2;
//calculate error / integral / derivative, of error vs time graph
error1 = driveDistance - currentDist;
if (std::abs(error1) < 200) {
//weigh the integral double when error < 50
if (std::abs(error1) < 50) {
integral1 += error1 * 2;
} else {
integral1 += error1;
}
}
derivative1 = error1 - prevError1;
error2 = RightMotors.position(degrees) - RightMotors.position(degrees);
integral2 += error2;
derivative2 = error2 - prevError2;
//core of the PID loop here, calculate the necessary motor power, combine both PID loops
motorPower = (kP1 * error1 + kI1 * integral1 + kD1 * derivative1);
///keep motor power variable in proper range, -1 to 1
if (motorPower > 1) motorPower = 1;
if (motorPower < -1) motorPower = -1;
//control the slew rate (dampen voltage differences), limits harsh acceleration
float slewRate = 0.08f;
if (motorPower > prevMotorPower + slewRate) {
motorPower = prevMotorPower + slewRate;
}
if (motorPower < prevMotorPower - slewRate) {
motorPower = prevMotorPower - slewRate;
}
//apply motor voltages
LeftMotors.spin(forward, 11 * motorPower * speedPID, volt);
RightMotors.spin(forward, 11 * motorPower * speedPID, volt);
//update final variables
prevMotorPower = motorPower;
prevError1 = error1;
prevError2 = error2;
//update histories
errorHistory.push_back(error1);
powerHistory.push_back(std::abs(motorPower));
time += 20;
//break out of the loop if we have reached the target or B is pressed
//we have reached the target if the error is less than 5 and the previous error is similar
if (Controller1.ButtonB.pressing() || ((std::abs(error1) < 5) && std::abs(error1 - prevError1) < 2)) {
break;
}
//don't hog CPU