This sensor stops your quadcopter before it can cut you
The folks at Spectrum have found a truly cool project for quadcopter pilots. It’s a spinning sensor that will stop the rotors if your finger gets too close to the blades, thereby preventing you – or your kids – from getting cut.
Researchers at the University of Queensland in Brisbane, Australia created so-called Safety Rotor to help prevent accidents with more powerful quadrotor drones. The system constantly senses for a “finger” – in this case a hot dog – and then slams the rotor to a stop within 0.077 seconds. A cage around the propellers spins more slowly than the propellers and is constantly on the lookout for biological material approaching the blades.
The measured latency [of the Safety Rotor’s braking response] was 0.0118 seconds from the triggering event to start of rotor deceleration. The rotor required a further 0.0474 s to come to a complete stop. Ninety percent of the rotational kinetic energy of the rotor (as computed from angular velocity) was dissipated within 0.0216 s of triggering, and 99 percent of the rotational kinetic energy of the rotor was dissipated within 0.032 s.
The safety functionality of the safety system was tested on the bench using a processed meat “finger” proxy to trigger the hoop, and also applied to an open rotor (without hoop) for comparison. The rotor was spun at hover speed (1100 rads−1) and the finger proxy was introduced into the hoop at 0.36 ms−1 … The rotor and finger motion were captured using a shutter speed of 480 Hz. The rotor came to a stop within 0.077 s, with only light marks on the finger proxy from the impact of the hoop. The rotor was completely stopped by the time the finger reached the rotor plane. In contrast, the tip of the finger proxy introduced to an open rotor was completely destroyed.
The kit adds $20 and about 22 grams to the drone so it’s not particularly expensive or difficult to implement. It could be, as they note, a real lifesaver if you tend to put your juicy, blood-filled digits into copter blades.