Brick.AGX python interface development
Project description
BRICK AGX
The brickagx package implements all Brick bundles such as Physics, Robotics, DriveTrain and Simulation using AGX Dynamics Real-time multi-body simulation. The package contains python bindings and native libraries needed to load and run .brick files.
Prerequisites
- Python 3.8 on Ubuntu 20.04
- Python 3.9 on Windows or OSX
- AGX Dynamics and an AGX Dynamics License
BRICK version | Required installed AGX version |
---|---|
0.0.14 - 0.0.15 | 2.36.1.4 |
0.0.16 - 0.0.17 | 2.36.1.5 |
Install
To get the version corresponding to your AGX on Windows do:
setup_env.bat
pip install %AGX_DATA_DIR%/agx-pypi
pip install -U brickagx
To get the version corresponding to your AGX on OSX and Linux do:
source setup_env.sh
pip3 install $AGX_DATA_DIR/agx-pypi
pip3 install -U brickagx
License
Usage Examples
Given the python file and brick file below, run with:
python3 inverted_pendulum.py
To just simulate the brick file without controllers, do:
brickview inverted_pendulum.brick
or python3 -m rebrick.view inverted_pendulum.brick
Store contents below in a new file named inverted_pendulum.brick
:
Rod is Physics3D.RigidBody:
inertia.mass: 10
geometry is Physics3D.Box:
size: Math.Vec3.fromXYZ(0.1, 0.1, 1)
arrow is Physics3D.Box:
local_transform:
position.z: 0.5
rotation: Math.Quat.angleAxis(Math.PI / 4, Math.Vec3.Y_AXIS())
size: Math.Vec3.fromXYZ(0.071, 0.1, 0.071)
mate_connector is Physics3D.MateConnector:
position.z: -geometry.size.z * 0.7
main_axis: Math.Vec3.Y_AXIS()
normal: Math.Vec3.Z_AXIS()
Cart is Physics3D.RigidBody:
inertia.mass: 10
geometry is Physics3D.Box:
size: Math.Vec3.fromXYZ(0.1, 0.1, 0.1)
connector is Physics3D.MateConnector:
main_axis: Math.Vec3.X_AXIS()
normal: Math.Vec3.Z_AXIS()
rotated_connector is Physics3D.MateConnector:
main_axis: Math.Vec3.Y_AXIS()
normal: Math.Vec3.Z_AXIS()
PendulumScene is Physics3D.System:
world_connector is Physics3D.MateConnector:
main_axis: Math.Vec3.X_AXIS()
normal: Math.Vec3.Z_AXIS()
cart is Cart
rod is Rod
prismatic is Physics3D.Prismatic:
charges: [world_connector, cart.connector]
cart_motor is Physics3D.LinearVelocityMotor:
desired_speed: 0
charges: prismatic.charges
hinge is Physics3D.Hinge:
initial_angle: 0
charges: [cart.rotated_connector, rod.mate_connector]
motor_input is Simulation.LinearVelocityMotorVelocityInput:
motor: cart_motor
hinge_angle_output is Simulation.HingeAngleOutput:
hinge: hinge
hinge_angular_velocity_output is Simulation.HingeAngularVelocityOutput:
hinge: hinge
cart_position_output is Simulation.RigidBodyPositionOutput:
rigid_body: cart
cart_velocity_output is Simulation.RigidBodyVelocityOutput:
rigid_body: cart
Store contents below in a new file named inverted_pendulum.py
:
import agxOSG
import agxSDK
import os
import signal
from brickbundles import bundle_path
# Import useful utilities to access the current simulation, graphics root and application
from agxPythonModules.utils.environment import init_app, simulation, root
from rebrick import Math, Simulation, Signals
from rebrick import InputSignalListener, OutputSignalListener, load_brickfile
def file_dir():
return os.path.dirname(os.path.abspath(__file__))
def pendulum():
return f"{file_dir()}/inverted_pendulum.brick"
class PDController:
def __init__(self, kp, kd, goal):
self.kp = kp
self.kd = kd
self.goal = goal
def observe(self, x, xdot):
error = self.goal - x
return self.kp * error - self.kd * xdot
class CartController(agxSDK.StepEventListener):
motor_input: Simulation.LinearVelocityMotorVelocityInput
cart: PDController
pole: PDController
def __init__(self, motor_input: Simulation.LinearVelocityMotorVelocityInput):
super().__init__()
self.motor_input = motor_input
self.cart = PDController(kp=10, kd=5, goal=0)
self.pole = PDController(kp=20, kd=5, goal=0)
def pre(self, t):
if t == 0.0:
hinge_angle = 0
hinge_angular_velocity = 0
cart_position = Math.Vec3.fromXYZ(0,0,0)
cart_velocity = Math.Vec3.fromXYZ(0,0,0)
else:
signal_values = {signal.source().getName():signal.value() for signal in Signals.getOutputSignals()}
hinge_angle = signal_values["PendulumScene.hinge_angle_output"]
hinge_angular_velocity = signal_values["PendulumScene.hinge_angular_velocity_output"]
cart_position = signal_values["PendulumScene.cart_position_output"]
cart_velocity = signal_values["PendulumScene.cart_velocity_output"]
u_cart = self.cart.observe(cart_position.x(), cart_velocity.x())
u_pole = self.pole.observe(hinge_angle, hinge_angular_velocity)
Signals.sendInputSignal(Simulation.RealInputSignal.create(-u_cart - u_pole, self.motor_input))
def buildScene():
brick_scene, assembly = load_brickfile(simulation(), pendulum(), bundle_path(), "")
# Add a signal listener so that signals are picked up from inputs
input_signal_listener = InputSignalListener(assembly)
output_signal_listener = OutputSignalListener(assembly, brick_scene)
simulation().add(input_signal_listener, InputSignalListener.RECOMMENDED_PRIO)
simulation().add(output_signal_listener, OutputSignalListener.RECOMMENDED_PRIO)
simulation().add(assembly.get())
agxOSG.createVisual(assembly.get(), root())
motor_input: Simulation.LinearVelocityMotorVelocityInput = brick_scene.getDynamic("motor_input").asObject()
controller = CartController(motor_input)
simulation().add(controller)
def handler(signum, frame):
os._exit(0)
signal.signal(signal.SIGINT, handler)
init = init_app(name=__name__,
scenes=[(buildScene, '1')],
autoStepping=True, # Default: False
onInitialized=lambda app: print('App successfully initialized.'),
onShutdown=lambda app: print('App successfully shut down.'))
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