Xiaohui Wei

Nanjing University of Aeronautics & Astronautics · Department of Aircraft

Multi-input multi-output random vibration control combined with limit channels is a commonly used experiment scheme in dynamic environmental testing. This paper proposes a limit control strategy for multi-shaker random vibration tests. Compared to the traditional limit control method, the presented work can alleviate the undertesting phenomenon. Th...

In continuation of our previous work on nonlinear stability analysis of trimmed isogeometric thin shells, this contribution is an extension to dynamic buckling analyses for predicting reliably complex snap‐through and mode‐jumping behavior. Specifically, a modified generalized‐α time integration scheme is used and combined with a nonlinear isogeome...

During aircraft braking, the change of ground adhesion forces can cause forward and backward vibration of the landing gear, and the performance of the brake disc may exacerbate this vibration. In order to solve this problem, a rigid–flexible coupling dynamic model of a two-wheel strut landing gear considering the friction characters of brake discs...

Rotorcraft Unmanned Aerial Vehicles (UAVs) often need to take off and land under complex working conditions. The rugged terrains may cause the UAV to tilt during takeoff and landing and even cause rollover and other accidents in severe cases. In this paper, a new four-legged landing gear of multirotor UAVs with a passive cushioning structure is des...

The carrier-based aircraft landing and arrest process is complex and nonlinear, and includes the coupling effect between the aircraft and the arresting system. This process has many uncertain factors, which create difficulties in landing safety analysis. To improve the accuracy and effectiveness of landing safety analysis, this paper presents some...

The probabilistic reachability problem, which involves the computation of probabilistic reachable sets, is studied for nondeterministic systems. In the existing works, the system evolution initialized from the probabilistic reachable set is required to reach the target set with a certain probability in a given time horizon. In this paper, the defin...

View Video Presentation: https://doi.org/10.2514/6.2022-3644.vid An aircraft may veer off the runway and severe ground directional instability accidents may take place resulting from asymmetric disturbance during a taxiing process. Thus an aircraft ground taxiing nonlinear dynamic model is established in MATLAB/Simulink and the numerical continuati...

In this paper, the generation mechanisms of standing waves on aircraft tires are discussed by comparing the time-domain model and FEA model. Unlike passenger car tires, aircraft tires accelerate to landing speed sharply when the airplane lands. According to the tire structure, the detailed finite element model of the aircraft tires is established i...

Artificial neural network has been several applications on fatigue crack, with prediction on fatigue crack growth life often serving as milestones. A typical difficulty in predicting the life curve of fatigue crack growth is the retardation of crack growth caused by the overload effect. Overload retardation, resulting in the lack of experiment data...

Rapid launch is one of the key indicators of UAV swarm operations, and one of the key decisions that determines the ultimate success of launch system development is the choice of its product architecture. The high-definition design structure matrix (HDDSM) method is introduced to model the product architecture of a UAV launch system, which reduces...

The level set method is a widely used tool for solving reachability and invariance problems. However, some shortcomings, such as large amount of storage space consumption and the difficulty of constructing terminal conditions for solving the Hamilton–Jacobi partial differential equation, limit the application of the level set method in some problem...

Rollout is an inevitable phase of realizing horizontal landing for an equipped–skid aircraft; therefore, one should pay attention to the safety of the entire rollout process. The research presented herein analyzes the effects of the landing gear layout on the safe rollout envelope, which is the set of all states where the aircraft can remain in the...

This paper describes the design and flight test of the control system of a novel octocopter with new topology to improve aerodynamic performance and efficiency. The article analyzes the advantages of the new configuration and analyzes the feasibility of the control method which can ensure fault-tolerant control when one rotor of the aircraft stops...

The carrier-based aircraft landing and arrest process is complex and nonlinear, and includes the coupling effect between the aircraft and arresting system. It has many uncertain factors, which lead to difficulty in the reliability analysis. To make the reliability analysis more accurate and effective, this paper presents some studies. Taking a cert...

The paper deals with straight-line path-following control design for the aircraft equipped with skid landing gears. First, a simple yet accurate on-ground aircraft model is established, which takes into account the effects of the aerodynamic and ground forces. To improve the directional stability of the aircraft during the roll-out phase, a novel s...

In this paper, we generalize the definition of reachable set. The classic definition of reachable set is a set of system states that can be driven into the target set within a given time horizon. Sometimes, the concern of researchers is not the time consumption but some other form of cost of driving the system state toward the target set. Under thi...

Sidestay lock mechanism is an important part of landing gear system, and the locking performance can be analyzed based on changes in its stability. However, during numerical continuation analysis of fully-rigid dual-sidestay landing gear without clearance, it has been found that the appearance of bifurcation points does not necessarily imply that b...

The probabilistic reachability problems of nondeterministic systems are studied. Based on the existing studies, the definition of probabilistic reachable sets is generalized by taking into account time-varying target set and obstacle. A numerical method is proposed to compute probabilistic reachable sets. First, a scalar function in the state space...

A dual-sidestay landing gear is prone to locking failure in the deployed state due to the restriction of movement between two sidestays. However, the principle of its locking movement still remains unclear. The present study is aimed at investigating the synchronous locking performance of the dual-sidestay landing gear based on the singularity and...

A novel method for computing reachable sets is proposed in this paper. In the proposed method, a Hamilton-Jacobi-Bellman equation with running cost function is numerically solved and the reachable sets of different time horizons are characterized by a family of non-zero level sets of the solution of the Hamilton-Jacobi-Bellman equation. In addition...

A novel method for computing reachable sets is proposed in this paper. In the proposed method, a Hamilton-Jacobi-Bellman equation with running cost functionis numerically solved and the reachable sets of different time horizons are characterized by a family of non-zero level sets of the solution of the Hamilton-Jacobi-Bellman equation. In addition...

An improvement of Q-learning is proposed in this paper. It is different from classic Q-learning in that the similarity between different states and actions is considered in the proposed method. During the training, a new updating mechanism is used, in which the Q value of the similar state-action pairs are updated synchronously. The proposed method...

Air cushion landing system (ACLS) can help airplane realize amphibious take-off and landing. Even so, vehicle with the ACLS is more susceptible to uncertainties such as crosswind, unmolded dynamics and high nonlinearities than other take-off/landing methods, resulting in difficulty escalation for the tracking deviation correction (TDC) control. In...

A novel actor-critic algorithm is introduced and applied to zero-sum differential game. The proposed novel structure consists of two actors and a critic. Different actors represent the control policies of different players, and the critic is used to approximate the state-action utility function. Instead of neural network, the fuzzy inference system...

Double-cavity shock absorber with high-pressure piston is the core component of the nose landing gear of the carrier-based aircraft, and its fast-extension performance seriously affects the safety of the catapult-assisted takeoff. The design of a carrier-based aircraft in our country is carried out based on the traditional method of fast-extension...

Level set method is a widely used tool for solving reachability, viability and invariance problems. However, some shortcomings, such as the difficulties of handling dissipation function and constructing terminal condition for solving the Hamilton-Jacobi partial differential equation, limit the application of level set method in some problems with n...

Directional stability during the roll-out phase is crucial to the safety and reusability of the aircraft. Because of the mechanical properties, the wheel-skid aircraft is more prone to produce course instability. To address this issue, the taxiing safe set of the wheel-skid aircraft is discussed based on the reachability theory. A dynamic model of...

This paper investigates the landing planar movement control (LPMC) problem of an amphibious airplane which is susceptible to uncertainties such as the gust, the unmodeled dynamics and the strong couplings. The uncertainties can bring negative effects for the airplane acting in forms of persistent influences and sudden changes, damaging system stabi...

A new combined electric anti-skid braking system of a high-speed unmanned aerial vehicle is designed to improve the stability and to reduce the system sensor noise. An electric anti-skid braking mechanism model considering the sensor noise effect is built in MATLAB/Simulink. The stability of a slip ratio braking system and a deceleration braking sy...

A loss of ground directional stability can trigger a high-speed Unmanned Aerial Vehicle (UAV) to veer off the runway. In order to investigate the combined effects of the key structural and operational parameters on the UAV ground directional stability from a global perspective, a fully parameterized mathematical high-speed UAV ground nonlinear dyna...

Based on the modal coupling theory, the rotor and stator contact stiffness and axial relative velocity are considered to build an electric aircraft brake dynamic system model in this study. Both the complex modal analysis and transient dynamic analysis methods are used to study the aircraft brake squeal performance and vibratory mechanism. The unst...

Joint clearances inevitably affect the kinematic accuracy and robustness of landing gear retraction mechanisms. However, the complexity and uncertainty of the clearances lead to difficulty in establishing mathematic models and analyzing effects. In the interest of assessing the clearance effects on the kinematic accuracy of landing gears, an integr...

The hinge clearance and rotation axis deviation of aircraft landing-gear retraction mechanism are unavoidable due to factors, such as manufacture, assembly, wear, and wing deformation. Such negative factors affect the dynamic response of the mechanism itself, which is more serious for spatial mechanisms. To study this effect, both numerical and exp...

The bifurcation analysis method is used to study the high-speed unmanned aerial vehicle (UAV) dynamics and directional stability during the steering process on the ground. A UAV nonlinear ground taxiing dynamic model is built considering the effects of large-angle-steering motion on the interactive aerodynamic forces. The single-parameter bifurcati...

To design and analyze a hook lock mechanism for a certain type of aircraft landing gear, numerical continuation and bifurcation theory are employed to study the performance of the lock mechanism in this paper. First, dynamic and static models of the hook lock mechanism are created separately, and by analyzing the locking and unlocking processes of...

The work reported in this paper concentrates on the design and application of an electric ground control system combining the braking and steering mechanisms on a small unmanned aerial vehicle. A virtual prototype of a small unmanned aerial vehicle is built with a multibody dynamic software LMS Virtual.Lab Motion. An electric anti-skid braking syst...

To improve the landing performance of a near-space manned capsule under various landing conditions, a novel landing system is designed that employs double chamber and single chamber dampers in the primary and auxiliary struts, respectively. A dynamic model of the landing system is established, and the damper parameters are determined by employing t...

The full nonlinear equations of an unmanned aerial vehicle ground taxiing mathematical dynamic model are built based on a type of unmanned aerial vehicle data in LMS Virtual.Lab Motion. The flexible landing gear model is considered to make the aircraft ground motion more accurate. The electric braking control system is established in MATLAB/Simulin...

The ability to perform vertical takeoff and landing reliably and safely is of great concern for a near space travel lander carrying passengers. Oblique and uneven terrains can severely limit the degree of landing safety, so mission adaptive landing gear is designed and analyzed for its function of automatic adjustment before touchdown. The legs of...

Assembly tolerance design for spatial mechanisms is a complex engineering problem that involves a highly nonlinear dimension chain equation and challenges in simplifying the spatial mechanism matrix equation. To address the nonlinearity of the problem and the difficulty of simplifying the dimension chain equation, this paper investigates the use of...

In this paper, the fault analysis of an aircraft nose landing gear’s emergency lowering was conducted with a cosimulation method. The simulation was aimed at studying the dynamic response characteristics of landing-gear retraction/extension. Moreover, the equations of the mechanical and hydraulic system were derived and analyzed so as to acquire th...

In order to improve the efficiency and accuracy of soft-landing dynamic calculation of lunar lander, this paper proposed a new soft-landing dynamic model with seven free degrees and the inertia force was also taken into consideration during the landing process. The force condition of lander during soft-landing was investigated; moreover dynamics an...

A study was conducted to demonstrate improved model of landing-gear drop dynamics. The improved model of the half-axle landing-gear drop dynamics was constructed to investigate the characteristics of shock-strut binding during landing process. The structural configuration of the main landing gear of the unmanned aircraft was a kind of half-axle sho...

Landing gear shock strut binding problem occurred during an unmanned aircraft's flying test. The half-axle main landing gear of the unmanned aircraft was chosen to analyze the influences of shock strut flexibility on drop dynamics. The friction force was modeled based on the half-axle configuration and taking shock strut flexibility into account. D...

Due to the offset of wheel axle center, the forces acting on the shock strut of landing gears are different from those with symmetrical wheel configuration. To solve the binding problem which occurs in the flight test of an unmanned aircraft, the main landing gear of the aircraft was chosen to analyze its drop dynamics. The drop dynamics was modele...

During the catapult launch of the carrier-based aircraft, complex dynamics problems exist because of the large load and short time, as well as the movement of the carrier and the airflow disturbance. The research status of the carrier-based aircraft catapult launch dynamics are reviewed, including nose tow catapult dynamics, rapid extension dynamic...

Based on the piezoelectric effect and magnetorheological technology, a parameter adaptive shock absorber was designed. Considering the practical working conditions of landing gear, mathematical model of the parameter adaptive shock absorber was built. Then on the basis of LMS Imagine.Lab AMESim software, the whole combined simulation model of self-...

The vibration of the nose landing gear caused by the sudden discharge of holdback load during catapult launch of a carrier-based aircraft could bring serious fatigue problem to the structure and airborne equipment. With the purpose to solve the vibration problem, a dynamics model of catapult launch is established. An anti-vibration holdback device...

This paper builds dynamical models and hydraulic system models of retraction/lowering of some regional aircraft nose landing gear respectively based on the software LMS VL motion and AMESim. The simulation analysis result was proved to be credible by checking with that of ground test. The peak oil return pressure with the critical damping force can...

The vibration of a nose landing gear caused by the sudden discharge of holdback load during the catapult launch of a carrier-based aircraft could bring serious fatigue both to the structure of the launch and the airborne equipment. To investigate the vibration and seek a solution, a dynamic model of the catapult launch is established. The load of t...

The new conception of landing region has been introduced and analyzed the behavior of landing impact based on the model with a landing region. A landing region is a mechanical system that is built on a runway. The parameter calculation show that an increase in the damping coefficient of the supporting damper results in an increase in the first maxi...