caster.urdf.xacro

caster.urdf.xacro

<?xml version="1.0"?>


<robot xmlns:xacro="http://ros.org/wiki/xacro" >


	<!-- Caster Dimensions -->
	<!-- These Dimensions are directly taken from the Solidworks model-->
    <xacro:property name="caster_wheel_length" value="0.02333" />
    <xacro:property name="caster_wheel_radius" value="0.024165" />
    <xacro:property name="caster_base_length" value="0.015" />
    <xacro:property name="caster_base_radius" value="0.015" />
    <xacro:property name="caster_base_joint_x" value="-0.02626" />
    <xacro:property name="caster_base_joint_z" value="-0.042385" />
    <xacro:property name="caster_base_link_z" value="-0.05615" />
    <xacro:property name="M_PI" value="3.14" />





	<xacro:property name="wheel_kp" value="600000" />
    <xacro:property name="wheel_kd" value="3" />
    <xacro:property name="wheel_mu1" value="10000000" />
    <xacro:property name="wheel_mu2" value="10000000" />

	<xacro:macro name="caster" params="caster_prefix parent_link *joint_pose">
		<!-- Caster Wheel Link -->
		<link name="${caster_prefix}_caster_link">
			<!--  These values are taken from the mass properties tool of Solidworks			 -->
			<inertial>
				<mass value="0.03837" />
				<origin xyz="0 0 0" />
				<inertia  ixx="0.000008221" ixy="0" ixz="0" iyy="0.000013003" iyz="0" izz="0.000008221" />
			</inertial>
			<!-- Here we included visual mesh generated from Blender as 
  				 the visual geometry of the caster wheel link-->
			<visual>
                <origin xyz="0 0 0" rpy="${M_PI/2} 0 0" />
				<geometry>
					<mesh filename="package://onebot_description/meshes/caswheel.dae" />
				</geometry>
			</visual>
			<!--  A simplified cylinder is used as the collision geometry -->
			<collision>
				<origin xyz="0 0 0" rpy="${M_PI/2} 0 0" />
				<geometry>
					<cylinder length="${caster_wheel_length/2}" radius="${caster_wheel_radius}" />
				</geometry>
			</collision>
		</link>

		<!-- Caster Base Link -->
        <link name="${caster_prefix}_caster_base">
			<inertial>
				<mass value="0.06597" />
				<origin xyz="-0.01204 0 -0.01454" />
				<inertia  ixx="0.000039912" ixy="0" ixz="0.000017794" iyy="0.000050728" iyz="0" izz="0.000035261" />
			</inertial>
			<visual>
				<!-- Here the xacro arguments have been used. If the argument is true the visual mesh is used as
	 				 the visual geometry otherwise a simple cylinder is used as the visual geometry-->
				<xacro:if value="$(arg mesh_enabled)">
					<origin xyz="0 0 0" rpy="0 0 0" />
					<geometry>
						<mesh filename="package://onebot_description/meshes/caster_base2.dae" />
					</geometry>
				</xacro:if>
				<xacro:unless value="$(arg mesh_enabled)">
					<origin xyz="0 0 ${-caster_base_length/2}" rpy="0 0 0" />
					<geometry>
						<cylinder length="${caster_base_length}" radius="${caster_base_radius}" />
					</geometry>
				</xacro:unless>
			</visual>
			<collision>
				<origin xyz="0 0 ${-caster_base_length/2}" rpy="0 0 0" />
				<geometry>
					<cylinder length="${caster_base_length}" radius="${caster_base_radius}" />
				</geometry>
			</collision>
		</link>

		<!-- Caster Base Link and Wheel Link Joint 
			 This joint is defined as a continuous type which enables the continuous movement in the joint. -->
        <joint name="${caster_prefix}_cwheel" type="continuous">
			<parent link="${caster_prefix}_caster_base"/>
			<child link="${caster_prefix}_caster_link"/>
			<origin xyz="${caster_base_joint_x} 0 ${caster_base_joint_z}" rpy="0 0 0" />
			<axis xyz="0 1 0" rpy="0 0 0" />				
		</joint>

		<!-- Caster base and parent joint 
			 This joint is also defined as continuous. A friction tag is added to model the friction 
			 in the actual casters. Change the values and find which suits the best-->
		<joint name="${caster_prefix}_caster" type="continuous">
			<parent link="${parent_link}"/>
			<child link="${caster_prefix}_caster_base"/>
			<xacro:insert_block name="joint_pose"/>
			<axis xyz="0 0 1" rpy="0 0 0" />       
			<dynamics friction="0.100" />
		</joint>
		
		<!-- The Gazebo physics engine ODE parameters are defined --> 
		<gazebo reference="${caster_prefix}_caster_link">
			<mu1 value="${wheel_mu1}"/>
			<mu2 value="${wheel_mu2}"/>
			<kp>${wheel_kp}</kp>
    		<kd>${wheel_kd}</kd>
			<dampingFactor>0.05</dampingFactor>
			<fdir1 value="1 0 0"/>
		</gazebo>
		
        <gazebo reference="${caster_prefix}_caster_base">
			<mu1 value="${wheel_mu1}"/>
			<mu2 value="${wheel_mu2}"/>
			<kp>${wheel_kp}</kp>
    		<kd>${wheel_kd}</kd>
			<fdir1 value="1 0 0"/>
		</gazebo>

		

		<!-- A transmission tag is added to visualize the motion of the caster in Rviz through
			 the joint state controller --> 
		<transmission name="${caster_prefix}_caster_trans" type="SimpleTransmission">
			<type>transmission_interface/SimpleTransmission</type>
			<actuator name="${caster_prefix}_caster_motor">
				<mechanicalReduction>1</mechanicalReduction>
			</actuator>
			<joint name="${caster_prefix}_caster">
				<hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
			</joint>
		</transmission>


		<transmission name="${caster_prefix}_casterbase_trans" type="SimpleTransmission">
			<type>transmission_interface/SimpleTransmission</type>
			<actuator name="${caster_prefix}_casterbase_motor">
				<mechanicalReduction>1</mechanicalReduction>
			</actuator>
			<joint name="${caster_prefix}_cwheel">
				<hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
			</joint>
		</transmission>

	</xacro:macro>

</robot>