Safety analysis of mechatronic product lines

Most methodologies for the design and analysis of mechatronic systems target a single product. From a business perspective, successful product development requires shortening development times, reducing engineering costs and offering a greater variety of product options for customers. In software engineering, the software product line (SPL) technology has been developed to meet these conflicting goals, and several major companies have reported success stories resulting from SPL adoption. In mechanical engineering, similar methodologies have been developed under the name of product platforms. Methodologies for analyzing product qualities such as safety or reliability have been introduced for both SPL and product platforms. The problem with these methodologies is that they consider either software or mechanical product design, so they do not guide developers to find the best balance between the controller and the equipment to be controlled. Several system properties of a mechatronic product line should be investigated with mechatronic analysis methodologies before the development process branches to software, electronic and mechanical design. In particular, safety is one system property that can only be analyzed by considering both the equipment and its controller, so mechatronic methodologies early in the design are advantageous for discovering safety-related design constraints before costly design commitments are made. This paper extends the Functional Failure Identification and Propagation (FFIP) framework to the safety analysis of a mechatronic product line with options in software signal connections and equipment. The result of applying FFIP is that unsafe combinations of options are removed from the product line.     

Fabrication of a pneumatically driven single-cell trap

This paper describes the creation of a pneumatically driven single-cell trap and its ability to trap a live single cell. The cell-trap device consists of a pneumatic vibrator array and a trap chamber used to trap single cells. The entire structure was manufactured with polydimethylsiloxane (PDMS). External compressed air was used to actuate the pneumatic vibrators. The magnitude and frequency of the pneumatic force were controlled by programmable electromagnetic valves. The live cell in the trap chamber was manipulated using the velocity field of the cell media induced by deformation of the vibrator diaphragm. The cell was successfully trapped in the central equilibrium region of the device, at which point the axial velocity fields generated by the vibrators were minimized. The intracellular calcium response of a single cell induced by mechanical stimuli during cell trapping was measured to verify the effectiveness of the pneumatic cell trap as a stress-free trapping method. The results showed that the internal signaling in the cell was sensitive to the extracellular physical environment. Since the measured intensity of the intracellular calcium of the single cell was very minor, the pneumatic cell trap described in this paper was categorized as a harmless trapping method.     

Synthesis of modular mechatronic products: a testabilityperspective

Producing modular products that combine modules with the consideration of product performance, e.g., testability of electronic systems, is frequently stated as a design goal. However, most of mechatronic frameworks (models) discussed in the literature do not consider testability of electronic subsystems of mechatronic products. This paper assumes that the product modules have been established, and aims at the development of modular mechatronic products with the consideration of testability of electronic subsystems as a performance criterion. The generation of modular products and module testability issues are discussed. Testability points, testability values, and access paths for a module/system are crucial to the generation of modular mechatronic products. A generalized label-correcting algorithm is developed to determine the points of focus, testability values, and access paths in modules     

An analysis of a coupled-ring rotary joint design

A theoretical and experimental analysis of a coupled-ring rotary joint design is described. A rotary joint of this type is commonly used for mechanically scanned, multichannel radars. The main goal of the analysis is to develop a better understanding for the transfer of energy through the joint's highly coupled rings. The author considers the geometry of a typical single channel and then describes a coupled transmission line model for the coupled-ring network. Using the model, the author determines the type of ring network needed for low channel loss and small rotational variations of this loss. Measurements on some test models support the predictions of the analysis     

Mirror synthesis in a mechatronic system for superficial defect detection

This paper deals with the problem of defect detection on highly reflective surfaces making use of vision systems. A new mechatronic system has been developed, based on a nonflat mirror. According to the method described in this paper, the light rays emitted from a source hit a suitably designed nonflat mirror, and are reflected so as to illuminate the curved surface under investigation. The path of the light rays from the source of light to the mirror and then to the object surface is mathematically traced making use of the optical geometry laws. After the reflection on the object surface, the light rays are collected by a charge-coupled device (CCD) camera and elaborated by a vision system, which manages to detect the surface defects as shadows of various shape and size within the picture. Simulations have been carried out in order to provide the optimal mirror shape. Moreover, a prototype of the mechatronic system, including the synthesized mirror, has been built to perform some experimental tests to validate the method. The results, reported in the paper, definitively show the effectiveness of the proposed method.     

Robust tracking control of mechatronic arms

A robust tracking control scheme based on variable structure systems (VSS) theory is presented to cope with the uncertainties and parameter variations in mechatronic arm dynamics. A modification of VSS is used to remove its restrictions with regard to chattering and required control efforts. By blending VSS with a self-organizing controller (SOC), a sliding mode self-organizing controller (SLIMSOC)scheme has been developed. In this scheme, both control actions and performance evaluation are executed using the distance from the desired sliding surface and rate of approach to it. Comparisons are drawn and it is shown that the inherent robustness properties of variable structure systems are retained while the undesirable chatter motion of the sliding mode is eliminated. The results are illustrated by applications of SLIMSOC on a direct drive SCARA type of robot.     

Automatic calibration with robust control of a six DoF mechatronic system

This paper presents a robust control methodology incorporating an automatic calibration step to compensate dynamic variations in a 6 DoF mechatronic system. The application used to illustrate the efficacy of the proposed approach is the ball and plate system based on the Stewart platform. To emulate dynamic changes in the system, we make use of various types of balls, varying in mass, diameter and surface. An automatic calibration step is introduced to obtain a model based on the type of ball which is placed on the plate. Using a model-based tuning technique, an optimal proportional-differential (PD) controller is designed based on the previous calibration. The resulting controller is tested for robustness by changing the ball without changing the controller parameters. The results indicate that our setup is robust and performs well in the presence of significant changes.     

Development of a mechatronic sorting system for removing contaminants from wool

Automated visual inspection (AVI) systems have been extended to many fields, such as agriculture and the food, plastic and textile industries. Generally, most visual systems only inspect product defects, and then analyze and grade them due to the lack of any sorting function. This main reason rests with the difficulty of using the image data in real time. However, it is increasingly important to either sort good products from bad or grade products into separate groups using AVI systems. This article describes the development of a mechatronic sorting system and its integration with a vision system for automatically removing contaminants from wool in real time. The integration is implemented by a personal computer, which continuously processes live images under the Windows 2000 operating system. The developed real-time sorting approach is also applicable to many other AVI systems.     

Investigation of mechatronic education in South Korea

This paper presents diverse aspects of South Korean mechatronic education in an effort to provide the basis of constructing a more desirable educational system on mechatronics. For this purpose, an analysis of the curriculum of 15 universities with departments of mechatronics are presented. It can be said that, in South Korea, characteristics of mechatronic education is that independent organizations for Mechatronics are operated over 15 universities and their curriculum is evolved to adapt local industrial environments. Almost all of them are trying to meet the requirements of Accreditation Board of Engineering Education of Korea (ABEEK), which is very similar to Accreditation Board of Engineering and Technology (ABET) in the United States. Another distinguishing feature is that the National Qualification Test for Mechatronics is offered in South Korea. The problem to be solved in near future is that there are some conflicts between ABEEK requirements and National Qualification Test. The ratio of students from vocational high schools entering 4-year universities is increasing in South Korea. The same tendency can be found in Japan, and some universities are trying to offer preparation courses to provide basic knowledge on physics, mathematics and chemistry to them.     

Advanced mechatronic design using a multi-objective genetic algorithm optimization of a motor-driven four-bar system

In this work we present a genetic algorithm based method to design a mechatronic system. First, we present the sequential approach where we optimize the geometry of the mechanism, for a given path, and then solve the dynamic problem where we take into account the characteristics of the motor along with the inertia of the different links of the mechanism. Several types of objective functions are tested. We show, however, that this sequential method does not yield acceptable results for the dynamic behavior due to the fact that the geometry is assumed fixed when optimizing the dynamics. This led us to formulate a global optimization problem where all the parameters of the mechanism are considered simultaneously. The problem is then presented as a multi-objective optimization one where the geometry and the dynamics are considered simultaneously. The obtained solutions form what is called a “Pareto front” and they are analyzed for several different design conditions. This paper also shows the advantages of a multi-objective optimization approach over the single-objective one.     

反斯托克斯荧光制冷的热力学分析

从1995年Epstein实现了光与热的制冷效应的历史性突破以来,由于该制冷方法具有全光性的独特优点,同时制备的制冷器具有无振动和噪声、无电磁辐射、体积小、重量轻、可靠性高等特点,故反斯托克斯荧光制冷器在军事、航天卫星、微电子、低温物理与工程等领域具有非常诱人的应用前景。运用热力学基本定律对反斯托克斯荧光制冷过程中的能量转换关系及转换深度进行分析,推导出这一过程的最大热力学效率的计算公式,获得设计激光制冷器热力学限制上限。     

On conceptual design of intelligent mechatronic systems

We have technology now to design networks of small intelligent units capable of competing and/or co-operating with each other on specified tasks and making decisions under conditions of uncertainty through a process of negotiation. In highly dynamic environments, such distributed systems are capable of achieving considerably better results in terms of performance/cost ratio and reliability than conventional centralised large systems and structures. The major elements of these systems are intelligent agents, which are software objects capable of communicating with each other, as well as reasoning about received messages. The paper discusses conceptual design of mechatronic systems based on multi-agent technology.     

Modular design of mechatronic systems with function modeling

This paper develops a modularization scheme based on the functional model of a system. The modularization approach makes use of the function–behavior–state (FBS) model of the system to derive the entity relations. The design structure matrix (DSM) is automatically constructed based on the FBS model. In this way, the tedious work of filling the DSM entries based on expert knowledge is avoided. The approach makes use of k-means clustering algorithm to allow the user to try different number of clusters in a fast way. The k-means clustering is adopted for DSM based modularization by defining a proper entity representation, relation measure and objective function. Two modularization schemes are performed, one based on the immediate relations and one on the deeper behavioral relations between the components. Considering the application on the shifting system of the Delft University of Technology (DUT) Formula Student car, the latter modularization resulted in more mechatronic behavior based modules, while the former resulted in modules based on mere disciplinary and spatial closeness.     

An original mechatronic design of a kinaesthetic hand exoskeleton for virtual reality-based applications

Within the new industrial era, the interaction between humans and virtual reality is spreading across our lives. The development of exoskeleton designed to enhance the immersivity of virtual reality environments has a potentially considerable social impact and arises as a hot research topic. The presented work dwells well with the subject by describing the mechatronic design process of a kinaesthetic hand exoskeleton system meant to reproduce proprioceptive stimuli coming from the interaction with a virtual reality. The presented prototype is a modular device, equipped with force and pose sensors, and driven by a Bowden-cable-based remote actuation system. Unlike similar devices, the proposed exoskeleton is specifically thought for VR interaction and is designed to be reversible while exerting up to 15 N per finger. For a more accurate rendering of kinetostatic finger stimuli, a procedure for reconstructing HMI force as a function of measured force and position signals by employing a system’s kinematic and dynamic model is presented, detailed, and followed by some preliminary tests. The results showed that the model can trace forces back to the end-effector with a percentage error below 15%.     

The Illinois Roadway Simulator: a mechatronic testbed for vehicledynamics and control

The Illinois Roadway Simulator (IRS) is a novel, mechatronic, scaled testbed used to study vehicle dynamics and controls. An overview of this system is presented, and individual hardware issues are addressed. System modeling results on the vehicles and hardware are introduced, and comparisons of the resulting dynamics are made with full-sized vehicles. Comparisons are made between dynamic responses of full-scale and IRS-scale vehicles. The method of dynamic similitude is a key to gaining confidence in the scaled testbed as an accurate representation of actual vehicles to a first approximation. The IRS is then used in a vehicle control case study to demonstrate the potential benefits of scaled investigations. The idea of driver-assisted control is formulated as a yaw-rate model-following problem based on the representation of the driver as a known disturbance model. The controller is designed and implemented to show that the vehicle's dynamics can be changed to match a prescribed reference model     

Design and development of a mechatronic infant torso simulator for respiratory physiotherapy learning

Currently, constraint-free realistic context training is nonexistent in infant physiotherapy. In order to enhance the vocational learning of novices, in close collaboration with expert physiotherapists, we designed an innovative simulator dedicated to the training of infant respiratory physiotherapy. This paper describes the simulator’s functionalities and the method used to design its physical structure and the learning paradigm. Firstly, regarding a cognitive approach, relevant vocational and didactic criteria were defined in order to characterize the gesture and determine its limits for a nondangerous practice. Subsequently, we chose physical parameters to assess the criteria and define the specifications of the simulator. The mechatronic functions arose from a didactic transposition of the expected simulation-based functionalities. A 6-month-old infant torso physical structure has been designed with the use of finite element simulations. Its mechanical behaviour provides the possibility to deform the mannequin like a real infant during physiotherapy manoeuvres. A prototype has been realized and validated.     

Scaling-law-based metamodels for the sizing of mechatronic systems

This paper presents a new metamodel form and associated construction procedure adapted to the sizing tasks of mechatronics systems. This method of meta-modeling uses scaling laws to extract compact forms of design models from local numerical simulations (FEM). Compared to traditional metamodels (polynomial response surfaces, kriging, radial basis function) the scaling-law-based metamodels have the advantage of a light, compact form and good predictive accuracy over a wide range of the design variables (several orders of magnitude). The general regression process is first explained and then illustrated on different examples: a purely numerical test function, a limited angle electromagnetic actuator and a flexible mechanical hinge.     

Integrating viewpoints in the development of mechatronic products

The development of mechatronic products involves multiple stakeholders which have different viewpoints and therefore use different concepts, models and tools to deal with their concerns of interest. This paper argues that an increased emphasis needs to be placed on the relations between viewpoints to be able to deal with the evolving scope and requirements on mechatronic products. We study relations between viewpoints at the levels of people, models and tools, and present solutions that are used to formally and explicitly capture such relations. Viewpoint contracts are used to define the vocabulary, assumptions and constraints required for ensuring smooth communication between stakeholders (people level). Dependency models capture relations between product properties belonging to different viewpoints, and how such dependencies relate to predictions and decisions (model level). Tool integration models describe the relations between tools in terms of traceability, data exchange, invocation and notifications (tool level). A major contribution of this paper is a unification approach, elaborating how these solutions can be used synergetically to integrate viewpoints. An industrial robot case study is utilized to illustrate the challenges and solutions with respect to relations between viewpoints, including the unification approach.