Detailed Description

Impose the constraint p_EScm(q) - p_EC = 0, where p_EScm(q) is a function that computes the center-of-mass (COM) position from robot generalized position q, expressed in a frame E.

p_EC ∈ ℝ³ is the variable representing robot CoM (C) position expressed in frame E. The evaluated variables are [q;r], where q is the generalized position vector of the entire plant.

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

Public Member Functions
	ComPositionConstraint (const MultibodyPlant< double > const plant, std::optional< std::vector< ModelInstanceIndex >> model_instances, const Frame< double > &expressed_frame, systems::Context< double > plant_context)
	Constructor, constrain f(q) = p_EC, where f(q) evaluates the CoM position expressed in frame E using the generalized position q. More...

	ComPositionConstraint (const MultibodyPlant< AutoDiffXd > const plant, std::optional< std::vector< ModelInstanceIndex >> model_instances, const Frame< AutoDiffXd > &expressed_frame, systems::Context< AutoDiffXd > plant_context)
	Overloaded constructor with MultibodyPlant<AutoDiffXd> and Context<AutoDiffXd>. More...

	~ComPositionConstraint () override

template<typename T >
void	ComposeVariable (const Eigen::Ref< const VectorX< T >> &q, const Eigen::Ref< const Vector3< T >> &p_EC, VectorX< T > *variables) const
	Compose the variables for Eval function from generalized position q and the CoM position p_EC. More...

Does not allow copy, move, or assignment
	ComPositionConstraint (const ComPositionConstraint &)=delete

ComPositionConstraint &	operator= (const ComPositionConstraint &)=delete

	ComPositionConstraint (ComPositionConstraint &&)=delete

ComPositionConstraint &	operator= (ComPositionConstraint &&)=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. More...

	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. More...

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`. More...

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. More...

	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. More...

void	Eval (const Eigen::Ref< const AutoDiffVecXd > &x, AutoDiffVecXd *y) const
	Evaluates the expression. More...

void	Eval (const Eigen::Ref< const VectorX< symbolic::Variable >> &x, VectorX< symbolic::Expression > *y) const
	Evaluates the expression. More...

void	set_description (const std::string &description)
	Set a human-friendly description for the evaluator. More...

const std::string &	get_description () const
	Getter for a human-friendly description for the evaluator. More...

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. More...

std::ostream &	Display (std::ostream &os) const
	Formats this evaluator into the given stream, without displaying the decision variables it is bound to. More...

std::string	ToLatex (const VectorX< symbolic::Variable > &vars, int precision=3) const
	Returns a LaTeX string describing this evaluator. More...

int	num_vars () const
	Getter for the number of variables, namely the number of rows in x, as used in Eval(x, y). More...

int	num_outputs () const
	Getter for the number of outputs, namely the number of rows in y, as used in Eval(x, y). More...

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) . More...

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. More...

bool	is_thread_safe () const
	Returns whether it is safe to call Eval in parallel. More...

	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. More...

void	UpdateUpperBound (const Eigen::Ref< const Eigen::VectorXd > &new_ub)
	Updates the upper bound. More...

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. More...

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. More...

virtual std::ostream &	DoDisplay (std::ostream &os, const VectorX< symbolic::Variable > &vars) const
	NVI implementation of Display. More...

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

◆ ComPositionConstraint() [1/4]

ComPositionConstraint ( const ComPositionConstraint & )

delete

◆ ComPositionConstraint() [2/4]

ComPositionConstraint ( ComPositionConstraint && )

delete

◆ ComPositionConstraint() [3/4]

ComPositionConstraint	(	const MultibodyPlant< double > *const	plant,
		std::optional< std::vector< ModelInstanceIndex >>	model_instances,
		const Frame< double > &	expressed_frame,
		systems::Context< double > *	plant_context
	)

Constructor, constrain f(q) = p_EC, where f(q) evaluates the CoM position expressed in frame E using the generalized position q.

Parameters

plant	The MultibodyPlant on which the constraint is imposed. `plant` should be alive during the lifetime of this constraint.
model_instances	We compute the model with these model instances in `plant`. If model_instances=std::nullopt, then we compute the CoM position of all model instances except the world.
expressed_frame	The frame in which the CoM position is expressed.
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.

Exceptions

std::exception if plant or plant_context is nullptr.

◆ ComPositionConstraint() [4/4]

ComPositionConstraint	(	const MultibodyPlant< AutoDiffXd > *const	plant,
		std::optional< std::vector< ModelInstanceIndex >>	model_instances,
		const Frame< AutoDiffXd > &	expressed_frame,
		systems::Context< AutoDiffXd > *	plant_context
	)

Overloaded constructor with MultibodyPlant<AutoDiffXd> and Context<AutoDiffXd>.

It is preferable to use the constructor with MBP<double> and Context<double>. But if you only have MBP<AutoDiffXd> and Context<AutoDiffXd>, then use this constructor.

◆ ~ComPositionConstraint()

~ComPositionConstraint ( )

override

Member Function Documentation

◆ ComposeVariable()

void ComposeVariable	(	const Eigen::Ref< const VectorX< T >> &	q,
		const Eigen::Ref< const Vector3< T >> &	p_EC,
		VectorX< T > *	variables
	)		const

Compose the variables for Eval function from generalized position q and the CoM position p_EC.

◆ operator=() [1/2]

ComPositionConstraint& operator= ( const ComPositionConstraint & )

delete

◆ operator=() [2/2]

ComPositionConstraint& operator= ( ComPositionConstraint && )

delete

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

drake/multibody/inverse_kinematics/com_position_constraint.h

Detailed Description

Public Member Functions

Additional Inherited Members

Constructor & Destructor Documentation

◆ ComPositionConstraint() [1/4]

◆ ComPositionConstraint() [2/4]

◆ ComPositionConstraint() [3/4]

◆ ComPositionConstraint() [4/4]

◆ ~ComPositionConstraint()

Member Function Documentation

◆ ComposeVariable()

◆ operator=() [1/2]

◆ operator=() [2/2]