Dear Sylvain,
Thanks for your help, I think it clears up some of my problem.
— On Tue, 1/13/09, AnyScript Support <anyscriptsup@anybodytech.com> wrote:
From: AnyScript Support <anyscriptsup@anybodytech.com>
Subject: RE: [AnyScript] Re: Problem on modeling a robot to drive human arm
To: anyscript@yahoogroups.com
Date: Tuesday, January 13, 2009, 9:28 PM
Hi Arif,
The spherical joint alone between the hand and the robot is not enough to
drive the 4 arm’s dof you want. You clearly need a 4 constraints joint on
the hand to do it.
The constraint combination (3 translational and 1 rotational) is equivalent
to a universal joint in anybody, leaving only 2 rotations free. You can
investigate the effect of such joint in anybody without modifying too much
your model, just change the spherical joint to universal and modify the
driver in consequence (you need a four component driver for this joint). It
should be able to drive the arm the way you want it.
Now I’m not an expert in robot, it seems a gantry robot has the good
constraint combination, but there might be others with a 4 constraint joint.
I honestly don’t know which is best and leave this choice up to you.
Best regards,
Sylvain, AnyBody Support
From: anyscript@yahoogrou ps.com [mailto:anyscript@yahoogrou ps.com] On Behalf
Of auwjong_4121f
Sent: 13. januar 2009 12:02
To: anyscript@yahoogrou ps.com
Subject: [AnyScript] Re: Problem on modeling a robot to drive human arm
Dear Sylvain,
Yes, you are correct, at this point I am using the robot to drive only
the 3 glenohumeral joints and elbow flextion.
With the above mentioned joints, I have 4 drivers that I have to
removed. However, the connection between the hand glove and the robot
is a spherical joint, which means I am only adding 3 constraints.
You did recommended me to use 3 translational and 1 rotational axis.
Does it mean that I need to use different type of robot? I am thinking
of something like gantry robot (3 translational axis) + 1 revolute joint
Thank you thank you
— In anyscript@yahoogrou <mailto:anyscript% 40yahoogroups. com> ps.com,
AnyScript Support <anyscriptsup@ …>
wrote:
>
> Hi Arif,
>
>
>
> First let me be sure i understand correctly how is working the device: I
> suppose the base of the robot (purple part) is fixed to the ground,
then the
> different dof of the robot are fully driven and the extremity is
attached to
> the hand. And the robot should drive the arm (all 3 glenohumeral
joints and
> the elbow joint) from this contact point on the hand. You didn’t
mention the
> forearm pronation so I will suppose you don’t want to drive it with the
> robot. Please correct me if I missed something.
>
>
>
> By linking the hand to the robot you are adding new constraints to
the arm,
> those new constraints should drive the dof mentioned above. To allow
those
> dof to be driven by the robot you must of course free them from the
already
> existing drivers (glenohumeralFlexio n, glenohumeralExterna lRotation,
> glenohumeralAbducti on and elbowFlexion) . I think this is what you
tried to
> do.
>
> If you remove those 4 drivers you need to add 4 new drivers to keep the
> balance, if not you will get the error saying that the model is
> kinematically indeterminate. So there should 4 constraints between
the hand
> and the robot.
>
> Those 4 have to be chosen from the 6 possible (3 translations and 3
> rotations) so that they correspond as much as possible to one that
have been
> removed. This is not always easy, in that case I think it could be the 3
> translations plus the rotation around the vertical axis of the robot
arm (x
> if I see it correctly on the picture).
>
>
>
> To make it easier I recommend removing one dof of the arm at a time and
> replacing it by its corresponding constraint on the hand and always
keep the
> model running.
>
>
>
> Best regards,
>
> Sylvain, AnyBody Support
>
>
>
>
>
> _____
>
> From: anyscript@yahoogrou <mailto:anyscript% 40yahoogroups. com> ps.com
[mailto:anyscript@ yahoogrou <mailto:anyscript% 40yahoogroups. com> ps.com]
On Behalf
> Of auwjong_4121f
> Sent: 12. januar 2009 12:11
> To: anyscript@yahoogrou <mailto:anyscript% 40yahoogroups. com> ps.com
> Subject: [AnyScript] Problem on modeling a robot to drive human arm
>
>
>
> Hi,
>
> My name is Arif Oyong, I am doing research on the use of robot for
> stroke rehabilitation. One of the thing that I am doing now is the
> implication of robot on the arm muscle.
>
> Modifying from the standing model, I have made a simple 3 link
> manipulator to drive the human arm. I have uploaded the photos in
> the
> photo section. My problem is, the configuration only works when I
> eliminate: glenohumeralFlexion , glenohumeralExterna lRotation, and
> elbowFlexion driver in the JointsandDrivers. any (shown in the photos
> uploaded)
>
> When I tried to eliminate glenohumeralFlexion ,
> glenohumeralAbducti on,
> and elbowFlexion, the analysis failed at time step 0. Why is that
> happening? Is it because of the initial position of the robot and
> human arm?
>
> Another question, based on my configuration, the robot should affect
> all 3 of the glenohumeral joint and elbow joint. However, if I try
> to
> remove all above joints, the analysis said thhat the study contains
> too few constraints to be kinematically determinate. Does it mean
> that I need to add another robot link to add another constraint?
>
> Thank you for help,
>
> Arif Oyong
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
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