In the aviation community, there is a high priority to develop all-electric aircraft. Electro-mechanical actuation systems would replace traditional, large, heavy and difficult-to-maintain hydraulic actuation systems. This movement from hydraulic actuation to electrical actuation enhances the flexibility to integrate redundancy and emergency system in future military aircraft. Elimination of the hydraulic fluid removes the possibility of leakage of corrosive hydraulic fluid and the associated fire hazard, as well as environmental concerns. The switch from hydraulic to electrical actuation provides additional benefits in reduced aircraft weight, improved survivability and improved maintainability.
The heat load in an electro-mechanical actuation (EMA) is highly transient and localized in nature; therefore a phase change material could be embedded in the heat generating components to store peak heat load. A comprehensive finite element analysis (FEA) model for the EMA motor has been developed, however the FEA model needs tremendous computational resources. A reduced-order thermal model (lumped node thermal network) is presented, which can reduce computational resources. The network can simulate the temperature time histories of the various components in an EMA electric motor during a flight mission. It is based on a detailed FEA model to locate the hot spots, determine the network parameters, and verify its effectiveness.
The lumped node model is represented by a series of ordinary differential equations and could be numerically solved by standard numerical techniques. It is also combined with an electromagnetic code written in MATLAB to dynamically calculate the temperature of the electric motor. In this paper, details are provided on the mathematical and numerical approaches taken for this integrated modeling effort. FEA results obtained with or without radiation are compared. Radiation is important when cooling effectiveness is insufficient and the motor temperature is high. This paper also demonstrates the temperature response of the EMA with phase change materials (PCM). The PCM is very effective in keeping the motor temperature near the melting point of the PCM until all PCM has melted. Finally, it is shown that the reduced-order model can produce results very similar to those of FEA.