This paper and presentation will discuss the design of an actuation mechanism to induce the nosecone of a missile to bend away from the centerline while in flight. This feature allows increased mobility for air-to-air missiles as well as a multitude of other benefits for the war fighter. Such a design must also be capable of withstanding significant loading produced by flight conditions. While this particular design has application for a morphing missile there are numerous other applications where high torque transfer at a variety of angles is desired.

The team consists of senior undergraduate mechanical engineering students at the United States Air Force Academy. All seniors are required to complete a two-semester capstone design experience as a culminating event to their undergraduate education. The department finds real-world sponsors for each team to challenge students with a relevant, complex design problem. This particular project is sponsored by the Air Force Research Laboratory (AFRL). It is the second year of a two-year effort. Year one resulted in a preliminary design which this year’s team was tasked to develop fully. The project will culminate in the manufacturing of a prototype for testing at AFRL.

The team’s design is a two-section angled rotary device designed to rotate around a central axis. Drawing inspiration from the F-35B morphing nozzle which was designed to allow short-takeoff and vertical landing, this design allows each section to rotate independent of the other. From this, the design can bend the nose cone of the missile up to +/- 30º in any direction. In addition, the missile can articulate at an angular velocity of great enough magnitude to allow the missile to sweep rapidly back and forth for target acquisition and lock.

The central axis is a driveshaft driven by an electric motor and connected by universal joints at two locations to allow for the change of angle in the mechanism. Directly connected to the driveshaft are two dog clutches located in both sections. Using electric linear actuators, these dog clutches can be moved along the driveshaft to interface with either a strain wave gear to have the section rotate in the same direction as the driveshaft or with a planetary gear system which causes the section to rotate opposite the driveshaft. Because the dog clutch in each section is independently controlled, the sections can rotate opposite each other at the same time, allowing the design to reach a wider range of potential angles in a reduced time. Furthermore, because of the use of gears directly before direct interface with the sections, the torque being transmitted from the motor through the system is significantly less than required by flight loads. Finally, the design contains a control program to dictate the rotation of each section in order to achieve a precisely defined angle.

The presentation will include a thorough analysis of each subsystem as well as the analytical characterization of the entire mechanism. The final design was tested under static and dynamic loading conditions at a variety of deflection angles and loads. The presentation will describe the results of this testing to include the rate of deflection at the prescribed maximum base loading condition and the nominal efficiency of the mechanism. Finally, the presentation outlines the benefits and consequences of a central driveshaft actuated swivel system.


Design and Test of an Articulation Mechanism for a Morphing Missile Nosecone

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

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