Design strategy for geared rotary actuators based on defined mounting and design conditions

Abstract Nowadays the aeronautical industry is transitioning from traditional hydro-mechanical systems to fully electric aircraft architectures, driven by advances in robust, efficient, and reliable electric motor drive technologies. In this shift, geared rotary actuators (GRAs) play a pivotal role as essential components in the new electric architectures, supporting the move toward more sustainable and high-performance aviation solutions. GRAs are essentially compound planetary gear systems with a high gear ratio. They are designed with specific geometry to eliminate the need for the carrier, which allows for higher power density. One of the most common types of GRAs is the center-hinge compound planetary gear set. The main benefits of GRAs include their compact design, the balancing of tangential forces on each planet gear shaft, the reduction of radial forces transmitted from the planet gears to the rings, and a high torque ratio. However, one of the major challenges with these planetary units is planning for mounting the GRA system without interference between different parts. This paper presents a design strategy capable of generating multiple solutions for a GRA, optimizing macro-geometry parameters to meet specific requirements such as target gear ratio, limited space constraints, and defined torque capacity, while also satisfying mounting and design conditions. Additionally, a 2D finite element analysis is used to fine-tune the macro-geometry parameters and provide a more precise assessment of efficiency during meshing. A numerical example illustrates the proposed approach.