Anti-skid Braking Research Articles

Aircraft Control System Validation via Hardware-in-the-Loop Simulation

T HISNote presents experiences from the validation process of an aircraft control system—the yawdamper controller (YDC)with hydraulic actuators. The hardware-in-the loop (HIL) simulation on a hydraulic stand with a revolving platform and a loading force actuator was used in the validation process of this mechatronics system in the first step [1]. This Note extends the previous work by describing the next level of the validation process in which the YDC and actuators have been embedded into the aircraft where the interaction with the mechanical control system is validated by the HIL simulation. The yaw damper controller and the simulator are very briefly described and the practical experiences demonstrating the usefulness of the hardware-in-the loop simulation during detection of errors in the system components are mentioned. The yawdamper (YD) is a device directly coupledwith the aircraft rudder. It senses the yaw rate via a fiber optic gyro (FOG) and compensates oscillations via hydraulic actuators deviating the rudder. Even though it is designed to be fail-safe (it is disconnected from the ruder when a failure is detected) and the direct mechanical coupling of the rudderwith the pedals guarantee controllability of the aircraft when the YDC does not work, a malfunction of the YDC could have a serious effect on flight safety. Therefore, the validation of the whole system controlling the ruder must be carefully undertaken. HIL simulation is a popular validation method in many branches. The HIL simulator for an electrohydraulic flight control system has been described in [2]. HIL simulation has been used for the development of the antiskid braking system of the aircraft in [3] or for the flight-formation system [4]. HIL is also often used for development of control systems of unmanned aerial vehicles [5–9], and missiles [10]. Reference [11] presents a study of the performance of a fuel-cell powered unmanned aerial vehicles using HIL simulation of the aircraft inflight. HIL simulation is irreplaceable in the automotive industry and it is also very useful in power electronic controls, motor control, and energetic-component design and teaching. The rest of the Note is organized as follows. The YD is briefly described in Sec. II. Section III presents the HIL simulator. The validation process is described in Sec. IV. The concluding remarks are mentioned in Sec. V.

Coupling Analysis of Frictional Heat under Control of Disc Brake Anti-Skid Brake System

The nonlinearity of material properties at different temperatures and the manner of braking force applying on a brake system are two key factors to affect the coupling of temperature and thermal stress. Considering these two factors, a finite element analysis model of automobile brake disc and pad is established. By using the model, the dynamic frictional heat and thermal stress of braking friction pair could be simulated and the coupling characters of temperature and thermal stress on friction surfaces could be studied, where the braking force is constant or controlled by an anti-skid brake system(ABS). The study results shown that the friction temperature of brake disk rises in periodic and fluctuant tendency. The fluctuant increase of temperature will influence the character of braking. The increase of friction temperature between a brake disc and pad can decrease under the control of ABS, so the effect of thermo-mechanical coupling could be reduced.

Research on Simulation of Aircraft Electro-Hydrostatic Actuator (EHA) Anti-Skid Braking System

With the background of the development of Aircraft Anti-skid Braking System, a new aircraft Electro-Hydrostatic Actuator (EHA) of a certain model fighter is designed to meet the need of the braking system. The paper describes the principle of work and features of the EHA, and gives the specific requirements of the system. The selection and performance of the motor, pump and hydraulic cylinder are optimized. Then, the paper describes the principle of work and features of the EHA, models and simulates it with MATLAB/Simulink., and analyzes the effects of all structural parameters on the performance. The results of EHA reach the design target of dynamic performance. Finally, the whole model of the aircraft system is built and established based on the EHA model and results. The results of the dry runway condition verify the correctness of the EHA design, so the Hydro Actuator of traditional aircraft anti-skid braking system could be replaced by EHA.

Design and Dynamics Analysis of Anti-skid Braking System for Aircraft with Four-wheel Bogie Landing Gears

In asymmetric conditions,the movement and loads of left/right wheels or front/back wheels of the aircraft with multi-wheel or four-wheel bogie landing gears are inconsistent.There are few open literatures related to anti-skid braking system for multi-wheels due to technology blockade.In China,the research on multi-channel control and non-equilibrium regulation has just started,and the design of multi-channel control system for anti-skid braking,the simulation of asymmetry taxiing under braking are not studied.In this paper,a dynamics model of ground movement for aircraft with four-wheel bogie landing gears is established for braking simulation, considering the six-degree-of-freedom aircraft body and the movement of bogies and wheels.A multi-channel anti-skid braking system is designed for the wheels of the main landing gears with four-wheel bogies.The eight wheels on left and right landing gears are divided into four groups,and each group is controlled via one channel.The cross protection and self-locked protection modules are added between different channels.A multi-channel anti-skid braking system with slip-ratio control or with slip-velocity control is established separately.Based on the aircraft dynamics model,aircraft braking to stop with anti-skid control on dry runway and on wet runway are simulated.The simulation results demonstrate that in asymmetric conditions,added with cross protection and self-locked protection modules,the slip-ratio-controlled braking system can automatically regulate brake torque to avoid deep slipping and correct aircraft course.The proposed research has reference value for improving brake control effect on wet runway.

Improvement of drivability and fuel economy with a hybrid antiskid braking system in hybrid electric vehicles

When braking on wet roads, Antilock Braking System (ABS) control can be triggered because the available brake torque is not sufficient. When the ABS system is active, for a hybrid electric vehicle, the regenerative brake is switched off to safeguard the normal ABS function. When the ABS control is terminated, it would be favorable to reactivate the regenerative brake. However, recurring cycles from ABS to motor regenerative braking could occur. This condition is felt to be unpleasant by the driver and has adverse effects on driving stability. In this paper, a novel hybrid antiskid braking system using fuzzy logic is proposed for a hybrid electric vehicle that has a regenerative braking system operatively connected to an electric traction motor and a separate hydraulic braking system. This control strategy and the method for coordination between regenerative and hydraulic braking are developed. The motor regenerative braking controller is designed. Control of regenerative and hydraulic braking force distribution is investigated. The simulation and experimental results show that vehicle braking performance and fuel economy can be improved and the proposed control strategy and method are effective and robust.

Wheel Slip Control via Second-Order Sliding-Mode Generation

During skid braking and spin acceleration, the driving force exerted by the tires is reduced considerably, and the vehicle cannot speed up or brake as desired. It may become very difficult to control the vehicle under these conditions. To solve this problem, a second-order sliding-mode traction controller is presented in this paper. The controller design is coupled with the design of a suitable sliding-mode observer to estimate the tire-road adhesion coefficient. The traction control is achieved by maintaining the wheel slip at a desired value. In particular, by controlling the wheel slip at the optimal value, the proposed traction control enables antiskid braking and antispin acceleration, thus improving safety in difficult weather conditions, as well as stability during high-performance driving. The choice of second-order sliding-mode control methodology is motivated by its robustness feature with respect to parameter uncertainties and disturbances, which are typical of the automotive context. Moreover, the proposed second-order sliding-mode controller, in contrast to conventional sliding-mode controllers, generates continuous control actions, thus being particularly suitable for application to automotive systems.

INTELLIGENT BRAKING SYSTEM USING FUZZY LOGIC AND SLIDING MODE CONTROLLER

In this paper, an antilock–antiskid braking system controller, which has been designed for stability enhancement of vehicles during braking and turning, is presented. Using available signals, a novel structure is proposed for vehicle stability improvement for critical driving conditions such as braking on slippery or µ-split road surfaces. In conventional vehicles, undesired lane changes may occur due to equal dispatch of braking torques to all wheels simultaneously. Also, intensive pressure on brake pedal can bring about wheel lockup which results in vehicle instability and undesired lane changes. Antilock braking system (ABS) along with Antiskid braking system (ASBS) can serve as a driver-assistance system in vehicle path correction facing critical driving conditions during braking and turning round on different road surfaces. For these purposes, at first, a trained Neuro-Fuzzy estimator is used for vehicle path prediction according to vehicle’s speed, applied steering angle and their changes. Then, slip of each wheel will be controlled by an antilock fuzzy controller which has been designed for each wheel. Also, a sliding mode controller has been designed so as to control the yaw angle considering the yaw error, where the yaw error is resulted from the difference of the Neuro-Fuzzy estimator’s output and actual yaw angle. Then, the difference of the left and the right wheels’ braking torques are used by the sliding mode controller in order to reduce the yaw error. Considering a model of three-degreeof-freedom for chassis and one-degree-of-freedom Dugoff’s tire model for each wheel, a series of Matlab/Simulink simulation results will be presented to validate the effectiveness of the proposed controller. Finally, a comparison will be made between the proposed method and one of the recent control systems which shows the superiority of its performance.

Dynamic Behavior of a Hydraulic Braking Valve Incorporating a Hydraulic Servo Actuator

This paper is dedicated to investigate the static and dynamic behavior of a pilot operated pressure reducing valve (PRV). The valve is the main component in an Anti-skid braking system of a vehicle. This system is fed by the hydraulic power from a constant pressure source. A mathematical model is deduced for the valve. A simulation program is developed usingthe MATLAB-SIMULINK where the mathematical model is implemented in the program. The developed program is used to study the dynamic valve response due to different input displacement values and effect of varying different design parameters on the overall performance of valve. A conclusion is made to evaluate the valve response and recommendations are suggested to improve valve performance.

Optimal Design of the Aircraft ABS Controller

The main control objective of an aircraft ABS(Anti-skid Brake System) is to continuously adjust brake pressure to maintain optimum brake torque. This optimum level should balance tire and runway friction at its peak value, which is conveniently done by controlling the wheel slip ratio around the peak of the friction coefflcient(µ)-slip ratio(s) curve during ABS maneuvers. It influences not only the taxing distance of an aircraft, but also the strength and the fatigue life of the landing gear system. Difficulties in designing an ABS controller are due to the nonlinear characteristics of braking system dynamics, the time-varying nature of the system components, and the unknown environmental parameters. Furthermore, as an optimal control problem, this is currently intractable because of the large uncertainty in the dynamics. In this paper, an ABS control algorithm is developed with a 5-D.O.F. aircraft dynamics model based on the landing dynamic equations and the ABS digital control unit(DCU) is designed to accommodate the anti-skid control algorithm. Also the design and implementation of real-time HILS system for development of the aircraft ABS DCU are presented. Developed ABS DCU is evaluated and tested with proposed HILS system on the several runway conditions.

実時間試行に基づくマルチプルコントロールシステムの提案とそのABSへの適用

実時間試行に基づくマルチプルコントロールシステムの提案とそのABSへの適用

Analyzing piecewise linear dynamical systems

This article presents a method of analyzing mixed logic/dynamic systems. The article describes the development of a computational tool for the analysis of piecewise linear (PL) dynamical systems. Unfortunately, many PL controllers are developed from ad hoc "intelligent systems" ideas which do not aim or allow the associated dynamic behavior to be predicted. An example of such a system is the anti-skid braking system in a car, where the controller is rule-based and designed using the engineer's knowledge of the system. The only current viable approach to testing such a system is by using extensive simulation and prototype testing, which must be repeated for each of the different car models on which it is installed. Anything that provides insight into the logic and dynamic interaction of such a system would be useful: hence the development of the work in this article. Similarly, systems with programmable logic controllers and gain schedulers also fall into the class of piecewise linear systems. The authors take ideas and known results from linear systems, convex set theory, and computational geometry and synthesize them to create an analysis tool for studying a class of systems that mix logic and dynamics. We choose to develop a computational analysis tool primarily because the traditional theoretical analysis of piecewise linear processes is intractable, except, that is, for certain local dynamic behavior.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Landing response of aircraft with optimal anti-skid braking

A short landing run requirement for an aircraft is important from economic, operational and strategic considerations. Too strong a braking produces skid, which is an undesirable condition, while weak breaking results in a long landing run. The shortest possible (optimal) landing run without any skidding requires a variable braking force to match the frictional force at all times. The maximum allowable braking force at any instant is a random variable as the ground-induced excitation and the frictional force between the wheel and the tyre are random in nature. In view of the time lag in the actuation of a servo system and its completion of the execution, a one-step prediction is employed to obtain the braking force required at a future instant. This brake management system has been tried on a simple aircraft model. The scheme is found to work well with the model.

Fuzzy learning control for antiskid braking systems

Although antiskid braking systems (ABS) are designed to optimize braking effectiveness while maintaining steerability, their performance often degrades under harsh road conditions (e.g. icy/snowy roads). The use of the fuzzy model reference learning control (FMRLC) technique for maintaining adequate performance even under such adverse road conditions is proposed. This controller utilizes a learning mechanism that observes the plant outputs and adjusts the rules in a direct fuzzy controller so that the overall system behaves like a reference model characterizing the desired behavior. The performance of the FMRLC-based ABS is demonstrated by simulation for various road conditions (wet asphalt, icy) and transitions between such conditions (e.g. when emergency braking occurs and the road switches from wet to icy or vice versa). >

Practical requirements for modelling the dynamics of hydraulic pipelines

Hydraulic pipeline dynamics play an important role in many real systems, for example in Diesel fuel injection, anti-skid braking, under-sea oil production and hydraulic control in general. When investigating the behaviour of such systems by simulation it is necessary to have suitable numerical models for the line. An excessively complicated model wastes computing time, but an inadequate one fails to predict the behaviour satisfactorily. A first step in deciding upon a suitable model is to look at the relationship between the frequency content of transient operations in the system and the natural frequencies of the lines. Rapid transients can be initiated by such things as valve operation, actuators reaching the end of their travel and cavitation and air release. A second important criterion is the amount of damping in the lines caused by fluid friction. This may be steady or frequency dependent friction in laminar or turbulent flow. On the one hand, increasing the complexity of the friction model employed makes the computations more involved. On the other hand, friction may limit the amount of higher frequency motion and consequently make the computations simpler. This paper examines the requirements for line models under different circumstances, and how these requirements can be met. Discussions are illustrated with results on practical systems.

A Four-Phase Control Scheme of an Anti-Skid Brake System for all Road Conditions

This paper presents a new scheme of four-phase control and its design method to accommodate all road conditions for an anti-skid brake system. This control law differs from the conventional two-phase control by adding a high-pressure holding mode and a low-pressure holding mode. The elapsed time interval and the angular acceleration of the wheel are used to control the switching of these two additional modes. Firstly, a piecewise linear tyre model with two segments is used to approximate all tyre-road characteristics. Next, the threshold values for the two additional modes are determined to ensure the desired performance under all road conditions for anti-skid systems with a quick convergence rate towards the desired operating region, so that a large brake force and desirable directional stability for the vehicle can be obtained. Finally, computer simulations are performed for two selected cases with dry and wet roads, with the results showing that the desired operation is achieved in only a few cycles.

Discrete-time controller design for robust vehicle traction

A discrete-time control algorithm for robust vehicle traction, which includes antiskid braking and antispin acceleration, is presented. The algorithm is a nonlinear feedback scheme that can be designed via classical digital control theory. The algorithm is easy to tune and modify to incorporate higher-order dynamics, which may be necessary for a practical hardware setup. The robust controller provides stable and reliable performance under a variety of uncertainties involved in the vehicle/brake system that are difficult to measure. The effectiveness of this new scheme is demonstrated by experiments on antiskid braking. >

The dynamic response of an aircraft wheel to variations in runway friction

Experimental and analytical techniques are presented for the determination of the response characteristics of a scale-model aircraft wheel to changes in runway friction. Results obtained from tests using these techniques are given. The wheel spin-up acceleration is shown to be proportional to wheel load and to the magnitude of the surface friction coefficient after surface change. It is also found to be inversely proportional to brake torque, but is largely independent of speed. An increase of speed is shown to increase the distance required for spin-up of a locked wheel as it encounters surfaces of higher friction coefficient. Good correlation of these trends is obtained analytically.The effects of tyre flexibility are indicated by the results of both the experimental tests and the analytical simulations. These effects may degrade the performance of aircraft antiskid braking systems. It is recommended, therefore, that simulations used in the development of such systems take proper account of tyre flexibility when modelling the dynamics of the wheel and tyre.

4657120 Flywheel mechanisms for anti-skid braking systems

Proposing optimum designs by adding disk counterweights to reduce the shaking force and shaking moment of the drag-link drive of mechanical presses is the main subject of this study. The two-phase optimization technique is proposed for the multi-objective optimization. The effects of implementing the designs on the flywheel and brake of the machine are also evaluated. Regarding the two-phase optimization technique proposed, it starts with an initial estimate but generates a few feasible designs. It is found that the results obtained with the technique are usually better than those starting with the criterion value as the objective function. The optimum designs with or without the tangent constraints, which insure the contours of the added counterweights on the links with fixed pivots that are tangent to the pivot centers, are investigated. It is found that the results with the tangent constraints are more cost-effective. Subject to the very strict space constraints, the shaking effects can be reduced by almost a half, using the proposed design.

4365538 Vacuum operatable differential servo-motor: Masamoto Andoh assigned to Aisin Seiki Kabushiki Kaisha

The main control objective of an aircraft ABS(Anti-skid Brake System) is to continuously adjust brake pressure to maintain optimum brake torque. This optimum level should balance tire and runway friction at its peak value, which is conveniently done by controlling the wheel slip ratio around the peak of the friction coefflcient(µ)-slip ratio(s) curve during ABS maneuvers. It influences not only the taxing distance of an aircraft, but also the strength and the fatigue life of the landing gear system. Difficulties in designing an ABS controller are due to the nonlinear characteristics of braking system dynamics, the time-varying nature of the system components, and the unknown environmental parameters. Furthermore, as an optimal control problem, this is currently intractable because of the large uncertainty in the dynamics. In this paper, an ABS control algorithm is developed with a 5-D.O.F. aircraft dynamics model based on the landing dynamic equations and the ABS digital control unit(DCU) is designed to accommodate the anti-skid control algorithm. Also the design and implementation of real-time HILS system for development of the aircraft ABS DCU are presented. Developed ABS DCU is evaluated and tested with proposed HILS system on the several runway conditions.

A describing-function approach to antiskid design

A describing-function approach is employed in the design of an antiskid braking system. This includes the specification of the dynamics of a braking vehicle, a proposed system employing a feedback compensator to provide antiskid behavior, and the determination of the design parameters by a describing-function analysis. A wide range of tire-roadway conditions was considered in the latter. The resulting design was implemented and evaluated in field tests. The observed antiskid braking performance was approximately that predicted from the design. Thus the describing-function approach, especially in view of its ease of application and the insights it provides, appears to be a useful one for the control aspect of antiskid design.