# Copyright (C) Istituto Italiano di Tecnologia (IIT). All rights reserved.
import warnings
import jax.numpy as jnp
import numpy as np
from adam.core.constants import Representations
from adam.core.rbd_algorithms import RBDAlgorithms
from adam.jax.jax_like import SpatialMath
from adam.model import Model, URDFModelFactory
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class KinDynComputations:
"""This is a small class that retrieves robot quantities using Jax for Floating Base systems."""
def __init__(
self,
urdfstring: str,
joints_name_list: list = None,
root_link: str = None,
gravity: np.array = jnp.array([0, 0, -9.80665, 0, 0, 0]),
) -> None:
"""
Args:
urdfstring (str): either path or string of the urdf
joints_name_list (list): list of the actuated joints
root_link (str, optional): Deprecated. The root link is automatically chosen as the link with no parent in the URDF. Defaults to None.
"""
math = SpatialMath()
factory = URDFModelFactory(path=urdfstring, math=math)
model = Model.build(factory=factory, joints_name_list=joints_name_list)
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self.rbdalgos = RBDAlgorithms(model=model, math=math)
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self.NDoF = self.rbdalgos.NDoF
if root_link is not None:
warnings.warn(
"The root_link argument is not used. The root link is automatically chosen as the link with no parent in the URDF",
DeprecationWarning,
stacklevel=2,
)
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def set_frame_velocity_representation(
self, representation: Representations
) -> None:
"""Sets the representation of the velocity of the frames
Args:
representation (Representations): The representation of the velocity
"""
self.rbdalgos.set_frame_velocity_representation(representation)
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def mass_matrix(self, base_transform: jnp.array, joint_positions: jnp.array):
"""Returns the Mass Matrix functions computed the CRBA
Args:
base_transform (jnp.array): The homogenous transform from base to world frame
joint_positions (jnp.array): The joints position
Returns:
M (jnp.array): Mass Matrix
"""
[M, _] = self.rbdalgos.crba(base_transform, joint_positions)
return M.array
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def centroidal_momentum_matrix(
self, base_transform: jnp.array, joint_positions: jnp.array
):
"""Returns the Centroidal Momentum Matrix functions computed the CRBA
Args:
base_transform (jnp.array): The homogenous transform from base to world frame
joint_positions (jnp.array): The joints position
Returns:
Jcc (jnp.array): Centroidal Momentum matrix
"""
[_, Jcm] = self.rbdalgos.crba(base_transform, joint_positions)
return Jcm.array
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def relative_jacobian(self, frame: str, joint_positions: jnp.array):
"""Returns the Jacobian between the root link and a specified frame frames
Args:
frame (str): The tip of the chain
joint_positions (jnp.array): The joints position
Returns:
J (jnp.array): The Jacobian between the root and the frame
"""
return self.rbdalgos.relative_jacobian(frame, joint_positions).array
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def jacobian_dot(
self,
frame: str,
base_transform: jnp.array,
joint_positions: jnp.array,
base_velocity: jnp.array,
joint_velocities: jnp.array,
) -> jnp.array:
"""Returns the Jacobian derivative relative to the specified frame
Args:
frame (str): The frame to which the jacobian will be computed
base_transform (jnp.array): The homogenous transform from base to world frame
joint_positions (jnp.array): The joints position
base_velocity (jnp.array): The base velocity
joint_velocities (jnp.array): The joint velocities
Returns:
Jdot (jnp.array): The Jacobian derivative relative to the frame
"""
return self.rbdalgos.jacobian_dot(
frame, base_transform, joint_positions, base_velocity, joint_velocities
).array
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def forward_kinematics(
self, frame: str, base_transform: jnp.array, joint_positions: jnp.array
):
"""Computes the forward kinematics relative to the specified frame
Args:
frame (str): The frame to which the fk will be computed
base_transform (jnp.array): The homogenous transform from base to world frame
joint_positions (jnp.array): The joints position
Returns:
H (jnp.array): The fk represented as Homogenous transformation matrix
"""
return self.rbdalgos.forward_kinematics(
frame, base_transform, joint_positions
).array
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def jacobian(
self, frame: str, base_transform: jnp.array, joint_positions: jnp.array
):
"""Returns the Jacobian relative to the specified frame
Args:
base_transform (jnp.array): The homogenous transform from base to world frame
s (jnp.array): The joints position
frame (str): The frame to which the jacobian will be computed
Returns:
J_tot (jnp.array): The Jacobian relative to the frame
"""
return self.rbdalgos.jacobian(frame, base_transform, joint_positions).array
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def bias_force(
self,
base_transform: jnp.array,
joint_positions: jnp.array,
base_velocity: jnp.array,
joint_velocities: jnp.array,
) -> jnp.array:
"""Returns the bias force of the floating-base dynamics equation,
using a reduced RNEA (no acceleration and external forces)
Args:
base_transform (jnp.array): The homogenous transform from base to world frame
joint_positions (jnp.array): The joints position
base_velocity (jnp.array): The base velocity
joint_velocities (jnp.array): The joints velocity
Returns:
h (jnp.array): the bias force
"""
return self.rbdalgos.rnea(
base_transform, joint_positions, base_velocity, joint_velocities, self.g
).array.squeeze()
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def coriolis_term(
self,
base_transform: jnp.array,
joint_positions: jnp.array,
base_velocity: jnp.array,
joint_velocities: jnp.array,
) -> jnp.array:
"""Returns the coriolis term of the floating-base dynamics equation,
using a reduced RNEA (no acceleration and external forces)
Args:
base_transform (jnp.array): The homogenous transform from base to world frame
joint_positions (jnp.array): The joints position
base_velocity (jnp.array): The base velocity
joint_velocities (jnp.array): The joints velocity
Returns:
C (jnp.array): the Coriolis term
"""
return self.rbdalgos.rnea(
base_transform,
joint_positions,
base_velocity.reshape(6, 1),
joint_velocities,
np.zeros(6),
).array.squeeze()
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def gravity_term(
self, base_transform: jnp.array, joint_positions: jnp.array
) -> jnp.array:
"""Returns the gravity term of the floating-base dynamics equation,
using a reduced RNEA (no acceleration and external forces)
Args:
base_transform (jnp.array): The homogenous transform from base to world frame
joint_positions (jnp.array): The joints position
Returns:
G (jnp.array): the gravity term
"""
return self.rbdalgos.rnea(
base_transform,
joint_positions,
np.zeros(6).reshape(6, 1),
np.zeros(self.NDoF),
self.g,
).array.squeeze()
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def CoM_position(
self, base_transform: jnp.array, joint_positions: jnp.array
) -> jnp.array:
"""Returns the CoM position
Args:
base_transform (jnp.array): The homogenous transform from base to world frame
joint_positions (jnp.array): The joints position
Returns:
CoM (jnp.array): The CoM position
"""
return self.rbdalgos.CoM_position(
base_transform, joint_positions
).array.squeeze()
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def CoM_jacobian(
self, base_transform: jnp.array, joint_positions: jnp.array
) -> jnp.array:
"""Returns the CoM Jacobian
Args:
base_transform (jnp.array): The homogenous transform from base to world frame
joint_positions (jnp.array): The joints position
Returns:
Jcom (jnp.array): The CoM Jacobian
"""
return self.rbdalgos.CoM_jacobian(
base_transform, joint_positions
).array.squeeze()
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def get_total_mass(self) -> float:
"""Returns the total mass of the robot
Returns:
mass: The total mass
"""
return self.rbdalgos.get_total_mass()