4 axis palletized robot arm (robot kinematics) for 3D printing
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Hello guys, I've been able to include the DH parameters directly to the gcode by creating a slicer using grasshopper. But this solution is not pratical in any form. @JoergS5 is it possible to launch a firmware with the DH enabled on the K13 so I can figure the robot directly on the config file? I'm using a cartesian kinematics and tricking the machine with the gcode. Here is a short video of it "building" a cillinder: lRobot kinda working
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@YuriConfessor I will provide an unfinished version on Feb 24/25 for your printer type, which is missing some features like velocity/angle checks. I'll provide a Duet 2 binary for you.
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@JoergS5 Ok, thank you! I'll post here if I have any updates
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Any uppdates on this? Im trying to get inverse kinematics working on the same type of robot.
I might be wrong but this should be a serial scara but when axis 1 moves axis 2 need to follow to keep the relative angle (axis 1 to 2) the same? the relative move should be a 1:1 = just add axis 1 moves to axis 2?
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@Nakcam it's more complicated then serial Scara:
the platform in front stays horizontal, due to the arm's nature: they make movements of a parallelogram, which means some of the arms stay parallel. The calculation is simliar to 5 bar paralleld scara, where two actuators together make a movement which is restricted by the connection at the end point. The inverse kinematics must calculate back with this restriction, with the added problem that there are multiple solutions for the inverse kinematics.
Your image looks fine, but differs from the black robot model: the back arms of his model are fix connected to the platform at the bottom. (looking from back, the left one)
Do you have a prototype, or only the drawing? If you have a working model or prototype, please give me information about how it is built exactly. (which of the arms are connected to the actuators=steppers, which are only connected through hinge, but not driven by the stepper)
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@JoergS5 Thanks for the reply. I have now found the robot 4 axis pelletized section of the duet3d documentation ( duet3d*/User_manual/Machine_configuration/robot_4_axis_palletized), this sould be a perfekt fitt.
I have uploaded the "github*/JoergS5/RepRapFirmware_robot" firmware to the board and run the firmware update. But now im stuck with :M669 K13 B"axisTypes=PRRRp"
currently only CoreXY5AC and CoreXY5BC are supportand it wont take the D values
=== M669 K13 current config ===
numOfAxes 5 axisTypes �������� chain ���������������������������������������� (normal �������������������� special �������������)
axis � ori: -0.00 0.00 0.00 point: -0.00 0.00 0.00 angles min/max/home: -0.00 0.00 0.00
axis � ori: 0.00 0.00 0.00 point: 0.00 0.00 0.00 angles min/max/home: 0.00 0.00 0.00
axis � ori: 0.00 0.00 0.00 point: 0.00 0.00 0.00 angles min/max/home: 0.00 0.00 0.00
axis � ori: 0.00 0.00 0.00 point: 0.00 0.00 0.00 angles min/max/home: 0.00 0.00 0.00
axis � ori: 0.00 0.00 0.00 point: 0.00 0.00 0.00 angles min/max/home: 0.00 0.00 0.00
Screw values:
reference angles/positions: -0.00 0.00 0.00 0.00 0.00
endpoint axis X: -0.00 -0.00 -0.00
endpoint axis Y: -0.00 -0.00 -0.00
endpoint axis Z: -0.00 -0.00 -0.00
endpoint point: -0.00 -0.00 -0.00
abSign: 0 (A/B angle preference: 0 take >=0, 1 take <= 0, 2 don't change calculation
cache used: -1 maximum: 200Mine is the same as yours with one arm fixt to the base (mine is to the right seen from behind)
I do have a fysikal protorype.
config (1).g -
@Nakcam This is a old picture, it does have motors and move. But not with Inverse kinematic
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@Nakcam the kinematics is not implemented yet, but I'll try to do it with your help.
Please confirm or correct me:
- 1 is connected with first actuator/stpper
- 2 is connected with the other
- 3 is connected to base
- 4 is a hinge connecting three parts: tringle low, big arm and other big arm
Your short video looks like the front horizontal platform tilts a bit, the front going a bit down. This may be an optical illustion. But if it's real, then some of the angles are wrong and the construction is not a parallelogram. Maybe you'll need to change the prototype a bit. But let's make the kinematics first.
BTW I like your prototype, because the gear is belt based, which means low or no backlash. The planetary based gears have some play when changing orientation of the rotations.
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@JoergS5 Thanks for helping out! You are correct on how the linkage work (point 1-4). The platform is tilted a bit, but the tilt does not change when moving (it does a tiny bit but that's because of sloop in the system, i did not have all the right fasteners at hand). I am working on a updated version that uses Capstan-Drive system. I would like to get this working first.
here's a fusion 360 link to the cad model
a360.**/42M19T2in using 1.8degree steppers and total gearing is 51,8 (5,18:1+200:20)
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@Nakcam I can work next weekend on it, and it would be nice if you can make some tests with the prototype, verifiying code, while I develop the code. I can provide you the RRF binary for each test.
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@JoergS5 Sounds great! Is there some "hack" to force the D values for now? Or is the robot firmware on github not working?
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@Nakcam the D values make only sense when the axes are calculated in the chain. This is only implemented for CoreXY. I you want to test setting D values in advance, just define your config for CoreXY.
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@JoergS5 Ok. I will wait for your test bin files then. here is some dimensions of my arm
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@Nakcam thank you! I don't have Fusion, so from your image I can make a prototype as well.
Please measure the triangle lenghts as well, from hinge to hinge each.
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@Nakcam here is a short explanation of the parallelograms:
The blue and red ones are connected through the triangle. The triangle is like a curve of the arms from up to down.
The opposite sides of blue, red and green parallelograms shall be parallel each. When they become "flat", i.e. small angles and opposite sides near at each other, the movements and caluclations will become inexact. So this situations should be avoided.
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@JoergS5
Here is a better drawing. Is there som cad format that you prefer? I can export to most of them. would you suggest any changes to the geometry? -
@Nakcam thanks a lot, I hope this is sufficient information for now to start. After the firmware runs, we can discuss improvements if you like. As always it will depend on what you want to do with it whether it's worth to improve precision etc.
This remembers me of that I need a load lifter, maybe I'll build it this this kinematics. Similar to a IRB 760.
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@JoergS5 My plan is to use this robot to reload my resin printer, so the final version should be capable to handle about 1.5kg. it will be mounted on a linear rail. Repetability will be more important than absolut precision.
I do own a cnc mill and the final version might be in aluminium or laser cut plywood. But its 3d printed for now -
I have added a rotational axis nr1 to the base.
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@Nakcam sorry for the delay. I had a family problem, I'll try to proceed.
I want to clearify, please tell me:
My understanding is:
- 1 is the first actuator
- 2 is the second one. Together they define through the parallelogram the blue arm and the lower end position, lower hinge
- 4 (the second arm in back of 1) is unclear for me: is it just to stabilize or has it a movement function?
- 5, 6 and 7 define the upper endpoint in respect to the lower endpoint through parallelism
Is my understanding correct?
Comment in advance to the linear rail where you plan to install it on: this fits perfect into a calculation chain, but you have 4 actuators and 3 degrees of freedom (xyz, orientation always the same). This results in indefinite solutions (you can reach a point with different combinations of linear rail and the 3 actuators), i.e. for a desired position there must be installed a strategy. E.g. if the planned coodination is out of reach, move the linear rail to the middle of the new next work area. This movement should not be in a move, but between moves. I want to make something similar: some (5 or 6) robot arm installed on a linear rail at the wall.
