Quadcopter Attitude Estimation using Multiple Ultrasonic Rangefinders and Rate Gyroscopes

To maintain stable flight, quadcopters require data output from sensors to be able to accurately determine flight states. Traditionally, quadcopters utilized data provided from Global Positioning System to rectify errors associated with integrating Inertial Measurement Unit measurements. Unfortunately, quadcopters often encounter situations where the Global Positioning System is unavailable thus another method must be used. Current methods utilizing laser scanners have been shown to be effective but are significant in cost. This work explores the use of four low-cost ultrasonic range finders placed on each arm of the quadcopter to provide consistent error correction. Multiple methods of calculating attitude were explored and simulated across multiple flight paths with data from rate gyroscopes, accelerometers, and ultrasonic range sensors. Ultimately this approach resulted in a less than 0.25° root mean square error for roll and pitch angles across all considered flight scenarios thus demonstrating its viability for attitude estimation purposes.