Terrence Fernando

Path planning in construction sites: performance evaluation of the Dijkstra, A∗, and GA search algorithms

Abstract This paper presents the application of path planning in construction sites according to multiple objectives. It quantitatively evaluates the performance of three optimisation algorithms namely: Dijkstra, A∗, and Genetic algorithms that are used to find multi-criteria paths in construction sites based on transportation and safety-related cost. During a construction project, site planners need to select paths for site operatives and vehicles, which are characterised by short distance, low risks and high visibility. These path evaluation criteria are combined using a multi-objective approach. The criteria can be optimised to present site planners with the shortest path, the safest path, the most visible path or a path that reflects a combination of short distance, low risk and high visibility. The accuracy of the path solutions and the time complexities of the optimisation algorithms are compared and critically analysed.

A constraint manager to support virtual maintainability

Virtual prototyping tools have already captivated the industrys interest as viable design tool. One of the key challenges for the research community is to extend the capabilities of Virtual Reality technology beyond its current scope of ergonomics and design reviews. The research presented in this paper is part of a larger research programme that aims to perform maintainability assessment on virtual prototypes. This paper discusses the design and implementation of a geometric constraint manager that has been designed to support physical realism and interactive assembly and disassembly tasks within virtual environments. The key techniques employed by the constraint manager are direct interaction, automatic constraint recognition, constraint satisfaction and constrained motion. Various optimization techniques have been implemented to achieve real-time interaction with large industrial models.

A simulation environment for construction site planning

This paper presents the design of a simulation environment for the modelling, visualisation and optimisation of construction site layouts. This construction site workspace application aims to support the site planning task by analysing space and risk on the site and generating automated site layouts which satisfy a combination of cost, efficiency and safety criteria. The construction site simulation environment forms part of an EU funded project called DIVERCITY (Distributed Virtual Workspace for enhancing Communication within the Construction Industry). This is concerned with the development of virtual simulation prototypes to support the client briefing, design review, and construction planning stages of the construction process. The site analysis module comprises a safety analysis component, a space analysis component, and an optimisation component. The safety analysis component is a generic model for the graphical and numerical representation of risk/hazard spaces. The space analysis component represents and classifies the various spaces on the construction site according to their relative importance in terms of accessibility and visibility. The optimisation component takes safety and space analysis information, and performs site layout optimisation according to travelling distance minimisation, risk minimisation, and space use maximisation criteria.

Software architecture for a constraint-based virtual environment

Virtual environment technology is now beginning to be recognised as a powerful design tool in industrial sectors such as Manufacturing, Process Engineering, Construction, Automotive and Aerospace industries. It offers the ability to visualise a design from different viewpoints by engineers from different design perspectives providing a powerful design analysis tool for supporting concurrent engineering philosophy. A common weakness of the current commercial virtual environments is the lack of efficient geometric constraint management facilities such as run-time constraint detection and the maintenance of constraint consistencies for supporting accurate part positioning and constrained 3D manipulations. The environments also need to be designed to support the user as they are completing their task. This paper describes the software architecture of a constraint-based virtual environment that supports interactive assembly of component parts, embedded within a task based environment that supports contextual help and allows for the structure of tasks to be easily altered for rapid prototyping.

The use of visual and auditory feedback for assembly task performance in a virtual environment

This paper presents our creation and evaluation of multi-modal interface for a virtual assembly environment. It involves implementing an assembly simulation environment with multi-sensory feedback (visual and auditory), and evaluating the effects of multi-modal feedback on assembly task performance. This virtual environment experimental platform brought together complex technologies such as constraint-based assembly simulation, optical motion tracking technology, and real-time 3D sound generation technology around a virtual reality workbench and a common software platform. A peg-in-a-hole and a Sener electronic box assembly tasks have been used as the task cases to perform human factor experiments, using sixteen subjects. Both objective performance data (task completion time, and human performance error rates) and subjective opinions (questionnaires) have been gathered from this experiment.

An Immersive Assembly and Maintenance Simulation Environment

This paper outlines the development of a virtual environment for constraint based assembly and maintenance task simulation and analysis of large scale mechanical products. It is important that allowance is made for maintenance activities during a products design phase to help reduce the lifetime operating costs of such large scale mechanical products. Unfortunately, current CAE systems do not support such assessment capabilities, with these issues typically being addressed using expensive and time consuming physical prototypes. The design and implementation of an immersive virtual prototyping environment for supporting the assessment of assemblability and maintainability of large scale mechanical products, along with its use as a maintenance training tool will be outlined. Procedures and environments for realistic component assembly, constraint recognition, automatic disassembly sequence generation, and maintenance review and training are presented. The simulation of maintenance operations allows for maintenance to be addressed early in the design stages. This reduces unforeseen problems creeping into the design as it progresses through its life cycle, consequently saving both time and money while improving product quality.

Investigating interaction in CAVE virtual environments

An experimental comparison of interaction in the real world and a CAVE virtual environment was carried out, varying interaction with and without virtual hands and comparing two manipulation tasks. The double-handed task was possible in the real world but nearly impossible in the VE, leading to changed behavior. The single-handed task showed more errors in the VE but few behavioral differences. Users encountered more errors in the CAVE condition without the virtual hand than with it, and few errors in the real world. Visual feedback caused many usability problems in both tasks. The implications for VE usability and virtual prototyping are discussed.

An efficient parallel collision detection algorithm for virtual prototype environments

The automatic recognition of geometric constraints in virtual assembly and maintenance operations relies in the determination of intersecting surfaces between virtual prototypes. This is a key challenge in many virtual prototype applications, where it is necessary to find collisions precisely and interactively. This paper presents an algorithm to determine intersecting surfaces at interactive speed in a virtual prototyping environment. The proposed algorithm is based on the overlapping axis-aligned bounding box (OAABB). The OAABB concept is used effectively to eliminate the number of surfaces that cannot intersect and improve performance. The algorithm also facilitates the implementation using parallel computing methods. OpenMP is used, taking advantage of shared memory multiple processors and reducing the overall time complexity of the collision detection algorithm. To achieve an efficient parallel simulation, it is necessary to provide an efficient load balancing scheme. Our experiences in parallelising the code to achieve a better work distribution are also described. Results show that the proposed collision detection achieves interactive rates in real industrial applications as desired.

Can virtual workspaces enhance team communication and collaboration in design review meetings

The development of software to facilitate collaborative working among project teams has been an active research area for the last two decades. However, the recent impetus in deploying Building Information Models (BIMs) in construction has brought teamwork to the forefront and, therefore, it is important to conduct an in-depth study as to how BIM could be complemented with advances in visualisation and interaction technology to enhance team communication and collaboration. Effective tools that bring critical data and stakeholders together to solve design challenges have the potential to produce optimised solutions, reduce the number of meetings, improve communication and, consequently, delivery times. This paper explores how virtual workspaces supported with advanced visualisation and interaction techniques can enhance team communication and collaboration. It explores the type of communication channels necessary for supporting team collaboration with the use of both public and private workspaces that are essential for supporting individual and team exploration. These features are then implemented and tested using a collaborative design scenario. This research shows that the implementation of direct and indirect communication channels within virtual workspaces can significantly enhance team communication and collaboration. Furthermore, it shows that the use of a private workspace can assist individuals to contribute creatively to team activities.

A Virtual Environment for the Design and Simulated Construction of Prefabricated Buildings

Abstract:The construction industry has acknowledged that its current working practices are in need of substantial improvements in quality and efficiency and has identified that computer modelling techniques and the use of prefabricated components can help reduce times, costs, and minimise defects and problems of on-site construction. This paper describes a virtual environment to support the design and construction processes of buildings from prefabricated components and the simulation of their construction sequence according to a project schedule. The design environment can import a library of 3-D models of prefabricated modules that can be used to interactively design a building. Using Microsoft Project, the construction schedule of the designed building can be altered, with this information feeding back to the construction simulation environment. Within this environment the order of construction can be visualised using virtual machines. Novel aspects of the system are that it provides a single 3-D environment where the user can construct their design with minimal user interaction through automatic constraint recognition and view the real-time simulation of the construction process within the environment. This takes this area of research a step forward from other systems that only allow the planner to view the construction at certain stages, and do not provide an animated view of the construction process.