Use of a MEMS Differential Pressure Sensor to Detect Ground, Ceiling, and Walls on Small Quadrotors

Effective autonomous indoor flight requires an ability to sense and navigate ground, ceiling, and walls. While this can be accomplished in many ways including vision, one bio-inspired approach that is not well studied uses the detection of pressure changes when flying close to surfaces. As an example, an increase in pressure can be detected when a quadrotor flies close to the ground, a phenomenon known as `ground effect'. This work evaluates the viability of differential pressure measurements as a means of sensing ground, ceilings, and walls for small quadrotors. Extending existing models for thrust in ground effect, a model is derived to predict pressure changes due to ground effect in hover and tilt. The pressure response with ground effect is characterized across a range of distances, thrust levels, sensor locations, and quadrotor tilts using a Crazyflie 2.0 quadrotor and a small MEMS differential pressure sensor. Characterization experiments are also used to evaluate pressure measurements at varying distances from ceilings and walls, as well as the pressure behavior due to step changes in ground height. Manually controlled free flight tests are used to validate ground sensing in both nominal and visually challenging environments, as well as wall sensing in free flight.