John A. Horst

How task analysis can be used to derive and organize the knowledge for the control of autonomous vehicles

Abstract The real-time control system (RCS) methodology has evolved over a number of years as a technique to capture task knowledge and organize it in a framework conducive to implementation in computer control systems. The fundamental premise of this methodology is that the present state of the task activities sets the context that identifies the requirements for all the support processing. In particular, the task context at any time determines what is to be sensed in the world, what world model states are to be evaluated, which situations are to be analyzed, what plans should be invoked, and which behavior generation knowledge is to be accessed. This results in a methodology that concentrates first and foremost on the task definition. It starts with the definition of the task knowledge in the form of a decision tree that clearly represents the branching of tasks into layers of simpler and simpler subtask sequences. This task decomposition framework is then used to guide the search for and to emplace all of the additional knowledge. This paper explores this process in some detail, showing how this knowledge is represented in a task context-sensitive relationship that supports the very complex real-time processing the computer control systems will have to do.

Dimensional metrology interoperability and standardization in manufacturing systems

Dimensional metrology is an important part of any manufacturing system. It consists of distinct components and requires a large, diverse, and interconnected knowledge base. How to pass information seamlessly with minimal cost and minimal data loss between different components of a dimensional metrology system is a major issue that concerns software and hardware vendors, standards developers, and customers. This paper focuses on the four main elements of a dimensional metrology system: product definition, measurement process plan definition, measurement process execution, and analysis and reporting of quality data. The activities and software modules that are involved in these elements are discussed. Key issues that cause interoperability problems are identified. These issues are discussed as they relate to the current situation in dimensional metrology standards development. The STEP (ISO 10303) standards are the product of an international effort to achieve interoperability for manufacturing systems. Extending STEP is an appropriate way to solve the interoperability problem within dimensional metrology systems. Further development of STEP standards is proposed so that Geometric Dimensioning and Tolerancing (GD&T) information already available in STEP can be linked with manufacturing feature information, measurement technology, and measurement results. The proposed STEP data model is an attempt to provide a standard that will support automatic measurement process plan generation for in-process on-machine measurement. Some case studies are under way to test the model.

A knowledge-based inspection workstation

We are building an inspection workstation development environment to use as a testbed for understanding what types of knowledge, e.g. data, algorithms and processes, can increase the productivity of inspection operations. Inspection can be more efficient through reducing the need for fixturing, integrating the generation of process plans and their execution within the controller, and reducing the errors or data losses that occur by translating the models to different formats. The initial configuration of inspection systems can be less costly through the use of open architectures that are constructed from components. Key elements of our work include in-situ feature-based planning, vision-driven part pose estimation and software methods to facilitate construction of manufacturing controllers. These provide a rich environment in which to study the categories of knowledge that are useful in intelligent control of inspection workstations. This paper describes our vision, approach and preliminary results.

Precise Definition of Software Component Specifications

Abstract A set of generic specification categories is presented which can be used to comprehensively define any software component within a certain class. With these categories as a template, a specific set of formal specifications can be generated for each component. Specifications for a particular component (an algorithm that estimates the position and orientation of a physical object using visual sensing) have been defined in EXPRESS, an information modeling language. A few example natural language specifications are presented for this particular component.

Trajectory generation for an on-road autonomous vehicle

We describe an algorithm that generates a smooth trajectory (position, velocity, and acceleration at uniformly sampled instants of time) for a car-like vehicle autonomously navigating within the constraints of lanes in a road. The technique models both vehicle paths and lane segments as straight line segments and circular arcs for mathematical simplicity and elegance, which we contrast with cubic spline approaches. We develop the path in an idealized space, warp the path into real space and compute path length, generate a one-dimensional trajectory along the path length that achieves target speeds and positions, and finally, warp, translate, and rotate the one-dimensional trajectory points onto the path in real space. The algorithm moves a vehicle in lane safely and efficiently within speed and acceleration maximums. The algorithm functions in the context of other autonomous driving functions within a carefully designed vehicle control hierarchy.

Transient analysis of serial production lines with perishable products: Bernoulli reliability model

Manufacturing systems with perishable products are widely observed in practice (e.g., food industry, biochemical productions, battery and semiconductor manufacturing). In such systems, the quality of the product is highly affected by its exposure time while waiting for the next operation, i.e., the residence time of intermediate parts within the system. Such a time should be strictly limited in order to ensure the product usability. The parts that reach the maximum allowable residence time need to be scrapped, thus impeding the production. To achieve an efficient production, the time-dependent or transient analysis is important to uncover the underlying principles governing production operations. In this paper, a serial production line model with two Bernoulli reliability machines, a finite buffer and perishable products is presented to analyze the transient behavior of such systems. The analytical formulas are derived to evaluate transient performance, and structural properties are investigated to study the effect of system parameters. In addition, using the model, we address problems of settling time estimation and production control to demonstrate the importance of the proposed method for transient analysis.

A Hierarchical structure of key performance indicators for operation management and continuous improvement in production systems

Key performance indicators (KPIs) are critical for manufacturing operation management and continuous improvement (CI). In modern manufacturing systems, KPIs are defined as a set of metrics to reflect operation performance, such as efficiency, throughput, availability, from productivity, quality and maintenance perspectives. Through continuous monitoring and measurement of KPIs, meaningful quantification and identification of different aspects of operation activities can be obtained, which enable and direct CI efforts. A set of 34 KPIs has been introduced in ISO 22400. However, the KPIs in a manufacturing system are not independent, and they may have intrinsic mutual relationships. The goal of this paper is to introduce a multi-level structure for identification and analysis of KPIs and their intrinsic relationships in production systems. Specifically, through such a hierarchical structure, we define and layer KPIs into levels of basic KPIs, comprehensive KPIs and their supporting metrics, and use it to investigate the relationships and dependencies between KPIs. Such a study can provide a useful tool for manufacturing engineers and managers to measure and utilize KPIs for CI.

Component Specifications for Robotics Integration

Robotics researchers have been unable to capitalize easily on existing software components to speed up their development efforts and maximize their systems capabilities. A component-based approach for building the software for robotics systems can provide reuse and sharing abilities to the research community. The software engineering community has been studying reuse techniques for three decades. We present several results from those efforts that are applicable to the robotics software integration problem. We describe how to specify a software component so that a potential user may understand its capabilities and facilitate its application to his or her system. At the National Institute of Standards and Technology, we have developed a three-stage, component-specification approach. We illustrate this approach for a component that is relevant to robotics.

A motion control algorithm for a continuous mining machine based on a hierarchical Real-time Control System design methodology

The drive toward increased safety for coal miners has led to the development of computer-assisted methods of underground coal mining. The development of control architectures for the control of the movement of continuous mining machines (tramming control) is an important part of this overall effort. The tramming control algorithm design described is in concert with hierarchical architecture design principles developed at National Institute of Standards and Technology (NIST), referred to as the Real-time Control Systems (RCS) methodology. The algorithm design allows for the control of both cutting and free-space movement by a continuous mining machine and allows for a high degree of human operator interaction.

Model-Based Enterprise Summit Report

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.