| 1. |
- Antoniou, Constantinos, et al.
(author)
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Non–linear Kalman Filtering Algorithms for On–line Calibration of Dynamic Traffic Assignment Models
- 2007
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In: IEEE transactions on intelligent transportation systems (Print). - 1524-9050 .- 1558-0016. ; 8:4, s. 661-670
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Journal article (peer-reviewed)abstract
- An online calibration approach that jointly estimates demand and supply parameters of dynamic traffic assignment (DTA) systems is presented and empirically validated through an extensive application. The problem can be formulated as a nonlinear state-space model. Because of its nonlinear nature, the resulting model cannot be solved by the Kalman filter, and therefore, nonlinear extensions need to be considered. The following three extensions to the Kalman filtering algorithm are presented: 1) the extended Kalman filter (EKF); 2) the limiting EKF (LimEKF); and 3) the unscented Kalman filter. The solution algorithms are applied to the on-line calibration of the state-of-the-art DynaMIT DTA model, and their use is demonstrated in a freeway network in Southampton, U.K. The LimEKF shows accuracy that is comparable to that of the best algorithm but with vastly superior computational performance. The robustness of the approach to varying weather conditions is demonstrated, and practical aspects are discussed.
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| 2. |
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| 3. |
- Eidehall, Andreas, et al.
(author)
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Statistical Threat Assessment for General Road Scenes using Monte Carlo Sampling
- 2008
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In: IEEE transactions on intelligent transportation systems (Print). - 1524-9050 .- 1558-0016. ; 9:1, s. 137-147
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Journal article (peer-reviewed)abstract
- This paper presents a threat-assessment algorithm for general road scenes. A road scene consists of a number of objects that are known, and the threat level of the scene is based on their current positions and velocities. The future driver inputs of the surrounding objects are unknown and are modeled as random variables. In order to capture realistic driver behavior, a dynamic driver model is implemented as a probabilistic prior, which computes the likelihood of a potential maneuver. A distribution of possible future scenarios can then be approximated using a Monte Carlo sampling. Based on this distribution, different threat measures can be computed, e.g., probability of collision or time to collision. Since the algorithm is based on the Monte Carlo sampling, it is computationally demanding, and several techniques are presented to increase performance without increasing computational load. The algorithm is intended both for online safety applications in a vehicle and for offline data analysis.
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| 4. |
- Eidehall, Andreas, et al.
(author)
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Toward Autonomous Collision Avoidance by Steering
- 2007
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In: IEEE transactions on intelligent transportation systems (Print). - Linköping : Linköping University Electronic Press. - 1524-9050 .- 1558-0016. ; 8:1, s. 84-94
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Journal article (peer-reviewed)abstract
- This paper presents a new automotive safety function called Emergency Lane Assist (ELA). ELA combines conventional lane guidance systems with a threat assessment module that tries to activate the lane guidance interventions according to the actual risk level of lane departure. The goal is to only prevent dangerous lane departure maneuvers. The ELA safety function is based on a statistical method that evaluates a list of safety concepts and tries to maximize the impact on accident statistics while minimizing development and hardware component costs. ELA. runs in a demonstrator and successfully intervenes during lane changes that are likely to result in a collision and is also able to take control of the vehicle and return it to a safe position in the original lane. It has also been tested on 2000 km of roads in traffic without giving any false interventions.
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| 5. |
- Forzati, Marco, et al.
(author)
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Asynchronous Phase Modulation for the Suppression of IFWM
- 2007
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In: IEEE transactions on intelligent transportation systems (Print). - 1524-9050 .- 1558-0016. ; 25, s. 2969-75
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Journal article (peer-reviewed)abstract
- Intrachannel four-wave mixing (IFWM) represents main source of impairments in fiber transmission at 40 Gb/s. A number of phase modulation techniques have been proposed to suppress the IFWM. In this paper, we study a cost-effective way of increasing the nonlinear tolerance of a 40-Gb/s wavelength division multiplexing transmission system by asynchronous phase modulation (APM). This can be achieved with one phase modulator placed after the wavelength multiplexer so that cost is shared by all channels. We show, by means of numerical simulations and laboratory experiments, that APM greatly improves the performance of ON-OFF-keying transmission.
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| 6. |
- Forzati, Marco, et al.
(author)
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Performance Analysis of Single-MZM APRZ Transmitters
- 2006
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In: IEEE transactions on intelligent transportation systems (Print). - 1524-9050 .- 1558-0016. ; 24, s. 2006-14
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Journal article (peer-reviewed)abstract
- In this paper, an efficient single Mach-Zender modulator (MZM) implementation of alternate-phase return to zero (APRZ), which combines carrier-suppressed return to zero (CSRZ)'s ease of implementation with APRZ's nonlinear tolerance, is analyzed. In particular, the first numerical study of 67%-duty-cycle single-MZM APRZ over a 40-Gb/s 5 × 100-km link, in terms of nonlinear, dispersion, and filtering tolerance, comparing it with 33% RZ, 33% APRZ, and standard 67% CSRZ, is presented. The results show that APRZ with phase shift close to π/2 is the optimum choice, independent of specific transmitter implementation. A new mechanism is also discovered, based on the interference of ghost pulses with the original pulse train, which improves the nonlinear tolerance of CSRZ in a 40-Gb/s transmission
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| 7. |
- Johannesson, Lars, 1979, et al.
(author)
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Assessing the Potential of Predictive Control for Hybrid Vehicle Powertrains using Stochastic Dynamic Programming
- 2007
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In: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050 .- 1558-0016. ; 8:1, s. 71-83
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Journal article (peer-reviewed)abstract
- The potential for reduced fuel consumption of Hybrid Electric Vehicles by the use of predictive powertrain control was assessed on measured drive data from an urban route with varying topography. The assessment was done by evaluating the fuel consumption using three optimal controllers, each with a different level of information access to the driven route. The lowest information case represents that the vehicle knows that it is being driven in a certain environment, e.g. city driving, and that the controller has been optimized for that type of environment. The second highest information level represents a vehicle equipped with a GPS combined with a traffic flow information system. In the highest information level the future power demand is completely known to the control system, hence the corresponding optimal controller results in the minimal attainable fuel consumption. The study showed that good performance, 1-3% from the minimal attainable fuel consumption, can be achieved with the lowest information case, with a time invariant controller that is optimized to the environment. The second highest information level results in less than 0.2% higher consumption than the minimal attainable on the studied route. This means that it is possible to design a predictive controller based on information supplied by the vehicle navigation system and traffic flow information systems that can come very close to the minimal attainable fuel consumption. A novel algorithm that uses information supplied by the vehicle navigation system was presented. The proposed algorithm results in a consumption only 0.3% from the minimal attainable consumption on the studied route.
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| 8. |
- Ma, Xiaoliang, et al.
(author)
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Behavior measurement, analysis and regime classification in car following
- 2007
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In: IEEE transactions on intelligent transportation systems (Print). - : IEEE Press. - 1524-9050 .- 1558-0016. ; 8:1, s. 144-156
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Journal article (peer-reviewed)abstract
- This paper first reports a data acquisition method that the authors used in a project on modeling driver behavior for microscopic traffic simulations. An advanced instrumented vehicle was employed to collect driver-behavior data, mainly car-following and lane-changing patterns, on Swedish roads. To eliminate the measurement noise in acquired car-following patterns, the Kalman smoothing algorithm was applied to the state-space model of the physical states (acceleration, speed, and position) of both instrumented and tracked vehicles. The denoised driving patterns were used in the analysis of driver properties in the car-following stage. For further modeling of car-following behavior, we developed and implemented a consolidated fuzzy clustering algorithm to classify different car-following regimes from the preprocessed data. The algorithm considers time continuity of collected driver-behavior patterns and can be more reliably applied in the classification of continuous car-following regimes when the classical fuzzy C-means algorithm gives unclear results.
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| 9. |
- Skog, Isaac, et al.
(author)
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In-Car Positioning and Navigation Technologies : a survey
- 2009
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In: IEEE transactions on intelligent transportation systems (Print). - 1524-9050 .- 1558-0016. ; 10:1, s. 4-21
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Research review (peer-reviewed)abstract
- In-car positioning and navigation has been a killer application for Global Positioning System (GPS) receivers, and a variety of electronics for consumers and professionals have been launched on a large scale. Positioning technologies based on stand-alone GPS receivers are vulnerable and, thus, have to be supported by additional information sources to obtain the desired accuracy, integrity, availability, and continuity of service. A survey of the information sources and information fusion technologies used in current in-car navigation systems is presented. The pros and cons of the four commonly used information sources, namely, 1) receivers for radio-based positioning using satellites, 2) vehicle motion sensors, 3) vehicle models, and 4) digital map information, are described. Common filters to combine the information from the various sources are discussed. The expansion of the number of satellites and the number of satellite systems, with their usage of available radio spectrum, is an enabler for further development, in combination with the rapid development of microelectromechanical inertial sensors and refined digital maps.
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| 10. |
- Urazghildiiev, Ildar, et al.
(author)
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High-Resolution Estimation of Ranges Using Multiple-Frequency CW Radar
- 2007
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In: IEEE transactions on intelligent transportation systems (Print). - 1524-9050 .- 1558-0016. ; 8:2, s. 332-339
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Journal article (peer-reviewed)abstract
- The problem of ranging multiple vehicles traveling at similar speeds using multiple-frequency continuous-wave (CW) radar is considered. A new method based on the compensation of vehicle movement and MUSIC-based time delay estimator is presented. The method is tested using a commercially available multiple-frequency CW radar sensor in real traffic situations. Test results show that the proposed method makes it possible to estimate the positions of two vehicles moving at similar speeds. Test results also demonstrate that under a given bandwidth, the multiple-frequency CW radar can provide about ten times higher resolution as compared with the coherent spread spectrum radar.
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