Virtual Reality System for the Evaluation of Complex Mechanical Systems

Modeling of friction forces has been a challenging task in mechanical engineering. Parameterized approaches for modeling friction find it difficult to achieve satisfactory performance due to the presence of nonlinearity and uncertainties in dynamical systems. This paper aims to develop adaptive fuzzy friction models by the use of data-mining techniques and system theory. Our main technical contributions are twofold: extraction of fuzzy rules and formulation of a static fuzzy friction model and adaptation of the fuzzy friction model by the use of the Lyapunov stability theory, which is associated with a control compensation of a typical motion dynamics. The proposed framework in this paper shows a successful application of adaptive data-mining techniques in engineering. A single-degree-of-freedom mechanical system is employed as an experimental model in simulation studies. Results demonstrate that our proposed fuzzy friction model has promise in the design of uncertain mechanical control systems.

The benefits of including aesthetic factors in the design of mechanical systems have been receiving increasing attention and study. Designs that successfully incorporate aesthetic considerations are more likely to create positive impressions in users, while offering increased usability and improved ergonomics. However, mechanical system design methods that successfully integrate the simultaneous evaluation of aesthetic factors with other parameters are not yet widely used. This paper presents a total design method that specifically includes aesthetic factors in the design process. The proposed method consists of three parts: (1) the analysis of the aesthetic factors; (2) the analysis of other factors (e.g. cost, function, mechanical characteristics, and so on); and (3) the evaluation of the overall system, using evaluation maps that include all system information. The use of evaluation maps allows other mechanical system factors to be treated concurrently with those of aesthetic importance. This method is applied to the design of a service robot that will offer a cup of beverage to a person.

Cohesive strength and fracture toughness of atmospheric ice

The analysis and design of mechanical structures and systems has a long and in-depth research history, and has achieved fruitful results. In fact, in the traditional analysis and design of mechanical structures and systems, people have found that there are a lot of uncertainties in the disciplines of system science, transportation science, and management science. It is difficult for traditional deterministic design methods to effectively deal with this type of problems. Uncertainty issues, such as the uncertainty of the shape and size of the structure due to the influence of processing technology, processing equipment, environmental factors and human factors in the manufacturing process, these inaccurate and uncertain information mainly come from the processing technology, Processing equipment, environmental factors, and man-made factors, and evidence theory can effectively model the problem of cognitive uncertainty in engineering, using probability intervals composed of credibility and likelihood to describe the cognitive uncertainty brought about by Impact. This article introduces the basic concepts of evidence theory and the basic process of reliability analysis of conventional evidence theory, and optimizes it to a certain extent. Then, this paper uses the optimization method and conventional methods of this paper to deal with a practical engineering problem, and compares the results. The final research results show that the optimization method in this paper is more effective than conventional methods, and it is concluded that the theory of evidence is indeed applicable to mechanical engineering, and it can effectively analyze the reliability of machinery.

991012632568403412 HKUST Electronic Theses Design and application of electrical resistivity and mechanical wave-based measurement systems for non-destructive process monitoring by Yuxin Wu thesis 2018 xviii, 152 pages : illustrations (chiefly color) ; 30 cm Non-destructive monitoring methods are very important…Read more ›

Product development is a process with complicated procedures, which incorporate many aspects of knowledge, experience and teamwork. Specifically, mechanical system design requires an iterative process to determine the desired component design parameters that would satisfy kinematic, performance and manufacturability requirements, which would result in an efficient and reliable operation of speed reduction units. This article describes an approach towards the development of intelligent design support environments for mechanical transmission systems, along with implementation details of a distributed knowledge-based gearing design and manufacturing system that is deployed over the Internet. The system embodies the various tasks of the design process, with modules that address: performance evaluation, process optimization, manufacturability analysis, and provides reasoning and decision-making capabilities for reducing the time between gear tooth creation, detailed design and final production. This methodology is highly desirable in that it is able to simulate real working conditions, evaluate and optimize the design effectively, prevent designers from time-consuming iterations and reduce long and expensive test phases. In an application example relating to process design of a forged gearing system, once a successful power rating is achieved within the design environment through FEA based techniques, the system automatically feeds input parameters into the manufacturing module which carries out all process design and planning stages. Estimation of the number of preforming stages, generation of detail die drawings, and forging load and energy requirements are calculated based on available material design databases, knowledge-based rules and feature-level calculations. Utilization of the World Wide Web, as a medium for the implementation of gear design and its agile manufacturing over the Internet is also being demonstrated. A combination of HTML, JavaScript, VRML, CGI Script and C++ based procedures is used to bring this capability to users distributed anywhere in the world. With the above developments, the problems of experience and expertise for the designers are overcome and unexpected design iterations that cause wastage of engineering time and effort, are avoided. The environment can be easily enhanced with other types of gearing systems.

<div class="htmlview paragraph">Effective computer-aided design of engineering systems requires comprehensive computer-application software that conveniently adapts to the particular engineering design considered. This paper discusses the theoretical background and initial experience with a program intended for computer-aided design of machine-like mechanical systems, and outlines the use of a time-shared graphic terminal for schematic display of program output. The program is applicable to three types of mechanical systems: linear and nonlinear unconstrained dynamic systems, kinematic systems (that is, constrained systems), and multifreedom, constrained systems.</div>

An integrated design method for a mechanical structure and controller using the Nash bargaining game is proposed. In this study, we describe how to apply the bargaining game model into the design of mechanical systems and show that optimized design parameters can be obtained from the strategy which maximizes the Nash product. The example application shown in this paper is the design of a single link flexible arm. In this sample design, the lowest natural frequency and the real part of the dominant pole of system with PD controller are considered as indices to optimize both the structure and controller. Results show that we can design a flexible arm with PD controller can be designed using this method.

Assistive devices of human knee joint: A review

The preparation of design notebooks by engineering students is discussed with reference to a required course for senior mechanical engineering students at Rensselaer called 'Design of Mechanical Systems'. The guidelines provided for the students at the beginning of the semester for preparing a design notebook of their work are presented. Experiences to date, covering approximately six semesters, with having the students prepare a design notebook are summarized. The students have trouble at the beginning of the semester filling in design notebooks. It is found out that students have trouble distinguishing between essential and non-essential facts. Faculty members find the notebook a useful tool to assess a student's contribution to the team effort. >

Carbon monoxide (CO), a highly toxic gas, is produced during the incomplete combustion of carbon-based fuels. In indoor environments, high CO concentrations constitute a serious occupational health hazard; this is especially true in the case of automotive repair shop (ARS) employees who are exposed on a daily basis to vehicle exhaust streams. The present study focuses on the experimental investigation and numerical simulation of CO production and dispersion inside an ARS facility. Detailed measurements of CO concentration, vehicle traffic and ventilation system velocities are performed; the obtained data are appropriately formulated to provide quantitative information for modelling purposes. A detailed Computational Fluid Dynamics simulation of the developing transient flow-field is performed. The numerical results are validated using the experimental data; an overall good qualitative and quantitative agreement is achieved. Aiming to improve the energy efficiency of the mechanical ventilation system, three alternative scenarios are investigated; it is shown that the utilization of a dynamic ventilation system may result in significant energy consumption benefits, while, at the same time, CO concentrations remain below the values suggested by current occupational health legislation. The obtained results may be utilized to assist the design of mechanical ventilation systems for ARS facilities.

Weight reduction is a recurring concern in the design of modern mechanical systems. This search may lead engineers to resort to using gears with holes in order to meet their requirements. This paper presents a methodology to carry out nonlinear dynamic analyses of a gear transmission with holes in the gear blanks subjected to a multiharmonic internal excitation. This work investigates the influence of these holes on the vibration levels, occurrence of contact loss and possible bifurcations. The numerical model features two flexible shafts coupled by a spur gear pair with holes. The gear model consists in two lumped masses and inertias and includes the gear backlash as well as the internal excitation sources that are the time-varying stiffness and the static transmission error (STE). The resulting mechanical system is solved in the frequency domain by the Harmonic Balance Method (HBM) coupled with an arc-length continuation algorithm and its stability is evaluated with Hill’s method. Results show that adding holes not only impacts the STE but also the mesh stiffness. The interactions of these two quantities has a substantial influence on the bifurcation structure along the main solution branch and leads to a decrease of the span of vibro-impact regions. As the applied static torque is increased, it is found that using holed gear blanks can effectively prevent contact loss and lead to a linear response.

This paper shows the early research findings of utilizing a virtual reality environment as an educational tool for the operation of a computerized numerical control (CNC) milling machine. Based off of previous work, the Advanced Virtual Machining Lab (AVML), this project features an environment in which a virtual CNC machine is fully operable, designed to allow STEM students and training professionals to learn the use of the CNC machine without the need to be in a physical lab. Users operate in the virtual environment using an immersive virtual reality headset (i.e. Oculus Rift) and standard input devices (i.e. mouse and keyboard), both of which combined make for easy movement and realistic visuals. On-screen tutorials allow users to learn about what they need to do to operate the machine without the need for outside instruction. While designing and perfecting this environment has been the primary focus of this project thus far, the research goal is to test the ease of use and the pedagogical effectiveness of the immersive technology as it relates to education in STEM fields. Initial usability studies for this environment featured students from a CAD/CAM-Theory and Advanced Applications (ME 54600) course at a Midwestern urban institution. Results from the study were tabulated with a survey using a four-point Likert scale and several open-ended questions. Findings from the survey indicated that the majority of users found the environment realistic and easy to navigate, in addition to finding the immersive technology to be beneficial. Many also indicated that they felt comfortable navigating the environment without the need for additional assistance from the survey proctors. Full details on the usability study, including data and discussion, can be found in this paper. The general consensus from the study was that, while some features needed refinement, the immersive environment helped them learn about the operation of a CNC machine. An additional comparative study will be undertaken to evaluate pedagogical effectiveness.

An application of fuzzy mathematical programming techniques to multiple objective design problems is presented. Two examples dealing with the multiobjective design of mechanical and structural systems are considered. The concept of a Pareto-optimal and fuzzy Pareto-optimal solution is discussed, and it is shown that the resulting formulation yields Pareto-optimal solutions. The fundamental assumption in fuzzy mathematical programming applications involving the use of linear membership functions is critically examined. Several nonlinear shapes for the membership functions of the fuzzy sets are proposed, consistent with varying perceptions of the designer, and are analyzed to determine their impact on the overall design process. These shapes correspond to what we define as the coefficient of membership satiation. It is seen that optimum designs for both examples are strongly influenced by the sign of the membership satiation coefficient.

In many locations mechanical ventilation has been the most widely used principle of ventilation over the last 50 years but the conventional system design must be revised to comply with future energy requirements. This paper examines the options and describes a concept for the design of mechanical ventilation systems with minimal pressure loss and minimal energy use. This can provide comfort ventilation and avoid overheating through increased ventilation and night cooling. Based on this concept, a test system was designed for a fictive office building and its performance was documented using building simulations that quantify fan power consumption, heating demand and indoor environmental conditions. The system was designed with minimal pressure loss in the duct system and heat exchanger. Also, it uses state-of-the-art components such as electrostatic precipitators, diffuse ceiling inlets and demand-control ventilation with static pressure set-point reset. All the equipment has been designed to minimize pressure losses and thereby the fan power needed to operate the system. The total pressure loss is 30–75 Pa depending on the operating conditions. The annual average specific fan power is 330 J/m3 of airflow rate. This corresponds to 10–15% of the power consumption for conventional mechanical ventilation systems thus enabling the system to fulfil future energy requirements in buildings.