Roll Rate Research Articles

Field Tests of a Tractor Rollover Detection and Emergency Notification System.

The objective of this research was to assess the feasibility of a rollover detection and emergency notification system for farm tractors using field tests. The emergency notification system was developed based on a tractor stability model and implemented on a mobile electronic device with the iOS operating system. A complementary filter was implemented to combine the data from the accelerometer and gyroscope sensors to improve their accuracies in calculating the roll and pitch angles and the roll and pitch rates. The system estimates a stability index value during tractor operation, displays feedback messages when the stability index is lower than a preset threshold value, and transmits emergency notification messages when an overturn happens. Ten tractor rollover tests were conducted on a field track. The developed system successfully monitored the stability of the tractor during all of the tests. The iOS application was able to detect rollover accidents and transmit emergency notifications in the form of a phone call and email when an accident was detected. The system can be a useful tool for training and education in safe tractor operation. The system also has potential for stability monitoring and emergency notification of other on-road and off-road motorized vehicles.

Sensor Failure Detection, Identification, and Accommodation Using Fully Connected Cascade Neural Network

Modern control systems rely heavily on their sensors for reliable operation. Failure of a sensor could destabilize the system, which could have serious consequences to the system's operations. Therefore, there is a need to detect and accommodate such failures, particularly if the system in question is of a safety critical application. In this paper, a sensor failure detection, identification, and accommodation (SFDIA) scheme is presented. This scheme is based on the fully connected cascade (FCC) neural network (NN) architecture. The NN is trained using the neuron by neuron learning algorithm. This NN architecture is chosen because of its efficiency in terms of the number of neurons and the number of inputs required to solve a problem. The SFDIA scheme considers failures in pitch, roll, and yaw rate gyro sensors of an aircraft. A total of 105 experiments were conducted; out of which, only one went undetected. The SFDIA scheme presented here is efficient, compact, and computationally less expensive, in comparison to schemes using, for example, the popular multilayer perceptron NN. These benefits are inherited from the FCC NN architecture.

Dynamic stability conditions for a rolling flight vehicle applying continuous actuator

The conditions for dynamic stability of coning motion for a rolling missile are proposed. Considering dynamics of fin actuator, a Proportional–Derivative (PD) controller is applied to the servomechanism employing a permanent magnet DC motor. The necessary and sufficient conditions of dynamic stability are analytically derived. Both steady state and transient responses of actuator are considered in this paper. The differential equation of a whole system for steady state response of actuator leads to a second order differential equation with complex coefficients. A theorem based on Routh–Hurwitz stability criterion is proposed that gives a triple inequality to determine the stability region of PD controller and consequentially, the stability of coning motion. For transient response, the feasibility of a linear matrix inequality should be checked for each PD coefficient. It is shown that considering the transient response of actuator can change the stability region. The controller coefficients that stabilize the coning motion in steady state response may cause instability in transient response of actuator. Finally, validation of this investigation is examined through simulation. Because of continually rolling motion of missile, the cross coupling that is caused by phase lag angle, will occur, so the effect of PD controller coefficients on static phase lag angle is discussed and some technical notes to reduce the cross coupling effect are explained. Furthermore, the influence of roll rate frequency on the region of PD controller coefficients is presented and a safe region for design is recommended.

Human manual control performance in hyper-gravity.

Hyper-gravity provides a unique environment to study how misperceptions impact control of orientation relative to gravity. Previous studies have found that static and dynamic roll tilts are perceptually overestimated in hyper-gravity. The current investigation quantifies how this influences control of orientation. We utilized a long-radius centrifuge to study manual control performance in hyper-gravity. In the dark, subjects were tasked with nulling out a pseudo-random roll disturbance on the cab of the centrifuge using a rotational hand controller to command their roll rate in order to remain perceptually upright. The task was performed in 1, 1.5, and 2 G's of net gravito-inertial acceleration. Initial performance, in terms of root-mean-square deviation from upright, degraded in hyper-gravity relative to 1 G performance levels. In 1.5 G, initial performance degraded by 26 % and in 2 G, by 45 %. With practice, however, performance in hyper-gravity improved to near the 1 G performance level over several minutes. Finally, pre-exposure to one hyper-gravity level reduced initial performance decrements in a different, novel, hyper-gravity level. Perceptual overestimation of roll tilts in hyper-gravity leads to manual control performance errors, which are reduced both with practice and with pre-exposure to alternate hyper-gravity stimuli.

Detection of impending vehicle rollover with road bank angle consideration using a robust fuzzy observer

This article describes a method of vehicle dynamics estimation for impending rollover detection. We estimate vehicle dynamic states in presence of the road bank angle as a disturbance in the vehicle model using a robust observer. The estimated roll angle and roll rate are used to compute the rollover index which is based on the prediction of the lateral load transfer. In order to anticipate rollover detection, a new method is proposed to compute the time to rollover (TTR) using the load transfer ratio (LTR). The nonlinear model, deduced from the vehicle lateral and roll dynamics, is represented by a Takagi-Sugeno (T-S) fuzzy model. This representation is used to account for the nonlinearities of lateral cornering forces. The proposed T-S observer is designed with unmeasurable premise variables to cater for non-availability of the slip angles measurement. The proposed approach is evaluated using CarSim simulator under different driving scenarios. Simulation results show good efficiency of the proposed T-S observer and the rollover detection method.

단일 GPS와 롤각속도계를 이용한 롤 회전 비행체의 롤자세각 추정

In this paper, a roll angle estimation method of a rolling airframe using a low grade GPS and a roll rate gyro is proposed. The strength of the received signal of the GPS antenna attached on the rolling airframe is maximized when the GPS satellite is placed on the plane determined by the x-axis of the rolling airframe and the GPS antenna axis. Under the assumption that the x-axis of the rolling airframe is coincident with its velocity vector, the roll angle of the rolling airframe is calculated from the relative position vector of the satellite to the GPS when the GPS signal strength becomes maximum. The Kalman filter combined with a roll rate gyro is introduced to increase the determination accuracy of the roll angle. The performance of the proposed method is verified via 6-DOF simulations.

Autonomous Flight of Unmanned Aerial Vehicle (UAV) by using Linear Quadratic Regulator (LQR)

The linear quadratic regulator based autopilot is premeditated for level flight of unmanned aerial vehicle (UAV) which has been achieved lucratively. Diverse modes are utilized for controlling the rates of UAV. The pitch rate is controlled by utilizing the phugoid mode, the roll rate is controlled by utilizing the roll mode and the spiral mode is utilized for yaw rate. The linear quadratic regulator proposes sturdiness at the rate of accomplishment to subjugation over the turbulences and instabilities in order to conquer the favored performance. The FlightGear simulator is utilized for the authentication of the performance of the autopilot. The level flight has been conquered successfully and has been legitimated by utilizing the FlightGear simulator. The simulated results as well as the FlightGear simulator results or the legitimated results are presented in this paper. Microsoft Visual Studio has been employed as a conduit between the MATLAB and FlightGear Simulator.

Firing Control Optimization of Impulse Thrusters for Trajectory Correction Projectiles

This paper presents an optimum control scheme of firing time and firing phase angle by taking impact point deviation as optimum objective function which takes account of the difference of longitudinal and horizontal correction efficiency, firing delay, roll rate, flight stability, and so forth. Simulations indicate that this control scheme can assure lateral impulse thrusters are activated at time and phase angle when the correction efficiency is higher. Further simulations show that the impact point dispersion is mainly influenced by the total impulse deployed, and the impulse, number, and firing interval need to be optimized to reduce the impact point dispersion of rockets. Live firing experiments with two trajectory correction rockets indicate that the firing control scheme works effectively.

2B23 Condition diagnosis of railway tracks by a compact size onboard device(Condition Monitoring-Infrastructure)

This paper summarizes observations on a new development of a compact size onboard device for condition monitoring of railway tracks. Track irregularities are estimated from a vertical and a lateral accelerations and roll rate of a car body. Rail corrugation is detected by cabin noise according to spectral peak calculation. A GPS system and a map-matching algorithm are used to pinpoint the location of faults on tracks. The device is driven by a Li-ion battery for 6 hours or by outside power source. Accelerometers, rate gyroscope and GPS were designed to give higher performance. A microphone may be added outside if condition monitoring of rail corrugation is necessary. Collected data are usually kept in inside un-volatility memory (SSD) or an SD card. Data transfer module transfers the collected data to a data server via cellular phone. The compact size onboard device provides regular monitoring of tracks in order to sustain railway systems and secure the safety.

Singular Perturbation Control of the Lateral-Directional Flight Dynamics of an UAV

This paper presents a singular perturbation control strategy for regulating the lateral-directional flight dynamics of an Unmanned Air Vehicle (UAV). The proposed control strategy is based on a four-time-scale (4TS) decomposition that includes the side-slip velocity, bank angle, yaw rate and roll rate dynamics, with the control signals being the aileron and rudder deflection. The nonlinear control strategy drives the system to follow a reference in load factor which in return provides references in bank angle, side-slip velocity and yaw rate. In addition, the control strategy permits to select the desired dynamics for all the singularly perturbed subsystems. Numerical results are included for a realistic nonlinear UAV model, including saturation on the control signals, and unmodeled dynamics.

Variable stability system control law development for in-flight simulation of pitch/roll/yaw rate and normal load

This paper describes the development of variable stability system (VSS) control laws for the KFA-i to simulate the dynamics of KFA-m aircraft. The KFA-i is a single engine, Class IV aircraft and was selected as an in-flight simulator (IFS) aircraft, whereas the KFA-m is a simulated aircraft that is based on the F-16 aircraft. A 6-DoF math model of KFA-i aircraft was developed, linearized, and separated into longitudinal and lateral motion for VSS control law synthesis. The KFA-i aircraft has five primary control surfaces: two flaperons, two all movable horizontal tails, and one rudder. Flaperons are used for load control, the horizontal tails are used for pitch and roll rate control, and the rudder is used for yaw rate control. The developed VSS control law can simulate four parameters of the KFA-m aircraft simultaneously, such as pitch, roll, yaw rates, and load. The simulation results show that KFA-i follows the responses of KFA-m with high accuracy.

Factors Affecting Physical Properties of Prednisolone Loaded Nanoparticles Fabricated by Eletrohydrodynamic Atomization Technique

Recently, nanoparticulate system has been applied to deliver drug to colon because this system can increase drug absorption, prolong drug staying in gastrointestinal tract and also minimize chance of dose dumping effect. In this study, nanoparticles (NPs) developed for colonic drug delivery were fabricated via electrohydrodynamic atomization (EHDA) to find suitable formulation and preparation conditions. The NPs were prepared by dissolving prednisolone (model drug) and Eudragit® S100 (EDS100) in methanol, ethanol, isopropanol, butanol and mixtures of ethanol with purified water in various drug/polymer weight ratio and polymer concentrations. After that, the prepared solution was injected using the EHDA machine. The preparation condition and the instrument parameters such as applied voltage, injected distance, feed rate, and drum collector rolling rate were delicately adjusted again to obtain blank and drug loaded NPs. The NPs papered from methanol offered spherical particles with diameter size of 422 nm. The products of isopropanol and butanol were shrinkage particles. The sprayed products were changed from particle to fiber when using the spraying solution prepared from high concentration of EDS100. More fiber product was obtained when high applied voltage (20kV) was utilized. Prednisolone loaded NPs were also fabricated by EHDA. SEM and zeta-potential results reveal that prednisolone was entrapped in the NPs. All the drug loaded NPs products were in spherical shape with average diameter size of 448.60-660.98 nm and the maximum drug encapsulation was 92.65%. From the preliminary result, this nanoparticulate system expresses possibility to fabricate specific colonic drug delivery.

Robust fault tolerant tracking controller design for vehicle dynamics: A descriptor approach

In this paper, an active Fault Tolerant Tracking Controller (FTTC) scheme dedicated to vehicle dynamics system is proposed. To address the challenging problem, an uncertain dynamic model of the vehicle is firstly developed, by considering the lateral forces nonlinearities as a Takagi–Sugeno (TS) representation, the sideslip angle as unmeasurable premise variables and the road bank angle as an unknown input. Subsequently, the vehicle dynamic states with the sensor faults are jointly estimated by a descriptor observer on the basis of the roll rate and the steering angle measures. Then a fault tolerant tracking controller is synthesized and solutions are proposed in terms of Linear Matrix Inequalities (LMIs). Simulation results show that the proposed FT control approach can effectively improve tracking performance of the vehicle motion.

LQG Control Design for Vehicle Active Anti-Roll Bar System

The objective of this paper is to design a linear quadratic regulator (LQR) and linear quadratic Gaussian (LQG) controllers for an active anti-roll bar system. The use of an active anti-roll bar will be analysed from two different perspectives in vehicle ride comfort and handling performances. This paper proposed the basic vehicle dynamic modelling with four degree of freedom (DOF) on half car model and are described that show, why and how it is possible to control the handling and ride comfort of the car, with the external forces also control strategies on the front anti-roll bar. By simulation analysis, the design model is validity and the performance under control of linear quadratic regulator (LQR) and linear quadratic Gaussian (LQG) controller are achieved. Both two controllers are modeled in MATLAB/SIMULINK environment. It has to be determined which control strategy delivers better performance with respect to roll angle and the roll rate of half vehicle body. The result shows, however, that LQG produced better response compared to a LQR strategy.

Optimal Topology of Aircraft Rib and Spar Structures Under Aeroelastic Loads

Several topology optimization problems are conducted within the ribs and spars of a wing box. It is desired to locate the best position of lightening holes, truss/cross-bracing, etc. A variety of aeroelastic metrics are isolated for each of these problems: elastic wing compliance under trim loads and taxi loads, stress distribution, and crushing loads. Aileron effectiveness under a constant roll rate is considered as are dynamic metrics: natural vibration frequency and flutter. This approach helps uncover the relationship between topology and aeroelasticity in subsonic transport wings and can therefore aid in understanding the complex aircraft design process that must eventually consider all these metrics and load cases simultaneously.

Inherent Stability Modes of Low-Aspect-Ratio Wings

The development of micro aerial vehicles has been hindered by a poor understanding of the flight dynamics associated with the unique aerodynamic regime. This study experimentally estimates the aerodynamic damping derivatives of flat-plate wings with aspect ratios less than 3 at a Reynolds number of ; when combined with previously published results detailing the lateral and longitudinal static loads, a dynamic model is developed for low-aspect-ratio wings. The initial-condition response of the linear equations of motion shows that the loading created by roll stall results in purely aerodynamic lateral modes which, unlike conventional aircraft, are not attributed to geometric features, such as the vertical tail; this response was favorably compared with the integration of the full nonlinear equations. The mode is manifested by divergent, high-amplitude perturbations in sideslip, bank angle, and roll rate; furthermore, it is seen to be affected by angle of attack variations, which significantly alter the instantaneous value of the roll stability derivative . If the input frequency of the angle of attack oscillations is close to the natural frequency of the pure lateral mode, the bank angle is seen to drift away from its equilibrium value due to an attenuated restoring roll moment. This represents a previously unconsidered stability mode, referred to as roll-resonance, which couples the lateral and longitudinal stability axes for small perturbations from equilibrium flight conditions.

On the compensation and damping of roll induced by wake vortices

AbstractThe effect of the wake of a leading aircraft on a following aircraft is demonstrated by calculating the rolling motion consisting of three terms: (i) the free rolling motion due to initial bank angle and roll rate; (ii) the forced wake response due the rolling moment induced by the wake encounter; (iii) the forced control response due to aileron deflection to counter the wake vortex effects. It is shown that in the absence of control action, the roll rate of the following aircraft goes through a peak, and then decays, leading to a constant asymptotic bank angle; the latter is a measure of the magnitude of the wake effect, e.g. is larger for weaker damping. The exact analytical solution of the roll equation appears as a power series of a damping factor, whose coefficients are exponential integrals of time; it is shown that the first two terms give an accuracy better than 2%. The theory is used to simulate 15 combinations of wake vortex encounters between leading and following aircraft in the five ICAO/FAA weight categories: light, medium, heavy, special (B757) and very large (A380).

Investigations on processing powder metallurgical high-Nb TiAl alloy sheets

In this work, high Nb-containing TiAl alloy sheets were hot rolled starting from powder metallurgical billets. The prealloyed powder prepared by the plasma rotation electrode process (PREP) was characterized. Results show that there are two typical morphologies of powders: martensitic (M) and dendritic (D) powders, which are formed due to different local cooling conditions. The two PREPed powders lead to the formation of different microstructures in HIPing. The coarse D powder will introduce defects, such as residual primary particle boundaries and interfacial porosity in the as-HIPed microstructures. The deformation behavior of PM high-Nb TiAl alloys largely depends on γ phase. Besides the dynamic recrystallization and the superplastic deformation, due to the large amount of the γ phase in PM high-Nb TiAl alloy and the high rolling rate, the mechanical twinning in γ phase plays a critical role in the hot rolling process. The mechanical properties of high-Nb TiAl alloys can be significantly improved by the hot rolling, through the refinement of microstructures and the elimination of primary particle boundaries. However, a large deformation may introduce defects and coarsened microstructures, and thus 60% deformation may be suitable for the purpose of improving mechanical properties.

Extracting Blade–Vortex Interactions Using Continuous Wavelet Transforms

An extraction method is proposed to investigate blade vortex interaction noise emitted during helicopter transient maneuvering flight. The extraction method allows for the investigation of blade vortex interactions, independent of other sound sources. It is based on filtering the spectral representation of experimentally acquired full-scale helicopter acoustic data. The data is first transformed into time-frequency space through the wavelet transformation, with blade vortex interactions identified and filtered by their high amplitude, high frequency impulsive content. The filtered wavelet coefficients are then inverse transformed to create a pressure signature solely related to blade vortex interactions. Analysis on a synthetic data set is conducted, and it is shown that blade vortex interactions can be accurately extracted so long as the blade vortex interaction peak energy signal is greater or equal to the energy in the main rotor harmonic. A brief analysis shows that the extraction method performs admirably throughout a fast advancing side roll maneuver. Using this method, it was shown that peak blade vortex interaction noise levels are linked directly to the roll rate of the vehicle, and are directed towards the retreating side during the transient portion of the maneuver.

Moral Hazard in Housing Policy: Takeaways from Judicial State Delinquencies

The longer foreclosure process in judicial states gives borrowers an incremental “free rent benefit,” potentially contributing to higher delinquencies compared to non-judicial counterparts. Based on rational expectations, we estimate that borrowers in judicial states perceive about 10–16 extra months in the foreclosure process, compared with non-judicial states. We estimate judicial effects (percentage increase in current-to-delinquent roll rates in judicial states, adjusted for other credit risk factors) to be about 20%. They are generally higher for higher CLTV loans, and also for higher FICO, and other stronger borrowers. For agency high CLTV pools, the concentration of loans from judicial states can be an important driver of delinquency buyout speeds. The judicial effect allows us to quantify the impact of moral hazard. Policy makers designing mortgage modification policies should take this into account, in our view. <b>TOPICS:</b>MBS and residential mortgage loans, legal/regulatory/public policy