differential drive robot not going in a straight line.

I have a differential drive robot using the differential drive controller plugin in gazebo This is the .gazebo file. falsetrue100left_wheel_hingeright_wheel_hinge20cmd_velmb1/odomodombase_linkGazebo/OrangeGazebo/Green0 0 0 0 0 0true407201-1.5707961.5707960.1030.00.01gaussian0.00.01/scanhokuyotruetrue100true__default_topic__mb1/imuimu_link10.00.00 0 00 0 0imu_link0 0 0 0 0 0 and this is the .xacro file 0 0 0.1 0 0 0001.01.0 The problem is that when i command it to go in a straight line(only linear velocity) it deviates right (-Y direction) after moving straight for a few meters. Is there any fix to this problem.