Networks and Computers
Introduction
The nees@berkeley lab is served by several gigabyte ethernet networks and numerous computers for capturing and transporting data. Here we mean data in the largest sense, encompassing numeric data gathered from transducer-type instrumentation, as well as photographs, videos, and audio. Figure 1 is a diagram showing the overall relationship of the networks and computers. In the following sections, we discuss the services and the dataflows represented in the figure, as well as other services available in the lab.
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| Figure 1 — Diagram of Networks and Computers at nees@berkeley. This diagram shows the main networks in the lab along with the computers on those networks. |
Let's examine this figure and break it into understandable pieces. Near the center is the bare word “Experiment”. This represents the experimental specimen located in the lab. Surrounding the specimen, are elements labeled
- Instruments
- represents the transducer-type instruments connected to the specimen.
- Actuators
- represents the actuators connected to the specimen.
- IMAQ Cameras:
- represents image acquisition (IMAQ) cameras pointed at the specimen.
- Telepresence Cameras
- represents network cameras pointed at the specimen or the general lab floor.
At the top and bottom of Figure 1, are blue lines that represent the two main gigabit ethernet networks serving the lab. The top one we call the “video” network as mostly image data is sent through them. The bottom one we call the “data” network as mostly numeric data is sent through them. On the right is a gigabit ethernet network that connects the lab to main campus backbone. (Actually there are redundant facilities connecting the Richmond Field Station to the main campus backbone.) The main campus backbone then connects to the public internet and to the higher-speed Internet 2, a network that includes various universities and other research facilities in the nation.
The video and data networks connect to the outside world via the two nees@berkeley servers. These Linux servers provide the lab services available to the public and to researchers and act as firewalls for the other computers in the lab. One is the Telepresence Server on the video network, which mainly runs the FlexTPS application. The other is the NEESPOP on data network which runs the Data Turbine application. Both these servers are also Tier 2 NTP time servers for the rest of the lab computers and equipment. Also associated with the servers are about 4 terabytes of RAID storage.
The instruments are connected to our Pacific Instruments DAQ controller, a real-time computer with electronics that condition the electrical signals and digitize the voltage. The DAQ controller is connected to a dedicated MS-Windows workstation which provides a graphical user interface (GUI) to configure and operate the DAQ. The data collected by the DAQ is placed on the SCRAMNet network and is collected into files on the MS-Windows GUI workstation.
The actuators at our site are controlled by one of two MTS systems. We have both FlexTest and Structural Test System (STS) system controllers. Each of those controllers is connected to its own dedicated MS-Windows workstation which provides a graphical user interface (GUI) to configure and operate the controller and actuators. Additionally, the STS controller is also connected to the SCRAMNet network. On the SCRAMNet, the STS controller can read instructions and write results. This capability enables the STS to interact with simulations for hybrid simulation experiments. Figure 1 depicts the STS system only, as it shows the controller connects to the SCRAMNet network.
The red oval outline is the SCRAMNet shared-memory ring network. This is the real heart and soul of our hybrid simulation capability and it enables other services, too. For computers connected to the SCRAMNet, applications can extend their address space (memory) to include the memory on the SCRAMNet card. SCRAMNet works in the background to update every card's memory after any node writes to memory. In this way SCRAMnet provides a shared-memory capability. The DAQ and the STS controller are both nodes on the SCRAMNet. Several workstations are also nodes, and with one exception, those workstation nodes are for simulation. The one exception is a workstation node used for streaming DAQ data.
Telepresence
The lab's telepresence capabilities consist of
Live streaming of videos captured by network cameras and available to clients on request (using a web browser) via the FlexTPS application.
Live synchronized streaming of data captured by the DAQ with telepresence video, and available to clients on request (using the Real-Time Data Viewer) via the Data Turbine application.
Teleconferencing with the Webex Service.
Teleconferencing with a Polycom Video Conferencing System.
Pioneer P-3 Robot.
Live Video and FlexTPS
The streaming video provided with the network cameras and the FlexTPS application is the most-used telepresence application here at the lab. The telepresence cameras (upper left corner of Figure 1) are mostly Axis network cameras. These cameras send motion JPEG (MJPEG) to the FlexTPS application on the Telepresence server. The FlexTPS application serves the MJPEG streams to clients who connect with web browsers.
Those same streams may also be captured by the AxisSource application running on the Telepresence Server and sent to the Data Turbine application on the NEES-POP, where the images may be seen synchronized with numeric data from the DAQs.
Streaming DAQ Data and the Data Turbine
DAQ data is sent to the Data Turbine application on the NEES-POP by means of the SCRAMNet and the computer and application we call “SCRAMNet DAQ”.
The SCRAMNet DAQ computer is a Linux system with SCRAMNet card. A locally developed application, “scramnetdaq” (based on the NEES diagnostic application “fake-daq”), reads the DAQ channels on the SCRAMNet. It provides that information to the NEES-POP “daq2rbnb” client application. In turn, the “daq2rbnb” application is the Data Turbine source for the DAQ data.
Researchers and others can connect to the Data Turbine using the NEES Real-Time Data Viewer (RDV) application.
Moreover, using the AxisSource application on the Telepresence server, the Data Turbine can additionally receive the telepresence motion JPEG (MJPEG) streams. Users can run the client application RDV to receive synchronized data and image streams, and view those streams simultaneously.
Teleconference: Webex Service
For teleconferencing, we mostly use the NEES subscription to the Webex service. We have several Logitech Quickcam Pro web cameras that can be attached to computers to provide video.
Teleconference: Polycom Teleconference System
The lab has a Polycom VSX 7000 system connected to a public gigabyte ethernet network in the lab. (not shown in Figure 1). There are a number of small PC Polycom units at the lab also. These enable users to connect with Polycom equipment in other facilities or to other PCs with the PC Polycom units.
Although Polycom video conferencing was much used in the early years of the NEES project (especially the construction phase), it is largely superceded by the Webex service, now.
ActivMedia Peoplebot Robot
The lab has a ActivMedia Peoplebot Robot equipped with a camera. It can be controlled remotely to move about the lab. It uses a private wireless network for operation. These are not shown in Figure 1.
The current functionality is limited, but we hope to improve it, soon. One of the next improvements is adding a laser pointer to the robot.
Hybrid Simulation
In summary, hybrid simulation uses a combination of simulations and physical experiments to determine the seismic response of a structure. In particular, the simulations and physical parts interact through feedback of displacements and forces from the physical to the virtual and specification of next-step target displacements and forces from the virtual to the physical. In our lab, this communication is enabled through the SCRAMNet shared memory network.
The Simulink Host machine is a MS-Windows workstation. Typically it runs Mathworks MatLab and Simulink software. Most often it acts as the host for the “xPC” workstation. This system may also run the actual simulation, or, in the case of a remote simulation, this machine acts as an intermediary between the simulation and the application on the “xPC” workstation.
The Simulink Target machine is a workstation that runs Mathworks xPC real-time operating system. This OS is quite primitive and does not feature a fully interactive user interface. One controls the “xPC” through another host computer, typically we use the Simulink Host machine. This communication runs through a crossover ethernet cable. The application we run on the Simulink Target host is a sophisticated predictor-corrector application. This application receives periodic displacement or force targets from a simulation and it sends feedback information to the simulation. The application also sends information to the MTS controller to increment towards the target at the periodicity of the controller. The MTS controller periodicity is much faster than that of the simulation and this predictor-corrector application fills in the gaps to keep the MTS controller moving appropriately. In our setup, the xPC does all the communication with the MTS controller.The OpenSees Simulation computer is a MS-Windows workstation running the OpenSees simulation software. It is connected to the SCRAMNet and it communicates with the predictor-corrector application on the xPC target host through the SCRAMNet. Although it doesn't directly command the MTS controller (we want to use the predictor-corrector application running on the “xPC” workstation), it gets the MTS controller feedback directly through the SCRAMNet and it communicates to the “xPC” workstation through the SCRAMNet, too. Like the Simulink Host, one may actually run the simulation here, or one may run the simulation remotely and communicate (get feedback, specify targets) with this host.
Image Acquisition System (IMAQ)
The lab provides an image acquisition system for capturing still and video images, as well as applications for processing those images.
Image Acquisition
The IMAQ cameras include firewire cameras that can be used in video and still image modes as well as DVR camcorders that capture TV and HDTV images. This image capture system is not designed for streaming images to the internet in near real-time. This system is designed for capturing images that are analyzed sometime after the event.
The firewire cameras connect to computers and capture images (still or video) directly to computer hard disk drives. The camcorders capture images and audio to miniDV tapes. After the experiment, the tapes are played and the multimedia data is captured onto hard disk drives. Typically the files are collected onto the RAID associated with the video editing computers for image processing.
Video Editing
The lab has two high-end computers, one a MS-Windows workstation and one a G5 (PowerPC) Macintosh workstation, along with about 4 terabytes of RAID, for use in video editing. Besides the standard on-board facilities of the two operating systems (eg, Movie Maker for Windows and iMovie for Apple), the machines host several high-end still-image and video applications.
The MS-Windows workstation has
Adobe Photoshop.
National Instruments Diadem Clip for synchronizing previously captured streams of data and images.
The Macintosh has
Adobe Photoshop.
Apple Final Cut Pro for editing video.
Apple DVD Studio Pro for creating DVDs.
Macromedia (now Adobe) Studio MX for an integrated web development tool set, including the the applications Dreamweaver, Flash, Fireworks, and FreeHand.
Real Viz Stitcher for combining still images into a wider panorama.
Real Viz Image Modeler for analyzing still images and creating a 3D computer model.
AirBears Wireless Network
The lab is also equipped with an 802.11b wireless network that is part of the main campus AirBears wireless network (not shown in Figure 1). Guests at the lab may use this network for email and web surfing. Although one needs a school ID to login and get access to the network, anyone with a school ID may create “guest passes” for visitors to use for a period of up to a week.
