Computational Design Synthesis: A Model-Based Approach for Complex Systems

The design of systems architectures often involve a combinatorial design-space made of technological and architectural choices. A complete or large exploration of this design space requires the use of a method to generate and evaluate design alternatives. This paper proposes an innovative approach for the design-space exploration of systems architectures. The SAMOA (System Architecture Model-based OptimizAtion) tool associated to the method is also introduced. The method permits to create a large number of various system architectures combining a set of possible components to address given system functions. The method relies on models that are used to represent the problem and the solutions and to evaluate architecture performances. An algorithm first synthesizes design alternatives (a physical architecture associated to a functional allocation) based on the functional architecture of the system, the system interfaces, a library of available components and user-defined design rules. Chains of components are sequentially added to an initially empty architecture until all functions are fulfilled. The design rules permit to guarantee the viability and validity of the chains of components and, consequently, of the generated architectures. The design space exploration is then performed in a smart way through the use of an evolutionary algorithm, the evolution mechanisms of which are specific to system architecting. Evaluation modules permit to assess the performances of alternatives based on the structure of the architecture model and the data embedded in the component models. These performances are used to select the best generated architectures considering constraints and quality metrics. This selection is based on the Pareto-dominance-based NSGA-II algorithm or, alternatively, on an interactive preference-based algorithm. Iterating over this evolution-evaluation-selection process permits to increase the quality of solutions and, thus, to highlight the regions of interest of the design-space which can be used as a base for further manual investigations. By using this method, the system designers have a larger confidence in the optimality of the adopted architecture than using a classical derivative approach as many more solutions are evaluated. Also, the method permits to quickly evaluate the trade-offs between the different considered criteria. Finally, the method can also be used to evaluate the impact of a technology on the system performances not only by a substituting a technology by another but also by adapting the architecture of the system.

Walking Trajectory Optimization With Rotation of the Feet for a Planar Bipedal Robot With Four-Bar Knees

The design of a knee joint is a key issue in robotics and biomechanics to improve the compatibility between prosthesis and human movements and to improve the bipedal robot performances. We propose a novel design for the knee joint of a planar bipedal robot, based on a four-bar linkage. The dynamic model of the planar bipedal robot is calculated. We design walking reference trajectories with double support phases, single supports with a flat contact of the foot in the ground and single support phases with rotation of the foot around the toe. During the double support phase, both feet rotate. This phase is ended by an impact on the ground of the toe of one foot, the other foot taking off. The single support phase is ended by an impact of the swing foot heel, the other foot keeping contact with the ground through its toe. For both gaits, the reference trajectories of the rotational joints are prescribed by polynomial functions in time. A parametric optimization problem is presented for the determination of the parameters corresponding to the optimal cyclic walking gaits. The main contribution of this paper is the design of a dynamical stable walking gait with double support phases with feet rotation, impacts and single support phases for this novel bipedal robot.

Toward the Use of Pareto Performance Solutions and Pareto Robustness Solutions for Multi-Objective Robust Optimization Problems

For Multi-Objective Robust Optimization Problem (MOROP), it is important to obtain design solutions that are both optimal and robust. To find these solutions, usually, the designer need to set a threshold of the variation of Performance Functions (PFs) before optimization, or add the effects of uncertainties on the original PFs to generate a new Pareto robust front. In this paper, we divide a MOROP into two Multi-Objective Optimization Problems (MOOPs). One is the original MOOP, another one is that we take the Robustness Functions (RFs), robust counterparts of the original PFs, as optimization objectives. After solving these two MOOPs separately, two sets of solutions come out, namely the Pareto Performance Solutions (PP) and the Pareto Robustness Solutions (PR). Make a further development on these two sets, we can get two types of solutions, namely the Pareto Robustness Solutions among the Pareto Performance Solutions (PR(PP)), and the Pareto Performance Solutions among the Pareto Robustness Solutions (PP(PR)). Further more, the intersection of PR(PP) and PP(PR) can represent the intersection of PR and PP well. Then the designer can choose good solutions by comparing the results of PR(PP) and PP(PR). Thanks to this method, we can find out the optimal and robust solutions without setting the threshold of the variation of PFs nor losing the initial Pareto front. Finally, an illustrative example highlights the contributions of the paper.

Recycling of Carbon Fiber: Identification of Bases for a Synergy Between Recyclers and Designers

In order to decrease both energy consumption and CO2 emissions, the automotive, aeronautics and aerospace industries aim at making lighter vehicles. To achieve this, composite materials provide good opportunities, ensuring high material properties and free definition of geometry. As an example, for cold applications, the use of carbon fiber/thermoset composites is ever increasing, in spite of a high fiber price. But in a global and eco-friendly approach, the major limitation for their use remains their potential recyclability. Recycling a composite means having a recycling technology available, getting a dismantle solution and an access for the product, and disposing identification plus selection possibilities to the materials. Thus, carbon fibers recovery (i.e. recycling and re-processing) would both help design engineers to balance energy efficiency and cost, and open new opportunities for developing second-life composites, dedicated to the manufacture of medium or low loaded parts (non-structural in many cases). A first section presents an overview of composite recycling possibilities. Indeed, environmentally and economically, composite incineration is not attractive (even with an energetic valorization), let-alone burying. Reuse and recycling thus remain the two most interesting options. Aeronautics offers a high potential in terms of fiber deposit. In southwest France, composites recycling will increase in terms of quantity due to dismantling platforms Tarmac (dedicated to civil aircraft applications) and P2P (for the disassembly of ballistic weapons). In addition, from a technical point of view, and even if end-of-life solutions for composites still remain under development, solvolysis (i.e. water under supercritical conditions) already offers the opportunity to recover carbon fibers. The resulting recyclate retains up to 90 percent of the fiber’s mechanical properties. A second part will explore the recycling to design issue (i.e. how recycling processes have to balance the previous aspects of the end-of-life proposal). The recycler clearly becomes a new supplier in the carbon fiber lifecycle, by revalorizing wastes with alternatives to burning. Moreover, increasing carbon fiber shelf life reduces its product life impact. Finally, promoting carbon fiber end-of-life would ensure to link aeronautics, automotive, and leisure and sports industries; but one can create demand for recycled reinforcement, by packaging it in useful and attractive forms for those end-users (e.g. pseudo-continuous fiber, felt, strips, bands, patches, etc.). These sections will be enlightened by several examples from collaborations between I2M and local industries.

Satisfying Piping Stress and Flexibility Requirements With the Implementation of Expansion Joints: Techno-Economical Optimization

There have been various attempts to deal with the optimization of solutions which involve expansion joints in piping systems where sufficient flexibility can’t be found using suitable pipe routing. The difficulty of piping designs which involve expansion joints is that they rely upon two engineering expertises: Pipe Flexibility and Stress Analysis on one side and Expansion Joint Design and Construction on the other. Arguably distinctively different, they have been looked upon as totally detached engineering disciplines and it is rarely that companies have two of these experts residing under the same roof. Pipe Stress Engineers basically relied on support form Expansion Joint Experts on “as required basis” and called upon their knowledge only when needed. Thus, we have the situation where knowledge related to the design and construction of expansion joints sits with expansion joints manufacturing companies, which are totally separate and often remote entities in the piping design process. Even so, the ever present demand for techno-economical optimizations, points us to the following observations. The “Traditional method”, where Pipe Stress Engineer defines on his own the requirements for expansion joints and describes them in the technical specification for purchasing is, or should be, a theme of the past. This approach may be used only as a first attempt in search for the solution, but given that it never heads in the direction of achieving optimal techno-economical results, needs to be upgraded with additional steps.

Design of a Hybrid Acoustic Device Based on Proof-Mass Actuators

The paper deals with the design of a device for sound reproduction to be fixed to a supporting surface. The device is made up of two different types of acoustic actuators based on different technologies that allow good sound reproduction in the range of frequencies from 20Hz to 20kHz. The generation of sound at high frequencies is demanded to a magnetostrictive actuator, while a more traditional magnetodynamics actuator is used to generate sound at low frequencies. The coupling between these two actuators leads to a device having small overall dimensions and high performance.

A Fluid-Structure Case Study in Simulation Lifecycle Management

This paper aims at presenting an approach to structuring interactions within product, through a graph, for simulation purposes. This approach has been developed for specific needs on Simulation Lifecycle Management (SLM) dedicated to aircraft engine development. The paper also illustrates the implementation of this approach on a case study which concerns a compressor design.

Design of a Series-Type Independently Controllable Transmission Mechanism

This study proposes a design of transmission mechanism which is referred to as a series-type independently controllable transmission (ICT). The series-type ICT is an alternative form of the parallel-types proposed in the former researches. The series-type ICT can serve as a continuously or an infinitely variable transmission mechanism, and it can also produce a required angular output velocity that can be independently manipulated by a controller and not affected by the angular velocity of the input shaft. The series-type ICT mechanism is composed of two planetary gear trains and two transmission-connecting members. Kinematic and dynamic characteristics of the ICT mechanism are analyzed and their analytical equations are derived for application in this study.

Robotic Solutions Applied to Production and Measurement of Marine Propellers

Over the past decades, robots have emerged as a valuable technological solution for multiple highly complex industrial processes, and the manufacture of marine propellers has not been an exception. Majority of the propellers being produced worldwide are custom-designed products aiming to satisfy each ship’s propulsion requirements. Such geometrical diversity is a considerable challenge when traditionally manual manufacturing processes like hand-grinding and polishing need to be automated. In several market-leading propeller manufacturers within Europe and Asia, industrial robots are being applied for widely diverse operations such as milling polystyrene blocks to make moulding patterns, grinding out the excess material in the blade surfaces, or polishing the complete propellers’ surface before their final verification. Propeller blades are customized products, formed by curved and warped surfaces, requiring minimum 5 axes to be smoothly polished, and this can be easily achieved with a robot cell where the CAD/CAM data coming from the individual design are directly translated into robotic parameters. While this solution has demonstrated to be perfectly capable to comply with the marine propellers finishing tolerances, which are internationally defined by ISO 484 standard rules [6], robotic solutions for propeller measurement have not been successfully implemented within this specific industry due to reasons like lack of accuracy and repeatability. This paper analyses the root causes behind this problem, identifying the calibration process, the cell alignment method and the tool positioning as the principal factors resulting in this low measuring repeatability. Findings explained by the authors are the outcome of several practical measuring tests made on real marine propellers within ABB and Fanuc robot cells. This paper concludes offering solutions to reduce the inaccuracies caused by the mentioned factors, and recommending what type of marine propellers are more suitable to be measured with industrial robots, on the basis of ISO 484 requirements for each customized design. Moreover, suggestions for further research on this specific measuring application are provided in the concluding chapter.