Roll Rate Research Articles

Design and flight test of a linear parameter varying flight controller

Future aircraft generations require improved performance and efficiency to enable a reduced environmental footprint. To acquire this goal, for example new material and wing concepts are perused at the moment by the aircraft industry. These developments, which include aspects such as over-actuation and lowly damped flexible modes, give rise to more complex, multi-objective control problems. One candidate method, which delivers a solution to these problems for the whole flight envelope, is linear parameter varying (LPV) control. It naturally incorporates the controller scheduling in the synthesis process, guarantees stability and robustness over the entire parameter envelope, and enables intuitive multi-objective, multiple-input multiple-output (MIMO) controller designs. This paper proves the concept of LPV control in practice: The paper presents and discusses the LPV controller design process, simulation results, motion simulator test and finally, the in-flight validation of the control system on a Cessna Citation II aircraft. The developed inner loop controller structures are inspired by classical flight controllers used on state-of-the-art fly-by-wire airliners. The longitudinal aircraft motion is augmented with load-factor command and the lateral motion controller features a roll rate command with attitude hold behavior. The control laws are validated in flight by automated and actual pilot inputs with respect to functionality, flying and handling qualities. Test results are encouraging with the provided key findings and lessons learned aiming to provide a simplification for future LPV flight controller development and testing campaigns.

Multihorizon discrete time survival models

The new accounting standards of CECL for the US and IFRS 9 elsewhere require predictions of lifetime losses for loans. The use of roll rates, state transition and “vintage” models has been proposed and indeed are used by practitioners. The first two methods are relatively more accurate for predictions of up to one year, because they include lagged delinquency as a predictor, whereas “vintage” models are more accurate for predictions for longer periods, but not short periods because they omit delinquency as a predictor variable. In this paper we propose the use of survival models that include lagged delinquency as a covariate and show, using a large sample of 30 year mortgages, that the proposed method is more accurate than any of the other three methods for both short-term and long-term predictions of the probability of delinquency. We experiment extensively to find the appropriate lagging structure for the delinquency term. The results provide a new method to make lifetime loss predictions, as required by CECL and IFRS 9 Stage 2.

A Vehicle Rollover Evaluation System Based on Enabling State and Parameter Estimation

There is an increasing awareness of the need to reduce the traffic accidents and fatality rates due to vehicle rollover incidents. The accurate detection of impending rollover is necessary to effectively implement vehicle rollover prevention. To this end, a real-time rollover index and a rollover tendency evaluation system are needed. These should give high accuracy and be of a low application cost. In this article, we propose a rollover evaluation system taking lateral load transfer ratio (LTR) as the rollover index with inertial measurement unit as the system input. A nonlinear suspension model and a rolling plane vehicle model are established for the state and parameter estimation. An adaptive extended Kalman filter is utilized to estimate the roll angle and rate, which adjusts noise covariance matrices to accommodate the nonlinear model characteristic and the unknown noise characteristic. In the meantime, the forgetting factor recursive least squares method is utilized to identify the height of the center of gravity. The Butterworth filter is used to filter out the high-frequency noise of the acceleration signal and the index of LTR is accordingly calculated based on the estimation results. The proposed scheme is verified and compared through hardware-in-loop tests. The results show that the developed scheme performs well in a variety of operating conditions.

Steering control to balance a motorcycle at low speeds based on riders’ input

Motorcycles are a primary mode of daily transportation in many developing countries, especially in towns and cities. The increased traffic congestion constrains the average speed of the motorcycle, causing stability and safety concerns for the riders. A controller that assists the riders can improve this scenario. This paper presents a new controller developed using an experimental study that improves the low-speed stability of a motorcycle. The experiments were conducted on a motorcycle with the riders of three experience levels: beginner, intermediate and expert. The input parameters: steering angle and steering torque; the output parameters: roll angle, yaw angle, roll rate and yaw rate were measured. Critical input and output parameters were identified statistically from the experimental measurements and used for the controller modelled in Simulink. The controller model was co-simulated with a multi-body dynamics model of the motorcycle. The co-simulation results showed the controller developed herein stabilises the motorcycle model at low speeds.

Predicting On-axis Rotorcraft Dynamic Responses Using Machine Learning Techniques

Physical-law-based models are widely utilized in the aerospace industry. One such use is to provide flight dynamics models for use in flight simulators. For human-in-the-loop use, such simulators must run in real-time. Owing to the complex physics of rotorcraft flight, to meet this real-time requirement, simplifications to the underlying physics sometimes have to be applied to the model, leading to errors in the model's predictions of the real vehicle's response. This study investigated whether a machine-learning technique could be employed to provide rotorcraft dynamic response predictions. Machine learning was facilitated using a Gaussian process (GP) nonlinear autoregressive model, which predicted the on-axis pitch rate, roll rate, yaw rate, and heave responses of a Bo105 rotorcraft. A variational sparse GP model was then developed to reduce the computational cost of implementing the approach on large datasets. It was found that both of the GP models were able to provide accurate on-axis response predictions, particularly when the model input contained all four control inceptors and one lagged on-axis response term. The predictions made showed improvement compared to a corresponding physics-based model. The reduction of training data to one-third (rotational axes) or one-half (heave axis) resulted in only minor degradation of the sparse GP model predictions.

Constant roll warm inflation in high dissipative regime

Constant-roll warm inflation is introduced in this work. A novel approach to finding an exact solution for Friedman equations in the constant-roll framework is presented for cold inflation and is extended to warm inflation with the constant dissipative parameter Q=Γ/3H. The evolution of the primordial inhomogeneities of a scalar field in a thermal bath is also studied. The 1σ consistency between the theoretical predictions of the model and observational constraints has been proven for a range of Q and β=−ϕ̈/(3Hϕ) (constant rate of inflaton roll). In addition, we briefly investigate the possible enhancement of super-horizon perturbations beyond the slow-roll approximation.

Probabilistic solution of nonlinear ship rolling in random beam seas

In this paper, the probability density function (PDF) and the mean up-crossing rate of nonlinear ship rolling in random beam seas are investigated. The excitation of stationary random sea waves is approximated as a second-order linear filtered white noise. The Fokker–Planck–Kolmogorov (FPK) equation governing the probability density function of ship rolling is a four-dimensional linear partial differential equation with varying coefficients, and obtaining its exact solution is much more sophisticated. The exponential-polynomial closure (EPC) method is applied to solve the corresponding FPK equation of the system. In numerical examples, linear-plus-cubic damping model and linear-plus-quadratic damping model with three different sea states are further examined. Comparison with the equivalent linearisation (EQL) method and Monte Carlo simulated results show that the proposed procedure is effective to obtain a satisfactory probability density function solution, especially in the tail region.

Design and Test of Double-Cutterbar Structure on Wide Header for Main Crop Rice Harvesting

Harvesting main crop rice with a wide header at a required height can increase its ratoon crop yield by decreasing the stubble rolling rate. However, an increased harvest width brings in more input material in a specific time, causing the size enlargement or working speed slowdown of harvesters. To solve this issue, a double-cutterbar structure was proposed. To provide a design baseline for the structure, the cutterbar configuration methods based on rice plant deformation were developed and verified, stalk shearing tests were conducted, and a double-cutterbar prototype was fabricated and tested. The results indicated that the methods developed for the configuration of the upper and lower cutterbars could considerably implement their functions of lowering the straw-grain ratio and keeping stubble height as required. The shearing tests indicated that the bevel angle significantly influenced the total shearing energy on each cutting point in Internode 2 and 3 (p < 0.05) due to the increased stalk cross sectional area. The stubble rolling rate, panicle straw length and stubble height of the developed harvester were 26.9 %, 125 ± 80 mm and 332 ± 22 mm, respectively, which could meet the requirements of main crop rice harvesting. The outcomes indicated the functionality and practicability of the double-cutterbar structure developed based on rice plant deformation and shearing properties.

Experimental and computational study of operation of an amphibious craft in calm water

The hydrodynamic characteristics of a waterjet-propelled amphibious craft traveling in displacement and planing modes are studied via full-scale experiments and numerical simulations in three ways. First, variations of pitch, resistance, and vertical rise for speeds from 2 to 18 knots are investigated. As speed is incrementally increased, pitch and resistance increase geometrically before maximizing in the transition region. In this region, the computations underpredict pitch, yet resistance matches the steady-state thrust measurements well. Second, maneuverability in displacement mode at 4 knots is investigated with a zigzag maneuver. Time variations of heading, pitch, yaw rate, roll, and roll rate predicted by computational fluid dynamics (CFD) for the zigzag maneuver are in good agreement with the experimental results. Third, the dynamic transition from displacement to planing mode is investigated by abruptly increasing the thrust beyond the craft's peak resistance. Beyond the resistance maximum, the vehicle experiences a sharp increase in speed and drop in pitch angle. Experiment and simulation conclude similarly with an abrupt cut to propulsion, resulting in a quick deceleration, which is overcome by its own wake. Simulated kinematics of the deceleration are remarkably accurate, suggesting valid computations of the transient drag, wake generation, and vehicle response to waves.

Adverse-Yaw Control During Roll for a Class of Optimal Lift Distributions

Lifting-line theory has formed the basis of wing-design understanding for nearly a century. This theory has previously been used to develop a class of optimal lift distributions that minimize induced drag for finite wings under specific structural and aerodynamic constraints. This class of lift distributions was first introduced by Prandtl in 1933 and includes the elliptic lift distribution and the bell-shaped lift distribution, among others, as special cases. Here, it is shown that, for all lift distributions in this class except the elliptic lift distribution, an antisymmetric twist distribution can be added to the wing to control the adverse yawing moment during roll. The requisite amount of this additional twist distribution depends on the prescribed yawing-moment sign and magnitude, and it can be used to produce zero adverse yaw or even proverse yaw during roll. Of course, employing this methodology to control the roll–yaw coupling produces additional induced drag relative to the case without roll–yaw coupling control. This induced-drag penalty is studied in detail and shows that a symmetric lift distribution within this class can be selected to minimize induced drag for a desired roll–yaw coupling. Roll initiation and steady rolling rate are both considered. Results can be applied to the design of morphing aircraft to minimize the use of a vertical control surface for yaw control.

Stability, performance and power flow of active U-tube anti-roll tank

Active control of ship roll using a U-tube anti-roll tank (ART) is considered. A linearized model of the ship and active ART with two degrees of freedom is formulated. The two degrees of freedom are the ART fluid free surface angle and the ship roll angle. The active control approach is based on the absolute roll-rate feedback assuming an idealized pump located in the connecting conduit of the U-tube. The pump generates a pressure difference proportional to the roll rate via a negative feedback gain. First, the stability of the feedback loop is analysed using the Nyquist criterion. The stability analysis indicates that the ART natural frequency should be set well below the ship roll natural frequency. The performance analysis is carried out in terms of the reductions of the frequency response function between the wave slope exciting the ship roll and the roll angle. It is found that also the active control performance improves with reducing the natural frequency of the ART. Finally, the analysis of the power flow through the system indicates that the pump power can be reduced with the reduction of the ART natural frequency. Also, it is shown that it is possible to reduce the wave power input into the ship plus ART system by engaging the active control.

Aero-Driven Bleed-Air Applied to Roll Control

Aero-driven bleed-air (ADB) is a flow control technology that offers a unique alternative to novel aircraft concepts that are not conducive to traditional flapped control surfaces. The primary source of mechanical energy for ADB control is derived from the motion of the vehicle. Inherent pressure differences across aerodynamic surfaces are communicated by means of internal channels, with the intent of affecting the local crossflow. Effected across a large area, ADB can significantly alter the global aerodynamic forces and moments. This investigation explores the performance of large-area-distributed ADB as a roll control mechanism on a low-speed, fixed-wing air vehicle. A series of wind tunnel experiments is presented, aimed at characterizing the effects that various porosity configurations have on the lift and drag of a Clark-Y airfoil section. ADB was found to be capable of reducing the sectional lift coefficient across a broad domain of angles of attack () by as much as relative to the baseline airfoil. A mathematical model for estimating the steady-state roll rate of a wing with ADB is developed. Several pore opening schedules are considered, with an emphasis on finding a nearly linear relationship between bleed level and steady-state roll rate. The selected schedule is implemented on a flight test vehicle equipped with ADB roll control effectors. Roll rates of up to were achieved in flight, and flight test data were found to validate the steady-state roll rate model. The aircraft was piloted from takeoff through landing using ADB for roll control.

Dynamic behaviours of damaged stability for floating energy storage unit after accidental collision

The transient dynamic behaviour of floating energy storage unit (FESU) is a result of coupling between three non-linear effects, which are sloshing of floodwater, wave loading, and FESU dynamics. The coupling of these effects would result in the catastrophic failure of the FESU in extreme conditions. Computational Fluid Dynamics (CFD) has shown that it holds great potential in solving the problem in the time domain, which is suitable for the transient stage. In this study, CFD simulation of damaged stability was conducted by using OpenFOAM to determine the dynamic response of FESU under the effects of floodwater and wave in transient flooding. OpenFOAM CFD simulation was conducted for the flooding of barge shaped FESU with different water inlet and air outlet sizes in still water condition followed by damaged stability in Stokes’ fifth-order beam wave and head wave condition. Dynamic responses of FESU, such as roll, pitch, heave, and floodwater volume flow rates were determined using the dynamic meshing solver of OpenFOAM. Simulation results showed similarity to experimental results within the time frame of 16 seconds. Reduction in water inlet area and air outlet area decreased the flooding time and flow rate of flood water. The amplitude of vibration of roll and pitch motion increased as the flood water volume was increased due to the force of floodwater exerted on the wall. Sloshing effects also caused the model to roll and pitch in secondary vibrational motion. Due to the coupling effect of the three non-linear criteria, the inflow and outflow of floodwater changed with time, which concludes that transient effects should not be ignored in the damaged stability assessment of FESU.

The preparation of PA6/CS‐NPs nanofiber filaments with excellent antibacterial activity via a one‐step multineedle electrospinning method with liquid bath circling system

AbstractBecause of the wide applications of the antibacterial fabrics, they have had broad‐based development recently. Chitosan is an environment‐friendly, biodegradable and natural organic antibacterial agent, which can be used to prepare the antibacterial fibers. Chitosan‐composited electrospun fibers have the potential to be applied in the fields such as surgical gowns, medical gauze, underwear, and sportswear. Therefore, using a one‐step 12‐needle electrospinning method with liquid bath circulating system, PA6/CS‐NPs nanofiber filaments would be fabricated. Under the combined effect of the drafting and impact forces, the surface of the nanofibers could adhere to a certain number of chitosan nanoparticles (CS‐NPs). By varying the mass ratios of 0.2 wt.% Span‐80/Tween‐80 (S‐80/T‐80) in the bath solution, water flow rate, and the winding rate, the filaments with different properties could be prepared. The results revealed that the surface of PA6 nanofibers could adhere to the largest number of CS‐NPs and the mechanical properties were good when the mass ratio of S‐80/T‐80 was 3/7, the water flow rate was 20 ml/min, and the roller rate was 40 r/min. The nanofibers fabricated by the optimum spinning parameters showed excellent antibacterial activity. In addition, the rate of bacteriostasis againstE. coliandS. aureuswas 99.9% and 98.9%, respectively.

Application of Queuing Theory in Production Efficiency of Direct Rolling Process of Long Product

Based on the mathematical method of queuing theory, the queuing model of billets in the direct rolling process of the long product was established, which represented the conveying process of billets at the casting and rolling interface. Using the billets queuing model, the influence of different steel quantity, length, speed and other factors on the average waiting time of a single billet in the direct rolling production process was analyzed. Combined with the temperature drop of billets, the optimal average waiting time for a single billet was determined. The method improved the conveying connection efficiency of the casting-rolling interface and the direct rolling rate of billets.

Set Membership Identification of Linear Systems With Guaranteed Simulation Accuracy

The problem of model identification for linear systems is considered, using a finite set of sampled data affected by a bounded measurement noise, with unknown bound. The objective is to identify one-step-ahead models and their accuracy in terms of worst-case simulation error bounds. To do so, the Set Membership identification framework is exploited. Theoretical results are derived, allowing one to estimate the noise bound and system decay rate. Then, these quantities and the data are employed to define the Feasible Parameter Set (FPS), which contains all possible models compatible with the available information. Here, the estimated decay rate is used to refine the standard FPS formulation, by adding constraints that enforce the desired converging behavior of the models' impulse response. Moreover, guaranteed simulation error bounds for an infinite future horizon are derived, improving over recent results pertaining to finite simulation horizon only. These bounds are the basis for a result and method to guarantee asymptotic stability of the identified model. Finally, the desired one-step-ahead model is identified by means of numerical optimization, and the related simulation error bounds are evaluated. Both input-output and state-space model structures are addressed. The approach is showcased on a numerical example and on real-world experimental data of the roll rate dynamics of an autonomous glider.

Parameter Optimization for Ship Antiroll Gyros

Ship antiroll gyros are a type of equipment used to reduce ships’ roll angle, and their parameters are related to the parameters of a ship and wave, which affect gyro performance. As an alternative framework, we designed a calculation method for roll reduction rate and considered random waves to establish a gyro parameter optimization model, and we then solved it through the bacteria foraging optimization algorithm (BFOA) and pattern search optimization algorithm (PSOA) to obtain optimal parameter values. Results revealed that the two methods could effectively reduce the overall mass and floor space of the antiroll gyro and improved its antirolling effect. In addition, the convergence speed and antirolling effect of the BFOA were better than that of the PSOA.

ПРИМЕНЕНИЕ НАКОПИТЕЛЕЙ ЭЛЕКТРОЭНЕРГИИ В СИСТЕМЕ ТЯГОВОГО ЭЛЕКТРОСНАБЖЕНИЯ С ЦЕЛЬЮ ПОВЫШЕНИЯ ПРОПУСКНОЙ СПОСОБНОСТИ НА ЛИМИТИРУЮЩИХ УЧАСТКАХ

The paper considers issues of increasing capacity on «bottleneck» sections of direct current railways by means of application of electric power accumulators. Selection of electric power accumulators location is carried out with the consideration for grading of track on a section, specific recuperation, dominance of traffic type, rate of electric rolling stops, mode of feeding of intersubstational zones. When determining power consumption and capacity of electric power accumulators a depth of discharge that affects a service life and a state of charge graph that depends on a selected characteristic of charging rate are considered. The procedure of assessing the influence of electric power accumulator operation on capacity is considered on the example of one of the railway sections.

Adaptive Control Allocation: A Human-In-The-Loop Stability Analysis

This paper demonstrates the stability limits of a human-in-the-loop closed loop control system, where the plant to be controlled has redundant actuators with uncertain dynamics. Two different human operator models are considered: For tasks that require very accurate control commands, pilots are shown to produce control commands resembling the output of a pure gain controller. Therefore, we first analyze the stability of the uncertain nonlinear closed loop system with a pure gain pilot model. Another commonly employed model, to represent the inability of the human operator to respond to high frequency inputs, is the lag filter. In our second analysis, we show the stability properties of the human-in-the-loop control system where a lag filter operator model is utilized. A flight control task, where the pilot controls the pitch angle via a pitch rate stick input, and the controller receives separate roll and yaw rate references, is simulated to demonstrate the accuracy of the stability analysis.

Recent Developments in Non-Oriented Electrical Steels

This paper gives an overview of developments in the field of non-oriented electrical steels that are widely used in motor cores in recent years, focusing mainly on texture control. ND//<100> texture is recognized as the ideal texture for application to motor cores. To obtain a suitable texture, precise control is required during each manufacturing process. This involves adjusting the chemical components during the steel making, fine temperature and reduction control during hot rolling, temperature control during hot-band annealing, temperature and reduction control during cold rolling and heating rate and temperature control during final annealing. High silicon Fe-Si alloy containing 6.5 mass% Si has been recognized as a promising core material for high frequency applications. When producing high silicon steel by the continuous chemical vapor deposition (CVD) siliconizing process, materials with a gradient Si concentration in the sheet thickness direction have been found to display superior high-frequency iron loss.