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- A scalable and efficient approach for obtaining measurements in CAN-Based control systemsPublication . Andersson, Björn; Pereira, Nuno; Elmenreich, Wilfried; Tovar, Eduardo; Pacheco, Filipe; Cruz, NunoThe availability of small inexpensive sensor elements enables the employment of large wired or wireless sensor networks for feeding control systems. Unfortunately, the need to transmit a large number of sensor measurements over a network negatively affects the timing parameters of the control loop. This paper presents a solution to this problem by representing sensor measurements with an approximate representation-an interpolation of sensor measurements as a function of space coordinates. A priority-based medium access control (MAC) protocol is used to select the sensor messages with high information content. Thus, the information from a large number of sensor measurements is conveyed within a few messages. This approach greatly reduces the time for obtaining a snapshot of the environment state and therefore supports the real-time requirements of feedback control loops.
- A microscope for the data centerPublication . Pereira, Nuno; Tennina, Stefano; Loureiro, João; Severino, Ricardo; Saraiva, Bruno; Santos, Manuel; Pacheco, Filipe; Tovar, EduardoNowadays, data centers are large energy consumers and the trend for next years is expected to increase further, considering the growth in the order of cloud services. A large portion of this power consumption is due to the control of physical parameters of the data center (such as temperature and humidity). However, these physical parameters are tightly coupled with computations, and even more so in upcoming data centers, where the location of workloads can vary substantially due, for example, to workloads being moved in the cloud infrastructure hosted in the data center. Therefore, managing the physical and compute infrastructure of a large data center is an embodiment of a Cyber-Physical System (CPS). In this paper, we describe a data collection and distribution architecture that enables gathering physical parameters of a large data center at a very high temporal and spatial resolution of the sensor measurements. We think this is an important characteristic to enable more accurate heat-flow models of the data center and with them, find opportunities to optimize energy consumptions. Having a high-resolution picture of the data center conditions, also enables minimizing local hot-spots, perform more accurate predictive maintenance (failures in all infrastructure equipments can be more promptly detected) and more accurate billing. We detail this architecture and define the structure of the underlying messaging system that is used to collect and distribute the data. Finally, we show the results of a preliminary study of a typical data center radio environment.
- Networked embedded systems for active flow control in aircraftPublication . Tovar, Eduardo; Pereira, Nuno; Bate, Iain; Indrusiak, Leandro; Penna, Sérgio; Negrão, José; Viana, Júlio C.; Philipp, François; Mayer, Dirk; Heras, José; Pacheco, Filipe; Loureiro, JoãoAerodynamic drag is known to be one of the factors contributing more to increased aircraft fuel consumption. The primary source of skin friction drag during flight is the boundary layer separation. This is the layer of air moving smoothly in the immediate vicinity of the aircraft. In this paper we discuss a cyber-physical system approach able of performing an efficient suppression of the turbulent flow by using a dense sensing deployment to detect the low pressure region and a similarly dense deployment of actuators to manage the turbulent flow. With this concept, only the actuators in the vicinity of a separation layer are activated, minimizing power consumption and also the induced drag.
- Highly scalable aggregate computations in cyber-physical systems: physical environment meets communication protocolsPublication . Tovar, Eduardo; Andersson, Björn; Pereira, Nuno; Alves, Mário; Prabh, K. Shashi; Pacheco, FilipeIn this paper, we focus on large-scale and dense Cyber- Physical Systems, and discuss methods that tightly integrate communication and computing with the underlying physical environment. We present Physical Dynamic Priority Dominance ((PD)2) protocol that exemplifies a key mechanism to devise low time-complexity communication protocols for large-scale networked sensor systems. We show that using this mechanism, one can compute aggregate quantities such as the maximum or minimum of sensor readings in a time-complexity that is equivalent to essentially one message exchange. We also illustrate the use of this mechanism in a more complex task of computing the interpolation of smooth as well as non-smooth sensor data in very low timecomplexity.
- Using a prioritized MAC protocol to execute the database operation join in networked embedded computer systemsPublication . Andersson, Björn; Pereira, Nuno; Tovar, Eduardo; Pacheco, FilipeDatabase query languages on relations (for example SQL) make it possible to join two relations. This operation is very common in desktop/server database systems but unfortunately query processing systems in networked embedded computer systems currently do not support this operation; specifically, the query processing systems TAG, TinyDB, Cougar do not support this. We show how a prioritized medium access control (MAC) protocol can be used to efficiently execute the database operation join for networked embedded computer systems where all computer nodes are in a single broadcast domain.
- Integration of TCP/IP and PROFIBUS protocolsPublication . Pereira, Nuno; Pacheco, Filipe; Pinho, Luís Miguel; Prayati, A.; Nikoloutsos, E.; Kalogeras, A.; Hintze, E.; Adamczyk, H.; Rauchhaupt, L.Recent technological developments are pulling fieldbus networks to support a new wide class of applications, such as industrial multimedia applications. These applications are usually supported by the widely used TCP/IP stack. It is thus essential to provide support to TCP/IP based applications, in fieldbus networks. This paper presents an effort that is being carried out to integrate the TCP/IP and PROFIBUS stacks, in order to support industrial multimedia applications, whilst guarantying the timing requirements of control-related traffic.
- Supporting internet protocols in master-slave fieldbus networksPublication . Pacheco, Filipe; Tovar, Eduardo; Kalogeras, A.; Pereira, NunoIn this paper we describe how to integrate Internet Protocols (IP) into a typical hierarchical master-slave fieldbus network, supporting a logical ring token passing mechanism between master stations. The integration of the TCP/IP protocols in the fieldbus protocol rises a number of issues that must be addressed properly. In this paper we particularly address the issues related to the conveyance of IP fragments in fieldbus frames (fragmentation/de-fragmentation) and on how to support the symmetry inherent to the TCP/IP protocols in fieldbus slaves, which lack communication initiative.
- Industrial multimedia put into practicePublication . Pacheco, Filipe; Pereira, Nuno; Marques, B.; Machado, Sandra; Marques, Luís; Pinho, Luís Miguel; Tovar, EduardoRecent developments in the factory floor technologies together with the widespread use of TCP/IP and the Internet are increasing the eagerness to support a new wide class of devices and applications, such as industrial multimedia applications, in factory floor networks. This paper presents how this new field of applications can be put into practice, via a manufacturing cell field trial being implemented. This manufacturing automation field trial involves the use of traditional distributed computer control systems and 'factory-floor-oriented' multimedia (e.g. voice, video) application services.
- A high performance wireless fieldbus in industrial multimedia-related environmentPublication . Alves, Mário; Tovar, Eduardo; Pacheco, Filipe; Ferreira, Luís; Pereira, Nuno; Machado, Sandra; Brandão, VeríssimoThis paper summarises the most important solutions that have emerged from the work carried out by our team within the framework of the EU (IST-1999-11316) project RFieldbus - High Performance Wireless Fieldbus in Industrial Multimedia-Related Environment. Within this project, Profibus was chosen as the fieldbus platform. Essentially, extensions to the current Profibus standard are being developed in order to provide Profibus with wireless, mobility and industrialmultimedia capabilities. In fact, providing these extensions means fulfilling strong requirements, namely to encompass the communication between wired (currently available) and wireless/mobile devices and to support real-time control traffic and multimedia traffic in the same network.