Look-ahead Distance Research Articles

3DOF Adaptive Line-Of-Sight Based Proportional Guidance Law for Path Following of AUV in the Presence of Ocean Currents

In order to achieve high-precision path following of autonomous underwater vehicle (AUV) in the horizontal plane, a three degrees-of-freedom adaptive line-of-sight based proportional (3DOFAPLOS) guidance law is proposed. Firstly, the path point coordinate system is introduced, which is suitable for the conversion of an arbitrary path. Then, the appropriate look-ahead distance is obtained by an improved adaptive line-of-sight (ALOS) according to three degrees-of-freedom (3DOF), including the cross-track error, the curvature of reference path, and the forward speed. Moreover, combining three degrees-of-freedom ALOS (3DOFALOS) with proportional guidance law, the desired heading is calculated considering the drift angle. 3DOFAPLOS has two functions: in the convergence stage, 3DOFALOS plays a leading role, making AUV converge to the path more quickly and smoothly. In the guidance stage, proportional guidance law plays a major role in effectively resisting the influence of drift angle and making AUV sail along the reference path. If the path is curved, 3DOFALOS makes contributions in both stages, adjusting look-ahead distance in real time with respect to curvature. The stability of the designed closed system is proved by Lyapunov theory. Both simulation and experiment results have verified that 3DOFAPLOS has a satisfactory result, which improves tracking performance more than 50% compared with the traditional line-of-sight (LOS). Specifically, the mean average error (MAE) of path following under 3DOFAPLOS can be reduced by about 60%, and the root mean square error (RMSE) can be reduced by about 50% compared with LOS.

Curved Path Following for Unmanned Surface Vehicles With Heading Amendment

This article presents two interrelated problems-along tracking and cross tracking-in guidance design for curved path following for unmanned surface vehicles. Since these two types of directional tracking are interactively constrained in most research work, an iteration mechanism is first put forward to optimize the path parameter in each closed loop such that along tracking will not affect cross tracking in the subsequent time period. An extended line-of-sight (ELOS) guidance principle is then proposed by varying the look-ahead distance with the cross-track error such that sideslip in cross tracking can be promptly compensated through vehicle heading amendment. Both simulation and experimental results verify the effectiveness of the proposed methods, which perform better than the conventional line-of-sight (LOS) and integral LOS (ILOS) guidance laws.

Synthesis of Robust Lane Keeping Systems: Impact of Controller and Design Parameters on System Performance

The lane keeping system (LKS), a promising driver assistance system, is essential for autonomous vehicles. In realworld road conditions, it can be quite challenging because LKS must stay within the lane without causing passenger discomfort while both disturbances (e.g., road curvature, wind gusts, and hydroplaning) and model uncertainties in parameters [e.g., vehicle mass, center of gravity (CG), and tire cornering stiffness] are present. In this paper, the performance limits and tradeoffs between three performance criteria (lane tracking, stability robustness, and passenger comfort) are first investigated by exploring the entire design space of three prominent controllers, i.e., proportional-integral-derivative, linear-quadratic- Gaussian, and H-infinity (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> ). Then, a sensitivity study on the vehicle parameters is conducted in order to investigate the impact of the parameters on the three performance metrics. Based on the aforementioned studies, this paper concludes that a robust controller can provide the maximum performance limit with respect to the lane tracking and stability robustness, when properly designed. However, it is observed that the robust controller is still sensitive to a few design and model parameters, such as look-ahead distance and CG. Therefore, the sensitivity study suggests that for vehicles with excessive mass and CG changes, such as SUVs and trucks, the adaptation of controller and look-ahead distance may be necessary to maximize both tracking performance and passenger comfort over a wide range of vehicle speeds.

Optimal Predictive Eco-Driving Cycles for Conventional, Electric, and Hybrid Electric Cars

In this paper, the computation of eco-driving cycles for electric, conventional, and hybrid vehicles using receding horizon and optimal control is studied. The problem is formulated as consecutive-optimization problems aiming at minimizing the vehicle energy consumption under traffic and speed constraints. The impact of the look-ahead distance and the optimization frequency on the optimal speed computation is studied to find a tradeoff between the optimality and the computation time of the algorithm. For the three architectures considered, simulation results show that in urban driving conditions, a look-ahead distance of 300-500 m leads to a sub-optimality less than 1% in the energy consumption compared to the global solution. For highway driving conditions, a look-ahead distance of 1-1.5 km leads to a sub-optimality less than 2% compared to the global solution.

Tradeoffs for Routing Flights in View of Multiple Weather Hazards

Adverse weather impacts the safety and efficiency of aviation. Convective storms, turbulence, and icing are aviation weather hazards that can lead to unpleasant rides and, in the worst case scenario, pose safety risks. Commercial flight route planning tools are largely based on wind optimization, and the daily air traffic flow discussion is heavily focused on avoidance of deep convective storms. Other hazards such as icing (mostly an issue for general aviation) and turbulence have to be manually accounted for by a dispatcher. Routing solutions favoring avoidance of convective storms can result in undesired outcomes such as significant encounters or extended duration of turbulence. This study examines various flight routing approaches, taking into account multiple weather hazards for a range of decision time horizons. A range of time horizons (that is, look-ahead distances) is used to assess the potential benefits of using weather uplinks (for example, onto an electronic flight bag) as compared to the limited information available through the onboard radar. The paper provides a glance at how to improve trajectory-based operations for safe, efficient, and comfortable airborne travel in the future.

Application of a 3D tractor-driving simulator for slip estimation-based path-tracking control of auto-guided tillage operation

Successful adoption of auto-steering agricultural vehicles in Korean paddy fields depends on the ability to accurately follow a full path, including straight and curved paths for agricultural tasks and headland turning in each row, in the presence of sliding caused by wet ground conditions in relatively small fields. To improve the performance of an autonomous tillage tractor originally developed in our previous study, this article describes a simulation study, conducted using a 3D computer simulator, that accounts for the slippery motion of a virtual tractor on ground with varying adherence properties, In addition, this study performed field evaluation of an auto-guided tillage tractor equipped with a slip estimation-based path-tracking algorithm that is robust to slippage in paddy fields. The test platform was built with a 60-kW tractor equipped with an RTK-GPS (real-time kinematic-global positioning system) and IMU (inertial measurement unit) system, a navigation controller that could estimate the sideslips of the tractor in real-time, and a three-point hitch dynamometer that could measure tillage drafts. The results of the computer simulation confirmed that the slip estimation-based path-tracking algorithm was superior in guiding the tractor along curved paths on the ground with relatively low coefficients of cornering stiffness by reducing the lateral deviations as compared with those obtained with the conventional look-ahead distance method. In field tests run in an arable field, the autonomous tillage tractor equipped with the slip observer algorithm demonstrated improved performance as compared to the previously developed system by reducing the RMSE (root mean square error) for lateral deviation on curved paths from 29 cm to 15 cm.

Multirate Lane-Keeping System With Kinematic Vehicle Model

In this paper, a novel multirate lane-keeping system (LKS) is introduced by using a kinematic-based model considering a look-ahead distance. First, we developed a kinematic lateral motion model for LKS with respect to the road. To increase a system damping of vehicle, the unique look-ahead output measurement matrix was introduced. The decentralized multirate lane-keeping control scheme with a multirate Kalman filter was also applied to resolve the asynchronous and irregular sampling time of multi sensors in autonomous vehicles. We validated the performance of the proposed kinematic-based multirate LKS using the dynamic vehicle solver CarSim, MATLAB/Simulink, and electric power steering hardware-in-the-loop system. Experimental validation was also conducted using a real test vehicle. Both simulation and experimental results showed that the proposed kinematic-based LKS performed lane-keeping capability comparable to that of dynamic-based LKS. In particular, the experimental results showed that the proposed method, compared to a human driver, can also maintain the lane within reasonable specifications. The experimental validation was performed at vehicle speeds of up to 120 km/h.

Observer-based backstepping control method using reduced lateral dynamics for autonomous lane-keeping system

This paper presents a backstepping control method with an augmented observer for an autonomous lane-keeping system. A novel reduced second-order model is also derived for an autonomous lane-keeping system. The proposed reduced model of lateral vehicle motion has the following advantages: (1) The lateral motion of the vehicle can be controlled with only simple linear second-order dynamics via the backstepping procedure; (2) The state variable of the reduced model includes the look-ahead distance similar to that for a human driver; (3) The system functions with unknown parameters and external disturbances can be lumped in the disturbance. An augmented observer is designed to estimate the full state and lumped disturbance, including the system functions with unknown parameters and external disturbances. A backstepping control is developed for improving the lateral control and compensation of the disturbance. The stability of the closed-loop system is demonstrated using the input-to-state stable property. The lateral control performance of the proposed method is validated via numerical simulations using CarSim and MATLAB/Simulink.

Path following for podded propulsion unmanned surface vehicle: Theory, simulation and experiment

This paper addresses three interrelated problems concerning the path following of a podded propulsion unmanned surface vessel (USV), namely, the modeling of podded propulsion USV, the model parameter identification and the guidance law design. Based on hypotheses and simplification, three degree of freedom (DOF) manipulating mathematical model group (MMG) models of podded propulsion USV are reduced to the response model, and then, a series of field experiments (turning experiment and zig‐zag experiment) is carried out to collect corresponding data. On this basis, the parameters of the model are obtained through the method of system identification. Meanwhile, the simulation data are compared with the actual data to verify the accuracy of the identification results. The conventional line‐of‐sight guidance is modified by adaptive sideslip angle and a time‐varying lookahead distance, where the lookahead distance is adjusted by fuzzy algorithm. Lyapunov function is used to prove that all error signals in the system are uniformly ultimately bounded. Three numerical examples and the real ship field experiment have been described to illustrate the performance and effectiveness of the proposed scheme. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Path Tracking Control of a Differential-Drive Tracked Robot Based on Look-ahead Distance

In this paper, a PI path tracking controller based on look-ahead point information for a differential-drive crawler-type robot was developed. The robot is equipped with Global Navigation Satellite System (GNSS) antennas and a receiver module which are used as navigation sensors to obtain real-time estimates of the position and heading errors of the robot. To control the position of the robot with respect to the target path, a look-ahead point was generated by using Euler Transformation. The look-ahead point lateral errors were then controlled by the designed controller. Forward and backward path tracking tests with different look-ahead distances were conducted to examine the controller performance of the robot and the effect of changing look-ahead distance. Through experiment results, it was noted that the lateral errors mean value was within 0.05 m for forward path tracking and 0.06 m for backward path tracking while the heading errors mean value was within 0.5 degree for forward path tracking and 1 degree for backward path tracking. The proposed algorithms were suitable for the differential-drive robot platform for forward and backward path tracking with a reasonable look-ahead distance.

Adaptive LOS Path Following for a Podded Propulsion Unmanned Surface Vehicle with Uncertainty of Model and Actuator Saturation

This paper addresses three related issues concerning the path following control of a podded propulsion unmanned surface vehicle (USV), namely modeling, guidance and control. The pod is different from the general propeller-rudder propulsion device, and its essence is a vector thruster. Therefore, first, through various assumptions and simplification, the three-degree of freedom (DOFs) planar motion model of the podded propulsion USV is established. Then, the classical line-of-sight (LOS) guidance strategy is improved by adaptive sideslip angle and a time-varying lookahead distance. Based on the guidance system, the corresponding controllers for yaw rate and surge speed are presented, which are combined by backstepping technology, the neural network minimum parameter learning method and the neural shunting model. Specifically, the neural network minimum parameter learning method is proposed to compensate the uncertainty of the model and the immeasurability of external disturbances, and the neural shunting model is employed to cope with the “explosion of complexity” problem of backstepping. Meanwhile, an auxiliary dynamic system is introduced to prevent actuator saturation (input saturation). All error signals of the system are proven to be uniformly ultimately bounded (UUB) by employing Lyapunov stability theory. Finally, two numerical simulations are given to prove the correctness of the proposed scheme.

Teleoperated path following and trajectory tracking of unmanned vehicles using spatial auditory guidance system

The majority of Human–Machine Interfaces (HMIs) designed for the teleoperation of unmanned vehicles only present information visually. Frequent overloading of the operator’s visual channel may result in accidents. To reduce the occurrence of accidents and improve overall operating performance, this paper proposes the extension of the HMI to the hearing modality. The proposed HMI takes the form of a spatial auditory display for complex navigation tasks such as path following (route guidance) or trajectory tracking. The interface incorporates two novel components. The first is the application of a modified “lookahead distance” guidance strategy, as a guidance law for generating a reference. The reference is presented to the operator as a spatial auditory image of the virtual target to be followed. Before being presented to the operator, the reference information is preconditioned through “supernormal” transformations to increase azimuth and distance resolution in regions of interest and thus to improve efficiency and overcome the comparative disadvantages of the hearing channel. A series of experiments show that the proposed guidance strategy provides a comprehensible and effective auditory reference. The enhanced supernormal auditory interface improves performance by reducing the tracking error of both path following and trajectory tracking compared to a non-enhanced interface without the supernormal transformation. Experiment participants report that the novel auditory interface is intuitive and easy to use, providing very good situational awareness. While the auditory interface investigated in this paper is shown to be effective for the teleoperation of unmanned vehicles, it may have other applications such as navigation for the visually impaired.

A study on tracking controller design for unmanned surface vehicles using magnetic coupling thruster

Controlling the unmanned surface vehicles to follow the object or define trajectory have many important applications in the field as military, survey quality environment so this problem has been much research on the world. This report represents the method to control the unmanned surface vehicles which use thruster with coupling follow square or zig-zag trajectories using the Line of Sight (LOS) algorithm combined with the Backstepping Controller. The system consists of three main blocks, Guidance - Control - Ship. Guidance will help to select waypoints to create the trajectory the use the LOS algorithm with lookahead distance to adjust and calculate the desired heading angle ψ. Control with the Backstepping algorithm will calculate the force and moment to apply to the dynamic model of the Ship. The position and heading angle of the vehicles will be feedback to the two Guidance-Control blocks for calculation and updating. The effectiveness of the algorithm will be presented in simulation results with MATLAB / SIMULINK

Backstepping Control Method with Sliding Mode Observer for Autonomous Lane Keeping System

This study derived a novel reduced second-order model for an autonomous lane keeping system. The proposed reduced model of the lateral vehicle motion has the following two advantages: first, one can control the vehicle’s lateral motion with only simple linear second-order dynamics and second, the state variable of the reduced model includes look-ahead distance likewise human driver. The backstepping control for the lateral control and the compensation of the system parameter and uncertainties is developed using the reduced model. Moreover, the reduced model-based sliding mode observer is designed to estimate the lateral velocity. The stability of the closed-loop system is proven using passivity. The lateral control performance of the proposed method is validated via numerical simulations using CarSim and MATLAB/Simulink and compared to the fourth-order lateral motion model-based linear quadratic controller.

A real-time artifact reduction algorithm based on precise threshold during short-separation optical probe insertion in neurosurgery

During neurosurgery, an optical probe has been used to guide the micro-electrode, which is punctured into the globus pallidus (GP) to create a lesion that can relieve the cardinal symptoms. Accurate target localization is the key factor to affect the treatment. However, considering the scattering nature of the tissue, the “look ahead distance (LAD)” of optical probe makes the boundary between the different tissues blurred and difficult to be distinguished, which is defined as artifact. Thus, it is highly desirable to reduce the artifact caused by LAD. In this paper, a real-time algorithm based on precise threshold was proposed to eliminate the artifact. The value of the threshold was determined by the maximum error of the measurement system during the calibration procession automatically. Then, the measured data was processed sequentially only based on the threshold and the former data. Moreover, 100[Formula: see text][Formula: see text]m double-fiber probe and two-layer and multi-layer phantom models were utilized to validate the precision of the algorithm. The error of the algorithm is one puncture step, which was proved in the theory and experiment. It was concluded that the present method could reduce the artifact caused by LAD and make the real boundary sharper and less blurred in real-time. It might be potentially used for the neurosurgery navigation.

A Comparison among Manual and Automatic Calibration Methods in VISSIM in an Expressway (Chihuahua, Mexico)

Traffic microsimulation is an essential tool in urban transportation and road planning. Its calibration is essential to attain representative results validated with real-world conditions. VISSIM (Verkehr in Stadten—SIMulationsmodell) operates with the Wiedemann’s psycho-physical car-following model for freeway travel that considers safety distances (standstill and movement) during simulation. Calibration in this paper was achieved by using two different approaches: a) manual and b) genetic algorithm (with the GEH statistic formula) calibration techniques. Calibration and validation of this model were performed at the Periferico de la Juventud expressway in Chihuahua City, in northern Mexico. The Periferico de la Juventud (PDJ) has a N-S orientation and a length of ca. 20 km, with its northern section being its most congested portion. Its highest vehicle volume occurs at noon, with 3700 vehicles per hour, with 95% being passenger cars and the other 5% heavy goods vehicles. PDJ’s speed limit is 70 km·h-1, but the driver’s behavior has a tendency towards the aggressive performance. A total of 82 standstill and 82 look-ahead distances were obtained from unmanned aerial vehicles (UAV) images, with values ranging from 0.8 to 4.7 m and from 0.2 to 28 m, respectively. VISSIM calibrated parameter values were calculated for this expressway, being slightly above than the VISSIM default ones; and was validated with travel times and look-ahead distances. Results contribute information for the city’s future installment of public transportation systems, and should help decision makers deal with future urban planning.

Haptic Guidance Steering Control Based on Look-ahead Distance during Driving in Curved Section

Haptic Guidance Steering Control Based on Look-ahead Distance during Driving in Curved Section

Back-stepping based anti-disturbance flight controller with preview methodology for autonomous aerial refueling

This paper proposes a novel back-stepping based flight controller for the receiver in Autonomous Aerial Refueling (AAR) by the combination of active disturbance rejection control (ADRC) and preview control methodology. Firstly, the proposed flight control law design is divided into five loops by the back-stepping technique. The 6 DOF model for aircraft is written into several strict-feedback nonlinear forms through tactful transformation, considering that the path dynamics are originally non-affine nonlinear forms and are intractable for controller design. Secondly, the influences of the unknown flow perturbations on a receiver in each loop are viewed as the components of the “total disturbances” which are estimated and compensated by extended state observer (ESO). Thirdly, the preview control methodology is introduced into the position loop design as the system dynamic of the receiver is much slower than drogue. The position loop determines the proper reference path angle by using a fuzzy-logic ADRC controller in which previewing error and current tracking error are both taken into consideration. And a novel adaptive look-ahead distance scheme based on the fuzzy logic control (FLC) is proposed for the selection of the preview point. Finally, extensive simulations and comparisons on the 6 DOF receiver model are carried out to demonstrate the effectiveness of the proposed flight controller.

Geo-Stopping With Deep-Directional-Resistivity Logging-While-Drilling: A New Method for Wellbore Placement With Below-the-Bit Resistivity Mapping

Summary The Wheatstone liquefied-natural-gas (LNG) Project in Western Australia uses subsea big-bore gas wells for producing the Wheatstone and Iago gas accumulations. These wells use a 9⅝-in. production conduit from the top of the gas-pay zone to the ocean floor to maximize their productive capacity. A critical design requirement is that the 9⅝-in. production conduit be set as close as possible to the target zone containing gas-pay intervals (i.e., preferably within 3 m) without actually penetrating into the productive core of a gas interval. In many instances, the top of the target zone and gas pay are one and the same. The wells must also intersect the horizontal top of the target zone at inclinations (inc) of 45–60°. These design requirements impose a significant challenge to the efficient execution of a Wheatstone well. Traditional “ahead-of-the-bit” logging-while-drilling (LWD) solutions are capable of detecting resistivity fluctuations up to 1 m in front of the drill bit. This, however, was considered an insufficient look-ahead distance to prevent premature penetration of a gas reservoir. Alternative solutions, such as pilot holes and biostratigraphic analysis of drilled cuttings, were also considered but found to be too expensive and/or operationally impractical. During a search for a potential solution to this problem, the Wheatstone Project team reviewed a new reservoir mapping-while-drilling technology (Beer et al. 2010; Jenkins et al. 2012; Leveque et al. 2012; Netto et al. 2012; Peppard et al. 2012; Constable et al. 2012; Viandante et al. 2013; Pontarelli et al. 2014; Seydoux et al. 2014; Dupuis and Mendoza-Barrón 2014) that was being field-tested for in-zone steering of horizontal wells and/or landing such wells at shallow angles of incidence relative to formation bedding (i.e., ≤ 13°). The technology, on the basis of deep-directional-resistivity (DDR) measurements, was recognized as a potential solution by the Wheatstone Project team, considering that it showed some promise for being able to predict/infer resistivity changes farther below the bit than previous systems. Deploying the technology at Wheatstone, however, would impose operating conditions for which it was neither designed nor intended (i.e., angles of incidence as high as 30–45°). Ultimately, the technology was successfully tested at Wheatstone and became the Project's default method for landing all big-bore gas wells to the required level of accuracy described above. This paper details (1) the safety and well-design drivers that precipitated the need for using DDR technology, (2) the physics and logic of this LWD system, (3) the new concept for applying the system in nonhorizontal applications, and (4) the observed results from all wells (seven in total) in which the technology was used. To fully evaluate the results, the below-the-bit resistivity and formation depths that were predicted by the DDR system while drilling above the gas-bearing target zone are compared with the actual formation depths and resistivities that were directly measured later when drilling through the target zone. Directly comparing the real-time DDR estimates to actual in-zone measurements, taken in the same strata and geographic locations, has allowed us to clearly determine both the system's geometric limits for detecting resistivity variations below the bit and its ability to accurately resolve the depth and resistivity of formations before penetrating them.

Teleoperated trajectory tracking of remotely operated vehicles using spatial auditory interface

Abstract: The majority of Human-Machine-Interfaces (HMIs) designed for teleoperation of Unmanned Vehicles (UVs) present information only visually. Frequent overloading of operator’s visual channel may cause unwanted mishaps. In order to reduce such mishaps and improve overall operating performance, this paper proposes the extension of the HMI by hearing modality in the form of spatial auditory display for trajectory tracking, the most complex guidance task. The main novelty of the interface is introduction of guidance laws to generate the reference presented to the operator as a spatial auditory image of the virtual target to be followed. Guidance laws for teleoperated trajectory tracking are based on modified lookahead distance strategy, known from path following applications. The paper also analyzes the stability of the kinematic controller based on this new guidance control law. The experiments show that the novel guidance strategy provides comprehensible and effective reference providing excellent trajectory tracking performance.