2011/12/2 andy pugh <[email protected]>:
> On 2 December 2011 17:35, Francesca Sca <[email protected]> wrote:
>
>> Infact I don't want loose a DOF. I would like to find a solution for have in 
>> the joint mode both the rotation of the wirst and the up  and down,  setting 
>> in the right way stepgen and pins. There are this solution? Or I should 
>> create some particular components?
>
> I think that needs a custom HAL component, using comp.
> Part of the problem is that you need to get the feedback back the other way.

Thanks, that sketch was useful, I could not picture the solution, but,
when I saw it, then it was like dooh, so simple...

I think I figured out the solution:
For genserkins:
joint 4 - wrist up/down
joint 5 - wrist rotate
set correct DH parameters for that to happen (disregard both
motors, take into account only kinematics of arms - the joints,
allignement of rotation axes of joints)

Now the joint positions need to be transfered to motor positions.
Make sure to match the direction of positive rotation for both motors
to positive movement of up/down joint, respectively, when both are
moving in positive direction, arm is going up.
Motor 4 is up + rotate
Motor 5 is up - rotate

Or:
Motor.4-cmd = joint.4-cmd + joint.5-cmd
Motor.5-cmd = joint.4-cmd - joint.5-cmd

To get correct feedback value, use last 2 equations and derive
feedback positions:
joint.4-fb = (motor.4-fb + motor.5-fb) / 2
joint.5-fb = (motor.4-fb - motor.5-fb) / 2


I think that this can easily be done with custom HAL component with 4
float inputs (for joint-cmd and motor-fb values) and 4 float outputs
(for motor-cmd and joint-fb).

Viesturs

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