Hi could you please share step files for the cover? Thx Jiri
One of my concerns with the OpenPPG controller design as well as the other designs suggested in this thread is the lack of dual pots. For safety, electronic automotive accelerator pedals always incorporate two sensors and the engine control unit is constantly comparing both inputs. If they donât match, no power is delivered. I worry about an uncommanded full power event (sticky pot), which would be made worse by the lack of a kill switch.
Andrew
maybe print cogs from nylon, not abs, pa is more wear-resistent
This is not accurate. The controller allows you to disarm and cut power at any pot level at any time with the press of the button. Additionally, the battery has a master power switch on the top.
Hi Zach,
I consider the work you are doing in this space pioneering - huge props. There are some elements of the design, however, that I donât think are truly mature for a product sold to the public, which is the reason that as an engineer and professional pilot (military/airline) I havenât flown my SP140 yet. Kill switch / single throttle pot are two of them.
Respectfully, I donât consider the battery master to be a useful kill switch. I donât know about you, but I canât reach it easily while in the harness. Also, unless youâve changed the logic, a long-press button mash (which you would do in a panic situation) while a throttle input is present sets cruise. Iâll admit that I havenât updated the firmware lately, so apologies if youâve changed that.
A mature design should account for predictable failure modes, one of which is a throttle input signal that doesnât match the pilotâs intent. Pots can and do fail (either electrically or mechanically) and the system should always fail safe. Here is a good video on design of the equivalent system in the automotive world: https://www.youtube.com/watch?v=FOEX6_3kCaM&t=298s. Youâll notice dual input sensors are standard, for good reason (redundancy for safety).
There is also always the potential in any design that the system fails in a way that the designer never could have predicted. In my opinion, murphyâs law makes a true cut-all-current kill switch necessary for safetyâs sake. Disarming, even if made panic-proof, isnât enough in my opinion.
⌠my two cents.
Andrew
Maybe duplicate battery switch, which controls BMS - move it to saddle or shoulder strap, it can be easily mounted with magnetic pogo connector. In case of emergency press button or pull string and disconnect connector
We appreciate the feedback and certainly want to improve reliability. Hall effect sensors are something we are looking into not only for reliability (no moving parts) but also cost. The (industrial grade) linear potentiometer has always been one of the most expensive components in the design.
Not sure if you have flown a gasoline paramotor or a certified single engine plane but those throttle systems are single input as far as I know.
Iâve flown both gas paramotors and piston-powered aircraft. Fully mechanical systems are not usually redundant. In a mechanical system, you can check that the mechanism is operating correctly as a pre-flight item (ensuring that the mechanism operates freely and returns to idle) as well as do a visual inspection of the components if the system is un-cowled, like on a paramotor. Mechanically, this is a true end-to-end check. On a fly-by-wire system, the equivalent check only ensures that the throttle handle is free, which doesnât help if there is an electrical/electronic issue. Redundancy on the electronic side is key, which is why it is standard practice on accelerator pedals in the auto industry. Drones can get away with a lack of redundancy here because people arenât strapped to them.
Additionally, both gas paramotors and aircraft have true âkill switches.â Parajet on the Mav Max actually has redundant kill switches (one on throttle handle and one in frame) that have separate grounding circuits for the ignition. Certified aircraft have three ways to kill the engine from pilot-reachable cockpit controls: mixture, ignition, and fuel shut off. I personally verify that my single, non-redundant kill switch on my gas paramotors (Miniplane and Maverick) works by shutting the engine off and restarting it as a pre-flight item given how critical this control is. I cringe watching out of control throttle videos on paramotors - people usually get seriously hurt.
From other posts, it sounds like youâre working on a next-gen OpenPPG power system. If youâd like input at the design stage, Iâd be happy to offer suggestions. There are several I have in mind for my personal SP140.
I like the way that Jerix was able use a rotary pot and handle-integral spring in his throttle design. This would be a nice add to an SP140 controller in addition to the linear pot. I may fly-wire out some more GPIO pins and do this when I start tinkering with the SP140 again. I already fly-wired out another UART to be able to add communication with the BMS. For now, though, Iâve shelved that project. My wife says the house reno needs to get done before I play with my toys âŚ
Again, great work and I appreciate all you guys are doing. Electric is for sure the future.
Andrew
I wired my sp140 in that way that I have a kill switch for the throttle. If thr would stuck on 100% I can use the switch do disable it, and esc would reset itself to 0% thr.
Thatâs prudent.
A good middle ground that can be implemented in software only would be a bar graph for sensed throttle position that shows on the screen when the controller is un-armed. This way, a pilot could âpre-flightâ test their throttle pot through its full range before arming. This would allow an electric equivalent to the throttle free & return to idle check which all gas pilots should do before starting.
Andrew
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yeah we could do a bar that shows that info pretty easily when disarmed if others want it.
It might not be clear (we need better written documentation) but its not possible to arm the system if it senses more than the smallest amount of throttle input for safety.
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I fly on beaches. As I turned around during a reversed inflation, the throttle was bumped, the RPM went up a bit, nothing drastic. It did not go back to zero after I let go the trigger/potentiometer. A few seconds later, I managed to stop the motor rotations by pulling the throttle lever back to the default position. Somehow, sand found its way inside the handle and jammed the trigger. Murphyâs law and nothing to do with electronics!
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@Voltair - This is a good example of where redundant sensors would be helpful. Both are very unlikely to jam in exactly the same way at the same time. Where did the sand get in: Was it the pivot point of the throttle arm or into the plunger of the potentiometer?
Iâd say you were lucky that the throttle bump was small and that the throttle stayed jammed at a low power setting.
Would you have found a kill switch helpful? My instincts in this situation would be kill motor first, troubleshoot second. Iâd rather not troubleshoot with a spinning prop on my back.
- Andrew
@zjwhitehead Thanks. The bar graph is low hanging fruit.
The sand accumulated at the pivot point of the trigger where the screw goes through the handle. Some of the sand grains managed to find their way on each sides of the lever base creating friction and blocking a full release. Later, I removed the screw and trigger/lever, vacuumed/cleaned the insides of the handle, reassembled it all. I did not want to spray a lubricant thinking it would make things worse with the sand grains sticking to the plastic.
Yes, a cutoff manual switch easily accessible and handed with winter thick gloves (Winter flying) would a great safety feature to have. A simple fat mechanical red ON/OFF switch integrated to the handle could be added without making the housing thicker.
Worse case scenario: a pilot trips during an inflation or the running phase or upon touchdown after a lousy crooked approach. We have a tendency to extend our arms/hands out when falling (reflex). It is likely that the pilotâs fingers will squeeze and create pressure on the trigger/potentiometer bumping up the RPM. I actually have seen that happening a few times. It also happened to me once in the middle of a low turn at about 10â over the beach after experiencing a hard cut off seconds before. Lucky me the motor was off by the time I hit the sand because my hand was clenched into a fist to support my tilted body trying to regain balance. I did not damage my gear and I was 100% ok. When flat on your side or in a tilted position strapped in your gear limiting freedom of movement for a few second, it is possible to have the motor running with you unable to stop it and this is why a cutoff finger switch on the handle as it is with ICE motors would be most welcome. Once I had to physically grab the SP trigger with two fingers and pull it to the default position to stop the motor from rotating.
Hereâs a design idea I made a couple years ago. One of my ICE PPG years back. I was so used to it - right handed - that I had to modified the SP throttle. Thumb kill switch at the top and side LED screen. I have to flip the handle 45 degrees sideways in flight to see the screen but no big deal.
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