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

#include <dynamic_model.h>

Inheritance diagram for towr::DynamicModel:

Public Member Functions
double	g () const
virtual BaseAcc	GetDynamicViolation () const =0
	The violation of the system dynamics incurred by the current values.
int	GetEECount () const
	the number of endeffectors that this robot has.
virtual Jac	GetJacobianWrtBaseAng (const EulerConverter &base_angular, double t) const =0
	How the base orientation affects the dynamic violation.
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.
virtual Jac	GetJacobianWrtEEPos (const Jac &ee_pos, EE ee) const =0
	How the endeffector positions affect the dynamic violation.
virtual Jac	GetJacobianWrtForce (const Jac &ee_force, EE ee) const =0
	How the endeffector forces affect the dynamic violation.
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.
Protected Member Functions
	DynamicModel (double mass, int ee_count)
	Construct a dynamic object. Protected as this is abstract base class.
virtual	~DynamicModel ()
Protected Attributes
Vector3d	com_acc_
	x-y-z acceleration of the Center-of-Mass.
ComPos	com_pos_
	x-y-z position of the Center-of-Mass.
EELoad	ee_force_
	The endeffector force expressed in world frame.
EEPos	ee_pos_
	The x-y-z position of each endeffector.
AngVel	omega_
	angular velocity expressed in world frame.
Vector3d	omega_dot_
	angular acceleration expressed in world frame.
Matrix3d	w_R_b_
	rotation matrix from base (b) to world (w) frame.
Private Attributes
double	g_
	gravity acceleration [m/s^2]
double	m_
	mass of the robot

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)).

This model is used in DynamicConstraint to ensure that the optimized motion trajectory complies to this.

Currently, only CentroidalModel is implemented, but this can be extended in the future to also incorporate full rigid body dynamics. This interface to the solver should remain the same.

Definition at line 58 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 ( ) [protected, virtual]

Member Function Documentation

double towr::DynamicModel::g ( ) const [inline]

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

Definition at line 136 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::CentroidalModel.

int towr::DynamicModel::GetEECount ( ) const [inline]

the number of endeffectors that this robot has.

Definition at line 146 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::CentroidalModel.

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::CentroidalModel.

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::CentroidalModel.

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::CentroidalModel.

double towr::DynamicModel::m ( ) const [inline]

Returns:: The mass of the robot [kg].

Definition at line 141 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