Profile Tolerances Modeling: A Unified Framework for Representing Geometric Variations for Line Profiles

Tolerance modeling is the most basic issue in Computer Aided Tolerancing (CAT). It will negatively influence the performance of subsequent activities such as tolerance analysis to a great extent if the resultant model cannot accurately represent variations in tolerance zone. According to ASME Y14.5M Standard [1], there is a class of profile tolerances for lines and surfaces which should also be interpreted correctly. Aim at this class of tolerances, the paper proposes a unified framework called DOFAS for representing them which composed of three parts: a basic DOF (Degrees of Freedom) model for interpreting geometric variations for profiles, an assessment method for filtering out and rejecting those profiles cannot be accurately represented and a split algorithm for splitting rejected profiles into sub profiles to make their variations interpretable. The scope of discussion in this paper is restricted to the line profiles; we will focus on the surface profiles in forthcoming papers. From the DOF model, two types of errors result from the rotations of the features are identified and formulized. One type of the errors is the result of the misalignment between profile boundary and tolerance zone boundary (noted as type 1); and if the feature itself exceeds the range of tolerance zone the other type of errors will form (noted as type 2). Specifically, it is required that the boundary points of the line profile should align with the corresponding boundary lines of the tolerance zone and an arbitrary point of the line profile should lie within the tolerance zone when line profile rotates in the tolerance zone. To make DOF model as accurate as possible, an assessment method and a split algorithm are developed to evaluate and eliminate these two type errors. It is clear that not all the line features carry the two type errors; as such the assessment method is used as a filter for checking and reserving such features that are consistent with the error conditions. In general, feature with simple geometry is error-free and selected by the filter whereas feature with complex geometry is rejected. According to the two type errors, two sub-procedures of the assessment process are introduced. The first one mathematically is a scheme of solving the maximum deviation of rotation trajectories of profile boundary, so as to neglect the type 1 error if it approaches to zero. The other one is to solve the maximum deviation of trajectories of all points of the feature: type 2 error can be ignored when the retrieved maximum deviation is not greater than prescribed threshold, so that the feature will always stay within the tolerance zone. For such features rejected by the filter which are inconsistent with the error conditions, the split algorithm, which is spread into the three cases of occurrence of type 1 error, occurrence of type 2 error and concurrence of two type errors, is developed to ease their errors. By utilizing and analyzing the geometric and kinematic properties of the feature, the split point is recognized and obtained accordingly. Two sub-features are retrieved from the split point and then substituted into the DOFAS framework recursively until all split features can be represented in desired resolution. The split algorithm is efficient and self-adapting lies in the fact that the rules applied can ensure high convergence rate and expected results. Finally, the implementation with two examples indicates that the DOFAS framework is capable of representing profile tolerances with enhanced accuracy thus supports the feasibility of the proposed approach.

New Prototype of the Two-Legged Robot CENTAUROB

The CENTAUROB is a mobile service robot which can operate in unstructured environments while always remain in a statically stable position. The special feature of this system is the use of two Stewart platforms as leg structures, providing high flexibility and maneuverability. By a special foot geometry (shape like a C), it has been possible for the first time to realize a walking biped which can even handle spiral staircases. In this paper, we present a new and advanced prototype of this system.

A Novel Magnetorheological Concentric Spiral-Flow Damper

In this article, a novel design of MR damper, concentric spiral flow MR damper, is proposed. It could improve the heat dissipation problem which is usually found in traditional MR damper. The proposed MR damper has a concentric spiral flow channel around the cylinder which not only separates coils from MR fluid, but also increases the length of flow channel in a fixed space. Experimental studies has been conducted to demonstrate the performance of the proposed MR damper, the result shows the MR damper generates the maximum damping force of 188 N without applying magnetic field and 1251 N when inputting 1.5 A at low frequency, which means the damper has high range of adjustable damping force. The CSF-damper can be used to systems or structures with low dynamic response.

Toward a Systematic Design Process for Apparel

This paper first provides a critical review of the literature regarding the contemporary apparel (product) design process, and then proposes a new apparel design process. Apparel is a general term for products which covers dress, skirt, etc. The new apparel design process applies a so-called systematic design approach well known to field of design. The systematic design approach classifies a design into four phases, namely, task classification, conceptual design, embodiment design, and detail design. The four phases are then tailored to apparel design. The new apparel design process is thus more rational and systematic. The paper uses a gown (a type of apparel) design as a case to illustrate the benefit of this new apparel design process, i.e., improved potentials to make apparel design more creative and efficient.

A Practical Algorithmic Approach Towards Multi-Modal Resource Constrained Multi-Project Scheduling Problems (MMRCMPSP)

The literature concerning resource constrained project scheduling problems (RCPSP) are mainly based on series or parallel schedule generation schemes with priority sequencing rules to resolve conflicts. Recently, these models have been extended for scheduling multi-modal RCPSP (MMRCPSP) where each activity has multiple possibilities to be performed thus providing decision managers a useful tool for manipulating resources and activities. Nonetheless, this further complicates the scheduling problem inflicted by increase of decision variables. Multiple heuristics have been proposed for this NP-hard problem. The main solution strategy adopted by such heuristics is a two loops decision strategy. Basically the problem is split between two parts where first part is conversion of MMRCPSP to RCPSP (mode fix) while second is finding feasible solution for a resource constrained project and is restricted to single project environments. This research aims on the development of scheduling heuristics, exploring the possibilities of scheduling MMRCPSP with parallel assignment of modes while sequencing the activities. The work addresses Multi-Mode Resource Constrained Multi-Project Scheduling Problem, (MMRCMPSP) by formulating a mathematical model that regards practical requirements of working systems. The algorithm is made intelligent and flexible in order to adopt and shift among various defined heuristic rules under different objectives to function as a decision support tool for managers.

Feature Model Approach for Managing Variablility of Dynamic Behavior Models in Mechatronic Systems

The design of mechatronic products requires cooperation and coordination of the involved disciplines. To analyze the dynamic behavior of the product’s subsystems and their components, multiple dynamic behavior models (DBM) are developed in different levels of detail (modeling depths) and domains. However, in order to simulate the complex interactions and dependencies between them, models of the whole system are needed, which fit the varying modeling objectives and analysis goals. These comprehensive models are often extensive and the manual construction presupposes deep insight in the specific model approaches and modeling tools. Furthermore, consistency needs to be ensured. The paper describes a way to automatically configure simulation models of the system adopting a Software Product Line (SPL) approach. With the use of feature models, SPL approach provides a structured method for managing variability. The particular focus of this paper is on handling of components in different tools with more than one level of detail through deployment of feature modeling. Also, it presents the concept of a multifunctional model client (MMC), which facilitates integration of solution and system knowledge.

Divergent Engineering

This is a position paper. Traditional engineering has focused on the design goal and all efforts have been paid to achieve design requirements and design specifications with the highest quality. Such engineering is indeed necessary to develop very high tech products or very sophisticated products. But on the other hand, there are needs for engineering which makes the most of the available resources. To borrow Theodore Roosevelt’s words, “Do what you can, with what you have, where you are” is the philosophy of such an approach. Current engineering is convergent engineering or tree-structured engineering. We invent or use many technologies to achieve our high goal. But if we look at the developing countries, local people are not capable of using such high sophisticated systems and what makes the matter worse, materials, etc. which are needed are not available locally. For them, what is more important is how they can utilize their own local materials or resources and develop a system which can be used and repaired by themselves. Thus, not only physical resources, but such resources as human, etc. must be considered how to utilize them in order to cater to their local needs. And in fact, if we are successful in developing such local products by utilizing their own local resources, it would increase employment and the market will grow up. In short, low-end to high-end industrial development can be expected. To achieve this, we need divergent engineering. An engineering to think how we can make the most of the resources at hand. The product thus developed may be low tech, but has quality and performance to satisfy the local needs enough. And it should be added that such low tech products would serve to cater to quickly aging society as well. Products that call for high capabilities cannot be used by seniors. So unless products are for a professional user, even in advanced countries, most of which are suffering from the problem of quick aging populations, very high tech and sophisticated products will not meet the aging customers’ needs or expectations. We need much simpler and intuitive engineering. Engineering is an activity to satisfy our dreams. But current convergent technology is too much stuck on the traditional path. Convergent engineering helps engineering going higher and higher, but it does not help it going wider and wider. It requires high expertise not only on the side of the producer, but also on the side of the customer. To expand engineering wider and wider, we need divergent engineering. This paper discussed the importance of divergent engineering and describes its importance with illustrative examples.

Development of Haptic-Enabled Virtual Reality Applications for Engineering, Medicine and Art

The technological growth in the last years have conducted to the development of virtual reality (VR) systems able to immerse the user into a three-dimensional (3D) virtual environment where the user can interact in real time with virtual objects. This interaction is mainly based on visualizing the virtual environment and objects. However, with the recent beginning of haptic systems, the interaction with the virtual world has been extended to also feel, touch and manipulate virtual objects. Virtual reality has been successfully used in the development of applications in different scientific areas ranging from basic sciences, social science, education and entertainment. On the other hand, the use of haptics has increased in the last decade in domains from sciences and engineering to art and entertainment. Despite many developments, there is still relatively little knowledge about the confluence of software, enabling hardware, visual and haptic representations, to enable the conditions that best provide for an immersive sensory environment to convey information about a particular subject domain. In this paper, the state of the art of the research work regarding virtual reality and haptic technologies carried out by the authors in the last years is presented. The aim is to evidence the potential use of these technologies to develop usable systems for analysis and simulation in different areas of knowledge. The development of three different systems in the areas of engineering, medicine and art is presented. In the area of engineering, a system for the planning, evaluation and training of assembly and manufacturing tasks has been developed. The system, named as HAMS (Haptic Assembly and Manufacturing System), is able to simulate assembly tasks of complex components with force feedback provided by the haptic device. On the other hand, in the area of medicine, a surgical simulator for planning and training orthognathic surgeries has been developed. The system, named as VOSS (Virtual Osteotomy Simulator System), allows the realization of virtual osteotomies with force feedback. Finally, in the area of art, an interactive cinema system for blind people has been developed. The system is able to play a 3D virtual movie for the blind user to listen to and touch by means of the haptic device. The development of these applications and the results obtained from these developments are presented and discussed in this paper.

Representation of Function, Behavior, Structure and Interrelationships at Different Abstract Levels of Product Information

To foster an effective collaboration during product lifecycle activities, product information must include data on geometry and topology, assembly constraints and associations, design and product processes, the functions and behaviors of the product, and the design intent. A product has many associations among its parts in terms of assembly, function, behavior, tolerance, kinematics, etc. These associations need to be represented in a consistent way, so that they will not conflict with each other. There have been many efforts to connect function and behavior to structure, but there exists no complete, consistent method yet. It is especially critical in the conceptual development of a product, as well as during its evaluation. The work described in this paper should help people make intelligent decisions by allowing them to manage product lifecycle activities from different perspectives (i.e., function, structure, etc.) using the knowledge of how the product information is interconnected, and how artifacts affect each other. In this study, functional and behavioral models have been developed to represent assembly-related product knowledge. These models connect functions, behaviors and structures — through the parts of artifacts using input/outputs and artifacts’ functional associations (i.e. spatial and design relations/requirements) at different abstract levels of product information. A planetary gearbox has been used as a case study to show how the functional/structural model can be implemented.