Tank drive motor issues

VEX V5 General Discussion Technical Discussion
1

Hi,

We’re currently facing issues with our 4 motor tank drive. Whenever we push a little into a cube or cluster of stars, our drive bugs out. I think that this is different from a drive burning out for two reasons - The motors don’t run hot, and there is jittering which incapacitates every motor on the robot, i.e, we can’t use our lift at all.

We removed chains to reduce friction and our robot is not that heavy. Here’s another detail: We have an IEM on either side of our drive for autonomous. In auton, the IEM’s work for two commands, i.e, checking and resetting the sensor values, and then they mysteriously switch off. Not sure if it is related, but it is another issue.

My guess is that it is programmatic or that the motors are crappy, but I don’t see why either would incapacitate the entire robot when the motors ‘burn out’.

I don’t have pics, but will clarify whatever I can. Your help is much appreciated!

2

Please post the code so we can rule out programming errors.

3 

#pragma config(I2C_Usage, I2C1, i2cSensors)
#pragma config(Sensor, in1,    gyro,           sensorGyro)
#pragma config(Sensor, dgtl3,  LimitSwitch,    sensorTouch)
#pragma config(Sensor, I2C_1,  leftDriveCount, sensorQuadEncoderOnI2CPort,    , AutoAssign )
#pragma config(Sensor, I2C_2,  rightDriveCount, sensorQuadEncoderOnI2CPort,    , AutoAssign )
#pragma config(Motor,  port2,           rightDrive,    tmotorVex393HighSpeed_MC29, openLoop, reversed, driveRight, encoderPort, I2C_2)
#pragma config(Motor,  port3,           leftDrive,     tmotorVex393HighSpeed_MC29, openLoop, reversed, driveLeft, encoderPort, I2C_1)
#pragma config(Motor,  port4,           rightTopLauncher, tmotorVex393_MC29, openLoop)
#pragma config(Motor,  port5,           rightMiddleLauncher, tmotorVex393_MC29, openLoop)
#pragma config(Motor,  port6,           bottomLauncher, tmotorVex393_MC29, openLoop)
#pragma config(Motor,  port7,           leftMiddleLauncher, tmotorVex393_MC29, openLoop, reversed)
#pragma config(Motor,  port8,           leftTopLauncher, tmotorVex393_MC29, openLoop, reversed)
int cubicMap(int x){
	return x / 127 * x / 127 * x;
}

task usercontrol()
{

	while(true){ // arcade drive user control
	// left joystick Ch3 fw-bk
	// right joystick Ch1 lt-rt
		int forward = 0; int backward = 0;
		if(vexRT[Ch3] > 0){
			int value = cubicMap(vexRT[Ch3] + abs(vexRT[Ch4]));
			if(value > 80){
				int currentSpeed = 80;
				while(currentSpeed < value){
					forward = currentSpeed;
					motor[leftDrive] = (forward + leftRight) / 2;
					currentSpeed += (value - currentSpeed) / 4;
					wait1Msec(150);
				}
			} else{
	  		forward = cubicMap(vexRT[Ch3] + abs(vexRT[Ch4]));
	  	}
		} else{
			int value = cubicMap(vexRT[Ch3] - abs(vexRT[Ch4]));
			if(value > 80){
				int currentSpeed = 80;
				while(currentSpeed < value){
					backward = currentSpeed;
					motor[leftDrive] = (backward + leftRight) / 2;
					currentSpeed += (value - currentSpeed) / 4;
					wait1Msec(150);
				}
			} else{
	  		backward = cubicMap(vexRT[Ch3] - abs(vexRT[Ch4]));
	  	}
		}
		int leftRight = 0;
		if(vexRT[Ch1] > 0){
	  	leftRight = cubicMap(vexRT[Ch1] + abs(vexRT[Ch2]));
		} else{
			leftRight = cubicMap(vexRT[Ch1] - abs(vexRT[Ch2]));
		}

		motor[leftDrive] = (forward + backward + leftRight) / 2;
		motor[rightDrive] = (forward + backward - leftRight) / 2;

		if(vexRT[Btn6U] == 1){ // raise arm
			motor[rightTopLauncher] = motor[rightMiddleLauncher] = motor[bottomLauncher] = motor[leftMiddleLauncher] = motor[leftTopLauncher] = 127;
		} else if(vexRT[Btn6D] == 1){ // pull down arm
			motor[rightTopLauncher] = motor[rightMiddleLauncher] = motor[bottomLauncher] = motor[leftMiddleLauncher] = motor[leftTopLauncher] = -127;
		} else if(SensorValue[LimitSwitch] == 1 && vexRT[Btn6U] == 0) { // hold down arm
			motor[rightTopLauncher] = motor[rightMiddleLauncher] = motor[bottomLauncher] = motor[leftMiddleLauncher] = motor[leftTopLauncher] = -10;
		}	else{ // stop moving arm
			motor[rightTopLauncher] = motor[rightMiddleLauncher] = motor[bottomLauncher] = motor[leftMiddleLauncher] = motor[leftTopLauncher] = 0;
		}
	}
}

Thanks!

4