Researchers in Switzerland and the Netherlands have used event driven image sensors to improve the safety of a multi-rotor autonomous drone.
Once a motor fails, a drone can rotate uncontrollably, making navigation and stabilisation very difficult. Larger drones use GNSS satellite receivers to try to regain control of the system, but this is not practical for smaller aircraft.
“When one rotor fails, the drone begins to spin on itself like a ballerina,” said Davide Scaramuzza, head of the Robotics and Perception Group at UZH and of the Rescue Robotics Grand Challenge at NCCR Robotics, which funded the research. “This high-speed rotational motion causes standard controllers to fail unless the drone has access to very accurate position measurements.”
Instead, the technique developed by the researchers combine data from a standard camera with an event-driven camera sensor that only responds to changes in an image. These event driven, neuromorphic or spiking neural network sensors are being commercialised by companies such as Prophesee in France and Opteran in the UK. The team plans to release the technology as open source.
This is increasingly important with more autonomous drones being used for deliveries that have to operate safely in the event of a failure.
The research team developed algorithms that combine information from the two sensors and use it to track the quadrotor’s position relative to its surroundings. This enables the onboard computer to control the drone as it flies – and spins – with only three rotors.