Eric thanked Richard Beck in topic Backlash for Moonlite? 3 months ago
Richard Beck replied to the topic 'Backlash for Moonlite?' in the forum. 3 months ago

Eric,

First off, thanks for sharing the code and leading me to understanding state machines through our direct messages. This exercise has been valuable to me for more than just the focus controller.

To ensure I eliminated backlash, I increased the backlash value to 96(!). However, I still saw similar results which may be seeing related, although I use 5 second exposures to minimize seeing effects.

I have been using full-field HFR and it works at a reasonable speed on the laptop I have been using. I suppose I may need modify that if I start using a Raspberry Pi at the scope.

Richard

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Chris Guidry thanked Richard Beck in topic DSUSB 3 months ago
Richard Beck replied to the topic 'DSUSB' in the forum. 3 months ago

I mapped the DSUSB to /dev/dsusb using a rule in in /etc/udev/rules.d. I named the file /etc/udev/rules.d/70-dsusb.rules and the contents are

ATTR{idVendor}=="134a" ATTR{idProduct}=="9021" GROUP="users", MODE="0666" SYMLINK+="dsusb"

I stopped using my DSLR some months ago and cannot recall what I put in the shutter release in EKOS. I didn't stop using the DSLR because of INDI. I stopped because I had some strange image artifacts with my D7000 which I couldn't seem to get out with calibration. I'm now working on getting and ASI 1600MM Pro plus filter wheel sorted out so I can image.

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Richard Beck replied to the topic 'Re:Backlash for Moonlite?' in the forum. 4 months ago

I'm still biased that the backlash isn't fully compensated. My goal of having enough engagement for the focuser to not slip outwards seems to have been met. I ran the R, G & B frames through PixInsight's SubframeSelector script and had the most consistent results I've had since the focuser was installed.

For the next night out, I think I'll change the backlash to 100 to improve the meshing of the gears both directions. If the issue on HFR vs focus position the other night is because backlash is non-symmetric, I can't think of how to correct it.

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Richard Beck replied to the topic 'Re:Backlash for Moonlite?' in the forum. 4 months ago

I don't have a screenshot, but I have re-created the v-curves from the logs.



After reviewing all the filters, I may not have enough backlash compensation yet. Thoughts?

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Eric thanked Richard Beck in topic Re:Backlash for Moonlite? 4 months ago
Richard Beck replied to the topic 'Re:Backlash for Moonlite?' in the forum. 4 months ago

I finally got this sorted and have reasonable focus results. There may still be a bit of seeing issues, but, in general, the v-curve looks better than before backlash compensation.

I forked TallFurryMan's firmware and removed the dustcap control as well as implementing backlash compensation. The firmware can be found at https://github.com/beckrd/Moonlite_Focuser .

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Richard Beck replied to the topic 'Re:Backlash for Moonlite?' in the forum. 4 months ago

I now have code that implements the backlash compensation, but I don't get progress information until the scope moves forward.

Here is the code:

        if(TargetPosition > CurrentPosition) 
        {
          Backlash = BACKLASH_FPTN;
          TempPosition = TargetPosition + Backlash;
          stepper.moveTo(TempPosition);      
          while (stepper.targetPosition() != stepper.currentPosition()) stepper.run();
        }
        stepper.moveTo(TargetPosition);

Any suggestions on how to get the position to update while going outward? There will be no feedback moving from all the way in to a defined preset.

Thanks.

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Richard Beck replied to the topic 'Re:Backlash for Moonlite?' in the forum. 4 months ago

Any movement outward, no matter how small, should be compensated with this logic.

For example, I'm using 24 for the backlash plus extra value. A command to move outward 4 ticks would result in unwinding the true backlash and moving outwards by an amount of 28 ticks (24 + 4). After that, the default command outside the if() block would move the focuser inward 24 ticks (unwinding the true backlash and moving the extra included in the 24), leaving the focuser at a true 4 ticks outward.

I am concerned the if() never evaluates as true. I need to see what I can do to confirm it does and the focuser responds as intended. I was thinking increasing the delay to 1000ms might give me a simple chance to see the move past and then the move back in INDI. The alternative would be to include a print that "outward test is true, moving out plus backlash". Your thoughts?

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Eric thanked Richard Beck in topic Re:Backlash for Moonlite? 4 months ago
Richard Beck replied to the topic 'Re:Backlash for Moonlite?' in the forum. 4 months ago

The logic is always focus inward. Even when going to a higher number of ticks, the number of ticks goes up by the backlash, the focuser moves out extra+ y (y is the desired movement outward) ticks, the number of ticks goes down by the backlash and the focuser moves in the extra ticks to leave the focuser at +y with backlash compensated.

In my normal usage, I go to a preset which requires inward focus to get to the minimum. After the minimum is reached, which is defined by drawing in past the minimum, the focuser commands an outward movement. Using your logic, I compensate for the backlash and go out the number of ticks. An unfortunate side effect is the focuser could slip on out the outward backlash. Using my logic, we command the focuser to move as described above and return to the target position.

To move the focuser inwards, the backlash was compensated on the outward movement. Think of this as being equivalent to biasing the RA axis east heavy.

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Richard Beck replied to the topic 'Re:Backlash for Moonlite?' in the forum. 4 months ago

Eric,

I missed any code to correct the position so that given physical tube position is always at the same number of ticks. This is the reason to move out past the target and then back. If backlash is always added to move out, the backlash going inwards must be taken out to have the gears in full contact. If the gears are in full contact, there will be minimal slippage of the focuser outwards. Without the inward backlash taken out, the focuser can slip out up to the amount of backlash. As programmed, I'm moving out dist+actual_backlash+extra and moving back actual_backlash+extra. (Backlash is defined as actual_backlash+extra.)

Since the Uno version seems to be working, I'll take it out the next time I have a chance and will see if it works better than the original version I had. I already like AccelStepper over the simple stepper that was in the other code.

Thanks.

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Richard Beck replied to the topic 'Re:Backlash for Moonlite?' in the forum. 4 months ago

Eric,

I have successfully used your code to step a 5V 28BYJ-48. I have also successfully changed over to using an A4998 stepper driver and a NEMA 17HS13-0404S-PG27 motor.

I wanted to change the backlash logic so that the stepper is always moving inwards to position. To do that, if the new position is outward, I want to step to the new position plus the backlash compensation and then step inwards to the new position. The code I have implemented is

if(CurrentPosition < TargetPosition && 0 < Backlash)
        {
          TempPosition = TargetPosition + Backlash;
          stepper.moveTo(TempPosition);
          delay(100);
        }
       stepper.moveTo(TargetPosition);

I was hoping to see the display go to target + backlash and then to target. It's not showing up in the INDI control panel. When I set debug to "true", I get strange behavior, including nonsensical temperatures.

Any thoughts or suggestions?

Also, I can get the sketch to load and work on an UNO, but it doesn't seem to behave properly when I try to upload to a LEONARDO (with the appropriate changes in build target). Any ideas there?

Thanks.

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Richard Beck replied to the topic 'Re:Backlash for Moonlite?' in the forum. 4 months ago

Eric,

Have you posted your firmware online? I'd like to look at your setup and either move to the same controller or figure out how to implement backlash compensation on the PnP focuser I'm presently using.

Thanks.

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Richard Beck thanked Eric in topic Re:Backlash for Moonlite? 5 months ago
Richard Beck created a new topic ' Backlash for Moonlite?' in the forum. 5 months ago

I have belt-driven DIY focuser which I think has some backlash in the PG27 stepper motor. This is based on the v-curve sort of looking like a V, but returning to a given position seems to not give the same HFR value in the focus module. Is there a way have the focus module go a number of steps beyond the target and move inwards to focus?

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Richard Beck replied to the topic 'Moonlite focus short limit' in the forum. 8 months ago

I'm using Jasem's Ubuntu PPA. The driver information says it's version 1. I can't seem to find any more information about the driver on my system.

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Richard Beck replied to the topic 'Moonlite focus short limit' in the forum. 8 months ago

I just tested my DIY setup and it moved 8000 steps out and in for me using only the moonlight driver and the CCD simulator.

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