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hi Viktor,
in my experiments i found that a servo's PID control will fail if the force is in the direction of the movement. I guess the hexapod car-simulator is possible with servo's only due to the fact that it is given relatively fast moves; the momentum of the rig+car creates a counter force it has to fight and thus the PID control of the servo works.
With regards,
Reinoud
by
reinoud
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Delta Machines
Hi Viktor,
those stepper motors are awesome; but are they (and the micro-stepper controllers) affordable? It would remove the need for Torsten's pulleys, but lets first get Torsten's machine up and running
With regards,
Reinoud
by
reinoud
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Delta Machines
Dear folks,
as I have been doing some math and analysis around the necessary transformation and Torstens setup, I'll try to answer the questions.
As for the precision: Torstens designs worst case error rate on position will be around 0.19 mm for the combined error vector length of x+y+z and 0.032 for the `sweet spot'. This error rate is for the combined step angle of 0.1125 degrees; the error i
by
reinoud
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Delta Machines
As for that delta-robotics url ... yeah, thats groovy, but at micrometer resolution with piezo elements. *glup* thats not going to be easy.... Isn't that for very small, say upto 1 cm stuff?
by
reinoud
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Delta Machines
Hi jhdgkss,
sorry to disappoint you, but unless you know of a way to disable the PID control in the servo's or try out digital servo's, i fear that that road is blocked for now The problem is that the PID control works fine with a counter force, but when it has a force in the direction of the movement, it starts to overshoot which results in a very resolution shattering motion.
As for the card
by
reinoud
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Delta Machines
Hi Torsten,
well hardware/software co-design and thus also embedded stuff is my field of expertise yeah. I `normally' also do kernel work for NetBSD So i'm quite used to programming 'C' and producing fast algorithms. Challenging for embedded stuff since memory is tight normally ...
The values are Axis positions in steps yes; the value 0 means parallel to the plane the machine is set on. If yo
by
reinoud
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Delta Machines
Hi Torsten,
i think i've cracked the calculation! In my simulation i have a smooth movement from a series of points with the object accelerating and deaccelerating linearly from point to point with the speed/acceleration of the motor movements taken into care. It's still embryonic as it is mostly in float and it still needs to be fitted into the firmware, but just wanted you to hear the good new
by
reinoud
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Delta Machines
hi Torsten,
well as others already mentioned, programming in C++ is not a good thing in embedded systems; too much overhead and most of all memory use. I'd rather transform the project into plain C, without losing the abstraction of course. Would you mind if i did?
As for the firmware design, i think a simplification would be to have the stepper motors only step at designated time deltas; the a
by
reinoud
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Delta Machines
Hiya Torsten,
just looked at your repository in detail; you are quite far already or did you base it on an existing one?
From memory i noticed that:
- the positions are already taken in but nothing is done yet with it
- you have the motor accelerating and deaccelerating code that does nothing yet
- it is based on the Sanguino :-S ... not bad, but i dont have one :-D
So missing is the importan
by
reinoud
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Delta Machines
Oeps, the angles and the block size need to be:
min theta -31.062, max theta 88.4962
block 184 x 184 x 138 fits
I had a bug in my min/max angle code
by
reinoud
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Delta Machines
Dear Torsten,
phew! glad you made the estimation yourself! Nice job btw. I guess that this 19x19x14 is good enough to start with!
Now the tricky part, making smooth movements! Can you please detail the specifics of your setup? i.e. effective stepsize in degrees, aprox. weight of the upper structure (with or without extruder), maximum step speed, some inertia info about your motor and belt? How
by
reinoud
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Delta Machines
Dear folks,
i've figured out the most likely reason for the shakeyness of the downward movements in my model. I think its the PID control that functions fine when its presented a force to combat to but utterly fails when presented a force that's in the way to go causing it to overshoot, correct, overshoot, correct etc... making the movement so very jerky.
With regards,
Reinoud
by
reinoud
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Delta Machines
Hi Torsten, hi folks,
i hope i've converted the values correctly . After some tweaking with the start height of the box it resulted in :
f = 138.564
e = 138.564
rf = 132
re = 168
Base plate servo radius 40
Base plate max radius 172
Height shoulder axis above base plate 72.8288
min theta -31.5975, max theta 56.5319
blo
by
reinoud
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Delta Machines
Dear folks,
as promised, its an article by `mzavatsky' on Trossen robotics.
`energetic', what are your parameters according to this paper? Then i can calculate the build size for you.
With regards,
Reinoud
by
reinoud
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Delta Machines
Dear folks,
i've attached two photo's of my current prototype. I originally designed this prototype to be a poof-of-concept one; to identify the issues i need to address in the 2nd prototype and, if possible, to get some replicated parts
Before i started building i wrote a program to analyze the coordinate transformation and the resulting build volume as parameters of the aspect ratio's of the
by
reinoud
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Delta Machines
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