[ros-users] Flexible & remote transmission

Stuart Glaser sglaser at willowgarage.com
Tue Dec 14 22:39:03 UTC 2010


Hi Jeroen,

Could you describe what you're trying to model in more detail?  In
particular, where are the encoders, motors, springs, gears, and joints
in relation to each other?

-Stu

On Tue, Dec 14, 2010 at 4:37 AM, Jeroen Willems <jjpa.willems at gmail.com> wrote:
> Okay I'm looking into the flexibility between the actuator and the joint by
> adding a custom transmission but I'm having some difficulties.
>
> I've looked into the existing transmissions and those are pretty
> straightforward (except for the pr2_gripper).
> I want to add the (linear, rotational) flexibility, I will neglect the
> damping for simplicity.
> I'm used to use the equations of motion:
> Load:  Jl theta_L_ddot + k ( theta_L - theta_M ) = 0
> Motor: Jm theta_M_ddot - k ( theta_L - theta_M ) = u
>
> I don't get it how to implement this in the transmission. I was thinking of
> a little bit of rewriting as in the attachment but it did not influence
> anything at all.
> Would be great if someone has an idea, solution or suggestion on how
> implementing this flexibility.
>
> Thanks in advance
>
> Jeroen
>
> On Sat, Nov 20, 2010 at 21:07, Stuart Glaser <sglaser at willowgarage.com>
> wrote:
>>
>> Hi Joeren,
>>
>> For both of these, the solution is to write a transmission.  Both
>> issues require a specific translation between actuators and joints,
>> and the best way to encode that translation is in a transmission.
>>
>> -Stu
>>
>> On Fri, Nov 19, 2010 at 1:36 AM, Jeroen Willems <jjpa.willems at gmail.com>
>> wrote:
>> > Hi All,
>> >
>> > I'm currently modeling a hexapod in Gazebo but I'm currently having some
>> > difficulties.
>> >
>> > I have basically 2 questions, I hope that this is not a problem for one
>> > post
>> > but both have to do with the transmission:
>> >
>> > 1) Between the actuators and the joints are torsion springs. I haven't
>> > found
>> > something that incorporates flexibility between actuators and joints.
>> > Is there some solution or workaround to obtain this or should I try an
>> > alternative solution like writing a custom transmission?
>> >
>> > 2) As you can imagine I have 6 legs consisting of three links, basically
>> > an
>> > elbow manipulator.
>> > The last two links can be regarded as in a 2D-plane. The third link is
>> > remotely driven.
>> > This means that when rotating the second link the third link does not
>> > change
>> > the rotation with respect to the body.
>> > So in a 'standard' situation the third link rotates with the second link
>> > so
>> > the angle between those two does not change.
>> > I hope this is a bit clear.
>> > So again is there some solution or workaround?
>> >
>> > Thanks!
>> >
>> > Jeroen
>> >
>> > _______________________________________________
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>> > ros-users at code.ros.org
>> > https://code.ros.org/mailman/listinfo/ros-users
>> >
>> >
>>
>>
>>
>> --
>> Stuart Glaser
>> sglaser -at- willowgarage -dot- com
>> www.willowgarage.com
>> _______________________________________________
>> ros-users mailing list
>> ros-users at code.ros.org
>> https://code.ros.org/mailman/listinfo/ros-users
>
>
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-- 
Stuart Glaser
sglaser -at- willowgarage -dot- com
www.willowgarage.com



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