Towards a more efficient quadrotor configuration

The small rotor sizes of quadrotors and multirotors makes them intrinsically less energy efficient than a traditional helicopter with a large single rotor. However, the quadrotor configuration's innate simplicity and inexpensive construction recommends its use in many aerial robotics applications. We present a four-rotor configuration that merges the simplicity of a quadrotor with the energy efficiency of a helicopter, while improving manoeuvering rotor bandwidth. This class of aircraft, called a `Y4' or `triangular quadrotor', consists of a single fixed-pitch main rotor with three smaller rotors on booms that provide both counter-torque and manoeuvering control. Our analysis indicates that a Y4 may provide a 20 per cent reduction in hovering power required, compared with a similarly sized conventional quadrotor. Using a matched pair of quadrotor/triangular quadrotor aircraft, our preliminary experiments show that the test-bed Y4 used 15 per cent less power, without optimisation. We present a dynamic model and demonstrate experimentally that the aircraft can be stabilised in flight with PID control.