Urdf Parsing

Parsing URDF files to get rigid body tree object. More...

Classes
class	fsb::urdf::UrdfError
	Urdf parsing error. More...
class	fsb::urdf::NameMap
	Name map relating names to object indices. More...
class	fsb::urdf::UrdfNameMap
	Name-index map of joints and bodies in rigid body tree. More...
struct	fsb::urdf::UrdfJoint
	Structure representing a URDF joint. More...

Enumerations
enum class	fsb::urdf::UrdfErrorType {   UrdfErrorType::SUCCESS , UrdfErrorType::VALUE_CONVERSION_FAILED , UrdfErrorType::RANGE_ERROR , UrdfErrorType::LOAD_FILE_ERROR ,   UrdfErrorType::PARSE_ERROR , UrdfErrorType::MISSING_ROBOT , UrdfErrorType::MISSING_NAME , UrdfErrorType::REPEATED_NAME ,   UrdfErrorType::MISSING_JOINT_TYPE , UrdfErrorType::INVALID_JOINT_TYPE , UrdfErrorType::JOINT_INVALID_AXIS , UrdfErrorType::MISSING_JOINT_PARENT ,   UrdfErrorType::MISSING_PARENT_LINK_ATTRIBUTE , UrdfErrorType::MISSING_JOINT_CHILD , UrdfErrorType::MISSING_CHILD_LINK_ATTRIBUTE , UrdfErrorType::MISSING_BODY_INERTIAL ,   UrdfErrorType::MISSING_BODY_MASS , UrdfErrorType::MISSING_BODY_INERTIA , UrdfErrorType::MISSING_INERTIA_ATTRIBUTE , UrdfErrorType::MISSING_MASS_VALUE_ATTRIBUTE ,   UrdfErrorType::BODY_PRINCIPAL_INERTIA , UrdfErrorType::BODY_INERTIA_NOT_POSITIVE_DEFINITE , UrdfErrorType::MAX_JOINTS_EXCEEDED , UrdfErrorType::MAX_BODIES_EXCEEDED ,   UrdfErrorType::MAX_COORDINATES_EXCEEDED , UrdfErrorType::MAX_DOFS_EXCEEDED , UrdfErrorType::BODY_TREE_ERROR , UrdfErrorType::JOINT_PARENT_BODY_NOT_FOUND ,   UrdfErrorType::JOINT_CHILD_BODY_NOT_FOUND }
	Errors from parsing URDF. More...
enum class	fsb::urdf::NameMapError { NameMapError::SUCCESS , NameMapError::NOT_FOUND , NameMapError::EXISTS }
	Name map errors. More...

Functions
size_t	fsb::urdf::string_to_index (const std::string &str, UrdfError &err)
	Parse a string to extract an unsigned integer as index value.
real_t	fsb::urdf::string_to_real (const std::string &str, UrdfError &err)
	Parse a string to extract a real value.
std::vector< std::string >	fsb::urdf::split_string_spaces (const std::string &str)
	Split a string with space character as delimiter.
Vec3	fsb::urdf::string_to_vector (const std::string &str, UrdfError &err)
	Converts a string to a vector with 3 elements separated by the space character.
Quaternion	fsb::urdf::string_to_quaternion (const std::string &str, UrdfError &err)
	Converts a string to a quaternion.
UrdfJoint	fsb::urdf::urdf_parse_joint (const std::string &fname, const tinyxml2::XMLElement *joint_xml, UrdfError &err)
	Parse a URDF joint element.
Transform	fsb::urdf::urdf_parse_origin (const std::string &fname, const std::string &el_name, const tinyxml2::XMLElement *el_xml, UrdfError &err)
	Parse first child origin element to get coordinate transform.
MotionVector	fsb::urdf::urdf_parse_origin_offset (const std::string &fname, const std::string &body_name, const tinyxml2::XMLElement *body_xml, UrdfError &err)
	Parse first child origin offset element.
Inertia	fsb::urdf::urdf_parse_inertia_mass (const std::string &fname, const std::string &body_name, const tinyxml2::XMLElement *inertial_xml, real_t &body_mass, UrdfError &err)
	Parse inertial element from URDF file.
BodyTree	fsb::urdf::parse_urdf_string (const std::string &urdf_string, UrdfNameMap &name_map, UrdfError &err)
	Parse URDF file string to get body tree object.
BodyTree	fsb::urdf::parse_urdf_file (const std::string &urdf_filename, UrdfNameMap &name_map, UrdfError &err)
	Parse URDF file to get body tree object.

Detailed Description

Parsing URDF files to get rigid body tree object.

Enumeration Type Documentation

NameMapError

enum class fsb::urdf::NameMapError

strong

Name map errors.

Enumerator
SUCCESS	No error.
NOT_FOUND	Joint or body name not found.
EXISTS	Joint or body already exists.

UrdfErrorType

enum class fsb::urdf::UrdfErrorType

strong

Errors from parsing URDF.

Enumerator
SUCCESS	No error.
VALUE_CONVERSION_FAILED	Failed to convert to numerical value.
RANGE_ERROR	Value out of range.
LOAD_FILE_ERROR	File failed to load.
PARSE_ERROR	Failed to parse URDF XML.
MISSING_ROBOT	Missing robot element.
MISSING_NAME	Missing name attribute.
REPEATED_NAME	Repeated element name.
MISSING_JOINT_TYPE	Missing joint type attribute.
INVALID_JOINT_TYPE	Invalid joint type attribute.
JOINT_INVALID_AXIS	Invalid joint axis.
MISSING_JOINT_PARENT	Joint parent not found.
MISSING_PARENT_LINK_ATTRIBUTE	Missing parent attribute on joint element.
MISSING_JOINT_CHILD	Missing child attribute on joint element.
MISSING_CHILD_LINK_ATTRIBUTE	Missing child attribute on joint element.
MISSING_BODY_INERTIAL	Missing inertial element for body.
MISSING_BODY_MASS	Missing mass element.
MISSING_BODY_INERTIA	Missing inertia element.
MISSING_INERTIA_ATTRIBUTE	Missing inertia attribute ixx, iyy, or izz.
MISSING_MASS_VALUE_ATTRIBUTE	Missing mass value attribute.
BODY_PRINCIPAL_INERTIA	Failed to determine inertia principal axis.
BODY_INERTIA_NOT_POSITIVE_DEFINITE	Inertia is not positive definite.
MAX_JOINTS_EXCEEDED	Maximum number of joints exceeded.
MAX_BODIES_EXCEEDED	Maximum number of bodies exceeded.
MAX_COORDINATES_EXCEEDED	Maximum number of position coordinates exceeded.
MAX_DOFS_EXCEEDED	Maximum number of degrees of freedom exceeded.
BODY_TREE_ERROR	Failed to add body to tree.
JOINT_PARENT_BODY_NOT_FOUND	Joint parent body not found.
JOINT_CHILD_BODY_NOT_FOUND	Joint child body not found.

Function Documentation

parse_urdf_file()

BodyTree fsb::urdf::parse_urdf_file	(	const std::string &	urdf_filename,
		UrdfNameMap &	name_map,
		UrdfError &	err
	)

Parse URDF file to get body tree object.

Parameters

urdf_filename	Input URDF filename
name_map	Output name map for rigid body tree
err	Error object

Returns

Body tree parsed from URDF

parse_urdf_string()

BodyTree fsb::urdf::parse_urdf_string	(	const std::string &	urdf_string,
		UrdfNameMap &	name_map,
		UrdfError &	err
	)

Parse URDF file string to get body tree object.

Parameters

urdf_string	String of URDF contents
name_map	Output name map for rigid body tree
err	Error object

Returns

Body tree parsed from URDF

split_string_spaces()

std::vector< std::string > fsb::urdf::split_string_spaces

(

const std::string &

str

)

Split a string with space character as delimiter.

Parameters

str	String to split

Returns

Array of strings between space characters.

string_to_index()

size_t fsb::urdf::string_to_index	(	const std::string &	str,
		UrdfError &	err
	)

Parse a string to extract an unsigned integer as index value.

The standard function std::strtol is used to parse the string and ignores trailing string characters after parsing the value.

Parameters

str	String to convert to an index value (unsigned integer)
err	Error from parsing

Returns

Index value

string_to_quaternion()

Quaternion fsb::urdf::string_to_quaternion	(	const std::string &	str,
		UrdfError &	err
	)

Converts a string to a quaternion.

Parameters

str	String to convert to a quaternion
err	Error from parsing string.

Returns

Quaternion from string

string_to_real()

real_t fsb::urdf::string_to_real	(	const std::string &	str,
		UrdfError &	err
	)

Parse a string to extract a real value.

The standard function std::strtod is used to parse the string and ignores trailing string characters after parsing the value.

Parameters

str	String to convert to a real value
err	Error from parsing

Returns

Real value

string_to_vector()

Vec3 fsb::urdf::string_to_vector	(	const std::string &	str,
		UrdfError &	err
	)

Converts a string to a vector with 3 elements separated by the space character.

Parameters

str	Convert string to 3-element vector
err	Error from parsing string.

Returns

Vector from string

urdf_parse_inertia_mass()

Inertia fsb::urdf::urdf_parse_inertia_mass	(	const std::string &	fname,
		const std::string &	body_name,
		const tinyxml2::XMLElement *	inertial_xml,
		real_t &	body_mass,
		UrdfError &	err
	)

Parse inertial element from URDF file.

This function parses the inertial element of a body in a URDF file. An example xml element is:

<inertial>
  <mass value="1.0"/>
  <inertia ixx="0.1" ixy="0.0" ixz="0.0" iyy="0.1" iyz="0.0" izz="0.1"/>
</inertial>

Parameters

[in]	fname	File name of the URDF file
[in]	body_name	Body name to which the inertial element belongs
[in]	inertial_xml	Pointer to the inertial XML element
[out]	body_mass	Mass of the body
[out]	err	Error object to store any parsing errors

Returns

Inertia tensor

urdf_parse_joint()

UrdfJoint fsb::urdf::urdf_parse_joint	(	const std::string &	fname,
		const tinyxml2::XMLElement *	joint_xml,
		UrdfError &	err
	)

Parse a URDF joint element.

An example xml snippet with a joint element is shown below.

<joint name="jointname" type="revolute">
  <parent link="parent_linkname"/>
  <child link="child_linkname"/>
  <origin xyz="0 0 0" rpy="0 0 0"/>
  <axis xyz="0 0 1"/>
</joint>

Parameters

[in]	fname	Name of the file being parsed
[in]	joint_xml	XML element representing the joint
[out]	err	Error status returned after parsing

Returns

Parsed URDF joint

urdf_parse_origin()

Transform fsb::urdf::urdf_parse_origin	(	const std::string &	fname,
		const std::string &	el_name,
		const tinyxml2::XMLElement *	el_xml,
		UrdfError &	err
	)

Parse first child origin element to get coordinate transform.

Here is an example xml snippet with the child origin of an element

<element name="elname">
  <origin xyz="0 0 0" rpy="0 0 0" />
</element>

Parameters

fname	Name of file being parsed
el_name	Parent element name containing origin
el_xml	Parent element containing origin
err	Error status returned after parsing

Returns

Coordinate transform of origin

urdf_parse_origin_offset()

MotionVector fsb::urdf::urdf_parse_origin_offset	(	const std::string &	fname,
		const std::string &	body_name,
		const tinyxml2::XMLElement *	body_xml,
		UrdfError &	err
	)

Parse first child origin offset element.

The origin offset is a custom element for the Fancy Safe Bot library and is prefixed fsb:. An XML snippet shows an example offset below. The angular offset is an axis-angle representation of a rotation in radians.

<element name="elname">
  <fsb:origin_offset xyz="0 0 0" rotvec="0 0 0" />
</element>

Parameters

fname	Name of file being parsed
body_name	Parent body element name containing origin offset
body_xml	Parent element containing origin offset
err	Error status returned after parsing

Returns

Linear and angular coordinate transform offset