Detailed Description

Constrain min(d) <= ub, namely at least one signed distance between a candidate pairs of geometries (according to the logic of SceneGraphInspector::GetCollisionCandidates()) to be no larger than a specified ub.

This constraint should be bound to decision variables corresponding to the configuration vector, q, of the associated MultibodyPlant.

The formulation of the constraint is

SmoothUnderMax( φ((dᵢ(q) - d_influence)/(d_influence - ub)) / φ(-1) ) ≥ 1

where dᵢ(q) is the signed distance of the i-th pair, ub is the upper bound of the minimum distance, d_influence is the "influence distance" (the distance below which a pair of geometries influences the constraint), φ is a solvers::MinimumValuePenaltyFunction. SmoothUnderMax(d) is smooth under approximation of max(d). We require that ub < d_influence. The input scaling (dᵢ(q) - d_influence)/(d_influence - ub) ensures that at the boundary of the feasible set (when dᵢ(q) == ub), we evaluate the penalty function at -1, where it is required to have a non-zero gradient.

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

Public Member Functions
	MinimumDistanceUpperBoundConstraint (const multibody::MultibodyPlant< double > const plant, double bound, systems::Context< double > plant_context, double influence_distance_offset, solvers::MinimumValuePenaltyFunction penalty_function={})
	Constructs a MinimumDistanceUpperBoundConstraint. More...

	MinimumDistanceUpperBoundConstraint (const multibody::MultibodyPlant< AutoDiffXd > const plant, double bound, systems::Context< AutoDiffXd > plant_context, double influence_value_offset, solvers::MinimumValuePenaltyFunction penalty_function={})
	Overloaded constructor. More...

	MinimumDistanceUpperBoundConstraint (const planning::CollisionChecker collision_checker, double bound, planning::CollisionCheckerContext collision_checker_context, double influence_distance_offset, solvers::MinimumValuePenaltyFunction penalty_function={})
	Overloaded constructor. More...

	~MinimumDistanceUpperBoundConstraint () override

double	distance_bound () const
	Getter for the upper bound of the minimum distance. More...

double	influence_distance () const
	Getter for the influence distance. More...

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

MinimumDistanceUpperBoundConstraint &	operator= (const MinimumDistanceUpperBoundConstraint &)=delete

	MinimumDistanceUpperBoundConstraint (MinimumDistanceUpperBoundConstraint &&)=delete

MinimumDistanceUpperBoundConstraint &	operator= (MinimumDistanceUpperBoundConstraint &&)=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...

	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)

Constructor & Destructor Documentation

◆ MinimumDistanceUpperBoundConstraint() [1/5]

MinimumDistanceUpperBoundConstraint ( const MinimumDistanceUpperBoundConstraint & )

delete

◆ MinimumDistanceUpperBoundConstraint() [2/5]

MinimumDistanceUpperBoundConstraint ( MinimumDistanceUpperBoundConstraint && )

delete

◆ MinimumDistanceUpperBoundConstraint() [3/5]

MinimumDistanceUpperBoundConstraint	(	const multibody::MultibodyPlant< double > *const	plant,
		double	bound,
		systems::Context< double > *	plant_context,
		double	influence_distance_offset,
		solvers::MinimumValuePenaltyFunction	penalty_function = `{}`
	)

Constructs a MinimumDistanceUpperBoundConstraint.

Parameters

plant	The multibody system on which the constraint will be evaluated.
bound	`ub` in the class documentation. The upper bound minimum signed distance between any candidate pair of geometries.
plant_context	The context of `plant`. The context should be obtained as a subsystem context from the diagram context, where the diagram (that contains both the MultibodyPlant and SceneGraph) creates the diagram context. `plant_context` cannot be a nullptr. `plant_context` must outlive this constraint. An example code of getting the plant context is auto diagram_context = diagram.CreateDefaultContext(); auto plant_context = plant.GetMyMutableContextFromRoot(diagram_context.get());
penalty_function	The penalty function formulation. Default: QuadraticallySmoothedHinge
influence_distance_offset	The difference (in meters) between the influence distance, d_influence, and the minimum distance_upper, ub (see class documentation), namely influence_distance = bound + influence_distance_offset. This value must be finite and strictly positive, as it is used to scale the signed distances between pairs of geometries. Larger value might increase the possibility of finding a solution through gradient based nonlinear optimization. This is because a geometry pair with distance larger than `influence_distance` is ignored, so is its gradient; hence the gradient-based optimizer doesn't know to actively reduce the distance between that pair. We strongly suggest to use a different (and larger) `influence_distance_offset` as the one used in MinimumValueLowerBoundConstraint.

Exceptions

std::exception	if `plant` has not registered its geometry with a SceneGraph object.
std::exception	if influence_distance_offset = ∞.
std::exception	if influence_distance_offset ≤ 0.

◆ MinimumDistanceUpperBoundConstraint() [4/5]

MinimumDistanceUpperBoundConstraint	(	const multibody::MultibodyPlant< AutoDiffXd > *const	plant,
		double	bound,
		systems::Context< AutoDiffXd > *	plant_context,
		double	influence_value_offset,
		solvers::MinimumValuePenaltyFunction	penalty_function = `{}`
	)

Overloaded constructor.

Constructs the constraint using MultibodyPlant<AutoDiffXd>.

◆ MinimumDistanceUpperBoundConstraint() [5/5]

MinimumDistanceUpperBoundConstraint	(	const planning::CollisionChecker *	collision_checker,
		double	bound,
		planning::CollisionCheckerContext *	collision_checker_context,
		double	influence_distance_offset,
		solvers::MinimumValuePenaltyFunction	penalty_function = `{}`
	)

Overloaded constructor.

Constructs the constraint with CollisionChecker instead of MultibodyPlant.

Parameters

collision_checker	collision_checker must outlive this constraint.
collision_checker_context	The context for the collision checker. See CollisionChecker class for more details.

◆ ~MinimumDistanceUpperBoundConstraint()

~MinimumDistanceUpperBoundConstraint ( )

override

Member Function Documentation

◆ distance_bound()

double distance_bound ( ) const

Getter for the upper bound of the minimum distance.

◆ influence_distance()

double influence_distance ( ) const

Getter for the influence distance.

◆ operator=() [1/2]

MinimumDistanceUpperBoundConstraint& operator= ( const MinimumDistanceUpperBoundConstraint & )

delete

◆ operator=() [2/2]

MinimumDistanceUpperBoundConstraint& operator= ( MinimumDistanceUpperBoundConstraint && )

delete

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

drake/multibody/inverse_kinematics/minimum_distance_upper_bound_constraint.h

Detailed Description

Public Member Functions

Additional Inherited Members

Constructor & Destructor Documentation

◆ MinimumDistanceUpperBoundConstraint() [1/5]

◆ MinimumDistanceUpperBoundConstraint() [2/5]

◆ MinimumDistanceUpperBoundConstraint() [3/5]

◆ MinimumDistanceUpperBoundConstraint() [4/5]

◆ MinimumDistanceUpperBoundConstraint() [5/5]

◆ ~MinimumDistanceUpperBoundConstraint()

Member Function Documentation

◆ distance_bound()

◆ influence_distance()

◆ operator=() [1/2]

◆ operator=() [2/2]