A interface for the the system dynamics of a legged robot. More...

#include <dynamic_model.h>

Inheritance diagram for towr::DynamicModel:

[legend]

Public Types
using	AngVel = Eigen::Vector3d

using	BaseAcc = Eigen::Matrix< double, 6, 1 >

using	ComPos = Eigen::Vector3d

using	EE = uint

using	EELoad = EEPos

using	EEPos = std::vector< Eigen::Vector3d >

using	Jac = Eigen::SparseMatrix< double, Eigen::RowMajor >

using	Matrix3d = Eigen::Matrix3d

using	Ptr = std::shared_ptr< DynamicModel >

using	Vector3d = Eigen::Vector3d

Public Member Functions
double	g () const

virtual BaseAcc	GetDynamicViolation () const =0
	The violation of the system dynamics incurred by the current values. More...

int	GetEECount () const
	the number of endeffectors that this robot has. More...

virtual Jac	GetJacobianWrtBaseAng (const EulerConverter &base_angular, double t) const =0
	How the base orientation affects the dynamic violation. More...

virtual Jac	GetJacobianWrtBaseLin (const Jac &jac_base_lin_pos, const Jac &jac_base_lin_acc) const =0
	How the base position affects the dynamic violation. More...

virtual Jac	GetJacobianWrtEEPos (const Jac &ee_pos, EE ee) const =0
	How the endeffector positions affect the dynamic violation. More...

virtual Jac	GetJacobianWrtForce (const Jac &ee_force, EE ee) const =0
	How the endeffector forces affect the dynamic violation. More...

double	m () const

void	SetCurrent (const ComPos &com_W, const Vector3d com_acc_W, const Matrix3d &w_R_b, const AngVel &omega_W, const Vector3d &omega_dot_W, const EELoad &force_W, const EEPos &pos_W)
	Sets the current state and input of the system. More...

Protected Member Functions
	DynamicModel (double mass, int ee_count)
	Construct a dynamic object. Protected as this is abstract base class. More...

virtual	~DynamicModel ()=default

Protected Attributes
Vector3d	com_acc_
	x-y-z acceleration of the Center-of-Mass. More...

ComPos	com_pos_
	x-y-z position of the Center-of-Mass. More...

EELoad	ee_force_
	The endeffector force expressed in world frame. More...

EEPos	ee_pos_
	The x-y-z position of each endeffector. More...

AngVel	omega_
	angular velocity expressed in world frame. More...

Vector3d	omega_dot_
	angular acceleration expressed in world frame. More...

Matrix3d	w_R_b_
	rotation matrix from base (b) to world (w) frame. More...

Private Attributes
double	g_
	gravity acceleration [m/s^2] More...

double	m_
	mass of the robot More...

Detailed Description

A interface for the the system dynamics of a legged robot.

This class is responsible for verifying that the current acceleration of a system given a specific robot state and input forces ensure the system dynamics, so g = xdd(t) - f(x(t), f(t)).

Dynamic models can for example be: Linear Inverted Pendulum (LIP), SingleRigidBodyDynamics (SRBD), Centroidal Dynamics, Full Rigid Body Dynamics (RBD).

An overview of all these models can be found here: https://doi.org/10.3929/ethz-b-000272432

This model is used in DynamicConstraint to ensure that the optimized motion trajectory complies to this. Currently, only SingleRigidBodyDynamics is implemented.

Definition at line 66 of file dynamic_model.h.

Member Typedef Documentation

using towr::DynamicModel::AngVel = Eigen::Vector3d

Definition at line 72 of file dynamic_model.h.

using towr::DynamicModel::BaseAcc = Eigen::Matrix<double,6,1>

Definition at line 73 of file dynamic_model.h.

using towr::DynamicModel::ComPos = Eigen::Vector3d

Definition at line 71 of file dynamic_model.h.

using towr::DynamicModel::EE = uint

Definition at line 77 of file dynamic_model.h.

using towr::DynamicModel::EELoad = EEPos

Definition at line 76 of file dynamic_model.h.

using towr::DynamicModel::EEPos = std::vector<Eigen::Vector3d>

Definition at line 75 of file dynamic_model.h.

using towr::DynamicModel::Jac = Eigen::SparseMatrix<double, Eigen::RowMajor>

Definition at line 74 of file dynamic_model.h.

using towr::DynamicModel::Matrix3d = Eigen::Matrix3d

Definition at line 70 of file dynamic_model.h.

using towr::DynamicModel::Ptr = std::shared_ptr<DynamicModel>

Definition at line 68 of file dynamic_model.h.

using towr::DynamicModel::Vector3d = Eigen::Vector3d

Definition at line 69 of file dynamic_model.h.

Constructor & Destructor Documentation

towr::DynamicModel::DynamicModel	(	double	mass,
		int	ee_count
	)

protected

Construct a dynamic object. Protected as this is abstract base class.

Parameters

mass	The mass of the system.

Definition at line 34 of file dynamic_model.cc.

virtual towr::DynamicModel::~DynamicModel ( )

protectedvirtualdefault

Member Function Documentation

double towr::DynamicModel::g ( ) const

inline

Returns: The gravity acceleration [m/s^2] (positive)

Definition at line 144 of file dynamic_model.h.

virtual BaseAcc towr::DynamicModel::GetDynamicViolation ( ) const

pure virtual

The violation of the system dynamics incurred by the current values.

Returns: The 6-dimension generalized force violation (angular + linear).

Implemented in towr::SingleRigidBodyDynamics.

int towr::DynamicModel::GetEECount ( ) const

inline

the number of endeffectors that this robot has.

Definition at line 154 of file dynamic_model.h.

virtual Jac towr::DynamicModel::GetJacobianWrtBaseAng	(	const EulerConverter &	base_angular,
		double	t
	)		const

pure virtual

How the base orientation affects the dynamic violation.

Parameters

base_angular	provides Euler angles Jacobians.
t	Time at which euler angles values are queried.

Returns: The 6xn Jacobian of dynamic violations with respect to variables defining the base angular spline (e.g. node values).

Implemented in towr::SingleRigidBodyDynamics.

virtual Jac towr::DynamicModel::GetJacobianWrtBaseLin	(	const Jac &	jac_base_lin_pos,
		const Jac &	jac_base_lin_acc
	)		const

pure virtual

How the base position affects the dynamic violation.

Parameters

jac_base_lin_pos	The 3xn Jacobian of the base linear position.
jac_base_lin_acc	The 3xn Jacobian of the base linear acceleration.

Returns: The 6xn Jacobian of dynamic violations with respect to variables defining the base linear spline (e.g. node values).

Implemented in towr::SingleRigidBodyDynamics.

virtual Jac towr::DynamicModel::GetJacobianWrtEEPos	(	const Jac &	ee_pos,
		EE	ee
	)		const

pure virtual

How the endeffector positions affect the dynamic violation.

Parameters

ee_force	The 3xn Jacobian of the foot position x,y,z.
ee	The endeffector for which the senstivity is required.

Returns: The 6xn Jacobian of dynamic violations with respect to variables defining the foot positions (e.g. node values).

Implemented in towr::SingleRigidBodyDynamics.

virtual Jac towr::DynamicModel::GetJacobianWrtForce	(	const Jac &	ee_force,
		EE	ee
	)		const

pure virtual

How the endeffector forces affect the dynamic violation.

Parameters

ee_force	The 3xn Jacobian of the foot force x,y,z.
ee	The endeffector for which the senstivity is required.

Returns: The 6xn Jacobian of dynamic violations with respect to variables defining the endeffector forces (e.g. node values).

Implemented in towr::SingleRigidBodyDynamics.

double towr::DynamicModel::m ( ) const

inline

Returns: The mass of the robot [kg].

Definition at line 149 of file dynamic_model.h.

void towr::DynamicModel::SetCurrent	(	const ComPos &	com_W,
		const Vector3d	com_acc_W,
		const Matrix3d &	w_R_b,
		const AngVel &	omega_W,
		const Vector3d &	omega_dot_W,
		const EELoad &	force_W,
		const EEPos &	pos_W
	)

Sets the current state and input of the system.

Parameters

com_W	Current Center-of-Mass (x,y,z) position in world frame.
com_acc_W	Current Center-of-Mass (x,y,z) acceleration in world.
w_R_b	Current rotation from base to world frame.
omega_W	Current angular velocity in world frame.
omega_dot_W	Current angular acceleration in world frame.
force_W	Force at each foot expressed in world frame.
pos_W	Position of each foot expressed in world frame

Definition at line 51 of file dynamic_model.cc.

Member Data Documentation

Vector3d towr::DynamicModel::com_acc_

protected

x-y-z acceleration of the Center-of-Mass.

Definition at line 158 of file dynamic_model.h.

ComPos towr::DynamicModel::com_pos_

protected

x-y-z position of the Center-of-Mass.

Definition at line 154 of file dynamic_model.h.

EELoad towr::DynamicModel::ee_force_

protected

The endeffector force expressed in world frame.

Definition at line 165 of file dynamic_model.h.

EEPos towr::DynamicModel::ee_pos_

protected

The x-y-z position of each endeffector.

Definition at line 164 of file dynamic_model.h.

double towr::DynamicModel::g_

private

gravity acceleration [m/s^2]

Definition at line 175 of file dynamic_model.h.

double towr::DynamicModel::m_

private

mass of the robot

Definition at line 176 of file dynamic_model.h.

AngVel towr::DynamicModel::omega_

protected

angular velocity expressed in world frame.

Definition at line 161 of file dynamic_model.h.

Vector3d towr::DynamicModel::omega_dot_

protected

angular acceleration expressed in world frame.

Definition at line 162 of file dynamic_model.h.

Matrix3d towr::DynamicModel::w_R_b_

protected

rotation matrix from base (b) to world (w) frame.

Definition at line 160 of file dynamic_model.h.

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

Public Types

Public Member Functions

Protected Member Functions

Protected Attributes

Private Attributes

Detailed Description

Member Typedef Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation