robot_calibration::ChainModel Class Reference

Model of a kinematic chain. This is the basic instance where we transform the world observations into the proper root frame. More...

#include <chain.h>

Inheritance diagram for robot_calibration::ChainModel:

Public Member Functions
	ChainModel (const std::string &name, KDL::Tree model, std::string root, std::string tip)
	Create a new chain model. More...
KDL::Frame	getChainFK (const CalibrationOffsetParser &offsets, const sensor_msgs::JointState &state)
	Compute the forward kinematics of the chain, based on the offsets and the joint positions of the state message. More...
std::string	name () const
virtual std::vector< geometry_msgs::PointStamped >	project (const robot_calibration_msgs::CalibrationData &data, const CalibrationOffsetParser &offsets)
	Compute the position of the estimated points. More...
virtual	~ChainModel ()

Protected Attributes
std::string	name_
std::string	root_
std::string	tip_

Private Attributes
KDL::Chain	chain_

Detailed Description

Model of a kinematic chain. This is the basic instance where we transform the world observations into the proper root frame.

Each world observation is an estimated point in some frame. In the case of the four led gripper, each led has an absolutely known location in the gripper_led_frame. The ordering of the points is:

       _                   _
      | |                 | |
      | |                 | |
      | |                 | |
      | |                 | |
      | |                 | |
      | |     gripper     | |
      |---------------------|
      |                     |
      |    0           3    |
      |                     |
      |          X <------------ gripper_led_frame
      |                     |
      |    2           1    |
      |                     |
       /

When using a checkerboard, each interesection on the checkerboard is an observation point. Even though checkerboard should be flat, the code assumes that each checkerboard intersection has 3 degrees of translational freedom. The gripper_led_frame to checkerboard_frame transformation becomes a set of free parameters in the calibration.

Based on the 6x5 checkboard, the ordering of the oberservation points produced by the OpenCV chessboard finder is always the same:

   ____________________________
  |                            |
  |  ###   ###   ###   ###     |
  |  ###   ###   ###   ###     |
  |  ###   ###   ###  LL##     |    11  First Observation Point
  |     ###   ###   ##LL  ###  |    11
  |     ###   ###   ###   ###  |
  |     ###   ###   ###   ###  |    22  Second Observation Point
  |  ###   ###   ###   ###     |    22
  |  ###   ###   ###   ###     |
  |  ##22  ###   ###   ###     |    LL  Last (20th) Obervation Point
  |    22##   ###   ###   ###  |    LL
  |     ###   ###   ###   ###  |
  |    11##   ###   ###   ###  |
  |  ##11  ###   ###   ###     |
  |  ###   ###   ###   ###     |   gripper_link
  |  ###   ###   ###   ###     |      X-axis (increasing row)
  |                            |     ^
  |           _____            |     |     gripper_link
  |          |     |           |     |  ----> Z-axis (increasing col)
  |          |     |
  |          |  0<----- gripper_link frame origin
  |__________|     |___________
             |     |
          ___|_____|___
         |             |
         |   Gripper   |
         |             |

For the ideal checkboard:

• All the checkerboard points should fall on or near Y=0 plane.
• The intersection points are spread appart by 25mm
• The X-offset from the gripper frame to the first observation point is 100mm
• The Z-offset from the gripper frame to the first observation point is -50mm The checkboard points are numberered so that the lowest Z value are the first points

Definition at line 107 of file chain.h.

Constructor & Destructor Documentation

robot_calibration::ChainModel::ChainModel	(	const std::string &	name,
		KDL::Tree	model,
		std::string	root,
		std::string	tip
	)

Create a new chain model.

Parameters

model	The KDL model of the robot's kinematics.
root	The name of the root link, must be consistent across all models used for error modeling. Usually 'base_link'.
tip	The tip of the chain.

Definition at line 40 of file models.cpp.

virtual robot_calibration::ChainModel::~ChainModel ( )

inlinevirtual

Definition at line 118 of file chain.h.

Member Function Documentation

KDL::Frame robot_calibration::ChainModel::getChainFK	(	const CalibrationOffsetParser &	offsets,
		const sensor_msgs::JointState &	state
	)

Compute the forward kinematics of the chain, based on the offsets and the joint positions of the state message.

Definition at line 112 of file models.cpp.

std::string robot_calibration::ChainModel::name ( ) const

inline

Definition at line 153 of file chain.h.

std::vector< geometry_msgs::PointStamped > robot_calibration::ChainModel::project ( const robot_calibration_msgs::CalibrationData &  data, const CalibrationOffsetParser &  offsets  )

virtual

Compute the position of the estimated points.

Parameters

data	The calibration data for this observation.
offsets	The offsets that the solver wants to examine.

Reimplemented in robot_calibration::Camera3dModel.

Definition at line 48 of file models.cpp.

Member Data Documentation

KDL::Chain robot_calibration::ChainModel::chain_

private

Definition at line 139 of file chain.h.

std::string robot_calibration::ChainModel::name_

protected

Definition at line 144 of file chain.h.

std::string robot_calibration::ChainModel::root_

protected

Definition at line 142 of file chain.h.

std::string robot_calibration::ChainModel::tip_

protected

Definition at line 143 of file chain.h.

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The documentation for this class was generated from the following files:

• chain.h
• models.cpp