Parallel hybrid propulsion system with integration of designed electric machine for medium altitude long endurance UAV

Abstract

Unmanned Aerial Vehicles (UAVs) are commonly used in several areas such as military and civilian applications and are getting popular day by day. They have classifications based on their range, total mass and altitude. According to their classification, they have different topologies about propulsion systems. Especially beyond Middle Altitude Long Endurance (MALE) class, they have conventional propulsion systems which is powered by internal combustion engines (ICEs). Nevertheless, the low efficiency rate and detrimental environmental impact of these propulsion systems have prompted the search for more efficient and environmentally friendly propulsion components. Electrical machines are regarded as a promising alternative for powertrain applications, given their high efficiency rate and environmentally friendly characteristics. Prototypes and operational applications have been observed in other transportation vehicles, further substantiating their potential. There are different topologies for hybrid and full electric propulsion systems, but they should be considered with respect of operational requirements of UAVs. Long endurance and range are required especially for MALE class UAVs, and it couldn't achieve with full electric propulsion models because of current battery technology. To address this issue, hybrid propulsion systems represent a promising avenue for resolution. In this study, the MALE class UAV, which is currently in use in the field, has been selected as a case study for the implementation of a hybrid propulsion system. This is because there is currently no known application of hybrid propulsion in this UAV model, which is equipped with an ICE. The results demonstrate that the parallel hybrid propulsion system has enhanced the performance of the existing system.

Highlights

• •Hybrid propulsion is explored for MALE UAVs, generally ICE-powered, to enhance efficiency and extend flight hours.
• •An electric machine is designed and integrated into a UAV to assess performance.
• •The study aims to lower ICE operating points and reduce environmental impact, contributing to greener propulsion systems.

1. Introduction

Unmanned Aerial Vehicles (UAVs) which are used in both civilian and military applications are getting popular and their usage in real life is getting growth because of their environment friendly, silent and efficient operations. There are different concepts for UAVs and main architectures are mentioned as fixed wing, multi-rotor and vertical take-off UAVs. Beside these, UAVs have different propulsion systems and they've been selected based on their reliability, efficiency and power [[1], [2], [3], [4], [5]]. However, there is a general classification which is based on their maximum take-off weight (MTOW), operating altitude and operation range. NATO classification for UAVs is shown in Table I [[6], [7], [8]].

Table 1.

UAV classification.

Class	Category	Mass [kg]	Range [km]	Altitude [m]
Class I	Micro	< 5	< 5	< 100
	Mini	< 15	< 25	< 1000
Class II	Small Tactical	≥ 15 150-600	< 50 < 200	< 1500 < 5500
Class III	MALE	> 600	Unlimited	< 13000
	HALE	> 600	Unlimited	< 20000

According to their class, they have different propulsion system topologies. Especially in Class I, electrical propulsion systems could be selected while considering their mass, range and altitude. However, Class II and III have significant weight, altitude and range values which needs powerful propulsion systems to meet these specifications which is also mentioned in Ref. [9]. ICE is commonly used for Class II and Class III UAVs [1,10,11]. ICEs are conventional propulsion components, and they have approximately 40 % efficiency. Addition to that they are harmful for environment because they are emitting hazardous materials to air. On the other hand, there is another important topic that is about fossil fuel sources. A report published by a petroleum company has indicated that fossil fuel sources may experience a shortage in the coming years [2,[12], [13], [14], [15]]. In order to address this challenge, ongoing academic research is seeking to explore and develop alternative powertrain components that are not powered by fossil fuels. As an alternative, electric power and electrical machines which are working with electric power are considered because of their high efficiency, low operation cost and environmental friendly behavior [13,[16], [17], [18]]. However, fully electrical concepts are insufficient for certain applications that necessitate prolonged endurance and range, given the limitations of current electrical power sources. Hybrid systems are offering solutions to overcome these concerns. It's already popular with cars and other ground transportation vehicles and it's getting popular with aerial vehicles as well.

The concept of hybrid propulsion system based on integrating conventional ICE system with alternate powertrain components [2,4,15,16,19,20].

Basically, hybrid propulsion systems have 3 topologies named as series, parallel and series-parallel. Based on operation profile, related systems could be selected to implement vehicles. Basic system schematic for related hybrid systems are shown in Fig. 1. In series hybrid topology, propellers are directly driven by electric machine which is fed by battery and external generator over converter and control circuit. The main advantage of series hybrid systems is that there is no need for additional mechanical coupling equipment through the propeller. In that case, electric machine is carrying all propulsive function and ICE is only driving generator. With this respect, ICE size could be reduced. However, the only source to drive propeller is electric machine and redundancy of the system couldn't be achieved if there is a fault on electric machine. Parallel hybrid system has connection both ICE and electric machine while driving propeller. Electric machine has a role as supportive to ICE and it reduces load on ICE while driving. Also, there is redundancy in case of any failure on engines. Moreover, ICE could be selected smaller than before because of supportive function of ICE that comes splitting power demand to drive propeller at required power. However, there is an also coupling components needed in this topology and it could add extra weight on board. Series-parallel configuration is the most complex topology among these three. There is adding more components to create a system, and its complexity could cause another problem like maintenance issues. It's been considered as adding series and parallel hybrid together and creating another hybrid system with that [2,12,14,21].

Fig. 1.

Schematic representation of hybrid system Configurations.

In addition, literature and ongoing studies are focused on the implementation of electric or hybrid systems in UAV and other transportation vehicles as well. As previously mentioned in the following studies [9,22,23]. They're mainly focused on small aircraft because of limitations about electrical energy storage. Moreover, there are several electrical power sources such as fuel cells, super-capacitors and batteries to supply the required power for electric machines. They have both advantages and disadvantages because of their inherent structures [[24], [25], [26]]. In this study, lithium battery has been selected because it's certified for aviation applications. About implementation of hybrid propulsion systems, it's been mentioned that hybrid propulsion systems could provide longer endurance while comparing with full electric propulsion systems as mentioned in following studies [24,27]. Some works are focused to simulate electric or hybrid propulsion system on MALE class UAVs but there is just prediction with using tabulated data or existing electric machines [4,[28], [29], [30], [31], [32], [33]].

The objective of this study is to implement a hybrid system on a MALE class UAV that is currently in use with a designed electric machine, the specifications of which are based on the requirements for related UAVs. The novelty of this work is the proposal of a hybrid propulsion system with a newly designed machine that has not been previously observed in literature. The created models and simulations are generally accomplished and analyzed with existing electric machines on the market and their performance on aircraft. MALE class UAVs have significant range and endurance which can be measured with flight hours. With this study, it's been tried to enhance flight hours and offered the lower operating point for ICE to reduce fuel consumption. To observe flight hours and operation of hybrid propulsion system, Electrical machine, UAV and ICE models have been created on computer aided software. Electrical machine (EM) designed as Brushless DC (BLDC) motor because of its high torque-weight ratio, easy control capability, low operating and maintenance cost, high efficiency and low noise level [17,34,35]. Its rating power and DC supply voltage value are selected as 40 kW and 400 V respectively. Regarding these values, torque value is calculated as 152 N-meters (Nm). After designing electrical machine, ICE model which is currently used in referenced UAV has been created on MATLAB-Simulink. Rotax 914 is currently used on referenced UAV as an ICE and it's modeled with required parameters according to manufacturers' specification. To observe combined performance of these propulsion elements, UAV model has been created via using DATCOM software and imported to MATLAB-Simulink. Created models are combined with environment and flight control components. To calculate produced thrust, equations block has been created and needed parameters for calculation are taken from EM and ICE blocks. While calculating thrust, propeller has been considered and specifications of propeller are added to calculation block on MATLAB-Simulink. Selected hybrid topology for this study is parallel hybrid propulsion system. With this concept, EM and ICE are connected to same shaft and there is supportive relation between two propulsion systems. There are advantages regarding that topology, which is about providing redundancy, running ICE in optimum range and reducing the fuel consumption as explained before. It's targeted to reduce fuel consumption, relax ICE operating point and enhance operation time with created parallel hybrid system when compared with conventional propulsion system. In methodology section, EM, ICE and UAV models' creation are explained and supported with related figures. Different models combined and created final model which has parallel hybrid system and UAV model. After running this model, obtained outcomes are shared in the Results section and compared with aimed values. In the conclusion part, all results are shared and explained in detail.

2. Methodology

In methodology part, EM, ICE and UAV models creation explained in detail. EM model creation and related formulation for design processes have been shared in related sections. There is also a part about system level modeling which is created from simulation results of designed machine. ICE section includes Rotax 914 based model creation with regard of manufacturer's data. At the end of the part UAV model and combined model are explained.

2.1. Electric machine modeling

The first step of starting electric machine design begins with determination of machine power, speed, pole/slot combination, number of phases, and DC voltage values. Subsequently, machine dimensions have been calculated with using Equation (1) and Equation (2) following the determination of the parameters [[36], [37], [38]].

$$D^{2}l=\frac{P}{C\left(\frac{n}{60}\right)}$$ (1)

$$X=\sqrt[3]{p}\frac{\mathrm{\pi }}{2p}$$ (2)

Following the calculation of the machine's diameter, length, and their respective ratios, the air gap length has been determined. The calculated values, obtained from the aforementioned calculations and determinations, are presented in Table II.

Table 2.

Determined and calculated values of electric machine.

Variable	Value
Machine Power (P)	40 [kW]
Rated Speed (n)	500 [rpm]
Machine Constant (C)	150 [kWs/m3]
Pole/Slot Combination	14/15
Number of Phases	3
DC Voltage	400 [V]
Stator Inner Diameter (D)	278.3 [mm]
Stack Length (l)	82.6 [mm]
Air-gap	1 [mm]
Winding Factor (kw)	0.95
Integer α	2π
Air-gap Flux Density	0.8 [T]

Helping with these parameters, the number of turns can be calculated according to Equation (3) where E, kw, τp, α, B signs are back emf, winding factor, pole pitch, coefficient and air-gap magnetic flux density value respectively. Back-emf value is calculated from given Equation (4). The value of number of turns in a single-phase effects air-gap flux density and according to that projected and calculated values could be compared with each other [36].

$$N=\frac{\sqrt{2}E}{\mathrm{\omega }{k}_{w}l{\mathrm{\tau }}_p\mathrm{\alpha }B}$$ (3)

$$E=0.95V_{d}c$$ (4)

Stator tooth and slot dimensions have been calculated as next steps of design process. It's calculated with magnetic flux and current density values which are created by windings. Calculated values are shown in Table III.

Table 3.

Stator tooth and slot dimensions.

Variable	Value [mm]
Slot Opening Width	5
Slot Opening Height	0.5
Length Between Stator Teeth	32.38
Stator Tooth Height	22.74
Stator Yoke	18.5

Magnet thickness is the next parameter to calculate which affects magnetic field strength in rotor side. Equation (5) has been used to calculate magnet thickness. Parameters which are used in Equation (5) are shared in Table IV.

$$d_m=\frac{B\left(\left({\mathrm{\mu }}_m\right)/\left({\mathrm{\mu }}_0\right)\right)g_m{K}_l{K}_{r}g}{g_m{K}_l{B}_r-B}$$ (5)

Table 4.

Parameters for calculation of magnet thickness.

Variable	Value
Air-gap Flux Density (B)	0.8 [T]
Magnetic Permeability of Magnet (μm)	1.3219 [μH/m]
Magnetic Permeability of Air (μ0)	1.2566 [μH/m]
Stator Tooth Arc Ratio (gm)	0.94
Leakage Factor (Kl)	0.85
Reluctance Factor (Kr)	1.3
Air-gap	1 [mm]

The computer aided model has been created using calculated parameters and it's been simulated on ANSYS Motor-CAD. To mention that designed machine drive has been accomplished with idealized trapezoidal wave form. There is no drive section of designed machine in this study. Because of that idealized wave form has been selected regarding with machine drive.

Following the completion of the simulation processes, the data generated by the designed machine is exported to a system-level model utilizing ANSYS Motor-CAD. The fundamental parameters of the electric machine are presented in Table V. System-level modelling facilitates the generation of more expedient and precise results when compared to those obtained from full simulations. Fig. 2 illustrates the system-level model that has been constructed.

Table 5.

Fundamental parameters of electric machine.

Variable	Value
Machine Power	40 [kW]
Rated Speed	2500 [rpm]
Number of Phases	3
DC Voltage	400 [V]
Rated Torque	152 [Nm]
Peak Line Current	109.4 [A]
Back-EMF	380 [V]
Machine Weight (with Cooling Equipment)	65 [kg]

Fig. 2.

Created EM model based on detailed simulation data.

The designed electric machine has an efficiency value of approximately 95 % according to the simulation results. The efficiency map of the designed machine is presented in Fig. 3 and demonstrates a correlation with the target values that were calculated at the outset of the design process.

Fig. 3.

Efficiency map of designed electric machine.

The fluctuations in power and torque against speed are illustrated in Fig. 4, Fig. 5. The figures demonstrate that the power and torque values are aligned with the target values, thereby substantiating the efficacy of the parameters that are calculated during the design process.

Fig. 4.

Power-speed alteration of designed electric machine.

Fig. 5.

Torque-speed alteration of designed electric machine.

EM model connected to battery which is created with specifications of Pipistrel aircraft's battery. The battery model has been chosen from currently used electric aircraft which is already certified for aviation applications. Specifications of battery are shared in Table VI [39].

Table 6.

Created battery model specifications.

Variable	Value
Nominal Voltage	345 [V]
Cell Capacity	78 [Ah]
Cell Configuration	96S12P
Maximum Continuous Discharge Power	40 [kW]
Battery Weight	70 [kg]

One advantage of system level modelling is that it offers a more straightforward approach to EM speed and torque control than a fully simulated design. The speed reference and load torque are applied through the throttle control block in a manner that is appropriate for a UAV. Speed and torque value which is created by EM model are gathered and forwarded to related block to calculate produced thrust. Also, state of charge (SoC) value of battery is tracked and limited to minimum value with 20 %.

2.2. Generation of internal combustion engine model

According to referenced UAV's specification, the ICE model is created as Rotax 914. In order to create model of the Rotax 914 engine's parameters in MATLAB Simulink, the Installation Manual (IM) has been used as a source of related data. Critical parameters for ICE are shared in Table VII [40].

Table 7.

Modeled rotax 914 ICE specifications.

Variable	Value
Max. Power	84.5 [kW]
Max. Speed	5800 [rpm]
Torque (@4900 rpm)	144 [Nm]
Total Weight (with Accessories)	75.5 [kg]

As referenced in installation manual [40] and papers at [41,42]; ICE performance is changing with altitude of aircraft. To implement this effect on model, output power of the ICE is created depending on speed command which is coming from throttle control block and current altitude of aircraft. The created ICE model is shared in Fig. 6. Fuel consumption values are obtained from installation manual and tabulated on MATLAB-Simulink. It's correlated with the engine's speed value and changes depending on that. Because of that it’s implemented with speed control block which is designed to determine engines speed during simulation.

Fig. 6.

Created ICE model as an existing propulsion system.

There is also a gearbox model that is located between propeller and ICE to add effects of mechanical components. To implement gearbox effect on the created model, there is a gain factor block which contains gearbox ratio and efficiency values. Gathered value for output power is forwarded to related block to calculate produced thrust.

2.3. Generation of reference UAV model

UAV model is referenced by existing model which is named MQ-1 Predator. It's a MALE class UAV and capable to fly up to 24 h [43]. Based on physical dimensions and wing airfoil type, aerodynamic coefficients have been calculated with using DATCOM software which is created by U.S. Air Force. DATCOM software has been created to calculate static stability, control and dynamic derivatives of fixed wing aircraft by U.S Air Force. Calculated parameters by DATCOM imported to MATLAB Simulink via dedicated block and combined with forces which are environment, gravity force and additional forces because of pitch movement of aircraft. Created model shared in Fig. 7 [[44], [45], [46]].

Fig. 7.

Created UAV model based on aerodynamic calculations.

In the case of gravitational forces, the remaining fuel on board is a determining factor. Consequently, the remaining fuel value is gathered from ICE block and added to mass of UAV to get realistic results. Additionally, an environmental model has been developed to incorporate wind effects on the UAV. In regard to the movement of the UAV, only pitch movement is modeled with the objective of stabilizing the aircraft at the desired altitude. The model does not include yaw and roll movements.

2.4. Combination of separately created models

As explained in previous subsections, 3 different main blocks have been created separately. To see the effects of created hybrid system on UAV, these main blocks should have connected each other with auxiliary blocks. These auxiliary blocks are responsible for arranging throttle command to keep aircraft is demanded speed, to send speed commands to EM and ICE blocks which is demanded power to produce required thrust and to calculate produced thrust. These blocks names are Throttle control, Speed control and Thrust respectively. The whole system model is shared in Fig. 8.

Fig. 8.

Created system model for parallel hybrid propulsion system.

2.5. Mission profile

In order to observe the effects of the hybrid system on the UAV, a mission profile is created which takes into account the operational duration, altitude, speed and weight specifications. The aforementioned parameters are selected on the basis of the characteristics of the reference UAV. Operation duration should be 24 h at least with ICE operation [43]. Altitude values are selected as 3000 m (9842 ft) to 3500 m (11482 ft) which are within limits of UAV's capability as climbing session in mission profile.

The speed of UAV is selected for body as 50 m/s in cruise and throttle control blocks are making arrangements to keep it in selected value. Calibrated Air Speed (CAS) is also measured and arranged within limits which is combination of body speed, air pressure and Mach speed. Weight of UAV is determined as 950 kg at the beginning of simulation. According to manufacturer's manuals, MTOW is nearly 1000 kg when loaded with all equipment and fuel on board. The created mission profile is just including the cruise phase of flight and remaining fuel is entered 250 kg because it's predicted that 50 kg of fuel is burned in ascending phase. Simulation ends when the remaining fuel value reaches 50 kg that is selected same as burned fuel in ascending phase. In the speed control module, the hybrid propulsion sequence is arranged and triggered with the application of dedicated values of remaining fuel and SoC. The EM operates in conjunction with the ICE at the outset of the simulation and provides support to the ICE during the ascending phase of the mission profile. EM is worked until SoC reached 20 % which is target level to protect battery and EM to avoid unwanted conditions.

3. Results

The created hybrid propulsion system model has been run with all main and auxiliary blocks. Gathered results after completion of simulation are shared in this part with graphical materials. Critical parameters are determined according to their importance in the designed propulsion system.

EM and ICE parameters are observed because these are the main components of hybrid propulsion system. To control aircraft's body speed and altitude, these parameters are also gathered, they are observed and forwarded to related blocks. As explained in the methodology part, provided power from ICE is changing according to altitude and shaft speed of the ICE. Because of that these parameters are used in ICE block and throttle control block as well. Thrust value is another important parameter which is needed force to fly aircraft with commanded values such as altitude and body speed.

According to mission profile, which is shared in Methodology part, body speed of the UAV should be controlled to avoid overspeed situation. To achieve this protection, throttle control block is created. CAS and body speed are measured during simulation and shared in Fig. 9. As can be seen in Fig. 9, overspeed situation didn't happen according to maximum speed value that shared in UAV specification during the simulation. It's been changing between the top speed limit which is 61 m/s and stall speed as 27 m/s. Nearly at 1500 s, there is descending values in speed because altitude command changed from 3000 m to 3500 m at this moment and the UAV is shifting to ascending phase according to the mission profile and that is evaluated as normal.

Fig. 9.

CAS and body speed values gathered during simulation.

Altitude traction is another parameter for observation to examine created hybrid propulsion system's performance about lifting aircraft on the air with desired altitude. It's related to thrust force which is produced by propulsion system components. Addition to that elevator commands also affected to change altitude of the UAV with moving related flight control surfaces. Altitude command and altitude response of UAV have been shared on Fig. 10. UAV's response to altitude command is matched with desired altitude that can be seen in Fig. 10.

Fig. 10.

Altitude response of created UAV model with hybrid propulsion system.

Thrust is another important parameter because it is the propulsive power which is needed to fly aircraft against drag force. In Fig. 11, produced thrust from hybrid propulsion system is shared. According to related figure, thrust is increased while climbing because ascending phase of flight needs more propulsive power in that phase, and it is achieved with relaxing operation both for EM and ICE which can be seen power values in same phase of flight in Fig. 12. At this point, EM has provided nearly 19 kW and ICE 14 kW. Before ascending, EM produced 6.5 kW and ICE 2.2 kW. Compared with rated peak values and ICE only operation, ICE is operating relaxer while EM is running. With stand-alone operation, ICE needs to produce 8.9 kW. The designed hybrid propulsion system reduced operating points of propulsion components with supportive function of EM over ICE.

Fig. 11.

Thrust values of created UAV model with hybrid propulsion system.

Fig. 12.

ICE and EM powers for created hybrid propulsion system.

In mission profile, EM is starting to work at the beginning of simulation until SoC level is dropped to 20 %. During simulation, that is observed from SoC percentage, ICE and EM powers and EM torque graphics. It can be seen from Fig. 12; EM is working as supportive component to ICE during simulation and ICE power needs to be increased to meet required thrust when EM stopped. That naturally increased fuel consumption because ICE is working more when compared with the case that EM is operative. Also, EM torque values observed and shared in Fig. 13 to show produced torque from designed EM. It can be seen that it’s capable of supporting ICE to relax its operating point and reduce fuel consumption. There is some overshoot points in ICE and EM operations because of switching between hybrid and conventional propulsion system. It's considered as normal and negligible while switching sequence which comes from throttle and speed control blocks. These are just in seconds and it's not effective on operation values because that is a basically mathematical model and there is no soft transaction while switching between propulsion systems.

Fig. 13.

EM Torque alteration for the designed machine.

SoC and remaining fuel values are also changing because of hybrid system's inherent structure. Remaining fuel is related with fuel consumption rate of ICE which is modeled according to manufacturer's manual and it's lower than full ICE operation while EM is in operation. Also, SoC value decreased in same phase because EM is in operation and EM current and voltage values increased. SoC and remaining fuel values are shown in Fig. 14. SoC values are shared as percentage and remaining fuel values are shared as kg in related figure.

Fig. 14.

SoC and remaining fuel values for created hybrid propulsion system.

Simulation stopped when remaining fuel is reaching 50 kg as explained before that is regarding with related work's consideration which is only for cruise phase of flight and observing the hybrid system's effect on flight duration during this phase of flight. According to data about referenced UAV, it can fly nearly 24 h (86400 s) in cruise phase of flight. Created model simulation is completed at 30.1 h (108609 s). EM is in operation for nearly 2.2 h and operation duration is increased about 6.1 h while comparing with only ICE operation.

4. Discussion

The hybrid propulsion system has been selected for implementation in the existing UAV model to facilitate the study and demonstration of its potential to enhance flight hours and relax the operating zone of ICE. Hybrid propulsion systems appear to offer a more viable option for integrating ICE powered aircraft than fully electrical propulsion systems. However, the current energy storage capacity of batteries and concerns about additional weight on aircraft make it challenging to achieve high endurance with the allowable battery quantity on aircraft, particularly in comparison with ICE performance. Because of that, the hybrid propulsion system is selected to implement on referenced UAV model to observe impact on flight hours for selected UAV and effects on ICE's workload as well. When compared with ICE powered UAV performance, operation duration has been enhanced nearly quarter of existing flight hours which is achieved with ICE. There is a possibility of creating hybrid propulsion system with different combinations to meet different requirements or enhancements while placing components of hybrid propulsion system on aircraft. However, this study is based on basic assumption while placing hybrid propulsion system's components without considering weight distribution on aircraft. The novelty of this study comes from implementation of newly designed electric machine on proposed hybrid propulsion system topology on currently used UAV and evaluation its effects on that. As can be seen from the results part, flight duration has been enhanced and ICE operation has been relaxed as aimed with created hybrid propulsion system. For future studies, power management systems could be designed with detail for hybrid propulsion system and operation duration may enhanced when compared with this study. Also, existing ICE could be replaced with a smaller one and fuel tank capacity could be decreased to arrange weight distribution according to allowed limits of aircraft. The objective of this study is to demonstrate the impact of a parallel hybrid propulsion system, constructed with an innovative apparatus, when integrated into the existing UAV.

5. Conclusion

The popularity of hybrid propulsion systems is increasing across a range of industries, including aviation, automotive and other forms of transportation. The primary objective of integrating this technology into a conventional propulsion system is to mitigate adverse environmental impacts and enhance the overall efficiency of the system. A review of the literature reveals the existence of a number of different hybrid propulsion system configurations. Furthermore, feasibility assessments of hybrid systems are frequently conducted through simulations that utilize existing electric machines. In this study, a parallel hybrid system has been selected in order to meet the requirements of the dedicated specifications, namely to provide redundancy, to enable the ICE to be operated at its optimum operating point and to offer the possibility of reducing fuel consumption. In the process of creating a hybrid system, a new electrical machine is designed and coupled with an ICE model that is based on the manufacturer's data and implemented on a UAV model that has been created with aerodynamic parameters. According to simulation results, operation duration of UAV has been increased nearly 25 % based on hours with designed system when compared with existing model which is only used with ICE and achieved to main purpose of this study. On the other hand, it's been observed that designed electric machine is achieved its supportive function to ICE and ICE's fuel consumption has been reduced during EM operation. That can be said that EM is relaxing ICE's operation point that is aimed to achieve with this study. The subject of this study is the design of power management modules and mission profiles. The findings demonstrate that a hybrid propulsion system can be more efficient than a conventional propulsion system, with a positive impact on operational duration, despite the basic design.

CRediT authorship contribution statement

Emre Kurt: Writing – review & editing, Writing – original draft, Visualization, Validation, Software, Methodology, Investigation, Conceptualization. Ahmet Yigit Arabul: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Methodology, Investigation, Conceptualization. Fatma Keskin Arabul: Writing – review & editing, Writing – original draft, Visualization, Validation, Software, Methodology, Investigation, Conceptualization. Ibrahim Senol: Writing – review & editing, Writing – original draft, Validation, Supervision, Conceptualization.

Data availability statement

Data will be made available on request. For requesting data, please write to the corresponding author.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.