Improved Transients in Multiple Frequencies Estimation via Dynamic   Regressor Extension and Mixing
  A problem of performance enhancement for multiple frequencies estimation is studied. First, we consider a basic gradient-based estimation approach with global exponential convergence. Next, we apply dynamic regressor extension and mixing technique to improve transient performance of the basic approach and ensure non-strict monotonicity of estimation errors. Simulation results illustrate benefits of the proposed solution. 
Aranovskiy Stanislav and Bobtsov Alexey and Ortega Romeo and Pyrkin   Anton
cs.SY