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Re: [Paparazzi-devel] Preventing Servos from Cycling at Boot

From: antoine drouin
Subject: Re: [Paparazzi-devel] Preventing Servos from Cycling at Boot
Date: Sat, 21 May 2011 01:35:50 +0200

I mean, as a bad workaround, you can always use one of the hard coded
cases or add yet another hard coded case in servos_4017_hw.c.

But I think we should rather discuss and specify how we want the
autopilot to behave in this case and then make all actuators implement
this behaviour. Wouldn't actuator be a nice candidate for the next
fixedwing/rotorcraft merger ?

Another feature that would be nice to finish adding during this merger
is the option to use several groups of actuators ( think rotorcraft
using I2C or CAN motor controllers + servos for a gimbal camera) or
big vehicle having several CAN servo drivers ( one lisa/M in each wing
and one in the tail ? ). The code generation is already mostly there.
When we stopped working on this feature we were thinking about how to
solve the "different groups want different refresh rate" issue. We had
settled for every group gets refreshed at max rate and groups who want
slower refresh will just prescale values.


On Sat, May 21, 2011 at 12:58 AM, Stephen Dwyer <address@hidden> wrote:
> Hello,
> Is there a possibility simply to put a small R/C or similar switch between
> the servo and the TWOG that can be turned on after initialization and before
> flight? Of course, more weight and complexity.
> Just a thought.
> -Stephen Dwyer
> On Fri, May 20, 2011 at 4:36 PM, antoine drouin <address@hidden> wrote:
>> Hi Luke
>> On the twog, I believe sw/airborne/arch/lpc21/servos_4017_hw.c is used.
>> On initialization, it starts by settings all servo to 1.5ms
>> It has a couple hard coded special cases when  SERVO_MOTOR,
>> outputs the specific SERVO_MOTOR_NEUTRAL etc... values.
>> On stm32 which uses
>> ./sw/airborne/firmwares/rotorcraft/actuators/arch/stm32/actuators_pwm_arch.c
>> , the behaviour is different and I believe servos are not commanded
>> (no PWM is output)  until the autopilot runs and makes the first call
>> to  actuators_commit
>> I'm not sure what the right thing to do is, as actuators are fed with
>> commands produced by the autopilot. There is nevertheless a failsafe
>> value defined for those commands ( it is used on failure of the
>> autopilot process - which only make sense on systems that have a level
>> of protection between the autopilot and fbw processes). Maybe a thing
>> to do would be to command servos using values computed from the
>> failsafe commands, but that would mean those values would have to be
>> computed before the actuators hardware initialization.
>> hth
>> Poine
>> On Sat, May 21, 2011 at 12:11 AM, Luke Ionno <address@hidden> wrote:
>> > Question for everybody...
>> >
>> > I’ve got a TWOG-based airframe with a servo-operated release mechanism;
>> > it’s
>> > a little tricky to reset, and unfortunately, at boot, all the servos
>> > cycle,
>> > causing the release to trigger.  Is there any way to prevent the initial
>> > servo cycling?
>> >
>> > Thanks!
>> >
>> > ~Luke
>> > _______________________________________________
>> > Paparazzi-devel mailing list
>> > address@hidden
>> >
>> >
>> >
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