Steering Function Research Articles

Electric Control of Spin‐Orbit Coupling in Graphene‐Based Nanostructures with Broken Rotational Symmetry

AbstractSpin and orbital angular momenta of light are important degrees of freedom in nanophotonics which control light propagation, optical forces, and information encoding. Here, it is shown that graphene‐supported plasmonic nanostructures with broken rotational symmetry provide a surprising spin to orbital angular momentum conversion, which can be continuously controlled by changing the electrochemical potential of graphene. Upon resonant illumination by a circularly polarized plane wave, a polygonal array of indium‐tin‐oxide nanoparticles on a graphene sheet generates the scattered field carrying electrically‐tunable orbital angular momentum. This unique photonic spin‐orbit interaction occurs due to the strong coupling between graphene plasmon polaritons and localized surface plasmons of the nanoparticles and leads to the controlled directional excitation of graphene plasmons. The tuneable spin‐orbit conversion paves the way for high‐rate information encoding in optical communications, electric steering functionalities in optical tweezers, and nanorouting of higher‐dimensional entangled photon states.

Global Vision-Based Formation Control of Soft Robotic Fish Swarm.

Possessing the attributes of high adaptability and low cost, soft robotic individuals can further coordinate and form into a swarming system, enhancing the performances as well as functions in practical applications. However, the formation control of soft robotic swarm remains challenging mainly due to the limitation in relatively low precision and slow response of the soft actuators. In this work, a soft robotic fish swarm system with global vision positioning was studied. The soft robotic fish used in the project is driven by a hybrid power-control system, in which the soft dielectric elastomers and the rigid electrical servo provide forward propulsion and controllable steering function, respectively. Results show that soft robotic fish swarm can quickly shift their formations, mimicking three typical swarming behaviors of natural creatures: highly parallel group, encircling, and torus. The system design and controlling principles of the soft robotic fish swarm may guide the future research of soft robots and robotic swarms, specifically for underwater applications.

Manipulating deformable objects by interleaving prediction, planning, and control

We present a framework for deformable object manipulation that interleaves planning and control, enabling complex manipulation tasks without relying on high-fidelity modeling or simulation. The key question we address is when should we use planning and when should we use control to achieve the task? Planners are designed to find paths through complex configuration spaces, but for highly underactuated systems, such as deformable objects, achieving a specific configuration is very difficult even with high-fidelity models. Conversely, controllers can be designed to achieve specific configurations, but they can be trapped in undesirable local minima owing to obstacles. Our approach consists of three components: (1) a global motion planner to generate gross motion of the deformable object; (2) a local controller for refinement of the configuration of the deformable object; and (3) a novel deadlock prediction algorithm to determine when to use planning versus control. By separating planning from control we are able to use different representations of the deformable object, reducing overall complexity and enabling efficient computation of motion. We provide a detailed proof of probabilistic completeness for our planner, which is valid despite the fact that our system is underactuated and we do not have a steering function. We then demonstrate that our framework is able to successfully perform several manipulation tasks with rope and cloth in simulation, which cannot be performed using either our controller or planner alone. These experiments suggest that our planner can generate paths efficiently, taking under a second on average to find a feasible path in three out of four scenarios. We also show that our framework is effective on a 16-degree-of-freedom physical robot, where reachability and dual-arm constraints make the planning more difficult.

A prebiotic-enhanced lipid-based nutrient supplement (LNSp) increases Bifidobacterium relative abundance and enhances short-chain fatty acid production in simulated colonic microbiota from undernourished infants.

Undernutrition remains a public health problem in the developing world with an attributable under-five death proportion of 45%. Lower gut microbiota diversity and poor metabolic output are associated with undernutrition and new therapeutic paths may come from steering gut microbiota composition and functionality. Using a dynamic gut model, the Simulator of Human Intestinal Microbial Ecosystem (SHIME®), we investigated the effect of a lipid-based nutrient supplement enriched with prebiotics (LNSp), compared to LNS alone and control treatment, on the composition and metabolic functionality of fecal microbiota from three infants suffering from undernutrition. LNS elicited a significant increase in acetate and branched-chain fatty acid production, and a higher relative abundance of the genera Prevotella, Megasphaera, Acinetobacter, Acidaminococcus and Pseudomonas. In contrast, LNSp treatment resulted in a significant 9-fold increase in Bifidobacterium relative abundance and a decrease in that of potential pathogens and detrimental bacteria such as Enterobacteriaceae spp. and Bilophila sp. Moreover, the LNSp treatment resulted in a significantly higher production of acetate, butyrate and propionate, as compared to control and LNS. Our results suggest that provision of prebiotic-enhanced LNS to undernourished children could be a possible strategy to steer the microbiota toward a more beneficial composition and metabolic activity. Further in vivo investigations are needed to assess these effects and their repercussion on nutritional status.

Design and Research of Omni-directional Moving AGV

Omni-directional mobile AGV can operate flexibly in a narrow space, which can replace heavy and dangerous labour to a greater extent and improve labour productivity. In this paper, the steering wheel integrated with walking and steering functions is taken as the driving unit, and the main research contents include: through digital structure design, the chassis structure and electrical control system of omnidirectional AGV are designed. Experiments show that the design realizes flexible operation of zero turning radius and 360-degree omnidirectional movement in narrow space, and meets the requirements of robot handling operation in complex environment.

Optical switching and beam steering with a graphene-based hyperprism

It is well established that the topological transition of the iso-frequency surface (IFS) of hyperbolic metamaterials from the ellipsoid to hyperboloid provides unique capabilities for controlling the propagation of the wave. Here, we present a graphene-based hyperprism (GHP) structure that uses an electronically controlled modulation strategy to achieve optical switching and wide-angle beam steering functions. Numerical simulation results show that, by regulating the chemical potential of GHP, the optical switching system can achieve high transmission (97%) and zero transmission, as well as the beam steering system can reach a maximum adjustable angle of 52.94°. Furthermore, the effects of Fermi energy and relaxation time on transmittance are also investigated. These works may provide new opportunities for applications such as optical data storage, modulators, and integrated photonic circuits.

An Efficient RRT-Based Framework for Planning Short and Smooth Wheeled Robot Motion Under Kinodynamic Constraints

This article presents a framework that extends a rapidly exploring random tree (RRT) algorithm to plan the motion for a wheeled robot under kinodynamic constraints. Unlike previous RRT-based path planning algorithms that apply complex steer functions during a path sampling phase, this framework uses a straight line to connect a pair of sampled waypoints such that an obstacle-free path can be quickly found. This path is further pruned by the short-cutting algorithm. Under the kinodynamic constraints, we propose a motion-control law that is guided by a pose-based steer function for the robot to reach its destination in a short time. A path deformation strategy is presented that shifts the waypoint away from the collision point such that the trajectory can be generated without any collision. Simulation results demonstrate that the proposed framework needs less computation to generate a smoother trajectory with shorter length than its peers, and experimental results show that simulated trajectories of our controller are very close to real ones and the performance is better than that of a prior pose-based controller.

Active steering control strategy for rail vehicle based on minimum wear number

ABSTRACT Active steering technology is an effective method to solve the contradiction between curving performance and running stability of traditional bogie. In this study, an integrated active steering device was developed to integrate wheelset constraints and actuators. In addition, to study the minimum wear number control strategy, the existence of an optimal steering level that minimises the wear number was corroborated by a theoretical derivation based on the single wheelset model. Later, this research method was extended to the complete vehicle lateral dynamics model and steady-state solutions at different active steering levels were analysed. The results demonstrate that at optimal steering control, wear number is the lowest. This state is less affected by the running velocity, stiffness of the primary suspension, tread taper, and creep state, which are determined by the wheelbase and track curvature. The lateral forces of rail-vehicle wheels with an active steering function at different steering levels were measured using instrumented wheelsets. Furthermore, the accuracy of the simulation model was verified by comparing the experimental data with simulation results. Finally, the wear number of test vehicles at different steering levels were predicted using this model, and the control strategy proposed in this investigation was validated.

Multifunctional optofluidic lens with beam steering.

In this paper, we demonstrate a multifunctional optofluidic (MO) lens with beam steering, which is actuated by electrowetting effect. A liquid lens chamber and a liquid prism chamber are stacked to form the MO lens. When the liquid lens chamber is actuated with voltage, the curvature of liquid-liquid interface changes accordingly and the focal length of the liquid lens can be varied. In the liquid prism chamber, a navigation sheet is just placed on the position of the liquid-liquid interface. When the liquid prism chamber is applied with voltage, the navigation sheet can be tilted to different angles in order to adjust the beam steering angle and keep high beam quality. Thereby, the MO lens has the zoom lens and the beam steering functions. The experiments show that the focal length can be tuned from -180 mm to -∞ and +∞ to 161 mm and the maximum beam tilt angle can be adjusted from 0° to 22.8° when the voltage is applied on one side of the electrode. The proposed MO lens can be applied in zoom imaging system, laser detecting system, and lighting system.

Mechatronics and Remote Driving Control of the Drive-by-Wire for a Go Kart.

This research mainly aims at the construction of the novel acceleration pedal, the brake pedal and the steering system by mechanical designs and mechatronics technologies, an approach of which is rarely seen in Taiwan. Three highlights can be addressed: 1. The original steering parts were removed with the fault tolerance design being implemented so that the basic steering function can still remain in case of the function failure of the control system. 2. A larger steering angle of the front wheels in response to a specific rotated angle of the steering wheel is devised when cornering or parking at low speed in interest of drivability, while a smaller one is designed at high speed in favor of driving stability. 3. The operating patterns of the throttle, brake, and steering wheel can be customized in accordance with various driving environments and drivers’ requirements using the self-developed software. The implementation of a steer-by-wire system in the remote driving control for a go kart is described in this study. The mechatronic system is designed in order to support the conversion from human driving to autonomous driving for the go kart in the future. The go kart, using machine vision, is wirelessly controlled in the WiFi frequency bands. The steer-by-wire system was initially modeled as a standalone system for one wheel and subsequently developed into its complete form, including front wheel steering components, acceleration components, brake components, a microcontroller, drive circuit and digital to analog converter. The control output section delivers the commands to the subsystem controllers, relays and converters. The remote driving control of the go kart is activated when proper commands are sent by the vehicle control unit (VCU). All simulation and experiment results demonstrated that the control strategies of duel motors and the VCU control were successfully optimized. The feasibility study and performance evaluation of Taiwan’s go karts will be conducted as an extension of this study in the near future.

Low-Cost GNSS Software Receiver Performance Assessment

The Software-Defined Receiver (SDR) is a rapidly evolving technology which is a useful tool for researchers and allows users an extreme level customization. The main aim of this work is the assessment of the performance of the combination consisting of the Global Navigation Satellite Systems Software-Defined Receiver (GNSS-SDR), developed by CTTC (Centre Tecnològic de Telecomunicacions de la Catalunya), and a low-cost front-end. GNSS signals were acquired by a Nuand bladeRF x-40 front-end fed by the TOPCON PG-A1 antenna. Particular attention was paid to the study of the clock-steering mechanism due to the low-cost characteristics of the bladeRF x-40 clock. Two different tests were carried out: In the first test, the clock-steering algorithm was activated, while in the second, it was deactivated. The tests were conducted in a highly degraded scenario where the receiver was surrounded by tall buildings. Single-Point and Code Differential positioning were computed. The achieved results show that the steering function guarantees the availability of more solutions, but the DRMS is quite the same in the two tests.

Multipath transmission control protocol–based multi-access traffic steering solution for 5G multimedia-centric network: Design and testbed system implementation

Various technologies have been developed for the efficient use of the multiple radio access technologies resource at the radio access network level or other network levels to improve user service quality in mobile communication networks. In long-term evolution, mobile carriers are commercializing radio access network-level traffic aggregation technologies such as licensed-assisted access-long-term evolution, long-term evolution-unlicensed, and long-term evolution-wireless local area network aggregation, which use the multi-accesses of the 3rd Generation Partnership Project and WiFi, and the multipath transmission control protocol–based traffic aggregation technologies at the L3 network level. The standardization of 3rd Generation Partnership Project Release 16, which is scheduled to be completed by 2020, is under progress to support the traffic aggregation technology at the L3 network level through a multi-access 5G network. Multipath transmission control protocol is also considered as a traffic aggregation technology. However, it is difficult to apply the multipath transmission control protocol employment model used in long-term evolution to the 5G network structure as it is due to the change to a common core architecture that accommodates multiple radio access technologies through one common interface. Therefore, this article proposes an optimal 5G system architecture and a multipath transmission control protocol adaptation method to support the access traffic steering function based on multipath transmission control protocol in a 3rd Generation Partnership Project 5G mobile communication network. We have verified the development of the multipath transmission control protocol–based multi-access traffic steering technology by implementing the proposed solution in a commercial server on a testbed based on the 5G system standard of 3rd Generation Partnership Project Release 15. Furthermore, this article defines problems that occur when implementing the multipath transmission control protocol–based multi-access traffic steering system and proposes relevant solutions. Based on the implementation results, it is demonstrated that the proposed multipath transmission control protocol–based multi-access traffic steering system can perform traffic steering in the 3rd Generation Partnership Project 5G network.

Geometrical Analysis and Design of Tension-Actuated Ackermann Steering System for Quad-Wheeled Robots

The tension-actuated steering system is a vehicular steering design that comprises a motorized gear system, pulleys, inelastic string, main steering bar, and a strain gauge. This development is aimed to produce a steering design that could enhance the efficiency of steering systems in quad-wheeled (i.e. four-wheeled) robots. In this work, the steering system of conventional passenger vehicles and existing quad-wheeled robots are reviewed and their technical deficiencies are improved based on cost, power and production factors. Thus, the tension-actuated steering system is proposed as a solution for mechanizing steering functions in quad-wheeled robots. It is expected that this work will stimulate interest and enthusiasm.

Focusing and Frequency Smoothing for Arbitrary Arrays With Application to Speaker Localization

The coherent signal subspace method (CSSM) enables the direction-of-arrival (DoA) estimation of coherent sources with subspace localization methods. The focusing process that aligns the signal subspaces within a frequency band to its central frequency is central to the CSSM. Within current focusing approaches, a direction-independent focusing approach may be more suitable for reverberant environments since no initial estimation of the sources' DoAs is required. However, these methods use integrals over the steering function, and cannot be directly applied to arrays around complex scattering structures, such as robot heads. In this article, current direction-independent focusing methods are extended to arrays for which the steering function is available only for selected directions, typically in a numerical form. Spherical harmonics decomposition of the steering function is then employed to formulate several aspects of the focusing error. A case of two coherent sources is studied and guidelines for the selection of the frequency smoothing bandwidth are suggested. The performance of the proposed methods is then investigated for an array that is mounted on a robot head. The focusing process is integrated within the direct-path dominance (DPD) test method for speaker localization, originally designed for spherical arrays, extending its application to arrays with arbitrary configurations. Finally, experiments with real data verify the feasibility of the proposed method to successfully estimate the DoAs of multiple speakers under real-world conditions.

Four-Wheel Differential Steering Control of IWM Driven EVs

This paper aims to realize the four-wheel differential steering function of an in-wheel motor (IWM) driven electric vehicle (EV) with a steer-by-wire (SBW) system. The dynamic models of four-wheel differential steering vehicle (4WDSV) and four-wheel steering vehicle (4WSV) are established, and a front-wheel steering vehicle (2WSV) with the neutral steering characteristics and a drop filter of the sideslip angle is employed as the reference model to provide the ideal yaw rate and sideslip angle. According to the reference model, the decoupling and fractional PI λ D μ controllers are designed for the 4WSV to obtain the standard inputs, i.e., the front and rear wheel steering angles, which is finally drawn as the MAP. Furthermore, the sliding mode controller (SMC) and torque distributor are designed to control the 4WDSV to have the same yaw rate as the 4WSV, whose inputs are consulted from the MAP drawn in advance according to the vehicle speed. The simulation results of several vehicle models with/without the controller of two working conditions (reverse and in phase steering) are presented, which indicates that the proposed decoupling and fractional PI λ D μ controller for the 4WSV is effective to obtain its standard inputs, and the proposed SMC and torque distributor for the 4WDSV ensure that it has the same yaw rate as the 4WSV, as well as the good robustness.

Visible-frequency meta-gratings for light steering, beam splitting and absorption tunable functionality.

Diffractive grating and plasmonic metasurface have always been developing as two parallel optical domains, which have not met for studying their hybridization to discover new applications and potentials. Here, we proposed a novel meta-grating design, which hybridizes the metasurface interfacial gradient with the blazed grating profile. The unique architecture takes advantage of both grating effect and plasmonic resonances with minimum cross-coupling, thus leading to the polarization-selective behaviors to steer different polarized light to drastically inverse directions (> 90°). Furthermore, the hybridized surface also exhibits angle-dependent broadband absorptive tunability (∼ 5% - 86%) by migrating the strong blazed order and plasmonic order at the far field. We believe that the integrated meta-grating device would suggest various potential applications including polarization beam splitters, high signal-to-noise ratio (SNR) optical spectrometer, high-efficiency plasmonic couplers and filter, etc.

Low-Cost Transmitarray Antenna Designs in V-Band based on Unit-Cells with 1 Bit Phase Resolution

Abstract This paper presents the design and characterization of linearly polarized low-cost transmitarray antennas with ± 70° azimuth beamforming range in V-band in order to add beam steering functionality to existing radar front ends. The transmitarray antennas are composed of 13 × 13 planar unit-cells. The unit-cells consist of two layers of RO4350B laminate and provide a one bit phase resolution. The desired unit-cell behavior has been validated by simulations and measurements. Eight transmitarrays with different phase distributions have been designed and fabricated to realize different beam steering angles in azimuth. The experimental characterization of the radiation patterns shows the desired performance in the frequency range from 59 GHz to 63 GHz. Additionally, steering angle combinations in azimuth and elevation up to 40° have been realized and successfully demonstrate by measuring the 2D radiation pattern.

Functionability Analysis of Redundant Mechatronic Systems in Bond Graph Framework

A redundant system can continue to perform its intended function in a faulty condition using its multiple configurations. However, the performance may be degraded due to varying functional performance of each configuration. Thus, redundancy improves the reliability of a system. This article presents a method to analyze the level of functional performance of a redundant system with faults. In this article, a new indicator, called functionability, is proposed for a class of redundant systems, namely engineering mechatronic systems. The developed method is integrated with the bond graph based theory of fault diagnosis, in order to develop a methodology for the functionability analysis of redundant systems. The developed methodology is applied on the steering function of a heavy redundant mobile robot called Robutainer. Due to redundancy, Robutainer shows multiple steering configurations, namely front, rear, and dual. The approach is validated through experiments and real-time cosimulation of Robutainer for trajectory tracking in a port environment and considering different components faults in its multidomain hybrid steering system.

Method of automatic steering system design and parameter optimisation for small tractors

In order to improve the operational efficiency and quality of small tractors, the original manual steering system needs to be renovated to include automatic steering functionality, which is the basis of autonomous navigation. Here, a modification method based on the steering circuit of a Dongfanghong SG250 tractor and a method to calculate the virtual steering angle is proposed. A small tractor steering model is established from the step response data of the system, and a PD controller for this model is also designed. The PD controller can also adapt to varying tractor speeds for optimal functionality in changing operational conditions, and a parameter optimisation approach for the speed-adaptive PD controller is proposed. Test results show that at a speed of 0.5 m s−1, the steady-state error in the step response is 0.32°, the percentage error is 2.3%, the overshoot is 1.86°, and the percentage overshoot is 13.7%. For a ramp response, the average signal latency is 0.82 s and the steady-state error is 0.25°. The ability of the PD to adapt to changing speeds is also tested at different speeds. The results show that the steering system performs well.

Catheter steering in interventional cardiology: Mechanical analysis and novel solution.

In recent years, steerable catheters have been developed to combat the effects of the dynamic cardiac environment. Mechanically actuated steerable catheters appear the most in the clinical setting; however, they are bound to a number of mechanical limitations. The aim of this research is to gain insight in these limitations and use this information to develop a new prototype of a catheter with increased steerability. The main limitations in mechanically steerable catheters are identified and analysed, after which requirements and solutions are defined to design a multi-steerable catheter. Finally, a prototype is built and a proof-of-concept test is carried out to analyse the steering functions. The mechanical analysis results in the identification of five limitations: (1) low torsion, (2) shaft shortening, (3) high unpredictable friction, (4) coupled tip-shaft movements, and (5) complex cardiac environment. Solutions are found to each of the limitations and result in the design of a novel multi-steerable catheter with four degrees of freedom. A prototype is developed which allows the dual-segmented tip to be steered over multiple planes and in multiple directions, allowing a range of complex motions including S-shaped curves and circular movements. A detailed analysis of limitations underlying mechanically steerable catheters has led to a new design for a multi-steerable catheter for complex cardiac interventions. The four integrated degrees of freedom provide a high variability of tip directions, and repetition of the bending angle is relatively simple and reliable. The ability to steer inside the heart with a variety of complex shaped curves may potentially change conventional approaches in interventional cardiology towards more patient-specific and lower complexity procedures. Future directions are headed towards further design optimizations and the experimental validation of the prototype.