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- Touqir Pasha, Muhammad
(författare)
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Circuit Design for All-Digital Frequency Synthesizers
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The market for low cost portable electronics is rapidly growing. Physical activity monitors, portable music players, and smart watches are fast becoming a part of daily life. As the market for wearable devices has grown, a primary concern for IC manufacturers is to provide low cost, low power and lightweight circuit solutions. In a bid to lower the costs and extend battery life there is an increased interest in using low-cost, low-power CMOS processes. As a result fully integrated systems on chips (SOC) have been realized that efficiently perform the required functions. These SOCs house digital, analog and in some cases radio circuits on a single die in a bid to reduce cost and improve productivity.Phase Locked Loops (PLLs) are a key building block for all SOCs where they are used to generate clock signals for synchronous systems. In monolithic implementations the design cost of a circuit is measured in terms of the silicon area and not the number of devices in the circuit. With the advent of all-digital techniques, there is a renewed interest in the design of compact PLLs as the area occupied by the traditional PLLs is very large due to the presence of large passive components in the loop filter and the oscillator. As a result, various digital circuit design techniques are being explored to design compact all-digital PLLs (ADPLLs) while satisfying the performance requirements for the target applications.The focus of this work is to explore new techniques for area, power and time efficient design of ADPLL component blocks. The first part of this works focuses on the feasibility of using automatic place and route (P&R) tools to synthesize a time-to-digital converter (TDC). An area efficient TDC is synthesized in a 65 nm CMOS process using automated P&R which exhibits a time resolution of 6.5 ps with an input sampling rate of 100 MS/s while occupying an area of 0.002 mm2. A modified switching scheme is also presented which reduces the power consumption of the thermometer-to-binary encoder by up to 40%.The second part of this thesis proposes a power supply filter for mitigating the affect of cyclostationary noise on the voltage controlled ring oscillator. The key idea is to raise the impedance in the current supply during the sensitive periods and lower it during insensitive periods of the oscillator operation. To demonstrate the feasibility of the proposed filter, a pseudo differential ring oscillator is designed in a 65 nm CMOS process which exhibits an rms jitter of less than 14 ps at 2.4 GHz in the presence of a 500 mV noise tone in the power supply.
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- Leander, John, 1976-, et al.
(författare)
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Dataset for damage detection retrieved from a monitored bridge pre and post verified damage
- 2023
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Ingår i: Data in Brief. - : Elsevier BV. - 2352-3409. ; 51
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Tidskriftsartikel (refereegranskat)abstract
- The Vänersborg Bridge in southwest Sweden is a single-leaf bascule bridge carrying railway traffic over a canal. The load consists of passing commuter trains, occasional freight trains and leaf openings to allow ships to pass on the canal. The bridge constructed from 1914 to 1916 was built by riveted truss members in steel. Over the years, several assessments and maintenance actions have been performed to keep the bridge in service. During autumn 2021, a long-term monitoring campaign was initiated with the installation of sensors to register the load effect and possible changes in the behaviour. In March 2023, the cloud-based service employed detected an abrupt change of behaviour. An emergency inspection revealed a large crack in one of the truss members in the counter-weight part. The published dataset contains sensor data from 64 registered bridge openings, comprising accelerations, strains, inclinations, and weather conditions. Data from before the fracture, during, and after are provided. During the bridge opening events, the data was recorded continuously with a sampling rate of 200 Hz. The evidence of damage in a real case scenario makes the dataset valuable for testing and evaluation of data-driven routines for infrastructure surveillance.
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- Mai, Vien V., et al.
(författare)
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A FAST AND ACCURATE SPLITTING METHOD FOR OPTIMAL TRANSPORT : ANALYSIS AND IMPLEMENTATION
- 2022
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Ingår i: ICLR 2022. - : International Conference on Learning Representations, ICLR.
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Konferensbidrag (refereegranskat)abstract
- We develop a fast and reliable method for solving large-scale optimal transport (OT) problems at an unprecedented combination of speed and accuracy. Built on the celebrated Douglas-Rachford splitting technique, our method tackles the original OT problem directly instead of solving an approximate regularized problem, as many state-of-the-art techniques do. This allows us to provide sparse transport plans and avoid numerical issues of methods that use entropic regularization. The algorithm has the same cost per iteration as the popular Sinkhorn method, and each iteration can be executed efficiently, in parallel. The proposed method enjoys an iteration complexity O(1/∊) compared to the best-known O(1/∊2) of the Sinkhorn method. In addition, we establish a linear convergence rate for our formulation of the OT problem. We detail an efficient GPU implementation of the proposed method that maintains a primal-dual stopping criterion at no extra cost. Substantial experiments demonstrate the effectiveness of our method, both in terms of computation times and robustness.
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- Ng, Amos, et al.
(författare)
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FACTS ANALYSER: AN INNOVATIVE TOOL FOR FACTORY CONCEPTUAL DESIGN USING SIMULATION
- 2007
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Ingår i: The Swedish Production Symposium in Göteborg 28-30 August 2007.
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Konferensbidrag (refereegranskat)abstract
- Despite simulation possesses an established background and offers tremendous promise for designing and analysing complex production systems, manufacturing industry has been less successful in using it as a decision support tool, especially in the early conceptual phase of factory design. If simulation is used today for system design, it is more often used in later phases when important designdecisions have already been made and costs are locked. With an aim to advocate the use of simulation in early phases of factory design, this paper introduces FACTS Analyser, a toolset developed based on the concept of integrating model abstraction, input data management and simulation-based optimisation under an innovative framework. Specifically, it addresses a novel aggregation method, which is based on Effective Processing Time, for modelling variability of workstations. Other features like simulation model generation, parallel simulation, optimisation and output data analysis that are provided by FACTS Analyser, through a Web Services interface, are also revealed. The aggregation method, when combined together with other system components, can synthetically enable simulation to become easier to use and speed up the time-consuming model building and experimentation process, which are required in conceptual design phases of production systems. Initial validation results applied to a trucks assembly plant is also given.
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- Olofsson, Björn, et al.
(författare)
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Sensor Fusion for Robotic Workspace State Estimation
- 2016
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Ingår i: IEEE/ASME Transactions on Mechatronics. - 1083-4435. ; 21:5, s. 2236-2248
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Tidskriftsartikel (refereegranskat)abstract
- We consider the problem of tool position and orientation state estimation for robot manipulators in workspace by sensor fusion of the internal robot joint measurements with inertial measurement unit data. A prerequisite for this to be successful is accurate calibration of the sensors used. Therefore, we discuss a method for calibration of the sensor with respect to the robot end-effector, which is straightforward to apply on an arbitrary industrial manipulator. We also consider two different workspace state-estimation algorithms requiring a minimum of robot modeling; the first is based on the extended Kalman filter and the second is based on the Rao-Blackwellized particle filter. The calibration procedure and the state-estimation algorithms were evaluated and compared in extensive experiments. Both state-estimation algorithms exhibited an accuracy improvement compared to estimates provided by the forward kinematics of the robot. Moreover, both algorithms were shown to satisfy the constraints of real-time execution at 4-ms sampling period. To further evaluate and compare the robustness of the methods, the algorithms were investigated with respect to the sensitivity of the filter parameters and the noise modeling.
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- Ringbäck, Rasmus, et al.
(författare)
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Multi-Agent Formation Tracking for Autonomous Surface Vehicles
- 2021
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Ingår i: IEEE Transactions on Control Systems Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 1063-6536 .- 1558-0865. ; 29:6, s. 2287-2298
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Tidskriftsartikel (refereegranskat)abstract
- In this article, the problem of collaborative tracking of an underwater target using autonomous surface vehicles (ASVs) is studied. Distance-based formation control with a collision-avoidance potential function is employed as a solution. A formation control protocol is devised and applied to the formation tracking problem. With the protocol, the vehicles form a desired formation around a moving target in order to continuously estimate its position, while the centroid of the formation tracks the target. Almost global stability is proved for the case with three tracking agents. A fully operational platform with four ASVs was built to implement the derived algorithms. One of the vehicles was used to simulate a target and the rest to form a triangular formation around it. Power usage of a naval vessel is highly affected by water resistance forces which increases significantly with the velocity. This was accounted for by adding an additional term to the formation tracking protocol, thereby increasing the overall system endurance. Experimental results are presented.
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