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Kinematics of iCub hand

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Kinematics of iCub hand

Giuseppe
Dear all,

I am doing an analysis of the iCub hand, I need to evaluate the position of each fingertip given the 9 joints values, therefore I need the forward kinematics for the whole hand.

On the wiki I can find only the DH parameters for the thumb, index and middle fingers, any idea about where I can fetch the parameters for the ring and pinky fingers?

This is the page I found:
http://wiki.icub.org/wiki/ICubFowardKinematics_hand_left

Many thanks,
Giuseppe
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Re: Kinematics of iCub hand

pattacini

Hi Giuseppe,

 

Find below a table containing the parameters of the ring and the little fingers.

 

We received them from the mech guys some time ago by now and did not integrate yet (in the wiki and in iKin) cause they need to be verified: something like unifying measurement units, defining proper handedness and finally putting them to test.

 

It would be nice to receive your feedback, if you plan to work them out.

 

Cheers,

Ugo

 

 

Ring Finger Transformation Matrix

DH Parameters

0.999816

-0.01912

-0.00167

0.012733

0.0148

0

pi/2

20

0.019124

0.999817

0

8.32621

0.0259

0

0

90

0.001673

-3.2E-05

0.999999

-7.60877

0.022

0

0

90

0.0168

0

-pi/2

90

Little Finger Transformation Matrix

DH Parameters

0.999816

-0.0192

0

-0.42157

0.0148

0

pi/2

20

0.019124

0.996011

-0.08716

23.2755

0.0219

0

0

90

0.001673

0.08714

0.996195

-9.56329

0.019

0

0

90

0.0168

0

-pi/2

90

 

 

 

> -----Original Message-----

> From: Giuseppe [mailto:[hidden email]]

> Sent: 17 August 2014 20:07

> To: [hidden email]

> Subject: [rc-hackers] Kinematics of iCub hand

>

> Dear all,

>

> I am doing an analysis of the iCub hand, I need to evaluate the position of

> each fingertip given the 9 joints values, therefore I need the forward

> kinematics for the whole hand.

>

> On the wiki I can find only the DH parameters for the thumb, index and middle

> fingers, any idea about where I can fetch the parameters for the ring and

> pinky fingers?

>

> This is the page I found:

> http://wiki.icub.org/wiki/ICubFowardKinematics_hand_left

>

> Many thanks,

> Giuseppe

>

>

>

> --

> View this message in context: http://robotcub-

> hackers.2198711.n2.nabble.com/Kinematics-of-iCub-hand-tp7578947.html

> Sent from the RobotCub Hackers mailing list archive at Nabble.com.

>

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Re: Kinematics of iCub hand

Giuseppe
Hi Ugo,

Thank you very much for this.
Actually, I do not plan to implement them directly into some C++ code, but I will definetively let you know how it goes.

Best,
Giuseppe
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Re: Kinematics of iCub hand

Giuseppe
Dear Ugo,

I am digging more into the kinematics at the moment, starting from the website.

I would like to ask you whether the DH parameters (on the website and the one you provieded) are given with respect to the hand reference frame (point in between the middle and ring finger metacarpals) or with respect to the base of the fingers.

Many thanks for your help,
Giuseppe
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Re: Kinematics of iCub hand

pattacini
Hi Giuseppe,

Those DH parameters are given with respect to the hand reference frame, so that starting from the arm end-effector you can reach the fingertips of the thumb, the index and the middle.

Cheers,
Ugo

> -----Original Message-----
> From: Giuseppe [mailto:[hidden email]]
> Sent: 12 September 2014 15:31
> To: [hidden email]
> Subject: Re: [rc-hackers] Kinematics of iCub hand
>
> Dear Ugo,
>
> I am digging more into the kinematics at the moment, starting from the
> website.
>
> I would like to ask you whether the DH parameters (on the website and the one
> you provieded) are given with respect to the hand reference frame (point in
> between the middle and ring finger metacarpals) or with respect to the base
> of the fingers.
>
> Many thanks for your help,
> Giuseppe
>
>
>
> --
> View this message in context: http://robotcub-
> hackers.2198711.n2.nabble.com/Kinematics-of-iCub-hand-tp7578947p7578990.html
> Sent from the RobotCub Hackers mailing list archive at Nabble.com.
>
> -----------------------------------------------------------------------------
> -
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> _______________________________________________
> Robotcub-hackers mailing list
> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/robotcub-hackers

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Re: Kinematics of iCub hand

Giuseppe
Hi Ugo,

Great! Thank you for this.
I will then consider that the <0,0> point is on the metacarpals, as described in [1], and the fingertip positions are expressed having that point as origin.

If this statement is not correct, please let me know.

Best,
Giuseppe

[1] http://wiki.icub.org/wiki/ICubFowardKinematics_right

On 12/09/2014 14:40, pattacini [via RobotCub Hackers] wrote:
Hi Giuseppe,

Those DH parameters are given with respect to the hand reference frame, so that starting from the arm end-effector you can reach the fingertips of the thumb, the index and the middle.

Cheers,
Ugo

> -----Original Message-----
> From: Giuseppe [mailto:[hidden email]]
> Sent: 12 September 2014 15:31
> To: [hidden email]
> Subject: Re: [rc-hackers] Kinematics of iCub hand
>
> Dear Ugo,
>
> I am digging more into the kinematics at the moment, starting from the
> website.
>
> I would like to ask you whether the DH parameters (on the website and the one
> you provieded) are given with respect to the hand reference frame (point in
> between the middle and ring finger metacarpals) or with respect to the base
> of the fingers.
>
> Many thanks for your help,
> Giuseppe
>
>
>
> --
> View this message in context: http://robotcub-
> hackers.2198711.n2.nabble.com/Kinematics-of-iCub-hand-tp7578947p7578990.html
> Sent from the RobotCub Hackers mailing list archive at Nabble.com.
>
> -----------------------------------------------------------------------------
> -
> Want excitement?
> Manually upgrade your production database.
> When you want reliability, choose Perforce Perforce version control.
> Predictably reliable.
> http://pubads.g.doubleclick.net/gampad/clk?id=157508191&iu=/4140/ostg.clktrk
> _______________________________________________
> Robotcub-hackers mailing list
> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/robotcub-hackers

------------------------------------------------------------------------------
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Re: Kinematics of iCub hand

pattacini

If the H0 matrix is the identity I4, you’re right; otherwise, there must be an initial displacement/rotation of the first frame.

Ugo

 

From: Giuseppe [mailto:[hidden email]]
Sent: 12 September 2014 15:51
To: [hidden email]
Subject: Re: [rc-hackers] Kinematics of iCub hand

 

Hi Ugo,

Great! Thank you for this.
I will then consider that the <0,0> point is on the metacarpals, as described in [1], and the fingertip positions are expressed having that point as origin.

If this statement is not correct, please let me know.

Best,
Giuseppe

[1] http://wiki.icub.org/wiki/ICubFowardKinematics_right

On 12/09/2014 14:40, pattacini [via RobotCub Hackers] wrote:

Hi Giuseppe,

Those DH parameters are given with respect to the hand reference frame, so that starting from the arm end-effector you can reach the fingertips of the thumb, the index and the middle.

Cheers,
Ugo


> -----Original Message-----
> From: Giuseppe [mailto:[hidden email]]
> Sent: 12 September 2014 15:31
> To: [hidden email]
> Subject: Re: [rc-hackers] Kinematics of iCub hand
>
> Dear Ugo,
>
> I am digging more into the kinematics at the moment, starting from the
> website.
>
> I would like to ask you whether the DH parameters (on the website and the one
> you provieded) are given with respect to the hand reference frame (point in
> between the middle and ring finger metacarpals) or with respect to the base
> of the fingers.
>
> Many thanks for your help,
> Giuseppe
>
>
>
> --
> View this message in context: http://robotcub-
> hackers.2198711.n2.nabble.com/Kinematics-of-iCub-hand-tp7578947p7578990.html
> Sent from the RobotCub Hackers mailing list archive at Nabble.com.
>
> -----------------------------------------------------------------------------
> -
> Want excitement?
> Manually upgrade your production database.
> When you want reliability, choose Perforce Perforce version control.
> Predictably reliable.
> http://pubads.g.doubleclick.net/gampad/clk?id=157508191&iu=/4140/ostg.clktrk
> _______________________________________________
> Robotcub-hackers mailing list
> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/robotcub-hackers


------------------------------------------------------------------------------
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View this message in context: Re: Kinematics of iCub hand
Sent from the RobotCub Hackers mailing list archive at Nabble.com.


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Re: Kinematics of iCub hand

Giuseppe
Dear Ugo,

I would like to ask you how reliable are the values of the DH parameters of the thumb reported on the wiki (http://wiki.icub.org/wiki/ICubFowardKinematics_hand_right).

Is it possible that right and left thumb parameters are swapped?

Additionally, the table reports 5 links and 4 joints. I have the following questions:
- Which joint (id number) is actively actuated by the dc motor (controllable by robotmotorgui) and which one is passively actuated by the tendons only?
- The two passive joints are moving synergistically as soon as the proximal phalange joint is moving (adduction/abduction joint - not opposition to palm). I assume there is a (linear?) relationship regulationg the motion i.e. if the add/abb joint goes to 20 the other two are 30 and 40 respectively. Do you know the equation of such relationship?
- What does represent the dummy link on the mechanics (i.e. is a distance on the palm?) ?

Many thanks for your help,
Giuseppe
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Re: Kinematics of iCub hand

pattacini
Hi Giuseppe,

I've double checked right now and the parameters of the left and right thumbs seem ok.

Link #0 in table is actuated by a DC motor (joint $8 in robotmotorgui)
Link #2 in table is actuated by a DC motor (joint $9 in robotmotorgui)
Link #3 and #4 in table are actuated by a single DC motor (joint $10 in robotmotorgui)

The static relations are:
   #3 = $10/2;
   #4 = $10/2.

The Link #0 is special in a sense that to comply with DH convention and locate the reference frames correctly downstream the structure we needed to attach a second rigid roto-translation represented by the Link #1 to which no joint is related. Therefore, you're right, the dummy Link #1 only accounts for a distance.

Ciao,
Ugo


> -----Original Message-----
> From: Giuseppe [mailto:[hidden email]]
> Sent: 25 September 2014 18:01
> To: [hidden email]
> Subject: Re: [rc-hackers] Kinematics of iCub hand
>
> Dear Ugo,
>
> I would like to ask you how reliable are the values of the DH parameters of
> the thumb reported on the wiki
> (http://wiki.icub.org/wiki/ICubFowardKinematics_hand_right).
>
> Is it possible that right and left thumb parameters are swapped?
>
> Additionally, the table reports 5 links and 4 joints. I have the following
> questions:
> - Which joint (id number) is actively actuated by the dc motor (controllable
> by robotmotorgui) and which one is passively actuated by the tendons only?
> - The two passive joints are moving synergistically as soon as the proximal
> phalange joint is moving (adduction/abduction joint - not opposition to
> palm). I assume there is a (linear?) relationship regulationg the motion i.e.
> if the add/abb joint goes to 20 the other two are 30 and 40 respectively. Do
> you know the equation of such relationship?
> - What does represent the dummy link on the mechanics (i.e. is a distance on
> the palm?) ?
>
> Many thanks for your help,
> Giuseppe
>
>
>
> --
> View this message in context: http://robotcub-
> hackers.2198711.n2.nabble.com/Kinematics-of-iCub-hand-tp7578947p7579020.html
> Sent from the RobotCub Hackers mailing list archive at Nabble.com.
>
> -----------------------------------------------------------------------------
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