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### Author Topic: degrees of freedom...  (Read 1936 times)

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#### kutalinelucas

• Beginner
• Posts: 3
##### degrees of freedom...
« on: January 19, 2012, 06:00:48 PM »
Hey Guys. Just have a quick question, if a robot hand was actuated by 9 motors, one for each base knuckle and then one motor to actuate the medial and distal knuckles on each finger, this makes the device underactuated right? so it would have 9 degrees of actuation, 13 joints, but how many degrees of freedom?

I've found some conflicting stuff...some sources refer to a degree of freedom as the number of independant displacements which provide the kinematic characteristics, but as the medial/distal knuckles engage linearly, the motion of both coupled joints define the hand's characteristics...

So basically...could I present my hand as having 13 degrees of freedom?...sounds much cooler than 9!

Any input would be brilliant

Martyn

#### Elijah5647

• Jr. Member
• Posts: 31
• Mwahaha
##### Re: degrees of freedom...
« Reply #1 on: January 20, 2012, 02:38:31 AM »
I would say that because you can only control 9 different positions then it is only 9 DOF but then again if you can't see how many motors there are than you could easily say that its 13DOF. Its your choice.

Cheers
Elijah

#### kutalinelucas

• Beginner
• Posts: 3
##### Re: degrees of freedom...
« Reply #2 on: January 20, 2012, 04:44:10 AM »
Well its for my Msc robotics thesis which I'm presenting to a bunch of people who really know about this stuff next week...so I should really be sticking to nine then

Thanks for the input

#### Soeren

• Supreme Robot
• Posts: 4,672
##### Re: degrees of freedom...
« Reply #3 on: January 20, 2012, 04:28:27 PM »
Hi,

[...] if a robot hand was actuated by 9 motors, one for each base knuckle and then one motor to actuate the medial and distal knuckles on each finger, this makes the device underactuated right? so it would have 9 degrees of actuation, 13 joints, but how many degrees of freedom?
Assuming a humanoid (i.e. 5 fingers) hand...
"one for each base knuckle" = 5
"one motor to actuate the medial and distal knuckles on each finger" = 5 more

Don't see how you get to 9?

If each finger is more or less parallel, it could be debated whether they actually was only one DoF per joint-"type", i.e. 3 in all.
Regards,
SÃ¸ren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?