towr::ForceConstraint Class Reference

Ensures foot force that is unilateral and inside friction cone. More...

#include <force_constraint.h>

Inheritance diagram for towr::ForceConstraint:

Public Types
using	EE = uint
using	Vector3d = Eigen::Vector3d
Public Types inherited from ifopt::ConstraintSet
typedef std::shared_ptr< ConstraintSet >	Ptr
typedef Composite::Ptr	VariablesPtr
Public Types inherited from ifopt::Component
typedef Eigen::SparseMatrix< double, Eigen::RowMajor >	Jacobian
typedef std::shared_ptr< Component >	Ptr
typedef std::vector< Bounds >	VecBound
typedef Eigen::VectorXd	VectorXd

Public Member Functions
void	FillJacobianBlock (std::string var_set, Jacobian &) const override
	ForceConstraint (const HeightMap::Ptr &terrain, double force_limit_in_normal_direction, EE endeffector_id)
	Constructs a force contraint. More...
VecBound	GetBounds () const override
VectorXd	GetValues () const override
void	InitVariableDependedQuantities (const VariablesPtr &x) override
virtual	~ForceConstraint ()=default
Public Member Functions inherited from ifopt::ConstraintSet
	ConstraintSet (int n_constraints, const std::string &name)
Jacobian	GetJacobian () const final
void	LinkWithVariables (const VariablesPtr &x)
virtual	~ConstraintSet ()=default
Public Member Functions inherited from ifopt::Component
	Component (int num_rows, const std::string &name)
std::string	GetName () const
int	GetRows () const
virtual void	Print (double tolerance, int &index_start) const
void	SetRows (int num_rows)
virtual	~Component ()=default

Private Attributes
EE	ee_
	The endeffector force to be constrained. More...
NodesVariablesPhaseBased::Ptr	ee_force_
	the current xyz foot forces. More...
NodesVariablesPhaseBased::Ptr	ee_motion_
	the current xyz foot positions. More...
double	fn_max_
	force limit in normal direction. More...
double	mu_
	friction coeff between robot feet and terrain. More...
int	n_constraints_per_node_
	number of constraint for each node. More...
std::vector< int >	pure_stance_force_node_ids_
HeightMap::Ptr	terrain_
	gradient information at every position (x,y). More...

Additional Inherited Members
Static Public Attributes inherited from ifopt::Component
static const int	kSpecifyLater
Protected Member Functions inherited from ifopt::ConstraintSet
const VariablesPtr	GetVariables () const

Detailed Description

Ensures foot force that is unilateral and inside friction cone.

This class is responsible for constraining the endeffector xyz-forces to only push into the terrain and additionally stay inside the friction cone according to the current slope.

In order to keep the constraint linear and simple for the solver to solve, we approximate the friction cone by a 4-sided pyramid.

Attention: Constraint is enforced only at the spline nodes. In between violations of this constraint can occur.

Definition at line 55 of file force_constraint.h.

Member Typedef Documentation

EE

using towr::ForceConstraint::EE = uint

Definition at line 58 of file force_constraint.h.

Vector3d

using towr::ForceConstraint::Vector3d = Eigen::Vector3d

Definition at line 57 of file force_constraint.h.

Constructor & Destructor Documentation

ForceConstraint()

towr::ForceConstraint::ForceConstraint	(	const HeightMap::Ptr &	terrain,
		double	force_limit_in_normal_direction,
		EE	endeffector_id
	)

Constructs a force contraint.

Parameters

terrain	The gradient information of the terrain for friction cone.
force_limit_in_normal_direction	Maximum pushing force [N].
endeffector_id	Which endeffector force should be constrained.

Definition at line 37 of file force_constraint.cc.

~ForceConstraint()

virtual towr::ForceConstraint::~ForceConstraint ( )

virtualdefault

Member Function Documentation

FillJacobianBlock()

void towr::ForceConstraint::FillJacobianBlock ( std::string  var_set, Jacobian &  jac  ) const

overridevirtual

Implements ifopt::ConstraintSet.

Definition at line 108 of file force_constraint.cc.

GetBounds()

ForceConstraint::VecBound towr::ForceConstraint::GetBounds ( ) const

overridevirtual

Implements ifopt::Component.

Definition at line 92 of file force_constraint.cc.

GetValues()

Eigen::VectorXd towr::ForceConstraint::GetValues ( ) const

overridevirtual

Implements ifopt::Component.

Definition at line 63 of file force_constraint.cc.

InitVariableDependedQuantities()

void towr::ForceConstraint::InitVariableDependedQuantities ( const VariablesPtr &  x )

override

Definition at line 51 of file force_constraint.cc.

Member Data Documentation

ee_

EE towr::ForceConstraint::ee_

private

The endeffector force to be constrained.

Definition at line 85 of file force_constraint.h.

ee_force_

NodesVariablesPhaseBased::Ptr towr::ForceConstraint::ee_force_

private

the current xyz foot forces.

Definition at line 78 of file force_constraint.h.

ee_motion_

NodesVariablesPhaseBased::Ptr towr::ForceConstraint::ee_motion_

private

the current xyz foot positions.

Definition at line 79 of file force_constraint.h.

fn_max_

double towr::ForceConstraint::fn_max_

private

force limit in normal direction.

Definition at line 82 of file force_constraint.h.

mu_

double towr::ForceConstraint::mu_

private

friction coeff between robot feet and terrain.

Definition at line 83 of file force_constraint.h.

n_constraints_per_node_

int towr::ForceConstraint::n_constraints_per_node_

private

number of constraint for each node.

Definition at line 84 of file force_constraint.h.

pure_stance_force_node_ids_

std::vector<int> towr::ForceConstraint::pure_stance_force_node_ids_

private

The are those Hermite-nodes that shape the polynomial during the stance phases, while all the others are already set to zero force (swing)

Definition at line 91 of file force_constraint.h.

terrain_

HeightMap::Ptr towr::ForceConstraint::terrain_

private

gradient information at every position (x,y).

Definition at line 81 of file force_constraint.h.

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

• force_constraint.h
• force_constraint.cc