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import pytest
import math
import numpy as np
import dartpy as dart
def read_world(uri: dart.common.Uri):
options = dart.utils.SdfParser.Options()
options.mDefaultRootJointType = dart.utils.SdfParser.RootJointType.FIXED
world = dart.utils.SdfParser.readWorld(uri, options)
for i in range(world.getNumSkeletons()):
skel = world.getSkeleton(i)
for j in range(skel.getNumJoints()):
joint = skel.getJoint(j)
joint.setLimitEnforcement(True)
return world
def test_static():
# Load world
world = read_world("dart://sample/sdf/test/force_torque_test.world")
assert world is not None
assert world.getNumSkeletons() == 1
# Check if the world is correctly loaded
model_1 = world.getSkeleton(0)
assert model_1 is not None
assert model_1.getName() == "model_1"
assert model_1.getNumBodyNodes() == 2
assert model_1.getNumJoints() == 2
world.setGravity([0, 0, -50])
# Simulate 1 step
world.step()
t = world.getTime()
# Get time step size
dt = world.getTimeStep()
assert dt > 0
assert t == pytest.approx(dt)
# Get joint and get force torque
link_1 = model_1.getBodyNode("link_1")
assert link_1 is not None
link_2 = model_1.getBodyNode("link_2")
assert link_2 is not None
joint_01 = model_1.getJoint("joint_01")
assert joint_01 is not None
joint_12 = model_1.getJoint("joint_12")
assert joint_12 is not None
tf = dart.math.Isometry3()
# Run 10 steps
for _ in range(10):
world.step()
#----------------------
# Test joint_01 wrench
#----------------------
# Reference adjustment for the difference of the joint frame conventions
# between Gazebo and DART
tf.set_identity()
tf.set_translation(joint_01.getTransformFromParentBodyNode().translation())
parent_frame01 = dart.dynamics.SimpleFrame(dart.dynamics.Frame.World(), "parent_frame01", tf)
tf.set_identity()
tf.set_translation(joint_01.getTransformFromChildBodyNode().translation())
child_frame01 = dart.dynamics.SimpleFrame(link_1, "child_frame01", tf)
parent_f01 = joint_01.getWrenchToParentBodyNode(parent_frame01)
assert (parent_f01 == [0, 0, 0, 0, 0, 1000]).all()
child_f01 = joint_01.getWrenchToChildBodyNode(child_frame01)
assert (child_f01 == -parent_f01).all()
#----------------------
# Test joint_12 wrench
#----------------------
# Reference adjustment for the difference of the joint frame conventions
# between Gazebo and DART
tf.set_identity()
tf.set_translation(joint_12.getTransformFromParentBodyNode().translation())
parent_frame12 = dart.dynamics.SimpleFrame(link_1, "parent_frame12", tf)
tf.set_identity()
tf.set_translation(joint_12.getTransformFromChildBodyNode().translation())
child_frame12 = dart.dynamics.SimpleFrame(link_2, "child_frame12", tf)
parent_f12 = joint_12.getWrenchToParentBodyNode(parent_frame12)
assert (parent_f12 == [0, 0, 0, 0, 0, 500]).all()
child_f12 = joint_12.getWrenchToChildBodyNode(child_frame12)
assert (child_f12 == -parent_f12).all()
def test_force_torque_at_joint_limits():
# Load world
world = read_world("dart://sample/sdf/test/force_torque_test.world")
assert world is not None
assert world.getNumSkeletons() == 1
# Check if the world is correctly loaded
model_1 = world.getSkeleton(0)
assert model_1 is not None
assert model_1.getName() == "model_1"
assert model_1.getNumBodyNodes() == 2
assert model_1.getNumJoints() == 2
world.setGravity([0, 0, -50])
# Simulate 1 step
world.step()
t = world.getTime()
# Get time step size
dt = world.getTimeStep()
assert dt > 0
assert t == pytest.approx(dt)
# Get joint and get force torque
link_1 = model_1.getBodyNode("link_1")
assert link_1 is not None
link_2 = model_1.getBodyNode("link_2")
assert link_2 is not None
joint_01 = model_1.getJoint("joint_01")
assert joint_01 is not None
joint_12 = model_1.getJoint("joint_12")
assert joint_12 is not None
# Change gravity so that the top link topples over, then remeasure
world.setGravity([-30, 10, -50])
# Wait for dynamics to be stabilized
for i in range(2000):
world.step()
tf = dart.math.Isometry3()
# Run 5 steps
for _ in range(5):
world.step()
#----------------------
# Test joint_01 wrench
#----------------------
# Reference adjustment for the difference of the joint frame conventions
# between Gazebo and DART
tf.set_identity()
tf.set_translation(joint_01.getTransformFromParentBodyNode().translation())
parent_frame01 = dart.dynamics.SimpleFrame(dart.dynamics.Frame.World(), "parent_frame01", tf)
tf.set_identity()
tf.set_translation(joint_01.getTransformFromChildBodyNode().translation())
child_frame01 = dart.dynamics.SimpleFrame(link_1, "child_frame01", tf)
parent_f01 = joint_01.getWrenchToParentBodyNode(parent_frame01)
assert np.isclose(parent_f01, [750, 0, -450, 600, -200, 1000], rtol=0.1, atol=4.5).all()
child_f01 = joint_01.getWrenchToChildBodyNode(child_frame01)
assert np.isclose(child_f01, [-750, -450, 0, -600, 1000, 200], rtol=0.1, atol=4.5).all()
#----------------------
# Test joint_12 wrench
#----------------------
# Reference adjustment for the difference of the joint frame conventions
# between Gazebo and DART
tf.set_identity()
tf.set_translation(joint_12.getTransformFromParentBodyNode().translation())
parent_frame12 = dart.dynamics.SimpleFrame(link_1, "parent_frame12", tf)
tf.set_identity()
tf.set_translation(joint_12.getTransformFromChildBodyNode().translation())
child_frame12 = dart.dynamics.SimpleFrame(link_2, "child_frame12", tf)
parent_f12 = joint_12.getWrenchToParentBodyNode(parent_frame12)
assert np.isclose(parent_f12, [250, 150, 0, 300, -500, -100], rtol=0.1, atol=0.1).all()
child_f12 = joint_12.getWrenchToChildBodyNode(child_frame12)
assert np.isclose(child_f12, [-250, -150, 0, -300, 500, 100], rtol=0.1, atol=0.1).all()
def test_force_torque_at_joint_limits_with_external_forces():
# Load world
world = read_world("dart://sample/sdf/test/force_torque_test2.world")
assert world is not None
assert world.getNumSkeletons() == 1
# Check if the world is correctly loaded
model_1 = world.getSkeleton(0)
assert model_1 is not None
assert model_1.getName() == "boxes"
assert model_1.getNumBodyNodes() == 3
assert model_1.getNumJoints() == 3
assert model_1.getNumDofs() == 2
# The first joint is fixed joint
assert model_1.getRootJoint().getType() == dart.dynamics.WeldJoint.getStaticType()
world.setGravity([0, 0, -50])
# Simulate 1 step
world.step()
t = world.getTime()
# Get time step size
dt = world.getTimeStep()
assert dt > 0
assert t == pytest.approx(dt)
# Get joint and get force torque
link_1 = model_1.getBodyNode("link1")
assert link_1 is not None
link_2 = model_1.getBodyNode("link2")
assert link_2 is not None
link_3 = model_1.getBodyNode("link3")
assert link_3 is not None
joint_12 = model_1.getJoint("joint1")
assert joint_12 is not None
joint_23 = model_1.getJoint("joint2")
assert joint_23 is not None
tf = dart.math.Isometry3()
# Run 45005 steps
kp1 = 5e+4
kp2 = 1e+4
target1 = 0
target2 = -0.25 * math.pi
steps = 4500
for _ in range(steps):
# PD control
j1_state = joint_12.getPosition(0)
j2_state = joint_23.getPosition(0)
p1_error = target1 - j1_state
p2_error = target2 - j2_state
effort1 = kp1 * p1_error
effort2 = kp2 * p2_error
joint_12.setForce(0, effort1)
joint_23.setForce(0, effort2)
world.step()
assert joint_12.getPosition(0) == pytest.approx(target1, abs=1e-1)
assert joint_23.getPosition(0) == pytest.approx(target2, abs=1e-1)
tol = 2
#----------------------
# Test joint_12 wrench
#----------------------
# Reference adjustment for the difference of the joint frame conventions
# between Gazebo and DART
tf.set_identity()
tf.set_translation(joint_12.getTransformFromParentBodyNode().translation())
parent_frame01 = dart.dynamics.SimpleFrame(link_1, "parent_frame01", tf)
tf.set_identity()
tf.set_translation(joint_12.getTransformFromChildBodyNode().translation())
child_frame01 = dart.dynamics.SimpleFrame(link_2, "child_frame01", tf)
parent_f01 = joint_12.getWrenchToParentBodyNode(parent_frame01)
assert np.isclose(parent_f01, [25, -175, 0, 0, 0, 300], rtol=0.01, atol=tol).all()
child_f01 = joint_12.getWrenchToChildBodyNode(child_frame01)
assert np.isclose(child_f01, [-25, 175, 0, 0, 0, -300], rtol=0.01, atol=tol).all()
#----------------------
# Test joint_23 wrench
#----------------------
# Reference adjustment for the difference of the joint frame conventions
# between Gazebo and DART
tf.set_identity()
tf.set_translation(joint_23.getTransformFromParentBodyNode().translation())
parent_frame12 = dart.dynamics.SimpleFrame(link_2, "parent_frame12", tf)
tf.set_identity()
tf.set_translation(joint_23.getTransformFromChildBodyNode().translation())
child_frame12 = dart.dynamics.SimpleFrame(link_3, "child_frame12", tf)
parent_f12 = joint_23.getWrenchToParentBodyNode(parent_frame12)
assert np.isclose(parent_f12, [25, 0, 0, 0, 0, 50], rtol=0.01, atol=tol).all()
child_f12 = joint_23.getWrenchToChildBodyNode(child_frame12)
assert np.isclose(child_f12, [-17.678, 0, 17.679, -35.355, 0, -35.355], rtol=0.01, atol=tol).all()
if __name__ == "__main__":
pytest.main()
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