MPU-6050 Gyro cross coupling problem

[ihart]

I am using the MPU-6050 for a Segway clone using an Arduino Uno.  The MPU-6050 is laid flat on the top of the segway platform with the Y axis used to measure front/back tilt.   Left/right rotation would be on the Z axis.

 

The front and back tilt seems to be working but when I turn left or right, the ZGyro seems to be coupling into the YGyro which is used for front/back tilting.  This causes the segway to dip when I turn left and raise up when I turn right.

 

When I look at the Arduino serial monitor with no motors enabled, I can see this behavior showing in my scrolling gyros printout.  In fact, the front back Y Axis motion seems to couple in to the Z axis Gyro as well.

 

Has anyone seen this before?  Any idea what might be causing this?

 

 

Some relevant code snips:

 

#include <Wire.h>
#include "I2Cdev.h"
#include "MPU6050_6Axis_MotionApps20.h"
 

 

  // supply your own gyro offsets here, scaled for min sensitivity
  mpu.setXGyroOffset(10);
  mpu.setYGyroOffset(7);
  mpu.setZGyroOffset(14);
  mpu.setZAccelOffset(900); // 1688 factory default for  test chip
 

 

   //Get sensor data
    mpu.dmpGetQuaternion(&q, fifoBuffer);
    mpu.dmpGetGyro(gyro, fifoBuffer);
    mpu.dmpGetGravity(&gravity, &q);
    mpu.dmpGetYawPitchRoll(ypr, &q, &gravity);