IMU plugin erratic acceleration measurements

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Hi,

I am trying to use the IMU plugin in Gazebo (v2.2.5) but am seeing weird behavior. I am running the IMU without biases or noise, and the acceleration/rate outputs integrate to trajectories I expect, but the measurements are nevertheless erratic: they are constantly switching sign. I publish sinusoidal velocities in gazebo so I know what to expect from the acceleration measurements, but they look like this:

Whole dataset (a_x, a_y, w)

Zoomed in

I don't expect perfectly smooth trajectories but 50m/s^2 accels at times seems too unstable, something must be wrong. If I just look at the gravity vector in rviz it jumps all over the place. I tried to set everything to zero...

<!-- Chassis -->
    <link name="base_link">
        <inertial>
            <mass value="10.0"/>
            <origin xyz="0 0 0.177"/>
            <inertia 
                 ixx="0.3338" ixy="0.0" ixz="0.0"
                 iyy="0.4783" iyz="0.0"
                 izz="0.3338"/>
        </inertial>
        <visual name="base_visual">
            <origin xyz="0 0 0.177" rpy="0 0 0"/>
            <geometry name="pioneer_geom">
                <mesh filename="package://dopebot_description/meshes/chassis.stl"/>
            </geometry>
            <material name="ChassisRed">
                <color rgba="0.851 0.0 0.0 1.0"/>
            </material>
        </visual>
        <collision>
            <origin xyz="0 0 0.177" rpy="0 0 0"/>
                <geometry>
                    <mesh filename="package://dopebot_description/meshes/chassis.stl"/>
                </geometry>
        </collision>
    </link> 

<!-- IMU -->
<link name="imu_link">
  <inertial>
    <mass value="0.001"/>
    <origin rpy="0 0 0" xyz="0 0 0"/>
    <inertia ixx="0.0001" ixy="0" ixz="0" iyy="0.0001" iyz="0" izz="0.0001"/>
  </inertial>

  <visual>
    <origin rpy="0 0 0" xyz="0 0 0"/>
    <geometry>
      <box size="0.1 0.1 0.1"/>
    </geometry>
  </visual>

  <collision>
    <origin rpy="0 0 0" xyz="0 0 0"/>
    <geometry>
      <box size="0.1 0.1 0.1"/>
    </geometry>
  </collision>
</link>

<!-- IMU Joint -->
  <joint name="imu_joint" type="fixed">
    <axis xyz="1 0 0"/> <!-- 0 1 0 -->
    <origin xyz="0 0 0.28"/>
    <parent link="base_link"/>
    <child link="imu_link"/>
  </joint>

      <plugin name="imu_plugin" filename="libhector_gazebo_ros_imu.so">
            <updateRate>1000</updateRate>
            <bodyName>base_link</bodyName>
            <topicName>/imu</topicName>
            <serviceName>/imu/calibrate</serviceName>
            <accelOffset>0.0 0.0 0.0</accelOffset>
            <accelDrift>0.0 0.0 0.0</accelDrift>
            <accelDriftFrequency>0.0 0.0 0.0</accelDriftFrequency>
            <accelGaussianNoise>0.0 0.0 0.0</accelGaussianNoise>
            <rateOffset>0.0 0.0 0.0</rateOffset>
            <rateDrift>0.0 0.0 0.0</rateDrift>
            <rateDriftFrequency>0.0 0.0 0.0</rateDriftFrequency>
            <rateGaussianNoise>0.0 0.0 0.0</rateGaussianNoise>
            <headingOffset>0.0</headingOffset>
            <headingDrift>0.0</headingDrift>
            <headingDriftFrequency>0.0</headingDriftFrequency>
            <headingGaussianNoise>0.0</headingGaussianNoise>
            <rpyOffset>0.0 0.0 0.0</rpyOffset>
            <xyzOffset>0.0 0.0 0.0</xyzOffset>
            <gaussianNoise>0.0</gaussianNoise>
        </plugin>

but the problem remains. Any ideas?

Thank you,

Jacob