Exponential convergence of a nonlinear attitude estimator

A nonlinear attitude estimator is presented. The estimator uses a minimum of two vector measurements and a rate-gyro to estimate the attitude and the rate-gyro bias. The estimator can be implemented using a low-cost inertial measurement unit such as those typically used on inexpensive aerial vehicles. Estimator design is based on an alternate attitude error function that yields an estimator with faster convergence properties than similar estimators previously considered in the literature. A proof of exponential stability about the desired equilibrium point is provided. Simulation and experimental results demonstrate the desirable properties of the proposed estimator.