Hi,

the diagram above for the math is awsome. Are there a similar diagram for GUS?

Thanks,

Geri

20 posts
• Page **2** of **2** • 1, **2**

Hi,

the diagram above for the math is awsome. Are there a similar diagram for GUS?

Thanks,

Geri

the diagram above for the math is awsome. Are there a similar diagram for GUS?

Thanks,

Geri

- geristockreiter
**Posts:**6**Joined:**Sun Nov 23, 2014 5:08 am

GUS uses the pythagorean theorem. All you have to do is calculate the distance from the effector (x,y,z) to the reference z at a pivot (xp,yp,z_ref). The linear nature of the arms makes it easy.

- Nicholas Seward
**Posts:**738**Joined:**Mon Nov 25, 2013 10:41 pm

I hope that you don't mind the minor threadjacking, but did anyone ever figure out where the dlcj version of Wally's wrist points to? Another way of putting it is where does the line perpendicular to the dlcj point to? I'm trying to figure out where that would put the hotend.

Thanks in advance.

Thanks in advance.

- bloodyshadow13
**Posts:**5**Joined:**Tue Feb 03, 2015 6:17 pm

bloodyshadow13 wrote:I hope that you don't mind the minor threadjacking, but did anyone ever figure out where the dlcj version of Wally's wrist points to? Another way of putting it is where does the line perpendicular to the dlcj point to? I'm trying to figure out where that would put the hotend.

Thanks in advance.

It is not a constant. The wrist stays parallel to the line from elbow to elbow. Fun fun math

- Nicholas Seward
**Posts:**738**Joined:**Mon Nov 25, 2013 10:41 pm

That math is digusting. I think I'll keep the concentric mount unless anyone has a better idea for wally's wrist joint. Has no one tried putting Gus Simpson arms on wally? I'm trying to figure out if it would make the xy simpler maths for slightly more complex construction.

- bloodyshadow13
**Posts:**5**Joined:**Tue Feb 03, 2015 6:17 pm

GUS arms would have super easy math. (Easy means no trig so it is easy to do on old hardware.). That is probably the best plan.

- Nicholas Seward
**Posts:**738**Joined:**Mon Nov 25, 2013 10:41 pm

So my previous post had several significant math errors in it and has been deleted accordingly.

Hopefully this post will have no math errors. If you find any, please point them out.

My idea at some point is to build Bob Wally with a bit of a twist. I'm going back to the DLCJ on the wrist, as well as a DLCJ on each shoulder.

This approach is very one sided, so I have reassigned the variables.

The line between the shoulders is Y=0.

Prime marks designate the far side arm.

A is the arm length.

B is the distance from the shoulder to the wrist joint.

C is the angle between the shoulder line and B.

D is the angle between B and the upper arm.

E is the distance from the elbow to the point(x,0).

F is the angle between the shoulder line and E.

G is the y-height of the elbow.

H is the distance of x (l-x on the far side) plus the x-length of the elbow.

K is the angle between the y axis and the extruder stub arm.

L is the distance between the shoulders.

M is the length of the extruder stub arm.

Xe is the X offset of the extruder.

Ye is the Y offset of the extruder.

derivative, not used

derivative, not used

derivative, not used

derivative, not used

By my count (at 23:00 with work in the morning)

2 square roots, 4 multiplies, 2 addition that we have to do for free to drive the elbows. (B)

4 square roots, 12 multiplies, 2 addition, 2 subtraction (E) also gives us for later use.

2 square roots, 8 multiplies, 2 division, 2 addition, 2 subtraction (G) remember we have already.

2 square roots, 4 multiplies, 2 subtraction (H)

1 square roots, 4 multiplies, 2 division, 2 addition (Xe & Ye) I only did H+Hprime and G^2+H+Hprime once each.

The total damage comes to :

11 square roots, 32 multiplies, 4 division, 8 addition, 6 subtraction

Using the figures in this blog: http://markdow.blogspot.com/2011/06/blink-of-eye-processing-on-arduino.html I calculate that this will take a grand total of 1.12 milliseconds, or 892 operations/second if we use floating point math. Is this fast enough? Or do I need to do all of this in integers to achieve 0.638 milliseconds, or 1,560 operations/second?

Hopefully this post will have no math errors. If you find any, please point them out.

My idea at some point is to build Bob Wally with a bit of a twist. I'm going back to the DLCJ on the wrist, as well as a DLCJ on each shoulder.

This approach is very one sided, so I have reassigned the variables.

The line between the shoulders is Y=0.

Prime marks designate the far side arm.

A is the arm length.

B is the distance from the shoulder to the wrist joint.

C is the angle between the shoulder line and B.

D is the angle between B and the upper arm.

E is the distance from the elbow to the point(x,0).

F is the angle between the shoulder line and E.

G is the y-height of the elbow.

H is the distance of x (l-x on the far side) plus the x-length of the elbow.

K is the angle between the y axis and the extruder stub arm.

L is the distance between the shoulders.

M is the length of the extruder stub arm.

Xe is the X offset of the extruder.

Ye is the Y offset of the extruder.

derivative, not used

derivative, not used

derivative, not used

derivative, not used

By my count (at 23:00 with work in the morning)

2 square roots, 4 multiplies, 2 addition that we have to do for free to drive the elbows. (B)

4 square roots, 12 multiplies, 2 addition, 2 subtraction (E) also gives us for later use.

2 square roots, 8 multiplies, 2 division, 2 addition, 2 subtraction (G) remember we have already.

2 square roots, 4 multiplies, 2 subtraction (H)

1 square roots, 4 multiplies, 2 division, 2 addition (Xe & Ye) I only did H+Hprime and G^2+H+Hprime once each.

The total damage comes to :

11 square roots, 32 multiplies, 4 division, 8 addition, 6 subtraction

Using the figures in this blog: http://markdow.blogspot.com/2011/06/blink-of-eye-processing-on-arduino.html I calculate that this will take a grand total of 1.12 milliseconds, or 892 operations/second if we use floating point math. Is this fast enough? Or do I need to do all of this in integers to achieve 0.638 milliseconds, or 1,560 operations/second?

- bloodyshadow13
**Posts:**5**Joined:**Tue Feb 03, 2015 6:17 pm

Over 1 millisecond for just the kinematics is probably too slow, but you could cheat (ie: do what the existing AVR delta firmwares do: run 100-200 kinematics calculations/s and linearly interpolate in between).

But I'd just recommend getting a faster CPU. If you don't want to jump to something as complex as Linux and a BeagleBone or x86 system running Machinekit (what I'm using), get one of the Cortex-M boards (Smoothie, Azteeg x5, R2C2, etc). Then you can (mostly) just write code, without having to carve out spare cycles from _somewhere_ to get it to run.

But I'd just recommend getting a faster CPU. If you don't want to jump to something as complex as Linux and a BeagleBone or x86 system running Machinekit (what I'm using), get one of the Cortex-M boards (Smoothie, Azteeg x5, R2C2, etc). Then you can (mostly) just write code, without having to carve out spare cycles from _somewhere_ to get it to run.

- cdsteinkuehler
**Posts:**74**Joined:**Tue Nov 26, 2013 1:53 am

Hello!

Is it possible to control a wally with LinuxCNC without going through a BEAGLEBONE, installing the Wallykins.c kinematics with sudo comp --install wallykins.c ?

Is it possible to control a wally with LinuxCNC without going through a BEAGLEBONE, installing the Wallykins.c kinematics with sudo comp --install wallykins.c ?

- Doglo
**Posts:**1**Joined:**Fri Mar 20, 2015 4:29 pm

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