Christiaan J.J. Paredis

Heterogeneous Teams of Modular Robots for Mapping and Exploration

In this article, we present the design of a team of heterogeneous, centimeter-scale robots that collaborate to map and explore unknown environments. The robots, called Millibots, are configured from modular components that include sonar and IR sensors, camera, communication, computation, and mobility modules. Robots with different configurations use their special capabilities collaboratively to accomplish a given task. For mapping and exploration with multiple robots, it is critical to know the relative positions of each robot with respect to the others. We have developed a novel localization system that uses sonar-based distance measurements to determine the positions of all the robots in the group. With their positions known, we use an occupancy grid Bayesian mapping algorithm to combine the sensor data from multiple robots with different sensing modalities. Finally, we present the results of several mapping experiments conducted by a user-guided team of five robots operating in a room containing multiple obstacles.

Kinematic Design of Serial Link Manipulators From Task Specifications

The Reconfigurable Modular Manipulator System (RMMS) consists of modular links and joints that can be assembled into many manipulator configurations. This capability allows the RMMS to be rapidly reconfigured to custom tailor it to specific tasks. An important issue related to the RMMS is the determination of the optimal manipulator configuration for a specific task. This article addresses the problem of mapping kinematic task specifications into a kinematic manipulator configuration. For the design of two-degrees-of-freedom (2- DOF) planar manipulators, an analytical solution is derived. Because analytical solutions become impractical for problems with more than two design parameters, we have also developed a numerical approach for the design of 6-DOF manipulators. The numerical procedure determines the Denavit-Hartenberg (D-H) parameters of a nonredundant manipulator with joint limits that can reach a set of specified positions/orientations in an environment that may include parallelepiped-shaped obstacles. Finally, this approach is demonstrated with a three- dimensional example for a 6-DOF manipulator

A rapidly deployable manipulator system

A rapidly deployable manipulator system combines the flexibility of reconfigurable modular hardware with modular programming tools, allowing the user to rapidly create a manipulator which is custom-tailored for a given task. This article describes two main aspects of such a system, namely, the reconfigurable modular manipulator system (RMMS) hardware and the corresponding control software.

Composable Models for Simulation-Based Design

This article introduces the concept of combining both form (CAD models) and behavior (simulation models) of mechatronic system components into component objects. By connecting these component objects to each other through their ports, designers can create both a system-level design description and a virtual prototype of the system. This virtual prototype, in turn, can provide immediate feedback about design decisions by evaluating whether the functional requirements are met in simulation. To achieve the composition of behavioral models, we introduce a port-based modeling paradigm. The port-based models are reconfigurable, so that the same physical component can be simulated at multiple levels of detail without having to modify the system-level model description. This allows the virtual prototype to evolve during the design process, and to achieve the accuracy required for the simulation experiments at each design stage. To maintain the consistency between the form and behavior of component objects, we introduce parametric relations between these two descriptions. In addition, we develop algorithms that determine the type and parameter values of the lower pair interaction models; these models depend on the form of both components that are interacting. This article presents the initial results of our approach. The discussion is limited to high-level system models consisting of components and lumped component interactions described by differential algebraic equations. Expanding these concepts to finite element models and distributed interactions is left for future research. Our composable simulation and design environment has been implemented as a distributed system in Java and C11, enabling multiple users to collaborate on the design of a single system. Our current implementation has been applied to a variety of systems ranging from consumer electronics to electrical train systems. We illustrate its functionality and use with a design scenario.

The Value of Using Imprecise Probabilities in Engineering Design

Engineering design decisions inherently are made under risk and uncertainty. The characterization of this uncertainty is an essential step in the decision process. In this paper, we consider imprecise probabilities (e.g., intervals of probabilities) to express explicitly the precision with which something is known. Imprecision can arise from fundamental indeterminacy in the available evidence or from incomplete characterizations of the available evidence and designers beliefs. The hypothesis is that, in engineering design decisions, it is valuable to explicitly represent this imprecision by using imprecise probabilities. This hypothesis is supported with a computational experiment in which a pressure vessel is designed using two approaches, both variations of utility-based decision making. In the first approach, the designer uses a purely probabilistic, precise best-fit normal distribution to represent uncertainty. In the second approach, the designer explicitly expresses the imprecision in the available information using a probability box, or p-box. When the imprecision is large, this p-box approach on average results in designs with expected utilities that are greater than those for designs created with the purely probabilistic approach, suggesting that there are design problems for which it is valuable to use imprecise probabilities.

Modeling and simulation methods for design of engineering systems

This article presents an overview of the state-of-the art in modeling and simulation, and studies to which extent current simulation technologies can effectively support the design process. For simulation-based design, modeling languages and simulation environments must take into account the special characteristics of the design process. For instance, languages should allow models to be easily updated and extended to accommodate the various analyses performed throughout the design process. Furthermore, the simulation software should be well integrated with the design tools so that designers and analysts with expertise in different domains can effectively collaborate on the design of complex artifacts. This review focuses in particular on modeling for design of multi-disciplinary engineering systems that combine continuous time and discrete time phenomena.

Multi-attribute utility analysis in set-based conceptual design

During conceptual design, engineers deal with incomplete product descriptions called design concepts. Engineers must compare these concepts in order to move towards the more desirable designs. However, comparisons are difficult because a single concept associates with numerous possible final design specifications, and any meaningful comparison of concepts must consider this range of possibilities. Consequently, the performance of a concept can only be characterized imprecisely. While standard multi-attribute utility theory is an accepted framework for making preference-based decisions between precisely characterized alternatives, it does not directly accommodate the analysis of imprecisely characterized alternatives. By extending uncertainty representations to model imprecision explicitly, it is possible to apply the principles of utility theory to such problems. However, this can lead to situations of indeterminacy, meaning that the decision maker is unable to identify a single concept as the most preferred. Under a set-based perspective and approach to design, a designer can work towards a single solution systematically despite indecision arising from imprecise characterizations of design concepts. Existing work in set-based design primarily focuses on feasibility conditions and single-attribute objectives, which are insufficient for most design problems. In this article, we combine the framework of multi-attribute utility theory, the perspective of set-based design, and the explicit mathematical representation of imprecision into a single approach to conceptual design. Each of the component theories is discussed, and their combined application developed. The approach is illustrated using the conceptual design of a fixed-ratio power transmission as an example. Additionally, important directions for future research are identified, with a particular focus on the process of modeling abstract design concepts.

A Port Ontology for Conceptual Design of Systems

During conceptual design of systems, the emphasis is on generating the system architecture: the configuration of sub-systems and the interactions between them. Ports, as locations of intended interaction, play an important role at this stage of design. They are convenient abstractions for representing the intended exchange of signals, energy or material; they can be applied at different levels of detail, across different energy domains, and to all aspects of design: form, function, and behavior. But to play this versatile role, ports need to be represented in an unambiguous yet flexible fashion, accommodating the differences in vocabulary and approach across different disciplines and perspectives. In this article, we introduce the semantic structure for such an unambiguous representation: a port ontology. The ontology formalizes the conceptualization of ports such that engineers and computer aided design applications can reason about component connections and interactions in system configuration. It defines ports in terms of form, function and behavior attributes and further includes axioms that can be used to support a variety of engineering design tasks, such as port refinement, port compatibility checking, and the instantiation of interaction models. A LEGO example is used to illustrate the ontology and its applications in conceptual design. @DOI: 10.1115/1.1778191#

Kinematic design of fault tolerant manipulators

Abstract This paper defines the property of kinematic fault tolerance and develops a general constructive proof of the existence of fault tolerant manipulators. After formulating the necessary and sufficient condition for fault tolerance, a planar manipulator with a minimal kinematic structure is designed. A generalization to spatial manipulators, using a numerical approach is formulated. Finally, it is shown how this approach enables us to solve the spatial design problem.

Multi-view modeling to support embedded systems engineering in SysML

Embedded systems engineering problems often involve many domains, each with their own experts and tools. To help these experts with analysis and decision making in their domain, it is desirable to present them with a view of the system that is tailored to their particular task. In this paper, a model integration framework is demonstrated to address issues associated with multi-view modeling. The Systems Modeling Language (OMG SysMLTM) is used as a general language to represent a common model for the system as well as the dependencies between the different domain-specific tools and languages. To maintain consistency between these domain-specific views, model transformations are defined that map the interdependent constructs to and from a common SysML model. The approach is illustrated bymeans of amechatronic design problem involving views in multiple domain-specific tools, namely EPLAN FluidTM (to create production ready layouts) and Modelica® (for dynamic system analysis).