Shop Forum Makelangelo Polargraph Art Robot REQUEST: Add Polar Coordinate Kinematics for San Drawing “Zen” Robot

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• #28966
Max Webber
Participant

Hey Dan!

I know how busy you are. But I was wondering with all the different Kinematics you include in your firmware. How hard would it be to ad Polar? That would be 2 axis, Radius and Theta.

You could probably just rework SCARA. one less joint.

I’d like to build a Zen Sand Drawing Robot. Think of a round dish of sand and a ball bearing. Underneath the Dish of sand it a Rare Earth magnet. attached to an arm. The arm rotates 360 degrees plus, and the magnet rides along the arm from the center to the outer circle.

Like magic the ball bearing rolls over the sand like a rake in a Zen Garden.

I understand a bit how Cartesian coordinates are converted to Polar. Radius and Theta. But I’m not a programmer and wouldn’t know how to get it in firmware.

I’ve asked Scott who maintains Marlin and they don’t support Polar Coordinates. i was told that Clipper and RepRap Firmware had a branch for Polar but could never find anything from the last few years.

Being that Makelangelo Firmware supports pretty much all 2D kinematics, Adding Polar would complete the set:-)

Just a request.

#28968
Dan
Keymaster

Yeah, it could be done. IK looks something like….

void ik(float *cartesian, float *motorSteps) {
float x = cartesian[0];
float y = cartesian[1];
float angle = atan2(y,x);
float distance = sqrt(sq(x)+sq(y));
motorSteps[0] = angle * STEPS_PER_DEGREE_A;
motorSteps[1] = distance * STEPS_PER_MM_B;
}

Boom.

#28969
Max Webber
Participant

I follow you on IG as well. I’m always amazed at how smart you are. I can follow directions for 3D printing these parts, wiring some electronics even configuring the Arduino sketch. But I don’t think I could do this from scratch!

Bravo, Dan!

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