Turning the Drivetrain Using RUN_TO_POSITION

Often times, like in the program created during Part 2: Robot Control, we use setPower(); to set the drivetrain motors to a set power or power based on a joystick's inputs. The combined power going to both motors help to determine the direction the robot moves or turns.

However, in RUN_TO_POSITION mode the encoder counts are used instead to dictate directionality of the motor.

• If a target position value is greater than the current position of the encoder, the motor moves forward.

• If the target position value is less than the current position of the encoder, the motor moves backwards.

Since speed an directionality impacts how a robot turns, target position and velocity need to be edited to get the robot to turn. Consider the following code:

int leftTarget = (int)(610 * COUNTS_PER_MM);
int rightTarget = (int)(-610 * COUNTS_PER_MM);
double TPS = (100/ 60) * COUNTS_PER_WHEEL_REV;
       
        
waitForStart();
        
        
leftmotor.setTargetPosition(leftTarget);
rightmotor.setTargetPosition(rightTarget);
        
leftmotor.setMode(DcMotor.RunMode.RUN_TO_POSITION);
rightmotor.setMode(DcMotor.RunMode.RUN_TO_POSITION);
        
leftmotor.setVelocity(TPS);
rightmotor.setVelocity(TPS);

The rightTarget has been changed to be a negative target position. Assuming that the encoder starts at zero due to STOP_AND_RESET_ENCODER this causes the robot to turn to the right.

Notice the velocity is the same for both motors. If you try running this code, you can see that the robot pivots along its center of rotation.

To get a wider turn, try changing the velocity so that the right motor is running at a lower velocity than the left motor. Adjust the velocity and target position as needed to get the turn you need.