### Author Topic: new robot calculators!  (Read 5476 times)

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#### Admin

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##### new robot calculators!
« on: October 21, 2007, 03:09:04 PM »
For those who dislike math I've decided to create a new robot calculator page.

I hope to develop these calculators as tools to help answer your questions such as 'what motor is good for my robot?' or 'what battery should I use?'

If you have ideas for a new calculator to do math you don't want to, feel free to suggest it here. And I intend these tools to be useful for the experts too! How about a robot arm torque calculator?

You may now find the robot calculators link on the skills menu on any page (outside the forum).

(To make room for this calculator section, I combined Electronics and Schematics together as one section.)

#### JesseWelling

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##### Re: new robot calculators!
« Reply #1 on: October 23, 2007, 12:00:16 AM »
Nice!  I got really tired of spec'ing out encoder after encoder.
« Last Edit: October 23, 2007, 12:00:53 AM by JesseWelling »

#### creedcradle

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##### Re: new robot calculators!
« Reply #2 on: October 23, 2007, 12:23:38 AM »
Perfect! no need for me to do manual calculations..
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#### bulkhead

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##### Re: new robot calculators!
« Reply #3 on: October 23, 2007, 12:30:28 AM »
A torque calculator for servos/arm lengths would be useful.  It could have the servo's torque rating inputed in either "oz in" or "kg cm" and options for selecting the length of lever arm or the force needed.  Default options could have 'standard' and 'high torque' servo values already inputed.

#### Admin

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##### Re: new robot calculators!
« Reply #4 on: November 12, 2007, 12:59:16 PM »
Just finished up the robot arm calculator.

You no longer need to do the math to put a robot arm on your robot

(I also put a basic encoder feature on it to calculate encoder error of your robot arm)

What I do not have in the calculator is a way to calculate dynamics of the robot arm (acceleration, velocity) and arm sagging. If anyone really needs this, let me know. I figured most people wouldn't need that info, or at least wouldn't know what to do with it . . .

#### Ro-Bot-X

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##### Re: new robot calculators!
« Reply #5 on: November 12, 2007, 02:52:24 PM »
The arm calculator works nice for an arm mouted on a base. But what changes for an arm mouted like a human arm? I mean the base is not vertical and holds the arm up, but horrisontal and holds the arm sideways. Will the calculator work the same way?
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#### Admin

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##### Re: new robot calculators!
« Reply #6 on: November 12, 2007, 03:19:15 PM »
For a horizontal arm motor, its not lifting anything. The torque just needs to counter friction and give proper desired dynamics (rotational acceleration, velocity). If you look at the diagram, the first motor is a horizontal one (the two triangles touching at the tips). I don't even bother having any calculations for it.

Just assume the base motor is where your arm lifts.

Enter your robot arm assuming all joints lift, and just ignore the torque results at the end for the motors that do not lift. If your arm has fewer joints, just set L=0 and weight=0 for that joint/linkage.

Hope that cleared it up . . .

#### Tsukubadaisei

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##### Re: new robot calculators!
« Reply #7 on: November 13, 2007, 04:13:49 AM »
But what if the arm has more then 3 motors??

A.I.(yes those are my initials)

#### Admin

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##### Re: new robot calculators!
« Reply #8 on: November 13, 2007, 05:53:08 AM »
If you have motors to rotate the wrist or open the clamp, you do not need to calculate for that.

You also do not need to calculate torque for motors that cause the arm to translate or rotate about its axis (except for dynamics).

I assume this will cover a good 95% of all arm designs . . . and if anyone fits in that 5%, let me know and Ill expand the program for you

#### Admin

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##### Re: new robot calculators!
« Reply #9 on: December 02, 2007, 11:01:22 AM »
For those who are using the robot arm calculator, I added two new features you will like.

First, I added another DOF that rotates about the Z axis at the arm base. This DOF is not affected by gravity, but still needs to be calculated for velocity of the arm. Of course if your robot arm doesn't have it, you can ignore the results.

Which brings me to my next point. Originally the calculator only handled static forces, meaning if it calculated that your motor needs 3Nm, that means it was the amount of force needed to stop the arm from lifting.

Now however it can also calculate dynamic forces, meaning you can tell the calculator the velocity you want your arm to lift the beer can, and it will give you a much more useful dynamic torque.

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