Protecting mobile code in the world

Proposed applications for mobile code systems include autonomous shopping agents, autonomic systems, distributed sensor network applications, and interstellar space networks. I argue the case for mobile code systems as the next-generation distributed programming paradigm and discuss the security problems that must be addressed before this vision is practically realizable. The security discussion will focus on protecting mobile code programs that execute in the wild from malicious actions by remote hosts.     

基于移动传感器/执行器网络的时滞分布参数系统镇定控制

考虑一类基于移动传感器/执行器网络具有状态时滞的分布参数系统,在系统中加入扰动因子,分析移动传感器/执行器的动力学行为,研究系统出现扰动时如何设计反馈控制器和移动控制力.首先利用无穷维抽象发展方程理论将时滞分布参数系统在Hilbert空间中进行方程演变;其次,结合工程实际应用进行合理的假设以便于问题的解决;接着利用算子半群理论,通过Lyapunov稳定性定理证明系统的状态在反馈控制器的作用下能够趋于稳态,且系统在移动控制力的作用下渐近稳定;最后,通过数值仿真实验表明所设计控制策略的有效性.     

Ethernet based time synchronization for Raspberry Pi network improving network model verification for distributed active turbulent flow control

Friction drag primarily determines the total drag of transport systems. A promising approach to reduce drag at high Reynolds numbers(> 104) are active transversal surface waves in combination with passive methods like a riblet surface. For the application in transportation systems with large surfaces such as airplanes, ships or trains, a large scale distributed real-time actuator and sensor network is required. This network is responsible for providing connections between a global flow control and distributed actuators and sensors. For the development of this network we established at first a small scale network model based on Simulink and True Time. To determine timescales for network events on different package sizes we set up a Raspberry Pi based testbed as a physical representation of our first model. These timescales are reduced to time differences between the deterministic network events to verify the behavior of our model. Experimental results were improved by synchronizing the testbed with sufficient precision. With this approach we assure a link between the large scale model and the later constructed microcontroller based real-time actuator and sensor network for distributed active turbulent flow control.     

Simultaneous On-Chip Sensing and Actuation Using the Thermomechanical In-Plane Microactuator

Many applications in microelectromechanical systems require physical actuation for implementation or operation. On-chip sensors would allow control of these actuators. This paper presents experimental evidence showing that a certain class of thermal actuators can be used simultaneously as an actuator and a sensor to control the actuator's force or displacement output. By measuring the current and voltage supplied to the actuator, a one-to-one correspondence is found between a given voltage and current and a measured displacement or force. This integrated sensor/actuator combination will lead to efficient on-chip control of motion for applications including microsurgery, biological cell handling, and optic positioning.     

Model-driven engineering of planning and optimisation algorithms for pervasive computing environments

This paper presents a model-driven approach to developing pervasive computing applications that exploits design-time information to support the engineering of planning and optimisation algorithms that reflect the presence of uncertainty, dynamism and complexity in the application domain. In particular, the task of generating code to implement planning and optimisation algorithms in pervasive computing domains is addressed.We present a layered domain model that provides a set of object-oriented specifications for modelling physical and sensor/actuator infrastructure and state-space information. Our model-driven engineering approach is implemented in two transformation algorithms. The initial transformation parses the domain model and generates a planning model for the application being developed that encodes an application’s states, actions and rewards. The second transformation parses the planning model and selects and seeds a planning or optimisation algorithm for use in the application.We present an empirical evaluation of the impact of our approach on the development effort associated with two pervasive computing applications from the Intelligent Transportation Systems (ITS) domain, and provide a quantitative evaluation of the performance of the algorithms generated by the transformations.     

Type-specialized staged programming with process separation

Staging is a powerful language construct that allows a program at one stage of evaluation to manipulate and specialize a program to be executed at a later stage. We propose a new staged language calculus, ??ML??, which extends the programmability of staged languages in two directions. First, ??ML?? supports dynamic type specialization: types can be dynamically constructed, abstracted, and passed as arguments, while preserving decidable typechecking via a System F_??-style semantics combined with a restricted form of ?? _?? -style runtime type construction. With dynamic type specialization the data structure layout of a program can be optimized via staging. Second, ??ML?? works in a context where different stages of computation are executed in different process spaces, a property we term staged process separation. Programs at different stages can directly communicate program data in ??ML?? via a built-in serialization discipline. The language ??ML?? is endowed with a metatheory including type preservation, type safety, and decidability as demonstrated constructively by a sound type checking algorithm. While our language design is general, we are particularly interested in future applications of staging in resource-constrained and embedded systems: these systems have limited space for code and data, as well as limited CPU time, and specializing code for the particular deployment at hand can improve efficiency in all of these dimensions. The combination of dynamic type specialization and staging across processes greatly increases the utility of staged programming in these domains. We illustrate this via wireless sensor network programming examples.     

Interrupt Verification via Thread Verification

Most of the research effort towards verification of concurrent software has focused on multithreaded code. On the other hand, concurrency in low-end embedded systems is predominantly based on interrupts. Low-end embedded systems are ubiquitous in safety-critical applications such as those supporting transportation and medical automation; their verification is important. Although interrupts are superficially similar to threads, there are subtle semantic differences between the two abstractions. This paper compares and contrasts threads and interrupts from the point of view of verifying the absence of race conditions. We identify a small set of extensions that permit thread verification tools to also verify interrupt-driven software, and we present examples of source-to-source transformations that turn interrupt-driven code into semantically equivalent thread-based code that can be checked by a thread verifier. Finally, we demonstrate a proof-of-concept program transformation tool that converts interrupt-driven sensor network applications into multithreaded code, and we use an existing tool to find race conditions in these applications.     

A Recurrent Neural-Network-Based Sensor and Actuator Fault Detection and Isolation for Nonlinear Systems With Application to the Satellite's Attitude Control Subsystem

This paper presents a robust fault detection and isolation (FDI) scheme for a general class of nonlinear systems using a neural-network-based observer strategy. Both actuator and sensor faults are considered. The nonlinear system considered is subject to both state and sensor uncertainties and disturbances. Two recurrent neural networks are employed to identify general unknown actuator and sensor faults, respectively. The neural network weights are updated according to a modified backpropagation scheme. Unlike many previous methods developed in the literature, our proposed FDI scheme does not rely on availability of full state measurements. The stability of the overall FDI scheme in presence of unknown sensor and actuator faults as well as plant and sensor noise and uncertainties is shown by using the Lyapunov's direct method. The stability analysis developed requires no restrictive assumptions on the system and/or the FDI algorithm. Magnetorquer-type actuators and magnetometer-type sensors that are commonly employed in the attitude control subsystem (ACS) of low-Earth orbit (LEO) satellites for attitude determination and control are considered in our case studies. The effectiveness and capabilities of our proposed fault diagnosis strategy are demonstrated and validated through extensive simulation studies.     

Optimizing the performance of sensor network programs through estimation-based code profiling

With the development of sensor technology and embedded systems, building large-scale, low-cost sensor networks, which is a critical step to facilitating the application of pervasive sensing in the future, becomes possible. One of the major challenges in developing sensor network applications is to improve the execution efficiency of programs running on power-constrained embedded devices. While profiling-guided code optimization has been widely used as a compiler-level optimization technique for improving the performance of programs running on general-purpose computers, it has not been applied to sensor network programs due to some defects. In this paper, we overcome these defects and design a more effective profiling-guided code placement approach for sensor network programs. Specifically, we model the execution of sensor network programs taking nondeterministic inputs as discrete-time Markov processes, and propose a novel approach named Code Tomography to estimate parameters of the Markov models that reflect sensor network programs’ dynamic execution behaviors by only using end-to-end timing information measured at the start and end points of each procedure in the source code. The parameters estimated by Code Tomography are fed back to compilers to optimize the code placement. The evaluation results demonstrate that Code Tomography can achieve satisfactory estimation accuracy with low profiling overhead and the branch misprediction rate can be reduced after reorganizing the code placement based on the profiling results. Besides, Code Tomography can also be useful for purposes such as post-mortem analysis, debugging and energy profiling of sensor network programs.     

Secrets to success and fatal flaws: the design of large-display groupware

Research in the field of large-display groupware applications has yet to yield a killer app, a common look and feel for applications, or a set of broadly applicable design principles. It's therefore difficult to understand what constitutes a successful large-display groupware application and what affects their adoption. Although large-display groupware faces many of the same adoption and use challenges as conventional desktop groupware, how people perceive and interact with large-display groupware yields some unique challenges. We've built and evaluated several large-display groupware systems that address various workgroups, functions, and environments. This experience has given us broad expertise regarding the social dynamics and technical challenges surrounding large-display groupware's design. To enhance our understanding of these challenges, we've also undertaken a broad survey of existing large-display groupware systems to understand how their purpose, design, and deployment affect the success of their integration into everyday tasks and practices.     

State-centric programming for sensor-actuator network systems

Distributed embedded systems such as wireless sensor and actuator networks require new programming models and software tools to support the rapid design and prototyping of sensing and control applications. Unlike centralized platforms and Web-based distributed systems, these distributed sensor-actuator network (DSAN) systems are characterized by a massive number of potentially failing nodes, limited energy and bandwidth resources, and the need to rapidly respond to sensor input. We describe a state-centric, agent-based design methodology to mediate between a system developer's mental model of physical phenomena and the distributed execution of DSAN applications. Building on the ideas of data-centric networking, sensor databases, and proximity-based group formation, we introduce the notion of collaboration groups, which abstracts common patterns in application-specific communication and resource allocation. Using a distributed tracking application with sensor networks, we'll demonstrate how state-centric programming can raise the abstraction level for application developers.     

一种动态无线传感网络操作系统－SOS

无线传感器网络节点,在一般用途的系统和嵌入式系统里都有自己的特点。有时必须在能源很少并且环境比较恶劣的情况下工作,同时还提供共同服务,使它很容易编写应用程序。在当前流行的无线传感网络操作系统TinyOs下,虽然各个组件可以互相提供共同服务,但是每个传感器节点必须单独的运行一个静态的系统镜像,所以很难满足多维应用的系统或者频繁的应用更新。SOS,一种从设计上更考虑动态性的更适合微型节点的操作系统应运而生。它由一个公共的内核和模块组成,它有自己的消息机制．动态内存机制,可以动态加载和动态卸载模块,以及其他的一些服务。然而模块之间是通过一个相互的预定协作机制相互联系的．没有内存的保护。但是尽管如此,SOS通过一系列自己的手段有效的克服了这些缺点,比如看门狗定时器,垃圾回收系统等等。相互独立的模块之间,可以通过最小的系统终端来添加或者删除。通过对比,虽然SOS是动态设计并且使用了更高的内核接口．但是跟TinyOs相比,总的使用开销却是基本一样的。SOS是基于模块化的,容易编程。TinyOS是基于组件化,效率高。而MantisOS可以支持多线程,但是代码占用空间大。由此可以看到,SOS是一个具有自己的特点和优势的无线传感网络操作系统。     

ZigBee2006协议栈的无线传感执行网络构建

无线传感执行网络是智能空间的重要组成部分。本文应用TI/Chipcon公司免费提供的ZigBee2006协议栈,以CC2430无线单片机为控制器,构建家庭无线传感执行网络,为执行器操作传送温度、湿度、光照等环境数据。实验结果表明,该系统能够达到检测环境的任务要求,且成本低,性能可靠稳定,在智能空间、智能家居等领域具有良好的应用前景。     

Sensor9k : A testbed for designing and experimenting with WSN-based ambient intelligence applications

Ambient Intelligence systems are typically characterized by the use of pervasive equipment for monitoring and modifying the environment according to users’ needs, and to globally defined constraints.Our work describes the implementation of a testbed providing the hardware and software tools for the development and management of AmI applications based on wireless sensor and actuator networks, whose main goal is energy saving for global sustainability. A sample application is presented that addresses temperature control in a work environment, through a multi-objective fuzzy controller taking into account users’ preferences and energy consumption.     

基于WSAN的道路积水监控系统的设计与实现

强降雨及城市排水系统的老化,使得城市道路低洼处积水严重,对市民人身安全、财产、路基、城市交通产生不容忽视的影响;针对该问题,采用无线传感器/执行器网络(WSAN)技术,设计了道路积水监控系统;该系统分为传感/执行层、网络层和应用层三层;传感/执行层的传感器节点使用超声波传感器采集积水信息,执行器节点使用执行器水泵进行排水;网络层网关及汇聚节点使用ZigBee网络和GPRS网络相结合来实现传感/执行层与应用层之间的数据双向传输;应用层服务器储存采集的道路积水信息,调用百度地图API将实时信息显示在web端,并通过网络层发送指令控制积水区域内的执行器水泵动作,实现闭环控制;该系统能够简洁有效地实现道路积水信息的实时共享,可以实现及时排水,具有实际的应用价值。     

Accessible Ultrasonic Positioning

A positioning system's design must account for several aspects of usability, most of which are determined by the application the system supports. The development of inexpensive, easy-to-use positioning technology simplifies the deployment of location-based applications. To explore the ubiquitous positioning systems' design space we use the term accessibility, which encompasses all aspects of usability. We've at tempted to address several of these aspects in the design of ultrasonic positioning systems. Our solutions score better in some categories than in others, but our approach has enabled us to design and install more than 20 systems for use in permanent and temporary applications     

Passivity-based control of nonlinear flexible multibody systems

In this paper, global asymptotic stability of a class of nonlinear multibody flexible space structures under certain dissipative compensation is established. Furthermore, for an important subclass of such systems, the stability is shown to be robust to certain types of actuator and sensor nonlinearities. The results are applicable to robust stabilization of a wide class of systems, including flexible space structures and manipulators with articulated flexible appendages. The stability proofs use the Lyapunov approach and exploit the inherent passivity of such systems     

VIBRATION CONTROL OF A SMART STRUCTURE USING PERIODIC OUTPUT FEEDBACK TECHNIQUE

Active vibration control is an important problem in structures. One of the ways to tackle this problem is to make the structure smart, adaptive and self‐controlling. The objective of active vibration control is to reduce the vibration of a system by automatic modification of the system's structural response. This work features the modeling and design of a Periodic Output Feedback (POF) control technique for the vibration control of a smart flexible cantilever beam system for a Single Input Single Output case. A POF controller is designed for the beam by bonding patches of piezoelectric layer as sensor/actuator to the master structure at different locations along the length of the beam. The entire structure is modeled in state space form using the Finite Element Method by dividing the structure into 3, 4, 5 elements, thus giving rise to three types of systems, viz., system 1 (beam divided into 3 finite elements), system 2 (4 finite elements), system 3 (5 finite elements). POF controllers are designed for the above three types of systems for different sensor/actuator locations along the length of the beam by retaining the first two vibratory modes. The smart cantilever beam model is developed using the concept of piezoelectric bonding and Euler‐Bernouli theory principles. The effect of placing the sensor/actuator at various locations along the length of the beam for all the three types of systems considered is observed and the conclusions are drawn for the best performance and for the smallest magnitude of the control input required to control the vibrations of the beam. The tip displacements with the controller is obtained. Performance of the system is also observed by retaining the first 3 vibratory modes and the conclusions are drawn.     

Bioinspired Engineering of Exploration Systems: A Horizon Sensor/Attitude Reference System Based on the Dragonfly Ocelli for Mars Exploration Applications

Bioinspired engineering of exploration systems (BEES) is a fast emerging new discipline. It focuses on distilling the principles found in successful, nature‐tested mechanisms of specific crucial functions that are hard to accomplish by conventional methods, but are accomplished rather deftly in nature by biological organisms. The intent is not just to mimic operational mechanisms found in a specific biological organism but to imbibe the salient principles from a variety of diverse organisms for the desired crucial function. Thereby, we can build exploration systems that have specific capabilities endowed beyond nature, as they will possess a mix of the best nature‐tested mechanisms for each particular function. Insects (for example, honey bees and dragonflies) cope remarkably well with their world, despite possessing a brain that carries less than 0.01% as many neurons as ours does. Although most insects have immobile eyes, fixed focus optics, and lack stereo vision, they use a number of ingenious strategies for perceiving their world in three dimensions and navigating successfully in it. We are distilling some of these insect‐inspired strategies for utilizing optical cues to obtain unique solutions to navigation, hazard avoidance, altitude hold, stable flight, terrain following, and smooth deployment of payload. Such functionality can enable access to otherwise unreachable exploration sites for much sought‐after data. A BEES approach to developing autonomous flight systems, particularly in small scale, can thus have a tremendous impact on autonomous airborne navigation of these biomorphic flyers particularly for planetary exploration missions, for example, to Mars which offer unique challenges due to its thin atmosphere, low gravity, and lack of magnetic field. Incorporating these success strategies of bioinspired navigation into biomorphic sensors such as the horizon sensor described herein fulfills for the first time the requirements of a variety of potential future Mars exploration applications described in this paper. Specifically we have obtained lightweight (～6 g), low power (<40 mW ), and robust autonomous horizon sensing for flight stabilization based on distilling the principles of the dragonfly ocelli. Such levels of miniaturization of navigation sensors are essential to enable biomorphic microflyers (<1 kg) that can be deployed in large numbers for distributed measurements. In this paper we present the first experimental test results of a biomorphic flyer platform with an embedded biomorphic ocellus (the dragonfly‐inspired horizon sensor/attitude reference system). These results from the novel hardware implementation of a horizon sensor demonstrate the advantage of our approach in adapting principles proven successful in nature to accomplish navigation for Mars exploration. © 2003 Wiley Periodicals, Inc.     

网络化控制系统中新型控制方法的研究

网络化控制系统的出现,正成为新的热点,减少网络带宽的占用,是网络化控制系统的研究中一个十分令人关注的问题,探讨了如何减少在传感器和控制器之间,减少状态数据包传输的方法。设计了一个能使系统稳定的新型结构的控制器和一个特殊的网络传输规则。