[ros-users] Flexible & remote transmission

[Stuart Glaser]

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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>> >
>> >
>>
>>
>>
>> --
>> Stuart Glaser
>> sglaser -at- willowgarage -dot- com
>> www.willowgarage.com
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>
>
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-- 
Stuart Glaser
sglaser -at- willowgarage -dot- com
www.willowgarage.com