Calibrating a Robot Camera

This paper addresses the problem of calibrating a camera mounted on a robot arm. The objective is to estimate the camera's intrinsic and extrinsic parameters. These include the relative position and orientation of camera with respect to robot base as well as the relative position and orientation of the camera with respect to a pre-defined world frame. A calibration object with a known 3D shape is used together with two known movements of the robot. A method is presented to find calibration parameters within an opti-misation framework. This method differs from existing methods in that 1) it fully exploits information from different displacements of the camera to produce an optimal calibration estimate, and 2) it uses an evolutionary algo-rithm to attain the optimal solution. Experimental results on both synthetic and real data are presented.

Study on the technology and properties of 3D bioprinting SF/GT/n-HA composite scaffolds

In this paper, three kinds of natural polymer materials, silk fibroin (SF), gelatin (GT), and nano-hydroxyapatite (n-HA), are mixed as 3D printing bioink to mimic protein polysaccharide and collagen fibers in natural articular cartilage. By changing the SF content, SF/GT/n-HA composite scaffolds with different ratios are prepared using 3D bioprinting technology. The microstructure and morphology, biological properties and mechanical properties of composite scaffolds are characterized. The results show that the printing precision of the bioink with 10% SF is best, and the composite scaffold with 10% SF also exhibits better mechanical properties, whose tensile elastic modulus is 10.60 ± 0.32 MPa and the compression elastic modulus is 1.22 ± 0.06 MPa. These studies are helpful to understand the interaction between SF, GT and n-HA, and provide a theoretical basis for the preparation of better silk fibroin-based composite scaffolds

Recognition of Cylindrical Objects Using Occluding Boundaries Obtained from Colour Based Segmentation

This paper describes a method for model-based recognition of cylindrical ob-jects from occluding boundaries obtained by computationally efficient colour segmentation of a 2D image. The models are invoked by combining geomet-ric and colour features. Occluding boundaries of hypothesized objects are generated using colour segmentation and ground plane constraint. Hypothe-sis verification is achieved by evaluating the fit between occluding boundary generated by the hypothesised object and the edge data. This method dif-fers from existing methods in that it integrates multiple measurements and prior knowledge to achieve robust object recognition. Experiments with real images have been carried out and the results are promising.

Preparation of PVA-GO Composite Hydrogel and Effect of Ionic Coordination on Its Properties

This paper adopts a method combining hybrid self-assembly, cyclic freezing-thawing and annealing treatment to prepare polyvinyl alcohol (PVA) and graphene oxide (GO) composite hydrogel. Then, the PVA-GO composite hydrogels are re-swelled in different ionic solutions (NaCl, MgCl2, CaCl2 and AlCl3) to improve mechanical strength, toughness and wear resistance by the ionic coordination bonds. The microstructure and morphology are characterized by Fourier transforms infrared spectroscopy (FTIR), x-ray diffraction (XRD) and Scanning electron microscopy (SEM), finding that the internal structure is porous three-dimensional network. Mechanical experiments indicate that the composite hydrogel with GO content of 0.05 wt% immersed in MgCl2 solution displays the best mechanical properties overall. Its tensile strength can reach 11.10 MPa and the elastic modulus reaches 1.72 MPa, which is 175% and 85% higher than the pure PVA, respectively. Sliding friction experiments illustrate that the composite hydrogel immersed in AlCl3 solution exhibits the lowest friction coefficient, and the higher the valence state of metal cation is, the better the wear reduction effect is. We expect to enrich the development of PVA-GO hydrogels in tissue engineering through synergy of hydrogen bonds and ionic coordination bonds

System-level biological effects of extremely low-frequency electromagnetic fields: an in vivo experimental review

During the past decades, the potential effects of extremely low-frequency electromagnetic fields (ELF-EMFs) on human health have gained great interest all around the world. Though the International Commission on Non-Ionizing Radiation Protection recommended a 100 μT, and then a 200 μT magnetic field limit, the long-term effects of ELF-EMFs on organisms and systems need to be further investigated. It was reported that both electrotherapy and possible effects on human health could be induced under ELF-EM radiation with varied EM frequencies and fields. This present article intends to systematically review the in vivo experimental outcome and the corresponding mechanisms to shed some light on the safety considerations of ELF-EMFs. This will further advance the subsequent application of electrotherapy in human health

Investigation of a new integration test environment : Facilitating offline debugging of Hardware-in-the-Loop

Advanced automatic testing is very important in development and research within the vehicle industry. Hardware-in-the-loop (HIL) systems give the ability to validate Electronic Control Units (ECUs) based on software simulation without gathering all of the physical hardware. This enables testing by providing inputs and examining the corresponding outputs of the ECUs in a simpler and safer way than in traditional physical testing. HIL offers the advantage that we can verify and validate the functions of ECUs prior to full-scale hardware production. On the contrary, because HIL systems are normally released as general-purpose test beds, it takes time to embed them into the current system. Additionally, the question of how to fill the gap between the HIL and the test environment is even more critical when the test bed is expected to be used for a long period of time without modifications. Furthermore, HIL systems are precious. It is not practical and will be considered as a waste of resource if it is used exclusively by testers. Scania’s RESI group uses Client-Server architecture to make it more flexible. The HIL system is hosted at server side while the testers operate it at client side. This architecture enables different implementations of client and server as long as a same protocol is applied, but this still does not solve the problem that the HIL is not always accessible when the testers want to debug their scripts. The testers want to find a solution to achieve this goal offline (without servers). To solve the problem, we first investigated which programming languages are used in the industry. Without doubt, there is no dominant language that ideally suits all situations, so secondly, we developed a new test environment. The new environment including “Dummy Mode” and “Mat Mode” is able to provide script validation service on basic and logic levels without servers. The result shows the Dummy mode is able to reach a higher detection rate (99.3%) on simple errors comparing to the current environment (81.3%). By reproducing and reusing the result of HIL system, Mat mode is able to identify logic errors and provide better assistance when the logic errors are found. In general, the proposed environment is able to show a better way of using HIL which makes the whole system more efficient and productive.I fordonsindustrin ställs stora krav på avancerad automatiserad testning. För att utvärdera Electronic Control Units (ECUs) används så kallade Hardware-In-the-Loop-system (HIL) för att simulera den omkringliggande hårdvaran. Detta möjliggör enklare samt säkrare testning av ECU-komponenterna än vid traditionell fysisk testning. Med hjälp av HIL kan ECUs testas innan en fullskalig produktion sätts igång. Då HIL-system vanligtvis utvecklas för ett brett användningsområde kan det ta tid att skräddarsy dem för ett specifikt system. Ett annat viktigt problem vi ställs inför är skillnaderna mellan HIL-systemet och testmiljön, då testfallen förväntas att användas en längre tid utan förändringar. Vidare är HIL-system kostsamma. Det anses vara varken praktiskt eller ekonomiskt att låta HIL-system enbart användas av testare. Scanias RESI-grupp använder en klient-server-arkitektur för att åstadkomma flexibilitet HIL-systemet körs på serversidan medan testarna arbetar på klientsidan. Den här typen av arkitektur öppnar upp för olika implementationer på klient- samt serversida, förutsatt att samma kommunikationsprotokoll används. En nackdel med den nuvarande lösningen är att HIL-systemet inte alltid finns tillgängligt när testarna vill felsöka deras programskript. Testarna vill hitta en lösning där det går att utföra felsökningen lokalt, utan tillgång till servrar. För att kunna lösa problemet undersöktes först vilka programmeringsspråk som används inom industrin. Undersökningen visar på att det finns inget programmeringsspråk som är idealt för alla ändamål. Vidare utvecklades en ny testmiljö som tillhandahåller testlägena "Dummy Mode" samt "Mat Mode". Testmiljön kan användas för att validera programskript på grund- och logiknivå utan att kommunicera mot servrar. Resultatet visar att "Dummy Mode" detekterar upp till 99.3% av enklare typ av fel än motsvarande 81.3% i nuvarande testmiljön. Genom att reproducera och återanvända resultat av HIL-systemet kan “Mat Mode” identifiera logikfel samt ge en bättre indikation om vad felen innebär. Generellt sätt kan den föreslagna testmiljön visa på ett bättre användande av HIL, som gör hela systemet mer effektivt och produktivt

An optimization approach to labelling problems in computer vision.

This thesis is concerned with the development of an optimization based approach to solving labelling problems which involve the assignment of image entities into interpretation categories in computer vision. Attention is mainly focussed on the theoretical basis and computational aspect of continuous relaxation for solving a discrete labelling problem based on an optimization framework. First, a theoretical basis for continuous relaxation is presented which includes the formulation of a discrete labelling problem as a continuous minimization problem and an analysis of labelling unambiguity associated with continuous relaxation. The main advantage of the formulation over existing formulations is the embedding of relational measurements into the specification of a consistent labelling. The analysis provides a sufficient condition for a continuous labelling formulation to ensure that a consistent labelling is unambiguous. Second, a continuous relaxation labelling algorithm based on mean field theory is presented with the aim of approximating simulated annealing in a deterministic manner. The novelty of the algorithm lies in the utilization of mean field theory technique to avoid stochastic optimization for approximating the global optimum of a consistent labelling criterion. This is contrast to the conventional methods which find a local optimum near an initial estimate of labelling. A special three-frame discrete labelling problem of establishing trinocular stereo correspondence and a mixed labelling problem of interpreting image entities in terms of cylindrical objects and their locations are also addressed. For the former, two orientation based geometric constraints are suggested for matching lines among three viewpoints and a method is presented to find a consistent labelling using simulated annealing. For the latter, the image interpretation of 3D cylindrical objects and their 3D locations is achieved using three knowledge sources: edge map, region map and the ground plane constraint. The method differs from existing methods in that it exploits an integrated use of multiple image cues to simplify the interpretation task and improve the interpretation performance. Experimental results on both synthetic data and real images are provided to demonstrate the viability and the potential of the proposed methods throughout the thesis

An optimization approach to labelling problems in computer vision.

This thesis is concerned with the development of an optimization based approach to solving labelling problems which involve the assignment of image entities into interpretation categories in computer vision. Attention is mainly focussed on the theoretical basis and computational aspect of continuous relaxation for solving a discrete labelling problem based on an optimization framework. First, a theoretical basis for continuous relaxation is presented which includes the formulation of a discrete labelling problem as a continuous minimization problem and an analysis of labelling unambiguity associated with continuous relaxation. The main advantage of the formulation over existing formulations is the embedding of relational measurements into the specification of a consistent labelling. The analysis provides a sufficient condition for a continuous labelling formulation to ensure that a consistent labelling is unambiguous. Second, a continuous relaxation labelling algorithm based on mean field theory is presented with the aim of approximating simulated annealing in a deterministic manner. The novelty of the algorithm lies in the utilization of mean field theory technique to avoid stochastic optimization for approximating the global optimum of a consistent labelling criterion. This is contrast to the conventional methods which find a local optimum near an initial estimate of labelling. A special three-frame discrete labelling problem of establishing trinocular stereo correspondence and a mixed labelling problem of interpreting image entities in terms of cylindrical objects and their locations are also addressed. For the former, two orientation based geometric constraints are suggested for matching lines among three viewpoints and a method is presented to find a consistent labelling using simulated annealing. For the latter, the image interpretation of 3D cylindrical objects and their 3D locations is achieved using three knowledge sources: edge map, region map and the ground plane constraint. The method differs from existing methods in that it exploits an integrated use of multiple image cues to simplify the interpretation task and improve the interpretation performance. Experimental results on both synthetic data and real images are provided to demonstrate the viability and the potential of the proposed methods throughout the thesis