Distribution Of Control Signals Research Articles

Adaptive Fault-Tolerant Control of a Hybrid Canard Rotor/Wing UAV Under Transition Flight Subject to Actuator Faults and Model Uncertainties

This paper proposes an adaptive fault-tolerant control scheme for an over-actuated hybrid vertical take-off and landing (VTOL) canard rotor/wing unmanned aerial vehicle (UAV) to simultaneously compensate actuator faults and model uncertainties without the requirement of fault information and uncertain bounds. The proposed control scheme is constructed with two separate control modules. The high-level control module is developed with a novel adaptive sliding mode controller, which is employed to maintain the overall system tracking performance in both faulty and fault-free conditions. The low-level control allocation module is used to distribute the virtual control signals that are generated by the high-level control module among the available redundant actuators. In the case of actuator faults, the proposed adaptive scheme can seamlessly adjust the control parameters to compensate the virtual control error and reconfigure the distribution of control signals among the available redundant actuators. A significant feature of this study is that the stability of the closed-loop system is guaranteed theoretically in the presence of both actuator faults and model uncertainties and overestimation of the adaptive control parameters can be avoided. The effectiveness of the proposed control strategy is validated through comparative simulation tests under different faulty and uncertain scenarios.

Fast Quantum-Dot Cellular Automata Adder/Subtractor Using Novel Fault Tolerant Exclusive-or Gate and Full Adder

Quantum-dot Cellular automata is a promising area to implement digital systems at nano scale level. Adders and subtractors are widely used in almost every digital information processing system. This work targets to design an efficient 8-bit adder/subtractor that can perform addition as well as subtraction by using a novel control signal distribution scheme. To perform controlled inversion of inputs a novel exclusive-or gate with fewer cells is proposed. During Quantum-dot Cellular automata circuit fabrication, missing cell defects have the potential to affect the performance of a circuit. The proposed designs have higher fault resistance to missing cell defects compared to the existing state-of-the-art designs. Results demonstrate that the proposed design has (N-2) less clock phases compared to the existing state-of-the-art designs. The proposed design can be extended to implement any N-bit adder/subtractor. All the designs are designed and verified using coherence vector simulation engine in QCADesigner.

An Adaptive Fault-Tolerant Sliding Mode Control Allocation Scheme for Multirotor Helicopter Subject to Simultaneous Actuator Faults

This paper proposes a novel adaptive sliding-mode-based control allocation scheme for accommodating simultaneous actuator faults. The proposed control scheme includes two separate control modules with virtual control part and control allocation part, respectively. As a low-level control module, the control allocation/reallocation scheme is used to distribute/redistribute virtual control signals among the available actuators under fault-free or faulty conditions, respectively. In the case of simultaneous actuator faults, the control allocation and reallocation module may fail to meet the required virtual control signal, which will degrade the overall system stability. The proposed online adaptive scheme can seamlessly adjust the control gains for the high-level sliding mode control module and reconfigure the distribution of control signals to eliminate the effect of the virtual control error and maintain the stability of the closed-loop system. In addition, with the help of the boundary layer for constructing the adaptation law, the overestimation of control gains is avoided, and the adaptation ceases once the sliding variable is within the boundary layer. A significant feature of this study is that the stability of the closed-loop system is guaranteed theoretically in the presence of simultaneous actuator faults. The effectiveness of the proposed control scheme is demonstrated by experimental results based on a modified unmanned multirotor helicopter under both single and simultaneous actuator faults conditions with comparison to a conventional sliding mode controller and a linear quadratic regulator scheme.

A Simple Control Strategy Using Speedy Transient Response for Multiphase Buck Converter

The high performance of recent originating digital processors requires power supply for transient output, firm voltage regulation and high current. Industry has taken up interleaved multiphase synchronous buck converters for meeting such demands. Application of the voltage mode (ripple) hysteretic strategy to multiphase Voltage Regulator Units (VRU) would help satisfying many of the upcoming digital processors and IC’s powering demands. This arises from the use of the various advantages that can be obtained from this technique. This current division method is known for several benefits it provides: easy accessibility in application to all control methods, with freedom from the prime control technique in voltage regulation loop, absence of any necessity for current reference, better accuracy in current division of equal magnitude at almost every load conditions in standstill and transients. As against this, there are several challenges that involve distribution of multiple control signals, current sharing and sensitivity to noise, high speed comparators, hysteretic band accuracy and stable at large load transients. In addition, application of the current division technique presented was made to a multiphase voltage mode ripple controlled Buck Converter that produced a novel and easy control strategy having minimum output voltage ripples and speedy transient output.

Store-Carry-Cooperative Forward Routing with Information Epidemics Control for Data Delivery in Opportunistic Networks

Data delivery in opportunistic networks requires robustness and resiliency due to the mobility and probabilistic propagation channels caused by fading. Besides the 100% data delivery, delivery with minimum delay, overhead, buffer consumption, and controlling unnecessary transmissions/replications are equally important. In this paper, we propose a data delivery solution for opportunistic networks. The solution comprises two main algorithms: store-carry-cooperative forward routing and information epidemic control. In the data forwarding, nodes proactively monitor and exploit the direct/two-hop cooperative forwarding opportunities and adaptively switch between the cooperative forwarding and reactive store-carry-forward routing. An information epidemics control algorithm, which provides earlier control signal distribution time and faster recovery rate, is also proposed. The susceptible-infected-recovered model is used to study the effectiveness of the proposed mechanism. Extensive network performance evaluation is conducted under a wide range of scenarios, which include fading environments, obstacle-constrained environments, and mobile social network environments. We show that: 1) the information epidemics control mechanism provides higher vaccination rate and recovery rate; 2) proactive replication incurs a number of unnecessary transmissions; 3) monitoring the vicinity and exploiting the opportunity shorten the data delivery delay; and 4) with the integrated solution, a robust data delivery is achieved and a substantial amount of unnecessary transmissions are well deterred.

Optimal control of epidemic information dissemination over networks.

Information dissemination control is of crucial importance to facilitate reliable and efficient data delivery, especially in networks consisting of time-varying links or heterogeneous links. Since the abstraction of information dissemination much resembles the spread of epidemics, epidemic models are utilized to characterize the collective dynamics of information dissemination over networks. From a systematic point of view, we aim to explore the optimal control policy for information dissemination given that the control capability is a function of its distribution time, which is a more realistic model in many applications. The main contributions of this paper are to provide an analytically tractable model for information dissemination over networks, to solve the optimal control signal distribution time for minimizing the accumulated network cost via dynamic programming, and to establish a parametric plug-in model for information dissemination control. In particular, we evaluate its performance in mobile and generalized social networks as typical examples.

Observer-Based Fault Diagnosis Incorporating Online Control Allocation for Spacecraft Attitude Stabilization under Actuator Failures

This paper proposes a novel observer-based fault diagnosis method, incorporating an online control allocation scheme, for an orbiting spacecraft in the presence of actuator failures/faults, unexpected disturbances and input saturation. The proposed scheme solves a difficult problem in spacecraft fault tolerant control design by compensating for the loss in effectiveness and time-varying faults using redundant actuators, so that the overall system is stable, despite external disturbances and input saturation. This is accomplished by developing an observer-based fault diagnosis mechanism to reconstruct or estimate the actuator faults/failures. An online control allocation scheme is then used to redistribute the control signals to the healthy actuators in the case of faults/failures, without reconfiguring the controller, so that the control signal distribution is based on the reconstructed actuator effectiveness level. Simulation results using a rigid spacecraft model show good performance in the presence of faults, including total actuator failure scenarios, external disturbances and actuator input saturation, which validates the effectiveness and feasibility of the proposed scheme.

FF-EMU: a radiation tolerant ASIC for the distribution of timing, trigger and control signals in the CMS End-Cap Muon detector

A radiation tolerant integrated circuit for the distribution of clock, trigger and control signals in the Front-End electronics of the CMS End-Cap Muon detector has been developed in the IBM CMOS 130nm technology. The circuit houses transmitter and receiver interfaces to serial links implementing the FF-LYNX protocol that allows the integrated transmission of triggers and data frames with different latency constraints. Encoder and decoder modules associate signal transitions to FF-LYNX frames. The system and the ASIC architecture and behavior and the results of test and characterization of the ASIC prototypes will be presented.

A Fully Bidirectional Optical Network With Latency Monitoring Capability for the Distribution of Timing-Trigger and Control Signals in High-Energy Physics Experiments

The present paper discusses recent advances on a Passive Optical Network inspired Timing-Trigger and Control scheme for the future upgrade of the TTC system installed in the LHC experiments' and more specifically the currently known as TTCex to TTCrx link. The timing PON is implemented with commercially available FPGAs and 1-Gigabit Ethernet PON transceivers and provides a fixed latency gigabit downlink that can carry level-1 trigger accept decisions and commands as well as an upstream link for feedback from the front-end electronics.

FF-LYNX: protocol and interfaces for the control and readout of future Silicon detectors

The FF-LYNX protocol provides an innovative solution for the integrated distribution of Timing, Trigger and Control signals and the data readout in future High Energy Physics experiments. Transmitter and receiver interfaces implementing the FF-LYNX protocol have been simulated with a high-level simulator and in an FPGA based emulator. The design of the interfaces in a commercial CMOS technology as radiation tolerant and low power modules is ongoing and the submission of a test circuit is foreseen in fall 2010. The key features of the protocol are described in this paper as well as its possible application for the transmission from Silicon Trackers to trigger processors with short and constant latency of data to be used for the L1 trigger generation.

FF-LYNX: Fast and flexible electrical links for data acquisition and distribution of Timing, Trigger and Control signals in future High Energy Physics experiments

The FF-LYNX project aims at the definition of a flexible protocol that can handle both the distribution of Timing, Trigger and Control (TTC) signals and the data acquisition in future High Energy Physics (HEP) experiments. The implementation of this protocol in digital interfaces designed and produced in standard CMOS technologies (130 and/or 90 nm) and available as “IP cores” is also foreseen.

The COMPASS data acquisition system

A fully pipelined and massively parallel data acquisition system has been developed for the COMPASS experiment at CERN. The main requirements are to read 250000 detector channels at a trigger rate of up to 100 kHz. Such high rates are only possible when using a hit selection mechanism on the front-end combined with dead-time free readout. For this purpose, a time-to-digital converter (TDC) chip has been developed and is used for all time measurement applications in COMPASS. Distributed, field programmable gate array (FPGA)-based readout-driver modules handle parallel front-end initialization, synchronous trigger and control-signal distribution, and local event building at a processing speed of 160 Mbyte/s. Each of the 160 readout-driver modules connects to 16 front-end boards through independent twisted pair cables (CAT 7, 600 MHz) or optical fibers using an industrial (ESCON), self synchronizing link at 40 Mbyte/s. Automatic configuration through unique module and link identification ensures the flexibility and scalability to very large detector systems. The preprocessed data are transmitted through optical fibers at 160 Mbyte/s to the master event building system. Here global event building is realized on high-performance personal computers (PCs) and Gigabit ethernet network components. The complete events are sent to the central data recording at the CERN main site at an average rate of 40 Mbyte/s and stored in an object oriented database. A reduced system was set up for the commissioning run of COMPASS in 2000. Operation of the full system starts in July 2001.

The clock and control signal distribution system for the NA48 experiment

In the NA48 experiment at CERN, several detector subsystems located at distances of up to 200 m between each other produce data on a continuous basis and feed them into pipelines. Triggers are produced after variable delay times by two different systems for charged and for all-neutral kaon decays. To allow the retrieval of the corresponding data from the various subsystems and their merging into complex events by means of timestamps, a special, highly stable global clock distribution system has been developed. The design principles and the setup of the clock system are described and results for clock stability monitoring and automated correction of the signal transmission speed are reported.

Improved control signal distribution for very wide VLSI data buses

A new technique for distributing electronic signals by way of a conducting path across large spatial distances with minimal temporal dispersion is presented. It provides for the delivery of a common signal to any number of different receivers located along the signal path, with near zero skew and little degradation of the signal's rise/fall transition times. The method involves the placement of an active routing structure in parallel with, and appropriately strapped to, a conventional passive conductor. The concept is demonstrated in the paper, within the context of VLSI design, by a solution to the problem of distributing an on-chip control signal to the many lines of a physically very wide data bus.

A gallium-arsenide digital phase shifter for clock and control signal distribution in high-speed digital systems

The design, implementation, testing, and applications of a gallium-arsenide digital phase shifter and fan-out buffer are described. The integrated circuit provides a method for adjusting the phase of high-speed clock and control signals in digital systems, without the need for pruning cables, multiplexing between cables of different lengths, delay lines, or similar techniques. The phase of signals distributed with the described chip can be dynamically adjusted in eight different steps of approximately 60 ps per step. The IC also serves as a fan-out buffer and provides 12 in-phase outputs. The chip is useful for distributing high-speed clock and control signals in synchronous digital systems, especially if components are distributed over a large physical area or if there is a large number of components. >

Optical beam forming techniques for phased array antennas

Following an outline of established optical techniques for the generation and distribution of reference and control signals for phased array antennas, two novel approaches are put forward: (i) a ‘nondispersive prism’, controlling agile single beams or monopulse patterns, and (ii) a ‘lens fed model array’, which can control multiple, independent antenna beams. The prospects of fibre-optic transmission for other functions in the array are also considered.

Easily reconfigurable VLSI sorter

An easily reconfigurable VLSI sorter is presented and a run-time reconfiguration scheme to tolerate faults is proposed. The scheme maintains the original data flow pattern by bypassing defective cells with bypass registers. A control signal distribution technique is developed to make the sorting algorithm work even for an array containing some bypass registers. An on-line fault diagnosis algorithm for this reconfigurable sorter is presented. Reconfiguration is carried out in a distributed fashion.

A high-speed GaAs MESFET optical controller

Optical interconnects are being considered for control signal distribution in phased array antennas. A packaged hybrid GaAs optical controller with a 1:16 demultiplexed output that is suitable for this application is described. The controller, which was fabricated using enhancement/depletion mode MESFET technology, operates at demultiplexer-limited input data rates up to 305 Mb/s and requires less than 200 mu W optical input power.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On Controllability and Finity Control of Distributed Systems

The paper is devoted to controllability (observability) of distributed systems.For illustration, an oscillating string is considered subjected to control as a force concentrated in some internal point „a”. In addition to some obvious uncontrollability points (nodes of natural space modes of the string) there are less obvious irrational uncontrollability points (in the class of the so-called generalized functions of slow growth)One example of an irrational uncontrollability point are Loui- ville points. The controllability and uncontrollability points are described in terms of diophantine approximations of numbers, Qualitatively, controllability points are those which have a “poor” and uncontrollability points those which have a “good” diophantine approximation. In this respect, quadratic irrationalities which have the worst diophantine approximation are “the best” controllability points. All these results are formulated and proven in a sequence of theorems. In particular, controllability points are shown to add up to a complete measure.All these results are extended to the case of arbitrary distribution of control signals along the definition range of the plant, either uni- or multi-dimensional.

A Large-Scale Digitizer System (Lsd) for Charge and Time Digitization in High-Energy Physics Experiments

A large-scale digitizer (LSD) system for acquiring charge and time-of-arrival particle data from high-energy-physics experiments has been developed at the Lawrence Berkeley Laboratory. The objective in this development was to significantly reduce the cost of instrumenting large-detector arrays which, for the 4π-geometry of colliding-beam experiments, are proposed with an order of magnitude increase in channel count over previous detectors. In order to achieve the desired economy (~ $65 per channel), a system was designed in which a number of control signals for conversion, for digitization, and for readout are shared in common by all the channels in each 128-channel bin. This paper describes the overall-system concept, and the distribution of control signals that are critical to the 10-bit charge resolution and to the 12-bit time resolution. Also described is the bit-serial transfer scheme, chosen for its low component and cabling costs.