Allow to set a robot's base (RCF) #762
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| self._origin = value | ||
| # The following is a world-relative frame representing the origin, which change with | ||
| # the joint state, while `origin` is parent-relative and static. | ||
| self.current_origin = value.copy() |
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maybe i haven't properly thought this through, but should this be
self.current_origin = self.current_origin @ self.origin.inverse() @ value
where i'm ignoring the distinction between a frame and its transformation
| self._axis = value | ||
| # The following is a world-relative axis which change with | ||
| # the joint state, while `axis` is parent-relative and static. | ||
| self.current_axis = value.copy() |
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And similarly here, should we not 'remember' the transformations that have already been applied to the current_axis?
src/compas/robots/model/robot.py
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| base_link = self.get_link_by_name(self.get_base_link_name()) | ||
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| # if there's no fixed joint and there is an RCF is explicitly set, return it as a transform | ||
| ref_frame = Frame.worldXY() |
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I don't understand. Say you've got a robot with a proper base link. Then you set robot.rfc = <some frame>. This will change the origin of the base link. But if then you access robot.rcf you'll get the identity transformation in return. Does that make sense? Is that supposed to make sense?
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nope, the comment might be somewhat misleading if it's right above this line, but Frame.worldXY() is the default if the if right after is not true. In the case where you set the rcf, then the if goes in, and the ref_frame is that one instead.
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i think i didn't express myself well. consider the following code:
import math
import compas_fab
from compas.robots import LocalPackageMeshLoader, RobotModel, Frame
urdf_filepath = compas_fab.get('universal_robot/ur_description/urdf/ur5.urdf')
loader = LocalPackageMeshLoader(compas_fab.get('universal_robot'), 'ur_description')
model = RobotModel.from_urdf_file(urdf_filepath)
assert model.rcf == Frame.worldXY()
model.rcf = Frame.from_euler_angles([math.pi, 0, 0], point=[1,0,0])
assert model.rcf == Frame.worldXY()
Without knowing the internals of rcf, that doesn't make any sense to the user.
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You're totally right. I'll fix.
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This should be now fixed (a4a3e8f) along with simpler code path to determine what happens where (and a bit less duplication)
It will also need to be propagated to the |
Co-authored-by: beverlylytle <[email protected]>
Co-authored-by: beverlylytle <[email protected]>
src/compas/utilities/decorators.py
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| if event_observers: | ||
| event_observers.remove(callback) | ||
| if not event_observers: | ||
| del event_source.__event_observers__[event_key] |
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I see a lot of potential for exceptions being raised with this function. If there is a typo in event_name, there will be a KeyError. If the wrong callback is passed there could be a ValueError. Does it make sense to raise custom exceptions for this, rather than the generic and perhaps mysterious ones?
src/compas/utilities/decorators.py
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| Examples | ||
| -------- | ||
| >>> class Test(object): | ||
| ... @observable(event_name='init') |
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I trust myself to type 'init' correctly, but I do not trust myself to type 'updated_transformations' correctly. I know this is what tests are for, but somethings are difficult to test (say, did the image of the robot in blender update correctly when the rcf changed?). Is there a nice way of throwing an exception somewhere if the observable event names for a class don't match up with the observed event names or vice versa? or is that something that shouldn't be protected against?
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I just noticed that |
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@gonzalocasas should this PR move to |
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@gonzalocasas I guess we have decided to shelf this idea for the time being. How about we move it to compas_robots first and manage it from there? |
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I know we said that we will not work on this issue soon, but just to collect one more argument for developing this function, is that the ability to set the robot base (to be different from World frame), can easily fix the orientation of a UR base. |
This adds a property RCF to the robot model (
model.rcf) to allow changing the base frame of the robot. Since operation is potentially quite involved once the model is used inCOMPAS FAB, I will need to add an event emitter or some way in which this model can be observed from an external class and hook into changes (like rcf change) so that those are propagated to backends. I'm still not sure how to do this best so, I'm opening this a draft for comments already now and I will update soon.What type of change is this?
Checklist
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xin the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.CHANGELOG.mdfile in theUnreleasedsection under the most fitting heading (e.g.Added,Changed,Removed).invoke test).invoke lint).compas.datastructures.Mesh.