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Dive into the research topics where Johan Wahlström is active.

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Featured researches published by Johan Wahlström.


IEEE Intelligent Transportation Systems Magazine | 2014

Insurance Telematics: Opportunities and Challenges with the Smartphone Solution

Peter Händel; Isaac Skog; Johan Wahlström; Farid Bonawiede; Richard Welch; Jens Ohlsson; Martin Ohlsson

Smartphone-based insurance telematics or usage based insurance is a disruptive technology which relies on insurance premiums that reflect the risk profile of the driver; measured via smartphones with appropriate installed software. A survey of smartphone-based insurance telematics is presented, including definitions; Figure-of-Merits (FoMs), describing the behavior of the driver and the characteristics of the trip; and risk profiling of the driver based on different sets of FoMs. The data quality provided by the smartphone is characterized in terms of Accuracy, Integrity, Availability, and Continuity of Service. The quality of the smartphone data is further compared with the quality of data from traditional in-car mounted devices for insurance telematics, revealing the obstacles that have to be combated for a successful smartphone-based installation, which are the poor integrity and low availability. Simply speaking, the reliability is lacking considering the smartphone measurements. Integrity enhancement of smartphone data is illustrated by both second-by-second lowlevel signal processing to combat outliers and perform integrity monitoring, and by trip-based map-matching for robustification of the recorded trip data. A plurality of FoMs are described, analyzed and categorized, including events and properties like harsh braking, speeding, and location. The categorization of the FoMs in terms of Observability, Stationarity, Driver influence, and Actuarial relevance are tools for robust risk profiling of the driver and the trip. Proper driver feedback is briefly discussed, and rule-of-thumbs for feedback design are included. The work is supported by experimental validation, statistical analysis, and experiences from a recent insurance telematics pilot run in Sweden.


IEEE Transactions on Intelligent Transportation Systems | 2015

Detection of Dangerous Cornering in GNSS-Data-Driven Insurance Telematics

Johan Wahlström; Isaac Skog; Peter Händel

We propose a framework for the detection of dangerous vehicle cornering events, based on statistics related to the no-sliding and no-rollover conditions. The input variables are estimated using an unscented Kalman filter applied to global navigation satellite system (GNSS) measurements of position, speed, and bearing. The resulting test statistic is evaluated in a field study where three smartphones are used as measurement probes. A general framework for performance evaluation and estimator calibration is presented as depending on a generic loss function. Furthermore, we introduce loss functions designed for applications aiming to either minimize the number of missed detections and false alarms, or to estimate the risk level in each cornering event. Finally, the performance characteristics of the estimator are presented as depending on the detection threshold, as well as on design parameters describing the driving behavior. Since the estimation only uses GNSS measurements, the framework is particularly well suited for smartphone-based insurance telematics applications, aiming to avoid the logistic and monetary costs associated with, e.g., on-board-diagnostics or black-box dependent solutions. The design of the estimation algorithm allows for instant feedback to be given to the driver and, hence, supports the inclusion of real-time value-added services in usage-based insurance programs.


IEEE Transactions on Intelligent Transportation Systems | 2017

Smartphone-Based Vehicle Telematics: A Ten-Year Anniversary

Johan Wahlström; Isaac Skog; Peter Händel

Just as it has irrevocably reshaped social life, the fast growth of smartphone ownership is now beginning to revolutionize the driving experience and change how we think about automotive insurance, vehicle safety systems, and traffic research. This paper summarizes the first ten years of research in smartphone-based vehicle telematics, with a focus on user-friendly implementations and the challenges that arise due to the mobility of the smartphone. Notable academic and industrial projects are reviewed, and system aspects related to sensors, energy consumption, and human–machine interfaces are examined. Moreover, we highlight the differences between traditional and smartphone-based automotive navigation, and survey the state of the art in smartphone-based transportation mode classification, vehicular ad hoc networks, cloud computing, driver classification, and road condition monitoring. Future advances are expected to be driven by improvements in sensor technology, evidence of the societal benefits of current implementations, and the establishment of industry standards for sensor fusion and driver assessment.


international conference on intelligent transportation systems | 2014

Risk Assessment of Vehicle Cornering Events in GNSS Data Driven Insurance Telematics

Johan Wahlström; Isaac Skog; Peter Händel

We propose a framework for the detection of dangerous vehicle cornering events, based on test statistics related to the no-sliding and no-rollover conditions. The input variables are estimated using circle fitting of position measurements (giving the instantaneous radius of the driving trajectory), and a Rauch-Tung-Striebel smoother applied to a state-space model describing the vehicle dynamics. The accuracy of the resulting test statistic is evaluated in a simulation study. In addition, we present the results of a field experiment where three smartphones were used as measurement probes. Since the estimation only uses position and speed data from global navigation satellite system receivers, the framework is particularly well-suited for smartphone-based insurance telematics applications, aiming to avoid the logistic and monetary costs associated with e.g., on-board-diagnostics or black-box dependent solutions. The design of the estimation algorithm allows for instant feedback to be given to the driver, and hence, supports the inclusion of real time value added services in usage-based-insurance programs.


IEEE Transactions on Intelligent Vehicles | 2016

IMU-Based Smartphone-to-Vehicle Positioning

Johan Wahlström; Isaac Skog; Peter Händel; Arye Nehorai

In this paper, we address the problem of using inertial measurements to position a smartphone with respect to a vehicle-fixed accelerometer. Using rigid body kinematics, this is cast as a nonlinear filtering problem. Unlike previous publications, we consider the complete three-dimensional kinematics, and do not approximate the angular acceleration to be zero. The accuracy of an estimator based on the unscented Kalman filter is compared with the Cramer-Rao bound. As is illustrated, the estimates can be expected to be better in the horizontal plane than in the vertical direction of the vehicle frame. Moreover, implementation issues are discussed and the system model is motivated by observability arguments. The efficiency of the method is demonstrated in a field study which shows that the horizontal RMSE is in the order of 0.5 [m]. Last, the proposed estimator is benchmarked against the state-of-the-art in left/right classification. The framework can be expected to find use in both insurance telematics and distracted driving solutions.


IEEE Transactions on Biomedical Engineering | 2017

A Hidden Markov Model for Seismocardiography

Johan Wahlström; Isaac Skog; Peter Händel; Farzad Khosrow-Khavar; Kouhyar Tavakolian; Phyllis K. Stein; Arye Nehorai

We propose a hidden Markov model approach for processing seismocardiograms. The seismocardiogram morphology is learned using the expectation-maximization algorithm, and the state of the heart at a given time instant is estimated by the Viterbi algorithm. From the obtained Viterbi sequence, it is then straightforward to estimate instantaneous heart rate, heart rate variability measures, and cardiac time intervals (the latter requiring a small number of manual annotations). As is shown in the conducted experimental study, the presented algorithm outperforms the state-of-the-art in seismocardiogram-based heart rate and heart rate variability estimation. Moreover, the isovolumic contraction time and the left ventricular ejection time are estimated with mean absolute errors of about 5 [ms] and


IEEE Transactions on Intelligent Vehicles | 2016

Map-Aided Dead-Reckoning Using Only Measurements of Speed

Johan Wahlström; Isaac Skog; João G. P. Rodrigues; Peter Händel; Ana Aguiar

{\text{9 [ms]}}


workshop on physical analytics | 2015

Driving Behavior Analysis for Smartphone-based Insurance Telematics

Johan Wahlström; Isaac Skog; Peter Händel

, respectively. The proposed algorithm can be applied to any set of inertial sensors; does not require access to any additional sensor modalities; does not make any assumptions on the seismocardiogram morphology; and explicitly models sensor noise and beat-to-beat variations (both in amplitude and temporal scaling) in the seismocardiogram morphology. As such, it is well suited for low-cost implementations using off-the-shelf inertial sensors and targeting, e.g., at-home medical services.


international conference on information fusion | 2015

IMU alignment for smartphone-based automotive navigation

Johan Wahlström; Isaac Skog; Peter Händel

We present a particle-based framework for estimating the position of a vehicle using map information and measurements of speed. The filter propagates the particles’ position estimates by means of dead-reckoning, and then updates the particle weights using two measurement functions. The first measurement function is based on the assumption that the lateral force on the vehicle does not exceed critical limits derived from physical constraints. The second is based on the assumption that the driver approaches a target speed derived from the speed limits along the upcoming trajectory. Assuming some prior knowledge of the initial position, performance evaluations of the proposed method indicate that end destinations often can be estimated with an accuracy in the order of


IEEE Transactions on Signal Processing | 2017

The

Johan Wahlström; Isaac Skog; Patricio S. La Rosa; Peter Händel; Arye Nehorai

100\,[\mathrm{m}]

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Isaac Skog

Royal Institute of Technology

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Peter Händel

Royal Institute of Technology

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Arye Nehorai

Washington University in St. Louis

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Patricio S. La Rosa

Washington University in St. Louis

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Farid Bonawiede

Royal Institute of Technology

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Martin Ohlsson

Royal Institute of Technology

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