GlassKnees
Well-Known Member
I don't know about other flight controllers, but my APM 2.6 controller/autopilot has a failsafe feature that permits the autopilot to take immediate action when the battery voltage or current drops below a certain threshold that you can set. The action can be to land immediately or return to the launch point (RTL); this permits a safe ending to your flight should you lose track of how long you've been flying.
However, there are some details you should take into consideration: what action should be taken? If the aircraft lands immediately it may not land in a safe spot, or it may be some distance away and you'll have to hike to retrieve your aircraft. If you choose RTL, you must be aware that your aircraft will attempt to rise or descend to its assigned RTL altitude before flying to the landing spot. If your copter has to climb to its assigned altitude and your battery voltage is already low, the increased demand placed on the battery may drop the voltage to near zero and your copter will perform it's rock imitation. This is particularly true if you set the failsafe voltage too low in order to eek out a little more flying time.
So, first decide which action makes sense for your trip out to the field. If you're just going to fly around the playground then "Land" is probably the best action to take. If, on the other hand, you choose RTL, you may want to set the "climb to" altitude to zero, in which case the aircraft will fly to the alunch point at whatever altitude it was at then the action was triggered.
Next, take care not to set your failsafe voltage too low. For a 4S lipo, you will want to set it at around 14.0V, or 83% of it's full charge of 16.8V. For a 3S lipo, 10.5V should be your failsafe value.
Finally, you may go out flying, hit the failsafe, come home and discover that your battery still had plenty of juice left in it. This happened to me until I discovered that I had to calibrate APM voltage reading. The APM monitors battery current/voltage via the APM power module which is connected in line between the battery and the power distribution leads. To do a voltage calibration, you must measure the battery voltage with a multimeter. Then hook up the battery to your aircraft and establish a telemetry link with Mission Planner and see what value is being displayed on the Flight Data Screen. If the voltage isn't the same as what you measured, then go into the Initial Setup screen, select Optional Hardware; there, you will see Battery Monitor where you can change the value. See: http://ardupilot.org/copter/docs/common-using-a-current-sensor.html for details.
I don't know about other FCs. like Naza - I'd like to think that they have similar capabilities.
However, there are some details you should take into consideration: what action should be taken? If the aircraft lands immediately it may not land in a safe spot, or it may be some distance away and you'll have to hike to retrieve your aircraft. If you choose RTL, you must be aware that your aircraft will attempt to rise or descend to its assigned RTL altitude before flying to the landing spot. If your copter has to climb to its assigned altitude and your battery voltage is already low, the increased demand placed on the battery may drop the voltage to near zero and your copter will perform it's rock imitation. This is particularly true if you set the failsafe voltage too low in order to eek out a little more flying time.
So, first decide which action makes sense for your trip out to the field. If you're just going to fly around the playground then "Land" is probably the best action to take. If, on the other hand, you choose RTL, you may want to set the "climb to" altitude to zero, in which case the aircraft will fly to the alunch point at whatever altitude it was at then the action was triggered.
Next, take care not to set your failsafe voltage too low. For a 4S lipo, you will want to set it at around 14.0V, or 83% of it's full charge of 16.8V. For a 3S lipo, 10.5V should be your failsafe value.
Finally, you may go out flying, hit the failsafe, come home and discover that your battery still had plenty of juice left in it. This happened to me until I discovered that I had to calibrate APM voltage reading. The APM monitors battery current/voltage via the APM power module which is connected in line between the battery and the power distribution leads. To do a voltage calibration, you must measure the battery voltage with a multimeter. Then hook up the battery to your aircraft and establish a telemetry link with Mission Planner and see what value is being displayed on the Flight Data Screen. If the voltage isn't the same as what you measured, then go into the Initial Setup screen, select Optional Hardware; there, you will see Battery Monitor where you can change the value. See: http://ardupilot.org/copter/docs/common-using-a-current-sensor.html for details.
I don't know about other FCs. like Naza - I'd like to think that they have similar capabilities.
