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We present a monolithic technique for simultaneous mode and polarization control in oxide-confined VCSELs using a locally etched sub-wavelength surface grating. A single-fundamental mode emission with an SMSR>30 dB and an OPSR~20 dB is achieved over the entire operational current range, with a maximum output power of 4.1 mW
One of the most important factors in building high-performance, scalable industrial control applications is the ability to transfer process data from the server to the client machine in the most efficient and fast way. OPC DA is widely accepted and used as the standard in automation and network control systems. We present a system and method for caching process data in large industrial control systems...
The developer of logic control systems is faced with increasing complexity of the functions to be implemented and, at the same time, increasing demands on the reliability of the resulting software. To analyze the reliability of such complex systems formal methods can be applied. One area of the corresponding research is focused on the application of model checking techniques to Programmable Logic...
Expectations for the near future of factory automation indicate that the amount of sensors can be greatly improved within affordable costs. The complexity that is today still manageable with traditional concepts will call for new models to maintain control over complex systems and gain maximum information from redundant sensory input. This paper proposes an artificial recognition system that is oriented...
The paper presents a layered architecture for real-time surveillance systems. Each layer includes objects that model the "real world" at a specific abstraction level, from raw data up to domain concepts. Each layer performs abstractions on perceptions coming from the lower layer and formulates timed hypotheses about domain objects. The failure of a hypothesis causes a perception to flow...
This paper describes an improved approach to design a Takagi-Sugeno zero-order type fast parameterized digital fuzzy logic controller (DFLC) processing only the active rules (rules that give a non-null contribution for a given input data set), at high frequency of operation, without significant increase in hardware complexity. To achieve this goal, an improved method of designing the fuzzy controller...
The paper introduces a new event-based criterion for discrete representations of continuous-time signals, which can be used in intelligent sensors to report the current state of the observed object. The criterion is based on the control of the sampling error energy. The analytic approximation of the mean sampling rate for a given sampling resolution is derived. The formula for the reduction of sampling...
In this paper we deal with the problem of determining a set of decentralized controllers for P/T nets that are able to impose a given global specification on the net behaviour. More precisely, both the global specification and the decentralized specifications are given in terms of generalized mutual exclusion constraints (GMECs) thus the controllers take the form of monitor places. In this paper we...
In this paper we consider a quantized discrete-time linear quadratic regulator (DLQR) problem, namely a DLQR problem where the input u may only take values in a given finite set 14. Eased on our previous results on the optimal control of hybrid systems we show that the optimal control law for the quantized DLQR problem takes the form of a feedback control law, that can be obtained from a partition...
Today there is a significant body of results of resource management in real-time systems. However, most of them are based on "open-loop" strategies and techniques that do not take into account application demands to dynamically adjust their behavior. To overcome this problem by focusing on control applications, we show a novel scheduling technique: large error first (LEF). This scheduling...
This paper presents the planned and on-going activities inside the FORDESIGN research project, funded by the Portuguese FCT (Foundation for Science and Technology), whose main objective is to foster the effective use of formal methods for embedded systems co-design. The project proposes a methodology where the use-cases are used as a starting point, not only for capturing requirements but also to...
The introduction of the workflow management provided companies with a flexible and robust approach to the supervision and execution of the business process. A further question that must be addressed is to help companies in the reuse of already developed workflows, thus saving investments and reducing time-to-market. This paper proposes a methodology aiming at providing reuse and modularity for production...
This paper presents the TinyCAN, a resource constrained controller area network controller implemented in VHDL language. The core description is fully synthesizable and fits in a FPGA-based platform occupying a maximum of 366 look-up tables. An enhanced error control strategy was elaborated with the aim of producing a more suitable behavior for safety-critical applications. For all that, compatibility...
This paper describes the design and implementation of a CAN time-triggered based communication protocol named SCoCAN, (shared channel on CAN), intended for use in distributed control systems, as is the case of autonomous mobile robots. This protocol enables real time communication between different intelligent nodes (sensors, actuators and controllers). The SCoCAN protocol has been implemented in...
This paper presents the implementation of two digital sinusoidal PWMs (DSPWMs) using a low-cost 8-bit micro-controller. Each DSPWM is implemented using two different PWM hardware modes on the micro-controller. The benefits and limitations of each DSPWM are investigated in relation to the switching frequency and micro-controller performance from experimental verification using a 2 kVA single-phase...
The management of ad-hoc networks raises interesting problems, that are particularly challenging for networks of mobile nodes. Considering the inherent complexity of these systems, the development of distributed applications relying on wireless communication protocols would be greatly simplified by the use of specific tools for supporting testing and step-by-step debugging. In this paper we describe...
The object of this research is to design and prototype a linear/rotary ultrasonic motor based upon multi-mode resonance behaviors for a piezoelectrically excited driver structure system. The whole ultrasonic motor system includes a pair of piezoactuator-equipped driver rods, a linear/rotary driven shaft, and a set of high-voltage power stages for energizing the piezoelectric stacks. The linear/rotary...
Measurements of human physiological data allow inferring information on the mental and emotional state of a human. An increasing number of application developers and scientists of different domains want to make use of this additional information on users. To be accepted in practical application, systems of this sort have to be easy to use, should not intrude the user by wires, and it should be easy...
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