A systematic approach to constructing families of incremental topology control algorithms using graph transformation

Software and Systems Modeling - In the communication system domain, constructing and maintaining network topologies via topology control algorithms is an important crosscutting research area....     

Analysing refactoring dependencies using graph transformation

Refactoring is a widely accepted technique to improve the structure of object-oriented software. Nevertheless, existing tool support remains restricted to automatically applying refactoring transformations. Deciding what to refactor and which refactoring to apply still remains a difficult manual process, due to the many dependencies and interrelationships between relevant refactorings. In this paper, we represent refactorings as graph transformations, and we propose the technique of critical pair analysis to detect the implicit dependencies between refactorings. The results of this analysis can help the developer to make an informed decision of which refactoring is most suitable in a given context and why. We report on several experiments we carried out in the AGG graph transformation tool to support our claims.     

A cooperative approach for topology control in Wireless Sensor Networks

The choice of the transmission power levels adopted in Wireless Sensor Networks (WSNs) is critical to determine the performance of the network itself in terms of energy efficiency, connectivity and spatial reuse, since it has direct impact on the physical network topology.In this paper, a cooperative, lightweight and fully distributed approach is introduced to adaptively tune the transmission power of sensors in order to match local connectivity constraints. To accurately evaluate the topology control solution, a small-scale testbed based on MicaZ sensor nodes is deployed in indoor and outdoor scenarios. Practical measures on local and multi-hop connectivity, convergence time and emitted power are used to compare the proposed approach against previous solutions. Moreover, mathematical programming formulations of the topology (power) control problem are introduced to assess the optimality of the distributed algorithm. Finally, simulation analysis complements the experimental evaluation in large-scale static and mobile WSN scenarios, where a testbed implementation becomes unfeasible.     

A graph theoretic approach to multivariable control system design

A graph theoretic approach is described for the design of multivariable control for large systems as an alternative to geometric methods. An example is given f⊙r a distillation column to demonstrate the technique, with a particular reference to aspects of disturbance rejection and the possibilities for pole assignment.     

PUPIL: A systematic approach to software integration in multi-scale simulations

We present a relatively straightforward way to integrate existing software packages into a full multi-scale simulation package in which each application runs in its own address space and there is no run-time intervention by the researcher. The PUPIL (Program for User Package Interfacing and Linking) architectural concept is to provide a simulation Supervisor, implemented as a Manager and various Workers which involve small wrapper interfaces written and installed within each application package and various communication services. The different, autonomous packages (“Calculation Units”) are plugged into the PUPIL system which one then operates as a software driver for them. Well-defined protocols are provided for communication between the different Calculation Units and the PUPIL system. The CORBA communication protocol is used to exchange information between running processes. All simulation directives from the user are stored in an XML file that is interpreted by the PUPIL Manager and Workers. An initial version has been designed using the Object Oriented (OO) paradigm and implemented in Java as a fast prototyping language. Tests of implementation ease and of operational correctness (on toy physical systems) have been carried out. In the former category, we document how interfaces to both DL_POLY and SIESTA were done relatively straightforwardly. In the latter category, the most demanding test was the joining of three different packages to do a MD calculation with pattern recognition to identify the QM-forces region and an external QM force calculation. The results show that PUPIL provides ease of operation and maintenance with little overhead.     

A parallel portfolio approach to configuration optimization for large software product lines

Software product line (SPL) engineering demands for optimal or near‐optimal products that balance multiple often competing and conflicting objectives. A major challenge for large SPLs is to efficiently explore a huge space of various products and satisfy a large number of predefined constraints simultaneously. To improve the optimality and convergence speed, we propose a parallel portfolio approach, called IBEAPORT, which designs three algorithm variants by incorporating constraint solving into the indicator‐based evolutionary algorithm in different ways and performs these variants by utilizing parallelization techniques. Our approach utilizes the exploration capabilities of different algorithms and improves optimality as far as possible within a limited time budget. We evaluate our approach on five large‐scale real‐world SPLs. Empirical results demonstrate that our approach significantly outperforms the state of the art for all five SPLs on a quality indicator and a diversity indicator. Moreover, IBEAPORT quickly converges to a relatively stable hypervolume value even for the largest SPL with 6888 features.     

A constructive approach to solving 3-D geometric constraint systems using dependence analysis

Solving geometric constraint systems in 3-D is much more complicated than that in 2-D because the number of variables is larger and some of the results valid in 2-D cannot be extended for 3-D. In this paper, we propose a new DOF-based graph constructive method to geometric constraint systems solving that can efficiently handle well-, over- and under-constrained systems based on the dependence analysis. The basic idea is that the solutions of some geometric elements depend on some others because of the constraints between them. If some geometric elements depend on each other, they must be solved together. In our approach, we first identify all structurally redundant constraints, then we add some constraints to well constrain the system. And we prove that the order of a constraint system after processing under-constrained cases is not more than that of the original system multiplied by 5. After that, we apply a recursive searching process to identify all the clusters, which is shown to be capable of getting the minimum order-reduction result of a well-constrained system. We also briefly describe the constraint evaluation phase and show the implementation results of our method.     

A specification-based approach to concurrency analysis

The behavior of a concurrent program often depends on the arbitrary interleaving of computations performed by asynchronous processes. The resulting non-determinism can lead to such phenomena as deadlock and starvation, making program development extremely difficult, and consequently making the development of tools for formal analysis highly desirable.A specification-based approach to concurrency analysis is a particularly promising way of addressing some of the difficulties inherent in concurrent program development. According to this approach, a programmer first writes a specification describing the interprocess communication behavior of a concurrent program. A set of formal analysis techniques are then applied in an effort to determine whether the specification can be fully satisfied. If the analysis is successful, target code is generated automatically that conforms to the specification.This approach has a variety of benefits. While such properties as safety and liveness are rather difficult to discern in actual code, they are actually easy to include as part of a specification. Moreover, state spaces induced by specifications tend to be smaller and more manageable than state spaces of actual code, and this leads to more effective analysis techniques. Finally, the generation of interprocess communication code from formal specifications is accomplished in a relatively straightforward manner.Research partially supported by NSF grant CCR-9109231.     

An improved robust model predictive control approach to systems with linear fractional transformation perturbations

In this paper, a robust model predictive control approach is proposed for a class of uncertain systems with time-varying, linear fractional transformation perturbations. By adopting a sequence of feedback control laws instead of a single one, the control performance can be improved and the region of attraction can be enlarged compared with the existing model predictive control (MPC) approaches. Moreover, a synthesis approach of MPC is developed to achieve high performance with lower on-line computational burden. The effectiveness of the proposed approach is verified by simulation examples.     

A systematic approach to the Kansei factors of tactile sense regarding the surface roughness

Designing products to satisfy customers' emotion requires the information gathered through the human senses, which are visual, auditory, olfactory, gustatory, or tactile senses. By controlling certain design factors, customers' emotion can be evaluated, designed, and satisfied. In this study, a systematic approach is proposed to study the tactile sense regarding the surface roughness. Numerous pairs of antonymous tactile adjectives are collected and clustered. The optimal number of adjective clusters is estimated based on the several criterion functions. The representative average preferences of the final clusters are obtained as the estimates of engineering parameters to control the surface roughness of the commercial polymer-based products.     

A systematic approach to data security

The problem of selecting internal controls, or that subset of those controls we call security measures, in a data processing environment yields rather readily to an orderly, systematic approach. Such an approach requires recognition that a control should not be implemented if it costs more than tolerating the problem. Further, no control should be implemented which is more costly or less effective or displaces less potential loss than does some other control. The basic concept and outline of the systematic approach is described and references to supplemental papers for guidance in specific areas is provided through the bibliography.     

A cascade control approach to active suspension using pneumatic actuators

Operators of forest machinery suffer from intensive whole body vibrations, which are big threats to their health. Therefore, it is important to investigate effective seat undercarriages and control methods for vibration reduction. This paper addresses the control problem of a novel seat undercarriage with pneumatic actuators customized for forest machinery. A two‐layer cascade control structure is developed, where the top layer consists of a group of proportional controllers to regulate the position of pneumatic actuators and the bottom layer is a sliding mode controller for force and stiffness tracking. The advantage of the sliding mode control is to achieve robust control performance with coarse system models. The paper demonstrates that the proposed control structure is better than a traditional PID controller. The robust stability of the sliding mode controller is proved by the Lyapunov's method. Experiments show its capability of reducing at least 20% amplitude of seat vibrations from 0.5 to 1 Hz.     

Adaptive neural control of high-order uncertain nonaffine systems: A transformation to affine systems approach

This brief investigates the adaptive neural network (NN) control of a class of high-order nonaffine nonlinear systems with completely unknown dynamics. Since the control terms appear within the unknown nonlinearity, traditional control schemes and stability analysis are usually rendered extremely complicated. Our main contribution includes a novel system transformation that converts the nonaffine system into an affine system through a combination of a low-pass filter and state transformation. As a result, the state-feedback control of the nonaffine system can be viewed as the output-feedback control of an affine system in normal form. The transformed system becomes linear with respect to the new input while the traditional backstepping approach is not needed thus allowing the synthesis to be extremely simplified. It is theoretically proven that all the signals in the closed-loop system are uniformly ultimately bounded (UUB). Simulation results are provided to demonstrate the performance of the developed controller.     

A virtual structure approach to formation control of unicycle mobile robots using mutual coupling

In this article, the formation control problem for unicycle mobile robots is studied. A distributed virtual structure control strategy with mutual coupling between the robots is proposed. The rationale behind the introduction of the coupling terms is the fact that these introduce additional robustness of the formation with respect to perturbations as compared to typical leader–follower approaches. The applicability of the proposed approach is shown in simulations and experiments with a group of wirelessly controlled mobile robots.     

A unifying theory of control dependence and its application to arbitrary program structures

There are several similar, but not identical, definitions of control dependence in the literature. These definitions are given in terms of control flow graphs which have had extra restrictions imposed (for example, end-reachability).We define two new generalisations of non-termination insensitive and non-termination sensitive control dependence called weak and strong control-closure. These are defined for all finite directed graphs, not just control flow graphs and are hence allow control dependence to be applied to a wider class of program structures than before.We investigate all previous forms of control dependence in the literature and prove that, for the restricted graphs for which each is defined, vertex sets are closed under each if and only if they are either weakly or strongly control-closed. Low polynomial-time algorithms for producing minimal weakly and strongly control-closed sets over generalised control flow graphs are given.This paper is the first to define an underlying semantics for control dependence: we define two relations between graphs called weak and strong projections, and prove that the graph induced by a set of vertices is a weak/strong projection of the original if and only if the set is weakly/strongly control-closed. Thus, all previous forms of control dependence also satisfy our semantics. Weak and strong projections, therefore, precisely capture the essence of control dependence in our generalisations and all the previous, more restricted forms. More fundamentally, these semantics can be thought of as correctness criteria for future definitions of control dependence.     

A new approach to model reduction of nonlinear control systems using smooth orthogonal decomposition

A new approach to model order reduction of nonlinear control systems is aimed at developing persistent reduced order models (ROMs) that are robust to the changes in system's energy level. A multivariate analysis method called smooth orthogonal decomposition (SOD) is used to identify the dynamically relevant modal structures of the control system. The identified SOD subspaces are used to develop persistent ROMs. Performance of the resultant SOD‐based ROM is compared with proper orthogonal decomposition (POD)–based ROM by evaluating their robustness to the changes in system's energy level. Results show that SOD‐based ROMs are valid for a relatively wider range of the nonlinear control system's energy when compared with POD‐based models. In addition, the SOD‐based ROMs show considerably faster computations compared to the POD‐based ROMs of same order. For the considered dynamic system, SOD provides more effective reduction in dimension and complexity compared to POD.     

A formal approach to perfective software maintenance: System integration using a basis of formal object-oriented components

We investigate how a formalism known as a basis and common to many areas of applied mathematics and engineering can be applied to perfective maintenance and the integration of application systems in software engineering, using an object-oriented approach. It is concluded that this formalism serves as a mathematical model for perfective software maintenance and software systems integration activities under object-oriented development. Theorems and properties about the model are reported as guides to software maintenance. The model and formal maintenance techniques have been applied to a software system in the management information systems area to demonstrate this approach to perfective maintenance and to assist in validating the model.     

A multi-level approach to investigate the control of an input device: application to a realistic pointing task

This study investigates the subjects' performance during realistic conditions of control of a joystick. An adapted reciprocal aiming task consisting in driving a virtual vehicle along a slalom course as fast as possible was performed while accuracy constraints were manipulated. Realistic dynamical Interface Screen Relationship between the joystick displacements and the displacements of the vehicle was simulated. Vehicle displacements and motor activity (muscle activity and joint kinematics) were recorded. The results highlighted the applicability of the Fitts' law to more realistic conditions where the use of an input device is performed in an intensive control situation. Besides, biomechanical results suggested that neuromuscular responses were different regarding the direction of movement, whereas the performance at a behavioural level were not affected. Thus, this study demonstrates the interest in considering two different aspects of the user's performance (behavioural and biomechanical ones) to make a better agreement between the device design and users' needs.