Research on Modeling of the Tilt Tri-rotor Unmanned Aerial Vehicle s Dynamic Fei ZHANG*, Ping LU, Tao JIANG and Feng-ming SHI

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1 17 nd International Conference on echanical Control and Automation (ICCA 17) ISBN: Research on odeling of the Tilt Tri-rotor Unmanned Aerial Vehicle s Dynamic Fei ZHANG*, Ping LU, Tao JIANG and Feng-ming SHI Department of UAV Engineering, Ordnance Engineering College, Shijiazhuang, 5, China *Corresponding author Keywords: Tilt tri-rotor UAV, Electric, Power System, odeling. Abstract. According to the basic principles of fixed-wing aircraft and multi-rotor design, combined with power requirement of the tilt tri-rotor UAV three flight modes, gives the tilt tri-rotor UAV power system model to solve the tilt tri-rotor UAV electric UAV power system matching problem, and to apply the theory completed a tilt tri-rotor UAV production, flight test was carried out to verify the theory. The experimental results analysis, tilt-rotor aircraft power system model in this paper can meet the general tilt rotor UAV power system design requirements. This achievement can provide theoretical references such UAV power system design. Introduction Tilt tri-rotor UAV with the advantages of multi-rotor UAV and fixed wing UAV can be tilted in front of the two rotor angle between the helicopter mode and fixed-wing mode conversion between the vertical can be achieved Low-speed flight and high-speed long-range mobile characteristics. Compared with traditional unmanned aerial vehicles, tilt tri-rotor UAV aircraft has more adaptability, wider range of applications and higher economic advantages, in the military, civilian market has broad application prospects [1-3].Tilt tri-rotor UAV in different flight modes, lift and power sources are different, resulting in its different flight mode power requirements are different. In helicopter mode, the main power of the aircraft comes from the upward lift provided by the propeller; in the fixed-wing mode, the aircraft lift is all provided by the wing, the propeller to enhance the forward pull of the aircraft; in the transition mode between the two modes, The lift of the tilting gyro is provided by the rotor and the wing. As the speed of the aircraft increases, the proportion of the total lift of the wing is gradually increased, and the lift proportion of the rotor is gradually reduced until the helicopter mode is completed. Fixed-wing mode of conversion, the wing provides the required lift aircraft, the rotor to provide a pull to overcome the resistance of the aircraft flight process [4-5]. In this paper, the general theory of the modeling of the Tilt tri-rotor UAV is given by modeling the power system of the tilt tri-rotor UAV with the positive triangular layout, and the research of the unmanned aerial vehicle The theoretical basis. Estimated Takeoff Weight Based on ission Load In the design process, the design of the tilt tri-rotor UAV will be based on the nature of the task, the task load to determine the relevant parameters, including the task load quality, life time T, and flight height H, cruise flight speed and many other design indicators. In the step of determining the take-off weight based on the mission payload, the weight of the mission load and the life time T are mainly considered. 17

2 Figure 1. Tilt tri-rotor UAV overall layout. The main steps for determining the take-off weight based on the weight of the mission load are as follows: 1) estimating the weight of the UAV power unit W based on the weight of the m mission load W p ; ) empirically determine the aircraft structure weight coefficient f e and estimated battery weight coefficient f b ; 3) Calculate the takeoff weight Wt according to the formula W t = ( Wp + Wm) /(1- fb - fe) ; 4) According to the take-off weight Wt of the tilting three-rotor UAV flight planning to be consumed by the energy E, with reference to the choice of battery energy density E e, the battery weight W b = ; e Wb 5) compare and estimate the weight coefficient f b of the battery, if equal, the Wt takeoff weight estimation is completed, if not equal to return to the second step to adjust the battery weight structure coefficient re-estimated until equal. Where in the power unit partial weight comprises the total mass of the motor, the electronic governor, the propeller and the pitch steering gear. UAV ain Parameter Calculation Aerodynamic Parameters of UAV UAV layout to determine the future, in order to accurately calculate the takeoff weight of UAV, the key is to know the weight of unmanned aerial vehicles, UAV battery weight to determine the need to fly in the course of its energy consumption to determine, and the energy is determined by the lift-up resistance of the UAV [6]. The polar curve of the aircraft is determined by equation (1), CD is the zero-lift drag coefficient and K is the induced drag coefficient. CD = CD + KCL (1) Zero-Lift Drag Coefficient. Aircraft in the course of the resistance of the source there are many, depending on the cause of resistance and whether or not with the lift, the resistance can be divided into zero-rise resistance and induced resistance. Zero rise resistance and UAV flight occurred in the process of victory is not directly related, which mainly includes the friction resistance and pressure resistance, which UAV zero-lift resistance coefficient can be expressed as: 171

3 S = () wet CD C fe S cef Among them, Swet is the aircraft as a whole wet area, Scef as the reference area, the general wing area, and the whole aircraft friction coefficient C :.58 C f =.455 / (logre) (3) Reference small unmanned aircraft, Reynolds number selection 4, the friction coefficient Cf is about Tilt tri-rotor UAV is different from the general fixed wing unmanned aerial vehicle, the need for the tail of the rotor to calculate the treatment. In the process of handling the tail pod, refer to [7], in its cruise stage, it is equivalent to a landing gear, C D =.1. So the whole aircraft of the zero-rise resistance coefficient can be expressed as: S C = C + C (5) wet D f D Scef Induced Resistance. The zero-drag resistance coefficient of the whole aircraft is obtained. To obtain the pole curve of the aircraft, it is also necessary to obtain the 1 aircraft induced resistance factor K. Induced resistance factor K =, where A is the Aπ e aspect ratio of the UAV. Since the tilt tri-rotor UAV uses a straight wing wing layout, for a straight wing aircraft, the Oswald efficiency factor e is:.68 e = 1.78(1.45 A ).46 (6) And then, the initial estimate of the aircraft pole curve. Different Flight ode Power System odel The tilt tri-rotor UAV have a total of three flight modes: the helicopter mode, the fixed wing mode and the transition mode between the helicopter mode and the fixed wing mode, which require consideration of the power requirements are mainly helicopter mode and fixed wing mode [8], so choose the helicopter mode and fixed-wing mode of the power system for mathematical modeling. Helicopter ode. In the helicopter mode, the tilt tri-rotor UAV is similar to the multi-rotor unmanned aerial vehicle, which provides all the lift required for the flight, ie the lift produced by the propellert G, where G is the weight of the unmanned aerial vehicle [9]. ( N ) ζ HN (7) xu sj T represents the total force generated by the three rotor blades, the UAV flight height characteristic coefficient H = N / N,ζ the propeller power transmission efficiency, N is the tilt tri-rotor UAV in the sea level and ( ) xu sj f N is the actual use of power in helicopter mode. Since the tilt tri-rotor UAV rotor uses a triangular layout, the center of gravity of the aircraft is at the center of the three rotors, the single rotor needs to bear the gravity T = G / 3. In the helicopter mode, the aircraft for low-altitude low-speed movement, in this condition, the air can be regarded as non-sticky in-compressible gas. According to Newton's second law, the rotor in order to obtain upward tension, you must apply downward force on the air. 17

4 According to the formula: 1 ρ p CT Ω R 16 ρ (8) CT 1 q 75ζ H i (9) m Ω R k p is the unit paddle load, q is the unit horsepower load, CT is the tension coefficient, ρ / ρ is the relative pressure, Ω is the propeller speed, R is the propeller radius, ζ for the power transmission efficiency. By simplifying the operation, the result is: G G 75 ρ q p = i ζ Hη i (1) N π R ρ change its expression form: N 3/ G (11) 33.5ζ HηD ρ ρ In the formula, N is the sea level to use power, small electric UAV flight height range for the high degree of feature coefficient H.9, power transmission efficiencyζ =.8, D for the propeller size, according to the integrated aerodynamic layout, fixed wing mode power requirements and propeller efficiency model select. In the helicopter mode, the tilting of the tri-rotor unmanned aerial vehicle hovering efficiencyη is related to the propeller being formed in the wing underneath, according to the literature [1-11], the tilted rotor 1 and the rotor is.7, the tail rotor 3 is.5. Then can get the total power N in helicopter mode: N = N 1 + N + N 3 (1) Fixed Wing ode. The tilt tri-rotor UAV is equivalent to a conventional fixed-wing unmanned aerial vehicle when flying in fixed-wing mode. According to a given index cruising speed Vc and maximum flight speedv max, calculate the constant power required to fly flat P: G P = DV = V (13) L / D In the fixed wing mode, the aircraft required lift all provided by the wing, the aircraft required lift is equal to the aircraft gravity, to meet the formula: L = Gg = qsw CL (14) 1 Where q is the dynamic pressure, q = ρv, W S is the wing area, and Gg CL =, qs according to the formula (1), CD can be obtained, then D = qsw CD, return to equation (13), by bringing different flight speed, can be obtained at the same flight speed, The required power. w 173

5 Propeller odel The tilt tri-rotor UAV fixed-wing mode is equivalent to double propeller aircraft, in order to cruise the state of energy efficiency to achieve the best, the need for mathematical modeling of the propeller [1]. The single single propeller in the cruise D state needs to provide tensiont =, the propeller efficiency diameter mathematical model is: η pro η pro V V = = n V + H 8T V + + V 6 π D ρ s (15) is the propeller efficiency, ns is the propeller rotates every minute. According to the tilted three-rotor UAV layout, the propeller must provide sufficient thrust over the entire flight speed range to meet the power requirements. At maximum flight speed, the maximum power demand of the propeller is greater than the maximum power required for the flat fly. At the same time, it is necessary to consider that the propeller has better performance in the UAV helicopter mode, considering the fixed wing mode Under the power demand, select the appropriate propeller size D is 5.4cm. Figure shows the example of the propeller diameter and efficiency of the curve. Figure. Propeller diameter-efficient curve. Example Combined with the previous analysis on the modeling of the tilt tri-rotor UAV (UAV) maneuvering system, the task and the key parameters of the unmanned aerial vehicle are given and taken into the example to complete the matching of the power system and the production of the unmanned aerial vehicle, And successfully carried out the test flight test to verify the correctness of this model. 174

6 Table 1. The key parameters of tilt tri-rotor UAV power system. Figure 3. The tilt tri-rotor UAV helicopter mode, fixed wing mode flight test. Conclusion In this paper, the mathematical model of the tilt tri-rotor UAV is given by mathematical modeling of the tilt tri-rotor UAV power system. The reliability and reliability of the model are verified by an example, which provides a basis for the design of the power system of the tilting rotor craft, which provides strong support for the overall parameter design of this type of UAV. References [1] Heng Chen, Xiao-yang Zuo, Yu-zhu Zhang.Study on the development of tilting rotor-craft technology [J]. Flight mechanics, 7, 3 (5-8). (In Chinese) [] Dayong Liu, Jia Liu. Summary of the development of offshore offshore unmanned aerial vehicles [J]. Flight issile, 14, 11 (54-6). (In Chinese) [3] in Xu. Study on the development and key technology of tilting rotor-craft [J]. Helicopter Technology, 3, (4-44). (In Chinese) [4] Yunyun Cao.Control Strategy for Tilt-Rotor Aircraft Trimming in Steady Level Flight [J].Journal of Nanjing University of Aeronautics and Astronautics,9, (6-1). (In Chinese) [5] Ugur Ozdemir, Yucel Orkut Aktas, Aslihan Vuruskan, Yasin Dereli. Design of a commercial Hybrid VTOL UAV System [J], Intell Robot Syst (14) 74: [6] Zhigang Zhang, Rongjun Dang, Yi Zhang, Heping Wang.Study on the Design ethod of UAV Takeoff Quality [J]. Aircraft Design, 5, 9, 3 (19-3). (In Chinese) [7] Weiji Li. Aircraft overall design []. Xi'an: Northwestern Polytechnical University Press, 4. (In Chinese) 175

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