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plant_test.py
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plant_test.py
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# -*- coding: utf-8 -*-
import collections
import copy
import itertools
import unittest
import numpy as np
from pydrake.autodiffutils import AutoDiffXd
from pydrake.symbolic import Expression, Variable
from pydrake.lcm import DrakeLcm
from pydrake.math import RigidTransform
from pydrake.multibody.tree import (
BallRpyJoint_,
Body_,
BodyIndex,
DoorHinge_,
DoorHingeConfig,
FixedOffsetFrame_,
ForceElement_,
ForceElementIndex,
Frame_,
FrameIndex,
JacobianWrtVariable,
Joint_,
JointActuator_,
JointActuatorIndex,
JointIndex,
LinearBushingRollPitchYaw_,
LinearSpringDamper_,
ModelInstanceIndex,
MultibodyForces_,
PlanarJoint_,
PrismaticJoint_,
RevoluteJoint_,
RevoluteSpring_,
RotationalInertia_,
RigidBody_,
SpatialInertia_,
UniformGravityFieldElement_,
UnitInertia_,
UniversalJoint_,
WeldJoint_,
world_index,
world_model_instance,
default_model_instance
)
from pydrake.multibody.math import (
SpatialForce_,
SpatialMomentum_,
SpatialVelocity_,
SpatialAcceleration_,
)
from pydrake.multibody.plant import (
AddMultibodyPlant,
AddMultibodyPlantSceneGraph,
CalcContactFrictionFromSurfaceProperties,
ConnectContactResultsToDrakeVisualizer,
ContactModel,
ContactResults_,
ContactResultsToLcmSystem,
CoulombFriction_,
ExternallyAppliedSpatialForce_,
MultibodyPlant,
MultibodyPlant_,
MultibodyPlantConfig,
PointPairContactInfo_,
PropellerInfo,
Propeller_,
Wing,
)
from pydrake.multibody.parsing import Parser
from pydrake.multibody.benchmarks.acrobot import (
AcrobotParameters,
MakeAcrobotPlant,
)
from pydrake.common.cpp_param import List
from pydrake.common import FindResourceOrThrow
from pydrake.common.deprecation import install_numpy_warning_filters
from pydrake.common.test_utilities import numpy_compare
from pydrake.common.test_utilities.deprecation import catch_drake_warnings
from pydrake.common.test_utilities.pickle_compare import assert_pickle
from pydrake.common.value import AbstractValue, Value
from pydrake.geometry import (
Box,
GeometryId,
GeometrySet,
HydroelasticContactRepresentation,
Meshcat,
Role,
PenetrationAsPointPair_,
ProximityProperties,
SignedDistancePair_,
SignedDistanceToPoint_,
Sphere,
)
from pydrake.math import (
RigidTransform_,
RollPitchYaw_,
RotationMatrix_,
)
from pydrake.systems.analysis import Simulator_
from pydrake.systems.framework import (
DiagramBuilder,
DiagramBuilder_,
System_,
LeafSystem_,
InputPort_,
OutputPort_,
)
from pydrake.systems.scalar_conversion import TemplateSystem
from pydrake.systems.lcm import LcmPublisherSystem
def get_index_class(cls, T):
# Maps a class to its corresponding index class, accommdating inheritance.
class_to_index_class_map = {
Body_[T]: BodyIndex,
ForceElement_[T]: ForceElementIndex,
Frame_[T]: FrameIndex,
Joint_[T]: JointIndex,
JointActuator_[T]: JointActuatorIndex,
}
for key_cls, index_cls in class_to_index_class_map.items():
if issubclass(cls, key_cls):
return index_cls
raise RuntimeError("Unknown class: {}".format(cls))
# Permits parametric scalar type conversion.
def to_type(system, T):
assert isinstance(system, System_[float])
if T == float:
return system
else:
return system.ToScalarType[T]()
class TestPlant(unittest.TestCase):
def setUp(self):
unittest.TestCase.setUp(self)
# For some reason, something in how `unittest` tries to scope warnings
# causes the previous filters to be lost. Re-install here.
# TODO(eric.cousineau): This used to be necessary for PY3-only, but
# with NumPy 1.16, it became PY2 too. Figure out why.
install_numpy_warning_filters(force=True)
def test_type_safe_indices(self):
self.assertEqual(world_index(), BodyIndex(0))
self.assertEqual(repr(world_index()), "BodyIndex(0)")
self.assertEqual(world_model_instance(), ModelInstanceIndex(0))
self.assertEqual(repr(world_model_instance()), "ModelInstanceIndex(0)")
self.assertEqual(default_model_instance(), ModelInstanceIndex(1))
self.assertTrue(ModelInstanceIndex(0) < ModelInstanceIndex(1))
def assert_sane(self, x, nonzero=True):
self.assertTrue(np.all(np.isfinite(numpy_compare.to_float(x))))
if nonzero:
numpy_compare.assert_float_not_equal(x, 0.)
@numpy_compare.check_all_types
def test_multibody_plant_construction_api(self, T):
# SceneGraph does not support `Expression` type.
DiagramBuilder = DiagramBuilder_[T]
SpatialInertia = SpatialInertia_[float]
RigidTransform = RigidTransform_[T]
CoulombFriction = CoulombFriction_[T]
builder = DiagramBuilder()
plant, scene_graph = AddMultibodyPlantSceneGraph(builder, 0.0)
self.assertEqual(plant.time_step(), 0.0)
spatial_inertia = SpatialInertia()
body = plant.AddRigidBody(name="new_body",
M_BBo_B=spatial_inertia)
body_mass = body.default_mass()
body_com = body.default_com()
body_default_unit_inertia = body.default_unit_inertia()
body_default_rotational_inertial = body.default_rotational_inertia()
body_default_spatial_inertial = body.default_spatial_inertia()
new_model_instance = plant.AddModelInstance("new_model_instance")
body = plant.AddRigidBody(name="new_body_2",
M_BBo_B=spatial_inertia,
model_instance=new_model_instance)
box = Box(width=0.5, depth=1.0, height=2.0)
body_X_BG = RigidTransform()
body_friction = CoulombFriction(static_friction=0.6,
dynamic_friction=0.5)
self.assertEqual(numpy_compare.to_float(
body_friction.static_friction()), 0.6)
self.assertEqual(numpy_compare.to_float(
body_friction.dynamic_friction()), 0.5)
body_friction2 = CoulombFriction(static_friction=0.2,
dynamic_friction=0.1)
combined_friction = CalcContactFrictionFromSurfaceProperties(
body_friction, body_friction2)
if T == float:
plant.RegisterVisualGeometry(
body=body, X_BG=body_X_BG, shape=box, name="new_body_visual",
diffuse_color=[1., 0.64, 0.0, 0.5])
plant.RegisterCollisionGeometry(
body=body, X_BG=body_X_BG, shape=box,
name="new_body_collision", coulomb_friction=body_friction)
self.assertGreater(plant.num_collision_geometries(), 0)
body0_props = scene_graph.model_inspector().GetProximityProperties(
plant.GetCollisionGeometriesForBody(body)[0])
body0_friction = body0_props.GetProperty(
"material", "coulomb_friction")
self.assertEqual(body0_friction.static_friction(), 0.6)
self.assertEqual(body0_friction.dynamic_friction(), 0.5)
explicit_props = ProximityProperties()
explicit_props.AddProperty("material", "coulomb_friction",
CoulombFriction(1.1, 0.8))
plant.RegisterCollisionGeometry(
body=body, X_BG=body_X_BG, shape=box,
name="new_body_collision2", properties=explicit_props)
body1_props = scene_graph.model_inspector().GetProximityProperties(
plant.GetCollisionGeometriesForBody(body)[1])
body1_friction = body1_props.GetProperty(
"material", "coulomb_friction")
self.assertGreater(plant.num_collision_geometries(), 1)
self.assertEqual(body1_friction.static_friction(), 1.1)
self.assertEqual(body1_friction.dynamic_friction(), 0.8)
# Confirm that passing the diagram context into the plant (a common
# user error) throws a RuntimeError instead of crashing.
plant.Finalize()
diagram = builder.Build()
context = diagram.CreateDefaultContext()
with self.assertRaises(RuntimeError):
plant.EvalBodyPoseInWorld(context, body)
def test_multibody_plant_config(self):
MultibodyPlantConfig()
config = MultibodyPlantConfig(time_step=0.01)
self.assertEqual(config.time_step, 0.01)
copy.copy(config)
builder = DiagramBuilder_[float]()
plant, scene_graph = AddMultibodyPlant(config, builder)
self.assertIsNotNone(plant)
self.assertIsNotNone(scene_graph)
@numpy_compare.check_all_types
def test_multibody_plant_api_via_parsing(self, T):
MultibodyPlant = MultibodyPlant_[T]
Joint = Joint_[T]
Body = Body_[T]
Frame = Frame_[T]
JointActuator = JointActuator_[T]
InputPort = InputPort_[T]
OutputPort = OutputPort_[T]
def check_repr(element, expected):
if T == float:
self.assertEqual(repr(element), expected)
# TODO(eric.cousineau): Decouple this when construction can be done
# without parsing.
# This a subset of `multibody_plant_sdf_parser_test.cc`.
file_name = FindResourceOrThrow(
"drake/multibody/benchmarks/acrobot/acrobot.sdf")
# N.B. `Parser` only supports `MultibodyPlant_[float]`.
plant_f = MultibodyPlant_[float](time_step=0.01)
model_instance = Parser(plant_f).AddModelFromFile(file_name)
self.assertIsInstance(model_instance, ModelInstanceIndex)
check_repr(model_instance, "ModelInstanceIndex(2)")
plant_f.Finalize()
plant = to_type(plant_f, T)
benchmark = MakeAcrobotPlant(AcrobotParameters(), True)
self.assertEqual(plant.num_bodies(), benchmark.num_bodies())
self.assertEqual(plant.num_joints(), benchmark.num_joints())
self.assertEqual(plant.num_actuators(), benchmark.num_actuators())
self.assertEqual(
plant.num_model_instances(), benchmark.num_model_instances() + 1)
self.assertEqual(plant.num_positions(), benchmark.num_positions())
self.assertEqual(
plant.num_positions(model_instance=model_instance),
benchmark.num_positions())
self.assertEqual(
plant.num_velocities(), benchmark.num_velocities())
self.assertEqual(
plant.num_velocities(model_instance=model_instance),
benchmark.num_velocities())
self.assertEqual(
plant.num_multibody_states(), benchmark.num_multibody_states())
self.assertEqual(
plant.num_multibody_states(model_instance=model_instance),
benchmark.num_multibody_states())
self.assertEqual(
plant.num_actuated_dofs(), benchmark.num_actuated_dofs())
self.assertEqual(
plant.num_actuated_dofs(model_instance=model_instance),
benchmark.num_actuated_dofs())
self.assertTrue(plant.is_finalized())
self.assertTrue(plant.HasBodyNamed(name="Link1"))
self.assertTrue(plant.HasBodyNamed(
name="Link1", model_instance=model_instance))
self.assertTrue(plant.HasJointNamed(name="ShoulderJoint"))
self.assertTrue(plant.HasJointNamed(
name="ShoulderJoint", model_instance=model_instance))
shoulder = plant.GetJointByName(name="ShoulderJoint")
self._test_joint_api(T, shoulder)
check_repr(
shoulder,
"<RevoluteJoint_[float] name='ShoulderJoint' index=0 "
"model_instance=2>")
np.testing.assert_array_equal(
shoulder.position_lower_limits(), [-np.inf])
np.testing.assert_array_equal(
shoulder.position_upper_limits(), [np.inf])
self.assertIs(shoulder, plant.GetJointByName(
name="ShoulderJoint", model_instance=model_instance))
self._test_joint_actuator_api(
T, plant.GetJointActuatorByName(name="ElbowJoint"))
link1 = plant.GetBodyByName(name="Link1")
self._test_body_api(T, link1)
self.assertIs(
link1,
plant.GetBodyByName(name="Link1", model_instance=model_instance))
link1 = plant.GetRigidBodyByName(name="Link1")
self._test_body_api(T, link1)
self.assertIs(
link1,
plant.GetRigidBodyByName(
name="Link1", model_instance=model_instance))
self.assertEqual(len(plant.GetBodyIndices(model_instance)), 2)
check_repr(
link1,
"<RigidBody_[float] name='Link1' index=1 model_instance=2>")
self._test_frame_api(T, plant.GetFrameByName(name="Link1"))
link1_frame = plant.GetFrameByName(name="Link1")
check_repr(
link1_frame,
"<BodyFrame_[float] name='Link1' index=1 model_instance=2>")
self.assertIs(
link1_frame,
plant.GetFrameByName(name="Link1", model_instance=model_instance))
self.assertIs(link1.GetParentPlant(), plant)
self.assertTrue(plant.HasModelInstanceNamed(name="acrobot"))
self.assertEqual(
model_instance, plant.GetModelInstanceByName(name="acrobot"))
self.assertEqual(
plant.GetBodiesWeldedTo(plant.world_body()), [plant.world_body()])
self.assertIsInstance(
plant.get_actuation_input_port(), InputPort)
self.assertIsInstance(
plant.get_state_output_port(), OutputPort)
self.assertIsInstance(
plant.get_generalized_acceleration_output_port(), OutputPort)
self.assertIsInstance(
plant.get_reaction_forces_output_port(), OutputPort)
self.assertIsInstance(
plant.get_contact_results_output_port(), OutputPort)
self.assertIsInstance(plant.num_frames(), int)
self.assertIsInstance(plant.get_body(body_index=BodyIndex(0)), Body)
self.assertIs(shoulder, plant.get_joint(joint_index=JointIndex(0)))
self.assertIs(shoulder, plant.get_mutable_joint(
joint_index=JointIndex(0)))
self.assertEqual([JointIndex(0), JointIndex(1)],
plant.GetJointIndices(model_instance=model_instance))
joint_actuator = plant.get_joint_actuator(
actuator_index=JointActuatorIndex(0))
self.assertIsInstance(joint_actuator, JointActuator)
check_repr(
joint_actuator,
"<JointActuator_[float] name='ElbowJoint' index=0 "
"model_instance=2>")
self.assertIsInstance(
plant.get_frame(frame_index=FrameIndex(0)), Frame)
self.assertEqual("acrobot", plant.GetModelInstanceName(
model_instance=model_instance))
self.assertIn("acrobot", plant.GetTopologyGraphvizString())
def _test_multibody_tree_element_mixin(self, T, element):
cls = type(element)
self.assertIsInstance(element.index(), get_index_class(cls, T))
self.assertIsInstance(element.model_instance(), ModelInstanceIndex)
element.GetParentPlant()
def _test_frame_api(self, T, frame):
Frame = Frame_[T]
self.assertIsInstance(frame, Frame)
self._test_multibody_tree_element_mixin(T, frame)
self.assertIsInstance(frame.body(), Body_[T])
self.assertIsInstance(frame.is_world_frame(), bool)
self.assertIsInstance(frame.is_body_frame(), bool)
self.assertIsInstance(frame.name(), str)
self.assertIsInstance(
frame.GetFixedPoseInBodyFrame(),
RigidTransform_[T])
self.assertIsInstance(
frame.GetFixedRotationMatrixInBodyFrame(),
RotationMatrix_[T])
def _test_body_api(self, T, body):
Body = Body_[T]
self.assertIsInstance(body, Body)
self._test_multibody_tree_element_mixin(T, body)
self.assertIsInstance(body.name(), str)
self.assertIsInstance(body.get_num_flexible_positions(), int)
self.assertIsInstance(body.get_num_flexible_velocities(), int)
self.assertIsInstance(body.is_floating(), bool)
self.assertIsInstance(body.has_quaternion_dofs(), bool)
self.assertIsInstance(body.floating_positions_start(), int)
self.assertIsInstance(body.floating_velocities_start(), int)
self.assertIsInstance(body.default_mass(), float)
# TODO(2022-11-01) Remove with completion of deprecation.
with catch_drake_warnings(expected_count=1):
self.assertIsInstance(body.get_default_mass(), float)
@numpy_compare.check_all_types
def test_body_context_methods(self, T):
plant = MultibodyPlant_[T](0.0)
dut = plant.AddRigidBody(
name="name", M_BBo_B=SpatialInertia_[float](
mass=1.0, p_PScm_E=[0.0, 0.0, 0.0],
G_SP_E=UnitInertia_[float](Ixx=1.0, Iyy=1.0, Izz=1.0)))
plant.Finalize()
context = plant.CreateDefaultContext()
self.assertIsInstance(
dut.get_mass(context=context),
T)
self.assertIsInstance(
dut.CalcCenterOfMassInBodyFrame(context=context),
np.ndarray)
self.assertIsInstance(
dut.CalcSpatialInertiaInBodyFrame(context=context),
SpatialInertia_[T])
self.assertIsInstance(
dut.EvalPoseInWorld(context=context),
RigidTransform_[T])
self.assertIsInstance(
dut.EvalSpatialVelocityInWorld(context=context),
SpatialVelocity_[T])
self.assertIsInstance(
dut.EvalSpatialAccelerationInWorld(context=context),
SpatialAcceleration_[T])
# The test_multibody_dynamics already covers GetForceInWorld,
# AddInForce, AddInForceInWorld.
# Also test these body api methods which require a finalized plant.
for i in range(7):
self.assertIsNotNone(dut.floating_position_suffix(i))
for i in range(6):
self.assertIsNotNone(dut.floating_velocity_suffix(i))
def _test_joint_api(self, T, joint):
Joint = Joint_[T]
Body = Body_[T]
Frame = Frame_[T]
self.assertIsInstance(joint, Joint)
self._test_multibody_tree_element_mixin(T, joint)
self.assertIsInstance(joint.name(), str)
self.assertIsInstance(joint.type_name(), str)
self.assertIsInstance(joint.parent_body(), Body)
self.assertIsInstance(joint.child_body(), Body)
self.assertIsInstance(joint.frame_on_parent(), Frame)
self.assertIsInstance(joint.frame_on_child(), Frame)
self.assertIsInstance(joint.num_positions(), int)
self.assertIsInstance(joint.num_velocities(), int)
self.assertIsInstance(joint.position_start(), int)
self.assertIsInstance(joint.velocity_start(), int)
nq = joint.num_positions()
q_default = joint.default_positions()
self.assertEqual(len(q_default), nq)
joint.set_default_positions(default_positions=q_default)
q_lower = joint.position_lower_limits()
self.assertEqual(len(q_lower), nq)
q_upper = joint.position_upper_limits()
self.assertEqual(len(q_upper), nq)
joint.set_position_limits(lower_limits=q_lower, upper_limits=q_upper)
nv = joint.num_velocities()
v_lower = joint.velocity_lower_limits()
self.assertEqual(len(v_lower), nv)
v_upper = joint.velocity_upper_limits()
self.assertEqual(len(v_upper), nv)
joint.set_velocity_limits(lower_limits=v_lower, upper_limits=v_upper)
a_lower = joint.acceleration_lower_limits()
self.assertEqual(len(a_lower), nv)
a_upper = joint.acceleration_upper_limits()
self.assertEqual(len(a_upper), nv)
joint.set_acceleration_limits(
lower_limits=a_lower, upper_limits=a_upper)
def _test_joint_actuator_api(self, T, joint_actuator):
JointActuator = JointActuator_[T]
Joint = Joint_[T]
self.assertIsInstance(joint_actuator, JointActuator)
self._test_multibody_tree_element_mixin(T, joint_actuator)
self.assertIsInstance(joint_actuator.name(), str)
self.assertIsInstance(joint_actuator.joint(), Joint)
self.assertIsInstance(joint_actuator.effort_limit(), float)
self.assertGreaterEqual(joint_actuator.input_start(), 0)
self.assertEqual(joint_actuator.num_inputs(), 1)
def _test_rotational_inertia_or_unit_inertia_api(self, T, Class):
"""
Tests the given Class (either RotationInertia or UnitInertia) for the
API subset that they both share.
"""
RotationMatrix = RotationMatrix_[T]
Class()
Class(Ixx=1.0, Iyy=1.0, Izz=1.0, Ixy=0.1, Ixz=0.1, Iyz=0.1)
Class(Ixx=1.0, Iyy=1.0, Izz=1.0)
dut = Class.TriaxiallySymmetric(I_triaxial=1.0)
self.assertIsInstance(dut, Class)
dut.rows()
dut.cols()
self.assertIsInstance(dut.get_moments(), np.ndarray)
self.assertIsInstance(dut.get_products(), np.ndarray)
self.assertIsInstance(dut.Trace(), T)
dut.CalcMaximumPossibleMomentOfInertia()
self.assertIsInstance(dut[0, 0], T)
with self.assertRaisesRegex(
Exception, r"incompatible function arguments"):
dut[0]
with self.assertRaisesRegex(
Exception, r"Unable to cast"):
dut[0.0, 0.0]
with self.assertRaisesRegex(
Exception, r"Expected \[i,j\]"):
dut[0, 0, 0]
self.assertIsInstance(dut.CopyToFullMatrix3(), np.ndarray)
dut.IsNearlyEqualTo(other=dut, precision=0.0)
dut.SetToNaN()
dut.IsNaN()
dut.SetZero()
self.assertIsInstance(dut.CalcPrincipalMomentsOfInertia(), np.ndarray)
dut.CouldBePhysicallyValid()
self.assertIsInstance(dut.ReExpress(R_AE=RotationMatrix()), Class)
self.assertIsInstance(copy.copy(dut), Class)
@numpy_compare.check_all_types
def test_rotational_inertia_api(self, T):
"""Tests rotational inertia construction and API."""
Class = RotationalInertia_[T]
self._test_rotational_inertia_or_unit_inertia_api(T, Class)
# Test methods present only on RotationalInernia, not UnitInertia.
p = [0.1, 0.2, 0.3]
dut = Class(mass=1.0, p_PQ_E=p)
self.assertIsInstance(
dut.ShiftFromCenterOfMass(mass=1.0, p_BcmQ_E=p), Class)
self.assertIsInstance(
dut.ShiftToCenterOfMass(mass=1.0, p_QBcm_E=p), Class)
self.assertIsInstance(
dut.ShiftToThenAwayFromCenterOfMass(
mass=1.0, p_PBcm_E=p, p_QBcm_E=p),
Class)
# Test operators.
zero = Class(Ixx=0.0, Iyy=0.0, Izz=0.0)
self.assertIsInstance(dut + zero, Class)
self.assertIsInstance(dut - zero, Class)
self.assertIsInstance(dut * T(1.0), Class)
self.assertIsInstance(T(1.0) * dut, Class)
self.assertIsInstance(dut * p, np.ndarray)
self.assertIsInstance(dut / T(1.0), Class)
dut += zero
self.assertIsInstance(dut, Class)
dut -= zero
self.assertIsInstance(dut, Class)
dut *= T(1.0)
self.assertIsInstance(dut, Class)
dut /= T(1.0)
self.assertIsInstance(dut, Class)
assert_pickle(self, dut, RotationalInertia_[T].CopyToFullMatrix3, T=T)
@numpy_compare.check_all_types
def test_unit_inertia_api(self, T):
"""Tests unit inertia construction and API."""
UnitInertia = UnitInertia_[T]
self._test_rotational_inertia_or_unit_inertia_api(T, UnitInertia)
# Test methods present only on UnitInertia, not RotationalInernia.
p = [0.1, 0.2, 0.3]
dut = UnitInertia(I=RotationalInertia_[T](mass=1.0, p_PQ_E=p))
self.assertIsInstance(
dut.ShiftFromCenterOfMass(p_BcmQ_E=p), UnitInertia)
self.assertIsInstance(
dut.ShiftToCenterOfMass(p_QBcm_E=p), UnitInertia)
assert_pickle(self, dut, UnitInertia.CopyToFullMatrix3, T=T)
# N.B. There are NO valid operators on UnitInertia. They are inherited
# through implementation reuse, but they are broken (#6109).
@numpy_compare.check_all_types
def test_spatial_inertia_api(self, T):
RotationalInertia = RotationalInertia_[T]
UnitInertia = UnitInertia_[T]
SpatialInertia = SpatialInertia_[T]
RotationMatrix = RotationMatrix_[T]
SpatialAcceleration = SpatialAcceleration_[T]
SpatialForce = SpatialForce_[T]
SpatialVelocity = SpatialVelocity_[T]
SpatialMomentum = SpatialMomentum_[T]
SpatialInertia()
SpatialInertia.MakeFromCentralInertia(
mass=1.3, p_PScm_E=[0.1, -0.2, 0.3],
I_SScm_E=RotationalInertia(Ixx=2.0, Iyy=2.3, Izz=2.4))
spatial_inertia = SpatialInertia(
mass=2.5, p_PScm_E=[0.1, -0.2, 0.3],
G_SP_E=UnitInertia(Ixx=2.0, Iyy=2.3, Izz=2.4))
numpy_compare.assert_float_equal(spatial_inertia.get_mass(), 2.5)
copied_inertia = copy.deepcopy(spatial_inertia)
self.assertIsInstance(spatial_inertia.get_com(), np.ndarray)
self.assertIsInstance(spatial_inertia.CalcComMoment(), np.ndarray)
self.assertIsInstance(spatial_inertia.get_unit_inertia(), UnitInertia)
self.assertIsInstance(
spatial_inertia.CalcRotationalInertia(), RotationalInertia)
# N.B. `numpy_compare.assert_equal(IsPhysicallyValid(), True)` does not
# work.
if T != Expression:
self.assertTrue(spatial_inertia.IsPhysicallyValid())
self.assertIsInstance(spatial_inertia.CopyToFullMatrix6(), np.ndarray)
self.assertIsInstance(
spatial_inertia.ReExpress(R_AE=RotationMatrix()), SpatialInertia)
self.assertIsInstance(
spatial_inertia.Shift([1, 2, 3]), SpatialInertia)
spatial_inertia += spatial_inertia
self.assertIsInstance(
spatial_inertia * SpatialAcceleration(), SpatialForce)
self.assertIsInstance(
spatial_inertia * SpatialVelocity(), SpatialMomentum)
assert_pickle(
self, spatial_inertia, SpatialInertia.CopyToFullMatrix6, T=T)
spatial_inertia.SetNaN()
# N.B. `numpy_compare.assert_equal(IsNaN(), True)` does not work.
if T != Expression:
self.assertTrue(spatial_inertia.IsNaN())
@numpy_compare.check_all_types
def test_friction_api(self, T):
CoulombFriction = CoulombFriction_[T]
CoulombFriction()
CoulombFriction(static_friction=0.7, dynamic_friction=0.6)
copy.copy(CoulombFriction())
assert_pickle(
self, CoulombFriction,
lambda x: [x.static_friction, x.dynamic_friction], T=T
)
@numpy_compare.check_all_types
def test_rigid_body_api(self, T):
RigidBody = RigidBody_[T]
M = SpatialInertia_[float]()
i = ModelInstanceIndex(0)
RigidBody(M_BBo_B=M)
RigidBody(body_name="body_name", M_BBo_B=M)
RigidBody(body_name="body_name", model_instance=i, M_BBo_B=M)
@numpy_compare.check_all_types
def test_multibody_force_element(self, T):
MultibodyPlant = MultibodyPlant_[T]
LinearSpringDamper = LinearSpringDamper_[T]
RevoluteSpring = RevoluteSpring_[T]
DoorHinge = DoorHinge_[T]
LinearBushingRollPitchYaw = LinearBushingRollPitchYaw_[T]
SpatialInertia = SpatialInertia_[float]
UnitInertia = UnitInertia_[float]
SpatialForce = SpatialForce_[T]
plant = MultibodyPlant(0.0)
spatial_inertia = SpatialInertia(
mass=1,
p_PScm_E=[0, 0, 0],
G_SP_E=UnitInertia(1, 1, 1),
)
body_a = plant.AddRigidBody(name="body_a",
M_BBo_B=spatial_inertia)
body_b = plant.AddRigidBody(name="body_b",
M_BBo_B=spatial_inertia)
linear_spring_index = ForceElementIndex(plant.num_force_elements())
linear_spring = plant.AddForceElement(LinearSpringDamper(
bodyA=body_a, p_AP=[0., 0., 0.],
bodyB=body_b, p_BQ=[0., 0., 0.],
free_length=1., stiffness=2., damping=3.))
if T == float:
self.assertEqual(
repr(linear_spring),
"<LinearSpringDamper_[float] index=1 model_instance=1>")
revolute_joint = plant.AddJoint(RevoluteJoint_[T](
name="revolve_joint", frame_on_parent=body_a.body_frame(),
frame_on_child=body_b.body_frame(), axis=[0, 0, 1],
damping=0.))
revolute_spring = plant.AddForceElement(RevoluteSpring(
joint=revolute_joint, nominal_angle=0.1, stiffness=100.))
door_hinge_config = DoorHingeConfig()
door_hinge = plant.AddForceElement(DoorHinge(
joint=revolute_joint, config=door_hinge_config))
torque_stiffness = np.array([10.0, 11.0, 12.0])
torque_damping = np.array([1.0, 1.1, 1.2])
force_stiffness = np.array([20.0, 21.0, 22.0])
force_damping = np.array([2.0, 2.1, 2.2])
bushing = plant.AddForceElement(LinearBushingRollPitchYaw(
frameA=body_a.body_frame(),
frameC=body_b.body_frame(),
torque_stiffness_constants=torque_stiffness,
torque_damping_constants=torque_damping,
force_stiffness_constants=force_stiffness,
force_damping_constants=force_damping,
))
plant.Finalize()
context = plant.CreateDefaultContext()
# Test LinearSpringDamper accessors
self.assertEqual(linear_spring.bodyA(), body_a)
self.assertEqual(linear_spring.bodyB(), body_b)
np.testing.assert_array_equal(linear_spring.p_AP(), [0, 0, 0])
np.testing.assert_array_equal(linear_spring.p_BQ(), [0, 0, 0])
self.assertEqual(linear_spring.free_length(), 1.)
self.assertEqual(linear_spring.stiffness(), 2.)
self.assertEqual(linear_spring.damping(), 3.)
# Test RevoluteSpring accessors
self.assertEqual(revolute_spring.joint(), revolute_joint)
self.assertEqual(revolute_spring.nominal_angle(), 0.1)
self.assertEqual(revolute_spring.stiffness(), 100.)
# Test DoorHinge accessors
self.assertEqual(door_hinge.joint(), revolute_joint)
door_hinge_config_test = door_hinge.config()
# Only test two members since the rest would be the same
self.assertEqual(door_hinge_config_test.spring_zero_angle_rad,
door_hinge_config.spring_zero_angle_rad)
self.assertEqual(door_hinge_config_test.static_friction_torque,
door_hinge_config.static_friction_torque)
# Test DoorHinge torque calculation. Set the angle to be the half of
# the catch width so that there is only torsional spring torque which
# is easy to compute by hand.
if T == float:
self.assertEqual(door_hinge.CalcHingeFrictionalTorque(
angular_rate=0.0), 0.0)
self.assertEqual(door_hinge.CalcHingeSpringTorque(
angle=0.01), -2.265)
self.assertEqual(door_hinge.CalcHingeTorque(
angle=0.01, angular_rate=0.0), -2.265)
# Test LinearBushingRollPitchYaw accessors.
self.assertIs(bushing.link0(), body_a)
self.assertIs(bushing.link1(), body_b)
self.assertIs(bushing.frameA(), body_a.body_frame())
self.assertIs(bushing.frameC(), body_b.body_frame())
numpy_compare.assert_float_equal(
bushing.torque_stiffness_constants(), torque_stiffness)
numpy_compare.assert_float_equal(
bushing.torque_damping_constants(), torque_damping)
numpy_compare.assert_float_equal(
bushing.force_stiffness_constants(), force_stiffness)
numpy_compare.assert_float_equal(
bushing.force_damping_constants(), force_damping)
# Set to 2x the original value and ensure it was updated in the given
# context.
bushing.SetTorqueStiffnessConstants(
context=context, torque_stiffness=2 * torque_stiffness)
numpy_compare.assert_float_equal(
bushing.GetTorqueStiffnessConstants(context=context),
2 * torque_stiffness)
bushing.SetTorqueDampingConstants(
context=context, torque_damping=2 * torque_damping)
numpy_compare.assert_float_equal(
bushing.GetTorqueDampingConstants(context=context),
2 * torque_damping)
bushing.SetForceStiffnessConstants(
context=context, force_stiffness=2 * force_stiffness)
numpy_compare.assert_float_equal(
bushing.GetForceStiffnessConstants(context=context),
2 * force_stiffness)
bushing.SetForceDampingConstants(
context=context, force_damping=2 * force_damping)
numpy_compare.assert_float_equal(
bushing.GetForceDampingConstants(context=context),
2 * force_damping)
# Test get_force_element().
self.assertIs(
plant.get_force_element(force_element_index=linear_spring_index),
linear_spring)
@numpy_compare.check_all_types
def test_multibody_gravity_default(self, T):
MultibodyPlant = MultibodyPlant_[T]
UniformGravityFieldElement = UniformGravityFieldElement_[T]
plant = MultibodyPlant(0.0)
with self.assertRaises(RuntimeError) as cm:
plant.AddForceElement(UniformGravityFieldElement())
self.assertIsInstance(
UniformGravityFieldElement.kDefaultStrength,
float)
@numpy_compare.check_all_types
def test_multibody_tree_kinematics_continuous(self, T):
self.do_test_multibody_tree_kinematics(T, 0.0)
@numpy_compare.check_all_types
def test_multibody_tree_kinematics_discrete(self, T):
self.do_test_multibody_tree_kinematics(T, 0.001)
def do_test_multibody_tree_kinematics(self, T, time_step):
RigidTransform = RigidTransform_[T]
SpatialVelocity = SpatialVelocity_[T]
plant_f = MultibodyPlant_[float](time_step)
file_name = FindResourceOrThrow(
"drake/bindings/pydrake/multibody/test/double_pendulum.sdf")
# N.B. `Parser` only supports `MultibodyPlant_[float]`.
instance = Parser(plant_f).AddModelFromFile(file_name)
plant_f.Finalize()
plant = to_type(plant_f, T)
context = plant.CreateDefaultContext()
world_frame = plant.world_frame()
base = plant.GetBodyByName("base")
base_frame = plant.GetFrameByName("base")
X_WL = plant.CalcRelativeTransform(
context, frame_A=world_frame, frame_B=base_frame)
self.assertIsInstance(X_WL, RigidTransform)
free_bodies = plant.GetFloatingBaseBodies()
self.assertEqual(len(free_bodies), 1)
self.assertTrue(base.index() in free_bodies)
self.assertFalse(base.is_locked(context))
if time_step:
base.Lock(context)
self.assertTrue(base.is_locked(context))
base.Unlock(context)
self.assertFalse(base.is_locked(context))
p_AQi = plant.CalcPointsPositions(
context=context, frame_B=base_frame,
p_BQi=np.array([[0, 1, 2], [10, 11, 12]]).T,
frame_A=world_frame).T
self.assertTupleEqual(p_AQi.shape, (2, 3))
# Verify CalcTotalMass() calculates a non-zero mass.
p_mass = plant.CalcTotalMass(context=context)
numpy_compare.assert_float_not_equal(p_mass, 0.)
p_mass = plant.CalcTotalMass(
context=context, model_instances=[instance])
numpy_compare.assert_float_not_equal(p_mass, 0.)
p_com = plant.CalcCenterOfMassPositionInWorld(context=context)
self.assertTupleEqual(p_com.shape, (3, ))
p_com = plant.CalcCenterOfMassPositionInWorld(
context=context, model_instances=[instance])
self.assertTupleEqual(p_com.shape, (3, ))
nq = plant.num_positions()
nv = plant.num_velocities()
wrt_list = [
(JacobianWrtVariable.kQDot, nq),
(JacobianWrtVariable.kV, nv),
]
for wrt, nw in wrt_list:
Js_v_ACcm_E = plant.CalcJacobianCenterOfMassTranslationalVelocity(
context=context, with_respect_to=wrt, frame_A=base_frame,
frame_E=world_frame)
self.assert_sane(Js_v_ACcm_E)
self.assertEqual(Js_v_ACcm_E.shape, (3, nw))
Js_v_ACcm_E = plant.CalcJacobianCenterOfMassTranslationalVelocity(
context=context, model_instances=[instance],
with_respect_to=wrt, frame_A=base_frame, frame_E=world_frame)
self.assert_sane(Js_v_ACcm_E)
self.assertEqual(Js_v_ACcm_E.shape, (3, nw))
Js_V_ABp_E = plant.CalcJacobianSpatialVelocity(
context=context, with_respect_to=wrt, frame_B=base_frame,
p_BP=np.zeros(3), frame_A=world_frame,
frame_E=world_frame)
self.assert_sane(Js_V_ABp_E)
self.assertEqual(Js_V_ABp_E.shape, (6, nw))
Js_w_AB_E = plant.CalcJacobianAngularVelocity(
context=context, with_respect_to=wrt, frame_B=base_frame,
frame_A=world_frame, frame_E=world_frame)
self.assert_sane(Js_w_AB_E)
self.assertEqual(Js_w_AB_E.shape, (3, nw))
Js_v_AB_E = plant.CalcJacobianTranslationalVelocity(
context=context, with_respect_to=wrt, frame_B=base_frame,
p_BoBi_B=np.zeros(3), frame_A=world_frame, frame_E=world_frame)
self.assert_sane(Js_v_AB_E)
self.assertEqual(Js_v_AB_E.shape, (3, nw))
Js_v_AB_E = plant.CalcJacobianTranslationalVelocity(
context=context, with_respect_to=wrt, frame_B=base_frame,
p_BoBi_B=np.zeros((3, 3)), frame_A=world_frame,
frame_E=world_frame)
self.assert_sane(Js_v_AB_E)
self.assertEqual(Js_v_AB_E.shape, (9, nw))
L_WSP_W = plant.CalcSpatialMomentumInWorldAboutPoint(
context=context, p_WoP_W=np.zeros(3))
self.assert_sane(L_WSP_W.translational(), nonzero=False)
self.assert_sane(L_WSP_W.rotational(), nonzero=False)
self.assertIsInstance(L_WSP_W, SpatialMomentum_[T])
L_WSP_W = plant.CalcSpatialMomentumInWorldAboutPoint(
context=context, model_instances=[default_model_instance()],
p_WoP_W=np.zeros(3))
self.assert_sane(L_WSP_W.translational(), nonzero=False)
self.assert_sane(L_WSP_W.rotational(), nonzero=False)
self.assertIsInstance(L_WSP_W, SpatialMomentum_[T])
abias_ACcm_E = plant.CalcBiasCenterOfMassTranslationalAcceleration(
context=context, with_respect_to=JacobianWrtVariable.kV,
frame_A=world_frame, frame_E=world_frame)
self.assert_sane(abias_ACcm_E, nonzero=False)
self.assertEqual(abias_ACcm_E.shape, (3,))
AsBias_ABp_E = plant.CalcBiasSpatialAcceleration(
context=context, with_respect_to=JacobianWrtVariable.kV,
frame_B=base_frame, p_BoBp_B=np.zeros(3), frame_A=world_frame,
frame_E=world_frame)
self.assert_sane(AsBias_ABp_E.rotational(), nonzero=False)
self.assert_sane(AsBias_ABp_E.translational(), nonzero=False)
asBias_ABi_E = plant.CalcBiasTranslationalAcceleration(
context=context, with_respect_to=JacobianWrtVariable.kV,
frame_B=base_frame, p_BoBi_B=np.zeros(3), frame_A=world_frame,
frame_E=world_frame)
self.assert_sane(asBias_ABi_E, nonzero=False)
self.assertEqual(asBias_ABi_E.shape, (3, 1))
# Compute body pose.
X_WBase = plant.EvalBodyPoseInWorld(context, base)
self.assertIsInstance(X_WBase, RigidTransform)
# Set pose for the base.
X_WB_desired = RigidTransform.Identity()
X_WB = plant.CalcRelativeTransform(context, world_frame, base_frame)
plant.SetFreeBodyPose(
context=context, body=base, X_WB=X_WB_desired)
numpy_compare.assert_float_equal(
X_WB.GetAsMatrix4(),
numpy_compare.to_float(X_WB_desired.GetAsMatrix4()))
# Set a spatial velocity for the base.
v_WB = SpatialVelocity(w=[1, 2, 3], v=[4, 5, 6])
plant.SetFreeBodySpatialVelocity(
context=context, body=base, V_WB=v_WB)
v_base = plant.EvalBodySpatialVelocityInWorld(context, base)
numpy_compare.assert_float_equal(
v_base.rotational(), numpy_compare.to_float(v_WB.rotational()))
numpy_compare.assert_float_equal(
v_base.translational(),
numpy_compare.to_float(v_WB.translational()))
# Compute accelerations.
vdot = np.zeros(nv)
A_WB_array = plant.CalcSpatialAccelerationsFromVdot(
context=context, known_vdot=vdot)
self.assertEqual(len(A_WB_array), plant.num_bodies())
# Make sure we can call these methods.
base.SetMass(context=context, mass=1.0)
base.SetCenterOfMassInBodyFrame(context=context, com=[0.0, 0.0, 0.0])
M = SpatialInertia_[T](1, [0, 0, 0], UnitInertia_[T](1, 1, 1))
base.SetSpatialInertiaInBodyFrame(context=context, M_Bo_B=M)
@numpy_compare.check_all_types
def test_multibody_state_access(self, T):
MultibodyPlant = MultibodyPlant_[T]
plant_f = MultibodyPlant_[float](0.0)
file_name = FindResourceOrThrow(
"drake/multibody/benchmarks/acrobot/acrobot.sdf")
# N.B. `Parser` only supports `MultibodyPlant_[float]`.
Parser(plant_f).AddModelFromFile(file_name)
plant_f.Finalize()
plant = to_type(plant_f, T)
context = plant.CreateDefaultContext()
nq = 2
nv = 2
nu = 1
self.assertEqual(plant.num_positions(), nq)
self.assertEqual(plant.num_velocities(), nv)
self.assertEqual(plant.num_actuators(), nu)
q0 = np.array([3.14, 2.])
v0 = np.array([-0.5, 1.])
x0 = np.concatenate([q0, v0])
# The default state is all values set to zero.
x = plant.GetPositionsAndVelocities(context)
numpy_compare.assert_float_equal(x, np.zeros(4))
# WARNING: The following oddities occur from the fact that
# `ndarray[object]` cannot be referenced (#8116). Be careful when
# writing scalar-generic code.
if T == float: