The Study of Electrical Energy Power Supply System for UAVs Based on the Energy Storage Technology
, Jan Leuchter 1, Radek Bystricky 1, Milos Andrle 1, Ngoc Nam Pham 2 and Van Thuan Pham 3Round 1
Reviewer 1 Report
In the submitted paper, the authors present an overview of the structure, classification, dynamic model and control methods of UAVs and one of the current leading concerns about the problem of energy supply for UAV operation. In the submitted paper, two very interesting experiments were conducted to evaluate the energy consumption of UAV and the efficiency of energy conversion from wind energy to electric energy and evaluate the influence of converted energy on the UAV performance. The experimental results showed that the main energy consumption of the quadrotor is during flight. Therefore, the authors conclude that to increase UAV’s performance, UAVs must fly to high altitudes to take advantage of wind energy. Furthermore, it was demonstrated that the efficiency of energy conversion from wind energy to electric energy is approximately 50%. From there the authors calculated the UVA’s gain efficiency.
The paper is clearly written and self explanatory. The introduction describes well the objective of the rest of the paper. References are appropriate. The application presented in this manuscript is of rather high interest in the field of UAV systems.
The reviewer finds very interesting the discussion about electric and hybrid UAV using innovative energy storage technologies, especially the part related to batteries and supercapacitors management. The proposed power management strategies are widely adopted even by larger aerial vehicles such as More Electric Aircrafts or Hybrid Aircrafts. Therefore, I would suggest the authors to extend their discussion and mention the possible application of such method to other fields. To this extend, I would suggest also to expand the literature review with the following recent works:
A. Russo and A. Cavallo, "Supercapacitor stability and control for More Electric Aircraft application," 2020 European Control Conference (ECC), 2020, pp. 1909-1914.
G. Canciello, A. Russo, B. Guida and A. Cavallo, "Supervisory Control for Energy Storage System Onboard Aircraft," 2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), 2018, pp. 1-6.
Finally, the reviewers spotted a few typos reported hereafter:
- page 12, line 424, the symbol used for inclusion of (x,y,z) in R^3 is incorrect, it should be flipped the other way around
- page 13, line 443, the parenthesis in the second equation seems to be wrong as it is equal to 0. The reviewer believes that the term in parentheses should be Ixx - Izz
- page 22, line 706, W.h should be Wh
- page 24, line 739, it should be 15m/s rather than 15m/2
As there may be other typos, the reviewer suggests to double check the English grammar.
Other than this, I support the publication of the submitted manuscript.
Author Response
Response to Reviewer 1 Comments
Point 1: The proposed power management strategies are widely adopted even by larger aerial vehicles such as More Electric Aircrafts or Hybrid Aircrafts. Therefore, I would suggest the authors to extend their discussion and mention the possible application of such method to other fields.
Response 1: thank you for the comment to help us to improve our paper. We have added the discussion about power management strategies and their possible application in Chapter 2. The discussion and possible application of such methods are added in the updated submission. The added text is in lines 272-290
ADDED:
Energy management strategy for UAV
There have been many energy management strategies (EMS) for UAVs studied and reported in various articles. Authors in [34] presented various EMS for UAVs in different flight segments with varying sizes of battery packs. In [35], Xie et al. introduced a comprehensive review of conceptual design and energy management methodologies for hybrid electric-powered aircraft. In [36] Antonio Russo and Alberto Cavallo presented a method to deal with the stability analysis and the control of a supercapacitor based on Second Order Sliding Mode for a More Electric Aircraft. In [37] Giacomo at el. Introduced an alternative EMS for aeronautic applications. The strategy is charging a battery in nominal condition and when the overload happens, the battery is used to help the generator.
Hybrid systems combine the advantages of different energy sources and balance their limitations, resulting in a significant increase in system performance. It is therefore very suitable for use in powering UAV systems. In EMS, power needs to be optimally split between power sources to achieve high performance of the system and efficiency of energy usage. The EMS can be mainly considered as follows: Rule-based, Intelligent-based, Optimization-based, and others.
Point 2: the reviewers spotted a few typos reported hereafter:
- page 12, line 424, the symbol used for inclusion of (x,y,z) in R^3 is incorrect, it should be flipped the other way around.
- page 13, line 443, the parenthesis in the second equation seems to be wrong as it is equal to 0.
- page 22, line 706, W.h should be Wh
- page 24, line 739, it should be 15m/s rather than 15m/2
Response 2: Thank you for the careful review to help us improve the editorial correction. We have rechecked all the text and sentences to make sure there is no mistake. The errors have been removed in the updated submission.
Point 3: the reviewer suggests to double-check the English grammar.
Response 3: Thank you for this comment as we are aware of this problem. As the authors are not native English speakers, we consulted with and sent the manuscript to language teachers to improve the English language in this paper. We hope the improvement in the presentation with the current submission could meet the requirements.
Reviewer 2 Report
The article is relevant. The main issue to be resolved is the search for solutions to increase the time spent by an unmanned aerial vehicle in the air. The authors are looking for the possibility of recharging the UAV battery using wind energy.
Of interest in the article is an overview of solutions for providing energy to UAVs and the results of experimental studies.
Although they are not original to a high degree, nevertheless the review is carried out in a large volume, and the experimental data are well specific. The study adds to the subject area an experimental assessment of the possibility of recharging the power source of the UAV due to wind energy while reducing the UAV of the quadrocopter type.
In terms of methodology, the authors could improve the following. In my opinion, the article provides an overly detailed overview of the areas of application of UAVs, options for energy sources for them. At the same time, the authors are exploring specific types of UAVs, namely quadrocopters.
The review related to the subject of the research of the authors - methods of recharging quadrocopters from wind energy has not been sufficiently completed. The experiment considers the perpendicular placement of the UAV in a wind tunnel. This does not allow taking into account horizontal and directed at different angles air flows. In future studies, the authors are encouraged to conduct such experiments. The conclusions are in good agreement with the arguments presented.
Links are relevant.
Table 1 is given, but its material is poorly used in further explanations in connection with the choice of the subject of research.
Author Response
Response to Reviewer 2 Comments
Point 1: In terms of methodology, the authors could improve the following. In my opinion, the article provides an overly detailed overview of the areas of application of UAVs, and options for energy sources for them. At the same time, the authors are exploring specific types of UAVs, namely quadrocopters.
Response 1: Thank you for the comment. Hybridization is the most suitable architecture to power the propulsion system in UAVs. It allows combining advantages and performances of different power sources and balancing their limitations. The hybrid concept is used on many types of UAVs and other applications. Therefore, we would like to cover their applications as well as power sources for UAVs in our article. In addition, we also focus only on quadrotors with the explanation in point 3.
Point 2: The review related to the subject of the research of the authors - methods of recharging quadrocopters from wind energy has not been sufficiently completed. The experiment considers the perpendicular placement of the UAV in a wind tunnel. This does not allow taking into account horizontal and directed at different angles air flows. In future studies, the authors are encouraged to conduct such experiments.
Response 2: Thank you for the thorough review to help us improve the paper. First of all, we would like to say that the reviewer is completely right, and we agree with him. Calculating the parameters of different angles of airflow on the efficiency of wind energy conversion makes the evaluation more accurate and comprehensive. However, this calculation will lead to further complexity of the system model. In addition, our goal was to focus on The study of Electrical Energy Power Supply systems for UAVs based on Energy Storage Technology to show a general concept and study of the hybrid systems. At the same time, we think that our system helps us to describe the concept of the method of recharging quadcopters from wind energy. In future studies, we definitely conduct such experiments and currently, we are working on it.
Point 3: Table 1 is given, but its material is poorly used in further explanations in connection with the choice of the subject of research.
Response 3: Thank you for a comprehensive review. We have given more evidence that rotary wings are more and more widely used in many fields due to their advantages. At the same time, we also point out the problem of this type of UAV. The further explanation in connection with the choice of the subject of research are added in the updated submission. The added texts are in lines 111-127.
ADDED: From Table 1, it can be seen that the Rotary-wing UAV (multirotor) is used more commonly in both civil and military applications due to advantages such as cost, high maneuverability, etc… In 2004, most UAVs are produced for military purposes. The UAVs intended for civilian use account for a very small and insignificant proportion compared to 98% of the UAVs used in the military [28]. At that time, fixed-wing UAVs were most commonly used in the military field. With the development and popularity of science and technology available on UAV to the hobbyists, rotary-wing UAVs are increasingly interested by hobbyists, commercial organizations and governments. The rotary-wing UAVs account for 62.8% of global market share, while Fixed-wing and the rest account for 25.4% and 12 respectively [29]. However, the problem of energy consumption of Rotary-wing UAVs is still a big challenge when it consumes higher energy than the other two types. Rotary-wing UAVs often use many motors to help UAV overcome the gravity of the earth, hence the energy consumed during the flight is very large, making the flight time of the rotary wing shorter. In addition, commercial rotary-wing UAVs usually have a flight time of less than 1 hour. Therefore, in this paper, the authors focus on solutions to solve the problem of power supply for rotary-wing systems (especially, quadrotors). However, before moving forward on that, let us first briefly discuss UAV’s components.
Reviewer 3 Report
This paper will investigate the electric energy supply problem for UAV, because the electric power is not easy to be stored onboard. The research topic is the windmilling effect of propeller motor can be converted in to electric power,and using the regenerated energy can increase the flight endurance of UAV. The selected topic is interesting, but the depth of research is not enough, the effect of regenerated energy for propulsion motor and battery's parameters are not considered. The novelty of this paper is not clear
1)this paper is not review paper, but the research content and detail about the winding energy conversion to electric energy are not presented in detail. the coupling relationship between the aerodynamic and power-train of UAV are not analyzed in this paper, any theory about this are not given in this paper.
2) when wind energy conversion happened, the dc bus voltage maybe deviated from the normal value because of the regenerated energy, for quad-rotor UAV , how to realize the flight control and power control coordinated? the control methods are nor presented in this paper . the paper just listed some kinds of methods.
3) "Aviation emits 2% of CO2 annually and is predicted to increase to an average of 4 to 5% in the future. If this continues without taking concrete action to control it, ICAO expects the emissions to roughly triple by 2050, which will account for 25% of global carbon emissions."in line 223-225,is there any reference paper to support this sentence?
4）there are some replica sentence in this paper, such as in line 577,578 is same as the line 582,583,584, it is better is revise this expression to make the paper more compact.
5) the aerodynamic equations and energy flow equations are listed in this paper, but the optimization control and management strategies can not be presented in this paper, how to realize the electric energy supply from the environmental conditions to increase the flight time of UAV, the key methods and mechanisms can not be found in this paper.
6 In order to improve the quality of this paper,some relative reference paper can be listed as following:
1)Cinar, G.; Markov, A.A.; Gladin, J.C.; Garcia, E.; Mavris, D.N.; Patnaik, S.S. Feasibility Assessments of a Hybrid Turboelectric Medium Altitude Long Endurance Unmanned Aerial Vehicle. In Proceedings of the AIAA Propulsion and Energy Forum, Virtual, 24–28 August 2020.
2)Dwivedi, V.S.; Giri, D.K.; Ghosh, A.K.; Kamath, G.M. Optimal Energy Utilization for a Solar-Powered Aircraft Using Sliding-Mode-Based Attitude Control. IEEE Trans. Aerosp. Electron. Syst. 2021, 57, 105–118.
3)Xie, Y.; Savvarisal, A.; Tsourdos, A.; Zhang, D.; Gu, J. Review of hybrid electric powered aircraft, its conceptual design and energy management methodologies. Chin. J. Aeronaut. 2021, 34, 432–450.
4)Boukoberine, M.N.; Zhou, Z.; Benbouzid, M. A critical review on unmanned aerial vehicles power supply and energy management: Solutions, strategies, and prospects. Appl. Energy 2019, 255, 113823.
5)Tao, L.E.I.; Zhou, Y.A.N.G.; Zicun, L.I.N.; Zhang, X. The state of art on energy management strategy for hybrid-powered unmanned aerial vehicle. Chin. J. Aeronaut. 2019, 32, 1488–1503.
6)Dantsker, O.D.; Caccamo, M.; Imtiaz, S. Electric Propulsion System Optimization for Long-Endurance and Solar-Powered Unmanned Aircraft. In Proceedings of the AIAA Propulsion and Energy 2019 Forum, Indianapolis, IN, USA, 19–22 August 2019.
7) Hanze Ritcher, Control for optimal energy regeneration from autorotation in UAVs，2020 American Control Conference Denver, CO, USA, July 1-3, 2020.
Control for optimal energy regeneration from autorotation in UAVs
Author Response
The answer has pictures, to see them, please see the attached file.
Response to Reviewer 3 Comments
Point 1: The selected topic is interesting, but the depth of research is not enough, the effect of regenerated energy on propulsion motor and battery parameters are not considered. The novelty of this paper is not clear.
Response 1: Thank you for the thorough review to help us improve the paper. Our goal was to focus on The study of Electrical Energy Power Supply Systems for UAVs based on Energy Storage Technology to show a general concept and study of the hybrid system. We analyze UAV's possibility to store energy by converting wind energy to electric power. In addition, when the UAV is in the windmill brake state, the motors stop producing the thrust forces and they act as generators to charge the battery during UAV descent. Therefore, the effect of regenerated energy on propulsion motor and battery parameters are not considered in detail.
There have been many research works on converting external energy source into electricity on UAVs such as solar energy. However, the use of wind energy to increase flight time for UAVs is still limited (most of the research is on fixed-wing UAVs), especially on quadrotors. Therefore, we want to provide a comprehensive view of the possibility of converting wind energy to electrical energy on a quadrotor.
Point 2: this paper is not review paper, but the research content and detail about the winding energy conversion to electric energy are not presented in detail. the coupling relationship between the aerodynamic and power-train of UAV are not analyzed in this paper, any theory about this are not given in this paper.
Response 2: Thank you for this comment, we appreciate the opportunity to complete our article. In order to better understand the energy conversion process from wind energy to electric energy, we have added a diagram of figure 18 to explain the direction of the converted energy. The airflow will act on the propeller to turn the motor. The motor will generate 3-phase AC and pass through the inverter to return to the energy storage device. We agree that the coupling relationship between the aerodynamic and power-train is important in UAV’s control. Although in this article, we have not gone deeper into the field of UAV control. However, as mentioned at the end of the conclusion for future work, we will conduct other experiments to evaluate the dependence of trajectory planning on UAV’s endurance by using various flight scenarios. Their relationship will be concluded in the next paper. In addition, our goal is to focus on the concept of energy conversion and storage technology.
ADDED:
3.1.1 Winding energy conversion of hybrid UAV.
The structure of the BLDC motor drive system is shown in Figure 18. In this topology, the voltage of the battery is proposed VBatt < Vsc (voltage of supercapacitor). Under normal conditions, the diode D1 and D2 are reverse biased. In this case, the battery and supercapacitor power the UAV's electric propulsion system by supplying the BLDC motors with suitable voltages. The conversion of wind energy to electrical energy when the regenerative braking event occurs. The D1 is forward biased, and the supercapacitor could harvest the braking energy through the inverter. When the voltage of the supercapacitor (VSC) is greater than the upper voltage limit of the supercapacitor ( VSCmax), the regenerative energy stops flowing into the capacitor, and then it goes to the battery through D2 which is in a state of forward biased. In the regenerative braking mode, the MOSFETs on the high side of the H-bridge are turned off and the low side is controlled by appropriate PWM.
Point 3: when wind energy conversion happened, the dc bus voltage may be deviated from the normal value because of the regenerated energy, for quad-rotor UAV, how to realize the flight control and power control coordinated? the control methods are not presented in this paper. The paper just listed some kinds of methods.
Response 3: Thank you for this comment to help us clarify the discussion. We used the microcontroller ESP-32 that can continuously measure the voltage of the battery and send the signal simultaneously to the flight controller (FC). The FC uses a PID or MPC controller to conduct continuous control with one input parameter being the wind energy conversion. The control algorithms in the FC will continuously compensate for errors to make the UAV can fly according to the trajectory.
ADDED: The dual-core ESP32 is used, to make the system work fluent. Core 0 is in charge of measuring the accumulator’s current and voltage, calculating the SoC, recording data to SD Card, and display to the OLED display. Then, the data calculated by Core 0 are sent via a wireless channel by Core 1. If the transmission is unsuccessful, it must be repeated by Core 1 without effect on the measurement process of Core 0.
Point 4: "Aviation emits 2% of CO2 annually and is predicted to increase to an average of 4 to 5% in the future. If this continues without taking concrete action to control it, ICAO expects the emissions to roughly triple by 2050, which will account for 25% of global carbon emissions."in line 223-225,is there any reference paper to support this sentence?
Response 4: Thank you for this comment. The reference paper supporting this sentence is the following:
- Wheeler, P.; Sirimanna, T. S.; Bozhko, S.; Haran, K. S. Electric/Hybrid-Electric Aircraft Propulsion Systems. Proceedings of the IEEE, 2021 vol. 109, no. 6, pp. 1115-1127.
The mentioned paragraph can be found in Chapter 2.
Point 5: there are some replica sentences in this paper, such as in line 577,578 is same as the line 582,583,584, it is better is revise this expression to make the paper more compact.
Response 5: Thank you for this comment, we appreciate the opportunity to complete our article. The replica sentences have been edited and rewritten to make the paper more compact.
Point 6: the aerodynamic equations and energy flow equations are listed in this paper, but the optimization control and management strategies can not be presented in this paper, how to realize the electric energy supply from the environmental conditions to increase the flight time of UAV, the key methods and mechanisms can not be found in this paper.
Response 6: Thank you for this comment to help us improve the paper’s quality. We have added lines 273-299 about the energy management strategy (EMS) for UAVs. By using EMS methods, the power supplied to the electric propulsion system is used optimally to increase the performance of the UAV and the efficiency of energy usage. We only focus on studying and considering the process of converting wind energy to electrical energy of the UAV as it gradually descends. Therefore, that conversion is enabled proactively by the user command.
ADDED:
2.2.1. Energy management strategy for UAV
There have been many energy management strategies (EMS) for UAVs studied and reported in various articles. Authors in [34] presented various EMS for UAVs in different flight segments with varying sizes of battery packs. In [35], Xie et al. introduced a comprehensive review of conceptual design and energy management methodologies for hybrid electric-powered aircraft. In [36] Antonio Russo and Alberto Cavallo presented a method to deal with the stability analysis and the control of a supercapacitor based on Second Order Sliding Mode for a More Electric Aircraft. In [37] Giacomo et al. Introduced an alternative EMS for aeronautic applications. The strategy is charging a battery in nominal condition and when the overload happens, the battery is used to help the generator.
Hybrid systems combine the advantages of different energy sources and balance their limitations, resulting in a significant increase in system performance. It is therefore very suitable for use in powering UAV systems. In EMS, power needs to be optimally split between power sources to achieve high performance of system and efficiency of energy usage. The EMS can be mainly considered as following: Rule-based, Intelligent-based, Optimization-based and others (shown on the Figure 7).
Author Response File: 
Author Response.docx
Round 2
Reviewer 3 Report
The winding energy is more relative to the flight trajectory of UAV, with different flight conditions such as environmental factors like air density, altitude. it is suggested that the author will discussed this in detailed.
