Detailed Description

Constrains the center of mass to lie within a polyhedron lb <= A * p_EC <= ub where p_EC is the position of the center-of-mass (C) expressed in a frame E.

For example, if you set A as identity matrix, then this constraint enforces a box-region on the CoM position p_EC. If you set the expressed frame E as the robot foot frame, and choose A to describe the foot support polygon, this constraint could enforce the projection of CoM to be within the foot support polygon, which is commonly used to ensure static equilibrium.

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

Public Member Functions
	ComInPolyhedronConstraint (const MultibodyPlant< double > plant, std::optional< std::vector< ModelInstanceIndex > > model_instances, const Frame< double > &expressed_frame, const Eigen::Ref< const Eigen::MatrixX3d > &A, const Eigen::Ref< const Eigen::VectorXd > &lb, const Eigen::Ref< const Eigen::VectorXd > &ub, systems::Context< double > plant_context)
	Constructs a ComInPolyhedronConstraint object.
	ComInPolyhedronConstraint (const MultibodyPlant< AutoDiffXd > plant, std::optional< std::vector< ModelInstanceIndex > > model_instances, const Frame< AutoDiffXd > &expressed_frame, const Eigen::Ref< const Eigen::MatrixX3d > &A, const Eigen::Ref< const Eigen::VectorXd > &lb, const Eigen::Ref< const Eigen::VectorXd > &ub, systems::Context< AutoDiffXd > plant_context)
	Overloaded constructor.
	~ComInPolyhedronConstraint () override
Does not allow copy, move, or assignment
	ComInPolyhedronConstraint (const ComInPolyhedronConstraint &)=delete
ComInPolyhedronConstraint &	operator= (const ComInPolyhedronConstraint &)=delete
	ComInPolyhedronConstraint (ComInPolyhedronConstraint &&)=delete
ComInPolyhedronConstraint &	operator= (ComInPolyhedronConstraint &&)=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

◆ ComInPolyhedronConstraint() [1/4]

ComInPolyhedronConstraint ( const ComInPolyhedronConstraint & )

delete

◆ ComInPolyhedronConstraint() [2/4]

ComInPolyhedronConstraint ( ComInPolyhedronConstraint && )

delete

◆ ComInPolyhedronConstraint() [3/4]

ComInPolyhedronConstraint	(	const MultibodyPlant< double > *	plant,
		std::optional< std::vector< ModelInstanceIndex > >	model_instances,
		const Frame< double > &	expressed_frame,
		const Eigen::Ref< const Eigen::MatrixX3d > &	A,
		const Eigen::Ref< const Eigen::VectorXd > &	lb,
		const Eigen::Ref< const Eigen::VectorXd > &	ub,
		systems::Context< double > *	plant_context )

Constructs a ComInPolyhedronConstraint object.

Parameters

plant	The MultibodyPlant on which the constraint is imposed. plant must be alive during the lifetime of this constraint.
model_instances	The CoM of these model instances are computed. If model_instances = std::nullopt, then we compute the CoM of all model instances (except the world).
expressed_frame	The frame in which the CoM is expressed.
A	The CoM position p_EC satisfies lb <= A * p_EC <= ub
lb	The CoM position p_EC satisfies lb <= A * p_EC <= ub
ub	The CoM position p_EC satisfies lb <= A * p_EC <= ub
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.

◆ ComInPolyhedronConstraint() [4/4]

ComInPolyhedronConstraint	(	const MultibodyPlant< AutoDiffXd > *	plant,
		std::optional< std::vector< ModelInstanceIndex > >	model_instances,
		const Frame< AutoDiffXd > &	expressed_frame,
		const Eigen::Ref< const Eigen::MatrixX3d > &	A,
		const Eigen::Ref< const Eigen::VectorXd > &	lb,
		const Eigen::Ref< const Eigen::VectorXd > &	ub,
		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.

Precondition: if model_instances is not std::nullopt, then all indices in model_instances refer to valid model instances in plant.

◆ ~ComInPolyhedronConstraint()

~ComInPolyhedronConstraint ( )

override

Member Function Documentation

◆ operator=() [1/2]

ComInPolyhedronConstraint & operator= ( ComInPolyhedronConstraint && )

delete

◆ operator=() [2/2]

ComInPolyhedronConstraint & operator= ( const ComInPolyhedronConstraint & )

delete

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

drake/multibody/inverse_kinematics/com_in_polyhedron_constraint.h

Detailed Description

Public Member Functions

Additional Inherited Members

Constructor & Destructor Documentation

◆ ComInPolyhedronConstraint() [1/4]

◆ ComInPolyhedronConstraint() [2/4]

◆ ComInPolyhedronConstraint() [3/4]

◆ ComInPolyhedronConstraint() [4/4]

◆ ~ComInPolyhedronConstraint()

Member Function Documentation

◆ operator=() [1/2]

◆ operator=() [2/2]