See a LinMot special linear actuator driven by IONI Pro servo drive. This utilizes the new SinCos encoder support!
Linear motor being used with IONI Pro
Reply
Monthly Archives: April 2015
SinCos encoder support
Last days we have been working on supporting SinCos encoders. SinCos encoder is exactly like standard incremental encoder, except it has sinusoidal analog outputs instead of digital quadrature waveforms.
SinCos encoder signals vs digital incremental encoder signals
The beauty of this is that the analog waveform can provide infinite position resolution when the phase angle of signals are calculated. The latest prototype firmware of IONI Pro now supports SinCos interpolation which increases the resolution that we would get from digital counting by the factor of 16, 64 or 256 times. I.e. a 1000 pulse (or cycle) per revolution analog encoder with 256X interpolation yields resolution equal to 256 000 quadrature pulses per revolution (PPR) or 1 024 000 counts/per revolution (actual position resolution of motor).
SinCos encoder interpolation: the first graph shows position counter in digital mode, the middle shows interpolated angle from sine and cosine signals and the last image shows the combination of these two to form the high resolution position count.
Very high resolution helps especially to make motion smoother, quieter and stiffer. The initial tests show amazing smooth performance of the motor in velocity and position modes. There was no dithering or groaning noise from the motor and at same time the motor position holding stiffness was jaw dropping. It felt like the motor was physically jammed as the eye, hand or ear can’t notice any movement.
CNC router test with IONI Pro
During Easter weekend I was testing IONI on my own DIY CNC router. Steppers ran above 2000 rpm making the machine run faster than it ever has.
IONI has native resolution of 25600 steps/rev (or 128 fold microstepping), which may lead to insufficient step rate from the CNC controller. In my case the LinuxCNC was able to generate only 33 kHz step rate, so step mutliplier in drive has been cranked up to 25x. This normally would reduce microstepping and cause noisy operation, but not with IONI when setpoint smoothing feature is turned on. At 0:32 you will see a comparison between setpoint smoothing off and on.
Special thanks to Aki for video editing!
IONI now measures motor resistance and inductance
IONI drive firmware release 1.1.0 brings a new useful feature that automatically measures motor characteristic resistance and inductance and completely takes the guesswork out of torque controller tuning.
It takes single click to auto-set resistance and inductance
The definition of inductance
Using automatic measure is the new recommended approach to set MR and ML parameters accurately even when motor data sheet would provide these values. This is because many data sheets unfortunately provide inaccurate values. Some manufacturers have apparently characterized motor inductance at high frequency range (hundreds of kHz) which typically gives a value more than 50% off from the real inductance.
Having accurate values also opens doors for sophisticated stepping motor control features such as advanced vibration damping which rely on accurate motor characteristics. This is a subject for another update!
IONIZER – an external power stage board
We have been quietly experimenting on a special IONI motherboard that has discrete power stage to extend IONI power capability. We already have a proof-of-concept board that is equipped with leftover VSD-E mosfets (61A 200V rated). After couple of weeks of use, we could not tell the difference between integrated and external power stage by observing motor control performance and smoothness.
IONIZER proof-of-concept board
Bottom side showing the discrete power MOSFETs
IONIZER has been considered to be available as DIY board (bare PCB) and a reference design where users could modify it to match virtually any power need. However, it’s not ready and many changes are needed to have our approval (such as galvanic isolation of all I/O, short circuit protection and switch to PCI-E 8x socket for newer IONI). Finishing this might be a subject for another crowd funding project.
Some pros are:
- Can be made to virtually any power
- Not highly expensive
And cons:
- If built with assembly errors, can be hazardous
- Some safety & protection features add complexity on circuity (STO, over temperature & short circuit protections)
- Industrial manufacturing may not be cost effective (more complex solution than Argon)
Tell me in the comments how useful do you see IONIZER and which voltage & current range would be your preference :)
Thank you!
The IONI Indiegogo campaign is now finished and has exceeded our most wishful original goals. I can’t figure out a way to express how thankful I am to all the contributors and word-spreaders that made it happen! So thank you!
Our next task is to oviously to fulfill all the shipments :) If you haven’t entered/duplicated your perk order to Granite Devices web shop already, please do it now as instructed in this post. That will help us great deal and will speed up the deliveries.
Contribution over time
Contributions by country
Oh, and happy easter too! :)
Green light (almost)
The prototype IONICUBE 1X has been now assembled and tested. Functionally everything is Ok, which is the most important thing, but few adjustments in layout and component selection will be made. No big deal – no delay!
IONICUBE 1X prototype (with temporary type pin header etc)
In the other news, we’re over $30k in the Indiegogo campaign! Pure awesomeness! This means that the very next IONI firmware release will buff current rating to 18 Amps on devices that are sent for the campaign contributors :)