Motor shutdown on pwm input (parachute release)

ArduCopter Copter 4.0
1

Hi all, we are using an external parachute trigger because the pixhawk did not trigger our chute last time and it resulted in a very expensive crash.

We are using the SATS mini from Fruity Chutes but because this deployment hardware is independent of the PIX we need to shutdown the motors via an external signal from the SATS.

Is there a way I can get a pwm INPUT signal into the pix to do an emergency motor shutdown?

Can I use the AUX connections and change one from an output to input? Is there an easier way?

Thanks all!

2

Yes, any of the PWM input channels can be used for auxiliary switch functions. One of those is Emergency Stop. From the quick start guide for that SATS mini, you probably would want to use the SATS no-delay output channel 1 to trigger the emergency stop in ArduCopter. Then SATS output #2 with its 500ms delay to pop the chute.

https://ardupilot.org/copter/docs/common-auxiliary-functions.html

3

Yes but I have a physical output from the SATS mini which needs to go to an input on pixhawk

Pixhawk uses PPM input so there is no input pins to use

I am hoping I am just having a huge brain fart here and am missing something obvious but I don’t get how I can have an input to the pixhawk pins

Thanks!

4

ah, well that makes it more complicated… This would be a job for one of the DIO pins. Have your SATS output 5v bring a DIO pin high. But there isn’t currently a DIO emergency stop function in ArduPilot that I’m aware of. @rmackay9 is this correct?

5

@Pedals2Paddles is correct that we don’t have a built-in way to disarm the vehicle based on a PWM input besides the regular RC input from the pilot. I wonder if we could write a Lua script to accomplish the same thing, perhaps by reading from an input relay.

If possible I’d like to see the log where the autopilot didn’t deploy the parachute. We suspect there is a race condition that could cause the crash check to trigger before the parachute (issue is here) but we haven’t actually seen this. We should fix it in any case but we’d definitely bump up the priority if this had occurred on a real vehicle. Sorry in advance if this was a factor in the severity of the crash.

6

His issue was the copter free falling, but not tumbling. Without the tumble, the conditions were not met to pop the chute. It was in this thread 23kg quad drone crash

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7

Ah, OK, thanks for that. I’ve added an enhancement request to the issues list to make parachutes deploy if the vehicle loses altitude control even if it manages to maintain attitude control.

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8

Thanks guys, while I am glad that pixhawk does have some sort of fail detection and chute deployment I feel that there is still a requirement to allow users to make use of third party chute deployment and detection.

For us I really like the way the SATS allows you to adjust all the detection parameters and is fully configurable. We actually are using two SATS systems which give us the redundancy our clients are looking for as well.

I am sure that we are not the only clients looking for this.

So yes please do add pwm input somewhere (best would be to make on aux out an aux in) such that the motors can be shut down on high pwm signal.

Thanks all.

Steve

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