Cable Robot using Repetier

Jagi

Hello everyone,

I'm trying to get repetier working with a cable robot like this one https://www.youtube.com/watch?v=xMw1Uj4MwNo, but instead of using 2 motors and 2 counterweights, I want to use 4 motors.

I defined a new DRIVE_SYSTEM and defined the kinematics in motion.cpp.

As it is a nonlinear system, I looked at the definition of the Delta kinematics and expanded it by a fourth motor, so now I have Tower_A, Tower_B, Tower_C and Tower_D.

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#elif DRIVE_SYSTEM == CABLE_ROBOT

a_steps = cartesianPosSteps[X_AXIS];

b_steps = cartesianPosSteps[Y_AXIS];

corePosSteps[A_Tower] = sqrt((a_steps) ^ 2 + (b_steps)²);

corePosSteps[B_Tower] = sqrt((X_MAX_LENGTH - a_steps) ^ 2 + (b_steps) ^ 2);

corePosSteps[C_Tower] = sqrt((a_steps) ^ 2 + (Y_MAX_LENGTH - b_steps) ^ 2);

corePosSteps[D_Tower] = sqrt((X_MAX_LENTH - a_steps) ^ 2 + (Y_MAX_LENGTH - b_steps) ^ 2);

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I already adjusted the defines for the towers, so that it is compiling at this stage.

Now to my questions:

(1) Which other parts of the FW do I need to adapt?

(2) How do I define, which uC Pins will be used for my new Tower_D? Or is there a better way to implement a system with 4 motors?

(3) In repetier.h, I want the FW to recognize the cable robot as a nonlinar system, so I modified the following lines:

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#if DRIVE_SYSTEM==DELTA DRIVE_SYSTEM==TUGA DRIVE_SYSTEM==BIPOD defined(FAST_COREXYZ) defined(CABLE_ROBOT)

#define NONLINEAR_SYSTEM 1

#else

#define NONLINEAR_SYSTEM 0

#endif

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Now I get an error when compiling:" 'xMaxStepsAdj' was not declared in this scope".

From these lines in Printer.cpp:
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#if !NONLINEAR_SYSTEM || defined(FAST_COREXYZ)

int32_t Printer::xMinStepsAdj, Printer::yMinStepsAdj, Printer::zMinStepsAdj; // adjusted to cover extruder/probe offsets

int32_t Printer::xMaxStepsAdj, Printer::yMaxStepsAdj, Printer::zMaxStepsAdj;

#endif

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I assume, that xMaxStepsAdj is only used in a not-nonlinear system. Can you hint me, where I need to look for the error? Is ne NONLINEAR_SYSTEM not set or do I need to change something in printer.cpp?

If I can get this to work, I'll be happy to put it in a state, where it can be implemented in the general FW, so it can be used by others as well.

Thank you for your time and Help!

Jagi

Repetier

You should better optimize parts used several times like
(X_MAX_LENTH - a_steps) ^ 2
by storing them into a temporary variable. These processors are not that fast that we want to add avoidable delays.

Next thing is 4 motor control is a problem since we only have 3 axes for motion plus extruder motor which is always a bit of a special case, but if you have no need for it you could use extruder axis instead.

Adding new systems to V1 firmware is a bit of a pain as there are so many things to consider. A much better solution would be to directly start with V2 firmware. There each motion system consists of an extra .h/.cpp file defining one class and adding a #if case to include the right motion system. So it is much easier to adapt.

What also makes it easier is that it has native support for up to 7 motors. If you look into the dual x printer you see that it uses x,y,z and a motor for the transformation.

Only drawback of V2 is that it requires at the moment a 32 bit due based board like RADDS board. But it makes developing your plotter much easier.

Jagi

Thank you for the answer. Since I want to use Due+RADDS anyway, this will be no Problem. I'll continue with your advice and will report back, when I face problems or have a working solution.

Best Firmware with the best developpers! So nice to have this support :)