Improving the Reliability of EMA by using Harmonic Drive Gears

Attention in using electro-mechanical actuators (EMA) in aircraft is increasing. The long-term vision is to replace hydraulic actuation completely and to come to the all-electric aircraft. Several challenges are waiting on this path. The different failure behavior and the limited in-service knowledge are some of them. The paper describes the principle of Harmonic Drive gears and how the application of these will allow to overcome some of these problems. Special focus is made on the discussion of failures and the reason why this gear principle avoids jammed conditions and is easier to be analyzed in reliability calculations.