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urdf_utils.py
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urdf_utils.py
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import pybullet as p
import math
def find_joint_count(ID):
"""Counts the number of joints in robot.
Arguments:
ID -- An integer representing a robot, as return from the p.loadURDF()
method.
Returns:
joint_count -- An integer representing the number of joints as defined
in the *.urdf file.
"""
joint_count = 0
while True:
try:
p.getJointState(ID, joint_count)
joint_count += 1
except:
return joint_count
def test_revolute_extents(ID, joint_count, speed=0.2, precision=5, delay=0.001):
"""Iterates through each joint and rotates them to the extent of its
movement. Returns a list of tuples representing the (minimum, maximum) of
each joint. Note: this has only been tested on robots with only revolute
joints.
Arguments:
ID -- An integer representing a robot, as return from the
p.loadURDF() method.
joint_count -- An integer representing the number of joints as defined
in the *.urdf file. Can be calculated with the find_joint_count()
function.
speed -- A number representing the rate at which each link rotates.
precision -- An integer representing the number of decimal places to
which the extents will be calculated to.
delay -- A number that artificially delays the simulation steps
with time.sleep(delay).
Returns:
extents -- A list of tuples representing the minimum and maximum extents
of rotation for each joint.
"""
# Set Starting States
starting_states = [p.getJointState(ID, i)[0] for i in range(joint_count)]
# Extents
extents = [2 * [starting_states[i]] for i in range(joint_count)]
# Initial Search Space
current_joint = 0
current_direction = -1
# Search
while True:
# Check for Final Joint
if current_joint == joint_count:
extent = [(180 * rad / math.pi for rad in pair) for pair in extents]
return [tuple(pair) for pair in extent]
# Update Extents
current_state = p.getJointState(ID, current_joint)[0]
current_min = extents[current_joint][0]
current_max = extents[current_joint][1]
if current_state < current_min:
extents[current_joint][0] = current_state
if current_state > current_max:
extents[current_joint][1] = current_state
# Make Move
target_state = current_state + (current_direction * speed)
p.setJointMotorControl2(
bodyIndex=ID,
jointIndex=current_joint,
controlMode=p.POSITION_CONTROL,
targetPosition=target_state,
)
p.stepSimulation()
if delay > 0:
time.sleep(delay)
# Checks if at Extent
new_state = p.getJointState(ID, current_joint)[0]
new_state_string = str(int(new_state * (10**precision)))
cur_state_string = str(int(current_state * (10**precision)))
if new_state_string == cur_state_string:
if current_direction == 1:
if current_joint < joint_count:
# Reset Joint
p.setJointMotorControl2(
bodyIndex=ID,
jointIndex=current_joint,
controlMode=p.POSITION_CONTROL,
targetPosition=starting_states[current_joint],
)
current_joint += 1
current_direction *= -1