   {
     if (variable_flag == false)
     {      
+      imu.begin();
+
       odom_pose[0] = 0.0;
       odom_pose[1] = 0.0;
       odom_pose[2] = 0.0;

    wheel_r = 0.0;

  delta_s     = WHEEL_RADIUS * (wheel_r + wheel_l) / 2.0;
  theta       = atan2f(imu.quat[1]*imu.quat[2] + imu.quat[0]*imu.quat[3],
                       0.5f - imu.quat[2]*imu.quat[2] - imu.quat[3]*imu.quat[3]);
  delta_theta = theta - last_theta;

  v = delta_s / step_time;

  odom_vel[1] = 0.0;
  odom_vel[2] = w;

  odom.header.frame_id = "odom";
  odom.child_frame_id  = "base_link";

  odom.pose.pose.position.x = odom_pose[0];
  odom.pose.pose.position.y = odom_pose[1];
  odom.pose.pose.position.z = 0;
