Functional design method for improving safety and ergonomics of mechanical products

Robust geotechnical design of shield-driven tunnels

<div class="htmlview paragraph">The concept of product or system function is considered as described in the Taguchi System of Quality Engineering. The importance of transfer functions is also discussed and a review of conventional value analysis techniques is given. This paper proposes a combination of the principles of robust design and value methodology to enable on-target functionality and direct cost allocation early in the product development process. The discussion on integration of value analysis principles in robust design methodology is provided considering the six sigma environment.</div>

Geotechnical design considers different limit states of design. Conventional deterministic design methodology uses the factor of safety approach, while reliability-based design and robust design methodology use probability distribution and statistics of properties. In this study, different design methodologies were compared. Efficient probabilistic methods and optimization techniques such as the first-order reliability method and genetic algorithm were used to arrive at a robust and optimized design. Estimation of system reliability helps in attributing importance to both the limit states involved, simultaneously. In addition, a combination of random field theory with numerical modeling in the framework of the Monte Carlo simulation method and response surface method was used in considering spatial variability. In this way, the risk involved while using conventional deterministic design methodology is brought out; it is apparent from the larger foundation sizes obtained using reliability-based and robust design methodologies. This emphasizes the importance of considering the variability of soil and the robustness of design for critical structures using probabilistic methods.

This paper presents an integrated control-structure design methodology that is robust to parametric variations and its application to the design of combine header height control. Traditional design process of controlled multibody systems is sequential wherein the structural design is accomplished first followed by the control design. Such sequential process can only provide suboptimal overall design and yield a suboptimal performance. In this paper, a sensitivity based integrated robust optimal design (IROD) methodology is used to determine optimal structural parameters concurrently with a controller with an objective of improving header height control performance for a combine harvester. The problem is to control the height of the heavy header assembly at a constant distance above the rough terrain to maximize the yield and efficiency during harvesting. The design methodology is demonstrated by choosing the pivot location of the hydraulic actuator on the header as a structural design parameter concurrently with controller parameters. The design obtained with this methodology was compared with the sequential design for tracking performance and robustness. It is shown that the integrated design obtained from IROD yields better performance, lower control power, and improved robustness than the sequential method. It also allows for higher vehicle speed and lower operational cost.

Robust design methodologies to the adaptive cycle engine system performance: preliminary analysis

Firstly introduced as a prototyping process, additive manufacturing (AM) is being more and more considered as a fully-edged manufacturing process. The number of AM processes, along with the range of processed materials are expanding. AM has made manufacturable shapes that were too difficult (or even impossible) to manufacture with conventional technologies. This has promoted a shift in engineering design, from conventional design for manufacturing and assembly to design for additive manufacturing (DFAM). Research efforts into the DFAM field have been mostly dedicated to part's design, which is actually a requirement for a better industrial adoption. This has given rise to topologically optimized and/or latticed designs. However, since AM is also capable of manufacturing fully functional assemblies requiring a few or no assembly operations, there is a need for DFAM methodologies tackling product's development more holistically, and which are, therefore, dedicated to assembly design. Considering all the manufacturing issues related to AM of assembly-free mechanisms and available post-processing capabilities, this paper proposes a top-down assembly design methodology for AM in a proactive manner. Such an approach, can be seen as the beginning of a shift from conventional design for assembly (DFA) to a new paradigm. From a product's concept and a selected AM technology, the approach first provides assistance in the definition of the product architecture so that both functionality and successful manufacturing (including post-processing) are ensured. Particularly, build-orientation and downstream processes' characteristics are taken into account early in the design process. Secondly, for the functional flow (energy, material, signal) to be appropriately conveyed by the right amount of matter, the methodology provides guidance into how the components can be designed in a minimalism fashion leveraging the shape complexity afforded by AM. A mechanical assembly as case study is presented to illustrate the DFAM methodology. It is found that clearances and material (be it raw unprocessed material or support structures) within them plays a pivotal role in a successful assembly's design to be additively manufactured. In addition, the methodology for components' design proves to be an efficient alternative to topology optimization. Though, the approach can be extended by considering a strategy for part consolidation and the possibility to manufacture the assemblies with more than one AM process. As regards components' design, considering anisotropy can also improved the approach. Highlights Additive manufacturing is capable of printing fully functional assemblies without any assembly operations. It is found that Design For Additive Manufacturing is currently mainly focused on part's design. A process-independent, structured and systematic method for designing assembly-free mechanisms (for AM) is proposed. Build orientation and downstream processes (including post-processing capabilities) are taken into account early in the design process. A method - based on functional flows - for part's design in a minimalist fashion, is proposed.

System analysis and design is an engineering technique which is widely used in industrial projects to ensure a solution is reached which fulfills the requirements of the user. The same technique has been used in this research for the design and implementation of a cricket bowling system which has been designed with both existing technology and the requirements of players and coaches in mind. The structured analysis and design methodology has been teamed with an object oriented approach to provide a component based solution which includes a bowling machine able to recreate any common bowling delivery, a visualization to provide temporal and spatial information about the delivery and an independent user interface to ensure robustness. This papers looks in more detail at the design and analysis methodologies used to create this solution.

Machine learning-aided generative design methodology for a Martian regolith habitation shell

A giant oil field offshore has been developed to date using vertical and then horizontal wells drilled off-shore from wellhead platform towers. In order to reduce costs reducing the number of wells required to drain the reservoir with improving recovery, further development of the field was planned using extended-reach long horizontal wells with throws greater than 18,000 ft and measured depths greater than 25,000 ft with some wells exceeding 35,000 ft. This paper will discuss how to reach an integrated robust completion design methodology to maximize performance of these long horizontal wells. The methodology considers a combination of two essential designs; Lower completion design and Stimulation design. While the key objective of lower completion and stimulation designs has been to connect wells to reservoirs at their best performances with the most effective and economical way, productivity/injectivity from every foot of these long laterals as well as long term performance are the keys to successful well design and reservoir development strategy. The design methodology incorporates several constraints from reservoir such as heterogeneities in permeability, pressure and porosity, and uncertainties in those properties prediction including presence of faults/thief zones. The design methodology also incorporates the objective to be able to perform well surveillance, such as PLTs, as well as manageable installation of lower completion. The paper will give examples of application of this methodology in designing a10,000+ ft long limited-entry liner which facilitates bullhead high pressure – high rate stimulation – high acid concentration in order to place acid across the entire lateral and maximize stimulation effectiveness of every foot of the lateral. The paper will also discuss actual well performances of available long lateral wells along with lessons learned.

Robust design methodology (RDM) comprises systematic efforts to achieve insensitivity of products or processes to sources of unwanted variation. In this article, the literature is reviewed and practices that facilitate industrial use of RDM by providing concrete ideas to generate robust designs are identified. To date the literature has focused mainly on statistical techniques useful for creating robust designs, that is, solutions that are insensitive to sources of unwanted variation, while scope and overall framework have been less emphasised, causing an ambiguity in these respects. One practice identified for insensitivity to variation sources is to exploit non-linearities (between response and control factors) and interactions (between noise and control factors), and suitable tools for accomplishing this can be design of experiments or simulation techniques. As systematic RDM efforts are based on an awareness of variation and are beneficial in all design stages, the review also focuses on these two aspects of RDM.

PurposeThe generic design environment for a flexible printed‐circuit board assemblies (PCBA) remanufacturing cell contains four interrelated complex design domains. Mechanical design domains are really complex and the use of well‐proven mechanical product design methodologies does not help the designer. Hence, this paper aims to develop a generic systematic design methodology for a flexible PCBA remanufacturing cell.Design/methodology/approachThe study investigates the use of conventional mechanical product design techniques for the design of a flexible PCBA rework (remanufacturing) cell. It indicates problems and the weaknesses when conventional product design techniques are used for the development of flexible manufacturing systems (FMS). It then provides a new systematic mechanical design methodology for designing a flexible PCBA rework (remanufacturing) cell. The design methodology is intended to be generic in order to apply successfully to any FMS design.FindingsConventional product design methodology cannot be used directly for the design of a flexible PCBA remanufacturing cell. Hence, two design methodologies were developed: the generic FMS mechanical design methodology and a specific FMS design methodology for a PCBA rework cell. The first one was developed based on the tasks of the conventional product design process integrated with new design tools. The generic design methodology was then extended to obtain the second methodology for a PCBA rework cell design. Both of the methodologies were applied to a flexible PCBA rework cell design problem. Both design methodologies eliminated unusable design solutions at the early design stages of the conceptual design process and made the design process easier.Practical implicationsThe generic and specific design methodologies provide a better design environment, even for less specialized FMS designers.Originality/valueThe design methodologies may help for the commercialization of a flexible PCBA remanufacturing cell that may be used for SM rework and assembly.

A View on Design: The German Perspective

With the smart grid revolution, there is a growing interest in the use of power converters associated to LCL filters to interface between the main utility grid and loads or renewable energy sources. LCL filters are commonly used mainly due to their low cost and high filtering performances. To achieve these performances, it is necessary to meticulously pick out the LCL filter parameters, taking into account grid code requirements and grid configuration and/or conditions. Several methodologies for LCL filter design have been presented and discussed in the literature. The main goal of this paper is to propose a simple, robust and systematic design methodology for LCL filter parameter tuning. The considered design methodology is aimed to overcome the shortcomings of classical design methodologies, namely, stable operation under different grid configurations and conditions. Compared to previous works, the proposed design methodology allows the achievement of robust LCL filter design with regard to large grid impedance variations without the use of any damping method. Also, it takes into account accuracy of capacitor standard values and proposes a simple design method for the converter side inductor that avoids saturation problems. An example of LCL filter design is presented and discussed. The obtained filter parameters were firstly tested using a Matlab-Simulink software tool. After that, they were tested through the development of an experimental set-up. The obtained simulation and experimental results show the reliability and efficiency of the proposed design methodology.

A significant challenge in today's electronic design is designing complex, high-performance, “reliable” systems out of available components that are often “unreliable”, their behavior being affected by uncertainties or stochastic fluctuations. The problem is to guide the design process towards robustness, i.e., making the design insensitive to parameter variations. In this paper, we review design techniques, methodologies and tools that address robust design in the context of analog and mixed-signal integrated systems. Our analysis is organized in two areas: architectures and methodologies with supporting tools. Design approaches based on calibration techniques have been traditionally used to tune analog performance and meet the required specifications. Digitally-assisted and system-assisted design approaches build circuits that are tolerant to impaired analog components. We survey statistical modeling and optimization techniques that are instrumental to robust, hierarchical design of complex systems. Finally, we discuss platform-based design and contract-based design as viable frameworks for robust design methodologies and tools to be developed into a structured design flow.

Patient-derived xenograft (PDX) is a well-accepted experimental cancer model mimicking original patients in histo- & molecular pathology, as well as drug response. Mouse clinical trials (MCT) using PDX becomes increasingly prevalent in oncology research, yet the theory and methodology for trial design and analysis is underdeveloped. By analyzing tumor growths of 34081 PDX mice, we showed that majority of them can be satisfactorily modeled by exponential growth kinetics, based on which we derived a new drug response readout called the AUC ratio that is superior to the tumor growth inhibition (TGI) and its variants. We outlined a bootstrap algorithm to calculate its confidence interval, and showed that a 4:4 (4 mice in both treatment groups) or up design sharply increases measurement accuracy over the lesser design. Next, we introduce three approaches for drug evaluation and biomarker discovery in MCTs. In the end-point based analysis, we used a cohort of gastric PDXs to show a positive correlation between EGFR mRNA expression and cetuximab efficacy, in agreement with clinical trial results. We then used linear mixed models (LMMs) to describe MCTs as clustered longitudinal studies that capture the growth and drug response heterogeneities across PDXs and among mice within a PDX. Further, LMMs can separate prognostic and predictive biomarker effects, quantify response difference to a drug for multiple cancers, or efficacy difference of multiple drugs to a cohort of PDXs. Thirdly, we used additive frailty models to perform survival analysis on MCTs. We defined survival endpoints of PFS and OS in PDXs, and showed that hazard ratios can be more accurately estimated. We revealed an inherent connection between frailty and growth rate for PDXs. We performed computational simulations for the last two methods to show that statistical power improves tremendously with a 3:3 or up design. This work lays the foundation for rational design and analysis of PDX mouse clinical trials. Citation Format: Sheng Guo, Binchen Mao, Henry Q. Li. Theory and methodology for the design and analysis of PDX mouse clinical trials [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4534. doi:10.1158/1538-7445.AM2017-4534