Steering Correction Research Articles

Visual control of flight speed inDrosophila melanogaster

Flight control in insects depends on self-induced image motion (optic flow), which the visual system must process to generate appropriate corrective steering maneuvers. Classic experiments in tethered insects applied rigorous system identification techniques for the analysis of turning reactions in the presence of rotating pattern stimuli delivered in open-loop. However, the functional relevance of these measurements for visual free-flight control remains equivocal due to the largely unknown effects of the highly constrained experimental conditions. To perform a systems analysis of the visual flight speed response under free-flight conditions, we implemented a 'one-parameter open-loop' paradigm using 'TrackFly' in a wind tunnel equipped with real-time tracking and virtual reality display technology. Upwind flying flies were stimulated with sine gratings of varying temporal and spatial frequencies, and the resulting speed responses were measured from the resulting flight speed reactions. To control flight speed, the visual system of the fruit fly extracts linear pattern velocity robustly over a broad range of spatio-temporal frequencies. The speed signal is used for a proportional control of flight speed within locomotor limits. The extraction of pattern velocity over a broad spatio-temporal frequency range may require more sophisticated motion processing mechanisms than those identified in flies so far. In Drosophila, the neuromotor pathways underlying flight speed control may be suitably explored by applying advanced genetic techniques, for which our data can serve as a baseline. Finally, the high-level control principles identified in the fly can be meaningfully transferred into a robotic context, such as for the robust and efficient control of autonomous flying micro air vehicles.

A comparison of three steering controllers for off-road vehicles

Many off-road vehicles use electrohydraulic (E/H) actuators for implementing steering controls. However, the high non-linearity of E/H steering systems often results in difficulties in achieving high performance in steering control, especially when it requires only some small steering corrections. Such features of E/H steering systems call for capable control methods to overcome the non-linearity problems in achieving a desirable level of steering performance. This paper presents a comparison of the performance of three commonly used controllers, namely a proportional—integral—derivative (PID) controller, a feedforward-plus-PID (FPID) controller, and a fuzzy controller, for an E/H steering system. To isolate environment influences on the investigation of the controller performance, the comparison tests were implemented on a validated hardware-in-the-loop (HIL) E/H steering system simulator. The results obtained confirmed that both the FPID and fuzzy controllers have superior performance in compensating for system deadband and could achieve more sensitive and accurate small steering corrections than a PID controller.

Warning Reliability and Driver Performance in Naturalistic Driving

This study examines how naturalistic driving performance is influenced by the perceived reliability of an in-vehicle warning system using a unique measure of perceived reliability. Prior studies of warning reliability conducted in simulator and test-track experiments demonstrate that the objective reliability of a warning can influence a driver's responsiveness to that warning. Driver responses to lateral drift warnings (LDWs) were examined to determine if the latency to initiate a corrective steering response was related to the subjective reliability of prior system performance. An operational definition of subjective reliability was developed based on measures of the proportion of LDWs responded to by a steering correction in the preceding 24-hr period - the day proportion. Age, gender, weather condition, light level, road class, weekday status, and day proportion were used to model correction latency in a linear model. A main effect of day proportion was found, suggesting that reaction time to respond decreases by about 375 ms as the day proportion increases from 0 to 1. The study illustrates a method of quantifying subjective reliability and performance using naturalistic data. The results suggest that latency to make a steering correction is inversely related to the perceived reliability of the warning system in the 24 hr preceding the warning. The results have direct application to the method of assessing the efficacy of in-vehicle collision warning systems, suggesting that use of a perceived reliability measure may better predict a driver's disposition to respond to a warning.

Adaptive beamforming with maximum output magnitude calibration in the presence of pointing errors

This Letter deals with robust adaptive array beamformers based on minimum variance distortionless response (MVDR) beamforming with maximum output magnitude. It has been shown that the adaptive eigenspace‐based (ESB) beamformer demonstrates the advantage of less sensitivity to small pointing errors over the MVDR beamformer. However, the ESB beamformer still can't deal with large pointing errors near the edge of the mainlobe. In conjunction with a maximum output magnitude searching approach, the MVDR and ESB with the proposed technique can mitigate pointing error and produce almost the same convergence speed as the MVDR and ESB beamformers under correct steering, respectively. Several computer simulation examples are provided for illustrating the effectiveness of the proposed technique.

Backup Hydrogen Maser Steering System for Galileo Precise Timing Facility

Two hydrogen masers (HMs) are used in the Precise Timing Facility to provide the physical realization of Galileo System Time, insuring the extremely high short‐term stability required for the navigation functions. In order to allow a smooth switch over between backup and primary HMs, the “backup HM steering algorithm” is developed. This acquires the phase difference measured between two HMs, computes a steering correction, and generates the steering correction to the backup HM via a PicoStepper with a 0.1‐picosecond resolution. The algorithm design is based on outlier removal and a proportional‐integral filtering controller. To verify the steering operability and the loop performance, the overall backup HM steering system is simulated using real HM‐HM measurements, and with simulated anomalies (phase/frequency spikes, jumps, and drift).

Modeling of Straight-Line Driving with a Guidance Aid for a Tractor-Driving Simulator

Minor steering corrections are necessary to keep a tractor moving in a straight line. If the factors that cause such steering corrections are not considered in the implementation of a driving simulator, the task of straight-line driving will be both unrealistic and too simple. The objective of this study was to develop and validate a model, for simulation of parallel swathing in a tractor-driving simulator, which accounts for both guidance system error and tractor self-deviation. Guidance system error and tractor self-deviation were both measured by an RTK GPS system. Fourier analysis was used to determine the energy spectrum in high-, medium-, and low-frequency regions. Complex sinusoids which had similar energy distributions to those obtained from field measurements were proposed for both guidance system error and tractor self-deviation. To validate the straight-line driving model, root mean square (RMS) and frequency composition of lateral deviation of the vehicle were determined for both the tractor-driving simulator and several real systems consisting of a tractor, driver, and lightbar guidance device. Six subjects participated in the simulator study. On average, the RMS of lateral deviation was 33 cm. The energy distribution was 32% in the high-frequency region, 39% in the medium-frequency region, and 29% in the low-frequency region. Field experiments with a single driver with seven distinct lightbar guidance systems yielded an average RMS of lateral deviation of 15 cm. The energy distribution was 27% in the high-frequency region, 41% in the medium-frequency region, and 32% in the low-frequency region. Field experiments with seven drivers using a single lightbar guidance device yielded an average RMS of lateral deviation of 30 cm. The energy distribution was 30% in the high-frequency region, 40% in the medium-frequency region, and 30% in the low-frequency region. Field experiments showed close agreement with simulator experiments in terms of the frequency composition of the lateral deviations.

ReflektAS: lane departure prevention system based on behavioural control

As a great portion of fatal accidents is caused by road departures, numerous systems for lateral control have been developed. These systems possess different functionalities, like warning the driver if he tends to depart from the lane or adding a steering torque to reduce the necessity for small steering corrections. To overcome some disadvantages of the classical systems and to develop a system for emergency situations, the knowledge of behavioural principles was utilised. A system based on reflexes has the potential of eliciting reactions reliably and quickly. In a simulator study, the principle was examined and different adjustments of the stimulus used to elicit target behaviour were tested. Subjective and objective data were collected. Results show that the participants trusted the system and perceived it as a valuable contribution to traffic safety. Objective data, like steering angle and measures of lateral position, were analysed and three different types of elicited reactions could be identified. Reaction time, reaction strength and a number of other measures were calculated for each type of reaction. The results confirmed that the system elicits reflexive reactions with very short delays, thus showing its potential for avoiding severe accidents.

A Continuous, In-Chamber Target Tracking and Engagement Approach for Laser Fusion

Target engagement is the process of measuring the target trajectory and directing the driver beams to hit the target at a position that is predicted based on these measurements. New target engagement concepts have been proposed in the last few years to continuously track the targets and to verify that the tracking system is aligned with the driver beams for each shot.For transverse position, a laser beam continuously backlights the target and the position of the Poisson spot in the center of the target’s shadow is measured. Axial target displacement is measured using a laser interferometer and counting interference fringes as the target moves away from the laser source. Final steering corrections use a “glint” reflected off the target ˜1 ms prior to firing the laser beams and collected in a separate Position Sensitive Detector (PSD) for each driver beamlet. The position of the glint on the PSD is compared to the position of an alignment beam that is collinear with the driver beam. Steering corrections are then made based on the difference in position of the two spots reaching the PSD.

Predictor-Corrector Reentry Guidance Algorithm with Path Constraints for Atmospheric Entry Vehicles

The problem of reentry guidance for an atmospheric entry vehicle is taken up for the study with focus on the evolution of a guidance strategy, which satisfies both terminal and path constraints. For this purpose, the numerical predictor–corrector approach is adopted, and an algorithm, based on real-time trajectory planning, is presented. The proposed guidance algorithm generates a feasible trajectory at each guidance cycle during the reentry flight, which is a function of the reference trajectory generated at the previous cycle and the measured parameter dispersions. The predictor steering program includes the bank reversal philosophy, and the corrector algorithm is formulated based on two control parameters and two terminal constraints. The path constraints on heat rate, aerodynamic load, and dynamic pressure are implemented as part of the predictor–corrector algorithm, by designing a control law for following the allowable drag and drag rate profiles. This control law is implemented through steering corrections in each predictor step, which ensures that each predicted trajectory satisfies the path constraints. The performance results for nominal and dispersed cases show that the algorithm steers a typical entry vehicle along a feasible 3-D trajectory, which satisfies both terminal and path constraints.

Plane arrays – Fundamental investigations for correct steering by means of sound field calculations

The most crucial problem with plane arrays is correct steering without grating lobes. The paper deals with optimization of the geometrical parameters and of the steering of phased arrays for water and for testing with the immersion technique. It gives a brief introduction into theory, investigates the existence and magnitude of grating lobes and deals with the limitation of steering angle. It suggest a fitting of steering angles with a fast approach to calculate sound fields. The paper shows also that grating lobes can appear in the transient field for extreme cases even if there are no lobes in the time harmonic field at the center frequency. This contradicts the common expectation. The paper deals also with a water/steel-configuration for testing with immersion technique. It is discussed that grating lobes and the limitation of steering in water strongly effect the sound field transmitted into steel.

Aberration correction in an adaptive free-space optical interconnect with an error diffusion algorithm

Aberration correction within a free-space optical interconnect based on a spatial light modulator for beam steering and holographic wavefront correction is presented. The wavefront sensing technique is based on an extension of a modal wavefront sensor described by Neil et al. [J. Opt. Soc. Am. A 17, 1098 (2000)], which uses a diffractive element. In this analysis such a wavefront sensor is adapted with an error diffusion algorithm that yields a low reconstruction error and fast reconfigurability. Improvement of the beam propagation quality (Strehl ratio) for different channels across the input plane is achieved. However, due to the space invariancy of the system, a trade-off among the beam propagation quality for channels is obtained. Experimental results are presented and discussed.

A Two-Point Visual Control Model of Steering

When steering down a winding road, drivers have been shown to use both near and far regions of the road for guidance during steering. We propose a model of steering that explicitly embodies this idea, using both a 'near point' to maintain a central lane position and a 'far point' to account for the upcoming roadway. Unlike control models that integrate near and far information to compute curvature or more complex features, our model relies solely on one perceptually plausible feature of the near and far points, namely the visual direction to each point. The resulting parsimonious model can be run in simulation within a realistic highway environment to facilitate direct comparison between model and human behavior. Using such simulations, we demonstrate that the proposed two-point model is able to account for four interesting aspects of steering behavior: curve negotiation with occluded visual regions, corrective steering after a lateral drift, lane changing, and individual differences.

Driver-Compatible Steering System for Wide Speed-Range Path Following

This paper presents a method of realizing driver-compatible steering systems in ITS, for vehicles that have capabilities of carrying out path following tasks. The method aims to maintain steering smoothness from high to low vehicle speed, including nonhighway environments, which may involve tighter turns. Multiple look-ahead points are introduced, which allows to guide the vehicle with minimum steering corrections, while maintaining the tracking accuracy. The look-ahead points, one for recognizing the path deviation for the error-cancel feedback control and the other for predicting the necessary steering for feedforward control, are varied independently according to vehicle speed. This appropriately distributes the controls and determines the final output of the steering system. The look-ahead distance for feedforward is extended longer than the look-ahead distance for feedback at low velocities, and is shortened according to velocity increase. The look-ahead distance for the feedback acts the opposite. The steering control system was implemented onto an experimental vehicle and tests were conducted. The results of path following experiments show that the method is capable of realizing smooth steering control when tracking paths involving various turns, in a wide speed range, while maintaining tracking accuracy.

New chicane magnet design for insertion device straights at the Advanced Light Source

A chicane magnet incorporating counter-rotating permanent magnet pairs together with trim coils has been designed for use in the Advanced Light Source (ALS) straights in conjunction with two insertion devices. In particular, this design is being developed for use in the existing beam line (BL) 4 elliptically polarizing undulator (EPU) straight and in the BL11 EPU straight, currently under design and construction. The purpose of the chicane is to provide a fixed angular separation between two successive EPU photon fans, and to correct steering perturbations resulting from EPU polarization state changes. Polarization changes occur on the time scale of one second; associated steering corrections must be accomplished in less than a second. Hysteresis associated with conventional iron core electromagnets prevents fast steering correction to the required precision. This consideration motivated the iron-free design presented here.

FUZZY CONTROL OF ELECTROHYDRAULIC STEERING SYSTEMS FOR AGRICULTURAL VEHICLES

This paper presents the development of a fuzzy steering controller for wheel–type agricultural vehicles with an electrohydraulic (E/H) steering system. The fuzzy controller,which consisted of a variable fuzzifier, an inference engine with a steering control rulebase, and a control signal defuzzifier, was developed based on a common–sense model of agricultural vehicle steering. The controller implemented steering corrections based upon the desired steering rate and the error between the desired and the actual wheel angles. Test results indicated that this controller could be used on vehicles with similar steering actuating mechanisms. Limited tuning on fuzzy membership functions was used to account for physical differences between vehicles. This fuzzy controller achieved prompt and accurate steering performance on both a hardware–in–the–loop electrohydraulic steering simulator and on an agricultural tractor. The adoption of this fuzzy controller can significantly reduce the time and costs in the design of steering controllers for agricultural vehicles.

Survey of New Zealand truck driver fatigue and fitness for duty

This paper presents recent research into compliance with current driving hours regulations, the effectiveness of using driving hours to predict fatigue, and alternative compliance and enforcement options. The paper describes results of a major survey of truck driver fatigue in New Zealand, a review of international compliance and enforcement procedures, and research focussing on the social forces and influences that affect truck drivers. The survey of truck drivers was based on interviews and performance tests collected from 600 truck drivers at depots, wharves, markets, and other locations throughout the North Island of New Zealand. The interviews included: questions on driver demographic and work/rest patterns, drivers' attitudes towards fatigue, propensity towards daytime sleepiness, and a self-assessment of the driver's momentary level of fatigue. In addition, a simulator-based performance test of driving was undertaken. The performance test included a combination of a standard driving task, a dual-axis sub-critical tracking task (maintaining speed and steering in a controlled but unstable environment, a virtual roadway affected by the appearance of random wind gusts requiring steering correction), and a tertiary or side-task requiring driver monitoring and periodic responses. The initial results from the first 100 drivers have found a sizable number of drivers exceeding the allowable driving hours, high levels of fatigue and sleepiness, and interesting differences between line-haul and local delivery drivers. A related research project into the social processes and relationships that affect truck drivers has resulted in a good understanding of the social conditions that influence cultural change and the actions of truck drivers and fleet managers. In this paper we will have particular regard to these processes in the construction of ideas concerning safety. This includes an understanding of the role of major stakeholders, such as freight forwarders and the enforcement agencies with respect to drivers and their conditions, actions and understanding of the road transport industry. This knowledge coupled with the survey results and an understanding of compliance and enforcement alternatives will be used to explore potential fatigue management options.

Indoor Vehicle Lateral Dynamics Simulation. 1st Report. System Framework.

A four-wheel flat belt chassis dynamometer with swiveling mechanisms had been developed mainly for indoor cornering tests. On the tester, a testing vehicle is restrained with wire ropes, and its longitudinal and lateral characteristics are well reproduced including body attitude. Because lateral response simulation in the set-up is consistent only in steady state in the strict sense, new techniques for lateral transient response are introduced in this paper. To reproduce the precise tire slip angles, the vehicle is equipped with Corrective Steering Systems for front and rear wheels. The CSSs are controlled in accordance with the real-time vehicle model which contains only the vehicle's mass property by making use of the vehicle restraint forces. The resultant testing system is proved to have sufficient preciseness in the overall running scenarios, and can be applied to various vehicle tests.

Flight motor patterns of locusts responding to thermal stimuli

Correctional and intentional steering manoeuvres in locusts differ in several important respects. The most profound difference between the two is the production of large forewing asymmetries in angle of elevation during the downstroke in intentional steering that are not obvious in correctional steering. We investigated the flight motor patterns during intentional steering responses to a radiant heat source. We found asymmetries in the timing of forewing first basalar (m97) activity on the left and right sides that were strongly and positively correlated with forewing asymmetries. Timing asymmetry in the second basalar (m98) and pleuroalar (m85) muscles was not significantly different from the changes observed in m97. The hindwing first basalar (m127) shifted its asymmetry in the opposite direction. The forewing subalar muscle (m99) did not shift its asymmetry with the same magnitude as m97, but instead was phase-shifted relative to m97 on the left and right sides, suggesting its role as a supinator. We conclude that large asymmetries in the elevation angle of the forewings during the downstroke, as are evident in intentional steering, are generated by bulk shifts in the activation times of forewing depressor muscles to cause a relative shift in the time of stroke reversals of the two forewings.

A function generating differential mechanism for an exact solution of the steering problem

The paper presents an original solution to the problem of correct steering. It is obtained by modifying the well-known six-bar linkage with the addition of a differential mechanism between the steering wheel and the original linkage. The differential mechanism, coupled to a higher pair, resolves the single input coming from the steering wheel into two outputs satisfying the condition of correct steering. Forces transmitted by the higher pair are evaluated through a static analysis. A numerical simulation, with practical criteria for the selection of relevant design variables, concludes the paper.

A two-way optical interconnection network using a single mode fiber array

We present a dynamic free space interconnection network for single mode fibers. The architecture consists of a two-way imaging geometry involving only one single mode fiber array. Input and output fibers belong to the same fiber array. Programmable and fixed diffractive optical elements are used for beam steering and wavefront correction. We show that the network ensures favorable conditions for launching and allows for a high interconnection volume with minimal insertion losses at 2.5 Gb/s. The architecture is also adapted to the use of binary electrically addressed spatial light modulators.