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  • 3801.
    Toss, Tomas
    et al.
    Saab AB, Linköping/Göteborg, Sweden.
    Dammert, Patrik
    Saab AB, Linköping/Göteborg, Sweden.
    Sjanic, Zoran
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten. Saab AB, Linköping/Göteborg, Sweden.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Navigation with SAR and 3D-Map Aiding2015Inngår i: Proceedings of the 18th International Conference on Information Fusion (Fusion), IEEE , 2015, s. 1505-1510Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a method for matching spotlight Synthetic Aperture Radar (SAR) images with a georeferenced 3D-map as means for navigational aid. A hypothesis of the flying platform's absolute position, velocity and direction - which later can be used to correct the inertial navigation system - is attained by image matching and optimization. A projective model with 6 DoF is used to create a simulated SAR image from a 3D map. The parameters of the projective model represents the most important of the platform's navigation state, and these are adjusted by Chamfer matching the captured SAR image to simulated ones. The performance is demonstrated on real spotlight SAR images and 3D-map, and the error is shown to be only a few pixels in average, which in our case is about 3 meters.

  • 3802.
    Toth, Roland
    et al.
    Delft University of Technology, The Netherlands.
    Lyzell, Christian
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Enqvist, Martin
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Heuberger, Peter S.C.
    Delft University of Technology, The Netherlands.
    Van den Hof, Paul M. J.
    Delft University of Technology, The Netherlands.
    Order and Structural Dependence Selection of LPV-ARX Models using a Nonnegative Garrote Approach2010Rapport (Annet vitenskapelig)
    Abstract [en]

    In order to accurately identify Linear Parameter-Varying (LPV) systems, order selection of LPV linear regression models has prime importance. Existing identification approaches in this context suffer from the drawback that a set of functional dependencies needs to be chosen a priori for the parametrization of the model coefficients. However in a black-box setting, it has not been possible so far to decide which functions from a given set are required for the parametrization and which are not. To provide a practical solution, a nonnegative garrote approach is applied. It is shown that using only a measured data record of the plant, both the order selection and the selection of structural coefficient dependence can be solved by the proposed method.

    Fulltekst (pdf)
    FULLTEXT01
  • 3803.
    Toverland, Anders
    Linköpings universitet, Institutionen för systemteknik.
    Icke modellbaserad ekoföljning för radarnivåmätning2006Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Denna rapport behandlar en fullständig metod för att följa, associera och klassificera ekospår. Vid radarnivåmätning ska ekon som härstammar ifrån samma fysikaliska objekt följas över tiden och klassificeras. Dagens radarnivågivare löser problemet genom konfiguration. Tankens geometri samt vilka störande objekt som finns anges vid installation.

    Den framtagna metoden har delats upp i tre delmoment. Först binds individuella inmätta ekon samman till linjesegment. Dessa segment associeras samman till ekospår varefter dessa klassas fysikaliskt. Metoden kräver betydligt mindre konfiguration än den lösning som används för tillfället.

    Fulltekst (pdf)
    FULLTEXT01
  • 3804.
    Toverland, Johan
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Thermal Modelling of Voicecoils in Microspeakers2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Microspeakers can overheat and break if not monitored and regulated. This monitoringis usually done by adding a pilot tone that introduces energy to the signal.A problem with this approach is the slow update rate of the temperature estimate.This in combination with a fast temperature rise could result in an audible regulationof the input. By simulating the voice coil temperature these problems couldbe mitigated. In this thesis, two existing grey box models and one novel black boxmodel are estimated for different speakers and evaluated using different signals.The results are promising and indicate that all models can estimate the voice coiltemperature with a mean error below one degree. The tests show that a correctinitialization of the model is crucial. Therefore the suggestion to Cirrus Logic,who hosted this thesis project, is to combine a feedforward model with eithertemperature sensor data from the mobile device or a pilot tone.

    Fulltekst (pdf)
    fulltext
  • 3805.
    Tronarp, Otto
    Linköpings universitet, Institutionen för systemteknik.
    Quality of Service in Ad Hoc Networks by Priority Queuing2003Independent thesis Basic level (professional degree)Oppgave
    Abstract [en]

    The increasing usage of information technology in military affairs raises the need for robust high capacity radio networks. The network will be used to provide several different types of services, for example group calls and situation awareness services. All services have specific demands on packet delays and packet losses in order to be fully functional, and therefore there is a need for a Quality of Service (QoS) mechanism in the network.

    In this master thesis we examine the possibility to provide a QoS mechanism in Ad Hoc networks by using priority queues. The study includes two different queuing schemes, namely fixed priority queuing and weighted fair queuing. The performance of the two queuing schemes are evaluated and compared with respect to the ability to provide differentiation in network delay, i.e., provide high priority traffic with lower delays than low priority traffic. The study is mainly done by simulations, but for fixed priority queuing we also derive a analytical approximation of the network delay.

    Our simulations show that fixed priority queuing provides a sharp delay differentiation between service classes, while weighted fair queuing gives the ability to control the delay differentiation. One of those queuing schemes alone might not be the best solution for providing QoS, instead we suggest that a combination of them is used.

    Fulltekst (pdf)
    FULLTEXT01
  • 3806.
    Trulsson, Eva
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Adaptive Control based on Explicit Criterion Minimization1983Rapport (Annet vitenskapelig)
    Abstract [en]

    A common approach to regulator design is to define an objective function, which is minimized with respect to adjustable regulator parameters. Here we discuss how such objective functions can be minimized on-line, thus providing adaptive control. Such an approach to adaptive control has its roots in early contributions to learning systems, and it is here further developed and discussed in the light of the recent development of the field. A general algorithm is given and special attention is paid to minimization of quadratic criteria. A key problem is to obtain information about the system dynamics in order to compute the derivatives of the criterion with respect to the regulator parameters. It is shown that the self-tuning regulator is obtained as a special case, corresponding to a particular quadratic criterion and a particular way of estimating the system dynamics. Explicit ways using instrumental variables techniques based on extra injected noise are also discussed. A specific feature of the algorithm is that it does not utilize specific knowledge about how to calculate the optimal regulator. The algorithm is the same for minimum phase as well as for non-minimum phase systems.

  • 3807.
    Trulsson, Eva
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Adaptive Control based on Explicit Criterion Minimization1983Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    A common approach to regulator design is to define an objective function, which is minimized with respect to adjustable regulator parameters. Here we discuss how such objective functions can be minimized online, thus providingadaptive eon tro I. Such an approach has its roots in early contributions to learning systems and it is here further developed and discussed in the light of the recent development in the field.

    A general algorithm is given and it is then specialized to some concrete examples. One problem when to use this algorithm is that the convergence properties are tied to successful identification of the system dynamics. Therefore an Instrumental Variable identification method based on extra injected noise is analysed and convergence is proved under a boundedness assumption.

    Special attention is paid to the minimization of quadratic criteria. It is shown that if the regulator is flexible enough the minimum of such a criterion is unique. It is also shown that the self tuning regulator is obtained as a special case of the algorithm, corresponding toa particular quadratic criterion anda particular way of estimating the system dynamics.

    One specific feature of the algorithm is that it does not utilize specific knowledge about how to calculate the optimal regulator. The algorithm is thus the same for minimum phase as well as for non minimum phase systems.

  • 3808.
    Trulsson, Eva
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Consistency of an Instrumental Variable Identification Method under Adaptive Feedback1985Inngår i: Proceedings of the 7th IFAC Symposium on Identification and System Parameter Estimation, Pergamon Press, 1985, s. 1335-1340Konferansepaper (Fagfellevurdert)
  • 3809.
    Trulsson, Eva
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Explicit Minimization Methods for Tuning of Nonlinear Regulators1984Inngår i: Proceedings of the 9th IFAC World Congress, Pergamon , 1984, s. 219-223Konferansepaper (Fagfellevurdert)
  • 3810.
    Trulsson, Eva
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Explicit Minimization Methods for Tuning of Nonlinear Regulators1983Rapport (Annet vitenskapelig)
  • 3811.
    Trulsson, Eva
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On Adaptive Control with Prescribed Robustness Properties1985Inngår i: Proceedings of the 1985 American Control Conference, 1985, s. 403-404Konferansepaper (Fagfellevurdert)
  • 3812.
    Trulsson, Eva
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On Adaptive Control with Prescribed Robustness Properties1985Rapport (Annet vitenskapelig)
  • 3813.
    Trulsson, Eva
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Stability in Adaptive Control by Persistently Exciting Regulators1985Rapport (Annet vitenskapelig)
    Abstract [en]

    The stability of adaptive regulators, based on least-squares parameter estimation under arbitrary, bounded disturbances, is considered. Using an idea by Barabanov to obtain persistence of excitation a fairly simple and general stability result is obtained.

  • 3814.
    Trulsson, Eva
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Uniqueness of Local Minima for Linear Quadratic Control Design1985Inngår i: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 5, nr 5, s. 295-302Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The problem of minimizing a weighted sum of the input and output variances from a linear scalar system is considered. This is viewed as an optimization problem with the parameters of the regulator as unknowns and it is proved that if the regulator is flexible enough, then every local minimum to this problem is a global optimum. This result is useful if a gradient method is used to find the optimal regulator.

  • 3815.
    Trulsson, Eva
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Adaptive Control based on Explicit Criterion Minimization1985Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 21, nr 4, s. 385-399Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A common approach to regulator design is to define an objective function, which is minimized with respect to adjustable regulator parameters. Here we discuss how such objective functions can be minimized on-line, thus providing adaptive control. Such an approach to adaptive control has its roots in early contributions to learning systems, and it is here further developed and discussed in the light of the recent development of the field. A general algorithm is given and special attention is paid to minimization of quadratic criteria. A key problem is to obtain information about the system dynamics in order to compute the derivatives of the criterion with respect to the regulator parameters. It is shown that the self-tuning regulator is obtained as a special case, corresponding to a particular quadratic criterion and a particular way of estimating the system dynamics. Explicit ways using instrumental variables techniques based on extra injected noise are also discussed. A specific feature of the algorithm is that it does not utilize specific knowledge about how to calculate the optimal regulator. The algorithm is the same for minimum phase as well as for non-minimum phase systems.

  • 3816.
    Trulsson, Eva
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Direct Minimization Methods for Adaptive Control of Non-Minimum Phase System1981Rapport (Annet vitenskapelig)
  • 3817.
    Trulsson, Eva
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Direct Minimization Methods for Adaptive Control of Non-Minimum Phase System1982Rapport (Annet vitenskapelig)
  • 3818.
    Trulsson, Eva
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On Self-Robustification of Adaptive Control Performance Criteria1986Rapport (Annet vitenskapelig)
    Abstract [en]

    Minimization of control performance criteria can be realized by adaptive control in several different ways. The self-tuning regulator solves the minimization problem analytically based on the current model. An explicit minimization method adjusts directly the regulator parameters to minimize the criterion. Based on observed behaviour of these two approaches when applied to a laboratory process we discuss their respective robustness properties in coping with nonideal conditions.

  • 3819.
    Trulsson, Eva
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On Self-Robustification of Adaptive Control Performance Criteria1987Rapport (Annet vitenskapelig)
  • 3820.
    Trulsson, Eva
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On Self-Robustification of Adaptive Control Performance Criteria1985Inngår i: Proceedings of the 7th IFAC Symposium on Identification and System Parameter Estimation, Pergamon Press, 1985, s. 1021-1024Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Minimization of control performance criteria can be realized by adaptive control in several different ways. The self-tuning regulator solves the minimization problem analytically based on the current model. An explicit minimization method adjusts directly the regulator parameters to minimize the criterion. Based on observed behaviour of these two approaches when applied to a laboratory process we discuss their respective robustness properties in coping with nonideal conditions.

  • 3821.
    Trulsson, Eva
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Stability in Adaptive Control by Persistently Exciting Regulators1985Rapport (Annet vitenskapelig)
    Abstract [en]

    The stability of adaptive regulators, based on least-squares parameter estimation under arbitrary, bounded disturbances, is considered. Using an idea by Barabanov to obtain persistence of excitation a fairly simple and general stability result is obtained.

  • 3822.
    Trulsson, Eva
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Stability in Adaptive Control by Persistently Exciting Regulators1985Inngår i: Proceedings of the 24th IEEE Conference on Decision and Control, 1985, s. 484-491Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The stability of adaptive regulators, based on least-squares parameter estimation under arbitrary, bounded disturbances, is considered. Using an idea by Barabanov to obtain persistence of excitation a fairly simple and general stability result is obtained.

  • 3823.
    Tsypkin, Ya Z.
    et al.
    University of Newcastle, Australia.
    Isaksson, Alf
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Modified Nyquist Criteria for Stability of Multivariable Systems1992Rapport (Annet vitenskapelig)
  • 3824.
    Tsypkin, Yakov Z.
    et al.
    University of Newcastle, Australia.
    Hill, David J.
    University of Newcastle, Australia.
    Isaksson, Alf
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Frequency-Domain Robust Instability Criterion for Time-Varying and Non-Linear Systems1992Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper presents an instability version of an earlier result on robust stability analysis using a modified Nyquist plot. The result is shown to be useful for presenting robust stability and instability margins for feedback systems.

  • 3825.
    Tudoret, Stéphane
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Signal-Simulink: Hybrid System Co-Simulation1999Rapport (Annet vitenskapelig)
    Abstract [en]

    This report presents an approach to simulating hybrid systems. We show how a discrete controller that controls a continuous environment can be co-simulated with the environment (plant) using C-code generated automatically from mathematical models. This approach uses SIGNAL with SIMULINK to model complex hybrid systems. The choices are motivated by the fact that SIGNAL is a powerful tool for modelling complex discrete behaviours and SIMULINK is well-suited to deal with continuous dynamics. We present various alternatives for implementing the communication between the plant and the controller, and how the MATLAB code generation mechanism in Real-time Workshop can be used for this purpose. Finally, we present interesting scenarios in the co-simulation of a discrete controller with its environment: a non-trivial siphon pump proposed by the Swedish engineer Christofer Polhem in 1697.

    Fulltekst (pdf)
    fulltext
  • 3826.
    Tugfe Demir, Özlem Tugfe
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten. KTH Royal Inst Technol, Sweden.
    The Bussgang Decomposition of Nonlinear Systems: Basic Theory and MIMO Extensions [Lecture Notes]2021Inngår i: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 38, nr 1, s. 131-136Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many of the systems in various signal processing applications are nonlinear due to, for example, hardware impairments, such as nonlinear amplifiers and finite-resolution quantization. The Bussgang decomposition is a popular tool used when analyzing the performance of systems that involve such nonlinear components. In a nutshell, the decomposition provides an exact probabilistic relationship between the output and the input of a nonlinearity: the output is equal to a scaled version of the input plus uncorrelated distortion. The decomposition can be used to compute either exact performance results or lower bounds, where the uncorrelated distortion is treated as independent noise. This lecture note explains the basic theory, provides key examples, extends the theory to complex-valued vector signals, and clarifies some potential misconceptions.

  • 3827.
    Tybrandt, Ola
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Distribution of Cooling to Avionics2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In modern aircraft, one of the most difficult issues has been how to provide avionics with adequate cooling. Future versions of the fighter aircraft JAS 39 Gripen is equipped with new applications that have increased heat loads. In previous versions of the JAS 39 Gripen avionics was cooled by zero degree air and fuel, but in the next version a liquid loop will be installed to cool the new radar.The fluid in the liquid loop is cooled to proper temperature by pressurized bleed air from the engine which is cooled by ram air. The air to cool the avionics is produced the same way and this is a very expensive process for the airplane which lowers its performance. It is important to minimize the production of cooling air and therefore three new adjustable valves that provide various components of cooling air are installed in the next version of the JAS 39 Gripen.

    The cooled and pressure controlled air from the engine is distributed between different avionic shelves, each containing a set of components. Depending on the type of tasks performed and current flight mode of the aircraft the requirement of functions which should be active varies and therefore also the cooling demand to avionics. The first part of this thesis studies the overall priority of how the engine bleed shall be used. This part of the thesis results in a decision basis for the distribution of cooling air to be regulated in the absence of full cooling capacity.

    The amount of cooling which must be distributed to the radar is proportional to its developed power which varies widely depending on the radar’s operational mode. Since the pump which determines the liquid flow velocity operates at a constant speed is the regulation of cooling to the radar is controlled by varying the bleed air flow into the heat exchanger which cools the fluid and thus the temperature of the fluid has when it reaches the radar. This part of the thesis creates a control algorithm for controlling the airflow into the heat exchanger. The regulation keeps the fluid inlet temperature to the radar within the range of +25 ± 5 ˚ C and the gradient of the temperature less than 0.5° C per second.

    The PI-controller with the feed-forward filter succeeded in controlling the temperature of the liquid as it reached the radar within +25 ± 1° C, the temperature gradient requirement, 0.5° C per second, was also passed in all flight cases which were used to evaluate the controller. The PI-controller with feed-forward has a low convergence time and no static error. It also performs well when the measurement signals contain a lot of noise because of the controllers integrated low pass filter.

     

    The three new adjustable valves saves 12 to 97 g/s of cooling air for the different valve positions studied in this thesis, this corresponds to 9 - 70% of the total amount of controllable air to the avionics. Since the production of cooling air is a costly process for the aircraft, the use of all 3 valves is recommended.

    Fulltekst (pdf)
    fulltext
  • 3828.
    Tydén, Amanda
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Olsson, Sara
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Edge Machine Learning for Animal Detection, Classification, and Tracking2020Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A research field currently advancing is the use of machine learning on camera trap data, yet few explore deep learning for camera traps to be run in real-time. A camera trap has the purpose to capture images of bypassing animals and is traditionally based only on motion detection. This work integrates machine learning on the edge device to also perform object detection. Related research is brought up and model tests are performed with a focus on the trade-off regarding inference speed and model accuracy. Transfer learning is used to utilize pre-trained models and thus reduce training time and the amount of training data. Four models with slightly different architecture are compared to evaluate which model performs best for the use case. The models tested are SSD MobileNet V2, SSD Inception V2, and SSDLite MobileNet V2, SSD MobileNet V2 quantized. Since the client-side usage of the model, the SSD MobileNet V2 was finally selected due to a satisfying trade-off between inference speed and accuracy. Even though it is less accurate in its detections, its ability to detect more images per second makes it outperform the more accurate Inception network in object tracking.

    A contribution of this work is a light-weight tracking solution using tubelet proposal. This work further discusses the open set recognition problem, where just a few object classes are of interest while many others are present. The subject of open set recognition influences data collection and evaluation tests, it is however left for further work to research how to integrate support for open set recognition in object detection models. The proposed system handles detection, classification, and tracking of animals in the African savannah, and has potential for real usage as it produces meaningful events

    Fulltekst (pdf)
    Edge Machine Learning for Animal Detection, Classification, and Tracking
  • 3829.
    Töpel, Johanna
    Linköpings universitet, Institutionen för systemteknik.
    Initial Analysis and Visualization of Waveform Laser Scanner Data2005Independent thesis Basic level (professional degree)Oppgave
    Abstract [en]

    Conventional airborne laser scanner systems output the three-dimensional coordinates of the surface location hit by the laser pulse. Data storage capacity and processing speeds available today has made it possible to digitally sample and store the entire reflected waveform, instead of only extracting the coordinates. Research has shown that return waveforms can give even more detailed insights into the vertical structure of surface objects, surface slope, roughness and reflectivity than the conventional systems. One of the most important advantages with registering the waveforms is that it gives the user the possibility to himself define the way range is calculated in post-processing.

    In this thesis different techniques have been tested to visualize a waveform data set in order to get a better understanding of the waveforms and how they can be used to improve methods for classification of ground objects.

    A pulse detection algorithm, using the EM algorithm, has been implemented and tested. The algorithm output position and width of the echo pulses. One of the results of this thesis is that echo pulses reflected by vegetation tend to be wider than those reflected by for example a road. Another result is that up till five echo pulses can be detected compared to two echo pulses that the conventional system detects.

    Fulltekst (pdf)
    FULLTEXT01
  • 3830.
    Törnquist, Martin
    Linköpings universitet, Institutionen för systemteknik.
    Investigation of rotational velocity sensors2008Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    To improve the speed measurement of construction equipment, different sensor technologies have been investigated. Many of these sensor technologies are very interesting but to keep the extent of the thesis only two was chosen for testing, magnetic absolute angle sensors using Hall and GMR technology, to investigate if those are a valid replacement for the current measurement system that is using a passive sensor. Tests show that these sensors are capable of speed measurement, but because of noisy angle estimates they need filtering for good speed computation. This filtering introduces a large time delay that is of significance for the quality of the estimate. A Kalman filter has been implemented in an attempt to lower the time delays but since only a very simple model has been used it does not give any improvements over ordinary low pass filtering. For these sensors the mounting tolerance is of great interest. For best performance the offset between the sensor and magnet centres need to be kept small for both sensors. This is due to a non-linearity effect this causes. The distance between the sensors and the magnet is not critical for linearity issues, but only for the quality of the signal, where it might drop out when the distance is too large. This is where the sensor using GMR technology stands out. Compared to the Hall technology sensor, the GMR sensor can handle distances that are more than 10 times larger. The conclusion is that these sensors can be a valid replacement of the current measurement system. They will introduce more functionality with the capability of detecting rotational direction and zero velocity. In an application with more than one sensor they can also be used for more purposes, like detecting slip in clutches etc. Depending on the application, the time delays may not be critical, else more work need to be done to improve the estimate, e.g. with a more advanced model for the Kalman filter.

     

    Fulltekst (pdf)
    FULLTEXT01
  • 3831.
    Törnqvist, David
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Initial State Estimation for Fault Detection over Sliding Windows2006Inngår i: Proceedings of Reglermöte 2006, 2006Konferansepaper (Annet vitenskapelig)
  • 3832. Bestill onlineKjøp publikasjonen >>
    Törnqvist, David
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Statistical Fault Detection with Applications to IMU Disturbances2006Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis deals with the problem of detecting faults in an environment where the measurements are affected by additive noise. To do this, a residual sensitive to faults is derived and statistical methods are used to distinguish faults from noise. Standard methods for fault detection compare a batch of data with a model of the system using the generalized likelihood ratio. Careful treatment of the initial state of the model is quite important, in particular for short batch sizes. One method to handle this is the parity-space method which solves the problem by removing the influence of the initial state using a projection.

    In this thesis, the case where prior knowledge about the initial state is available is treated. This can be obtained for example from a Kalman filter. Combining the prior estimate with a minimum variance estimate from the data batch results in a smoothed estimate. The influence of the estimated initial state is then removed. It is also shown that removing the influence of the initial state by an estimate from the data batch will result in the parity-space method. To model slowly changing faults, an efficient parameterization using Chebyshev polynomials is given.

    The methods described above have been applied to an Inertial Measurement Unit, IMU. The IMU usually consists of accelerometers and gyroscopes, but has in this work been extended with a magnetometer. Traditionally, the IMU has been used to estimate position and orientation of airplanes, missiles etc. Recently, the size and cost has decreased making it possible to use IMU:s for applications such as augmented reality and body motion analysis. Since a magnetometer is very sensitive to disturbances from metal, such disturbances have to be detected. Detection of the disturbances makes compensation possible. Another topic covered is the fundamental question of observability for fault inputs. Given a fixed or linearly growing fault, conditions for observability are given.

    The measurements from the IMU show that the noise distribution of the sensors can be well approximated with white Gaussian noise. This gives good correspondence between practical and theoretical results when the sensor is kept at rest. The disturbances for the IMU can be approximated using smooth functions with respect to time. Low rank parameterizations can therefore be used to describe the disturbances. The results show that the use of smoothing to obtain the initial state estimate and parameterization of the disturbances improves the detection performance drastically.

    Fulltekst (pdf)
    FULLTEXT01
  • 3833.
    Törnqvist, David
    Linköpings universitet, Institutionen för systemteknik.
    Transmission Timing in WCDMA terminals2003Independent thesis Basic level (professional degree)Oppgave
    Abstract [en]

    Power control is one of the technologies used to utilize the radio resources as efficient as possible in WCDMA. The transmission power is adjusted to transmit with the lowest power level possible while the required received signal quality is maintained. Since there are large variation in channel quality over time, the power has to be adjusted to compensate for these variations. During moments of bad channel conditions a high transmission power has to be used which will to a greater extent interfere with other users in the system.

    To solve this problem a concept called transmission timing was proposed. The basic idea is that the transmitter avoids data transmission during the short periods of bad channel conditions caused by fast fading. Higher bit rates can be used to compensate for this when the channel conditions are good.

    In this thesis the performance of transmission timing applied to uplink data transmissions is evaluated. This is accomplished through a theoretical analysis as well as simulations of a cellular system using transmission timing. Lowered transmission power is achieved and thus lowered interference is induced. Simulations showed that the transmission power can be lowered by up to 1.6 dB compared to ordinary continuous transmission with equal average data rate. These results are however strongly dependent on the used radio environment. It is also showed that transmission timing provides increased system stability in case of rapid changes in the load situation.

    Fulltekst (pdf)
    FULLTEXT01
  • 3834.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Geijer Lundin, Erik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Transmission Timing - A Control Approach to Distributed Uplink Scheduling in WCDMA2004Inngår i: Proceedings of the 2004 American Control Conference, 2004, s. 1667-1672 vol.2Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Centralized control and coordination of the connections in a wireless network is not possible in practice. To keep the delay from measurement instants to actuating the decisions, distributed control is required. This paper focuses on the uplink (from mobiles to base stations) and discusses distributing the decision of when and when not to transmit data (distributed scheduling) to the mobiles. The scheme, uplink transmission timing, utilizes mobile transmitter power control feedback from the base station receiver to determine whether the channel is favorable or not compared to the average channel condition. Thereby, the battery consumption and disturbing power to other connections are reduced. The algorithm can be described as a feedback control system. Some transient behaviors are analyzed using systems theory, and supported by wireless network simulations of a system with a WCDMA (Wideband Code Division Multiple Access) radio interface as in most 3G systems.

  • 3835.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Geijer Lundin, Erik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Transmission Timing - A Control Approach to Distributed Uplink Scheduling in WCDMA2004Rapport (Annet vitenskapelig)
    Abstract [en]

    Centralized control and coordination of the connections in a wireless network is not possible in practice. To keep the delay from measure-ment instants to actuating the decisions, distributed control is required. This paper focuses on the uplink (from mobiles to base stations) and dis-cusses distributing the decision of when and when not to transmit data (distributed scheduling) to the mobiles. The scheme, uplink transmission timing, utilizes mobile transmitter power control feedback from the base station receiver to determine whether the channel is favorable or not compared to the average channel condition. Thereby, the battery consumption and disturbing power to other connections are reduced. The algorithm can be described as a feedback control system. Some transient behaviors are analyzed using systems theory, and supported by wireless network simulations of a system with a WCDMA (Wideband Code Division Multiple Access) radio interface as in most 3G systems.

    Fulltekst (pdf)
    FULLTEXT01
  • 3836.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Eliminating the Initial State for the Generalized Likelihood Ratio Test2006Inngår i: Proceedings of the 6th IFAC Symposium on Fault Detection, Supervision and Safety of Technical Processes, 2006, s. 699-604Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fault detection based on comparing a batch of data with a model of the system using the generalized likelihood ratio test is considered. Careful treatment of the initial state of the model is quite important, in particular for short batch sizes. There are two standard approaches to this problem. One is based on a parity space, where the influence ofinitial state is removed by projection, and the other on using prior information obtained by Kalman filtering past data. A new idea of anti-causal Kalman filtering in the present data batch is introduced and compared to the previous methods. An efficient parameterization of incipient faults is given. It is shown in simulations of torque disturbances on a DCmotor that efficient fault profile parameterization and using smoothed estimates of the initial state increase performance considerably. (Copyright 2006 IFAC)

  • 3837.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Eliminating the Initial State for the Generalized Likelihood Ratio Test2006Rapport (Annet vitenskapelig)
    Abstract [en]

    Fault detection based on comparing a batch of data with a model of the system using the generalized likelihood ratio test is considered. Careful treatment of the initial state of the model is quite important, in particular for short batch sizes. There are two standard approaches to this problem. One is based on a parity space, where the influence ofinitial state is removed by projection, and the other on using prior information obtained by Kalman filtering past data. A new idea of anti-causal Kalman filtering in the present data batch is introduced and compared to the previous methods. An efficient parameterization of incipient faults is given. It is shown in simulations of torque disturbances on a DCmotor that efficient fault profile parameterization and using smoothed estimates of the initial state increase performance considerably.

    Fulltekst (pdf)
    FULLTEXT01
  • 3838.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Unifying the Parity-Space and GLR Approach to Fault Detection with an IMU Application2008Rapport (Annet vitenskapelig)
    Abstract [en]

    Using the parity-space approach, a residual is formed by applying a projection to a batch of observed data and this is a well established approach to fault detection. Based on a stochastic state space model, the parity-space residual can be put into a stochastic framework where conventional hypothesis tests apply. In an on-line application, the batch of data corresponds to a sliding window and in this contribution we develop an improved on-line algorithm that extends the parity-space approach by taking prior information from previous observations into account. For detection of faults, the Generalized Likelihood Ratio (GLR) test is used. This framework allows for including prior information about the initial state, yielding a test statistic with a significantly higher sensitivity to faults. Another key advantage with this approach is that it can be extended to nonlinear systems using an arbitrary nonlinear filter for state estimation, and a linearized model around a nominal state trajectory in the sliding window. We demonstrate the algorithm on data from an Inertial Measurement Unit (IMU), where small and incipient magnetic disturbances are detected using a nonlinear system model.

    Fulltekst (pdf)
    FULLTEXT01
  • 3839.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Unifying the Parity-Space and GLR Approach to Fault Detection with an IMU Application2008Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using the parity-space approach, a residual is formed by applying a projection to a batch of observed data and this is a well established approach to fault detection. Based on a stochastic state space model, the parity-space residual can be put into a stochastic framework where conventional hypothesis tests apply. In an on-line application, the batch of data corresponds to a sliding window and in this contribution we develop an improved on-line algorithm that extends the parity-space approach by taking prior information from previous observations into account. For detection of faults, the Generalized Likelihood Ratio (GLR) test is used. This framework allows for including prior information about the initial state, yielding a test statistic with a significantly higher sensitivity to faults. Another key advantage with this approach is that it can be extended to nonlinear systems using an arbitrary nonlinear filter for state estimation, and a linearized model around a nominal state trajectory in the sliding window. We demonstrate the algorithm on data from an Inertial Measurement Unit (IMU), where small and incipient magnetic disturbances are detected using a nonlinear system model.

  • 3840.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Klein, Inger
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    GLR Tests for Fault Detection over Sliding Data Windows2005Inngår i: Proceedings of the 16th IFAC World Congress, 2005, s. 124-124Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Generalized Likelihood Ratio (GLR) test for fault detection as derived by Willsky and Jones is a recursive method to detect additive changes in linear systems in a Kalman filter framework. Here, we evaluate the GLR test on a sliding window and compare it to stochastic parity space approaches. Robust fault detection defined as being insensitive to faults in the signal space is also studied in the GLR framework.

  • 3841.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Klein, Inger
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    GLR Tests for Fault Detection over Sliding Data Windows2004Rapport (Annet vitenskapelig)
    Abstract [en]

    The Generalized Likelihood Ratio (GLR) test for fault detection as derived by Willsky and Jones is a recursive method to detect additive changes in linear systems in a Kalman filter framework. Here, we evaluate the GLR test on a sliding window and compare it to stochastic parity space approaches. Robust fault detection defined as being insensitive to faults in the signal space is also studied in the GLR framework.

    Fulltekst (pdf)
    FULLTEXT01
  • 3842.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Klein, Inger
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    GLR Tests for Fault Detection over Sliding Data Windows2005Rapport (Annet vitenskapelig)
    Abstract [en]

    The Generalized Likelihood Ratio (GLR) test for fault detection as derived by Willsky and Jones is a recursive method to detect additive changes in linear systems in a Kalman filter framework. Here, we evaluate the GLR test on a sliding window and compare it to stochastic parity space approaches. Robust fault detection defined as being insensitive to faults in the signal space is also studied in the GLR framework.

    Fulltekst (pdf)
    FULLTEXT01
  • 3843.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Tight Integration Between IMU and GPS for Sounding Rockets2010Rapport (Annet vitenskapelig)
    Abstract [en]

    This report presents integrity monitoring and integration methods for an Inertial Measurement Unit (IMU) and a gps receiver. The methods are applied to data from a Maxus sounding rocket used for microgravity research. It is crucial to determine the rocket position during launch to ensure a safe landing location. Today, the navigation relies on IMU integration only. Involving a GPS receiver enhances the position accuracy but there is a need for protection against faulty satellite range measurements. Monitoring over a sequence of the measurements gives higher confidence to the tests.

    Fulltekst (pdf)
    FULLTEXT01
  • 3844.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Window Based GPS Integrity Test using Tight GPS/IMU Integration Applied to a Sounding Rocket2010Inngår i: Proceedings of the 2010 IEEE Aerospace Conference, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents an integrity monitoring method for tight integration of an Inertial Measurement Unit (IMU) and a GPS receiver. The method is applied to data from a Maxus sounding rocket used for microgravity research. It is crucial to determine the rocket position during launch to ensure a safe landing location. Today, the navigation relies on IMU integration only. Involving a GPS receiver enhances the position accuracy but there is a need for protection against faulty satellite range measurements. Monitoring over a sequence of the measurements gives higher confidence to the tests.

  • 3845.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Saha, Saikat
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Fault Detection using Nonlinear Parameter Estimation2011Inngår i: Proceedings of the 2011 IEEE Aerospace Conference, 2011, , s. 6Konferansepaper (Fagfellevurdert)
    Abstract [en]

    For linear and Gaussian systems, fault detection over a batch of data is well-studied, and analytical solutions exist in a stochastic framework. The parity space approach handles additive faults and can be shown to be equivalent to estimating the state trajectory and then removing its influence on the output sequence. Multiplicative faults in linear systems can be handled using parameter estimation methods, such as the EM-algorithm in combination with the Kalman smoother. For nonlinear and non-Gaussian systems, we propose to estimate the state trajectory and the faults over the data batch using a particle smoother and the EM-algorithm. The result is a generic fault detection and isolation scheme that applies to arbitrary nonlinear and non-Gaussian systems, where the faults are monitored over a sliding window.

  • 3846.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Schön, Thomas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Detecting Spurious Features using Parity Space2008Rapport (Annet vitenskapelig)
    Abstract [en]

    Detection of spurious features is instrumental in many computer vision applications. The standard approach is feature based, where extracted features are matched between the image frames. This approach requires only vision, but is computer intensive and not yet suitable for real-time applications. We propose an alternative based on algorithms from the statistical fault detection literature. It is based on image data and an inertial measurement unit (IMU). The principle of analytical redundancy is applied to batches of measurements from a sliding time window. The resulting algorithm is fast and scalable, and requires only feature positions as inputs from the computer vision system. It is also pointed out that the algorithm can be extended to also detect nonstationary features (moving targets for instance). The algorithm is applied to real data from an unmanned aerial vehicle in a navigation application.

    Fulltekst (pdf)
    FULLTEXT01
  • 3847.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Schön, Thomas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Detecting Spurious Features using Parity Space2008Inngår i: Proceedings of the 10th International Conference on Control, Automation, Robotics and Vision, 2008, s. 353-358Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Detection of spurious features is instrumental in many computer vision applications. The standard approach is feature based, where extracted features are matched between the image frames. This approach requires only vision, but is computer intensive and not yet suitable for real-time applications. We propose an alternative based on algorithms from the statistical fault detection literature. It is based on image data and an inertial measurement unit (IMU). The principle of analytical redundancy is applied to batches of measurements from a sliding time window. The resulting algorithm is fast and scalable, and requires only feature positions as inputs from the computer vision system. It is also pointed out that the algorithm can be extended to also detect nonstationary features (moving targets for instance). The algorithm is applied to real data from an unmanned aerial vehicle in a navigation application.

  • 3848.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Schön, Thomas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Karlsson, Rickard
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Particle Filter SLAM with High Dimensional Vehicle Model2008Rapport (Annet vitenskapelig)
    Abstract [en]

    This work presents a particle filter (PF) method closely related to FastSLAM for solving the simultaneous localization and mapping (SLAM) problem. Using the standard FastSLAM algorithm, only low-dimensional vehicle models can be handled due to computational constraints. In this work an extra factorization of the problem is introduced that makes high-dimensional vehicle models computationally feasible. Results using experimental data from a UAV (helicopter) are presented. The algorithm fuses measurements from on-board inertial sensors (accelerometer and gyro), barometer, and vision in order to solve the SLAM problem.

    Fulltekst (pdf)
    FULLTEXT01
  • 3849.
    Törnqvist, David
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Schön, Thomas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Karlsson, Rickard
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Particle Filter SLAM with High Dimensional Vehicle Model2009Inngår i: Journal of Intelligent and Robotic Systems, ISSN 0921-0296, E-ISSN 1573-0409, Vol. 55, nr 4, s. 249-266Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work presents a particle filter (PF) method closely related to FastSLAM for solving the simultaneous localization and mapping (SLAM) problem. Using the standard FastSLAM algorithm, only low-dimensional vehicle models can be handled due to computational constraints. In this work an extra factorization of the problem is introduced that makes high-dimensional vehicle models computationally feasible. Results using experimental data from a UAV (helicopter) are presented. The algorithm fuses measurements from on-board inertial sensors (accelerometer and gyro), barometer, and vision in order to solve the SLAM problem.

  • 3850.
    Törnroth, Oscar
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nyberg, Truls
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Design and Implementation of a Strategy for Path Tracking on Autonomous Heavy-Duty Vehicles2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this thesis, a combined feedforward and feedback controller for improved path tracking on autonomous heavy-duty vehicles is designed and implemented. The steering wheel is controlled in order to follow a reference curvature, computed by a higher-level MPC, responsible for minimizing the distance to a planned path.

    The steering dynamics, from steering wheel via wheel angles, to a measurable vehicle curvature, is modeled, and a conversion from desired curvature gain to input angle to the steering wheel is derived.

    Tests with an autonomous Scania R580 show that the desired curvature can be followed with satisfactory small error, both in a designed slalom path and on a more generic test track. By utilizing future curvature values computed by the MPC, a non-causal feedforward controller can reduce the delay from input to the steering wheel to a measured response in curvature, by almost two thirds, compared to the currently implemented solution.

    Compared to an open-loop control design, tests in simulation show that a feedback controller can reduce errors in curvature gain. However, with the identified steering dynamics and the improved conversion from steering wheel angle to curvature, no further improvement in the curvature gain was seen when implementing the feedback controller in the test vehicle. Care must also be taken not to introduce instability in the system when the feedback controller is implemented in series with a high-level MPC.

    Fulltekst (pdf)
    fulltext
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