Reasons for a parachute: The Safe Drones
Thought the duration of the week, we explored the possibility of having a couple of manual failsafe systems such as parachutes and airbags to complement the failsafe mechanisms already implemented in the drone’s flight control system. There are many scenarios in which a UAV operates erroneously that could result in a crash, and subsequently damage to the machine, be it major or minor:
1. Drone ‘flyaway’ is when a drone travels downwind but needs to travel upwind to return to the operator. Since it faces resistance from the wind, the drone will require additional power from the battery to combat the heavy wind to return to the operator. If the drone is unable to overcome the wind’s force, it will lead to it drifting away from the operator.
2. Software glitches. Sometimes due to a fault in uploading of the drone’s firmware, glitches may occur during flight which may cause the drone to not be able to return to the preassigned home base.
3. Bad GPS data. The operator may have flown into an area which has poor GPS connectivity or if the drone is in an area with a lot of Electromagnetic Field (EMF) interference such as in the proximity of cell towers or transmission towers.
4. Loss of signal to the controller. If the transmitter’s internal circuitry short-circuits, if it runs out of power or if the drone’s receiver is faulty, it may result in a signal loss or ‘garbage’ data being processed by the FCB, which may result in a crash.
5. Low/faulty battery of the drone. This relates to point 1 as well on drone ‘flyaways’ and wind direction and speed.
6. Piloting error. The operator may have accidentally caused the drone to collide with an obstacle which could have damaged the drone’s propellers and hence resulting in a crash.
7. Compass incorrectly calibrated or no calibration done at all. If the drone’s accelerometer and compass are incorrectly calibrated, the flight performance would be impacted heavily.
8. Poor battery mounting. If the battery is poorly secured onto the drone’s frame, it may fall off during flight which will lead to an unbalanced center of gravity or even worse, battery disconnection. It is important to ensure that the power cables are secured tightly by cable ties or some other means.
9. Drone collision during return path. After a failsafe activates, a drone will typically fly in a straight line back to the home point and could collide with obstacles if it does not have any obstacle avoidance algorithm implemented.
10. Operator is unaware of failsafes.
11. Poor weather conditions. A sudden change in weather may cause signal interference, a wet drone, ‘flyaways’ and the drone could be struck by lightning.
These are just a few possibilities, as a combination of these problems could occur as well so it is important to implement a manual failsafe system to protect the drone’s electronics and overall structure.
Leveraging on the parachute idea, further refining of the idea boils down to a core need for a variety of safety mechanisms to be on board certain drones, depending on their operating conditions.
We are aiming to develop a multitude of safety mechanism prototypes which also contribute to the robustness of the drone, such as an airbag which could potentially double up as a buoy to transform the drone into a hovercraft.
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