ompl::control::KPIECE1 Class Reference

Kinodynamic Planning by Interior-Exterior Cell Exploration. More...

#include <KPIECE1.h>

Inheritance diagram for ompl::control::KPIECE1:

Classes
struct	CellData
	The data held by a cell in the grid of motions. More...
class	Motion
	Representation of a motion for this algorithm. More...
struct	OrderCellsByImportance
	Definintion of an operator passed to the Grid structure, to order cells by importance. More...
struct	TreeData
	The data defining a tree of motions for this algorithm. More...
Public Member Functions
virtual void	clear (void)
	Clear all internal datastructures. Planner settings are not affected. Subsequent calls to solve() will ignore all previous work.
double	getBadCellScoreFactor (void) const
	Get the factor that is multiplied to a cell's score if extending a motion from that cell failed.
double	getBorderFraction (void) const
	Get the fraction of time to focus exploration on boundary.
double	getGoalBias (void) const
double	getGoodCellScoreFactor (void) const
	Get the factor that is multiplied to a cell's score if extending a motion from that cell succeeded.
virtual void	getPlannerData (base::PlannerData &data) const
	Get information about the current run of the motion planner. Repeated calls to this function will update data (only additions are made). This is useful to see what changed in the exploration datastructure, between calls to solve(), for example (without calling clear() in between).
const base::ProjectionEvaluatorPtr &	getProjectionEvaluator (void) const
	Get the projection evaluator.
	KPIECE1 (const SpaceInformationPtr &si)
	Constructor.
void	setBorderFraction (double bp)
	Set the fraction of time for focusing on the border (between 0 and 1). This is the minimum fraction used to select cells that are exterior (minimum because if 95% of cells are on the border, they will be selected with 95% chance, even if this fraction is set to 90%).
void	setCellScoreFactor (double good, double bad)
	When extending a motion from a cell, the extension can be successful or it can fail. If the extension is successful, the score of the cell is multiplied by good. If the extension fails, the score of the cell is multiplied by bad. These numbers should be in the range (0, 1].
void	setGoalBias (double goalBias)
void	setProjectionEvaluator (const std::string &name)
	Set the projection evaluator (select one from the ones registered with the state space).
void	setProjectionEvaluator (const base::ProjectionEvaluatorPtr &projectionEvaluator)
	Set the projection evaluator. This class is able to compute the projection of a given state.
virtual void	setup (void)
	Perform extra configuration steps, if needed. This call will also issue a call to ompl::base::SpaceInformation::setup() if needed. This must be called before solving.
virtual bool	solve (const base::PlannerTerminationCondition &ptc)
	Function that can solve the motion planning problem. This function can be called multiple times on the same problem, without calling clear() in between. This allows the planner to continue work more time on an unsolved problem, for example. If this option is used, it is assumed the problem definition is not changed (unpredictable results otherwise). The only change in the problem definition that is accounted for is the addition of starting or goal states (but not changing previously added start/goal states). The function terminates if the call to ptc returns true.
virtual	~KPIECE1 (void)
Protected Types
typedef GridB< CellData *, OrderCellsByImportance >	Grid
	The datatype for the maintained grid datastructure.
Protected Member Functions
unsigned int	addMotion (Motion *motion, double dist)
	Add a motion to the grid containing motions. As a hint, dist specifies the distance to the goal from the state of the motion being added. The function Returns the number of cells created to accommodate the new motion (0 or 1).
unsigned int	findNextMotion (const std::vector< Grid::Coord > &coords, unsigned int index, unsigned int count)
	When generated motions are to be added to the tree of motions, they often need to be split, so they don't cross cell boundaries. Given that a motion starts out in the cell origin and it crosses the cells in coords[index] through coords[last] (inclusively), return the index of the state to be used in the next part of the motion (that is within a cell). This will be a value between index and last.
void	freeCellData (CellData *cdata)
	Free the memory for the data contained in a grid cell.
void	freeGridMotions (Grid &grid)
	Free the memory for the motions contained in a grid.
void	freeMemory (void)
	Free all the memory allocated by this planner.
void	freeMotion (Motion *motion)
	Free the memory for a motion.
bool	selectMotion (Motion &smotion, Grid::Cell &scell)
	Select a motion and the cell it is part of from the grid of motions. This is where preference is given to cells on the boundary of the grid.
Static Protected Member Functions
static void	computeImportance (Grid::Cell cell, void )
	This function is provided as a calback to the grid datastructure to update the importance of a cell.
Protected Attributes
double	badScoreFactor_
	When extending a motion from a cell, the extension can fail. If it is, the score of the cell is multiplied by this factor.
ControlSamplerPtr	controlSampler_
	A control sampler.
double	goalBias_
	The fraction of time the goal is picked as the state to expand towards (if such a state is available).
double	goodScoreFactor_
	When extending a motion from a cell, the extension can be successful. If it is, the score of the cell is multiplied by this factor.
base::ProjectionEvaluatorPtr	projectionEvaluator_
	This algorithm uses a discretization (a grid) to guide the exploration. The exploration is imposed on a projection of the state space.
RNG	rng_
	The random number generator.
double	selectBorderFraction_
	The fraction of time to focus exploration on the border of the grid.
const SpaceInformation *	siC_
	The base::SpaceInformation cast as control::SpaceInformation, for convenience.
TreeData	tree_
	The tree datastructure.

Detailed Description

Kinodynamic Planning by Interior-Exterior Cell Exploration.

Short description: KPIECE is a tree-based planner that uses a discretization (multiple levels, in general) to guide the exploration of the continuous space. This implementation is a simplified one, using a single level of discretization: one grid. The grid is imposed on a projection of the state space. When exploring the space, preference is given to the boundary of this grid. The boundary is computed to be the set of grid cells that have less than 2n non-diagonal neighbors in an n-dimensional projection space. It is important to set the projection the algorithm uses (setProjectionEvaluator() function). If no projection is set, the planner will attempt to use the default projection associated to the state space. An exception is thrown if no default projection is available either. This implementation is intended for systems with differential constraints.

External documentation: I.A. Şucan and L.E. Kavraki, Kinodynamic motion planning by interior-exterior cell exploration, in Workshop on the Algorithmic Foundations of Robotics, Dec. 2008.
[PDF]

Definition at line 72 of file control/planners/kpiece/KPIECE1.h.

Member Typedef Documentation

typedef GridB<CellData*, OrderCellsByImportance> ompl::control::KPIECE1::Grid [protected]

The datatype for the maintained grid datastructure.

Definition at line 234 of file control/planners/kpiece/KPIECE1.h.

Constructor & Destructor Documentation

ompl::control::KPIECE1::KPIECE1 ( const SpaceInformationPtr & si ) [inline]

Constructor.

Definition at line 47 of file control/planners/kpiece/KPIECE1.h.

virtual ompl::control::KPIECE1::~KPIECE1 ( void ) [inline, virtual]

Definition at line 59 of file control/planners/kpiece/KPIECE1.h.

Member Function Documentation

unsigned int ompl::control::KPIECE1::addMotion	(	Motion *	motion,
		double	dist
	)			`[protected]`

Add a motion to the grid containing motions. As a hint, dist specifies the distance to the goal from the state of the motion being added. The function Returns the number of cells created to accommodate the new motion (0 or 1).

virtual void ompl::control::KPIECE1::clear ( void ) [virtual]

Clear all internal datastructures. Planner settings are not affected. Subsequent calls to solve() will ignore all previous work.

Reimplemented from ompl::base::Planner.

static void ompl::control::KPIECE1::computeImportance	(	Grid::Cell *	cell,
		void *
	)			`[inline, static, protected]`

This function is provided as a calback to the grid datastructure to update the importance of a cell.

Definition at line 258 of file control/planners/kpiece/KPIECE1.h.

unsigned int ompl::control::KPIECE1::findNextMotion	(	const std::vector< Grid::Coord > &	coords,
		unsigned int	index,
		unsigned int	count
	)			`[protected]`

When generated motions are to be added to the tree of motions, they often need to be split, so they don't cross cell boundaries. Given that a motion starts out in the cell origin and it crosses the cells in coords[index] through coords[last] (inclusively), return the index of the state to be used in the next part of the motion (that is within a cell). This will be a value between index and last.

void ompl::control::KPIECE1::freeCellData ( CellData * cdata ) [protected]

Free the memory for the data contained in a grid cell.

void ompl::control::KPIECE1::freeGridMotions ( Grid & grid ) [protected]

Free the memory for the motions contained in a grid.

void ompl::control::KPIECE1::freeMemory ( void ) [protected]

Free all the memory allocated by this planner.

void ompl::control::KPIECE1::freeMotion ( Motion * motion ) [protected]

Free the memory for a motion.

double ompl::control::KPIECE1::getBadCellScoreFactor ( void ) const [inline]

Get the factor that is multiplied to a cell's score if extending a motion from that cell failed.

Definition at line 126 of file control/planners/kpiece/KPIECE1.h.

double ompl::control::KPIECE1::getBorderFraction ( void ) const [inline]

Get the fraction of time to focus exploration on boundary.

Definition at line 99 of file control/planners/kpiece/KPIECE1.h.

double ompl::control::KPIECE1::getGoalBias ( void ) const [inline]

Get the goal bias the planner is using

Definition at line 81 of file control/planners/kpiece/KPIECE1.h.

double ompl::control::KPIECE1::getGoodCellScoreFactor ( void ) const [inline]

Get the factor that is multiplied to a cell's score if extending a motion from that cell succeeded.

Definition at line 119 of file control/planners/kpiece/KPIECE1.h.

virtual void ompl::control::KPIECE1::getPlannerData ( base::PlannerData & data ) const [virtual]

Get information about the current run of the motion planner. Repeated calls to this function will update data (only additions are made). This is useful to see what changed in the exploration datastructure, between calls to solve(), for example (without calling clear() in between).

Reimplemented from ompl::base::Planner.

const base::ProjectionEvaluatorPtr& ompl::control::KPIECE1::getProjectionEvaluator ( void ) const [inline]

Get the projection evaluator.

Definition at line 146 of file control/planners/kpiece/KPIECE1.h.

bool ompl::control::KPIECE1::selectMotion	(	Motion *&	smotion,
		Grid::Cell *&	scell
	)			`[protected]`

Select a motion and the cell it is part of from the grid of motions. This is where preference is given to cells on the boundary of the grid.

void ompl::control::KPIECE1::setBorderFraction ( double bp ) [inline]

Set the fraction of time for focusing on the border (between 0 and 1). This is the minimum fraction used to select cells that are exterior (minimum because if 95% of cells are on the border, they will be selected with 95% chance, even if this fraction is set to 90%).

Definition at line 92 of file control/planners/kpiece/KPIECE1.h.

void ompl::control::KPIECE1::setCellScoreFactor	(	double	good,
		double	bad
	)			`[inline]`

When extending a motion from a cell, the extension can be successful or it can fail. If the extension is successful, the score of the cell is multiplied by good. If the extension fails, the score of the cell is multiplied by bad. These numbers should be in the range (0, 1].

Definition at line 111 of file control/planners/kpiece/KPIECE1.h.

void ompl::control::KPIECE1::setGoalBias ( double goalBias ) [inline]

In the process of randomly selecting states in the state space to attempt to go towards, the algorithm may in fact choose the actual goal state, if it knows it, with some probability. This probability is a real number between 0.0 and 1.0; its value should usually be around 0.05 and should not be too large. It is probably a good idea to use the default value.

Definition at line 75 of file control/planners/kpiece/KPIECE1.h.

void ompl::control::KPIECE1::setProjectionEvaluator ( const std::string & name ) [inline]

Set the projection evaluator (select one from the ones registered with the state space).

Definition at line 140 of file control/planners/kpiece/KPIECE1.h.

void ompl::control::KPIECE1::setProjectionEvaluator ( const base::ProjectionEvaluatorPtr & projectionEvaluator ) [inline]

Set the projection evaluator. This class is able to compute the projection of a given state.

Definition at line 133 of file control/planners/kpiece/KPIECE1.h.

virtual void ompl::control::KPIECE1::setup ( void ) [virtual]

Perform extra configuration steps, if needed. This call will also issue a call to ompl::base::SpaceInformation::setup() if needed. This must be called before solving.

Reimplemented from ompl::base::Planner.

virtual bool ompl::control::KPIECE1::solve ( const base::PlannerTerminationCondition & ptc ) [virtual]

Function that can solve the motion planning problem. This function can be called multiple times on the same problem, without calling clear() in between. This allows the planner to continue work more time on an unsolved problem, for example. If this option is used, it is assumed the problem definition is not changed (unpredictable results otherwise). The only change in the problem definition that is accounted for is the addition of starting or goal states (but not changing previously added start/goal states). The function terminates if the call to ptc returns true.

Implements ompl::base::Planner.