A Low-Cost, Open-Source, Robotic Airship For Education And .
A Low-Cost, Open-Source, RoboticAirship for Education and ResearchGAL GORJUP, (Student Member, IEEE) AND MINAS LIAROKAPIS, (Senior Member, IEEE)New Dexterity research group, Department of Mechanical Engineering, University of Auckland, New ZealandCorresponding author: Gal Gorjup (e-mail: ggor290@aucklanduni.ac.nz).ABSTRACT Miniature indoor robotic airship platforms offer high mobility, safety, and extended flighttimes. This paper focuses on the feasibility, design, development, and evaluation of such a platform forrobotics education and research. Selected commercially available envelope materials were considered andtested in terms of their helium retention capability and mechanical properties. The obtained envelopeproperties were used in a feasibility study, demonstrating that indoor airships are environmentally andfinancially viable, given an appropriate material choice. The platform’s mechanical design was studiedin terms of gondola placement and rotor angle positioning, resulting in an unconventional, asymmetricarrangement. The developed system was finally tested in a simple path following experiment for proofof-concept purposes, proving its efficiency in attaining the desired heading and altitude configuration. Theproposed robotic airship platform can be used for a variety of education and research oriented applications.Its design is open-source, facilitating replication by others.INDEX TERMS Airship, lighter-than-air, open educational resources, path following, unmanned aerialvehicles.I. INTRODUCTIONIn the golden age of the giant airships, these vehicles hadsurpassed the fixed wing aircraft in terms of flight range,payload, and fuel efficiency. Even though the dream of fillingthe skies with fleets of transport and cargo ships has faded,the advantages of lighter-than-air (LTA) crafts remain. Thesecan be applied in several fields of robotics education andresearch, where miniature robotic devices (both aerial andmobile) are slowly but surely making their appearance, attracting an increased interest.In terms of indoor exploration and navigation, airshipsoffer higher mobility and looser path planning constraintswhen compared to ground robots. Additionally, their field ofview is less obstructed and locomotion issues over differentterrain and obstacles are bypassed completely. Conventionalunmanned aerial vehicles (UAV) that are capable of statichovering in most cases generate lift purely through rotorthrust, which typically drains their battery in under 20 minutes. LTA vehicles, on the other hand, are able to maintain adesired altitude for significantly longer periods of time ona single battery charge [1]. In addition, airship platformsgenerally do not require precise collision control indoors,as their low speed and soft envelope prevent damage tothemselves 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 viablealternative to static or ground-based robots in many applications involving tele-embodiment, monitoring, guidance, andentertainment [2]–[5]. Compared to rotorcraft, airships aresilent and safer due to the absence of sharp, high velocityrotor blades. This allows close proximity interaction andmakes them more attractive to users [6].Despite their promising features, the spread of indoorairship platforms is slow due to the design and controlchallenges they involve. The first task in LTA vehicle designis choosing an appropriate lifting gas. For indoor applications, helium is the default choice because of its nonreactive properties and high lift capabilities. Helium is nonrenewable, making the choice of envelope material criticalwhen considering environmental and financial aspects. Because of the small size of helium molecules, the gas escapesquickly through most conventional films which results in lossof lift over time. For indoor applications, the airship size isalso constrained by standard corridor and doorway widths,limiting their maximum lift and weight of mechanical andelectronic components. Once built, an airship is hard to con1
G. Gorjup et al.: A Low-Cost, Open-Source, Robotic Airship for Education and ResearchFIGURE 1. The proposed low-cost, open-source, indoor robotic airship. The airship consists of a gondola containing all the electronicsand rotors and a Qualatex Microfoil balloon (metallised PET).trol due to its slow response times and nonlinear dynamics.This imposes some very nice problems in terms of controldesign from an educational perspective. Small crafts are alsohighly susceptible to external disturbances, as drafts and airconditioning may greatly influence the airship’s behaviour.This paper focuses on the feasibility, design, and development of an open-source, helium-based, indoor robotic airshipthat can be used for education and research purposes. First,this work focuses on the environmental and financial feasibility of the platform with respect to the helium losses throughdifferent envelope materials. The results offer yearly heliumloss and related cost estimates for a range of commerciallyavailable balloons in an indoor environment. The mechanicalproperties of candidate materials are also evaluated. Then,the paper presents a compact gondola design and exploresthe effects of its placement and rotor angle positioning onflight stability. The efficiency of the final design is experimentally validated via a proof-of-concept path followingexercise that proves its manoeuvring capabilities, while theairship’s motion is being tracked by a Vicon motion capturesystem. Finally, the platform is examined in terms of cost andpossible education and research applications are discussed.The rest of this paper is organised as follows: Section IIintroduces the related work in the field, Section III presentsthe methods used, the analysis conducted, as well as theexperimental setup, Section IV presents the obtained experimental results, Section V examines applications in researchand education, while Section VI concludes the work anddiscusses future directions.II. RELATED WORKWith the spread of intelligent robotic agents, numerousrobotic platforms have been developed and disseminated inan open-source manner to allow replication by others inrobotics education and research [7], [8]. Even though considerable progress has already been made in the field, mostof the related work has focused on ground-based, stationary, or humanlike robotic devices [7], [9]–[11]. While theyare certainly a reasonable choice in many educational andresearch scenarios, such robots are often heavy, expensive,hard to replicate, or have limited mobility.2Such limitations can be overcome by indoor aerial platforms, which have in the recent years received a lot ofattention. The most popular choice of such systems arequadrotors that have been developed as fully autonomousindoor, aerial robotic platforms [12]–[14]. Other studies havefocused on indoor robotic airships. Skye [5] is a sphericalomnidirectional blimp actuated by 4 rotors and equipped witha high resolution camera unit. It was intended for entertainment and interaction in large indoor and outdoor venues asthe platform itself is quite large, with a diameter of 2.7 m.Another entertainment-oriented indoor airship platform is theBlimpduino [15], which features an Arduino-based controlboard that allows communication and basic control through amobile app. The blimpduino came at a very affordable priceof 90 USD, although it is not available for purchase anymoreat the time of writing. A notable example of an autonomousindoor blimp is also the GT-MAB [16], one of the smallestautonomous indoor LTA platforms designed for human-robotinteraction and autonomy studies. In [17], the GT-MAB wasdemonstrated in a human following and gesture recognitionscheme, paving the road for flying airship companions.Some research has also focused on human interaction withrotorcraft, where work was mainly based on one-directionalcommunication through gesture recognition. In [18], the authors presented an agent capable of full-pose person trackingand accepting simple gestural commands. Authors of [19]expanded this concept by developing a gesture-based interface for communicating with teams of quadrotors. In [20], theauthors reversed the information flow and examined the communication of UAV intent to a human user through motion.Regarding rotorcraft, only the visual mode of interaction wasconsidered in human robot interaction research because theseplatforms are generally too loud for auditory communicationand too dangerous for tactile communication. LTA vehicles,on the other hand, can be silent and harmless to the user,provided that an appropriate lifting gas is chosen.The miniaturisation and democratisation of electroniccomponents (access to sophisticated technology has becomemore accessible to more people) has allowed for progressively smaller and more low-cost designs of indoor airships,which have since become relevant for both robotics educationand research. Initial studies have focused mainly on airshipcontrol and navigation, utilising the aerodynamic envelopeshapes of their larger, outdoor airship counterparts. In [21],the authors presented an early indoor blimp system andstudied visual servoing techniques. In [22], a dynamic airshipmodel was developed and successfully applied in an indoortesting environment. Other examples that make use of theclassic blimp envelope shapes include developments in blimpautonomy and navigation as described in [23], [24]. Butall these studies have not focused on the feasibility of therobotic airship platforms, have not examined the permeabilityand applicability of different materials, the yearly heliumlosses, and the projected costs and none of these studies hasproposed an open-source, platform that can be used for bothrobotics education and research.
G. Gorjup et al.: A Low-Cost, Open-Source, Robotic Airship for Education and ResearchFIGURE 2. Evaluated balloons, from left to right: Qualatex untreated round 41 cm latex balloon, Qualatex untreated round 61 cm latex balloon,Qualatex round 61 cm latex balloon treated with UHF, Qualatex round 61 cm Bubble balloon and Qualatex round 91 cm Microfoil balloon.III. METHODSThe lifting gas chosen for the proposed robotic airship platform is helium as it is safe and provides high lifting capacity.An alternative with comparable buoyancy is hydrogen, whichwas immediately discarded due to its high flammabilitycharacteristics. Hot air was also considered, but its liftingpotential is significantly lower than that of the above gases.In addition, the heating element would pose a safety risk,especially for indoor use. Other lifting gas choices are eithertoxic, flammable or offer minimal buoyancy, making theminappropriate for this application.A. ENVELOPE MATERIALBefore designing the gondola, a number of envelope material candidates were examined with respect to their heliumpermeability and mechanical properties. To ensure a low costplatform, the envelope was chosen from the following set ofcommercially available balloons (see Figure 2): Qualatex untreated round 41 cm (16 inch) latex balloon Qualatex untreated round 61 cm (24 inch) latex balloon Qualatex round 61 cm (24 inch) latex balloon treatedwith Ultra Hi-Float (UHF) [25] Qualatex 61 cm (24 inch) clear Bubble balloon (layeredmembrane including a high barrier layer of ethylenevinyl alcohol copolymer) Qualatex round 91 cm (36 inch) Microfoil (metallisedPET) balloonTo evaluate their helium permeability, the balloons’ liftingcapacities, along with their surfaces, were measured dailyover the course of 16 days. Because of their elastic properties, the surfaces of latex and Bubble balloons were determined through their circumferences. The Microfoil balloonsurface was measured before inflation as the material doesnot stretch. After collection, the helium escape rate wascomputed as the flux through the balloon envelope, given by:dQ 1· ,(1)dt Awhere J is the gas flux, Q is the amount of gas escaping, tis time and A is the envelope surface. The obtained heliumescape rates were then averaged and used in a feasibilitystudy projecting expected helium losses through the membrane of an ideal spherical balloon. The approximate costof helium used in the study was based on commerciallyavailable balloon gas tanks.J The mechanical properties of latex, Bubble and Microfoilmaterials were examined in terms of membrane thicknessin the inflated state, membrane area density in the inflatedstate, membrane tensile strength, and membrane elongationcharacteristics. Material samples for latex were taken fromthe Qualatex untreated round 61 cm balloon. For the Microfoil balloon, thickness was measured in the uninflatedstate because the material stretching is negligible duringinflation. As the latex and Bubble balloons stretch duringinflation, their inflated membrane thickness ti was estimatedby assuming constant density of the material:ti tu ·Au,Ai(2)Where tu is the uninflated membrane thickness, Au is theuninflated balloon surface, and Ai is the inflated balloon surface. The area density for all balloons was computed from theuninflated balloon mass and inflated balloon area. Materialtensile strength and elongation were obtained experimentally,in accordance with the ASTM D412-16 Standard [26] forlatex, and ASTM D882-18 Standard [27] for the Bubble andMicrofoil materials. Samples were cut with the Standard DieC, as per ASTM D412-16 for all materials. The strain ratewas 50 mm/min for Microfoil, and 500 mm/min for latex andBubble samples. For each material, five samples were tested.B. GONDOLA DESIGN AND PLACEMENTThe airship gondola was built around the chosen electroniccomponents and actuators. The central control and communication unit is a Raspberry Pi Zero W running a Liteversion of the Raspbian Stretch operating system. Peripheralcomponents include a single cell 500 mAh Li-Ion battery,step-up voltage regulator, motor drivers, three 7x16 mm DCmotors, three 57x20 mm propeller units and a camera modulethat will facilitate the formulation of HRI frameworks. Rotorspeeds can either be controlled by on-board logic or manuallyvia a wireless connection through SSH or an appropriatelydeveloped Robot Operating System (ROS) package [28]. Thecombined cost of the gondola components (excluding the 3Dprinting filament and wiring) comes to 90 USD, which dropsto 54 USD if the camera module is not required. Parametersfor all subsystems of the robotic airship, including component descriptions, product codes, prices, and links to resellerwebpages are collected in a bill of materials available throughthe website listed in Section VI.3
G. Gorjup et al.: A Low-Cost, Open-Source, Robotic Airship for Education and Research(a)(b)FIGURE 5. Centered (a) and angled (b) gondola positioning considered in the flight stability experiments.FIGURE 3. The assembled gondola of the robotic airship. All theelectronics are located inside the gondola body and three rotors areused (see also Figure 4). The gondola is attached to the balloonthrough Velcro pads.FIGURE 6. Side rotor angle configurations, with respect to the gondola axis of symmetry.FIGURE 4. Exploded view of the robotic gondola. The electronics aredepicted at the top of the figure, including the single cell Li-Ion battery.The camera is positioned in an angled configuration on the gondolaand is depicted at the left of the figure. The modular rotor bracketsand airship legs allow for easy replacement and fast modification.The physical frame is 3D printed and built in a modularfashion: the gondola legs and rotor brackets were detachable to facilitate component modification and replacement.The assembled gondola and its exploded view model arepresented in Figures 3 and 4, respectively. The gondola isattached to the chosen envelope using Velcro. The gondolaplacement on the chosen envelope and the rotor angleswith respect to the horizontal axis of gondola symmetrywere determined experimentally to optimise flight stability.Two gondola placement options were considered. The firstplacement was centered and symmetric with respect to theenvelope, in which case the side rotors were horizontal and athird one would in principle be required to control the airshipaltitude (Figure 5a). The second option angled the gondola4with respect to the envelope centre, tilting the airship andshifting its side rotors out of the horizontal plane (Figure5b). In this configuration, the airship orientation and altitudecould be controlled using only the two side rotors. The siderotor angles of 0 , 5 , 10 and 20 were examined in theexperiments. The four evaluated rotor angle configurationsare depicted in Figure 6. The experiments consisted of 10trials for each rotor angle and gondola placement at 25%and 50% of the rotor maximum speed (160 trials in total).The airship was released from a height of 1.5 m. Duringflight, the airship position and rotation were recorded withthe Vicon motion optical capture system, which consists of 8Vicon T-series cameras connected to the Giganet system. TheVicon Tracker software was used to capture the trajectoriesof reflective markers mounted on the airship envelope. Thesystem sampling rate was 100 Hz.C. PROOF-OF-CONCEPT PATH FOLLOWINGThe airship was evaluated in terms of its path following ability in an indoor environment. The angled gondola placement(Figure 5b) with 5 rotor angles was used in the experiments.Path following was implemented using a discrete variation ofthe carrot-chasing algorithm described in [29]. Because thetwo side rotors affected the airship’s altitude in addition toits speed and heading, the algorithm was modified with a Pcontroller that adjusted the baseline rotor speeds dependingon the platform’s current altitude.
G. Gorjup et al.: A Low-Cost, Open-Source, Robotic Airship for Education and ResearchMethod 1 Modified carrot-chasing path following8060Lift [g]Input: (x, y, z), ψ, W0.n [(x0 , y0 ), . . . (xn , yn )], Nt , zt ,Pψ , Pz , Cbase , Cmin , Cmax ,Output: cl , cr1: i argmini kWi (x, y)k2: Wt Wi Nt3: ψd atan2(yt y, xt x)4: C̃base Cbase Pz (zt z)5: cl,r C̃base Pψ (ψd ψ)6: cl,r max(Cmin , min(Cmax , cl,r ))40Latex 41 cmLatex 61 cmLatex 61 cm UHFBubble 61 cmMicrofoil 91 cm2000.0The implemented computational flow of the modifiedcarrot-chasing path following algorithm is presented inMethod 1, where (x, y, z) is the current airship position, ψ isits heading (yaw) angle, W0.n is the desired path segmentedinto a sequence of equidistant waypoints, Nt is the lookahead index, zt is the desired altitude, Pψ and Pz are theheading and altitude gains, Cbase is the default rotor controlsignal and Cmin , Cmax are the minimum and maximumallowed rotor values. The method outputs control signals forthe left and right rotor cl and cr . The proposed airship relieson two rotors for both altitude and heading control for simplicity reasons. This choice imposes certain instability to theplatform. Multiple basic control methods that are typicallyused in undergraduate Engineering courses were examinedand a basic proportional control provided the best results interms of path tracking efficiency and simplicity. Other, moresophisticated methods can also be used, which is a matterof future research from users of the proposed device. Theframework was implemented as a collection of nodes withinthe ROS architecture, which provided the basic communication utilities and allowed for easy debugging. The airship realtime position and orientation were continuously published bya node tracking the airship, which was connected to the Vicondata stream. It ran on a personal computer, along with a noderunning the path following algorithm and publishing the rotorcontrol signals with a rate of 5 Hz. The airship was runninga single node that was receiving the control signals a
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, at-tracting an increased interest. In terms of indoor exploration and navigation, airships
COUNTY Archery Season Firearms Season Muzzleloader Season Lands Open Sept. 13 Sept.20 Sept. 27 Oct. 4 Oct. 11 Oct. 18 Oct. 25 Nov. 1 Nov. 8 Nov. 15 Nov. 22 Jan. 3 Jan. 10 Jan. 17 Jan. 24 Nov. 15 (jJr. Hunt) Nov. 29 Dec. 6 Jan. 10 Dec. 20 Dec. 27 ALLEGANY Open Open Open Open Open Open Open Open Open Open Open Open Open Open Open Open Open Open .
the Source 1 power source until the Source 2 power source does appear. Conversely, if connected to the Source 2 power source and the Source 2 power source fails while the Source 1 power source is still unavailable, the ATS remains connected to the Source 2 power source. ATSs automatically perform the transfer function and include three basic .
Open source software Open source software has been a nebulous reference to any software that is free, and is often confused with freeware and shareware. The Open Source Initiative (OSI; www. opensource.org) has therefore become a certification body for open source software under a commonly agreed-upon definition for "open source".
open source: boundless suite 4.9.1 4 open source: geonode 2.8 5 open source: deegree3 3.3.2 (osgeo-live dvd 11.0) 5 open source: geomajas 2.4.0 (osgeo-live dvd 11.0) 5 installation of open source web gis applications 6 visual model: web gis application features grouped by functionality 6 functionality comparison matrix 7 summary 9
EA 4-1 CHAPTER 4 JOB COSTING 4-1 Define cost pool, cost tracing, cost allocation, and cost-allocation base. Cost pool––a grouping of individual indirect cost items. Cost tracing––the assigning of direct costs to the chosen cost object. Cost allocation––the assigning of indirect costs to the chosen cost object. Cost-alloca
Cost Accounting 1.2 Objectives and Functions of Cost Accounting 1.3 Cost Accounting and Financial Accounting — Comparison 1.3 Application of Cost Accounting 1.5 Advantages of Cost Accounting 1.6 Limitations or Objections Against cost Accounting 1.7 Installation of a costing system 1.7 Concept of Cost 1.9 Cost Centre 1.10 Cost Unit 1.11 Cost .File Size: 1MB
Base: 159 director decision makers for open source adoption and/or cloud strategy in North America. Source: A commissioned study conducted by Forrester Consulting on behalf of Perforce, March 2021. Optimized approach Supporting open source Onboarding open source Migrating existing tools/workloads to open source Comprehensive capabilities
Open Source Used In Open Source Documentation Used in SD-WAN 3.5 2 This document contains licenses and notices for open source software used in this product. With respect to the free/open source software listed in this document, if you have any questions or wish to receive a copy of any source code to which you may be entitled under
