Long lags / pauses / delays before and after 90-degree turns

Programming Support ROBOTC Tech Support
#1

New programmer here – using RobotC on a VEX IQ kit. We’re just trying to program the robot to complete a basic (what we thought would be easy) autonomous square. It runs OK, but we experience long pauses / lags before and after the turns. Can someone offer guidance on what we’re doing wrong? TIA

#pragma config(Motor, motor1, left, tmotorVexIQ, PIDControl, encoder)
#pragma config(Motor, motor2, right, tmotorVexIQ, PIDControl, reversed, encoder)
//!!Code automatically generated by ‘ROBOTC’ configuration wizard !!//

task main()
{

resetMotorEncoder(left);
resetMotorEncoder(right);

setMotorTarget(left, 1180, 50);
setMotorTarget(right, 1180, 50);

repeatUntil(getMotorEncoder(left) == getMotorTarget(left));
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));



setMotorTarget(left, -500, 50);
setMotorTarget(right, 500, 50);

repeatUntil(getMotorEncoder(left) == getMotorTarget(left));
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));



resetMotorEncoder(left);
resetMotorEncoder(right);

setMotorTarget(left, 1180, 50);
setMotorTarget(right, 1180, 50);

repeatUntil(getMotorEncoder(left) == getMotorTarget(left));
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));


resetMotorEncoder(motor2);

setMotorTarget(motor2, 550, 50);

repeatUntil(getMotorEncoder(motor2) == getMotorTarget(motor2));



resetMotorEncoder(left);
resetMotorEncoder(right);

setMotorTarget(left, 1180, 50);
setMotorTarget(right, 1180, 50);

repeatUntil(getMotorEncoder(left) == getMotorTarget(left));
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));


resetMotorEncoder(motor2);

setMotorTarget(motor2, 500, 50);

repeatUntil(getMotorEncoder(motor2) == getMotorTarget(motor2));



resetMotorEncoder(left);
resetMotorEncoder(right);

setMotorTarget(left, 1180, 50);
setMotorTarget(right, 1180, 50);

repeatUntil(getMotorEncoder(left) == getMotorTarget(left));
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));
#2

Possibly because it is waiting for the error to be exactly 0 for both motors, and that takes a lot of time. Sometimes you need to put a threshold to make it exit faster. Consider making a function to simplify the process.

void waitForSettle() {
  int leftError = 0;
  int rightError = 0;
  int threshold = 2; //tolerance
  bool completed = false; //the loop will exit once this is true
  //this is a do-while loop, it will run at least once to do calculations before exiting
  do { 
    leftError = getMotorEncoder(left) - getMotorTarget(left); //if they are equal, error will be 0
    rightError = getMotorEncoder(right) - getMotorTarget(right);
    //completed will be true if both motors are threshold away from target, regardless of direction
    completed = abs(leftError) < threshold && abs(rightError) < threshold; 
  } while(!completed); //loop while not completed
}
1 Like
#3

Couple things. Good start…
Lotsa ways to do most things, but have to pick one or the other.

1st, no reset before the 1st turn, maybe cut/paste error when posting?
2nd, later turns only use one motor.
3rd, testing for == is too narrow, try >= and <=. This causes the lag…

The post above Is a perfect solution for controllable accuracy.

4th (minor) helpful to name consistently (right vs motor2) - and to use comments.
Finally, how could you use this?:

repeat(numberOfTimes)
{
  body
}

Rewrote your version for clarity, below.

task main()
{
// 1st straight
resetMotorEncoder(left);
resetMotorEncoder(right);
setMotorTarget(left, 1180, 50);
setMotorTarget(right, 1180, 50);
repeatUntil(getMotorEncoder(left) == getMotorTarget(left));
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));

// turn left
setMotorTarget(left, -500, 50);
setMotorTarget(right, 500, 50);
repeatUntil(getMotorEncoder(left) == getMotorTarget(left));
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));

// 2nd straight
resetMotorEncoder(left);
resetMotorEncoder(right);
setMotorTarget(left, 1180, 50);
setMotorTarget(right, 1180, 50);
repeatUntil(getMotorEncoder(left) == getMotorTarget(left));
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));

// 2nd turn left
resetMotorEncoder(right);
setMotorTarget(right, 550, 50);
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));

// 3rd straight
resetMotorEncoder(left);
resetMotorEncoder(right);
setMotorTarget(left, 1180, 50);
setMotorTarget(right, 1180, 50);
repeatUntil(getMotorEncoder(left) == getMotorTarget(left));
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));

// 3rd turn left
resetMotorEncoder(right);
setMotorTarget(motor1, 500, 50);
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));

// 4th straight
resetMotorEncoder(left);
resetMotorEncoder(right);
setMotorTarget(left, 1180, 50);
setMotorTarget(right, 1180, 50);
repeatUntil(getMotorEncoder(left) == getMotorTarget(left));
repeatUntil(getMotorEncoder(right) == getMotorTarget(right));
}

What’s your bot look like (width, wheelbase)? 500 turn not near 90 degrees on my standardbot.
Let us know how it goes.

1 Like
#4

Thank you to both of you for your quick responses to our inquiry. We were able to incorporate code from the second suggestion and it is greatly improved. Thank you – what a supportive community!

1 Like
#5

All good, thanks for feedback. Go for loops and functions, too.

Curious, what +/- motor degrees worked to get you 90 degree bot turn?

#6