Robert R. Lipman

Ladars for construction assessment and update

Work at the National Institute of Standards and Technology (NIST) on laser radar imaging of a construction site is described. The objective of the NIST research is to make measurements required in a construction project quicker and cheaper than current practice and to do so without impacting existing operations. This can be done by developing techniques for real-time assessment and documentation in terms of 3-D as-built models of the construction process. Once developed, this technology may be used for other applications such as condition assessment of a hazardous environment where human intervention would be impossible.

Using VRML in construction industry applications

This paper describes initial research using the Virtual Reality Modeling Language (VRML97) in construction industry applications. The modeling of steel structures and construction equipment as objects for inclusion in construction-site world models was studied. The ultimate goal is to provide three-dimensional web-based technologies for managing, accessing, and viewing construction project information.

The origin and characterization of conformational heterogeneity in adsorbed polymer layers

The equilibration of polymer conformations tends to be sluggish in polymer layers adsorbed onto highly attractive substrates, so the structure of these layers must be understood in terms of the layer growth process rather than equilibrium theory. Initially adsorbed chains adopt a highly flattened configuration while the chains which arrive later must adapt their configurations to the increasingly limited space available for adsorption. Thus, the chains adsorbed in the late stage of deposition are more tenuously attached to the surface. This type of non-equilibrium growth process is studied for polymethylmethacrylate (PMMA) adsorbed on oxidized silicon where the segmental attraction is strong (/segment) and for polystyrene (PS) adsorbed on oxidized silicon from a carbon tetrachloride solution where the segmental attraction is relatively weak (/segment). Measurements were based on Fourier transform infrared spectroscopy in attenuated total reflection (FTIR - ATR). In both cases, the chains arriving first adsorbed more tightly, became flattened (as measured by the dichroic ratio), and occupied a disproportionately large fraction of the surface. This non-uniform structure persisted indefinitely for the strongly adsorbed PMMA chains, while the PS chains exhibited a gradual evolution, presumably reflecting an equilibration of the adsorbed layer occurring after long times. On the theoretical side, the initial heterogeneity of these adsorbed polymer layers is modelled using a random sequential adsorption (RSA) model where the size of the adsorbing species is allowed to adapt to the surface space available at the time of adsorption. The inhomogeneity in the size of adsorbing species (hemispheres) in this model is similar to the distribution of chain contacts in our measurements on adsorbed polymer layers. Owing to extensive variance around the mean, conformations having the mean number of chain contacts are least probable, which contrasts starkly with expectations based on equilibrium adsorption theory.

Conformance checking of PMI representation in CAD model STEP data exchange files

Recommended practices supplement data exchange standards by providing common implementation guidance associated with specific requirements. ISO 10303 (STEP) product data exchange files that conform to recommended practices ensure interoperability between computer-aided design (CAD) systems and with downstream applications such as manufacturing and inspection. Correct implementation of product and manufacturing information (PMI)-annotations associated with a CAD models edges and faces such as geometric tolerances, dimensional tolerances, and datum features-in CAD authoring systems and translators is essential for interoperability. This paper discusses an approach implemented in a software tool for checking the conformance of STEP files to the recommended practice for PMI representation. Display Omitted Geometric and dimensional tolerances (PMI) are represented in STEP files.Correct implementation of PMI ensures interoperability with downstream applications.A software tool has been developed for conformance checking of PMI in STEP files.

Field Demonstration of Laser Scanning for Excavation Measurement

The use of a scanning laser to measure terrain changes due to excavation at a construction site is described. The objective at this phase of the project is to develop the tools necessary to measure terrain changes in real-time. This paper focuses on adaptations required to extend previously developed scanning procedures and post-processing algorithms for an indoor laboratory environment to a large outdoor area such as a construction site. The challenges encountered, techniques that worked or didn’t work, and lessons learned are discussed.

Mobile 3D Visualization for Construction

Until recently, visualization of 3D models required computational resources available only on desktop computers in office environments. With the advance of technology, it is now possible to visualize substantial 3D models on mobile handheld computers in the field. This paper discusses some of the current technology, discusses the use of the Virtual Reality Modeling Language on mobile handheld computers, shows several examples of 3D structural steelwork models visualized on a mobile handheld computer, and identifies some of the limitations imposed by current technology.

Investigating the Role of Geometric Dimensioning and Tolerancing in Additive Manufacturing

Additive manufacturing (AM) has increasingly gained attention in the last decade as a versatile manufacturing process for customized products. AM processes can create complex, freeform shapes while also introducing features, such as internal cavities and lattices. These complex geometries are either not feasible or very costly with traditional manufacturing processes. The geometric freedoms associated with AM create new challenges in maintaining and communicating dimensional and geometric accuracy of parts produced. This paper reviews the implications of AM processes on current geometric dimensioning and tolerancing (GD&T) practices, including specification standards, such as ASME Y14.5 and ISO 1101, and discusses challenges and possible solutions that lie ahead. Various issues highlighted in this paper are classified as (a) AM-driven specification issues and (b) specification issues highlighted by the capabilities of AM processes. AM-driven specification issues may include build direction, layer thickness, support structure related specification, and scan/track direction. Specification issues highlighted by the capabilities of AM processes may include region-based tolerances for complex freeform surfaces, tolerancing internal functional features, and tolerancing lattice and infills. We introduce methods to address these potential specification issues. Finally, we summarize potential impacts to upstream and downstream tolerancing steps, including tolerance analysis, tolerance transfer, and tolerance evaluation. [DOI: 10.1115/1.4031296]

Automated Earthmoving Status Determination

Efforts are underway at the National Institute of Standards and Technology (NIST) to develop automated non-intrusive production measurement systems and procedures for monitoring the status of general earthmoving operations at typical construction sites. The approach involves the use of autoregistered Lidar range sensing systems, wireless communications, high speed networking, temporal project databases, web-based data analysis and 3D user interfaces to provide useful derivative quantities to the earthmoving contractor while at the actual construction site. These same techniques may prove useful for planning and execution of remote, autonomous excavation on other planets. Present research is focused on developing methods for automated registration of independent 2-I/2D range data, automated volumetric calculations, including cut/fill requirements and amounts of raw material removed or placed, and web-based 3D site simulators which reflect the instant terrain geometry. This paper discusses the methods employed to achieve this capability and plans currently underway for daily construction monitoring at a

Model-Based Enterprise Summit Report

6M process plant in the spring of 2000.

Automating Robot Planning Using Product and Manufacturing Information

Abstract : This report summarizes the presentations, discussions, and recommendations from the Model-Based Enterprise Summit held at the National Institute of Standards and Technology in December of 2012. The purpose of the Summit was to identify challenges, research, implementation issues, and lessons learned in manufacturing and quality assurance where a digital three-dimensional (3D) model serves as the authoritative information source for all activities in a product s lifecycle. The report includes an overview of model-based engineering, technical challenges, summaries of the presentations given at the workshop, and conclusions that emerged from the presentations and discussions.