PointToLineDistanceConstraint Class Reference

Detailed Description

Constrain that the distance between a point P on frame B1 and another line L on frame B2 is within a range [distance_lower, distance_upper].

#include <drake/multibody/inverse_kinematics/point_to_line_distance_constraint.h>

Public Member Functions
	PointToLineDistanceConstraint (const MultibodyPlant< double > *plant, const Frame< double > &frame_point, const Eigen::Ref< const Eigen::Vector3d > &p_B1P, const Frame< double > &frame_line, const Eigen::Ref< const Eigen::Vector3d > &p_B2Q, const Eigen::Ref< const Eigen::Vector3d > &n_B2, double distance_lower, double distance_upper, systems::Context< double > *plant_context)
	Constrain the distance between a point P attached to frame_point (denoted as B1) and the line L attached to frame_line (denoted as B2) is within the range [distance_lower, distance_upper].
	PointToLineDistanceConstraint (const MultibodyPlant< AutoDiffXd > *plant, const Frame< AutoDiffXd > &frame_point, const Eigen::Ref< const Eigen::Vector3d > &p_B1P, const Frame< AutoDiffXd > &frame_line, const Eigen::Ref< const Eigen::Vector3d > &p_B2Q, const Eigen::Ref< const Eigen::Vector3d > &n_B2, double distance_lower, double distance_upper, systems::Context< AutoDiffXd > *plant_context)
	Overloaded constructor.
	~PointToLineDistanceConstraint () override
Does not allow copy, move, or assignment
	PointToLineDistanceConstraint (const PointToLineDistanceConstraint &)=delete
PointToLineDistanceConstraint &	operator= (const PointToLineDistanceConstraint &)=delete
	PointToLineDistanceConstraint (PointToLineDistanceConstraint &&)=delete
PointToLineDistanceConstraint &	operator= (PointToLineDistanceConstraint &&)=delete
Public Member Functions inherited from Constraint
template<typename DerivedLB, typename DerivedUB>
	Constraint (int num_constraints, int num_vars, const Eigen::MatrixBase< DerivedLB > &lb, const Eigen::MatrixBase< DerivedUB > &ub, const std::string &description="")
	Constructs a constraint which has num_constraints rows, with an input num_vars x 1 vector.
	Constraint (int num_constraints, int num_vars)
	Constructs a constraint which has num_constraints rows, with an input num_vars x 1 vector, with no bounds.
bool	CheckSatisfied (const Eigen::Ref< const Eigen::VectorXd > &x, double tol=1E-6) const
	Return whether this constraint is satisfied by the given value, x.
bool	CheckSatisfied (const Eigen::Ref< const AutoDiffVecXd > &x, double tol=1E-6) const
symbolic::Formula	CheckSatisfied (const Eigen::Ref< const VectorX< symbolic::Variable > > &x) const
const Eigen::VectorXd &	lower_bound () const
const Eigen::VectorXd &	upper_bound () const
int	num_constraints () const
	Number of rows in the output constraint.
	Constraint (const Constraint &)=delete
Constraint &	operator= (const Constraint &)=delete
	Constraint (Constraint &&)=delete
Constraint &	operator= (Constraint &&)=delete
Public Member Functions inherited from EvaluatorBase
virtual	~EvaluatorBase ()
void	Eval (const Eigen::Ref< const Eigen::VectorXd > &x, Eigen::VectorXd *y) const
	Evaluates the expression.
void	Eval (const Eigen::Ref< const AutoDiffVecXd > &x, AutoDiffVecXd *y) const
	Evaluates the expression.
void	Eval (const Eigen::Ref< const VectorX< symbolic::Variable > > &x, VectorX< symbolic::Expression > *y) const
	Evaluates the expression.
void	set_description (const std::string &description)
	Set a human-friendly description for the evaluator.
const std::string &	get_description () const
	Getter for a human-friendly description for the evaluator.
std::ostream &	Display (std::ostream &os, const VectorX< symbolic::Variable > &vars) const
	Formats this evaluator into the given stream using vars for the bound decision variable names.
std::ostream &	Display (std::ostream &os) const
	Formats this evaluator into the given stream, without displaying the decision variables it is bound to.
std::string	ToLatex (const VectorX< symbolic::Variable > &vars, int precision=3) const
	Returns a LaTeX string describing this evaluator.
int	num_vars () const
	Getter for the number of variables, namely the number of rows in x, as used in Eval(x, y).
int	num_outputs () const
	Getter for the number of outputs, namely the number of rows in y, as used in Eval(x, y).
void	SetGradientSparsityPattern (const std::vector< std::pair< int, int > > &gradient_sparsity_pattern)
	Set the sparsity pattern of the gradient matrix ∂y/∂x (the gradient of y value in Eval, w.r.t x in Eval) .
const std::optional< std::vector< std::pair< int, int > > > &	gradient_sparsity_pattern () const
	Returns the vector of (row_index, col_index) that contains all the entries in the gradient of Eval function (∂y/∂x) whose value could be non-zero, namely if ∂yᵢ/∂xⱼ could be non-zero, then the pair (i, j) is in gradient_sparsity_pattern.
bool	is_thread_safe () const
	Returns whether it is safe to call Eval in parallel.
	EvaluatorBase (const EvaluatorBase &)=delete
EvaluatorBase &	operator= (const EvaluatorBase &)=delete
	EvaluatorBase (EvaluatorBase &&)=delete
EvaluatorBase &	operator= (EvaluatorBase &&)=delete

Additional Inherited Members
Protected Member Functions inherited from Constraint
void	UpdateLowerBound (const Eigen::Ref< const Eigen::VectorXd > &new_lb)
	Updates the lower bound.
void	UpdateUpperBound (const Eigen::Ref< const Eigen::VectorXd > &new_ub)
	Updates the upper bound.
void	set_bounds (const Eigen::Ref< const Eigen::VectorXd > &new_lb, const Eigen::Ref< const Eigen::VectorXd > &new_ub)
	Set the upper and lower bounds of the constraint.
virtual bool	DoCheckSatisfied (const Eigen::Ref< const Eigen::VectorXd > &x, const double tol) const
virtual bool	DoCheckSatisfied (const Eigen::Ref< const AutoDiffVecXd > &x, const double tol) const
virtual symbolic::Formula	DoCheckSatisfied (const Eigen::Ref< const VectorX< symbolic::Variable > > &x) const
Protected Member Functions inherited from EvaluatorBase
	EvaluatorBase (int num_outputs, int num_vars, const std::string &description="")
	Constructs a evaluator.
virtual std::ostream &	DoDisplay (std::ostream &os, const VectorX< symbolic::Variable > &vars) const
	NVI implementation of Display.
virtual std::string	DoToLatex (const VectorX< symbolic::Variable > &vars, int precision) const
void	set_num_outputs (int num_outputs)
void	set_is_thread_safe (bool is_thread_safe)

Constructor & Destructor Documentation

PointToLineDistanceConstraint() [1/4]

PointToLineDistanceConstraint ( const PointToLineDistanceConstraint & )

delete

PointToLineDistanceConstraint() [2/4]

PointToLineDistanceConstraint ( PointToLineDistanceConstraint && )

delete

PointToLineDistanceConstraint() [3/4]

PointToLineDistanceConstraint	(	const MultibodyPlant< double > *	plant,
		const Frame< double > &	frame_point,
		const Eigen::Ref< const Eigen::Vector3d > &	p_B1P,
		const Frame< double > &	frame_line,
		const Eigen::Ref< const Eigen::Vector3d > &	p_B2Q,
		const Eigen::Ref< const Eigen::Vector3d > &	n_B2,
		double	distance_lower,
		double	distance_upper,
		systems::Context< double > *	plant_context )

Constrain the distance between a point P attached to frame_point (denoted as B1) and the line L attached to frame_line (denoted as B2) is within the range [distance_lower, distance_upper].

Mathematically, we impose the constraint distance_lower² <= distance(P, L)² <= distance_upper². We impose the constraint on the distance square instead of distance directly, because the gradient of distance is not well defined at distance=0; on the other hand, the gradient of the distance square is well defined everywhere.

We parameterize the line using a point Q on the line, and a directional vector n along the line.

Parameters

plant	The MultibodyPlant on which the constraint is imposed. plant must be alive during the lifetime of this constraint.
frame_point	The frame B1 to which the point P is attached.
p_B1P	The position of point P measured and expressed in B1.
frame_line	The frame B2 to which the line is attached.
p_B2Q	Q is a point on the line, p_B2Q is the position of this point Q measured and expressed in B2.
n_B2	n is the directional vector of the line, n_B2 is this vector measured and expressed in B2.
distance_lower	The lower bound on the distance, must be non-negative.
distance_upper	The upper bound on the distance, must be non-negative.
plant_context	The Context that has been allocated for this plant. We will update the context when evaluating the constraint. plant_context must be alive during the lifetime of this constraint.

PointToLineDistanceConstraint() [4/4]

PointToLineDistanceConstraint	(	const MultibodyPlant< AutoDiffXd > *	plant,
		const Frame< AutoDiffXd > &	frame_point,
		const Eigen::Ref< const Eigen::Vector3d > &	p_B1P,
		const Frame< AutoDiffXd > &	frame_line,
		const Eigen::Ref< const Eigen::Vector3d > &	p_B2Q,
		const Eigen::Ref< const Eigen::Vector3d > &	n_B2,
		double	distance_lower,
		double	distance_upper,
		systems::Context< AutoDiffXd > *	plant_context )

Overloaded constructor.

Same as the constructor with the double version (using MultibodyPlant<double> and Context<double>), except the gradient of the constraint is computed from autodiff.

~PointToLineDistanceConstraint()

~PointToLineDistanceConstraint ( )

override

Member Function Documentation

operator=() [1/2]

PointToLineDistanceConstraint & operator= ( const PointToLineDistanceConstraint & )

delete

operator=() [2/2]

PointToLineDistanceConstraint & operator= ( PointToLineDistanceConstraint && )

delete

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

• drake/multibody/inverse_kinematics/point_to_line_distance_constraint.h