| 1. |
- Kersten, Anton, 1991
(författare)
-
Modular Battery Systems for Electric Vehicles based on Multilevel Inverter Topologies - Opportunities and Challenges
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modular battery systems based on multilevel inverter (MLI) topologies can possibly overcome some shortcomings of two-level inverters when used for vehicle propulsion. The results presented in this thesis aim to point out the advantages and disadvantages, as well as the technical challenges, of modular vehicle battery systems based on MLIs in comparison to a conventional, two-level IGBT inverter drivetrain. The considered key aspects for this comparative investigation are the drive cycle efficiency, the inverter cost, the fault tolerance capability of the drivetrain and the conducted electromagnetic emissions. Extensive experiments have been performed to support the results and conclusions. In this work, it is shown that the simulated drive cycle efficiency of different low-voltage-MOSFET-based, cascaded seven-level inverter types is improved in comparison to a similarly rated, two-level IGBT inverter drivetrain. For example, the simulated WLTP drive cycle efficiency of a cascaded double-H-bridge (CDHB) inverter drivetrain in comparison to a two-level IGBT inverter, when used in a small passenger car, is increased from 94.24% to 95.04%, considering the inverter and the ohmic battery losses. In contrast, the obtained efficiency of a similar rated seven-level cascaded H-bridge (CHB) drivetrain is almost equal to that of the two-level inverter drivetrain, but with the help of a hybrid modulation technique, utilizing fundamental selective harmonic elimination at lower speeds, it could be improved to 94.85%. In addition, the CDHB and CHB inverters’ cost, in comparison to the two-level inverter, is reduced from 342€ to 202€ and 121€, respectively. Furthermore, based on a simple three-level inverter with a dual battery pack, it is shown that MLIs inherently allow for a fault tolerant operation. It is explained how the drivetrain of a neutral point clamped (NPC) inverter can be operated under a fault condition, so that the vehicle can drive with a limited maximum power to the next service station, referred to as limp home mode. Especially, the detection and localization of open circuit faults has been investigated and verified through simulations and experiments. Moreover, it is explained how to measure the conducted emissions of an NPC inverter with a dual battery pack according to the governing standard, CISPR 25, because the additional neutral point connection forms a peculiar three-wire DC source. To separate the measured noise spectra into CM, line-DM and phase-DMquantities, two hardware separators based on HF transformers are developed and utilized. It is shown that the CM noise is dominant. Furthermore, the CM noise is reduced by 3dB to 6dB when operating the inverter with three-level instead of two-level modulation.
|
|
| 2. |
|
|
| 3. |
- del Aguila Pla, Pol, 1990-, et al.
(författare)
-
Clock synchronization over networks - Identifiability of the sawtooth model
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we analyze the two-node joint clocksynchronization and ranging problem. We focus on the case of nodes that employ time-to-digital converters to determine the range between them precisely. This specific design leads to a sawtooth model for the captured signal, which has not been studied in detail before from an estimation theory standpoint. In the study of this model, we recover the basic conclusion of a well-known article by Freris, Graham, and Kumar in clock synchronization. Additionally, we discover a surprising identifiability result on the sawtooth signal model: noise improves the theoretical condition of the estimation of the phase and offset parameters. To complete our study, we provide performance references for joint clock synchronization and ranging. In particular, we present the Cramér-Rao lower bounds that correspond to a linearization of our model, as well as a simulation study on the practical performance of basic estimation strategies under realistic parameters. With these performance references, we enable further research in estimation strategies using the sawtooth model and pave the path towards industrial use.
|
|
| 4. |
- Bengtsson, Lars, 1963
(författare)
-
Embedded Measurement Systems
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The subject of Embedded Measurement Systems (EMS) is the merging of embedded systems and electrical measurement systems. This indicates that EMSs are hardware-software systems dedicated to measuring one or a few physical quantities. Applications are numerous; EMSs measure the temperature in refrigerators, freezers, irons, ovens and automobile combustion engines, they sense vibrations in tilt alarms and game consoles, they measure airflow in engines and ventilation systems, they measure shock impact in crash detectors and are used as shock and temperature loggers for transport goods, they measure air pressure in airplane cabins, humidity in air-conditioned environments, they measure liquid levels in fuel tanks, they detect smoke in fire alarms, they measure the viscosity of lubricant oil in engines, they measure the rotation speed of spinning wheels (in any engine), they measure torque in engines and are used as heart rate and ECG detectors in medicine etc. The commercial demand for ever cheaper products and worldwide environmental legislations force vendors to continuously look for more cost-efficient and less power-consuming solutions for their embedded measurement systems. This thesis is concerned most of all with the implementation of cost-efficient/low-power measurement systems in embedded controllers. This includes some novel ideas in voltage, time and resistance measurements with embedded controllers and it will demonstrate how these quantities, analog in nature, can be measured accurately and precisely by inherently digital embedded controllers.
|
|
| 5. |
- Bengtsson, Lars, 1963
(författare)
-
RISC-baserad 50 MHz räknare med alfanumerisk display
- 1995
-
Ingår i: Allt om elektronik. ; 6, s. 35-37
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Denna artikel presenterar en konstruktion som använder en RISC-kontroller (PIC16C54) som frekvensräknare. Frekvensen räknas på controllerns RTCC-ingång och signalfrekvensen, uttryckt i kHz visas på en alfanumerisk display.
|
|
| 6. |
- Di Orio, Giovanni, et al.
(författare)
-
The PRIME Semantic Language: Plug and Produce in Standard- based Manufacturing Production Systems
- 2015
-
Ingår i: Proceedings of the Flexible Automation and Intelligent Manufacturing Conference.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Nowadays manufacturing production systems are becoming more and more responsive in order to succeed in ahighly unstable environment. The capability of a production system to effectively and efficiently adapt and evolveto face the changing requirements – imposed by volatile and dynamic global markets – is a necessary conditionto enable manufacturing enterprises to be agile. Since the agility of a manufacturing enterprise is always limitedby the agility of its own building blocks than it needs to be spread over the whole enterprise including the operationand information technologies (OT/IT). Turning to production systems, one of the significant challenges isrepresented by the possibility to provide easy and rapid (re-)configuration of their internal components and/orprocesses. Innovative technologies and paradigms have been explored during the years that combined with theincreasing advancement in manufacturing technologies enable the implementation of the “plug and produce”paradigm. The “plug and produce” paradigm is the foundation of any agile production system, since to be agile itis inevitably required to reduce the installation and (re-)engineering activities time – changing/adapting the systemto new requirements – while promoting configuration rather than programming. Therefore, the “plug andproduce” paradigm is a necessary but not sufficient condition for implementing agile production systems. Modernproduction systems are typically known for their plethora of heterogeneous component/equipment. In this complexscenario, the implementation of the “plug and produce” paradigm implies the existence of a well-definedontological model to support components/equipment abstraction with the objective to allow interactions,collaboration and knowledge sharing between them. The PRIME semantic language specifies the semanticstructure for the knowledge models and overall system communication language.
|
|
| 7. |
- Yin, Hang, et al.
(författare)
-
Policy Learning with Embedded Koopman Optimal Control
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Embedding an optimization process has been explored for imposing efficient and flexible policy structures. Existing work often build upon nonlinear optimization with explicitly unrolling of iteration steps, making policy inference prohibitively expensive for online learning and real-time control. Our approach embeds a linear-quadratic-regulator (LQR) formulation with a Koopman representation, thus exhibiting the tractability from a closed-form solution and richness from a non-convex neural network. We use a few auxiliary objectives and reparameterization to enforce optimality conditions of the policy that can be easily integrated to standard gradient-based learning. Our approach is shown to be effective for learning policies rendering an optimality structure and efficient reinforcement learning, including simulated pendulum control, 2D and 3D walking, and manipulation for both rigid and deformable objects. We also demonstrate real world application in a robot pivoting task.
|
|
| 8. |
- Alam, Assad, et al.
(författare)
-
Cooperative driving according to Scoop
- 2011
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- KTH Royal Institute of Technology and Scania are entering the GCDC 2011 under the name Scoop –Stockholm Cooperative Driving. This paper is an introduction to their team and to the technical approach theyare using in their prototype system for GCDC 2011.
|
|
| 9. |
- Krook, Jonas, 1986
(författare)
-
Formal Methods and Safety for Automated Vehicles: Modeling, Abstractions, and Synthesis of Tactical Planners
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One goal of developing automated road vehicles is to completely free people from driving tasks. Automated vehicles with no human driver must handle all traffic situations that human drivers are expected to handle, possibly more. Though human drivers cause a lot of traffic accidents, they still have a very low accident and failure rate that automated vehicles must match. Tactical planners are responsible for making discrete decisions for the coming seconds or minutes. As with all subsystems in an automated vehicle, these planners need to be supported with a credible and convincing argument of their correctness. The planners interact with other road users in a feedback loop, so their correctness depends on their behavior in relation to other drivers and road users over time. One way to ascertain their correctness is to test the vehicles in real traffic. But to be sufficiently certain that a tactical planner is safe, it has to be tested on 255 million miles with no accidents. Formal methods can, in contrast to testing, mathematically prove that given requirements are fulfilled. Hence, these methods are a promising alternative for making credible arguments for tactical planners’ correctness. The topic of this thesis is the use of formal methods in the automotive industry to design safe tactical planners. What is interesting is both how automotive systems can be modeled in formal frameworks, and how formal methods can be used practically within the automotive development process. The main findings of this thesis are that it is viable to formally express desired properties of tactical planners, and to use formal methods to prove their correctness. However, the difficulty to anticipate and inspect the interaction of several desired properties is found to be an obstacle. Model Checking, Reactive Synthesis, and Supervisory Control Theory have been used in the design and development process of tactical planners, and these methods have their benefits, depending on the application. To be feasible and useful, these methods need to operate on both a high and a low level of abstraction, and this thesis contributes an automatic abstraction method that bridges this divide. It is also found that artifacts from formal methods tools may be used to convincingly argue that a realization of a tactical planner is safe, and that such an argument puts formal requirements on the vehicle’s other subsystems and its surroundings.
|
|
| 10. |
- Selvaraj, Yuvaraj, 1990
(författare)
-
On Provably Correct Decision-Making for Automated Driving
- 2020
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The introduction of driving automation in road vehicles can potentially reduce road traffic crashes and significantly improve road safety. Automation in road vehicles also brings several other benefits such as the possibility to provide independent mobility for people who cannot and/or should not drive. Many different hardware and software components (e.g. sensing, decision-making, actuation, and control) interact to solve the autonomous driving task. Correctness of such automated driving systems is crucial as incorrect behaviour may have catastrophic consequences. Autonomous vehicles operate in complex and dynamic environments, which requires decision-making and planning at different levels. The aim of such decision-making components in these systems is to make safe decisions at all times. The challenge of safety verification of these systems is crucial for the commercial deployment of full autonomy in vehicles. Testing for safety is expensive, impractical, and can never guarantee the absence of errors. In contrast, formal methods , which are techniques that use rigorous mathematical models to build hardware and software systems can provide a mathematical proof of the correctness of the system. The focus of this thesis is to address some of the challenges in the safety verification of decision-making in automated driving systems. A central question here is how to establish formal verification as an efficient tool for automated driving software development. A key finding is the need for an integrated formal approach to prove correctness and to provide a complete safety argument. This thesis provides insights into how three different formal verification approaches, namely supervisory control theory, model checking, and deductive verification differ in their application to automated driving and identifies the challenges associated with each method. It identifies the need for the introduction of more rigour in the requirement refinement process and presents one possible solution by using a formal model-based safety analysis approach. To address challenges in the manual modelling process, a possible solution by automatically learning formal models directly from code is proposed.
|
|
