Currently, if a motor fails during a drone flight, this leads to only three of the usual four rotors working. With only three rotors working, the drone will lose stability and inevitably crash, unless an emergency control strategy sets in. However, researchers at the University of Zurich and the Delft University of Technology have now found a solution to this problem, by using onboard cameras to stabilise the drone and keep it flying autonomously after one rotor suddenly fails.
Davide Scaramuzza, Head of the Robotics & Perception Group at UZH explains:
“When one of the rotors fails, the drone begins to spin itself like a ballerina. This high-speed rotational motion causes standard controllers to fail unless the drone has access to very accurate position measurements.”
This therefore means that once the drone starts spinning, the drone is no longer able to estimate its position in space and eventually crashes. One way to solve this problem is to provide the drone with a reference position through GPS. But there are many places where GPS signals are unavailable. In their study, the researchers solved this issue for the first time without relying on GPS, instead of using visual information from different types of onboard cameras.
Event Cameras Working Well In Low Light
The researchers equipped their quadcopters with two types of cameras: standard ones, which record images serval times per second at a fixed rate, and event cameras, which are based on independent pixels that are only activated when they detect a change in the light that reaches them. The research team developed algorithms that combine information from the two sensors and use it to track the quadcopters position relative to its surroundings. This enables the onboard computer to control the drone as it flies (and spins) with only three rotors. The researchers found that both types of cameras perform well in normal light conditions.
Sihao Sun, a postdoc in Scaramuzza’s lab, said:
“When illumination decreases, however, standard cameras begin to experience motion blur that ultimately disorients the drone and crashes it, whereas event cameras also work well in very low light”.
Increased Safety To Avoid Drone Accidents
The researchers believe that this work can improve quadrotor flight safety in all areas where GPS signal is weak or absent. The problem address by this study is extremely relevant, as with drones becoming increasingly more widespread, rotor failure may cause accidents.
If this work to ever come to fruition, this may be a fantastic way to avoid any drone failure claims within the future.