Wheel Joint

Create a car with two wheel and wheel joints

Uses:

• b2d.WheelJointDef

• b2d.WheelJoint

Imports

pyb2d is imported as b2d

import b2d
import numpy as np

These imports are only needed for plotting. b2d.plot requires OpenCV to be installed!

import b2d.plot
import matplotlib.pyplot as plt

The world and ground body

world = b2d.world(gravity=(0, -10))
edge = world.create_static_body(
    position=(0, 0), fixtures=b2d.fixture_def(shape=b2d.edge_shape([(-20, 0), (5, 0)]))
)

# random slope
x = np.linspace(5, 50, 10)
y = np.random.rand(10) * 4 - 2
y[0] = 0
xy = np.stack([x, y]).T
xy = np.flip(xy, axis=0)
edge = world.create_static_body(
    position=(0, 0),
    fixtures=b2d.fixture_def(shape=b2d.chain_shape(xy, prev_vertex=(10, 0))),
)

create car

left_wheel = world.create_dynamic_body(
    position=(-3, 2),
    fixtures=b2d.fixture_def(shape=b2d.circle_shape(radius=2), density=1),
)
right_wheel = world.create_dynamic_body(
    position=(3, 2),
    fixtures=b2d.fixture_def(shape=b2d.circle_shape(radius=2), density=1),
)

chasis = world.create_dynamic_body(
    position=(0, 2),
    fixtures=b2d.fixture_def(shape=b2d.polygon_shape(box=[3, 0.5]), density=1),
)

wheel_joint_def = dict(
    stiffness=10,
    enable_motor=True,
    motor_speed=-100,
    max_motor_torque=100,
    collide_connected=False,
    enable_limit=True,
    lower_translation=-0.4,
    upper_translation=0.4,
    local_axis_a=(0, 1),
)
world.create_wheel_joint(chasis, left_wheel, local_anchor_a=(-3, 0), **wheel_joint_def)
world.create_wheel_joint(chasis, right_wheel, local_anchor_a=(3, 0), **wheel_joint_def)

fig, ax, ani = b2d.plot.animate_world(world, world_margin=(10, 10), t=5)
ani
plt.show()

Once Loop Reflect

/home/runner/.local/lib/python3.10/site-packages/b2d/plot.py:128: UserWarning: You passed in an explicit save_count=121 which is being ignored in favor of frames=121.
  ani = animation.FuncAnimation(