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Controlling Firgelli Linear Actuators
http://robotc.net/forums/viewtopic.php?f=41&t=5802
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Author:  gunsilla [ Thu May 02, 2013 12:23 pm ]
Post subject:  Controlling Firgelli Linear Actuators

Hi,

Have built a nxt based robot which among other things have 6 linear actuators, and downloaded the 3rd Party RobotC Drivers to use with it.

Using "firgelli-linearact.h", "mindsensors-motormux.h", "lego-ultrasound.h"

The motormux works perfect. Couldn't find an example of how to use a standard NXT sonar through a motormux but 'USreadDist(S4)' seems to work so hoping that's an ok way to do it?

But the main problem I'm having are the Linear actuators. I can't get the 'ticks' to work. No matter how many ticks i tell it to go it always go all the way in or out and stop by stalling there. I've tried the example programs as well and the same thing happens. Also it stalls _alot_. One actuator is lifting 2 NXT bricks and two motors by itself so is it simply the weight making it stall? Increased the stallcount in firgelli-linearact.h which helps somewhat.

Using RobotC v 3.60 and drivers 3.3.1. Also tried v 3.54 and drivers for 3.54 on another computer with same result.

Appreciate any help you can give me.

Regards,

gunsilla

Author:  mightor [ Fri May 03, 2013 4:18 am ]
Post subject:  Re: Controlling Firgelli Linear Actuators

gunsilla wrote:
The motormux works perfect. Couldn't find an example of how to use a standard NXT sonar through a motormux but 'USreadDist(S4)' seems to work so hoping that's an ok way to do it?

That seems reasonable :)

Quote:
But the main problem I'm having are the Linear actuators. I can't get the 'ticks' to work. No matter how many ticks i tell it to go it always go all the way in or out and stop by stalling there. I've tried the example programs as well and the same thing happens. Also it stalls _alot_. One actuator is lifting 2 NXT bricks and two motors by itself so is it simply the weight making it stall? Increased the stallcount in firgelli-linearact.h which helps somewhat.

The trouble is that I cannot check the issue because my Firgelli LA is a pre-production one and behaves very differently from the production ones. You could just use it as a normal NXT motor. You won't have stall detection but if that doesn't work anyway, there's not much point.

= Xander

Author:  gunsilla [ Fri May 03, 2013 5:42 am ]
Post subject:  Re: Controlling Firgelli Linear Actuators

I've tried using the motorencoders in the standard RobotC way as well like any other motor, but can't get that to work either unfortunatly. Read somewhere here that you have to disable PID - tried that with a command i found on this forum somewhere - but still no luck.

Only way i have of controlling the distance now is by time/ speed in x seconds, which is somewhat inaccurate.

Author:  mightor [ Fri May 03, 2013 8:55 am ]
Post subject:  Re: Controlling Firgelli Linear Actuators

In the Sensor and Motor setup UI, you can untick the PID box:
Attachment:
2013-05-03_14-53-08.png
2013-05-03_14-53-08.png [ 12.35 KiB | Viewed 21540 times ]


That should disable PID for that motor.

= Xander

Author:  gunsilla [ Fri May 03, 2013 9:44 am ]
Post subject:  Re: Controlling Firgelli Linear Actuators

Aha haven't noticed that option. Thanks.

motorencoder commands sill wont work though for the actuators, so looks like i'll have to do without them.

Author:  krexc [ Mon Dec 01, 2014 2:08 pm ]
Post subject:  Re: Controlling Firgelli Linear Actuators

This thread may be long dead but here goes anyway. Using RobotC 4.27 with the accompanying driver suite I had the same problem with the LA on a NXT. Using the sample program 1 it would only go all out or all in. I also found that it would go into never-never land if the actuator was already all in or all out and it was commanded there again. For the latter problem I found that the logic to detect the task ending was resulting in an endless loop. I changed a != to and == in all three motor tasks. In debugging I found that the motor power command was driving the LA in the opposite direction that the target. Result was it would just go all the way to end and stall. Positive power causes LA to extend. Extending causes encoder to decrease. Negative power retracts LA and encoder increases. I changed several logic statements to make target and direction of travel consistent. Finally I changed FLACtretractLA to FLACretractLA just because. The driver file I came up with is attached. I put comments next to each line I changed accept for the subroutine names.

Attachments:
firgelli-linearact_v2.h [12.88 KiB]
Downloaded 811 times

Author:  mightor [ Fri Dec 05, 2014 5:30 am ]
Post subject:  Re: Controlling Firgelli Linear Actuators

Hi Krexc,

Thanks for the fixes. I have not touched this driver in years, as my own LA is actually a prototype and responds very differently to production versions.

= Xander

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