Steppers & Linear encoders

Well, i think that a component between axis* and stepgen* ist the best solution to integrate the linear-encoder.
Another advantage is that emc can stop on lost steps also cause the stepgen* and axis* are not modified. We'll be still able to use position feedback and fmin_error / fmax_error the same way if've already on my machine. Need some test now to see if such a component makes sense or not...

regards, Thomas

I realise this thread is old but it is "on topic" to what I am starting to look into and didn't want to raise the same topic again if there was undocumented success here.

Thomas - did you ever solve this? I see 2.8 has external oiffsets that could be the answer under latest available capabilities.

Anyone else - if there is a better/newer thread on this use case please just post the link and I'll hop across.

Cheers,
James.

"MetalMusing" has quite a few YouTube videos plus a thread here that I cannot
find ATM...

Any discussion around steppers and encoders should now include smarter drivers like the LAM DS series that have a boost function that allows the current to be increased to the driver as required. Tommy has experimented with enabling this boost feature based on following errors measured via an encoder. However, a more normal use would be to reduce the current when the axis is coasting at speed and not accelerating (which is where the greatest torque requirement occurs). From the modelling we've done, a well matched stepper motor may require a lot lower current than its maximum rating to do a particular job so it all starts to make sense.... So if additional current was boosted when the following error got close to loosing steps, the drive might be able to catch up.

I will be experimenting with this when I get to it. I was thinking of building a component that reduced the current if the velocity was not changing between servo periods. If you have a system designed to work at up to 10 m/min and its only moving at 2m/min, it stands to reason the torque requirements are much reduced so there is a lot of scope to be gentler on the drives.

I use steppers in closed loop with glass scales on my mill with a 7i76E. Works fine.

tommylight wrote:

Rod, are you gona be using encoders?

No I won't. I did buy one to experiment with but good encoders are awfully expensive. I thought a better approach was to enable boost only during acceleration/deceleration via a separate component. In a lot of instances, this would be for only a very short period most of the time so the drive could idle once at cruising velocity . That seemed to be more the way Lam suggested how to use the feature.