Detailed Description

Constrains the position of a point Q, rigidly attached to a frame B, to be within a bounding box measured and expressed in frame A.

Namely p_AQ_lower <= p_AQ <= p_AQ_upper.

Note that p_BQ may or may not be a decision variable. Common use cases include:

We want a specified point Q on the frame B to be within a bounding box. In this case, p_BQ is specified and not a decision variable.
We want some point Q on the frame B to be within a bounding box, but we don't know the exact position of Q on the frame B. For example, we want some point on the robot palm to touch a table, but we don't care which point on the robot palm. In this case, p_BQ is a decision variable, and we need an additional constraint to say "Q is on the surface of the robot palm".

When p_BQ is a decision variable (i.e., it is not specified in the ctor), the constraint is evaluated on the vector x = [q, p_BQ]. When p_BQ is not a decision variable (i.e. it is specified non-nulloptin the ctor), the constraint is evaluated on the vector x = q.

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

Public Member Functions
	PositionConstraint (const MultibodyPlant< double > plant, const Frame< double > &frameA, const Eigen::Ref< const Eigen::Vector3d > &p_AQ_lower, const Eigen::Ref< const Eigen::Vector3d > &p_AQ_upper, const Frame< double > &frameB, std::optional< Eigen::Vector3d > p_BQ, systems::Context< double > plant_context)
	Constructs PositionConstraint object.
	PositionConstraint (const MultibodyPlant< AutoDiffXd > plant, const Frame< AutoDiffXd > &frameA, const Eigen::Ref< const Eigen::Vector3d > &p_AQ_lower, const Eigen::Ref< const Eigen::Vector3d > &p_AQ_upper, const Frame< AutoDiffXd > &frameB, std::optional< Eigen::Vector3d > p_BQ, systems::Context< AutoDiffXd > plant_context)
	Overloaded constructor.
	PositionConstraint (const MultibodyPlant< double > plant, const Frame< double > &frameAbar, const std::optional< math::RigidTransformd > &X_AbarA, const Eigen::Ref< const Eigen::Vector3d > &p_AQ_lower, const Eigen::Ref< const Eigen::Vector3d > &p_AQ_upper, const Frame< double > &frameB, std::optional< Eigen::Vector3d > p_BQ, systems::Context< double > plant_context)
	Overloaded constructor.
	PositionConstraint (const MultibodyPlant< AutoDiffXd > plant, const Frame< AutoDiffXd > &frameAbar, const std::optional< math::RigidTransformd > &X_AbarA, const Eigen::Ref< const Eigen::Vector3d > &p_AQ_lower, const Eigen::Ref< const Eigen::Vector3d > &p_AQ_upper, const Frame< AutoDiffXd > &frameB, std::optional< Eigen::Vector3d > p_BQ, systems::Context< AutoDiffXd > plant_context)
	Overloaded constructor.
	~PositionConstraint () override
Does not allow copy, move, or assignment
	PositionConstraint (const PositionConstraint &)=delete
PositionConstraint &	operator= (const PositionConstraint &)=delete
	PositionConstraint (PositionConstraint &&)=delete
PositionConstraint &	operator= (PositionConstraint &&)=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

◆ PositionConstraint() [1/6]

PositionConstraint ( const PositionConstraint & )

delete

◆ PositionConstraint() [2/6]

PositionConstraint ( PositionConstraint && )

delete

◆ PositionConstraint() [3/6]

PositionConstraint	(	const MultibodyPlant< double > *	plant,
		const Frame< double > &	frameA,
		const Eigen::Ref< const Eigen::Vector3d > &	p_AQ_lower,
		const Eigen::Ref< const Eigen::Vector3d > &	p_AQ_upper,
		const Frame< double > &	frameB,
		std::optional< Eigen::Vector3d >	p_BQ,
		systems::Context< double > *	plant_context )

Constructs PositionConstraint object.

Parameters

plant	The MultibodyPlant on which the constraint is imposed. plant should be alive during the lifetime of this constraint.
frameA	The frame in which point Q's position is measured.
p_AQ_lower	The lower bound on the position of point Q, measured and expressed in frame A.
p_AQ_upper	The upper bound on the position of point Q, measured and expressed in frame A.
frameB	The frame to which point Q is rigidly attached.
p_BQ	The position of the point Q, rigidly attached to frame B, measured and expressed in frame B. If set to nullopt, then p_BQ is also a decision variable.
plant_context	The Context that has been allocated for this plant. We will update the context when evaluating the constraint. plant_context should be alive during the lifetime of this constraint.

Precondition: frameA and frameB must belong to plant.; p_AQ_lower(i) <= p_AQ_upper(i) for i = 1, 2, 3.

Exceptions

std::exception	if plant is nullptr.
std::exception	if plant_context is nullptr.

◆ PositionConstraint() [4/6]

PositionConstraint	(	const MultibodyPlant< AutoDiffXd > *	plant,
		const Frame< AutoDiffXd > &	frameA,
		const Eigen::Ref< const Eigen::Vector3d > &	p_AQ_lower,
		const Eigen::Ref< const Eigen::Vector3d > &	p_AQ_upper,
		const Frame< AutoDiffXd > &	frameB,
		std::optional< Eigen::Vector3d >	p_BQ,
		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.

◆ PositionConstraint() [5/6]

PositionConstraint	(	const MultibodyPlant< double > *	plant,
		const Frame< double > &	frameAbar,
		const std::optional< math::RigidTransformd > &	X_AbarA,
		const Eigen::Ref< const Eigen::Vector3d > &	p_AQ_lower,
		const Eigen::Ref< const Eigen::Vector3d > &	p_AQ_upper,
		const Frame< double > &	frameB,
		std::optional< Eigen::Vector3d >	p_BQ,
		systems::Context< double > *	plant_context )

Overloaded constructor.

Except that the constructor takes in a frame A̅ and a pose X_AAbar between the frame A and A̅. We will constrain the position of point Q expressed in the frame A to lie within a bounding box of A.

Parameters

plant	The MultibodyPlant on which the constraint is imposed. plant should be alive during the lifetime of this constraint.
frameAbar	The frame A̅ in which point Q's position is measured.
X_AbarA	relative transform between the frame A̅ and A. If empty, then we use identity transform.
p_AQ_lower	The lower bound on the position of point Q, measured and expressed in frame A.
p_AQ_upper	The upper bound on the position of point Q, measured and expressed in frame A.
frameB	The frame to which point Q is rigidly attached.
p_BQ	The position of the point Q, rigidly attached to frame B, measured and expressed in frame B. If set to nullopt, then p_BQ is also a decision variable.
plant_context	The Context that has been allocated for this plant. We will update the context when evaluating the constraint. plant_context should be alive during the lifetime of this constraint.

Precondition: frameA and frameB must belong to plant.; p_AQ_lower(i) <= p_AQ_upper(i) for i = 1, 2, 3.

Exceptions

std::exception	if plant is nullptr.
std::exception	if plant_context is nullptr.

◆ PositionConstraint() [6/6]

PositionConstraint	(	const MultibodyPlant< AutoDiffXd > *	plant,
		const Frame< AutoDiffXd > &	frameAbar,
		const std::optional< math::RigidTransformd > &	X_AbarA,
		const Eigen::Ref< const Eigen::Vector3d > &	p_AQ_lower,
		const Eigen::Ref< const Eigen::Vector3d > &	p_AQ_upper,
		const Frame< AutoDiffXd > &	frameB,
		std::optional< Eigen::Vector3d >	p_BQ,
		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.

◆ ~PositionConstraint()

~PositionConstraint ( )

override

Member Function Documentation

◆ operator=() [1/2]

PositionConstraint & operator= ( const PositionConstraint & )

delete

◆ operator=() [2/2]

PositionConstraint & operator= ( PositionConstraint && )

delete

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

drake/multibody/inverse_kinematics/position_constraint.h

Detailed Description

Public Member Functions

Additional Inherited Members

Constructor & Destructor Documentation

◆ PositionConstraint() [1/6]

◆ PositionConstraint() [2/6]

◆ PositionConstraint() [3/6]

◆ PositionConstraint() [4/6]

◆ PositionConstraint() [5/6]

◆ PositionConstraint() [6/6]

◆ ~PositionConstraint()

Member Function Documentation

◆ operator=() [1/2]

◆ operator=() [2/2]