Real-time Control Experiments Research Articles

A Kalman filter approach to virtual sensing for active noise control

Local active noise control systems aim to produce zones of quiet at a number of desired locations within a sound field, such as the ears of an observer. The resulting zones of quiet are usually centred at the error sensors, and are often too small to extend from the error sensors to the observer's ears. To overcome these problems, virtual sensing methods have been suggested. These methods are based on estimating the error signals at a number of locations remote from the physical locations of the error sensors. By minimising the estimated error signals, the zones of quiet can be moved away from the error sensors to the locations where noise control is desired, i.e. the virtual locations. In this paper, the active noise control problem under consideration is analysed using a state-space model of the plant. Kalman filtering theory is then used to develop a virtual sensing algorithm that computes optimal estimates of the error signals at the virtual locations. The developed algorithm is implemented on an acoustic duct arrangement, and the real-time estimation performance at a virtual location inside the acoustic duct is analysed. Furthermore, the developed algorithm is combined with the filtered-x LMS, and the results of real-time broadband feedforward control experiments at the virtual location are presented.

Neural-optimal control algorithm for real-time regulation of in-line storage in combined sewer systems

Attempts at implementing real-time control systems as a cost-effective means of minimizing the pollution impacts of untreated combined sewer overflows have largely been unsustained due to the complexity of the real-time control problem. Optimal real-time regulation of flows and in-line storage in combined sewer systems is challenging due to the need for complex optimization models integrated with urban stormwater runoff prediction and fully dynamic routing of sewer flows within 5–15 min computational time increments. A neural-optimal control algorithm is presented that fully incorporates the complexities of dynamic, unsteady hydraulic modeling of combined sewer system flows and optimal coordinated, system-wide regulation of in-line storage. The neural-optimal control module is based on a recurrent Jordan neural network architecture that is trained using optimal policies produced by a dynamic optimal control module. The neural-optimal control algorithm is demonstrated in a simulated real-time control experiment for the King County combined sewer system, Seattle, Washington, USA. The algorithm exhibits an effective adaptive learning capability that results in near-optimal performance of the control system while satisfying the time constraints of real-time implementation.

Food Science Education Publications and Websites

Bird We invite readers to submit print or electronic resources that they would like to share with other readers. Please submit the full text of the articles or the URL for the website and an annotation of not more than 100 words. We welcome your comments and resources. Material should be submitted to: Jim Bird, Science & Engineering Center, Fogler Library, Univ. of Maine, Orono, ME 04469 or e-mailed to Jim.Bird@umit.maine.edu. CRIS Current Research Information System. USDA. Available at http://cris.csrees.usda.gov/ (accessed 8/18/2006) CRIS includes a searchable database of ongoing or recently completed projects supported by grants from the USDA. Users can search the database by an assisted search interface that includes a fill-in form or by a professional search that utilizes Boolean operators and field-directed commands. A detailed classification code system can be used with both search interfaces. Each record includes performing institution and principal investigator(s); a brief description of the funded project, giving objectives, approach, and progress; and a list of publications that have resulted from the research. There are also a CRIS pending projects database and a database of multistate projects. Hooker, P. 2005. Mineral analysis of whole grain total cereal. J Chem Ed 82(8):1223-5. The author describes an experiment that was implemented in the chemistry curriculum at Westminster College, Salt Lake City, Utah. The procedure for iron, calcium, and zinc analysis is discussed. Supplementary information, including instructor notes, is available in this issue of Journal of Chemical Education online (subscription required). Laminack, J, Dainello, F, Vestal, TA, Wingenbach, G. 2006. Experiential education employed to demystify food irradiation as a viable technology for food industry professionals. HortTechnology 16(2):318-23. The authors describe a professional development short course for food industry personnel and extension agents. Focusing on the course effectiveness, the article includes information on participants' perceptions, knowledge and understanding, and levels of concern about food safety and irradiation. The authors note that the short course increased food safety knowledge among participants as well as changing perceptions and attitudes. Lemar, L, Haytowitz, D, Bingham, M, Cutrufelli, R, and Thomas, R. 2006. The Nutrient Data Laboratory web site gets a new look. J Food Comp Analysis 19:S96-9. This paper describes the redesigned Nutrient Data Laboratory (NDL) web site (http://www.ars.usda.gov/ba/bhnrc/ndl (last updated 7/26/2006). Through this site users can access the USDA National Nutrient Database for Standard Access (release 18), the full text of articles (1996–present) by NDL staff as well as poster sessions and presentations, and a current list of research programs and projects. Riverol, C, Andrade, S, and Cooney, J. 2005. A laboratory course on real-time control for food engineers. Int J Eng Ed 21(4):668-75. The authors describe a laboratory course that utilizes real-time control experiments focusing on fuzzy control. It is noted that this laboratory course is preceded by a 1-year course titled “Application of Artificial Intelligent [sic] (AI) in Food Processing.” MATLAB software is used for laboratory experiments. Distance learning is briefly discussed, as is student feedback. Taylor, A and Sajan, S. 2005. Testing for genetically modified foods using PCR. J Chem Ed 82(4):597-8. The authors describe an experiment that can be used in biochemistry or analytical chemistry courses. Using PCR, students evaluate “…commercially-available cornmeal products for the presence of the CaMV 35S promoter… ” (p.597). This is a 2-week experiment that also includes a case study on genetically modified foods. Supplementary information, including instructor notes and the case study, is available in this issue of Journal of Chemical Education online (subscription required). University of Nebraska, Lincoln. Center for Science, Mathematics, & Computer Education. Food science labs. http://scimath.unl.edu/labs/food.html (accessed 8/14/2006) The experiments listed on the site are appropriate for high school science classes and are the result of a grant for the inclusion of food experiments in science classes. Contributors include Nebraska science teachers and others. A contact e-mail is given for comments on the experiments. Included are experiments on digestive enzymes, DNA isolation from an onion, chromatography, vitamin C analysis, and food microbes.

Real-time measurement and control at JET signal processing and physics analysis for diagnostics

To meet the requirements of the scientific programme, the EFDA JET real-time measurement and control project has developed an integrated set of real-time plasma measurements, experiment control and communication facilities. Traditional experiments collected instrument data during the plasma pulse and calculated physics data after the pulse. The challenge for continuous tokamak operation is to calculate the physics data in real-time, keeping up with the evolution of the plasma. In JET, many plasma diagnostics have been augmented with extra data acquisition and signal-processing systems so that they can both capture instrument data for conventional post-pulse analysis and calculate calibrated, validated physics results in real-time. During the pulse, the systems send sampled data sets into a network, which distributes the data to several destinations. The receiving systems may do further analysis, integrating data from several measurements, or may control the plasma scenario by heating or fuelling. The simplest real-time diagnostic systems apply scale factors to the signals, as with the electron cyclotron emission (ECE) diagnostic's 96 tuned radiometer channels, giving the electron temperature profile. In various spectroscopy diagnostics, spectral features are least-squares-fitted to measure spectra from several lines of sight, within 50 ms. Ion temperatures and rotation speed can be calculated from the line widths and shifts. For diagnostics using modulation techniques, the systems implement digital-signal processing phase trackers, lock-in amplifiers and filters, e.g., the far infrared (FIR) interferometer samples 15 channels at 400 kHz for 30 s, i.e., six million samples per second. Diagnostics have specific lines of sight, spatial channels, and various sampling rates. The heating/fuelling systems have relatively coarse spatial localisation. Analysis systems have been developed to integrate the basic physics data into smaller sets of controllable parameters on a common geometry, e.g., temperature, density and safety factor profiles with values at 10 points of normalised radius. The EFDA real-time project is essential groundwork for future reactors such as ITER, and has successfully involved many scientific and technical staff from several institutions. The facility is now frequently used in experiments.

Real-time measurement and control at JET experiment control

Abstract Over the past few years, the preparation of ITER-relevant plasma scenarios has been the main focus of experimental activity on tokamaks. The development of integrated, simultaneous, real-time controls of plasma shape, current, pressure, temperature, radiation, neutron profiles and also impurities, ELMs and MHD are now seen to be essential for further development of quasi-steady state conditions with feedback, or the stabilisation of transient phenomena with event-driven actions. For this thrust, the EFDA JET Real-Time Project has developed a set of real-time plasma measurements, experiment control and communication facilities. The plasma diagnostics used for real-time experiments are Far Infra Red interferometry, polarimetry, visible, UV and X-ray spectroscopy, LIDAR, bolometry, neutron and magnetics. Further analysis systems produce integrated results, such as temperature profiles on geometry derived from MHD equilibrium solutions. The actuators include toroidal, poloidal and divertor coils, gas and pellet fuelling, neutral beam injection, radio frequency (ICRH) waves and microwaves (LH). The heating/fuelling operators can either define a power or gas request waveform or select the real-time instantaneous power/gas request from the real-time experiment central control (RTCC) system. The real-time experiment control system provides both a high-level, control-programming environment and interlocks with the actuators. A MATLAB facility is being developed for the development of more complex controllers. The plasma measurement, controller and plant control systems communicate in ATM network. The EFDA Real-Time Project is essential groundwork for future reactors such as ITER. It involves many staff from several institutions. The facility is now frequently used in experiments. This work has been conducted under the European Fusion Development Agreement and is partly funded by Euratom and the UK Engineering and Physical Sciences Research Council.

Description of a Modeling, Simulation, Animation, and Real-Time Control (MoSART) Environment for a Class of Electromechanical Systems

This paper describes an Interactive Modeling, Simulation, Animation, and Real-Time Control (MoSART) Environment that is useful for controls education and research. The described MoSART environment is shown to be useful for analyzing, designing, visualizing, and evaluating control systems for a class of cart-pendulum electromechanical systems. The environment-referred to as Cart-Pendulum Control3D-Lab-is based on Microsoft Windows, Visual C++, Direct-3D, and MATLAB/Simulink. The environment can be used as a stand-alone application or together with MATLAB, Simulink, and toolboxes. When used as a stand-alone application, a friendly graphical user interface permits easy interaction. Users may select (via pull-down menus) systems, dynamical models, control laws, exogenous signals (including joystick inputs) and associated parameters, initial conditions, integration routines, and associated parameters. When used with MATLAB, Simulink, and toolboxes, the previously mentioned nominal features are significantly enhanced. In either case, the interface permits users to access the following (via pull-down menus): animation models, mesh properties, texture and lighting models, system-specific visual indicators, graphics to be displayed, animation/data display/storage rates, simulation control buttons, and extensive documentation. When Simulink is present, users can exploit extensive visualization and three-dimensional (3-D) animation features through provided and/or user-generated Simulink diagrams. This capability makes the developed environment very extensible with respect to mathematical models and control laws. In addition, users may readily export simulation data to MATLAB/toolboxes for postprocessing and further analysis. The environment also contains a suite of well-documented (easy-to-modify) models and control laws that are implemented within the provided Simulink block diagrams. Provided (special) blocks enable animation, joystick inputs, and (near) real-time simulation and animation (when possible). (Near real-time-or faster-than-real-time-simulation and animation are possible whenever the mathematical and animation models are sufficiently simple and data manipulation requirements, e.g. storage and display, are sufficiently mild. For the systems considered, (near) real-time simulation and animation is readily achievable.) Associated with each block diagram are system-specific, menu-accessed m-files that permit detailed analysis and design. A hardware module permits real-time control of actual hardware experiments. The developed environment is shown to be a valuable tool for enhancing both controls education in a variety of classes as well as research. Examples are presented to illustrate the utility of the environment.

Webshaker: Live internet shake-table experiment for education and research

Internet technologies are employed to allow real-time video monitoring, control, and execution of bench-top shake-table experiments. Structural models of relevance to education in dynamics and earthquake engineering can be tested remotely over the internet on a 24-h, 7-day (24/7) basis. The underlying elements of experiment tele-observation and tele-operation/control are incorporated in a newly developed website http://webshaker.ucsd. edu. © 2005 Wiley Periodicals, Inc. Comput Appl Eng Educ 13: 99–110, 2005; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20034

On-Line Educational Shake Table Experiments

Internet technologies are employed to allow real-time video monitoring, control, and execution of bench-top shake table experiments. Structural models of relevance to education in dynamics and earthquake engineering can be tested remotely over the Internet at any time. The underlying elements of experiment tele-observation and tele-operation/control are incorporated in a newly developed Web site. Tools for graphical display and analysis of recorded model response are included. Related education evaluation and assessment materials are prepared and made available on-line. The Web site currently provides an experimental component in courses such as earthquake engineering and structural dynamics. Based on a developed education assessment framework and the compiled student feedback, the Web site is found to be useful and effective. From this feedback, most students rated their experience as equivalent to the usual hands-on laboratory experiment. Similar applications in other areas of science and engineering will bring valuable experimentation content directly into the classroom, with efficient use of time and resources and the convenience of anywhere/anytime access.

Real-time robotics and process control experiments in the Distributed Control Lab

The Distributed Control Lab (DCL) provides an open infrastructure for conducting robotics and control experiments over the Internet. It is based on web services technologies and offers a wide range of frontend applications. Within the DCL environment work is focused on safety strategies and mechanisms in order to prevent malicious code from damaging experimental equipment. These include source code analyses, .NET code access security, runtime observation and the dynamic replacement of faculty control algorithms. The .NET framework provides a solid base for a safe execution of user code in the lab. In the Lego .NET experiment work is focused on making the Microsoft .NET run-time available for the DCL Lego Mindstorm robot experiment. A frontend for the GNU Compiler Collection (GCC) has been implemented that translates ECMA intermediate language into native code. This strategy allows the extension of the concept of code access security to embedded devices. Within the paper an overview of the DCL's architecture is presented and the frontends implemented, including a Visual Studio .NET plug-in, are introduced. The installed experiments are introduced and case studies of implemented techniques to ensure their and the DCL's safety are described.

Integrated scenario in JET using real-time profile control

The recent development of real-time measurements and control tools in JET has enhanced the reliability and reproducibility of the relevant ITER scenarios. Diagnostics such as charge exchange, interfero-polarimetry, electron cyclotron emission have been upgraded for real-time measurements. In addition, real-time processes like magnetic equilibrium and q profile reconstruction have been developed and applied successfully in real-time q profile control experiments using model based control techniques. Plasma operation and control against magnetohydrodynamic instabilities are also benefiting from these new systems. The experience gained at JET in the field of real-time measurement and control experiments operation constitutes a very useful basis for the future operation of ITER scenarios.

Periodic Tension Disturbance Attenuation in Web Process Lines Using Active Dancers

This paper investigates the role of active dancers in attenuation of web tension disturbances in a web process line. A general structure of the active dancer is considered; governing equations for web spans upstream and downstream to the dancer roller are developed. A structural limitation that facilitates efficient design of the active dancer system for web tension disturbance attenuation is derived and discussed based on the developed model. An open-architecture experimental web platform is developed for conducting real-time control experiments using the active dancer system. The active dancer system model is experimentally identified using the standard system identification techniques available in literature. Three types of control designs were investigated for the active dancer system: a proportional-integral-derivative controller, an internal model based controller, and a linear quadratic optimal controller. Data collected from a series of experiments using the three control designs validate the usefulness of the active dancers in attenuating web tension disturbances in a web process line. A representative sample of the experimental data is presented and discussed.

A virtual laboratory environment for real-time experiments

A virtual laboratory is a computing system that allows to share the physical resources available in a laboratory with remote users connected on the internet. This paper describes a particular virtual laboratory environment for running real-time robot control experiments over the internet through a standard web browser. Using the proposed approach, a remote user can connect to the virtual lab, run a control experiment on a physical robot device, change the control parameters. and interact with the real-time system to receive the desired state information. The robotic application considered in this paper is a ball balancer, a two-degrees-of-freedom rotating plate that has to be controlled to keep a ball in a desired location. Ball position and speed are detected by vision, through a fixed CCD camera.

Cost-oriented virtual reality and real-time control system architecture

In this paper the use of inexpensive standard hardware and software is proposed in place of high-cost commercial solutions to set up real-time control experiments with a human in the control loop, including graphical and haptic virtual reality (VR). For this purpose a generic simulation environment for the implementation of control experiments using VR with haptic feedback and their evaluation, has been developed. As an example, setups of a car simulator with a human in the control loop and an inverted pendulum as an experiment for student laboratories are presented.

Alstom selected for Canadian hydro plant

An application of a multivariable state-space adaptive controller to a turbo-generator set is considered in this paper. The turbo-generator, consisting of an air pressure turbine and a synchronous generator, is a typical electromechanical system, which exhibits highly nonlinear behaviour and non-negligible couplings between electrical and mechanical control loops. Especially if the plant is not connected to the rigid 50 Hz grid, the control task for varying load in different operating points is quite difficult. Great fluctuations of the central pressure pump cause the turbo-generator to work in a noisy environment as well. The parameters of the state-space model are identified directly using the recursive prediction error algorithm, which estimates also the system states. Based on the estimated parameters and states, the adaptive controller is determined through state feedback. The optimal control strategy is comissioned for designing the state controller. The results of real-time control experiments of the turbo-generator demonstrate the feature and applicability of the designed multivariable state-space adaptive controller.

Diagnostics System of JT-60U

The diagnostic system of JT-60U (JT-60upgrade) is composed of about 50 individual diagnostic devices. Recently, the detailed radial profile measurements of plasma parameters have been improved, so that the internal structure of plasmas could be explored. The understanding of plasma confinement has been enhanced by density and temperature fluctuation measurements using a mm-wave reflectometer and electron cyclotron emission measurements, respectively. In addition, real-time control experiments of electron density, neutron yield, radiated power, and electron temperature gradient have been carried out successfully by corresponding diagnostic devices. These measurements and the real-time control contribute to improving plasma performance. Diagnostic devices for next generation fusion devices such as a CO2 laser interferometer/polarimeter and a CO2 laser collective Thomson scattering system have been developed.

Novel active noise-reducing headset using earshell vibration control.

Active noise-reducing (ANR) headsets are available commercially in applications varying from aviation communication to consumer audio. Current ANR systems use passive attenuation at high frequencies and loudspeaker-based active noise control at low frequencies to achieve broadband noise reduction. This paper presents a novel ANR headset in which the external noise transmitted to the user's ear via earshell vibration is reduced by controlling the vibration of the earshell using force actuators acting against an inertial mass or the earshell headband. Model-based theoretical analysis using velocity feedback control showed that current piezoelectric actuators provide sufficient force but require lower stiffness for improved low-frequency performance. Control simulations based on experimental data from a laboratory headset showed that good performance can potentially be achieved in practice by a robust feedback controller, while a single-frequency real-time control experiment verified that noise reduction can be achieved using earshell vibration control.

Real-Time linux dynamic clamp: a fast and flexible way to construct virtual ion channels in living cells.

We describe a system for real-time control of biological and other experiments. This device, based around the Real-Time Linux operating system, was tested specifically in the context of dynamic clamping, a demanding real-time task in which a computational system mimics the effects of nonlinear membrane conductances in living cells. The system is fast enough to represent dozens of nonlinear conductances in real time at clock rates well above 10 kHz. Conductances can be represented in deterministic form, or more accurately as discrete collections of stochastically gating ion channels. Tests were performed using a variety of complex models of nonlinear membrane mechanisms in excitable cells, including simulations of spatially extended excitable structures, and multiple interacting cells. Only in extreme cases does the computational load interfere with high-speed "hard" real-time processing (i.e., real-time processing that never falters). Freely available on the worldwide web, this experimental control system combines good performance. immense flexibility, low cost, and reasonable ease of use. It is easily adapted to any task involving real-time control, and excels in particular for applications requiring complex control algorithms that must operate at speeds over 1 kHz.

Design of a new remote control system for microgravity facilities on board the international space station: preliminary results

The paper deals with the preliminary design of a new system for Telescience operations of microgravity experimentation on-board the International Space Station. The system represents an innovative implementation of new telecommunication system that combined with on-board computer, is able to provide complementary link between the investigator on-ground and the facilities on-board. This new concept is aimed to carry out the following tasks: • to reduce as much as possible the period of loss of the signal, so as to guarantee an almost continuous and real-time control of the experiment; • to reduce the complexity of the network which routes the signal from ISS to the Investigator and vice versa; • to simplify the access procedure to the scientific payloads. In order to obtain such results the system has been designed to be operated with the existing commercial telecommunication satellites for mobile users. The selection of these platforms imposed the utilisation of low bit rate channels, that, however, using data extraction techniques, are compliant with large part of the planned experiments. This scenario has been defined also taking into account a comparative analysis of the possible constellation suitable for this utilisation. A major problem due to the installation on a space platform of a transponder conceived for Earth mobile users is the magnitude and the rate of Doppler shift between the platform and the satellites of the constellation. The required modifications to the transponder have been analysed and a solution is proposed. Utilisation of low bit rate channels represents a strong constraint for data stream, since for a certain number of microgravity experiments the most relevant information is carried in video images. A video link, on the other hand, is an extremely demanding resource, often not available during the complete mission, but only during very limited periods of coverage. From these considerations stems the idea to implement on-board a system able to extract most significant scientific information from experiment images and to transmit only this information over the link (available during all the mission time). In addition, other systems on-ground receive the data and are able to reconstruct a “virtual” image on the basis of the extraction algorithm used. In this paper, techniques that can be applied to this process of “video information extraction” are analysed and discussed. As a test case two algorithms of data extraction from video images of Fluid Science experiments have been developed, together with the on-ground reconstruction software. The algorithms have been tested using images of an experiment carried out during Spacelab LMS mission and the results obtained are presented. Their implementation has shown that this system is suitable for the real-time experiment control, also taking into account that the scientific images can be stored on-board and analysed post-flight for a more accurate scientific evaluation.

A Portable and Low-Cost System for Real-Time Digital Control

A portable and low-cost system which provides the flexibility for working adults, who are attending a part-time course, to perform real-time digital control experiments anywhere and anytime is presented. Advantages of the proposed system are high-lighted and typical results of real-time case studies are discussed.

Sensor/Actuator Optimal Design for Active VibrationControl of Shell Structure

In this paper, a distributed sensor and actuator are designed for the active vibration control of shell structure. To prevent the adverse effect of spillover, distributed modal sensorlactuator system is established by optimizing the electrode pattern and the lamination angle of polyvinylidene fluoride (PVDF). Finite element programs are developed to consider the curved structures integrated with PVDF sensor and actuator. The nine-node Mindlin shell element is used for finite element discretization. The electrode pattern and the lamination angle of PVDF sensor/actuator are optimized using genetic algorithm. The sensor is designed to minimize the observation spillover. and actuator is designed to minimize the system energy of the control modes under a given initial condition. For the verification of the design, numerical simulation and real-time vibration control experiment ofthe integrated smart structure are performed using discrete LQG method as the control law. A singly curved cantilevered smart shell structure integrated with distributed modal sensor/actuator for the suppression of the first and second modes is manufactured for the experiment. The vibration suppressions of control modes are successfully achieved as expected.