Lie Algebraic Unscented Kalman Filter for Pose Estimation

An unscented Kalman filter for matrix Lie groups is proposed where the time propagation of the state is formulated on the Lie algebra. This is done with the kinematic differential equation of the logarithm, where the inverse of the right Jacobian is used. The sigma points can then be expressed as logarithms in vector form, and time propagation of the sigma points and the computation of the mean and the covariance can be done on the Lie algebra. The resulting formulation is to a large extent based on logarithms in vector form, and is therefore closer to the UKF for systems in $\mathbb{R}^n$. This gives an elegant and well-structured formulation which provides additional insight into the problem, and which is computationally efficient. The proposed method is in particular formulated and investigated on the matrix Lie group $SE(3)$. A discussion on right and left Jacobians is included, and a novel closed form solution for the inverse of the right Jacobian on $SE(3)$ is derived, which gives a compact representation involving fewer matrix operations. The proposed method is validated in simulations

Crane feedback control in offshore moonpool operations

A novel feedback controller for cranes employed in heavy-lift offshore marine operations is proposed. The control objective is to reduce the hydrodynamic slamming load acting on a payload at water-entry of moonpool operations; at the same time the values of the wire tension must be kept within acceptable bounds. The effectiveness of the proposed controller is shown experimentally; the experiments are performed on a scale model and show improvements with respect to a previous feedforward controller. (c) 2007 Elsevier Ltd. All rights reserved

Polarization image laser line extraction methods for reflective metal surfaces

In this work, we propose a novel pipeline method for laser line extraction from images with a polarization image sensor. The proposed method is specially developed for strong laser beam reflections from metal surfaces. For the pre-processing stage, we propose a demosaicing algorithm for color polarizer filter array (CPFA) sensors. This can be implemented by using either one quarter or full resolution of the sensor. In addition, we propose two methods for optimizing the information available in a 12-channel color polarization image: The first method, is based on the minimum linearly polarized irradiance, and the second method, is based on the linear polarization intensity. These pre-processing, and optimization methods are combined with laser line extraction methods. The laser line extraction is done with either the Polarized Finite Impulse Response (FIR) Center Of Gravity (COG), where the laser line coordinates are computed from the filtered laser intensity distribution, or with the Polarized FIR-Peak, where the laser line coordinates are calculated from the first derivative of the filtered laser signal. The performance of the proposed algorithms is studied experimentally using a laser line scanner assembly, made of a polarization camera, and a laser line projector operating in the blue wavelength range.acceptedVersio

«Det er litt opp til hver enkelt» : praktikeres faglige utvikling og vedlikehold i praksisfeltet

Bakgrunn for valg av tema: Gjennom denne oppgaven ønsker jeg å sette fokus på sosialarbeideres muligheter til faglig utvikling og vedlikehold i deres arbeidshverdag. Særlig er den nye endringen med NAV- reformen her sentral. Denne legger flere føringer for utviklingen av faget. Samtidig er mange sosialarbeidere ansatt i andre sektorer. Jeg ønsker å se på hvordan man får til en faglig utvikling når arbeidsplassene er relativ små og spredd utover geografisk. Metode: I oppgaven er både kvantitative data og kvalitativt intervjumateriale benyttet (HUSKdata). Dette er for å få tak i de ulike informantens erfaringer, men også hvordan en større del av sosialarbeiderne opplever sine egne muligheter til faglig utvikling. StudData er brukt for å vise forskjeller mellom de dataene som er samlet inn gjennom HUSK- undersøkelsen. Resultat: Forskjellen som kommer frem mellom de som jobber i NAV og de som jobber andre steder gir uttrykk for at det er større muligheter for faglig utvikling utenfor NAV. Samtidig er flertallet av sosialarbeiderne ansatt i NAV. NAV-ansatte har større muligheter til å ta ulike typer utdanning deriblant master. Dette er det eneste punktet de NAV-ansatte skårer høyere på enn de som ikke jobber i NAV. Samtidig er det mange sosialarbeidere som ikke vet om tilbud og rettigheter til faglig utvikling og vedlikehold. I seg selv er dette en oppsiktsvekkende observasjon. Siden man ikke vet om mulighetene har man heller ikke mulighet til å benyttet seg av disse. Sosialarbeiderne rettet fokus mot at hverdagen slett ikke tillater tid til fagutvikling på jobb. Dette kommer særlig til syne i NAV, men gjør seg gjeldende i noen grad også utenfor. Konklusjoner: Det er ikke i tilstrekkelig grad tilrettelagt for faglig utvikling verken i eller utenfor NAV. Det synes midlertidig slik at man i større grad har tid og mer vektlegging av faglig vedlikehold utenfor NAV. Dette kan skyldes at arbeidet er av en annen art når man jobber utenfor NAV og at problemstillinger som synliggjør behovet for faglig vedlikehold i større grad kommer opp her.Background: In this thesis I wanted to focus the attention on what prospects social workers are facing when it comes to further development and maintenance of their profession in their everyday work. In particular, the new reorganization of the NAV-reform is central in this aspect, as it sets the guidelines for the further development of this profession. Meanwhile, many social workers are employed in social service sectors outside of NAV. I also wanted to examine how one manages to develop the profession of social work when in relatively small working places, which may also be scattered geographically. Methods: Both quantitative data and qualitative focus group interview material have been employed in this thesis (HUSK-data). This was done both to cover the different informants’ experiences, but also to obtain knowledge about how social workers perceive their own opportunities for professional development. StudData has been used to demonstrate differences between the data material collected through the HUSK-survey. Results: The apparent differences emerging between the ones working in NAV and the ones working elsewhere, express greater opportunities for further professional development outside of NAV. Meanwhile, the majority of the social workers are employed inside of NAV, and have better opportunities to undertake higher education, including a master’s degree. This is the one point on which the NAV-employed scored higher than the ones not working in NAV. At the same time, many social workers are not even aware of what offers or rights to professional development they are facing. This observation is in itself worrying, since not knowing about ones possibilities eliminates ones chance to make any use of them. The social workers pointed out that the everyday work did not allocate the time needed to practice professional development. This was most obvious in the NAV internally, but to some degree was also apparent for the external ones. Conclusions: Opportunities for further professional development have not been sufficiently facilitated neither inside nor outside of NAV. It seems, however, that more time and emphasis are put down exerting professional development outside of NAV. This could be due to the work itself being of a slightly different manner outside of NAV, and that the need for such professional maintenance may be better highlighted here.Master i sosialt arbei

Vision-based control of a knuckle boom crane with online cable length estimation

A vision-based controller for a knuckle boom crane is presented. The controller is used to control the motion of the crane tip and at the same time compensate for payload oscillations. The oscillations of the payload are measured with three cameras that are fixed to the crane king and are used to track two spherical markers fixed to the payload cable. Based on color and size information, each camera identifies the image points corresponding to the markers. The payload angles are then determined using linear triangulation of the image points. An extended Kalman filter is used for estimation of payload angles and angular velocity. The length of the payload cable is also estimated using a least squares technique with projection. The crane is controlled by a linear cascade controller where the inner control loop is designed to damp out the pendulum oscillation, and the crane tip is controlled by the outer loop. The control variable of the controller is the commanded crane tip acceleration, which is converted to a velocity command using a velocity loop. The performance of the control system is studied experimentally using a scaled laboratory version of a knuckle boom crane

Robotic weld groove scanning for large tubular T-joints using a line laser sensor

This paper presents a novel procedure for robotic scanning of weld grooves in large tubular T-joints. The procedure is designed to record the discrete weld groove scans using a commercially available line laser scanner which is attached to the robot end-effector. The advantage of the proposed algorithm is that it does not require any prior knowledge of the joint interface geometry, while only two initial scanning positions have to be specified. The position and orientation of the following scan are calculated using the data from two previous weld groove scans, so once initiated, the scanning process is fully autonomous. The procedure is a two-step algorithm consisting of the prediction and correction substeps, where the position and orientation of the sensor for the following scan are predicted and corrected. Such a procedure does not require frequent weld groove scanning for navigation along the groove. The performance of the proposed procedure is studied experimentally using an industrial-size T-joint specimen. Several cases of scanning motion parameters have been tested, and a discussion on the results is given.publishedVersio

An EKF for Lie Groups with Application to Crane Load Dynamics

An extended Kalman filter (EKF) for systems with configuration given by matrix Lie groups is presented. The error dynamics are given by the logarithm of the Lie group and are based on the kinematic differential equation of the logarithm, which is given in terms of the Jacobian of the Lie group. The probability distribution is also described in terms of the logarithm as a concentrated Gaussian distribution that is a tightly focused distribution around the identity of the Lie group. The filter is applied to estimation on SO(3) a case where a stereo camera setup tracks a crane wire with a payload. The wire, which is under tension and forms a line is monitored by two 2D-cameras, and a line detector is used to obtain a description of how the wire is projected onto each image plane. A model of a spherical pendulum is applied and the estimator is validated by applying it on simulated data, as well as experimental data

Supporting robotic welding of aluminium with a laser line scanner-based trigger definition method

Automation and the use of robots for welding operations is an important research topic. Being able to automate and, thus, save time for setting up and using robotic welding for complex, large-scale structures made of reflective materials, such as aluminium, will provide clear economic and competitive advantages. However, challenges coming from the ability to accurately detect and calibrate the robot for a given physical workpiece in addition to noises, such as the reflections, make it hard to develop and demonstrate a feasible automation solution. This paper proposes combining laser line scanning technology with CAD-based analysis of a workpiece geometry to support the identification of relevant elements of the workpiece in the physical world and thus support welding operations. An extendable trigger definition method is proposed to identify features of interest in a workpiece. The method can potentially support the execution of welding sequences, which in our case can be represented as a sequence of triggers that have to be observed and followed at the robot runtime to weld the workpiece together.acceptedVersio

Development and Validation of Robotic Cleaning System for Fish Processing Plants

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