Position and velocity of nodes used to generate a Hermite spline. More...

#include <nodes_variables.h>

Inheritance diagram for towr::NodesVariables:

Classes
struct	NodeValueInfo
	Semantic information associated with a scalar node value. More...
Public Types
enum	Side { Start = 0, End }
Public Member Functions
void	AddFinalBound (Dx deriv, const std::vector< int > &dimensions, const VectorXd &val)
	Restricts the last node in the spline.
void	AddObserver (ObserverPtr const spline)
	Adds a dependent observer that gets notified when the nodes change.
void	AddStartBound (Dx deriv, const std::vector< int > &dimensions, const VectorXd &val)
	Restricts the first node in the spline.
const std::vector< Node >	GetBoundaryNodes (int poly_id) const
VecBound	GetBounds () const override
int	GetDim () const
const std::vector< Node >	GetNodes () const
virtual std::vector < NodeValueInfo >	GetNodeValuesInfo (int opt_idx) const =0
	Node values affected by one specific optimization variable.
int	GetOptIndex (const NodeValueInfo &nvi) const
	Index in the optimization vector for a specific nodes' pos/vel.
int	GetPolynomialCount () const
VectorXd	GetValues () const override
	Pure optimization variables that define the nodes.
void	SetByLinearInterpolation (const VectorXd &initial_val, const VectorXd &final_val, double t_total)
	Sets nodes pos/vel equally spaced from initial to final position.
void	SetVariables (const VectorXd &x) override
	Sets some node positions and velocity from the optimization variables.
Static Public Member Functions
static int	GetNodeId (int poly_id, Side side)
	The node ID that belongs to a specific side of a specific polynomial.
Static Public Attributes
static const int	NodeValueNotOptimized = -1
Protected Member Functions
	NodesVariables (const std::string &variable_name)
virtual	~NodesVariables ()
Protected Attributes
VecBound	bounds_
	the bounds on the node values.
int	n_dim_
std::vector< Node >	nodes_
Private Member Functions
void	AddBound (const NodeValueInfo &node_info, double value)
	Restricts a specific optimization variables.
void	AddBounds (int node_id, Dx deriv, const std::vector< int > &dim, const VectorXd &values)
	Bounds a specific node variables.
void	UpdateObservers () const
	Notifies the subscribed observers that the node values changes.
Private Attributes
std::vector< ObserverPtr >	observers_

Detailed Description

Position and velocity of nodes used to generate a Hermite spline.

#### Four nodes defining a single spline (e.g. foot position in x-direction)

Instead of setting the polynomial coefficients directly, a third-order polynomial is also fully defined by the value and first-derivative of the start and end of the polynomial as well as the duration. This class holds these node values composed of position and velocity.

In the above image the nodes are defined by the scalar position and velocity values x0, x0d, ..., xT, xTd. By optimizing over these nodes, different spline shapes are generated. It is important to note that **not all node values must be optimized over**. We can fix specific node values in advance, or _one_ optimization variables can represent _multiple_ nodes values in the spline. This is exploited in the subclass NodesVariablesPhaseBased using _Phase-based End-effector Parameterization_.

Definition at line 71 of file nodes_variables.h.

Member Enumeration Documentation

enum towr::NodesVariables::Side

Enumerator:

Start
End

Definition at line 159 of file nodes_variables.h.

Constructor & Destructor Documentation

towr::NodesVariables::NodesVariables ( const std::string & variable_name ) [protected]

Parameters:

n_dim	The number of dimensions (x,y,..) each node has.
variable_name	The name of the variables in the optimization problem.

Definition at line 35 of file nodes_variables.cc.

virtual towr::NodesVariables::~NodesVariables ( ) [protected, virtual]

Member Function Documentation

void towr::NodesVariables::AddBound	(	const NodeValueInfo &	node_info,
		double	value
	)		`[private]`

Restricts a specific optimization variables.

Parameters:

node_info	The specs of the optimization variables to restrict.
value	The value to set the bounds to.

Definition at line 162 of file nodes_variables.cc.

void towr::NodesVariables::AddBounds	(	int	node_id,
		Dx	deriv,
		const std::vector< int > &	dim,
		const VectorXd &	values
	)		`[private]`

Bounds a specific node variables.

Parameters:

node_id	The ID of the node to bound.
deriv	The derivative of the node to set.
dim	The dimension of the node to bound.
values	The values to set the bounds to.

Definition at line 153 of file nodes_variables.cc.

void towr::NodesVariables::AddFinalBound	(	Dx	deriv,
		const std::vector< int > &	dimensions,
		const VectorXd &	val
	)

Restricts the last node in the spline.

Parameters:

deriv	Which derivative (pos,vel,...) should be restricted.
dimensions	Which dimensions (x,y,z) should be restricted.
val	The values the last node should be set to.

Definition at line 177 of file nodes_variables.cc.

void towr::NodesVariables::AddObserver ( ObserverPtr const spline )

Adds a dependent observer that gets notified when the nodes change.

Parameters:

spline Usually a pointer to a spline which uses the node values.

Definition at line 82 of file nodes_variables.cc.

void towr::NodesVariables::AddStartBound	(	Dx	deriv,
		const std::vector< int > &	dimensions,
		const VectorXd &	val
	)

Restricts the first node in the spline.

Parameters:

deriv	Which derivative (pos,vel,...) should be restricted.
dimensions	Which dimensions (x,y,z) should be restricted.
val	The values the fist node should be set to.

Definition at line 171 of file nodes_variables.cc.

const std::vector< Node > towr::NodesVariables::GetBoundaryNodes ( int poly_id ) const

Returns:: the two nodes that make up polynomial with "poly_id".

Definition at line 94 of file nodes_variables.cc.

NodesVariables::VecBound towr::NodesVariables::GetBounds ( ) const [override]

Returns:: the bounds on position and velocity of each node and dimension.

Definition at line 115 of file nodes_variables.cc.

int towr::NodesVariables::GetDim ( ) const

Returns:: The dimensions (x,y,z) of every node.

Definition at line 103 of file nodes_variables.cc.

int towr::NodesVariables::GetNodeId	(	int	poly_id,
		Side	side
	)		`[static]`

The node ID that belongs to a specific side of a specific polynomial.

Parameters:

poly_id	The ID of the polynomial within the spline.
side	The side from which the node ID is required.

Definition at line 88 of file nodes_variables.cc.

const std::vector< Node > towr::NodesVariables::GetNodes ( ) const

Returns:: All the nodes that can be used to reconstruct the spline.

Definition at line 121 of file nodes_variables.cc.

virtual std::vector<NodeValueInfo> towr::NodesVariables::GetNodeValuesInfo ( int opt_idx ) const [pure virtual]

Node values affected by one specific optimization variable.

Parameters:

opt_idx The index (=row) of the optimization variable.

Returns:: All node values affected by this optimization variable.

This function determines which node values are optimized over, and which nodes values are set by the same optimization variable.

Reverse of GetOptIndex().

Implemented in towr::NodesVariablesPhaseBased, and towr::NodesVariablesAll.

int towr::NodesVariables::GetOptIndex ( const NodeValueInfo & nvi ) const

Index in the optimization vector for a specific nodes' pos/vel.

Parameters:

nvi	Description of node value we want to know the index for.

Returns:: The position of this node value in the optimization variables.

Reverse of GetNodeInfoAtOptIndex().

Definition at line 41 of file nodes_variables.cc.

int towr::NodesVariables::GetPolynomialCount ( ) const

Returns:: the number of polynomials that can be built with these nodes.

Definition at line 109 of file nodes_variables.cc.

Eigen::VectorXd towr::NodesVariables::GetValues ( ) const [override]

Pure optimization variables that define the nodes.

Not all node position and velocities are independent or optimized over, so usually the number of optimization variables is less than all nodes' pos/vel.

See also:: GetNodeInfoAtOptIndex()

Definition at line 53 of file nodes_variables.cc.

void towr::NodesVariables::SetByLinearInterpolation	(	const VectorXd &	initial_val,
		const VectorXd &	final_val,
		double	t_total
	)

Sets nodes pos/vel equally spaced from initial to final position.

Parameters:

initial_val	value of the first node.
final_val	value of the final node.
t_total	The total duration to reach final node (to set velocities).

Definition at line 127 of file nodes_variables.cc.

void towr::NodesVariables::SetVariables ( const VectorXd & x ) [override]

Sets some node positions and velocity from the optimization variables.

Parameters:

x	The optimization variables.

Not all node position and velocities are independent or optimized over, so usually the number of optimization variables is less than all nodes pos/vel.