"Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering"

Pourtakdoust, Seid H; Zare, Hadi; Bighashdel, Arian

doi: 10.1177/09544100221108316pmid: N/A

A novel integrated aeroelastic model of flapping wings (FWs) undergoing a prescribed rigid body motion is presented. In this respect, the FW nonlinear structural dynamics is enhanced via a newly proposed modification of implicit condensation and expansion (MICE) method that better considers the structural nonlinear effects. In addition, the unsteady aerodynamic model is also an extension of the widely utilized modified strip theory (MST) in which the flexibility effects are accounted for (MST-Flex). The integrated utility of the proposed generalized MICE and MST-Flex is demonstrated to be more realistic for elastic FW flight simulation applications. The prescribed rigid body motion is produced via a servo motor whose dynamics is also considered for the analysis. A special case study is also performed whose combined aeroelastic solution is determined and validated under a sinusoidal flapping motion. To this end, an experimental setup is designed and tested in order to validate the proposed integrated approach for aeroelastic modeling of FWs. There is very good agreement between the numerical and experimental results for elastic FW aerodynamics. It should be noted that the proposed integrated aeroelastic approach is readily adaptable to all kinds of elastic wings with arbitrary geometry and various combination of structural elements.

Lai, Anqing; Cheng, Han; Li, Meng; Pan, Jie

doi: 10.1177/09544100221113215pmid: N/A

High-altitude ice crystal icing of aero engine is a serious threat to flight safety. Previous studies on ice crystal icing focused on the influence of air flow on ice crystals, but ice crystals also affect the engine flow field, which is often ignored in the research on the influence of ice crystals on engines. Numerical simulation based on Eulerian method is adopted to realize the two-way coupling between the compressor air flow and the particles in this study. The approach is demonstrated using the NASA compressor stage 35. The changes of compressor and particle parameters with different inlet total water content, relative humidity, and median volume diameter are calculated and analyzed, and the influence of ice crystal on the compressor performance is studied. The results show that the variation of relative humidity has a great influence on the particle temperature, median volume diameter, and wet bulb temperature. Median volume diameter has a great influence on the melt ratio. The variation of total water content has little effect on particle temperature, total water content, median volume diameter, and wet bulb temperature. The particle parameters are affected by the flow field of the compressor. The parameters show that the icing is easy to occur at the leading edge of NASA stage 35 stator. By contrast, the overall compressor characteristics, after ice particle injection, the total pressure ratio, and isentropic efficiency of the compressor are increased without considering ice crystal accretion, and the chocking boundary and stall boundary are not affected.

Li, Xiaohua; Zhao, Chenxu; Lu, Bo

doi: 10.1177/09544100221108612pmid: N/A

Test management is a critical problem for in-time correction-based testability growth test. For the existing testability growth model, they are either too complex to be implemented in practice, or do not have the ability to draw a smooth test planning/projecting curve. This paper proposes a unified model for in-time correction-based testability growth test and presents its application on the test planning. Firstly, a simple model with only three parameters is developed, and its compatibility with the original Markov model is proved. The revised model only has three parameters, which can reduce the complexity of parameters estimation and increase the certainty of the test planning. Secondly, the paper incorporates the simplified transition probability model with the test cost model and studies the optimal test planning method with the minimum test cost criterion. To illustrate the efficacy of the proposed model, an application of the model to an attitude control system of a helicopter available in the open literature is given. The simulation demonstrates that the model and the method proposed in this paper are reasonable, and they are useful for effectively managing the testability growth test planning problem during system maturation.

Sandeepkumar, R; Mohan, Ranjith

doi: 10.1177/09544100221112724pmid: N/A

The advent of efficient numerical algorithms and powerful computing resources have made real-time optimization a reality. However, for systems like 6DoF aircraft, the problem remains challenging due to the complexity and fast dynamics of the system. Smaller optimization problems with fewer constraints can be obtained from a differential flatness-based optimization scheme. This paper proposes a flatness-based nonlinear model predictive controller (NMPC) for a 6DoF aircraft to improve computational time. However, it is difficult to tell in advance if flatness-based NMPC can outperform the simultaneous NMPC with many variables and constraints. This is because there is a trade-off between loss in convexity and an increase in nonlinearity with a dimension reduction. In addition, nonlinear optimization solvers like IPOPT can exploit the underlying sparse structure of the optimization problems from simultaneous NMPC to compute solutions efficiently. Hence, a comparative study between flatness-based and simultaneous nonlinear model predictive control is necessary to assess the computational performance. Results are presented with discussions on solve time, numerical conditioning, convergence, convexity, and solve success rates of the optimization problem. The discussions presented can be extended to other systems to study the effectiveness of flatness-based optimization in a systematic manner. In addition, pseudospectral knots are explored in the paper, which improves sparsity and numerical conditioning of flatness-based optimal control problems.

Farhangian, Farzan; Landry, Rene Jr

doi: 10.1177/09544100221113123pmid: N/A

An inertial navigation method augmented by Signals of Opportunity (SOPs) of three low earth orbit (LEO) constellations is presented. The downlink signal characteristics of the Iridium-NEXT, Orbcomm, and Globalstar LEO constellations are discussed. Furthermore, a tightly coupled integration model of the inertial navigation system and high-order LEO-SOP Doppler measurement model is designed. We presented a second-order measurement model of the LEO-SOP/INS integration using a second-order extended Kalman filter in which all the unknown states of the receiver and LEO satellites are estimated. The state parameters of the second-order EKF model are the position and velocity of both the receiver and the satellites, as well as the receiver’s orientation, the clock bias, and clock drift of the LEO satellites, and the constant bias of the Inertial Measurement Unit. An experiment is performed using a ground aerial vehicle equipped with a Multi-Constellation Software-Defined Receiver (MC-SDR). The Doppler measurements are provided by observing the downlinks from multiple satellites of the Iridium-NEXT and Orbcomm constellations. As well, the predicted measurement of a Globalstar satellite is used in the designed model. The results show the positioning accuracy of less than 10 m being achieved during a dynamic ground experiment, representing an 82% precision gain as compared against the regular single constellation EKF method.

Graffstein, Jerzy

doi: 10.1177/09544100221107725pmid: N/A

For solving the airplane-to-obstacle collision avoidance problem, two methods are necessary, that is, one for detecting a collision threat and the other one for synthesizing a safe manoeuvre avoiding threating obstacles. In the article, a method for detecting a threat of collision to obstacle was presented for the case of many obstacles moving within the neighbourhood of the airplane. Methods for optimal anti-collision trajectory synthesis and for proving the workability of such a result were proposed too. A solution of an optimisation problem, obtained by the swarm of particles optimization (PSO) was used for trajectory synthesis. A form of quality index was proposed for this task and the analyses of its behaviour for several values of weighting factors were presented. Results of simulations of flight along an optimal, anti-collision manoeuvre trajectory proved that such a manoeuvre is workable.

Wu, Zeyan; Dong, Shaopeng; Yuan, Mei; Cui, Jin; Zhao, Longfei; Tong, Chengbin

doi: 10.1177/09544100221113198pmid: N/A

As one of the key technologies in the development of Unmanned Aerial Vehicle (UAV), the path planning method has an intuitive impact on the real-time performance of UAV. Most existing path planning algorithms have drawbacks in global optimization ability or optimization speed, and cannot meet the requirements of practical applications. To improve the effectiveness and practicability of the path planning algorithm for UAV obstacle avoidance, this paper proposes the Rotate Artificial Potential Field (R-APF) method based on the traditional artificial potential field method. By introducing a new potential field function and stimulating rotating repulsive force, the R-APF solves the problems of local minimum as well as inaccessibility to targets near obstacles, respectively. Convergence of the algorithm is discussed to demonstrate the feasibility of R-APF. This paper also designs and implements algorithm feasibility verification experiments, obstacle shuttle experiments, as well as running time, and efficiency comparison experiments. In addition, the improved Visual-Inertial Navigation System obstacle detection algorithm is introduced to carry out physical verification experiments. Theoretical proof and experimental results show the proposed R-APF method has higher obstacle avoidance capability, shorter running time, and higher success rate compared to other algorithms, and is promising in practical application.

Saroha, Sagar; Sinha, Sawan S

doi: 10.1177/09544100221108609pmid: N/A

The partially averaged Navier–Stokes (PANS) methodology has emerged as a viable bridging method of turbulence computations. Partially averaged Navier–Stokes methodology allows the user to implicitly choose the filter cut-off seamlessly in the inertial sub-range of motion. In past, most PANS simulations have been performed using the linear eddy viscosity closure for the unclosed turbulent stresses. Recently, evaluation of the advantages of higher order eddy viscosity closures with the PANS methodology has also been initiated. With our motivation to make further progress in this direction, this study presents an evaluation of PANS methodology wherein the turbulent stresses are modelled involving closures up to the cubic products of the resolved strain-rate and the rotation-rate tensors. After appropriately adapting a popular Reynolds-averaged Navier Stokes cubic closure for the PANS paradigm, an extensive evaluation of the method is performed in the flow past a heated sphere at a Reynolds number of 10,000. Time-averaged PANS predictions of surface-related as well as wake-related quantities are compared against available experimental, direct numerical simulation as well as large eddy simulation results. Indeed, very significant improvements are demonstrated by the PANS methodology in conjunction with the cubic eddy viscosity closure when compared to the corresponding predictions of the PANS methodology using a linear or even a quadratic eddy viscosity closure. This study demonstrates the promising augmentative ability of the higher eddy-viscosity to the PANS framework in performing improved simulations of the separated flows.

Zhang, Chao; Xi, Zhaojun; Li, Renfu; Kong, Ningliang

doi: 10.1177/09544100221110655pmid: N/A

Direct numerical simulations were performed to investigate an active control strategy for supersonic (Mach 1.8 and 2.2) flows past a rectangle cavity with a length-to-depth ratio of 4. A steady mass injection is applied upstream of the cavity as the active control technique. The pressure oscillations are significantly suppressed by two mechanisms: (1) thickening and lifting of the cavity shear layer to alleviate downstream impingement with the cavity trailing edge and (2) weakening of the cavity shear layer instability. When the initial boundary layer thickness of the supersonic cavity flow is relatively small, a stronger mass injection leads to increased cavity shear layer thickening and uplift, increased weakening of the shear layer instability, and higher suppression of the pressure oscillations. When the Mach number equals 1.8, the dominant flow mode changes from the Rossiter II mode to the Rossiter III mode under active control, which is detected by the dynamic mode decomposition. However, the mode transition under active control substantially differs if the initial boundary layer thickness is relatively large, for which the pressure oscillation suppression controlled by the high-velocity upstream mass injection is not better than a low-velocity injection, owing to a higher shear layer instability. Mechanism (2) listed above is therefore more important than mechanism (1).

Tarighi, Reza; Mazinan, Amir Hooshang; Kazemi, Mohammad Hosein

doi: 10.1177/09544100221109976pmid: N/A

This paper presents a novel speed control method for an unmanned flight system. A Polytopic Linear Parameter Varying model is generated by linearization of the nonlinear dynamic model around several trim points. As a novelty of this paper, an Integral action over the tracking error is added to a conventional state-feedback to form the proposed control law. Augmenting the proposed control action to the system dynamic, the proposed control law is reassigned as a common state-feedback control problem. An attenuation level for the tracking error under external disturbances is guaranteed by solving the related linear matrix inequalities to compute the control gains. In the end, the designed controller has been implemented for different scenarios in order to maintain the speed in different modes with the ability to control the longitudinal, Lateral, and altitude velocities simultaneously. The simulation results show the effectiveness of the proposed control against the system uncertainties, external disturbances, and the interactions between different channels.