Design, Development and Fabrication of AirdropMechanism for First Aid Kit Drop in Unmanned

Disaster Relief Helicopter

Umair Iqbal⇤, Muhammad Salman Sadiq† and Syed Irtiza Ali Shah⇤⇤Department of Robotics and Artificial Intelligence

School of Mechanical and Manufacturing EngineeringNational University of Sciences and Technology , Islamabad, Pakistan

umair.choudhry@smme.edu.pkirtiza@smme.nust.edu.pk

†Department of Design and ManufacturingSchool of Mechanical and Manufacturing Engineering

National University of Sciences and Technology , Islamabad, Pakistansalman.sadiq@seecs.edu.pk

Abstract—Increasing trend in disasters worldwide has forcedthe use of emerging technology, especially unmanned aerialsystems for disaster surveying and relief operations. Unmannedhelicopters have been used more often for the surveying andrescuing in the disaster struck areas. To provide the element ofrescuing in the unmanned helicopters, in this research paper, asingle piece, servo actuated airdrop mechanism design has beenproposed and fabricated. Proposed airdrop mechanism is capableof carrying 1kg payload of first aid kit to drop in disaster affectedareas. Design has been modelled using the SolidWorks virtualComputer Aided Design (CAD) platform and fabricated using theCNC machine to get the high level of precision. The proposedairdrop mechanism can be utilized in small and medium sizeunmanned aerial systems to drop the payload of 1 kg capacity.

Keywords—Disaster Relief, Unmanned Helicopters, Design andManufacturing and Mechanical Mechanisms.

I. INTRODUCTION

Unmanned Aerial Vehicles (UAVs) are one of the cheapand trending solution for surveying the disaster struck area inreducing the number of mortalities [1]. UAVs provide quickscan of the disaster struck area in the form of in-depth imagesand videos. This aerial view of disaster struck area helps thedisaster management agencies to assess the nature and intensityof damages. Using the helpful information gathered from theUAV, rescue teams are directed to save to the lives. Importanceof first 72 hours after disaster forces the use of quick surveyingtechniques such as using the UAV.

Variety of available aerial platforms are being used in-dividually and in collaboration to make the aerial surveysmore effective. There are five major types of unmanned aerialsystems (UAS), fixed wing [2], rotary wing [3], blimp type,captive balloons and cable driven robots [4], that are beingused in the past for disaster surveying either individually orin combination. A survey about the use of UAV for imagerydata collection in disaster research has also stated the effec-tiveness of using the UAV [5]. In a comparison carried out

between above mentioned aerial systems for disaster searchand rescue applications, rotary wing aerial systems have moreadvantages in disaster search as compared to others and henceare commonly used [6].

For a rotary wing UAS to be more effective in disaster reliefand search operations it must be quipped with high qualityimagery data gathering equipment, autopilot system, longrange control system and other sensory equipment. Usuallyin practice, development of unmanned helicopters for disas-ters has involved the modification of already existing hobbyhelicopters to avoid the extra effort and time. In order to doso, additional mentioned systems have to be implemented onthe model radio controlled (RC) helicopters. Implementationof these additional systems involves the necessary changes inthe helicopter design so that extra space can be created formounting. Also, new mechanical structures have to be designedto mount these systems, such as elevated skid, camera mountand etc [7].

To introduce the part of rescue in the UAVs, it mustcarry a first aid kit containing some high energy biscuits,medicines and high energy soups and drop that kit to certainlocation. To carry and drop the first aid kit, an additionalairdrop mechanism is required to be designed and developedthat can be mounted on UAV to facilitate this operation. Thispaper presents the design and development of such an airdropmechanism developed for the 90 size unmanned helicopter.Detailed design requirements, modelling and fabrication ofthe proposed airdrop mechanism have been presented in thisarticle.

II. DESIGN REQUIREMENTS AND METHODOLOGY

This section describes the basic requirements for the air-drop mechanism and methodology used to implement themechanism. Basic requirements for the airdrop mechanism areweight, space, functionality, vibrations, COG shift, drag forcesand etc. For the utility on 90 size unmanned helicopter listedare the specific requirements for the airdrop mechanism.

3rd International Conference on Engineering and Emerging Technologies (ICEET), Lahore, Pakistan, April 07-08, 2016.

• Overall weight of the airdrop mechanism should notexceed 500g.

• Mechanism should be capable of holding and dropping1kg of payload.

• Mechanism should be with in the space limits heli-copter base to avoid the interaction with skid.

• Mechanism should be designed to minimize the effectof helicopter vibrations during flight.

• Mechanism design should not alter the overall centreof gravity (COG) of the helicopter before of after thedrop.

Basic design manufacturing procedures [8], [9] and flowprocess [10], [11] has been adopted to develop and implementthe desired airdrop mechanism. Fig.1 shows the block diagramfor the standard design and manufacturing process followedfor the development of airdrop mechanism.

III. IMPLEMENTATION OF AIRDROP MECHANISM

This section provides the details about the processes ofparts identification and CAD modelling for implementingairdrop mechanism. Parts identification and CAD modellingare two basic steps before analysis and fabrication.

A. Parts, tools and material identification

Parts, tools and material for the development of airdropmechanism have been identified as a first step in the imple-mentation process. The proposed design for airdrop mech-anism is electronically actuated using the radio controller.To hold and drop the first aid kit, a small servo motor hasbeen selected based on the torque analysis performed on thedesign. Detailed specifications of the servo motor are givenin Table I. For the modelling and detailed study of proposedmechanism, SolidWorks CAD platform has been used. For theprototype developed in this research, aluminium alloy 7071grade material has been used. The material is lightweight,easily available in market and suitable for the manufacturingof aerial mechanisms. Finally, for the fabrication of airdropmechanism, CNC machine has been used to achieve high levelof precision and quality.

TABLE I. SPECIFICATIONS OF SERVO MOTOR. SHOWS THESPECIFICATIONS OF SERVO MOTOR USED FOR THE ACTUATION OF

AIRDROP MECHANISM.

Model Mass Dimensions Torque Operating Voltage(g) (mm) (kgcm) (V)

HS-81 Micro 16.6 30⇥12⇥30 2.6 4.8-6.0

B. CAD Modelling

To facilitate the first aid kit box drop, a reliable andweight optimal airdrop mechanism was required. A singleservo operated, airdrop mechanism has been designed andanalysed using the Solid Works. System has been designedby keeping its aeronautical application in mind. A relativelycomplex system has been designed to ensure the reliability,safety and other factors. To avoid the effect of vibrations, most

Fig. 1. Process Diagram for Manufacturing of Airdrop Mechanism.Shows the overall flow diagram followed for the design, simulation andmanufacturing of airdrop mechanism for first aid kit drop.

of the parts in the airdrop system are single piece parts anduse of joints, welds and screws has been avoided at its most.The components of the airdrop system are shown in Fig.2including releasing pylon, actuation pin and first aid kit box.A string based mechanism has been planned to actuate thepins so that it can drop the box. The designing of first aid kitbox and placement of fuel tank has been done considering theCOG of overall helicopter. The system has been designed sothat, if during the flight box is dropped, the COG of overallhelicopter remains unaffected. Overall assembly of the airdropmechanism along with all its components is shown in Fig.3.

(a) Actuation Pin (b) Releasing Pylon

(c) First Aid Box

Fig. 2. Components of Airdrop Mechanism. Shows the components of the airdrop mechanism proposed for the first aid kit drop. Overall the proposed systemconsists of a releasing pylon, actuation pin and first aid kit .

Fig. 3. CAD Assembly of Airdrop Mechanism. Shows the final assembly of airdrop mechanism with all the parts integrated together. Proposed airdropmechanism will be attached beneath the helicopter and will be capable of holding and releasing the first aid kit box actuated by single servo motor.

IV. TORQUE ANALYSIS FOR AIRDROP MECHANISM

Proposed airdrop mechanism has been tested for thetorque requirements necessary to actuate the drop of first aidkit. The design has been modified and simplified as a resultof these analysis results. Torque analysis has been carried tocheck the capability of motor to hold the load and operate thereleasing mechanism. The basic torque analysis are carriedusing fundamental torque expression and effect of frictionshas been included as the efficiency of mechanism.

There are on total three forces opposing the movement ofactuation pin, force due to friction, force due to spring andforce due to load. Expression to determine the force due tofriction is stated in Equation 1.

F

fric

= µN (1)

Where µ is the surface to surface friction constant and N

is the load of sliding surface. Here in this case aluminiumto aluminium friction constant is 1.35 and load is 0.2 N.As both the left and right actuation pins are identical, thefrictional force of both actuation pins will be same and canbe determined as given in Equation 2.

F

fricL

= F

fricR

= (1.35)(0.2) = 0.27N (2)

Total frictional force for both actuation pins is stated inEquation 3.

F

fric

= F

fricR

+ F

fricL

= 0.27 + 0.27 = 0.54N (3)

To calculate the force due to spring expression in Equation4 has been used. This force opposed the movement of actuationpin due to elasticity of spring. The spring constant for the usedspring is important factor in this mechanism.

F

s

= kx (4)

Where k is the spring constant and the x is the maximumdisplacement of spring. In this case the spring constant is 0.013N/mm and the maximum displacement is 6 mm. As both theleft and right springs are identical, the spring force will besame and is given in Equation 5.

F

s1 = F

s2 = (13Nm

�1)(0.006m) = 0.078N (5)

Total force due to spring is the sum of both spring forcesas given in Equation 6.

F

s

= F

s1 + F

s2 = 0.078 + 0.078 = 0.156N (6)

Force due to 1 kg of load is also kind of frictional force onall four corners of the releasing pylon. The mass of overall firstaid kit will be distributed to all four corners equally. Equation7 shows the force due to payload attached to the releasingpylon.

F

Load

= µN = (0.4)(2.5) = 1N (7)

Total force opposing the movement of actuation pin is sumof all forces determined above and stated in Equation 8.

F

t

= F

fric

+F

s

+F

Load

= 0.54 + 0.156 + 1 = 1.696N (8)

Now as a final step, the required torque can be determinedusing the fundamental torque expression as given in Equation9.

⌧ = r ⇥ F (9)

Here r is the moment arm in this case is around 127 mm.hence the total required torque will be as shown in Equation10.

⌧ = r ⇥ F = (0.127m)(1.696N) = 0.215Nm = 2.192kgcm(10)

The torque of motor specified for this purpose is 3.2kgcm which is higher than the required torque to operate theactuation pin.

V. FABRICATION OF AIRDROP MECHANISM

This section presents the hardware fabrication and man-ufacturing results of the airdrop mechanism for the first aidkit drop. Manufacturing has been carried out using the CNCmachine to ensure the preciseness and quality of final products.Fig.4 shows the fabricated hardware components of airdropmechanism to facilitate the first aid kit drop functionality inthe disaster relief helicopter. Main component in the airdropmechanism is the releasing pylon which is a single piececomponent and hardest fart to manufacture. Sixteen hoursof CNC machine working resulted in the manufacturing ofreleasing pylon which has been then assembled with otherfabricated parts. Actuation pins and the respective springs havebeen attached in the specified positions in the design and metal-lic string based servo actuation mechanism setup has beenconfigured. Fig.5 shows the final assembly of manufacturedairdrop mechanism. The specifications of proposed airdropmechanism in terms of its dimensions, material and the massare given in Table II.

TABLE II. SPECIFICATIONS OF AIRDROP MECHANISM. SHOWS THESPECIFICATIONS OF PROPOSED AIRDROP MECHANISM TO DROP FIRST AID

KIT.

Mass (g) Dimensions (mm) MaterialAirdrop Mechanism 450 248⇥142⇥46 Aluminium 7071

VI. COST ANALYSIS

This section presents the overall cost analysis for thedevelopment of airdrop mechanism. Table III presents thedetails of financial resources spent during the design andfabrication process of airdrop mechanism.

(a) Actuation Pin (b) Releasing Pylon

Fig. 4. Fabricated Hardware Components of Airdrop Mechanism. Shows the final manufactured components of the airdrop mechanism proposed for thefirst aid kit drop. Figures have been taken at aerial robotics lab NUST.

Fig. 5. Fabricated Hardware Assembly of Airdrop Mechanism. Shows the final manufactured assembly of airdrop mechanism with all the parts integratedtogether. Figure has been taken at aerial robotics lab NUST.

TABLE III. COST ANALYSIS OF AIRDROP MECHANISM. SHOWS THEOVERALL EXPENSE FOR THE RESEARCH CARRIED OUT ON DEVELOPMENT

OF AIRDROP MECHANISM FOR DISASTER RELIEF HELICOPTER.

Part Description Purpose PriceAluminum Alloy Block Airdrop Mechanism Design $180

Servo Motor Actuation of Releasing Pins $10Manufacturing Fabrication $120

Others Miscellaneous $10Total $320

VII. CONCLUSION

Air drop mechanism has been modelled and fabricatedsuccessfully to facilitate the first aid kit drop functionality indisaster relief helicopter. Single servo motor actuated mech-anism has been proposed, modelled, tested and fabricatedsuccessfully. Fabricated airdrop mechanism is capable of fa-cilitating the hold and drop of approximately 1 kg first aidkit box. In addition, the design of box is according to itsaerodynamic use and can facilitate the extra fuel tank beneath.Torque analysis shows that the mechanism torque requirementsare under the limits required for the application. Airdropmechanism is slightly heavy with regard to its aerodynamicuse and also complex model causes difficulties in fabrication.Proposed airdrop mechanism model can be used on 90 sizehelicopters for other civilian purposes other than the disasterrelief as well.

VIII. FUTURE WORK

Potential future prospectives for the airdrop mechanism arelisted as follows.

• In flight testing of the airdrop mechanism.

• Design simplifications of airdrop mechanism.

• Fabrication of airdrop mechanism light weight mate-rial to optimize.

ACKNOWLEDGEMENT

I would like to thank NUST main office for the moral andfinancial support in performing the research on developmentof unmanned disaster relief helicopter at Aerial Robotics Lab.In addition, i would like to thank, department of design andmanufacturing, NUST for technical assistance and providingopportunity to utilize manufacturing resources in order tofabricate the airdrop mechanism.

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