Design of a Payload Spin Stabilization System for an All-Rotating Aerial Vehicle

Over the past decade, the aerospace industry has witnessed substantial progress in the field of unmanned aircraft systems. These systems have become lighter and more efficient, as well as more capable of performing complex tasks. A recent example of one such system is the bio inspired AeroSeed aircraft [1]. The developed system offers great advantages in design simplicity and efficiency; however, the unique design also carries some unique challenges related to payload stabilization.

The Aeroseed is an all-rotating rotorcraft developed based on the shape and dynamic behavior of the samara maple seed [1]. It consists of two large “wing” structures that generates lift for the aircraft when the vehicle rotates. The center structure of the aircraft sports two side-mounted motorized propellers that control the rotation rate of the aircraft, therefore controlling the elevation. Higher rotation rates generate more lift, causing the vehicle to climb in elevation, while lower rotation rates decrease the lift generated by the aircraft and its’ elevation. Two servomechanisms join the wings to the center structure of the aircraft and allow for changes in the orientation of the wings that will consequently alter the trajectory of the aircraft.

While this design represents an innovation in the rotorcraft field, the rotation of the entire vehicle does not allow for its use in practical applications such as tracking or imaging. For the design to be practical in terms of pointing a payload such as a camera or sensor, a system that counters the rotation of the aircraft and stabilizes the payload is required.

This paper addresses the design and testing of such a de-spun payload platform. The methodology employed in the design process for this system follows that of a conventional system engineering process starting with the identification of the need. The need, in this case, is to stabilize the payload of an all-rotating aerial vehicle. This is followed by the definition of functional and performance requirements that must be fulfilled in order for the need to be satisfied. The requirements were first utilized to select the electronic components. The structure was then designed around the selected components, with the design going through several iterations as the mass and volume of the system was optimized and new considerations were examined. The resulting structure was manufactured using 3D printing and machining and integrated with selected electronic components to create the final system.

The designed solution consists of a spinning portion and a de-spun portion. The spinning portion is mounted to the aircraft and inherits the rotation of the aircraft. It includes a motor and motor housing tasked with countering the rotation of the Aeroseed aircraft. The de-spun portion provides the mounting surface for the payload (such as a camera and gimbal) as well as the data-collecting and handling electronics that will be responsible for determining the necessary spin rate to stabilize the payload. The payload plate serves as a mounting surface for the desired de-spun payload, an IMU, an Arduino Nano, and a SD card module. The Arduino receives rotational velocity readings of the payload plate from the IMU and calculates the necessary spin rate to stabilize the rotation. A thin shroud extending down from the motor housing protects the electronics on the payload plate. A slider mechanism with two degrees of translational freedom serves as the interface between the system and the aircraft and allow for the alignment of their respective centers of rotation. The final design has a total mass of 589.67 g and a height of 109.1 mm.

References

[1] Ulrich, E. R., Pines, D. J., Park, J., & Gerardi, S. (2013, February 5). United States Patent No. US 8366055 B2. Retrieved from https://patents.google.com/patent/US8366055B2