Aircraft Braking System Research Articles

The influence of disks deformation on the stability analysis of an aircraft braking system

Friction-induced vibration emanating from aircraft braking system is a key issue in the design phase, due to the significant damage it can cause to the brake structure. Although the problem of unstable vibrations in aircraft braking systems has been studied by a number of researchers, the suitability of the mechanical modeling strategy for predicting instabilities remains an open problem. The need for relevant numerical models is therefore essential in order to be as predictive as possible during the design phase. Preliminary studies must therefore be carried out to validate or invalidate the modeling hypotheses traditionally used. Indeed the stability analysis of an aircraft braking system is performed in order to study a low-frequency instability. An industrial model is used, hence reducing the number of degrees of freedom (DoF) is of utmost importance in order to have reasonable computation times. When studying low-frequency phenomena, this can be achieved by neglecting the deformations of the disks. However, no current study has shown that this hypothesis is realistic. So the aim of this paper is to assess the effect of the rigidity hypothesis on the results predicted by the stability analysis. In order to do so, the stability analysis results of a model with rigid disks and one with non-rigid disks are compared, with a particular attention on the main instability phenomenon. It is found that considering rigid disks has a very limited influence on the frequency of the low-frequency eigenmodes, but it over-predicts the real part of the unstable eigenmode. Besides, a component mode synthesis (CMS) technique is shown to reduce significantly the size of the non-rigid disks model while ensuring a satisfying precision regarding eigenmodes prediction.

Operational reliability assessment of complex mechanical systems with multiple failure modes: An adaptive decomposition-synchronous-coordination approach

To effectively perform Complex Mechanical Systems Operational Reliability Assessment (CSORA) with multiple failures, the Adaptive Decomposition-Synchronous-Coordination Approach (ADSCA) is proposed by integrating Decomposition-Synchronous-Coordination strategy, adaptive modeling technology, surrogate model and multi-objective reliability assessment theory. In which, the main problem is decomposed into related sub-problems using a Decomposition-Synchronization-Coordination strategy, with sub-models coordinated to achieve synchronous mapping between multiple variables, thereby enhancing efficiency in large multi-subsystem problems. The adaptive modeling technique is adopted to construct a series of interrelated sub models based on the surrogate model as the basis function, improving performance. A multi-objective reliability assessment theory is adopted to achieve CSORA under multiple fault modes, where multiple weak links are integrated to comprehensively evaluate the reliability of complex systems. The significance of the ADSCA lies in its ability to manage complexity, enhance scalability, and improve the accuracy and efficiency of reliability assessments in complex mechanical systems. To demonstrate the effectiveness of the proposed approach, two illustrative examples are used. This includes approximation and probability analysis of nonlinear functions that exhibit multiple responses, as well as reliability analysis of temperature in civil aircraft braking system. The study can provide theoretical reference for the reliability evaluation of multi-failure operation in complex mechanical systems.

Knowledge embedding synchronous surrogate modeling for multi-objective operational reliability evaluation of complex mechanical systems

To effectively assess the multi-objective operational reliability of complex mechanical system, the concept of Knowledge Embedding Surrogate Modeling (KeSM) is proposed by integrating Knowledge-based Decomposition-Coordination (K-DC) strategy, Knowledge-based Parameter Decomposition (K-PD) strategy, and the surrogate model. In this concept, the K-DC strategy is used to decompose a complex problem into several smaller sub problems, coordinating outcomes from the bottom-up; the K-PD is applied to decompose complex parameters into two parts: associated trends and local fluctuations; the surrogate model is adopted to establish the mapping relationship between input and output. Under this concept, the Knowledge Embedding Synchronous Surrogate Modeling (S-KeSM) multi-objective operational reliability evaluation method is developed by combining linkage important sampling technique and synchronous modeling thought with KeSM concept. In addition, an engineering case (civil aircraft braking system temperature with multi-failures) is employed to validate the proposed method. Through comparison and validation with multiple methods, the results show that the proposed method has significant advantages in analysis accuracy and efficiency. This study can provide theoretical references for the multi-objective operational reliability evaluation of complex mechanical systems.

Simulation of the landing situation of an aircraft and the problems of diagnosing anti-skid devices

Safety is ensured, including the safe landing of the aircraft. A short landing run without a skid is achieved by the necessary preparation of the runway, a serviceable braking system, anti-skid automation and take-off and landing devices of the aircraft. Standard operation of anti-skid automatics should be able to cope with constant non-linearity of movement and atmospheric interference on the surface of the runway, as well as adjust the wheel slip coefficient to ensure reliable operation of the braking system. The need to develop technical solutions in the field of expanding the operational capabilities of diagnostic tools for anti-youth automation of the aircraft braking system is determined by regular aviation incidents, related to failures of anti-skid devices, including their incorrect setting before installation on the aircraft landing gear wheel, which leads to serious consequences – increased wear of the wheel tire surface and its possible destruction, including an emergency landing due to loss of control over the aircraft. The purpose of the work is to simulate the youth situation of the aircraft during landing, to study the problem, to increase the efficiency, reliability of the results of diagnosing devices and automata of the aircraft braking system. This article discusses the main external and operational factors affecting the dynamics and nature of the aircraft's run along the runway, the model of aircraft movement with the influence of aerodynamic forces on it, the model of tire friction on the ground, and also proposes a method for diagnosing anti-youth automation of the aircraft braking system.

Brake-Induced Landing Gear Walk Vibration Analysis and Suppression Method Research

During aircraft braking, brake-induced frequent wheel slippage may cause coupling vibration between the antiskid brake system and landing gear. Brake-induced longitudinal coupled vibration is also known as “gear walk” vibration. Gear walk vibration not only reduces the structural life of the landing gear but also impairs the efficiency of the aircraft braking system. This paper focuses on the landing gear walk vibration mechanism and suppresses the method by modifying the antiskid brake control law. Firstly, a comprehensive multiwheel landing gear walk vibration model is developed. This model describes not only the longitudinal and vertically coupled vibration characteristics of the landing gear but also the dynamics of the aircraft braking system and the fuselage. Secondly, by simplifying the landing gear walk to the transverse vibration of a cantilever beam with a tip mass, the landing gear walk vibration mechanism is revealed in the frequency domain. Finally, a method to suppress landing gear walk vibration by modifying the pressure-bias-modulated (PBM) antiskid braking control law is proposed, which can solve the serious landing gear walk vibration problem caused by the conventional PBM control law. Simulation and experimental results show that the proposed method can suppress the landing gear walk vibration while improving braking efficiency.

Adaptive Nonhomogeneous Super-twisting Sliding Mode Control for Aircraft Braking System With Disturbance Compensation

Adaptive Nonhomogeneous Super-twisting Sliding Mode Control for Aircraft Braking System With Disturbance Compensation

Antidisturbance Slip Ratio Algorithm of Aircraft Braking System Based on On/Off Valves

A safe and high-efficiency braking process is the primary consideration for the aircraft braking system. The traditional servo valve is prone to blockage, which can cause serious safety accidents. Based on the analysis of the operation principle of the braking system, a safer aircraft braking system based on an on/off valve is proposed, which uses a normally open valve as the downstream valve. The braking system based on on/off valves has problems such as fluctuating pressure, harsh working conditions, and strong nonlinearity of the system. An algorithm with a strong antidisturbance ability and high braking efficiency is proposed to solve the above three problems. The algorithm typically consists of two main components: outer and inner loops. The outer loop uses the active disturbance rejection control, and the inner loop adopts the segmented nonlinear predictive pressure regulation algorithm with compensation. The outer loop can compensate for the internal uncertainty and external disturbance of the system. The inner loop can compensate for the flow rate during the closing process of the on/off valve to ensure the pressure regulation effect and the life of the on/off valve. The experimental results show that the proposed algorithm has a strong antidisturbance ability and high regulation precision. The braking distance of the algorithm can be reduced by 5.48–15.15% under three different working conditions, which significantly improves the braking efficiency of the aircraft.

Development of aircraft brake system

Aircraft wheel braking system is a subsystem with relatively independent function. Its function is to bear the aircraft's static weight, dynamic impact load and absorb the aircraft landing kinetic energy. Its performance directly affects the aircraft's rapid response, sustained combat capability and other overall performance. The aircraft braking system developed from the early mechanical inertia antiskid system to the electronic antiskid system, which is widely used today, has experienced a long history. In this paper, the development of aircraft brake system is reviewed briefly, and the present situation and development direction of domestic aircraft brake system are introduced emphatically.

An aircraft landing gear walk suppression method based on runway identification

The main landing gear walk is a longitudinal fore and aft movement of the strut caused by the brake system, and usually the vibration frequency does not exceed 10Hz. Gear walk is not only detrimental to the structural safety of the landing gear but also impairs the aircraft braking system's efficiency, so this vibration must be suppressed. Conventional anti-skid braking system (ABS) cannot recognize the friction characteristics of the tires and the road, so the tire-road friction changes drastically, which is the direct reason for gear walk. To address this problem, this paper first proposes a runway identification method to determine the optimal slip ratio for different runways, thereby achieving efficient anti-skid control and avoiding drastic changes in tire-road friction. A common anti-skid braking algorithm used in aircraft today is the pressure-bias modulation (PBM) algorithm, which is a rule-based deceleration-rate type of anti-skid algorithm. To solve the problem of landing gear vibration caused by unstable brake pressure of PBM, this paper proposes a slip-ratio based antiskid control method based on the super twist algorithm (STA). We constructed a simulation model in MATLAB/Simulink and conducted simulation tests, and the simulation results proved that the gear walking suppression method is effective.

A Research of High-Precision Pressure Regulation Algorithm Based on ON/OFF Valves for Aircraft Braking System

The aircraft braking system is a critical system used to slow down and stop the aircraft. Typically, the aircraft braking system usually uses the electro-hydraulic pressure servo-valve (EHPSV) to regulate the braking pressure of the aircraft. However, the pilot stage of EHPSV which has very precise orifice is easy to be blocked and leads to terrible fault. The <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> / <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> valve is robust to oil contamination and has better stability, but it is challenging to achieve high-precision pressure regulation. In order to guarantee the braking efficiency of aircraft, a high-precision pressure regulation algorithm is required. In this study, a algorithm with <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> / <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> valve array unit is studied to optimize the pressure regulation performance. The characteristics of the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> / <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> valve under different actuation times and pressures are derived. Based on this characteristics, a novel algorithm which can predict the required number of <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> / <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> valves and actuation time obtained by the unknown input state observer. Then the proposed algorithm is validated both by simulations and experiments. The results show that the proposed regulation algorithm in this study can achieve high-precision pressure regulation for aircraft braking application, which the regulation precision is better than 0.2 MPa, and the overshoot is less than 2.5%.

Design and validation of scalable PHM solutions for aerospace onboard systems

In recent years, Prognostic &amp; Health Management (PHM) has become a topic of strong interest in the aerospace domain. Health assessment and remaining useful life estimation for on-board systems provide several advantages, mainly related to the increased analysis capabilities and the reduction of maintenance interventions (and, consequently, of operating costs). For this reason, it is of interest for the aerospace industry to identify and define efficient strategies both for the introduction of native PHM capabilities in new generation on-board systems and for the retrofit of existing ones. This paper proposes a strategy for the scalable deployment of PHM techniques for on-board systems, with particular focus on edge computing capabilities. Different reference scenarios (ranging from cloud-based processing to local-only processing) are presented, and an edge-focused PHM architecture is discussed in detail, with the relative challenges addressed. The design and validation of proposed edge-based solution is described, with specific reference to its support for an existing data analytics framework. The solution is then assessed against a reference aerospace use case involving a representative aircraft braking system, focusing on computational aspects to highlight the compatibility of the proposed deployment strategy with efficient on-board computations.

Experimental and Analytical Investigation of Aircraft Brake Pad Material Composition

In the field of aviation industry, the aircraft braking system serves for ground taxing operation, ability to hold the aircraft at full static run-up and to stop the aircraft during landing. As usage of braking system increases, the frictional parts of the braking system undergo wear when it contacts with the rotor disc. To optimize the reliability of brake pads, finding suitable material is essential. This work is carried out to make a better frictional material with superior mechanical properties to sustain the environment. Identification of suitable composition was found satisfactory with help of adding and removing the set of constituent materials. Six sample brake pads with different materials and numerous compositions were manufactured through the powder metallurgy process. The necessary machining operations were performed to get a required shape. Theoretical calculations and analysis were done to establish the enhanced mechanical properties including wear and hardness. It was observed that samples 1 and 3 have better wear resistance and wear rate for different loading conditions.

Effect of cooling rate on C92900 bronze microstructure and properties

In the mechanical engineering, antifriction tin bronzes are used for the manufacture of friction parts. For example, the C92900 bronze has found use in aircraft braking system components. One of the ways to improve the properties of leaded tin bronzes is to increase the cooling rate during solidification. This paper studies the effect of the cooling rate and changes in the content of alloying elements within the limits established by the C92900 bronze industry standard OST 1 90054-72. In order to provide different cooling rates, the prepared alloys were casted into molds made of resin-bonded sand, steel and graphite with cooling rates 0.4, 5.0, and 14.6 °C/s, respectively. The influence of the cooling rate and the bronze composition on the freezing range, macrostructure, microstructure, thermal conductivity, mechanical, and tribological properties were investigated. Differential thermal analysis demonstrated that the upper-limit alloying of C92900 bronze leads to a decrease of the solidus temperature by 40 °C, which should be considered during deformation processing and heat treatment. An increase in the cooling rate during C92900 bronze ingot solidification provides a significant grain refinement and changes the amount, size and morphology of phases. For example, in case of metallic and graphite mold casting, the size of lead particles decreases, and its circularity increases. The change in the Sn content within the range established by the industrial standard has a significant effect on the γ-(Cu,Ni)3Sn intermetallic phase fraction. The increase in the cooling rate has no significant effect on the C92900 bronze thermal conductivity but increases hardness by 30 HB as well as cooling rate and yield strength and ultimate tensile strength. Wear tests carried out in accordance with the «shaft – partial insert» scheme in a kerosene medium using a steel counterbody showed that an increase in the cooling rate during solidification leads to an increase in the bronze wear rate from ~0.4·10–8 to ~1.2·10–8. The change in the bronze composition within the industrial standard range has practically no effect on the wear rate but leads to a slight increase of the coefficient of friction.

Chattering Suppression Fast Terminal Sliding Mode Control for Aircraft EMA Braking System

The performance of the electromechanical actuator (EMA) in the aircraft braking system suffers from the system’s nonlinear characteristics, whereas the robust control can contribute to the improvement of tracking precision in its servo system. In this article, a chattering suppression fast terminal sliding mode (FTSM) control strategy with an embedded nonlinear disturbance observer (NDO) is proposed for the EMA braking system, which can retain the fast convergence characteristic of the classical FTSM and guarantee the system converges to equilibrium point timely. Moreover, the singularity problem of the classical FTSM control is resolved through the well-designed sliding mode manifold. The NDO is designed to estimate the uncertain factors online, including time-varying parameters, external disturbance, and unmolded dynamics of the EMA system. By applying the compensation terms into the control law, the proposed control strategy can alleviate the chattering problem and improve system stability. To verify the performance of the proposed control strategy for EMA, wheel braking tests are conducted under various conditions regarding the type of runway and failure cases. The results indicate that the proposed control strategy can guarantee the servo performance, the control precision, and the response speed of the EMA servo system.

Evaluating the parametric, semi-parametric and nonparametric models for reliability in aircraft braking system

It is assumed that the lifetime of a system is a random variable valued based on a probability model and reliability studies with a system as a function of time. In this study, by multi-layers and hierarchical coding, we initially recognize the common operations and then, considering the sources likely to cause a crash, the crash center will be detected followed by estimating the structure of reliability of model. In this study, the aircraft wheel braking system has been broken down to its existing sub-systems and finally a reliability engineering model has been provided for wheels braking system and it has been estimated using existing methods whether nonparametric, semi-parametric and parametric approaches based on attrition and accelerated attrition. Then, among provided models, the most suitable model with least risk of square root of error has been fitted for studied data.

Study on modal characteristics and vibration reduction of an aircraft rotor–stator brake-induced squeal system

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 unstable vibration modes indicate that the out-of-plane vibration plays an important role and the feed-in energy is larger than the output energy in the brake rotor–stator module so that brake squeal takes place. Then the influences of the contact stiffness, friction damping and frictional coefficient on the brake squeal system are carried out, laying the foundation for the three proposed vibration suppression methods. Results show that the coefficient negative-slope condition will intensify the vibration. Also, a linear relationship between the squeal factor and the frictional coefficient is obtained to provide a guidance to predict squeal stability under more conditions. Vibration reduction design shows that adding a damping layer to the brake mechanism and chamfering the edge of braking stators both can reduce brake squeal effectively, while slotting braking stators is invalid in aircraft braking system.

Design for System Safety Analysis of the Aircraft Braking System Having Normal and Emergency Wheel Braking

Design for System Safety Analysis of the Aircraft Braking System Having Normal and Emergency Wheel Braking - written by Rolwyn Marian Cardoza , Dr. M. Krishna published on 2020/07/06 download full article with reference data and citations

Identification of the heat flux generated by friction in an aircraft braking system

In this paper, we present an estimation of the heat flux generated by friction under real aircraft braking conditions using an inverse method. The estimation is performed considering an assumption of 1D transient model and multiple interfaces. This model takes into account a non-perfect description of the thermal contact. Then, an identification of the generated heat flux by friction in the different interfaces from experimental data is performed using a linear temporal evolution parameterization of this parameter. The reconstruction of the thermal field from identified generated heat fluxes provides some very low residues. The comparison between the thermal energy identified by the inverse method and mechanical energy absorbed on the test bench validates the results.

Research on HILS Technology Applied on Aircraft Electric Braking System

On the basis of analyzing the real-time feature of hardware-in-the-loop simulation of aircraft braking system, a new simulation method based on MATLAB/RTW (Real-Time Workshop) and DSP is introduced. The purpose of this research is to develop a digital control unit with antilock brake system control algorithm for aircraft braking system using HILS. DSP is used as simulator. Using this method, a detailed mathematical modeling of system is proposed first. Studies on reducing sampling time with model simplification and modeling for applying to I/O interface of DSP and HILS are conducted. Compared with other methods, this method is low cost and convenient to implement. By using these methods, we can complete HIL simulation of aircraft braking under various experimental conditions, modify its control laws, and test its braking performance. The results have demonstrated that this platform has high reliability. The algorithm is verified by real-time closed loop test with HILS system and the results are presented.

Multi-criteria failure mode effects and criticality analysis method: a comparative case study on aircraft braking system

The Department of the USA's Army published technical manual TM 5-698-4 to create a new failure mode effects and criticality analysis (FMECA) method, since the formal military specifications and standards MIL-STD-1629A was cancelled. However, the design processes of the two-phase product do not take the most appropriate corrective measures to eliminate the product risks in the first design phase. Thus, the risk priority number (RPN) and criticality analysis (CA) methods have serious flaws from a technical perspective which are still widely used and misleading in the related FMECA handbook and instruction manual. This paper uses the maximal entropy ordered weighted geometric averaging (ME-OWGA) operator to obtain the optimal weighting vector, which calculates FMECA values in one-phase and moreover circumvents the difficulties of mathematical operators. A fighter aircraft braking system is used as a case study to illustrate the proposed method, which compares the proposed approach with the RPN and CA methods. The results indicate that the proposed method can efficiently shorten the design process and more accurately calculate than MIL-STD-1629A, TM 5-698-4, FMECA handbook and other equivalent instruction manuals.