Altitude Estimation and Control of an Insect-Scale Robot with an Onboard Proximity Sensor

Insect-scale micro-air vehicles (MAVs) require careful consideration of the size, weight and power for each component. The inherent instability of the system, exacerbated by the faster dynamics that result from increasing angular accelerations with decreasing scale, requires high bandwidth sensing to maintain stable flight. The Harvard RoboBee is the first MAV under 100 mg to demonstrate controlled flight using external motion capture cameras to measure the position and orientation of the vehicle during flight. Prior research into onboard sensing has demonstrated several sensors that provide sufficiently high-bandwidth and lowlatency feedback to stabilize the attitude of the robot. To achieve autonomous flight, the vehicle needs to sense its attitude, altitude, and either lateral position or velocity. Here we build on previous work by incorporating a sensor that is sizeand powercompatible with insect-scale flight, capable of estimating distance by measuring the time-of-flight of an infrared laser pulse. This sensor has sufficiently low latency to allow the robot to maintain constant altitude over multiple flight experiments. This work on onboard altitude control represents the latest results in achieving autonomous control and visually-guided flight.