In the golden age of the giant airships, these vehicles had surpassed the fixed wing aircraft in terms of flight range, payload, and fuel efficiency. Even though the dream of filling the skies with fleets of transport and cargo ships has faded, the advantages of lighter-than-air (LTA) crafts remain. These can be applied in several fields of robotics education and research, where miniature robotic devices (both aerial and mobile) are slowly but surely making their appearance, attracting an increased interest.

In terms of indoor exploration and navigation, airships offer higher mobility and looser path planning constraints when compared to ground robots. Additionally, their field of view is less obstructed and locomotion issues over different terrain and obstacles are bypassed completely. Conventional unmanned aerial vehicles (UAV) that are capable of static hovering in most cases generate lift purely through rotor thrust, which typically drains their battery in under 20 minutes. LTA vehicles, on the other hand, are able to maintain a desired altitude for significantly longer periods of time on a single battery charge [1]. In addition, airship platforms generally do not require precise collision control indoors, as their low speed and soft envelope prevent damage to themselves and their environment.

These attributes render LTA platforms an interesting solution for various robotics education and research applications. Even though their physical interaction capabilities are limited, their higher mobility and lower cost makes them a viable alternative to static or ground-based robots in many applications involving tele-embodiment, monitoring, guidance, and entertainment [2]–[3][4][5]. Compared to rotorcraft, airships are silent and safer due to the absence of sharp, high velocity rotor blades. This allows close proximity interaction and makes them more attractive to users [6].

Despite their promising features, the spread of indoor airship platforms is slow due to the design and control challenges they involve. The first task in LTA vehicle design is choosing an appropriate lifting gas. For indoor applications, helium is the default choice because of its non-reactive properties and high lift capabilities. Helium is non-renewable, making the choice of envelope material critical when considering environmental and financial aspects. Because of the small size of helium molecules, the gas escapes quickly through most conventional films which results in loss of lift over time. For indoor applications, the airship size is also constrained by standard corridor and doorway widths, limiting their maximum lift and weight of mechanical and electronic components. Once built, an airship is hard to control due to its slow response times and nonlinear dynamics. This imposes some very nice problems in terms of control design from an educational perspective. Small crafts are also highly susceptible to external disturbances, as drafts and air conditioning may greatly influence the airship’s behaviour.

This project focuses on the feasibility, design, and development of an open-source, helium-based, indoor robotic airship that can be used for education and research purposes. First, it focuses on the environmental and financial feasibility of the platform with respect to the helium losses through different envelope materials. The results offer yearly helium loss and related cost estimates for a range of commercially available balloons in an indoor environment. The mechanical properties of candidate materials are also evaluated. Then, the project presents a compact gondola design and explores the effects of its placement and rotor angle positioning on flight stability. The efficiency of the final design is experimentally validated via a proof-of-concept path following exercise that proves its manoeuvring capabilities, while the airship’s motion is being tracked by a Vicon motion capture system. Finally, the platform is examined in terms of cost and possible education and research applications are discussed.

References

[1] D. Palossi, A. Gomez, S. Draskovic, A. Marongiu, L. Thiele and L. Benini, "Extending the lifetime of nano-blimps via dynamic motor control", J. Signal Process. Syst., vol. 91, no. 4, pp. 339-361, Mar. 2019.

[2] E. Paulos and J. Canny, "PRoP: Personal roving presence", Proc. CHI, pp. 296-303, 1998.

[3] H. Tobita and T. Kuzi, "Face-to-avatar: Augmented face-to-face communication with aerotop telepresence system", Proc. Int. Work. Conf. Adv. Vis. Interface (AVI), pp. 262-265, 2012, [online] Available: http://dl.acm.org/citation.cfm?id=2254605.

[4] S. Oh, S. Kang, K. Lee, S. Ahn and E. Kim, "Flying display: Autonomous blimp with real-time visual tracking and image projection", Proc. IEEE/RSJ Int. Conf. Intell. Robots Syst., pp. 131-136, Oct. 2006.

[5] M. Burri, L. Gasser, M. Kach, M. Krebs, S. Laube, A. Ledergerber, et al., "Design and control of a spherical omnidirectional blimp", Proc. IEEE/RSJ Int. Conf. Intell. Robots Syst., pp. 1873-1879, Nov. 2013.

[6] C. F. Liew and T. Yairi, "Quadrotor or blimp? Noise and appearance considerations in designing social aerial robot", Proc. 8th ACM/IEEE Int. Conf. Hum.-Robot Interact. (HRI), pp. 183-184, Mar. 2013.