gazebo urdf loading errors

gistfile1.txt

Warning [parser.cc:377] SDF has no <sdf> element in file[data-string]
Dbg extension [<joint:hinge name="ackermann_left_bar_joint"><body1>ackermann_bar_link</body1><body2>front_left_bar_link</body2><anchor>ackermann_bar_link</anchor><axis>0 0 1</axis><anchorOffset>0 0.45 0</anchorOffset></joint:hinge>] not converted.
Dbg extension [<joint:hinge name="ackermann_right_bar_joint"><body1>ackermann_bar_link</body1><body2>front_right_bar_link</body2><anchor>ackermann_bar_link</anchor><axis>0 0 1</axis><anchorOffset>0 -0.45 0</anchorOffset></joint:hinge>] not converted.
Dbg extension [<controller:ackermann_plugin name="ackermann_controller" plugin="libackermann_plugin.so"><alwaysOn>true</alwaysOn><update>100</update><updateRate>100.0</updateRate><leftJoint>back_left_wheel_joint</leftJoint><rightJoint>back_right_wheel_joint</rightJoint><steerJoint>steer_joint</steerJoint><wheelSeparationWidth>1.1</wheelSeparationWidth><wheelSeparationLength>1.6</wheelSeparationLength><wheelDiameter>0.4</wheelDiameter><driveTorque>5</driveTorque><steerTorque>5</steerTorque><interface:position name="position_iface_0" /><robotNamespace>/</robotNamespace><topicName>cmd_vel</topicName></controller:ackermann_plugin>] not converted.
Dbg [base_link] has no parent joint
Error [parser.cc:712] XML Element[joint:hinge], child of element[model] not defined in SDF. Ignoring.[model]
Error [parser.cc:703] Error reading element <model>
Error [parser.cc:369] Unable to read element <sdf>
Error [parser.cc:319] parse as old urdf model file failed.