[FTC]: One Encoder Works; The Other Ones Does Not

[F Elliott]

I've done some more online research... This is exactly our problem and first surfaced about a year ago:
http://www.robotc.net/forums/viewtop...=2774&start=15

It was supposedly fixed in ROBOTC 3.54. We are running ROBOTC 3.62

Also, the order of powering up the motor controller and the NXT seems to be important. We are using this order:
1. Power up 12v to motor controller
2. Power up NXT
3. Download and run program

[FTC4211]

Hello,

Here is the code that we use for moving motors to a position. We have had problems non-stop with the built in RobotC nMotorEncoderTarget function so we wrote our own.

Here it is written to do what your code was supposed to do:

#pragma config(Hubs,  S1, HTMotor,  none,     none,     none)
#pragma config(Sensor, S1,     ,               sensorI2CMuxController)
#pragma config(Motor,  mtr_S1_C1_1,     motorD,        tmotorTetrix, PIDControl, encoder)
#pragma config(Motor,  mtr_S1_C1_2,     motorE,        tmotorTetrix, PIDControl, reversed, encoder)
//*!!Code automatically generated by 'ROBOTC' configuration wizard  

typedef enum
{
Quintic = 5, // good for very light loads with no backlash/gears: very fast

Cubic = 3, // good for light loads with minimal backlash in the gears: faster near its target but can overshoot the target

Linear = 1, // good for most loads on motors: good average, try starting with this one

CubeRoot = (1/3), // good for heavy loads with backlash in the gears: slow near its target

QuinticRoot = (1/5) // good for very heavy loads with lots of backlash in the gears: slow near its target
}tMotorPowerCurve;  // motor power curve applications: test to find the best for your application

int trim(int num, int min, int max) // clips @param 'num' to be within within min/max values
{
return (num>max) ? max : (num<min) ? min : num;
}

int targetLocationToMotorPower(tMotor nMotor, int targetPos, short deadband, float speedMultiplier, short minPower, short maxPower, tMotorPowerCurve powerCurve=Linear)
{
int iPower;
if (abs(nMotorEncoder[nMotor]-targetPos)<deadband)
{
iPower=0;
}
else
{
iPower = pow((-(nMotorEncoder[nMotor]-targetPos)),(float)powerCurve)*(float)speedMultiplier;
}
return trim(iPower, minPower, maxPower);
}

bool moveMotorToPosition(tMotor nMotor, int targetPos, short deadband=20, float speedMultiplier=1.0, short minPower=-50, short maxPower=50, tMotorPowerCurve powerCurve=Linear) // return true if at target
{
int power = targetLocationToMotorPower(targetPos, nMotor, deadband, speedMultiplier,minPower,maxPower,powerCurve);
motor[nMotor]= power;
return power == 0; // if power = 0 then at target
}

task main()
{

nMotorEncoder[motorD]=0;
nMotorEncoder[motorE]=0;
while (!moveMotorToPosition(motorD, 720)||!moveMotorToPosition(motorE, 720))
{
}
wait1Msec(3000);
}

We have different power curves for the target to motor power function because we found that depending on load and backlash in certain applications a single power curve could cause oscillations. We have used this method for controlling everything from arms to our drive base with great success.

Play around with this code and see what settings work the best.

Best of luck,
Team 4211

[F Elliott]

Wow. Terrific! Many thanks!