Dynamics model relating forces to base accelerations. More...

#include <single_rigid_body_dynamics.h>

Inheritance diagram for towr::SingleRigidBodyDynamics:

[legend]

Public Member Functions
BaseAcc	GetDynamicViolation () const override
	The violation of the system dynamics incurred by the current values. More...

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

Jac	GetJacobianWrtBaseLin (const Jac &jac_base_lin_pos, const Jac &jac_acc_base_lin) const override
	How the base position affects the dynamic violation. More...

Jac	GetJacobianWrtEEPos (const Jac &jac_ee_pos, EE) const override
	How the endeffector positions affect the dynamic violation. More...

Jac	GetJacobianWrtForce (const Jac &jac_force, EE) const override
	How the endeffector forces affect the dynamic violation. More...

	SingleRigidBodyDynamics (double mass, const Eigen::Matrix3d &inertia_b, int ee_count)
	Constructs a specific model. More...

	SingleRigidBodyDynamics (double mass, double Ixx, double Iyy, double Izz, double Ixy, double Ixz, double Iyz, int ee_count)
	Constructs a specific model. More...

virtual	~SingleRigidBodyDynamics ()=default

Public Member Functions inherited from towr::DynamicModel
double	g () const

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

Private Attributes
Eigen::SparseMatrix< double, Eigen::RowMajor >	I_b

Additional Inherited Members
Public Types inherited from towr::DynamicModel
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

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

virtual	~DynamicModel ()=default

Protected Attributes inherited from towr::DynamicModel
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...

Detailed Description

Dynamics model relating forces to base accelerations.

This class implements a Single Rigid Body dynamics model, a reduced dimensional model, lying in terms of accuracy between a Linear Inverted Pendulum model and a full Centroidal or Rigid-body-dynamics model.

This model makes the assumption that the motion of the limbs does not incur significant momentum and can therefore be neglected. This eliminates the nonlinear dependency on joint angles and allows to express all quantities in Cartesian space.

For the derivation and all assumptions of this model, see: https://doi.org/10.3929/ethz-b-000272432

See also: https://en.wikipedia.org/wiki/Newton%E2%80%93Euler_equations

Definition at line 56 of file single_rigid_body_dynamics.h.

Constructor & Destructor Documentation

towr::SingleRigidBodyDynamics::SingleRigidBodyDynamics	(	double	mass,
		const Eigen::Matrix3d &	inertia_b,
		int	ee_count
	)

Constructs a specific model.

Parameters

mass	The mass of the robot.
ee_count	The number of endeffectors/forces.
inertia_b	The elements of the 3x3 Inertia matrix around the CoM. This matrix maps angular accelerations expressed in base frame to moments in base frame.

Definition at line 69 of file single_rigid_body_dynamics.cc.

towr::SingleRigidBodyDynamics::SingleRigidBodyDynamics	(	double	mass,
		double	Ixx,
		double	Iyy,
		double	Izz,
		double	Ixy,
		double	Ixz,
		double	Iyz,
		int	ee_count
	)

Constructs a specific model.

Parameters

mass	Mass of the robot.
I..	Elements of the 3x3 Inertia matrix
ee_count	Number of endeffectors/forces.

Definition at line 59 of file single_rigid_body_dynamics.cc.

virtual towr::SingleRigidBodyDynamics::~SingleRigidBodyDynamics ( )

virtualdefault

Member Function Documentation

SingleRigidBodyDynamics::BaseAcc towr::SingleRigidBodyDynamics::GetDynamicViolation ( ) const

overridevirtual

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

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

Implements towr::DynamicModel.

Definition at line 77 of file single_rigid_body_dynamics.cc.

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

overridevirtual

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).

Implements towr::DynamicModel.

Definition at line 124 of file single_rigid_body_dynamics.cc.

SingleRigidBodyDynamics::Jac towr::SingleRigidBodyDynamics::GetJacobianWrtBaseLin	(	const Jac &	jac_base_lin_pos,
		const Jac &	jac_base_lin_acc
	)		const

overridevirtual

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).

Implements towr::DynamicModel.

Definition at line 104 of file single_rigid_body_dynamics.cc.

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

overridevirtual

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).

Implements towr::DynamicModel.

Definition at line 182 of file single_rigid_body_dynamics.cc.

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

overridevirtual

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).

Implements towr::DynamicModel.

Definition at line 168 of file single_rigid_body_dynamics.cc.

Member Data Documentation

Eigen::SparseMatrix<double, Eigen::RowMajor> towr::SingleRigidBodyDynamics::I_b

private

Inertia of entire robot around the CoM expressed in a frame anchored in the base.

Definition at line 95 of file single_rigid_body_dynamics.h.

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

Public Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation