Senior Design Struggles - motors not spinning, please help

I’m designing a drone for a school project with my team. We are running into some issues and feel like they are simple fixes but we would appreciate some help, please. For reference, before any of these issues, we double-checked to make sure roll, pitch, and yaw are mapped correctly and in the correct direction. We also confirmed that all motors were spinning in the correct direction. We calibrated the GPS, accelerometer, and ESCs. We are using Mission Planner and Arducopter. Here’s the sequence of events that followed.

r/Quadcopter - Senior Design Struggles pt 1

Our drone has this layout

  1. We armed our drone, and the motors were not spinning at the same rate. When I changed roll, pitch, and yaw and returned back to normal they looked about the same. As we started to slowly lift off, the drone tilted backward and slightly hit the ground (grass), however, we disarmed right away.
  2. We thought it might be an issue of trim so we changed the trim on the transmitter and that prevented the vehicle from arming. Similarly, we tried changing the trim parameter for each control through Mission Planner, and this still prevented the vehicle from arming, so we changed it back to normal. We continued testing and had the same issue of tilting so we disarmed it before it hit the ground again. We stored it away until we got more time to test it.
  3. A few days later we came back to the drone and armed it and motor 4 (pictured) was not turning at all. We swapped places of the ESC signal pin position with that for motor 2 and motor 2 was spinning fine. We thought its the motor or ESC so we ordered one of each.
  4. This past weekend we wanted to test it in the meantime so we swapped motors 2 and 4, and left the ESCs as they were. We used the motor test function on Mission Planner and all motors were spinning now. Motors 1 and 2 (which was formerly motor 4) were spinning at the same rate which I assigned as 15% throttle. However, motor 3 was spinning faster than 1 and 2, and motor 4 (formerly motor 2) was spinning slower. We tried consulting some on-campus help but no one had a clue as to what was going on. We assumed it was the ESC and waited till our replacement parts arrived to swap it out and do some testing.
  5. It came this morning and we tested the drone to still make sure it was happening, and now motor 4 (formerly motor 2) was not spinning, which led us to think it was the ESC. We probed the PDB and it was reading 11.1 V as expected on the terminals for the ESC that’s not working. We swapped out the ESC on arm 4 for the new one, calibrated the ESCs again, and used the Motor test function again it was STILL not spinning, and the rest of the motors were spinning near the same rate, but with a noticeable difference between each other. We have ordered a Tachometer to track the RPM.

So we have no idea what it could be. In case it helps here is some other information:

  • We are using this kit drone
  • We soldered on the motor leads to the ESC since we didn’t have bullet connectors
  • An issue we realized is that the battery we have is supplying 3S voltage and the minimum is 4S for the motors. We didn’t think this would cause this issue, but don’t know for sure. Another issue that I’m gonna make a separate post about is getting our input voltage of 13.5 (not a battery, its power is drawn from a wall through a series of converters and cables) to 22.2 V for the 6S requirement.

Center the transmitter trims and never change them. Go back to Motor Test in Mission Planner and confirm that the motor order and direction is correct when you press the A-D buttons. Understand which motors should run when you sequence thru these.
A craft that flips on take-off is almost always due to wrong motor order. Next would be wrong Frame Type/class. Post your parameter file.

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Thanks for the quick response. I don’t have the drone in front of me. As soon as I get it back tomorrow morning, I’ll post it. I’ll post some more pictures too.

Also, it seems counterintuitive, but once you are certain of motor order and direction, don’t be too tentative with the takeoff. A dragging skid or frame component wreaks havoc with the control loops. Commit to a takeoff with a smooth, steady throttle increase and get it off the ground.

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03.01.2023-1144.param (15.2 KB)
Please let me know if this is adequate or if I can supply anything else.

OK, most things look OK. But set the Transmitter Yaw trim in the center (all trims actually) and re-run the Radio Calibration. The trim value saved is way off center at 1700us. Also, drop the throttle to minimum before saving the Radio Calibration. It shouldn’t cause a problem but your Trim value is at max.

How did you come up with these?

Then run Motor Test.

That’s right, I changed the motor trim value, I’ll change it back to 1500. I don’t remember changing MOT_PWM_MAX, MOT_PWM_MIN so I think they were like that when we got the FC, but I could be mistaken. Should I change those to 1900 and 1100, respectively?

Also, we tried switching the FC pins for two ESCs and the one that was spinning slow one day, then stopped altogether the next day, was still not spinning so we are trying it out with a different motor. Once it’s reinstalled we’ll make some edits to the parameters.

UPDATE: We switched the motor that wasn’t spinning to a new one, and it was still not spinning when we used the Motor test function. We swapped it’s ESC signal pins in slot 4 with the signal pins in slot 3 and the motor for 3 was spinning and motor 4 was still not, so it can’t be the flight controller, right?

Don’t manually change any of the trim values. These come from Radio Calibration.

1000 and 2000.

What throttle percentage were you using? Set it higher, maybe 15%. The props are off right?

What Flight Controller and ESC’s do you have?

Hi Dave,

I’ve made said changes. However, after some testing and testing extra parts, it turned out to be the ESCs we were using were duds. It came as part of a kit, however, we’ve ordered some more high-quality motors and ESCs and this will hopefully resolve any aforementioned issues. Thanks again for the help.

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