Elevation Cable Modeling for Interactive Simulation of Cranes

In this paper, the way to simulate hoisting cables in real time is addressed. We overcome instability in such simulation by considering a two-layered model: a model for the dynamics of a cable passing through a set of pulleys and an oscillation model based on the classical one-dimensional wave equation. The first layer considers the interaction between the cable and pulleys with the elevation equipment, while the second layer simulates cable oscillation. Numerical instability is avoided by suspending the oscillation layer when required. Due to the system properties, this can be carried out in such a way that does not cause significant loss in the system quality. It considers the oscillation of the cable between every pair of pulleys, collision detection and the variation of the cable length very efficiently. Rendering issues are discussed, with remarks on how to prevent aliasing artifacts in the cable. Efficiency is analyzed, including performance tests which show that the model can be run very efficiently. The paper also covers how to integrate the model in a complex multibody simulation with a high degree of interactivity.In this paper, the way to simulate hoisting cables in real time is addressed. We overcome instability in such simulation by considering a two-layered model: a model for the dynamics of a cable passing through a set of pulleys and an oscillation model based on the classical one-dimensional wave equation. The first layer considers the interaction between the cable and pulleys with the elevation equipment, while the second layer simulates cable oscillation. Numerical instability is avoided by suspending the oscillation layer when required. Due to the system properties, this can be carried out in such a way that does not cause significant loss in the system quality. It considers the oscillation of the cable between every pair of pulleys, collision detection and the variation of the cable length very efficiently. Rendering issues are discussed, with remarks on how to prevent aliasing artifacts in the cable. Efficiency is analyzed, including performance tests which show that the model can be run very efficiently. The paper also covers how to integrate the model in a complex multibody simulation with a high degree of interactivity

New Developments in Simulation-Based Harbour Crane Training

This paper presents the efforts that have been made during the development of a set of harbour training simulators to improve their quality. The paper focuses on two main research lines: the improvement of complex physical systems involved in the simulation and the analysis of hardware architecture solutions. Cable-based hoist systems and bulk materials are systems present in different harbour equipment and are usually simulated with poor quality due to their complexity. In this paper physics-based models for the interactive simulation of these systems are proposed and applied to real cases. Also, different hardware simulator architectures are analysed and different approaches are proposed to the problem of choosing the devices for a simulator

Stable Constrained Dynamics

International audienceWe present a unification of the two main approaches to simulate deformable solids, namely elasticity and constraints. Elasticity accurately handles soft to moderately stiff objects, but becomes numerically hard as stiffness increases. Constraints efficiently handle high stiffness, but when integrated in time they can suffer from instabilities in the nullspace directions, generating spurious transverse vibrations when pulling hard on thin inextensible objects or articulated rigid bodies. We show that geometric stiffness, the tensor encoding the change of force directions (as opposed to intensities) in response to a change of positions, is the missing piece between the two approaches. This previously neglected stiffness term is easy to implement and dramatically improves the stability of inextensible objects and articulated chains, without adding artificial bending forces. This allows time step increases up to several orders of magnitude using standard linear solvers

Activities of the Center for Space Construction

The Center for Space Construction (CSC) at the University of Colorado at Boulder is one of eight University Space Engineering Research Centers established by NASA in 1988. The mission of the center is to conduct research into space technology and to directly contribute to space engineering education. The center reports to the Department of Aerospace Engineering Sciences and resides in the College of Engineering and Applied Science. The college has a long and successful track record of cultivating multi-disciplinary research and education programs. The Center for Space Construction is prominent evidence of this record. At the inception of CSC, the center was primarily founded on the need for research on in-space construction of large space systems like space stations and interplanetary space vehicles. The scope of CSC's research has now evolved to include the design and construction of all spacecraft, large and small. Within this broadened scope, our research projects seek to impact the underlying technological basis for such spacecraft as remote sensing satellites, communication satellites, and other special purpose spacecraft, as well as the technological basis for large space platforms. The center's research focuses on three areas: spacecraft structures, spacecraft operations and control, and regolith and surface systems. In the area of spacecraft structures, our current emphasis is on concepts and modeling of deployable structures, analysis of inflatable structures, structural damage detection algorithms, and composite materials for lightweight structures. In the area of spacecraft operations and control, we are continuing our previous efforts in process control of in-orbit structural assembly. In addition, we have begun two new efforts in formal approach to spacecraft flight software systems design and adaptive attitude control systems. In the area of regolith and surface systems, we are continuing the work of characterizing the physical properties of lunar regolith, and we are at work on a project on path planning for planetary surface rovers

Digital technologies for enhancing crane safety in construction: a combined quantitative and qualitative analysis

A digital-enabled safety management approach is increasingly crucial for crane operations, which are common yet highly hazardous activities sensitive to environmental dynamics on construction sites. However, there exists a knowledge gap regarding the current status and developmental trajectory of this approach. Therefore, this paper aims to provide a comprehensive overview of digital technologies for enhancing crane safety, drawing insights from articles published between 2008 and 2021. Special emphasis is placed on the sensing devices currently in use for gathering “man-machine-environment” data, as well as the communication networks, data processing algorithms, and intuitive visualization platforms employed. Through qualitative and quantitative analysis of the literature, it is evident that while notable advancements have been made in digital-enabled crane safety management, these achievements remain largely confined to the experimentation stage. Consequently, a framework is proposed in this study to facilitate the practical implementation of digital-enabled crane safety management. Furthermore, recommendations for future research directions are presented. This comprehensive review offers valuable guidance for ensuring safe crane operations in the construction industry

Improving crane safety by agent-based dynamic motion planning using UWB real-time location system

The safe operation of cranes requires not only the experience of the operator, but also sufficient and appropriate support in real time. Due to the dynamic nature of construction sites, unexpected changes in the site layout may create new obstacles for the crane that can result in collisions and accidents. Limited research has been done on efficient re-planning for cranes with near real-time environment updating while considering communications between construction crews. To improve the safety of mobile crane operations and to provide more awareness on site, the present research proposes a near real-time monitoring and motion planning approach to improve crane safety on construction sites using an ultra wideband (UWB) real-time location system (RTLS) technology. In addition, an agent system framework is proposed to guide crane operators for safe crane operations by enhancing environment awareness and by providing intelligent re-planning. Location data are collected from tags attached to cranes and are processed by the agent system to identify the poses of dynamic objects, which is used to generate a new motion plan to guide the crane movement and thus to avoid potential collision. A motion planning algorithm, RRT-Con-Con-Mod, is proposed to efficiently generate safe and smooth paths for crane motions, mainly for the boom movement, while taking into account the engineering constraints and the path quality. A dynamic motion planning algorithm, DRRT-Con-Con-Mod, is proposed to ensure safety during the execution phase by quickly re-planning and avoiding collisions. In addition, an anytime algorithm is proposed to search for better solutions during a given time period by improving the path smoothness and by reducing the path execution time. The proposed algorithms are compared with other motion planning and re-planning algorithms. The results show that the proposed algorithms can quickly find a safe and smooth motion plan. Several tests of a UWB system have been applied in the laboratory and in indoor and outdoor environments to investigate the requirements of applying UWB on construction sites, that is, requirements including accuracy, visibility, scalability, and real-time. To satisfy these requirements, the configuration of the UWB system has been analyzed in detail to decide the sensors’ and tags’ locations and numbers based on heuristic rules. These tests show a good potential for using UWB tracking technology in construction sites by processing and organizing location data into useful information for near real-time environment updating. Furthermore, the framework of an agent system is proposed to integrate the proposed methodologies of motion planning and near real-time tracking. Different agents are created to represent the equipment, to coordinate tasks, and to update the site information. The functions of these agents include exchanging information, deciding priorities, etc. The current research will benefit the construction industry by providing more awareness of dynamic construction site conditions, a safer and more efficient work site, and more reliable decision support based on good communications

Capturing and Modeling a Three-Dimensional Stationary Noise Source Directivity Pattern with a Dynamic Array in the Near Field

The author has studied several legacy landmark methodologies to develop an original measurement technique. Spherical harmonics modeling practices were leveraged to accurately represent a source directivity pattern. In this thesis a lightweight microphone measurement array that was manually maneuvered around a static noise source was employed. The measurement technique consisted of inserting a head-tracker sensor onto the microphone array to allow the location of the captured acoustic Sound Pressure Level (SPL) to be investigated. By leveraging the historical methodologies the acoustic SPL and location data collected with this technique were processes to represent a directivity pattern of the compressor source chosen. The results indicated that the measurement technique is valid for capturing acoustic SPL and location data of a static noise source with a dynamic array. Propagation techniques yielded a ten decibel difference between the measured and predicated SPLs. The dynamic measurement technique and method for characterizing the three-dimensional acoustic directivity of a static noise source is further presented in this thesis

Modeling Construction Equipment in 4D Simulation and Application in VR Safety Training

Enhancing safety and productivity in construction sites is of principal importance, especially in congested sites. Scheduling and visualizing the construction progress in a Four-dimensional (4D) model with a high Level of Detail (LOD) are expected to improve safety, productivity, and constructability in construction sites. In spite of the large number of studies using Building Information Modeling (BIM) for visualization of the construction activities at the macro-level, these research works do not fully consider the scheduling and animating the equipment operations at the micro-level. This study aims to visualize the construction equipment activities to model the erection of a structure with prefabricated components along with other resources, such as workers and temporary equipment. The construction process is modeled in Fuzor Virtual Design and Construction (VDC) and the collision test is run to find the upcoming dangers. In addition, one of the areas where 4D can be used is for safety training. It is expected that the combination of 4D BIM with Virtual Reality (VR) improves the safety knowledge of construction workers, students, and equipment operators. Despite the large number of research works on the use of Three-dimensional (3D) VR in construction training, 4D VR is not sufficiently used for training purposes. This study aims to improve the safety knowledge of construction students by using a VR-based training approach. The specific objectives of the research are: (1) Identifying the requirements for construction equipment modeling and comparing the available commercial and research platforms in terms of visualizing, animating, and simulating equipment movements; (2) Animating and scheduling the construction processes at the micro-level in 4D BIM; and (3) Enhancing and evaluating the safety knowledge of construction management students in terms of Personal Protective Equipment (PPE) and equipment-related hazards using VR. In the first stage, the construction 4D context was developed and the safety scenarios about PPE- and equipment-related hazards were added. Secondly, construction students were given the initial VR-based training regarding hazard scenarios. Then, their safety knowledge was tested and they were asked to express their learning experience. The conclusions of this research are as follows: (1) When equipment tasks are visualized and scheduled at the micro-level in 4D BIM, the conflicts can be detected in advance and the cycle time of equipment can be determined, leading to the improvement of safety, productivity, and constructability in construction sites; (2) VR safety training improves hazard recognition of construction students since they can experience risky conditions in virtual construction sites; and (3) The capability of students in identifying equipment-related hazards would improve when they experience safety risks applied in 4D VR

Enabling the Development and Implementation of Digital Twins : Proceedings of the 20th International Conference on Construction Applications of Virtual Reality

Welcome to the 20th International Conference on Construction Applications of Virtual Reality (CONVR 2020). This year we are meeting on-line due to the current Coronavirus pandemic. The overarching theme for CONVR2020 is "Enabling the development and implementation of Digital Twins". CONVR is one of the world-leading conferences in the areas of virtual reality, augmented reality and building information modelling. Each year, more than 100 participants from all around the globe meet to discuss and exchange the latest developments and applications of virtual technologies in the architectural, engineering, construction and operation industry (AECO). The conference is also known for having a unique blend of participants from both academia and industry. This year, with all the difficulties of replicating a real face to face meetings, we are carefully planning the conference to ensure that all participants have a perfect experience. We have a group of leading keynote speakers from industry and academia who are covering up to date hot topics and are enthusiastic and keen to share their knowledge with you. CONVR participants are very loyal to the conference and have attended most of the editions over the last eighteen editions. This year we are welcoming numerous first timers and we aim to help them make the most of the conference by introducing them to other participants