Robert Sturges - Academia.edu (original) (raw)

Papers by Robert Sturges

Quasi-static wedging of three-point contacts is investigated, wherein the concepts of virtual and... more Quasi-static wedging of three-point contacts is investigated, wherein the concepts of virtual and redundant wedging due to a resultant force falling into a friction cone are proposed. We consider the fully-started case of a square peg and hole consisting of two point-surface contacts and one line-line contact. An analysis of the wedging diagram for this highly constrained configuration is carried out and compared to the two dimensional case. An approximate wedging diagram is constructed which shows that wedging of square pegs into square holes is more likely than cylindrical pees and holes of similar sizes.

Robotics and Computer-integrated Manufacturing, Jun 1, 1992

The technology of workholding is intimately related to the developing surface features of the par... more The technology of workholding is intimately related to the developing surface features of the parts to be held, the tooling systems which generate these surfaces, and the approaches appfied to grasp and secure the part. A rationale for workholding is developed which considers "single setup" as a desirable goal in the context of a machining FMS. A taxonomy of workholding methods is outlined with examples.

This paper addresses automatic assembly with passive rather than active compliant devices. Previo... more This paper addresses automatic assembly with passive rather than active compliant devices. Previous work has shown that in an ideal manufacturing environment three assembly primitives (prismatic insertions, threaded fits and general path insertions) exhibit a high level of difficulty. None of these are reliably assemblable under sensor-based force control or with an ordinary remote center compliance (RCC) device. In this paper, the authors extend the science of part mating and apply dexterity theory to synthesize a passive assembly device for precision fits of three-dimensional prismatic parts. This spatial remote center compliance (SRCC) obviates sensor-based and force control approaches to precision assembly of non-axisymmetric parts. >

Proceeding of Flexible Automation and Integrated Manufacturing 1999

<jats:title>Abstract</jats:title> <jats:p>This paper deals with the automated g... more <jats:title>Abstract</jats:title> <jats:p>This paper deals with the automated generation of stacking plans for bent sheet metal parts which are difficult to stack due to their irregular geometry. A stacking plan consists of a set of homogeneous transformations describing the configuration of each constituent part of the stack with respect to a world coordinate system. Stacks are constructed incrementally by adding parts to an existing stack. The base part is positioned to maximize stability when placed on a special part buffer. Successive parts are added in a configuration minimizing the height of the stack c.g. and ensuring the stability of the stack and the constituent parts. Evaluation of part and stack stability and analysis of part-part interference and part instability are addressed. Three examples demonstrate the advantage of interference analysis, handling of non-90° part orientations, and effect of features like asymmetric flanges and large holes on computational efficiency.</jats:p>

Volume 1: 21st Design Automation Conference, 1995

Human designers and optimization codes are very good at improving the performance of existing des... more Human designers and optimization codes are very good at improving the performance of existing designs, however, due to time and resource constraints, human designers tend to limit the range of alternative configurations considered. This paper presents a methodology, called Genetic Design (GD), to aid the designer by generating viable design alternatives. GD uses formal grammars for artifact description and representation, evaluates the artifacts automatically and manipulates the representations with genetic programming-like operations. GD can explore a wide breadth of the available design space, though at shallow depth, and presents alternatives to the human designer. The combination of GD’s ability to explore the design space and the human engineer’s ability to optimize existing configurations, promotes the production of viable, new design concepts by avoiding the inefficiencies associated with trial and error methods. This paper explores one application of GD: the design of simple...

In the design of material handling systems with complex and unpredictable dynamics, conventional ... more In the design of material handling systems with complex and unpredictable dynamics, conventional search and optimization approaches that are based only on performance measures offer little guarantee of robustness. Using evidence from research into complex systems, the use of behavior-based optimization is proposed, which takes advantage of observed relationships between complexity and optimality with respect to both performance and robustness. Based on theoretical complexity measures, particularly algorithmic complexity, several simple complexity measures are created. The relationships between these measures and both performance and robustness are examined, using a model of a directly connected material handling system as a backdrop. The fundamental causes of the relationships and their applicability in the proposed behavior-based optimization approach are discussed.

The need for concurrency in design and manufacturing is supported in a recently developed sheet m... more The need for concurrency in design and manufacturing is supported in a recently developed sheet metal design system by doing preliminary process design at the detail product design stage. This new “design with features” approach represents the evolving part form to the designer in multiple process domains and at multiple stages of a sequential process. Each pair of part form representations defines the conceptualized process which transforms it from one to the other. At this modelling level, processes are reversible so that design activity can take place in any of the domains and transferred to the others. We have fully implemented this concept in a sheet metal design/ manufacturing system in which preliminary process design occurs concurrently with product design and the normal representation ambiguities of wireframe and flat panel models are eliminated.

Volume 4: 3rd Design for Manufacturing Conference, 1998

Assembly sequences may require part grasp poses that differ from the implicit assembly insertion ... more Assembly sequences may require part grasp poses that differ from the implicit assembly insertion axis of RCC-type devices. Since favorable compliant responses accrue only for the insertion axis engineered into the RCC, such “off-axis” poses may obviate its use. The fundamental issue is the creation of an effective compliance that is isotropic in a plane normal to the insertion axis, irrespective of the location of the mechanism. This paper addresses the design of alternative compliant devices, especially an RRR spherical mechanism suitable for industrial application. General compliance requirements are established, mechanism kinematics are developed, and design equations are presented. A laboratory model is described that embodies the desireable features of zero friction, zero backlash, and isotropic stiffness for off-axis assembly tasks.

HEDL is developing automated fabrication equipment for fast reactor fuel. A major inspection oper... more HEDL is developing automated fabrication equipment for fast reactor fuel. A major inspection operation in the process is the gaging of fuel pellets. A key element in the system has been the development of a handling system that reliably moves pellets at the rate of three per second without product damage or excessive equipment wear.

Journal of Manufacturing Science and Engineering, 1992

This paper discusses an approach to monitoring cutting tool/part interactions in milling processe... more This paper discusses an approach to monitoring cutting tool/part interactions in milling processes using processed acoustic emission (AE) signals and the combined geometric aspects of the tool and the part. The expected events marking interactions of the tool edge with respect to the part during a cut are computed from a priori knowledge of tool and part geometry. Each event period is characterized by its timing and expected AE spectrogram. During cutting, AE signals are periodically converted to spectrograms to determine the peak signal frequency band. This band then defines a bandpass filter through which AE signals pass in real time, reporting the levels and event times of the actual process. Comparison of expected and actual event times and levels forms the basis for a continuous on-line tool/part interaction monitor which detects workholder failure and certain tool failure conditions.

Complex Systems, 2013

Behavior-based optimization is proposed to take advantage of relationships between complexity and... more Behavior-based optimization is proposed to take advantage of relationships between complexity and optimality with respect to both performance and robustness. Two dynamic measures are presented: logical and state complexities in the case of naval weapons elevator design. Logical complexity measure is defined as the ratio of the length of the logical evolution to the temporal evolution length, while state complexity is the measure identifying the number of unique states in an evolution. A system with more complexity is found to result in an increase of throughput.

<jats:title>Abstract</jats:title> <jats:p>Components with subtle asymmetry requ... more <jats:title>Abstract</jats:title> <jats:p>Components with subtle asymmetry require more handling time in manual and automatic assembly. Models of assembly processes predict that almost half of the acquisition effort derives from the recognition of feature subtlety and the symmetries of the part. An algorithm is presented which detects and evaluates the axes of symmetry and partial symmetry for a wide variety of asymmetries, features, and aspect ratios. The orientations of the partial symmetry axes are then used to calculate the effect on assembly time. The ability to locate axes in an object that are not orthogonal is demonstrated. Currently the algorithm can only examine 2-D shapes, and an approach to fully automated evaluation of a 3-D object is presented.</jats:p>

Volume 3: 5th Design for Manufacturing Conference, 2000

This work concentrates on a common assembly primitive, threaded fastener insertion, in an effort ... more This work concentrates on a common assembly primitive, threaded fastener insertion, in an effort to determine the nature of contact between a bolt and nut during thread mating. Contact state models were created to constrain the motion of the bolt at 1 and 2-point contacts. By analyzing the depth of intersection of the bolt into the nut as well as the vertical movement of the origin of the bolt reference frame, we determined that there are three types of contacts states present: unstable two-point, quasi-stable two-point, stable three point. Though the unstable case remains to be deciphered, the parametric equations derived in this work can be used without modification to create a full spectrum of maps at any point in the history of a threaded assembly problem. We investigated 81 potential orientations, each of which has its own set of contact points. From this exhaustive examination, we are capable of detailing a contact state history and, from this, have the potential to develop a ...

<jats:title>Abstract</jats:title> <jats:p>Recent concern for the environment ha... more <jats:title>Abstract</jats:title> <jats:p>Recent concern for the environment has caused growing attention to recycling, both using recycled materials to make products and recycling products after use. Although environmentalists may be eager to buy recycled/recyclable products, other consumers may not be so easily convinced. It may also be difficult to convince manufacturers that it is beneficial to develop green products. This paper supports a joint project between engineering and marketing disciplines to determine the cost and value of an environmentally designed product. Specifically, this paper evaluates the resources spent to manufacture a green videocassette in comparison with a standard videocassette by performing a resource analysis. This analysis estimates the cost, time and energy necessary to produce both videocassettes. This paper also compares the value of the videocassettes in terms of performance and physical attributes.</jats:p>

Fast moving technologies have caused high-tech components to have shortened life cycles, renderin... more Fast moving technologies have caused high-tech components to have shortened life cycles, rendering them obsolete quickly. Technology obsolescence creates significant problems for product sectors that use components that are only available for a short period of time for manufacture and maintenance of long field-life systems. Technology obsolescence can make design changes of systems prohibitively expensive, and results in high life cycle costs of systems. While the impact and pervasiveness of obsolescence problems are growing, existing tools and solutions are lacking the needed information and knowledge to do much more than focus on reactively managing obsolescence. Current methods and tools are limited by data conflicts and data inexplicitness, incompleteness, and inconsistency. In response to the drawbacks of current tools, comprehensive knowledge representation that allows information sharing, reuse, and collaboration on obsolescence issues across different organizations is requir...

Volume 4: 4th Design for Manufacturing Conference, Sep 12, 1999

ASME 1999 Design Engineering Technical Conferences, Sep 12, 1999