Micro gear validation: improving the correlation between virtual and physical testing

Downsizing mechanical systems requires the consideration of technological environment and restrictions. Nominal dimensions can be miniaturized, but shape and material deviations cannot be scaled down in the same way. In design these effects have to be considered and thus analyzed and evaluated in the very early activities. Simulation and test methods have to be adapted to the special characteristics of microtechnology. The present paper provides a strategy to validate micromechanical systems by means of virtual and physical testing. A standard test approach in macroscopic gear metrology, the tangential composite inspection, is used as validation tool for both test approaches. The results are very promising and show a good correlation between both miniaturized tests procedures.     

Virtual shaft: Synchronized motion control for real time testing of automotive powertrains

The complexity of automobile powertrains continues to rise, leading to increased development time and effort. Synchronous testing with spatially distributed test benches allows improvements by front-loading of the validation phase. Nevertheless, virtualization of the mechanical interaction of shaft connections is required. A virtual shaft algorithm (VSA) is investigated for synchronized motion control in separate test benches. The behavior of a rigid mechanical shaft is analyzed and modeled. The mechanical shaft is substituted by two electrical motors and a superimposed VSA controller. This virtual shaft is established between two test benches for a combustion engine and a mechanical transmission. Control algorithms for synchronized motion control, known from web machines and force feedback, are analyzed. A controller layout with separate torque and speed controllers is implemented and analyzed through transfer function mathematics. The controllers are parametrized analytically for different gears. The effect of communication delay on the VSA is analyzed by simulation. The open clutch situation is handled by deactivation of the torque feedback. Validation on real test benches shows small deviations for torque and speed. Further work will focus on the necessity of system knowledge for controller layout and on the transient behavior during shifting.     

Microscale and nanoscale robotics systems [Grand Challenges of Robotics]

Depending on their overall size, sensing and actuation precision, part or tool size, and task space, robotic systems can be classified as microrobotics or nanorobotics, respectively. Micro/nanorobotics represents these two different scale robotics areas jointly while keeping their clear scale differences in mind. At its current early infancy, the field of micro/nanorobotics has two major research thrust areas. Analogous to the manipulation area in macroscale robotics, the first area explores new methods for programmable manipulation and assembly of micro- and nanoscale entities. Here, the overall micro/nanorobotic system size can be very large, while only the manipulation tools, manipulated objects, and sensing, actuation, and manipulation precision are required to be at the micro/nanoscale. On the other hand, the second research area focuses on overall miniaturization of mobile robots down to mum overall sizes with various locomotion capabilities such as flying, swimming, walking, hopping, rolling, and climbing. In these mobile robotic systems, overall system size is very limited, which induces severe constraints in utilized actuators, sensors, motion mechanisms, power sources, computing power, and wireless communication capability. These two research thrusts are described in detail in the following sections     

具有空间连续行为的微型压力传感器系统级建模

大多数MEMS器件(如梁、膜等)的动态特性方程为偏微分方程,因此建立对应组件的可重用参数化行为模型是一个难题.本文通过有限差分法把偏微分方程转化为常微分方程组,然后采用混合信号硬件描述语言进行描述,解决了该问题.针对电容式微型压力传感器,专门考虑膜片的空间连续行为以及结构、静电力的耦合作用,建立了包含接口电路在内的系统模型,据此进行了动态行为仿真.通过结果对比,验证了方法的实用性.相对于通用的参数化组件模型,当前MEMS商业化软件多采用逐个器件进行宏模型抽取的方式实现系统级建模和仿真.     

Overload effects and their prevention

The so-called “thrashing effect”, well known from virtual storage, but also reported from data-base systems and packet switching networks, has turned out to be a common phenomenon of large systems with concurrent processing. It simply means that beyond a saturation point an increase of the load (e.g. number of jobs) leads to a (sometimes sudden) decrease in performance (e.g. throughput). With growing size and complexity of computer systems and the general trend towards distribution, overload phenomena of different origin can interfere and superimpose mutually, resulting in a composite overload effect that can hardly be broken down into its constituents. Because the complexity of such systems defies detailed modeling, it is more appropriate to look at those systems in a more macroscopic, behavioral way, considering only the two externally measurable variables “load” and “throughput”. The resulting abstraction from internal details can smooth the way to a more general treatment and application. The article deals with such overload phenomena and their prevention in a general way using a control-theoretic approach. Special emphasis is placed on dynamic behavior, where load characteristics are changing with time, making feedback mechanisms necessary. The problem is approached as a dynamic optimum search problem for which different algorithms are presented and compared by simulation.     

模糊PID控制在H型钢张力控制中的应用

从H型钢的两机架轧制入手，推导出H型钢两机架轧制的系统模型和张力模型。在此基础之上，采用模糊控制与PID控制方式相结合的控制策略，设计了微张力模糊控制系统。同时考虑到轧件宽度的要求，模糊控制规则表采用了不对称取法。仿真与试验结果表明，该控制方法很好地改善了系统的动态特性，提高了稳态精度。     

计算机仿真评估电子战系统的基本方法

对电子战（ＥＷ）系统在完成作战任务中的作用和使用效果进行定量描述和测试、评估（Ｅ＆Ｔ）具有十分重要的地位。计算机建模和仿真是全面分析和评估ＥＷ系统动态行为的效能的重要手段。该文综述了计算机仿真在ＥＷ系统评估中的应用,并从ＥＷ的特点出发,把ＥＷ系统的仿真评估分为三个层次：工程级、系统级和任务级。提出根据这三个层次的标准规范建立系统数学模型和设计ＥＷ系统仿真模型构件的概念,用于构筑大型复杂的ＥＷ系统评估的仿真环境,走发展和利用综合仿真的道路。     

Design of practical optimum JIT systems by integration of computer simulation and analysis of variance

This study introduces a framework for re-design of manufacturing systems into practical optimum just-in-time systems by integration of computer simulation and analysis of variance. The conventional JIT approach is mostly applicable to static production systems and the dynamic production systems require a more practical integrated JIT approach. In addition, the re-design of existing dynamic systems into just-in-time systems must follow a practical path, which can be a cumbersome task. This means, a unique practical optimum just-in-time system that considers system's limitations and its dynamic behavior must be designed. To achieve the objective of this study, first, the actual system must be totally modeled and simulated. Second, the integrated simulation model is tested and validated by analysis of variance. Third, the optimum (most fitted) JIT design is developed and tested by modeling actual system's limitations and its dynamic behavior. The framework is applied and tested for an auto production line and a heavy rolling mill workshop.     

Analyzing and comparing the performance of two real-time playback systems

A technique used in animated computer graphics involves the use of real-time playback. This method is used when it is not possible to display frames of display code in real-time. Instead, frames are compiled in advance at non realtime rates, saved in secondary storage, and played back at desired realtime speeds. The basic design and operation of two such systems will be considered. The more powerful of the two is built upon an Evans and Sutherland picture System I and utilizes animated vector graphics. The other playback system is built upon a Terak micro computer display and represents an example of rudimentary raster graphics animation. The synchronization, buffering, blocking and man-machine interfaces of both systems are detailed thus spotlighting their operational behavior. A comparison of the two systems show: that similarities in the logical organization of each system exist; that both systems are input bound; and both require their image files to be built on other computer systems. The differences in the performance of the two systems can be attributed to technological differences between the two systems; the retrieval rates of their respective disk subsystems; and differences in the intent and purpose behind the design of each machine. The systems are demonstrated by applying them to chemical modeling. It is determined that playback is a useful technique for examining complicated sequential situations or for providing the concise and convenient representation of large amounts of data.     

椭圆类齿轮参数化设计与运动仿真系统的开发

非圆齿轮因其节曲线为非圆形,计算复杂,设计困难,目前的三维设计软件都无法直接进行实体建模。根据非圆齿轮的设计理论,利用Visual Basic 6.0良好的界面设计功能和计算能力对SolidWorks进行二次开发,设计出椭圆类齿轮参数化设计与运动仿真系统,实现了椭圆类齿轮的三维参数化建模与运动仿真。论述了系统的开发过程,运行实例表明系统界面友好,设计正确。解决了椭圆类齿轮设计中的复杂计算和三维实体造型难的问题,可提高设计精度、缩短产品开发周期,保证产品质量。     

Applying Computer Modeling to Examine Complex Dynamics and Pattern Formation of Tissue Growth

For research in areas such as developmental biology and cancer, understanding the formation and regrowth of tissue is of great importance. Since complex system behavior makes it difficult to interpret dynamics and pattern formation of tissue growth, it is helpful to have a way to simulate the cell systems and test hypotheses about the mechanisms by which the system is responding. Computer “modeling experiments” can serve this purpose, as we show with an example of the small intestine epithelial cells' response to cytosine arabinoside. This example demonstrates that nonhomogeneities in the cell population can play an important role and emphasizes the need to use a modeling approach, like our spatial modeling, that addresses the differences within the tissue structure. These types of “modeling experiments” can guide researchers with further experiments and provide clues as to how complex cell proliferation behavior is linked to underlying molecular phenomena.     

A numerical study on the fatigue and rolling contact fatigue behaviour of PVD-coated steel and titanium spur gears

Thin hard coatings deposited with physical vapor deposition (PVD) can enhance both the fatigue and the rolling contact fatigue resistance of mechanical components. In this work a cheap and fast way to evaluate the best parameter levels of coating and bulk material is proposed. Design of Experiments (DoE) was applied to the numerical results obtained from the simulation of meshing PVD-coated spur gears. Preliminary analyses were performed to assess the fatigue behaviour of PVD-coated standard specimens for rotating bending tests. The coating elastic modulus and thickness, and the trend of the residual stresses induced by the deposition process were considered among the variables affecting the fatigue and the rolling contact fatigue behaviour. Different bulk materials, including steel and titanium alloys, were analyzed. The proposed method may help to define the optimal coating design, especially when the replacement of traditional steels with light alloys constitutes a goal that is strongly recommended.     

A continuous simulation approach for supply chains in the automotive industry

In the automotive industry supply chains, several factories collaborate to manufacture a product (car, engines, etc.). In order to fulfill customers’ needs, they have to be designed and organized in the proper way. The dynamic analysis of their behavior through simulation provides important information to improve their performances. Most existing research works addressing the modeling and simulation of supply chains are generally based on a discrete event worldview. We are concerned here with medium or long term decision problems, which necessitate “macroscopic” models of the supply chain. At these levels, the representation of the individual flows of the numerous parts that circulates in the supply chain being quite difficult, given the objectives considered, we chose a continuous worldview. The models are based on Forrester’s system dynamic paradigms. The proposed approach is actually applied to a large French company, in the automotive industry. The supply chain presented in this article is composed of five existing plants, located in two different production areas. The results show the concrete benefits that can be achieved. Several research directions are suggested.     

Sliding simulation for adhesion problems in micro gear trains based on an atomistic simplified model

The objective of this research work is to provide a systematic method to perform molecular dynamics simulation or evaluation for adhesion of micro/nano gear train during sliding friction in MEMS. In this paper, molecular dynamics simulations of adhesion problems in micro gear train are proposed. The perfect MEMS gear train model is very complicated by considering the computing time. A simplified model to simulate surface sliding between metals by molecular dynamics (MD) is proposed because the surface property is a dominant factor for the performance of gear systems. Based on analysis of sliding friction and the transmitting characteristics of micro gear train, a model is established by utilizing the Morse potential function. The Verlet algorithm is employed to solve atom trajectories. The simulation results show that adhesion tends to occur between two micro gears after certain cycles and such adhesion accounts for the friction force and the temperature increase. The simulation results are in consistence with the experimental results in the literature. The model is meaningful to prolong the lifetime of micro gear train by selecting proper parameters.     

Ensuring functional reliability of molded micro components

Microsystems technology is an emerging technology that is used in ever more technical systems, such as inkjet nozzles or accelerometers. 3D micromechanical structures became feasible by miniaturizing macromechanical elements. One big challenge in downsizing mechanical elements is to adapt conventional manufacturing technologies to the conditions of microtechnology. Integrated design and production processes must be suited to the new requirements, in-depth knowledge of production technology is required to design micromechanical components. Since 2000, the Collaborative Research Center 499 “Design, Production and Quality Assurance of Molded Microcomponents made of Metallic and Ceramic Materials” has been focusing on a continuous and stable process chain for molded micro components (Albers et al. 2005, Microsyst Technol). The aim of prior funding periods was to develop the knowledge about how components, such as gearwheels, and systems, such as micro gears, can be designed. Present research is focused on how to design functional elements, i.e. shaft-hub joints to transmit torque. This paper will introduce an approach that generates know-how via testing several plain bearings and shaft-hub joints in order to derive the necessary know-how to develop simulation tools later on.     

Use of penalty formulations in dynamic simulation and analysis of redundantly constrained multibody systems

The determination of particular reaction forces in the analysis of redundantly constrained multibody systems requires the consideration of the stiffness distribution in the system. This can be achieved by modeling the components of the mechanical system as flexible bodies. An alternative to this, which we will discuss in this paper, is the use of penalty factors already present in augmented Lagrangian formulations as a way of introducing the structural properties of the physical system into the model. Natural coordinates and the kinematic constraints required to ensure rigid body behavior are particularly convenient for this. In this paper, scaled penalty factors in an index-3 augmented Lagrangian formulation are employed, together with modeling in natural coordinates, to represent the structural properties of redundantly constrained multibody systems. Forward dynamic simulations for two examples are used to illustrate the material. Results showed that scaled penalty factors can be used as a simple and efficient way to accurately determine the constraint forces in the presence of redundant constraints.     

非圆齿轮三维造型设计系统的开发

基于非圆形节曲线的非圆齿轮设计和计算要比圆齿轮复杂得多。由于非圆齿轮各轮齿的形状不尽相同,因此无法使用阵列、镜像等方法进行建模。目前的三维机械CAD软件还不能直接进行非圆齿轮实体建模。文章利用Visual Basic语言对三维软件SolidEdge进行二次开发,实现了齿轮的根切校验、凸性校验、压力角计算等功能,建立了非圆齿轮的三维建模系统,为非圆齿轮三维建模参数化设计提供了一种方法。生成的齿轮三维实体可用于装配设计、运动仿真及计算机辅助教学中。     

Planning for mechatronics systems—Architecture, methods and case study

Mechatronic systems are a relatively new class of technical systems. The integration of electro-mechanical systems with hard- and software enables systems that adapt to changing operation conditions and externally defined objective functions. To gain superior system performance from this ability, sophisticated decision making processes are required. Planning is an ideal method to integrate long-term considerations beyond the time horizon of classical controlled systems into the decision making process. Unfortunately, planning employs discrete models, while mechatronic systems or controlled systems in general emphasize the time continuous behavior of processes. As a result, deviations of the actual behavior during the execution from the planned behavior plan cannot be entirely avoided. We introduce a hybrid planning architecture, which combines planning and learning from artificial intelligence with simulation techniques to optimize the general system behavior. The presented approach is able to handle the inevitable deviations during plan execution, and thus maintains feasibility and quality of the created plans.     

Probabilistic Boolean network modeling of an industrial machine

Theoretical modeling of manufacturing processes assists the design of new systems for predictions of future behavior, identifies improvement areas, and evaluates changes to existing systems. A novel approach is proposed to model industrial machines using probabilistic Boolean networks (PBNs) to study the relationship between machine components, their reliability and function. Once a machine is modeled as a PBN, through identification of regulatory nodes, predictors and selection probabilities, simulation and property verification are used to verify model correctness and behavior. Using real machine data, model parameters are estimated and a PBN is built to describe the machine, and formulate valid predictions about probability of failure through time. Two models were established: one with non-deterministic inputs (proposed), another with components’ MTBFs inputs. Simulations were used to generate data required to conduct inferential statistical tests to determine the level of correspondence between predictions and real machine data. An ANOVA test shows no difference between expected and observed values of the two models (p value = 0.208). A two-sample T test demonstrates the proposed model provides values closer to expected values; consequently, it can model observable phenomena (p value \(=\) 0.000). Simulations are used to generate data required to conduct inferential statistical tests to determine the level of correspondence between model prediction and real machine data. This research demonstrates that using PBNs to model manufacturing systems provides a new mechanism for the study and prediction of their future behavior at the design phase, assess future performance and identify areas to improve design reliability and system resilience.     

基于Marc的快速弹簧卷制仿真

随着铁路事业的迅猛发展,弹簧产品的性能提升到一个新的高度.弹簧在制造过程中由于受炉内加热、成形和淬火等工艺的影响,成形后在保证弹簧性能的前提下不易对其进行调整,借助仿真手段对其进行试加工制造是个很好的途径.由于弹簧的种类繁多,卷制仿真从模型建立到结果提交需要花费几个小时.从脚本文件的建立入手,针对弹簧卷制过程涉及的操作进行脚本录入,最后形成对同一类型弹簧制造过程的卷制仿真程序,通过对比大大节约仿真时间,提升仿真效率.