### Author Topic: Torque Calculations... help pls  (Read 652 times)

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#### fantasy_rk89

• Beginner
• Posts: 3
##### Torque Calculations... help pls
« on: March 14, 2013, 10:39:46 PM »
Hey guys

Im new here and i have a big problem. I am supposed to select motors for a walking robot design. specifically i am supposed to select motors for the leg movement namely, hips, knees and ankles. i understand i need to get my torque calculations done for this. but unfortunately im thoroughly a new comer into robotics. can anyone gimme these relations or any headsup over this.

Thanks a lot in advance and just a note, its kinda urgent guys.

#### newInRobotics

• Supreme Robot
• Posts: 1,015
• N.I.R.
##### Re: Torque Calculations... help pls
« Reply #1 on: March 15, 2013, 01:00:43 AM »
Hi

Torque = Force * ArmLength
So if You are looking for knee motor ArmLength is going to be length of thigh.

Force = Mass * Acceleration
Mass is human body mass in this case and Acceleration is how fast You want specific joint to gain velocity.
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

#### fantasy_rk89

• Beginner
• Posts: 3
##### Re: Torque Calculations... help pls
« Reply #2 on: March 15, 2013, 01:17:52 AM »
thanks dude...

but i tried seeing some scholarly articles where they have mentioned very complex equations and some angular considerations for torque calculations...

#### jwatte

• Supreme Robot
• Posts: 1,343
##### Re: Torque Calculations... help pls
« Reply #3 on: March 15, 2013, 12:20:39 PM »
That is correct. To do this engineering the "right way," you need to calculate the statics of the robot to make sure it can stand still, and then add in the dynamics you want, which includes angular momentum, inertia tensors, and other 3D math.

Quote
i am supposed to select motors for the leg movement

It would be interesting to understand what skills you have, and what other skills are available on your team.

If you do not know any mechanics, nor any 3D math, then you're not very well prepared to do what you are supposed to do. So, either learn (which is a significant amount of learning,) or experiment (start with something, make it fail, figure out how to compensate, repeat,) or just ask for a specific recommendation from those who know.
To be able to answer a specific recommendation, we need to know how much the robot will weigh, how long each piece of the leg is, how fast it is supposed to move (in degrees per second) and how quickly it is supposed to be able to react (in degrees per second per second.)

#### fantasy_rk89

• Beginner
• Posts: 3
##### Re: Torque Calculations... help pls
« Reply #4 on: March 15, 2013, 03:19:20 PM »

i do have some engineering background to understand a bit on momentum and stuff. is there any paper or link or anything that describes in detailed about the way to calculate torque from engineering stand point.

also wud u be able to give me the equations or anything like that for these calculations...

what i am supposed to do is calculate the torque required at the joints and based on the torque select motors. and this is an engineering project, so i have to do it the analytical way

#### waltr

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##### Re: Torque Calculations... help pls
« Reply #5 on: March 15, 2013, 06:27:21 PM »
The basics will be there.

Also, there are some articles on torque calculation in the Robot Tutorials part of the web site. Just click the "Robot Tutorials" at the upper left corner of the page.

Then Google will find lots of info.

#### jwatte

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