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Feature: Custom python functions for dependent joints #64

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Feature: Custom python functions for dependent joints #64

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ad3a700
Allow custom python functions for dependent joints
Aug 31, 2021
735e323
Added test example for nonlinear function dependent joint
Aug 31, 2021
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50 changes: 29 additions & 21 deletions joint_state_publisher/src/joint_state_publisher/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -248,32 +248,15 @@ def loop(self):
# Add Free Joint
if name in self.free_joints:
joint = self.free_joints[name]
factor = 1
offset = 0

# Add Dependent Joint
elif name in self.dependent_joints:
param = self.dependent_joints[name]
parent = param['parent']
factor = param.get('factor', 1)
offset = param.get('offset', 0)
# Handle recursive mimic chain
recursive_mimic_chain_joints = [name]
while parent in self.dependent_joints:
if parent in recursive_mimic_chain_joints:
error_message = "Found an infinite recursive mimic chain"
rospy.logerr("%s: [%s, %s]", error_message, ', '.join(recursive_mimic_chain_joints), parent)
sys.exit(1)
recursive_mimic_chain_joints.append(parent)
param = self.dependent_joints[parent]
parent = param['parent']
offset += factor * param.get('offset', 0)
factor *= param.get('factor', 1)
joint = self.free_joints[parent]
joint = self.compute_dependent_joint(name, [])

if has_position and 'position' in joint:
msg.position[i] = joint['position'] * factor + offset
msg.position[i] = joint['position']
if has_velocity and 'velocity' in joint:
msg.velocity[i] = joint['velocity'] * factor
msg.velocity[i] = joint['velocity']
if has_effort and 'effort' in joint:
msg.effort[i] = joint['effort']

Expand All @@ -284,6 +267,31 @@ def loop(self):
r.sleep()
except rospy.exceptions.ROSTimeMovedBackwardsException:
pass

def compute_dependent_joint(self, name, recursive_mimic_chain_joints):
param = self.dependent_joints[name]
parent = param['parent']
loc = param.copy()
loc['factor'] = param.get('factor', 1) #to allow default behaviour
loc['offset'] = param.get('offset', 0)
dependent_fun = param.get('fun', "position = parent_position * factor + offset")
#Handle recursive mimic chain
recursive_mimic_chain_joints.append(name)
if (parent in self.dependent_joints):
if parent in recursive_mimic_chain_joints:
error_message = "Found an infinite recursive mimic chain"
rospy.logerr("%s: [%s, %s]", error_message, ', '.join(recursive_mimic_chain_joints), parent)
sys.exit(1)
loc['parent_position'] = self.compute_dependent_joint(parent, recursive_mimic_chain_joints)['position']
else:
loc['parent_position'] = self.free_joints[parent]['position']

exec(dependent_fun, globals(), loc)
ret = {}
ret['position'] = loc['position']
#TODO: velocity
return ret


def update(self, delta):
for name, joint in self.free_joints.iteritems():
Expand Down
57 changes: 57 additions & 0 deletions joint_state_publisher/test/nonlinear_dependent_chain.urdf
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Original file line number Diff line number Diff line change
@@ -0,0 +1,57 @@
<?xml version="1.0"?>
<robot name="nonlinear_dependent_chain">
<link name="finger1">
<visual>
<origin xyz="0.0628 -0.0207 0.0" rpy="0 0 -0.2584" />
<geometry>
<box size="0.149 0.0277 0.07" />
</geometry>
</visual>
</link>
<link name="finger2">
<visual>
<origin xyz="0.0628 0.0207 0.0" rpy="0 0 0.2584" />
<geometry>
<box size="0.149 0.0277 0.07" />
</geometry>
</visual>
</link>
<link name="base">
<visual>
<origin xyz="0 0 0" rpy="0 0 0" />
<geometry>
<box size="0.2 0.2 0.001" />
</geometry>
</visual>
</link>

<link name="piston">
<visual>
<origin xyz="0 0 -0.1" rpy="0 0 0" />
<geometry>
<box size="0.02 0.02 0.2" />
</geometry>
</visual>
</link>

<joint name="finger1_joint" type="revolute">
<origin rpy="0 -1.57 0" xyz="0 -0.033 0" />
<parent link="base" />
<child link="finger1" />
<axis xyz="0 0 -1" />
<limit effort="10" velocity="10" lower="-1" upper="1" />
</joint>
<joint name="finger2_joint" type="revolute">
<origin rpy="0 -1.57 0" xyz="0 0.033 0" />
<parent link="base" />
<child link="finger2" />
<axis xyz="0 0 -1" />
<limit effort="10" velocity="10" lower="-1" upper="1" />
</joint>
<joint name="piston_joint" type="prismatic">
<parent link="base" />
<child link="piston" />
<axis xyz="0 0 1"/>
<limit effort="10" velocity="10" lower="-0.02" upper="0.04" />
</joint>
</robot>
33 changes: 33 additions & 0 deletions joint_state_publisher/test/test_nonlinear_dependent_chain.launch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,33 @@
<?xml version="1.0"?>
<launch>
<param name="robot_description" textfile="$(find joint_state_publisher)/test/nonlinear_dependent_chain.urdf"/>

<rosparam>
dependent_joints:
finger1_joint: {
parent: piston_joint,
p_off: -0.004,
z1: 0.03636756796927724,
z2: 0.025,
q_off: -0.820403314,
fun: "j = parent_position + p_off\nposition = (-2.0 * math.atan2((z1 - math.sqrt(math.pow(z1, 2) + math.pow(z2, 2) - math.pow(j, 2))), (z2 - j))) + q_off"
}
finger2_joint: {
parent: finger1_joint,
fun: "position = -1 * parent_position"
}
</rosparam>

<node pkg="joint_state_publisher_gui" type="joint_state_publisher_gui" name="dut_joint_state_publisher_gui">
<param name="rate" value="10"/>
</node>

<node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher" output="screen"/>
<test pkg="rostest" type="hztest" name="hztest" test-name="hztest_mimic_chain">
<param name="topic" value="joint_states"/>
<param name="hz" value="10"/>
<param name="hzerror" value="0.1"/>
<param name="test_duration" value="10"/>
<param name="wait_time" value="10"/>
</test>
</launch>