Schoenflies ( X ) motion is a 4D displacement Lie group including a spatial translation and any rotation whose axis is parallel to a given direction. Delassus parallelogram has four parallel screw (H) pairs with related pitches and the isosceles triangle is a special HHHP. After merging these two chains, an HHH-//-HHH generator of 2-DoF translation along a right helicoid is derived. It produces a 2-DoF motion mathematically modeled by a 2D submanifold of a 4D group of X -motion. Because of the product closure in an X -group, the 4-DoF generator with HHH-//-HHH loop serving as a subchain is revealed by adding two H pairs with axes parallel to fixed H axes. Parallel arrangement of two generators of the same X motion results in a new Schoenflies-motion manipulator with hybrid topology for 4-DoF pick-and-place operations. Four fixed H pairs (two double Hs) can actuate this manipulator and the two coaxial Hs must have distinct pitches. In addition, the possible design choices of special architectures are introduced for practical applications. Computer simulations of the new parallel manipulator with Schoenflies motion verify the effectiveness.

Generally product lifecycle management (PLM) is characterized as an integrated management process of product information and related processes across the product lifecycle. PLM affects development time of product and optimize the cooperation of all components of the development process of products. Therefore attention has to be paid to this fact in production and research. Processes across the entire product lifecycle management are complex and it is difficult to support various levels of cooperation. It is necessary to identify technological solutions to facilitate the implementation of PLM systems into processes of product life cycle. In the paper is presented derivation of technology solutions for PLM (product lifecycle information modeling and management, product lifecycle knowledge management, design chain management, product lifecycle process management, product trade exchange, collaborative product service and product lifecycle portal for stakeholder, developer, customer, manufacturer and supplier) and applications of advanced information technologies for implementation of PLM. In the paper is also described the technological solution which was developed to meet industrial requirements and obtain long term sustainability in today’s highly competitive market. Currently, still only a few small and medium-sized enterprises (SMEs) uses real benefits that PLM offers. The small and medium-sized enterprises also try to implement those technologies but, despite their flexibility, they have difficulties in structuring and exchanging information. Enterprises also have problems in creating data models for structuring and sharing product information, especially in the context of extended enterprises. It is caused by several factors that may have information, technical and financial character. Article refers and highlights the benefits that PLM brings by extension of PLM into so called “Closed-Loop Lifecycle Management (CL2M)”. It also describes the major barriers to the implementation of PLM in SME and propose possible solutions.

This paper presents an activity concerning a theoretical/experimental analysis of a new measurement system of the chain strength functional for the control of the electrically assisted bicycles. Such systems are characterized by a driving torque due to the contribution of an electric motor and of the rider. The electrical assistance is commonly regulated taking into account informations such as chain ring rotation, bicycle speed and/or the torque given by the rider. As a consequence, suitable measurements have to be made on board in order to handle the assistance performances and to improve drivability.

Based on the Bennett 4R chain, we construct a rotating loop by fixing one R axis to the frame and the fixed R becomes a coaxial double R pair. The R pair opposite to the fixed double R is replaced by a spherical S pair which can be equivalent to a (RRR) open chain with non-coplanar intersecting axes. In the (RRR) sub-chain, we choose special axes and derive R |- R |( R(R R R)R chain moving with 2 DoFs. That moving R becomes a coaxial double R with the addition of another rigid body and the obtained chain with hybrid topology generates a 3-dof motion, which is mathematically modeled by a 3D submanifold of a 4D group of X motions. Because of the product closure in an X -motion group, adding an H pair with any pitch and an axis parallel to the fixed R axis leads to a mechanical generator of a 4D X -motion group. Then, parallel arrangement of two generators of the same X motion gives a new parallel generator of X motion, which can be actuated by four fixed R pairs; the two Hs must have distinct pitches. A special design with four collinear actuated axes is revealed too.

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.

The human middle ear includes the tympanic membrane and the ossicular chain. The finite element method is capable of representing the complex geometry and the material orthotropy of the tympanic membrane. On the contrary, the ossicles can be considered as rigid bodies and a multi-body approach can be adopted. In the present study a multi-body model of the ossicular chain and other structures (joints, ligaments and muscle tendons) of the middle ear was developed and combined with a finite element model of the tympanic membrane through a feedback control strategy. An optimization procedure was used to calibrate unspecified or uncertain parameters with the aim of reproducing ascertained experimental literature data. The sensitivity of the calibrated models to both tympanic membrane and ossicular chain parameters was investigated. Material, geometrical and inertial parameters were considered, in particular those whose values were most widespread in the literature.

Grinding is always one of the most significant processes in manufacturing sector due to its high precision and accuracy and especially nowadays where the demand for higher quality products has been raised. Its importance lies on the fact that it stands at the final stages of a component’s manufacturing chain and therefore, the possibility of errors must be at the lowest levels. Heretofore, the improvement of this process has motivated a number of researchers to develop different techniques. In the current work a novel method of vibration-assisted surface grinding of mild and hardened steel using aluminium oxide grinding wheels is examined. More specifically, the design concept along with the dynamic characteristics of a simplified vibrating jig is presented. The purpose of this jig was to accommodate and oscillate the workpiece at a certain frequency during surface grinding in order to improve the performance of the process in terms of achieving lower grinding forces and thus lower power consumption, higher material removal rates and better product surface finish. Two grinding wheels and two workpiece materials with different properties were employed during conventional and vibration-assisted surface grinding and the results are compared. The benefits of this non-conventional, advanced grinding process are also illustrated.

The paper describes a new kind of solar tracker intended to satisfy the precision requirements of high concentration photovoltaic systems. The tracker is designed according to a Delta type parallel kinematic schematics. The paper describes the kinematic schematics, the sensor chain and the control algorithm. Finally results obtained in functional tests are shown.

Often a designer has the problem to apply a suitable system of geometrical and dimensional tolerances to an assembly. The right solution is not unique, in fact it depends on the chosen parameters. If the tolerances have to be optimized, some important parameters have to be taken into account, e.g. the efficiency of each prescription, or if this last is reachable, or it can be verified and how much the realization costs. The authors opinion is that a statistical approach based on the Monte Carlo Method is very useful when the tolerances chains are complex. This paper shows an application of this method in order to verify the functional alignment between two assemblies and a critical analysis of the uncertainty in phase both of the component design and test. This study has been developed thanks to the strict requirements imposed by ESA (European Space Agency) on the components that Thales Alenia Space has to realize within the LISA Pathfinder experiment. The very critical aspect of this work is to reciprocally align two cylindrical elements of two different assemblies. The specifications require 100 μm as maximum linear displacement and 300 μrad as maximum angular displacement. Moreover this prescriptions have to be verified also when the two elements are independently moving. To be able to reach such strict accuracy level the components have been assembled in an ISO 100 class cleanroom and the work space was a 3D Coordinate-Measuring Machine (CMM). The cylindrical elements have a 10 mm diameter, so the value of the measurement uncertainty associated with the alignment check is fundamental. Starting from the different uncertainty sources, the measurability and verifiability of the alignment have been considered and evaluated. The overall uncertainty has been assessed by numerical simulations which have taken into account the dimensional, geometrical and form tolerances as well as the instrumental uncertainty of the 3D CMM. This estimation has been positively validated by a session of repeated measurements. Numerical simulations have also allowed performing a sensitivity analysis, in order to give information about which sources more contribute to the overall uncertainty.

In mechanical assemblies, the performance, quality, cost and assemblability of the product are significantly affected by the geometric errors of the parts. This paper develops the statistical error analysis approach for dimensional control in automotive body multi-station assembly process. In this method, the homogeneous transformation matrices are used to describe the location and orientation of part and assembly features and the small homogeneous transformation matrices are used to model the errors. In this approach, the effective errors in automotive body assembly process are classified in three categories: manufacturing errors (dimensional and geometric tolerances), locating errors (fixture errors) and process errors (joining errors). In a mechanical assembly, small variations due the errors propagate according to a complex mechanism that in this approach it formulated in error analysis procedure. The propagation chain of geometric errors is described based on CAD models. The estimation of the error accumulation and the percent contributions of individual errors are based on the statistical model (root-sum-square method). The application of the proposed method is illustrated through presenting an example problem.

Product Life Cycle Management (PLM) is a system that integrates computerized tools and methodologies for managing the engineering knowledge and information that defines products. The PLM approach covers all the stages of the product lifecycle, beginning with the initial concept definition and including requirement characterization, detailed design, analyses and simulations, transition from development to production, production planning, production, maintenance and end of life. PLM tools support design processes distributed among decentralized development groups, as well as knowledge and information management within and outside the organization, including suppliers, clients and business partners. As in ERP, which supports the supply chain and management of the organization’s operations, assets and resources, PLM supports the product definition information chain and management of the organization’s intellectual property (IP). PLM systems comprise the following main and tightly integrated components: • Systems engineering and requirement management tools; • CAD tools for defining the digital product; • Product data and engineering processes management – PDM; • Digital manufacturing system, including design and simulation of production lines. Integrating PLM into the management system can shorten time-to-market, reduce expenses, improve quality and encourage innovation and creativity in developing products and planning production and service processes. The paper describes the principles and components of the PLM approach and presents a case study involving a PLM implementation at Boeing and Airbus. The case study describes the design and digital manufacturing of the Airbus A380 and the Boeing 787 aircraft. Both companies used similar tools in the PLM environment. At the time of the study (2006), Airbus used Dassault Catia V4 and Catia V5 with the Enovia PLM system, while Boeing used Dassault Catia V5 with Enovia. Major differences were found in system implementation, engineering process definitions and management methods, leading to entirely different results. The main differences in the implementations at Boeing and at Airbus were as follows: • In both cases, the engineering project and the business environment were extremely complex. At Airbus, design and production took place in four different countries at 16 different sites, with 41,000 employees. At Boeing, 6,000 engineers at 135 sites designed the plane, with 300 major suppliers; • In the case of Airbus, because of CAD system incompatibility changes in the design of the electrical wiring harnesses caused the harnesses not to fit the airplane body. The digital prototype was not updated with all the changes, and the lack of fit was only discovered at the stage of the actual physical assembly; • Boeing laid down strict rules during the design process to ensure that the information was complete and up to date. At Boeing, all those involved in development and production were obligated to work with one central data base, which was updated at least twice a week by all participants; • Airbus reported major losses and delays in supplying the planes, while Boeing reported high profits and shorter time-to-market. Airbus reported a loss of 6 billion dollars and a two-year delay in supplying the A380. Boeing, in contrast, reported a savings of 2 billion dollars and a reduction of 12 months in the timetable for supplying the 787. The use of PLM in the above examples leads to the following conclusions: • The design of major engineering processes (i.e. change process) is a critical success factor to PLM implementation; • Digital information must be compatible among the various CAD systems in the entire design chain; • All participants in the design and supply chain must impose and enforce engineering procedures and processes; • The information must be integrated among all the components in the PLM system; • A single data base must be created to reflect the product definition during the entire lifecycle of the product.

Projects are performed in different kinds of organizations: functional structure, project-based structure or matrix structure. The matrix organization is a combination of the functional organization and the “pure” project organization. In a matrix organization, there are usually two chains of command. The chain dealing with issues related to the functional division and the chain dealing with issues related to the project. Due to the split authority between project managers and functional managers, management becomes much more complicated. The cooperation between the project managers is vital for the matrix organization to perform well. Therefore, training teams of project managers in the matrix structure environment is required. A new method for training teams of project managers is presented. The proposed method is based on a real-time simulation called the Project Team Builder (PTB). PTB simulates a dynamic, stochastic multi-project management environment. A project management course for graduate students in systems engineering utilized PTB. The students used the simulator in a multi-user multi-project mode. A class of undergraduate engineering students participated in the same experiment as a control group. The 132 participants were divided into teams of three students (44 teams) which performed repetitive simulation-runs. Three factors were investigated: 1. Previous experience, 2. History recording mechanism, and 3. Team debriefing process. The findings indicate that for the initial learning phase, and for the transfer to different scenario phase, these three independent factors affect the performances. Furthermore, the interactions between the experience and history factors; between the experience and debriefing factors; and between the history and debriefing factors were all significant. Based on these findings a new paradigm for simulation-based team-learning model in a matrix organization structure is presented. The new model includes integration of history mechanism and debriefing procedure in the Kolb’s Team Learning Experience model.

Build sequence scheduling is an important topic in mixed-model production. It is to determine the order of products being built in the assembly line. Significant research has been conducted to determine good sequences based on various criteria. For example, in Just-In-Time production systems, optimal sequences are searched to minimize the variation in the rate at which different parts were consumed. This paper discusses the selection of optimal build sequences based on complexity introduced by product variety in mixed-model assembly line. The complexity was defined as the information entropy that operator processes during assembly, which indirectly measures the human performance in making choices, such as selecting parts, tools, fixtures, and assembly procedures in a multi-product, multi-stage, manual assembly environment. In an earlier paper by the authors, a simple version of complexity measure has been developed for i.i.d. (independent identically distributed) sequences. This paper extends the concept and takes into account the sequential dependence of the choices and its impact on build sequence schedules. A model based on Hidden Markov Chain is proposed to model the sequence scheduling problem with the constraints by spacing rules. Methodologies developed in this paper enhance the previous work on modeling complexity, and provide solution strategies for build sequence scheduling to minimize complexity.

Based on the group theory and group algebraic structure of the displacement set, an interesting playing toy of the magic folding square block belonging to one class of single-loop spatial eight-revolute mechanism is offered to illustrate the discontinuous mobility of mechanism. This folding toy’s mobility generally has two finite global dofs as a whole kinematic chain. Nevertheless, during the movement, the permanent finite mobility of mechanism depends on the various positions of joints. When the block profile-shape constraints are taken into account, one bifurcation between one 2-dimensional manifold and one 1-dimensional manifold occurs at an initial transition position and the other bifurcation between two 1-dimensional manifolds exists in another specified configuration. In addition, any motion of one working mode destroys the geometrical condition that is required for the other modes but a bifurcation toward a spatial mode with two finite dofs remains possible by ingoring the profile shape constraints. In fact, there is a discontinuous mobility with a trifurcation among three subsets. It is composed of a general spatial mode with 2-dimensional manifold, one part mobility chain of 2-dimensional manifold and another part mobility chain of 1-dimensional manifold.

The need for light and flexible robots is greatly increasing in the industrial engineering environment. This paper presents the design and the implementation of a PID controller for a flexible planar manipulator. The controller synthesis and tuning is based on a very accurate dynamic model of the system and is applied to a significant test case, namely a five-bar closed-chain mechanism, driven by two electric motors. The chosen PID controller is described, and the experimental results are presented and discussed. The approach followed proves the practical usefulness of the dynamic model proposed even when applied to a complex test case.

The main goal of brake by wire technology is the development of compact, cheap and flexible braking systems. Since neither brake fluid nor hydraulic lines are used, brake by wire electro-mechanical actuation is a favourable solution both for production process and environmental aspect, and offer a precise control of braking torque amplitude. One of the most critical aspect is the lack of traditional link between brake pedal and brakes (calliper); this mean a potential safety problem to be correctly managed through the system architecture, redundancies, diagnosis and recoveries. During CRF brake by wire system development several architectures were deeply analysed using PHA, FMEA, and FTA methodology to identify the best configuration for production intent. The selected one is a fault-tolerant architecture based on a time-triggered communication network connecting fail-silent nodes. From safety analysis were defined critical events and system diagnosis and recovery requirements specifications. This paper describes the steps followed in the brake by wire software development, and its validation with respect to safety needs. For this purpose a three levels design and validation process was exploited. First of all, it was defined the complete simulation template including calliper electro-mechanical actuators and theirs ECU, time-triggered communication network and vehicle control ECU. The brake by wire system was interfaced to a complete vehicle dynamics model specifically developed for control design and validation purpose. Within this environment the control software was developed and the strategies were verified applying Software In the Loop technique. Then the ECU software was automatically generated using a customised tool chain based on Real Time Workshop Embedded Coder. Than, Hardware In the Loop testing was adopted to deeply verified high level software (application), low level software (OS, API, drivers,...) and hardware. HIL bench include the complete brake by wire system and a real time platform running the same vehicle model used during previous phase. Finally, vehicle testing phases complete the evaluation in the real environment and allows the system control development and tuning toward performances and subjective aspects. In each phase the system is tested both in normal and faulty conditions; a fault injection campaign was carried on to verify system response to fault with respect to the expected one. The process is cyclical, and a new loop has to be activated for each changes in the system. At the same time, testing complexity increases in order to guarantee the system safety.

In this paper, a pattern recognition method is put forward to identify damping coefficients of rod pumping system of directional well by using characteristics space mapping. The 24-direction chain code is presented to encode the curve of dynamometer card. The parametric equation of the dynamometer card curve is transformed into Fourier series whose coefficients can be computed according to the curve’s chain codes. By means of those Fourier coefficients, shape characteristics of the curve are extracted. Euclidean distance is introduced as the measurement of similar degree between the shape characteristics of measured dynamometer card and that of simulated dynamometer card. Changing the value of viscous damping coefficient and Coulomb damping coefficient in the simulation program, different simulated dynamometer cards are obtained. Substituting their shape characteristics to the Euclidean distance, respectively, a series of distances are acquired. When the distance is little than the given error, the corresponding values of the damping coefficients in the simulation program are regarded as real damping coefficients of the rod pumping system of directional well. In the end, an example is provided to show the correctness and effectiveness of the presented method.

This paper tackles the problem of designing state observers for flexible link mechanisms: an investigation is made on the possibility of employing observers making use of suitable piecewise-linear truncated dynamics models. A general approach is proposed, which provides an objective way of synthesizing observers preventing the instability that may arise from using reduced-order linearized models. The approach leads to the identification of the regions of the domain of the state variables where the linear approximations of the nonlinear model can be considered acceptable. To this purpose, first of all, the stability of the equilibrium points of the closed-loop system is assessed by applying the eigenvalue analysis to appropriate piecewise-linear models. Admittedly, the dynamics of such a closed-loop system is affected by the pole perturbation caused by spillover, and by the discrepancies between the linearized models of the plant and the one of the observer. Additionally, when nodal elastic displacements and velocities are not bounded in the infinitesimal neighborhoods of the equilibrium points, the difference between the nonlinear model and the locally-linearized one is expressed in terms of unstructured uncertainty and stability is assessed by H ∞ robust analysis. The method is demonstrated by applying it to a closed-chain flexible link mechanism.

The new type of mechanisms — the variable structure mechanisms (VSM) possess a unique possibility of rapid and practically instantaneous transformation of the motion law of actuating link under influence of insignificant non-force displacement of one of the kinematical elements without breaking up the entire kinematical chain. The main feature of VSM is in its ability to fulfill two and more laws of motion by output link. The change of motion law for lever mechanisms occurs without disruption in the kinematical chain and thus enables to expend less effort and time. Whereas the couplings, brakes and other power impact elements control the block of interacting mechanisms till now, this results in disruption of entire kinematical chain. A considerable part of power will be required to put these elements into action. This results in decrease of machine efficiency and, especially, extremely influences the machine parts’ durability. The variable structure mechanisms (VSM) exclude such supplementary operative power consumption elements.