Switching class labels to generate classification ensembles

Ensembles that combine the decisions of classifiers generated by using perturbed versions of the training set where the classes of the training examples are randomly switched can produce a significant error reduction, provided that large numbers of units and high class switching rates are used. The classifiers generated by this procedure have statistically uncorrelated errors in the training set. Hence, the ensembles they form exhibit a similar dependence of the training error on ensemble size, independently of the classification problem. In particular, for binary classification problems, the classification performance of the ensemble on the training data can be analysed in terms of a Bernoulli process. Experiments on several UCI datasets demonstrate the improvements in classification accuracy that can be obtained using these class-switching ensembles.     

Identification of semi-physical and black-box non-linear models: the case of MR-dampers for vehicles control

The topic of this paper is the identification of an accurate model for magneto-rheological (MR) dampers. A semi-active MR-damper is a dynamic system, where the inputs are the elongation velocity and the command current; the current is the control input which modulates at high-bandwidth the damping characteristic through the variation of a magnetic field. The output is the force delivered by the damper. Among the broad set of applications where MR-dampers can be used, the results proposed in this work refer to MR-dampers for the control of vehicle dynamics.MR-damper are highly non-linear systems, and their accurate modeling is a non-trivial task. MR-dampers can be modeled using two different model classes: semi-physical models and black-box models. Both approaches are considered in this work.The purpose of this brief paper is to make a concise but complete presentation and discussion of a non-trivial system identification problem. The problem considered herein is particularly interesting from the system identification point of view: from one side, the MR-damper is a very attractive actuator, which is likely to become the key device for many dynamics and vibration control systems in the near future; on the other side, it is an example of an application problem where the accurate modeling of the actuation device is one of the most crucial part of the whole control design problem.     

Structured coprime factor model reduction based on LMIs

In this paper we discuss dynamic model reduction methods which preserve a certain structure in the underlying system. Specifically, we consider the situation where the reduction must be consistent with a partition of the system states. This is motivated, for instance, in situations where state variables are associated with the topology of a networked system, and the reduction should preserve this. We build on the observation that imposing block structure to generalized controllability and observability gramians automatically yields such state-partitioned model reduction. The difficulty lies in ensuring feasibility of the resulting Lyapunov inequalities, which is in general very restrictive. To overcome this, we consider coprime factor model reduction. We derive an LMI characterization of expansive and contractive coprime factorizations that preserve structure, and use this to build a more flexible method for structured model reduction. An example is given to illustrate the method.     

A level-set based variational method for design and optimization of heterogeneous objects

A heterogeneous object is referred to as a solid object made of different constituent materials. The object is of a finite collection of regions of a set of prescribed material classes of continuously varying material properties. These properties have a discontinuous change across the interface of the material regions. In this paper, we propose a level-set based variational approach for the design of this class of heterogeneous objects. Central to the approach is a variational framework for a well-posed formulation of the design problem. In particular, we adapt the Mumford-Shah model which specifies that any point of the object belongs to either of two types: inside a material region of a well-defined gradient or on the boundary edges and surfaces of discontinuities. Furthermore, the set of discontinuities is represented implicitly, using a multi-phase level set model. This level-set based variational approach yields a computational system of coupled geometric evolution and diffusion partial differential equations. Promising features of the proposed method include strong regularity in the problem formulation and inherent capabilities of geometric and material modeling, yielding a common framework for optimization of the heterogeneous objects that incorporates dimension, shape, topology, and material properties. The proposed method is illustrated with several 2D examples of optimal design of multi-material structures and materials.     

On the development of a haptic system for rapid product development

This paper presents a system development that extends haptic modeling to a number of key aspects in product development. Since haptic modeling has been developed based on physical laws, it is anticipated that a natural link between the virtual world and practical applications can be established based on haptic interaction. In the proposed system, a haptic device is used as the central mechanism for reverse engineering, shape modeling, real time mechanical property analysis, machining tool path planning and coordinate measuring machine (CMM) tolerance inspection path planning. With all these features in a single haptic system, it is possible to construct a three dimensional part by either haptic shape modeling or reverse engineering, then performing real-time mechanical property analysis in which the stiffness of a part can be felt and intuitively evaluated by the user, or generating collision free cutter tool path and CMM tolerance inspection path. Due to the force feed back in all of the above activities, the product development process is more intuitive, efficient and user-friendly. A prototype system has been developed to demonstrate the proposed capabilities.     

Design automation for customized apparel products

This paper presents solution techniques for a three-dimensional Automatic Made-to-Measure scheme for apparel products. Freeform surface is adopted to represent the complex geometry models of apparel products. When designing the complex surface of an apparel product, abstractions are stored in conjunction with the models using a non-manifold data structure. Apparel products are essentially designed with reference to human body features, and thus share a common set of features as the human model. Therefore, the parametric feature-based modeling enables the automatic generation of fitted garments on differing body shapes. In our approach, different apparel products are each represented by a specific feature template preserving its individual characteristics and styling. When the specific feature template is encoded as the equivalent human body feature template, it automates the generation of made-to-measure apparel products. The encoding process is performed in 3D, which fundamentally solves the fitting problems of the 2D tailoring and pattern-making process. This paper gives an integrated solution scheme all above problems. In detail, a non-manifold data structure, a constructive design method, four freeform modification tools, and a detail template encoding/decoding method are developed for the design automation of customized apparel products.     

CAD tools for aesthetic engineering

The role of computers and of computer-aided design tools for the creation of geometrical shapes that will be judged primarily by aesthetic considerations is reviewed. Examples are the procedural generation of abstract geometrical sculpture or the shape optimization of constrained curves and surfaces with some global ‘cost’ functional. Different possibilities for such ‘beauty functionals’ are discussed. Moreover, rapid prototyping tools based on layered manufacturing now add a new dimension to the visualization of emerging designs. Finally, true interactivity of the CAD tools allows a more effective exploration of larger parts of the design space and can thereby result in an actual amplification of the creative process.     

3D virtual apparel design for industrial applications

The integration of physics-based models within CAD systems for garment design leads to highly accurate cloth shape results for virtual prototyping and quality evaluation tasks. To this aim, we present a physics-based system for virtual cloth design and simulation expressly conceived for design purposes. This environment should allow the designer to validate her/his style and design option through the analysis of garment virtual prototypes and simulation results in order to reduce the number and role of physical prototypes. Garment shapes are accurately predicted by including material properties and external interactions through a particle-based cloth model embedded in constrained Newtonian dynamics with collision management, extended to complex-shaped assembled and finished garments. Our model is incorporated within a 3D graphical environment, and includes operators monitoring the whole design process of apparel, e.g. panel sewing, button/dart insertion, multi-layered fabric composition, garment finishings, etc. Applications and case studies are considered, with analysis of CAD modelling phases and simulation results concerning several male and female garments.     

Tool path generation for clean-up machining by a curve-based approach

This paper presents a new efficient and robust tool-path generation method that employs a curve-based approach for clean-up machining. The clean-up machining discussed in this paper is pencil-cut and fillet-cut for a polyhedral model of the STL form with a ball-end mill. The pencil-cut and fillet-cut paths are obtained from the curve-based scanning tool paths on the xz, yz, and xy planes. The scanning tool path has exact sharp-concave points and bi-contact vectors, both of which are very useful to detect ‘pencil-points’, to trace the pencil-cut path, and to generate the fillet-cut path. In the paper, some illustrative examples are provided, and the characteristics of the proposed method are discussed.     

Maintaining associativity between form feature models

The promise of features technology was that the task domains would have access to task specific product data through feature based models. This is an important requirement in a distributed and concurrent design environment, where data of part geometry has to be shared between different task domains.Associativity between feature models implies the automatic updating of different feature models of a part after changes are made in one of its feature models. The proposed algorithm takes multiple feature models of a part as input and modifies other feature models to reflect the changes made to a feature in a feature model. The proposed algorithm updates feature volumes in other feature models and then classifies the updated volumes to obtain the updated feature model. The spatial arrangement of feature faces and adjacency relationship between features are used to isolate features in a view that are affected by the modification. Feature volumes are updated based on the classification of the feature volume of the modified feature with respect to feature volumes of the model being updated. The algorithm is capable of handling all types of feature modifications namely, feature deletion, feature creation, and changes to feature location and parameters. In contrast to current art in automatic updating of feature models, the proposed algorithm does not use an intermediate representation, does not re-interpret the feature model from a low level representation and handles interacting features. The present work considers modifications to form features only. Modification of constraints and application attributes are under investigation. Results of implementation on typical cases are presented.