Independent Steering Research Articles

Study protocol: azithromycin therapy for chronic lung disease of prematurity (AZTEC) - a randomised, placebo-controlled trial of azithromycin for the prevention of chronic lung disease of prematurity in preterm infants

IntroductionChronic lung disease of prematurity (CLD), also known as bronchopulmonary dysplasia (BPD), is a cause of significant respiratory morbidity in childhood and beyond. Coupled with lung immaturity, infections (especially by...

Robust adaptive beamforming for coprime array with steering vector estimation and covariance matrix reconstruction

Coprime array exhibits many advantages over the uniform linear array (ULA) with the same number of physical sensors in resolution performance and interference suppression capability. In this study, the authors take the advantages of coprime array to improve the robustness of adaptive beamformer. In the coprime virtual ULA (CV-ULA), they prove that a constructed Toeplitz matrix can be taken as the sample covariance matrix from the perspective of virtual signal characteristics. The CV-ULA Capon spectrum estimator is modified to obtain the directions and powers of all impinging signals. Since the real directions of all impinging signals are located at different angular sectors, they form independent signal subspace for each impinging signal. They also assign independent steering vector mismatches for different impinging signals to obtain their real steering vectors. The steering vector mismatch of each impinging signal is independently obtained by solving its own convex optimisation problem. They reconstruct the interference-plus-noise covariance matrix (INCM) with precise steering vectors and powers of interference signals. The proposed weight vector is computed by combining the desired signal steering vector and the reconstructed INCM. Extensive simulations show that the proposed algorithm provides robustness against many types of model mismatches.

Electromagnetic and mechanical analyses of the ITER electron cyclotron Upper launcher steering M4 mirrors for the vertical displacement event

Abstract The mm-wave power exiting the eight In-Vessel waveguides inside the ITER Electron Cyclotron Upper Launcher is reflected by three fixed mirror sets and finally aimed by two independent steering mirrors to specific plasma locations. A design solution for both Upper and Lower Steering M4 Mirrors capable to withstand the loads taking place during normal operation was already proposed. This design is now assessed against the Vertical Displacement Event Category III (VDEIII) linear decay (36 ms) scenario, which was identified as one of the most stringent load combinations for the steering M4 mirrors. This paper reports the analyses performed to quantify the mechanical loads induced in the steering M4 mirrors during the VDEIII scenario as well as the structural integrity assessment to validate the design against these loads. The transient electromagnetic simulations show that the highest forces are induced in the reflecting surfaces, which produce a bending moment that tends to rotate upwards the mirrors. The comparison between the categorized stresses obtained from the transient mechanical analyses and the allowable design limits according to the ASME code shows that the design of the steering M4 mirrors is widely capable of withstanding the expected loads taking place during the VDEIII scenario.

4 휠 독립 조향 차량의 핸들링 성능 향상을 위한 자가 동조 기반 적응형 모델 예측 제어 알고리즘 개발

4 휠 독립 조향 차량의 핸들링 성능 향상을 위한 자가 동조 기반 적응형 모델 예측 제어 알고리즘 개발

Yaw rate tracking-based path-following control for four-wheel independent driving and four-wheel independent steering autonomous vehicles considering the coordination with dynamics stability

The path-following problem for four-wheel independent driving and four-wheel independent steering electric autonomous vehicles is investigated in this paper. Owing to the over-actuated characters of four-wheel independent driving and four-wheel independent steering autonomous vehicles, a novel yaw rate tracking-based path-following controller is proposed. First, according to the kinematic relationships between vehicle and the reference path, the yaw rate generator is designed by linear matrix inequality theory, with the ability to minimize the disturbances caused by vehicle side slip and varying curvature of path. Considering that the path-following objective and dynamics stability are in conflict with each other in some extreme path-following conditions, a coordinating mechanism based on yaw rate prediction is proposed to satisfy the two conflicting objectives. Then, according to the desired yaw rate and longitudinal velocity, a hierarchical structure is introduced for motion control. The upper-level controller calculates the generalized tracking forces while the allocation layer optimally distributes the generalized forces to tires considering tire vertical load and adhesive utilization. Finally, simulation results indicate that the proposed method can achieve excellent path-following performances in different driving conditions, while both path-following objective and dynamics stability can be satisfied.

Path Tracking Control of Self-Reconfigurable Robot hTetro With Four Differential Drive Units

The research interest in mobile robots with independent steering wheels has been increasing over recent years due to their high mobility and better payload capacity over the systems using omnidirectional wheels. However, with more controllable degrees of freedom, almost all of the platforms include redundancy which is modeled using the instantaneous center of rotation (ICR). This paper deals with a Tetris inspired floor cleaning robot hTetro which consists of four interconnected differential-drive units, i.e., each module has a differential drive unit, which can steer individually. Differing from most other steerable wheeled mobile robots, the wheel arrangement of this robot changes because of its self-reconfigurability. In this paper, we proposed a robust path tracking controller that can handle discontinuous trajectories and sudden orientation changes. Singularity problems are resolved on both the mechanical aspect and control aspect. The controller is tested experimentally with the self-reconfigurable robotic platform hero, and results are discussed.

Distributed active disturbance rejection control for Ackermann steering of a four-in-wheel motor drive vehicle with deception attacks on controller area networks

This paper investigates the network-based modeling and distributed active disturbance rejection control (ADRC) to address the Ackermann steering problem of a four-in-wheel motor drive electric vehicle with deception attacks on controller area networks (CAN). The distributed ADRC can achieve the independent steering, ensure a small steering radius and improve the stability and robustness of the vehicle under unknown tyre longitudinal forces and network attacks. Using an independent driving strategy and Ackermann steering geometry, a state-space model for rotational velocity tracking of each wheel is established, where a virtual external disturbance that consists of the tyre longitudinal force and the expected rotational velocity is imposed on the model. Considering the effect of deception attacks on measurement outputs, sampled-data-driven extended state observers are designed to estimate the tracking error and the external disturbance. To capture the interactions among four wheels, a distributed controller based on ADRC is proposed and the resulting system is formulated as a stochastic linear system with input delay and composite disturbance, where the composite disturbance is composed of false signals, a discretized disturbance error and the derivative of the longitudinal forces. A lemma is obtained to prove the discretized disturbance error to be energy-limited. Some stochastic stability conditions with H∞ performance are derived by constructing a new discontinuous augmented Lyapunov–Krasovskii functional, and a design algorithm of the observer gain and the controller gain is presented. The effectiveness of the results is exemplified by two examples.

Lateral Tyre Force Distribution for Four-Wheel Steer-by-Wire Vehicles

In a four-wheel independent steering vehicle, all the tyres have the capability of being steered independently. The traditional steering assemblies are mechanically limited because their inner and outer wheel’s steering angles are interrelated which makes it difficult to extract the maximum possible traction from the ground. Such steering systems are unable to take the advantage of the load transfer which occurs during the cornering. This work proposes a novel method of lateral tyre force distribution between the inner and outer wheels by making use of load transfer during the cornering of the vehicle. The distribution is obtained by using a function which maps the lateral acceleration of the vehicle to the distribution of the forces between the wheels. The function can be tailored according to the requirements of the driving. The control strategy involves simple equations to allow for an easy hardware implementation. The simulations performed through numerical solution of vehicle dynamics model using the computer program in MATLAB/Simulink show an improvement in the cornering performance of the vehicle and a significant reduction in workload of tyres.

Hierarchical Synchronization Control Strategy of Active Rear Axle Independent Steering System

The synchronization error of the left and right steering-wheel-angles and the disturbances rejection of the synchronization controller are of great significance for the active rear axle independent steering (ARIS) system under complex driving conditions and uncertain disturbances. In order to reduce synchronization error, a novel hierarchical synchronization control strategy based on virtual synchronization control and linear active disturbance rejection control (LADRC) is proposed. The upper controller adopts the virtual synchronization controller based on the dynamic model of the virtual rear axle steering mechanism to reduce the synchronization error between the rear wheel steering angles of the ARIS system; the lower controller is designed based on an LADRC algorithm to realize an accurate tracking control of the steering angle for each wheels. Experiments based on a prototype vehicle are conducted to prove that the proposed hierarchical synchronization control strategy for the ARIS system can improve the control accuracy significantly and has the properties of better disturbances rejection and stronger robustness.

Comparison among Active Front, Front Independent, 4-Wheel and 4-Wheel Independent Steering Systems for Vehicle Stability Control

For the last four decades, several steering systems for vehicles such as active front steering (AFS), front wheel independent steering (FWIS), 4-wheel steering (4WS) and 4-wheel independent steering (4WIS) have been proposed and developed. However, there have been few approaches for comparison among these steering systems with respect to yaw rate tracking or path tracking performance. This paper presents comparison among AFS, FWIS, 4WS and 4WIS in terms of vehicle stability control. In view of vehicle stability control, these systems are used as an actuator for generation of yaw moment. Direct yaw moment control is adopted to calculate a control yaw moment. Distribution from the control yaw moment into tire forces is achieved by a control allocation method. From the calculated tire forces, the steering angles of FWIS, 4WS and 4WIS are determined with a lateral tire force model. To check the performance of these actuators, simulation is conducted on vehicle simulation packages, CarSim. From the simulation, the advantages of FWIS and 4WIS are revealed over AFS and 4WS.

Steered by Numbers: How Quantification Differentiates the Reform of a German University

Quantification theories assume that numbers govern and steer a policy field or an organisation. In order to steer successfully, however, the local interpretation of numbers takes centre stage as the meaning of numbers—and thus the way how actors respond to them—varies between systems or sectors. Empirically, this article reviews how a German university makes sense of political numbers and their implicit steering signals, and how quantification alters its organisational structures and reshapes the roles of academics. The article analyses the translation process distinguishing between three levels: the political discourse on university reform; the organisational adaptations; and the effects they have on the professional academic role. The article finds that the university has highly differentiated strategies to respond to the ‘governance by numbers,’ and that it has established independent number-based steering systems. We also find that such differentiation of programmes makes the university management more flexible, helping it deal with anticipated goal conflicts and unwanted allocative effects, but it also places serious strain on—and potentially overburns—the coordination provided by the university’s central administration. We also find that academics have started to align their behavioural strategies towards fulfilling their organisational goals and that they tend to deviate from professional expectations. Discussing these differentiated strategies, this article shows how the differentiation of governance approaches also contributes to the university becoming an ‘organisational actor.’ These preliminary findings suggest the need for and potential direction of further investigations.

A multibeam subarrayed time-modulated linear array

In conventional time-modulated arrays TMAs , because of the usage of the RF-switch, harmonics are generated at multiples of the modulation frequency. In this study, the synthesis of time-modulated arrays has been analyzed for cognitive radio CR systems, in which these harmonics are suitably exploited for more efficient utilization of the spectrum. In order to accomplish the desired pattern at requested harmonic frequencies, a new excitation strategy with sinusoidal signals is proposed. The use of sinusoidal waveforms creates independent beams, allowing independent steering capability. Moreover, by utilizing the subarray structure, it is possible to have a smaller number of excitation functions in the hardware. It is shown by means of explanatory examples that the effectiveness of the proposed approach is due to free-adjustable beamforming, beam steering, and low complexity.

Directing Therapy with Circulating Tumor DNA Analysis in Advanced Breast Cancer: The PlasmaMATCH Trial

Directing Therapy with Circulating Tumor DNA Analysis in Advanced Breast Cancer: The PlasmaMATCH Trial

Design and Numerical Analyses of the M4 Steering Mirrors for the ITER Electron Cyclotron Heating Upper Launcher

Four electron cyclotron heating upper launchers (ECHULs) will be used at ITER to counteract magnetohydrodynamic plasma instabilities by targeting them with up to 24 MW of mm-wave power at 170 GHz. This mm-wave power is injected through eight ex-vessel (EV) waveguide assemblies for each ECHUL to the in-vessel (IV) waveguides. The mm-wave power exiting the eight IV waveguides inside the ECHUL is reflected by three fixed mirror sets and finally aimed by two independent steering mirrors to specific plasma locations. These two steering mirrors have recently experienced an important redesign in order to deal with the new requirements. This article reports the status of the steering mirrors as well as the fluid dynamic and thermomechanical analyses carried out to validate the design for the normal operation (NO) scenario. The fluid dynamic analyses show that the power dissipated in both steering mirrors due to the mm-wave radiation, nuclear heating, and plasma heat flux can be properly removed with an acceptable mass flow generating admissible pressure drop, temperature rise, and corrosion rate values. The results obtained in the thermomechanical simulation, validated using the American Society of Mechanical Engineers (ASME) code, shows that the steering mirror design is capable of withstanding the expected loads taking place during NO.

실내 작업 건설 기계용 전동식 독립 조향 및 주행 제어 시스템 개발

실내 작업 건설 기계용 전동식 독립 조향 및 주행 제어 시스템 개발

Management of Wet Age-Related Macular Degeneration in Spain: Challenges for Treat and Extend Implementation in Routine Clinical Practice.

Purpose To ascertain wet AMD (wAMD) management patterns in Spain. Methods A two-round Delphi study conducted through a questionnaire-based survey designed from literature review and validated by an independent Steering Committee. Results Forty-nine retina specialists experienced in wAMD participated by answering the two-round study questionnaire. Retina specialists are the main responsible for wAMD diagnosis and monitoring, including visits and associated procedures, with a median time per visit of 15 minutes. Standard treatment strategies are based on anti-VEGF administration, including standard loading dose administration followed by maintenance with aflibercept or ranibizumab (81% of patients). Although treat and extend (T&E) dosing strategy is considered as optimal for wAMD management (78% of the panelists), the main routine healthcare limitations (i.e., visits overload, reduced staff, short visit time, coordination issues, lack of facilities) conduct to self-defined “flexible” strategies, based on T&E and pro-re-nata (PRN) protocols. Conclusion Proactive treatment patterns (T&E) are the preferred ones by the retina specialists in Spain. However, their proper implementation is difficult due to healthcare resource limitations, as well as organisation and logistic issues. The use of anti-VEGF agents with longer duration of action could facilitate the use of strict T&E approaches according to routine clinical practices.

Coordination of Independent Steering and Torque Vectoring in a Variable-Geometry Suspension System

In this paper, the coordination and control design of a variable-geometry suspension is proposed, in which independent steering and torque vectoring are integrated. The motivation of this paper is the research on the novel smart actuators for autonomous urban vehicles, by which various functionalities can be achieved. The goal of this paper is to propose a control design for trajectory tracking with increased reachability domain. Therefore, in this paper, the hierarchical control design of the suspension system using robust and linear-parameter varying (LPV) methods is presented. The robust stability of the hierarchy is guaranteed through the modeling of the uncertainties of different control layers. Furthermore, the coordination of independent steering and torque vectoring is proposed, which is based on a nonlinear reachability analysis of the interventions. The efficiency of the prosed method is presented through the high-complexity simulation software of the vehicle dynamics (CarSim) and the suspension construction (SimMechanics).

Robust H ∞ state feedback control for handling stability of intelligent vehicles on a novel all‐wheel independent steering mode

We propose an H ∞ dynamics controller for an all-wheel independent steering. A norm-bounded method is used to describe the uncertainties in the system. A new reference model aimed at minimising the yaw rate and making the sideslip angle remain the same as the target sideslip angle is proposed; this will help especially when a vehicle changes lanes. Simulation and experimental results indicate that the controller can help improve the handling stability and correct directional problems when the vehicle's direction is changed by the steering angle.

Chassis integrated control for 4WIS distributed drive EVs with model predictive control based on the UKF observer

Four-wheel independent steering (4WIS) system and direct yaw moment control (DYC) have an important influence on vehicle lateral stability. However, DYC has a great effect on the longitudinal velocity, and the capability of 4WIS is limited to stability. To decrease the influence on the longitudinal velocity and improve the stability of electrical vehicles, a chassis controller integrated with a 4WIS system and a DYC system with model predictive control (MPC) is designed. The framework consists of an unscented Kalman filter (UKF) observer and an MPC that contains three blocks: supervisor blocks, upper blocks and lower blocks. First, the sideslip angle, longitudinal velocity and lateral tire forces are estimated by the UKF observer; second, a bicycle model is utilized in the supervisor to calculate the desired values; third, the upper blocks are designed with the MPC to optimize the target steering angles and longitudinal tire forces under the constraints of subsystems; to facilitate the design of the MPC, a nonlinear tire is simplified based on the Taylor expansion method; finally, the target steering angles and longitudinal tire forces are achieved by the lower blocks. The integrated controller is simulated on the co-simulation platform of MATLAB-Carsim. The results show that the proposed integrated controller has less impact on longitudinal velocity and could effectively improve vehicle stability.

Integrated lateral control for 4WID/4WIS vehicle in high-speed condition considering the magnitude of steering

Aiming at the difficulty of vehicle lateral control in high-speed condition, a comprehensive control method that integrates active steering (AS) and direct yaw moment control (DYC) systems is proposed for four-wheel independent driving and four-wheel independent steering (4WID/4WIS) vehicle. According to the characteristics of lateral dynamics in high-speed conditions, different principles are adopted in different steering conditions. In a slight or moderate steering, a decoupling control method is proposed, and a penalty function is used to allocate the involvement of AS and DYC for the over-actuated characteristics of 4WID/4WIS vehicle. While in a large steering, based on sideslip phase plane, handling-oriented and stability-oriented control are proposed in order to realise a fine trade-off between handling and stability performance. A transient layer is introduced in the phase plane to further improve the performance of this controller. And the allocation of active yaw moment is also discussed. Simulation results demonstrate that the proposed integrated control method can effectively improve the lateral dynamics performance of the vehicle in high-speed condition as compared to previous control methods.