After a while of silence, I’m pleased to announce the completion of Argon resolver feedback device support. This means the release of Argon resolver adapter device and a new Argon firmware version 1.3.0 that adds support for it.
Argon resolver adapter fits nicely inside a standard D-sub hood
Adapters are in stock and orderable through web shop at cost of 8.90 eur/pcs. I hope to hear some experiences once first users adopt the new devices!
As are now wiser than during Argon release and we have data about drive reliability, we are confident to start pushing current limits up little by little. To the date, not even one Argon has failed due to overload. We know many users who are pushing them at their power limits and couple of them have even special versions that allows significantly higher currents than the original 10 A continuous / 15 A peak ratings.
The Argon firmware version 1.2.1 has been released to increase current limits to 11 A continuous and 16 A peak. The latest version also addresses issues regarding mechanical brake timing and Hall sensor support. Find full list of changes and download link at Wiki.
As we want to offer motors with pre-made cables that plug directly to the drives eliminating soldering work and chance of wiring error, I made a new poll to ask how long motor cables our followers would prefer.
Cable lenght specification
So please make your vote on the right side of this page or leave a comment to share your thoughts!
More brushless AC servo motors arrived today from a different manufacturer than the previous ones. These ones have premium build quality, high power density (compact size versus power) and reasonable pricing. Such sweet ingredients make a very tasty candidate for our next stocked motor choice.
New motors, 400W and 600W models with brake and 2500 P/R encoders. Encoder cables are pre-made for Argon.
A good thing is, this manufacturer makes wire endings according to our specifications, so they plug direclty to the drive. Out of the box, the first motor was correctly set-up and running in less than 5 minutes. These irons spin silky smooth and quiet as expected.
Servos under the very first test
One of the goals during our SPS IPC DRIVES exhibition visit was to shop for new industrial brushless AC servo motors that eventually would be offered through our web shop separately or as a package with servo drives.
Today we received the first candidates which immediately gave well made and smooth first impression. One positive thing with these motors is the heavy duty connectors counter-parts that come with motors. Obtaining this kind of mating connectors separately usually is time consuming and expensive – it’s not rare to see one of those plugs costing 50 euros from distributors.
New AC servo motors. The smaller ones are 2 Nm and bigger ones 4 Nm 3000 rpm. Both are equipped with 2500 PPR encoders (10 000 counts/rev after 4x decoding).
The new motors offer higher torque & power than the currently offered brushless motor series ranged from 150 W to 660 W power. These new motors output 630 W and 1.3 kW respectively. Anyone wanna buy some for testing? :)
A resolver (stator and rotor part) and an adapter card plugged to Argon
Resolver feedback device will get an official support in the next Argon firmware release. Connecting a resolver to the drive requires few passive components between the feedback device port and actual resolver. These are easily fitted inside the D-sub connector hood and pre-made PCB’s for that will be available for low cost.
A bit oversized plugs on the motor under test?
The main concern using analog feedback device (in which category resolver belongs) is the sensitivity to electromagnetic interference. The following images illustrate the importance of proper cable shielding when using resolver. The upper image without cable shielding/screening shows significant amount of position sensor noise which would cause motor hissing and hunting while standing still. The lower image shows nearly ideal stability. In both cases motor is standing still in torque mode, so all we see here is not real movement but just the sensor noise.
Resolver position counter noise when motor or resolver cable shield is present but not connected to drive. Noise amplitude is over 10 counts out of 8192 per revolution.
The noise when motor or resolver cable shield is connected at drive end. Noise amplitude has reduced to about 1 to 2 counts out of 8192 per revolution.
Random fact of the day: I typically use the most horrible imaginable wiring when developing & testing drives. This serves two purposes: saves time and reveals potential problems early. If it works reliably with bad wiring, then it damn sure will work with a proper wiring.
To demostrate the use of SimpleMotion V2 library with Argon drives, we created a laser projector demo where the angle of two surface mirrors are controlled by two brushless servo motors and Argons.
This was the demo presented also in our SPS IPC DRIVES visit few weeks ago.
Some random project facts:
The source code of Argon servo drive’s STM32F205 ARM Cortex M3 microcontroller has been released under GPL v2 license! What this means to the user is that now he/she can alter servo drive behavior and functionality.
For example, one can implement a pre-programmed motion sequences that are triggered by simple digital input state change (such as push-button interface) or add support for a custom feedback device. It’s also possible to implement highly advanced adaptive control where motor gains are varied depending on external variables.
Block diagram of Argon drive. The I/O side firmware runs on the ARM CPU which connects to all I/O, feedback device and SimpleMotion ports and acts as host/controller for GraniteCore motor control core through isolated communication link.
The source code is downloadable from Granite Devices GitHub page. Users are free to share and commit their changes so eventually everyone could enjoy them out of the box.
Argon firmware package 1.2.0 has been released today featuring a breakthrough in servo bandwidth. This has been achieved by significantly reducing the motor feedback sensor propagation delay from read-out to control algorithm. In practice, this allows tuning higher gain values to the motor and achieve higher servo stiffness. This is especially useful in low inertia systems where machine inertia has low stabilizing effect.
ARGON circuity
For full list of changes and download, visit the Wiki page.
The visit in SPS IPC DRIVES 2013 exhibition at Nuremberg is over and we’re back home now! I believe the visit was well worth the effort. However, as we enrolled to the exhibition bit too late, we got a sub-optimal booth location but regardless of that we got plenty of good feedback and promising contacts.
Tero Kontkanen and Timo Piiroinen at the SPS IPC DRIVES 2013 exhibition
We had small demonstration system on our desk to show some of the capabilities of Argon drive with SimpleMotion V2 bus. The demo is a laser projector where a green laser beam is steered by two mirrors rotated by very fast servo motors. More details, a video and making-of coverage will follow later!
Laser projector demo controlled by Argon drives and SimpleMotion library