Neural Feedback Scheduling of Real-Time Control Tasks

Many embedded real-time control systems suffer from resource constraints and dynamic workload variations. Although optimal feedback scheduling schemes are in principle capable of maximizing the overall control performance of multitasking control systems, most of them induce excessively large computational overheads associated with the mathematical optimization routines involved and hence are not directly applicable to practical systems. To optimize the overall control performance while minimizing the overhead of feedback scheduling, this paper proposes an efficient feedback scheduling scheme based on feedforward neural networks. Using the optimal solutions obtained offline by mathematical optimization methods, a back-propagation (BP) neural network is designed to adapt online the sampling periods of concurrent control tasks with respect to changes in computing resource availability. Numerical simulation results show that the proposed scheme can reduce the computational overhead significantly while delivering almost the same overall control performance as compared to optimal feedback scheduling.Comment: To appear in International Journal of Innovative Computing, Information and Contro

Fuzzy Feedback Scheduling of Resource-Constrained Embedded Control Systems

The quality of control (QoC) of a resource-constrained embedded control system may be jeopardized in dynamic environments with variable workload. This gives rise to the increasing demand of co-design of control and scheduling. To deal with uncertainties in resource availability, a fuzzy feedback scheduling (FFS) scheme is proposed in this paper. Within the framework of feedback scheduling, the sampling periods of control loops are dynamically adjusted using the fuzzy control technique. The feedback scheduler provides QoC guarantees in dynamic environments through maintaining the CPU utilization at a desired level. The framework and design methodology of the proposed FFS scheme are described in detail. A simplified mobile robot target tracking system is investigated as a case study to demonstrate the effectiveness of the proposed FFS scheme. The scheme is independent of task execution times, robust to measurement noises, and easy to implement, while incurring only a small overhead.Comment: To appear in International Journal of Innovative Computing, Information and Contro

Control-theoretic dynamic voltage scaling for embedded controllers

For microprocessors used in real-time embedded systems, minimizing power consumption is difficult due to the timing constraints. Dynamic voltage scaling (DVS) has been incorporated into modern microprocessors as a promising technique for exploring the trade-off between energy consumption and system performance. However, it remains a challenge to realize the potential of DVS in unpredictable environments where the system workload cannot be accurately known. Addressing system-level power-aware design for DVS-enabled embedded controllers, this paper establishes an analytical model for the DVS system that encompasses multiple real-time control tasks. From this model, a feedback control based approach to power management is developed to reduce dynamic power consumption while achieving good application performance. With this approach, the unpredictability and variability of task execution times can be attacked. Thanks to the use of feedback control theory, predictable performance of the DVS system is achieved, which is favorable to real-time applications. Extensive simulations are conducted to evaluate the performance of the proposed approach.Comment: Accepted for publication in IET Computers and Digital Techniques. doi:10.1049/iet-cdt:2007011

A facile route to encapsulate ultrasmall Ni clusters within the pore channels of AlPO-5

A simple one-step method to encapsulate Ni (II) into the pore channels of AlPO-5 molecule sieve was developed by using nickel-amine complexes as templating agent for synthesis of Ni(deta)2-AlPO-5. The Ni (II) occluded in the pores can be directly reduced by reducing gases in situ generated from the decomposition of nickel-amine complexes in AlPO-5 during heat treatment. The resulted catalyst has ultra-small Ni clusters highly dispersed into the pore channels, showing a high selectivity for 1,2-propanediol in the hydrogenolysis of glycerol

Tris(ethyl­enediamine)zinc(II) hexa­fluorido­silicate

The title compound, [Zn(C2H8N2)3](SiF6), was synthesized ionothermally using choline chloride–imidazolidone as solvent and template provider. In the crystal structure, the anions and cations are located on special positions of site symmetry 3.2 and show a typical octa­hedral geometry. The ZnII ion is coordinated by six N atoms from three ethyl­enediamine mol­ecules. The crystal structure displays weak hydrogen bonding between [SiF6]2− anions and the ethyl­enediamine NH hydrogen atoms

Cross-Layer Adaptive Feedback Scheduling of Wireless Control Systems

There is a trend towards using wireless technologies in networked control systems. However, the adverse properties of the radio channels make it difficult to design and implement control systems in wireless environments. To attack the uncertainty in available communication resources in wireless control systems closed over WLAN, a cross-layer adaptive feedback scheduling (CLAFS) scheme is developed, which takes advantage of the co-design of control and wireless communications. By exploiting cross-layer design, CLAFS adjusts the sampling periods of control systems at the application layer based on information about deadline miss ratio and transmission rate from the physical layer. Within the framework of feedback scheduling, the control performance is maximized through controlling the deadline miss ratio. Key design parameters of the feedback scheduler are adapted to dynamic changes in the channel condition. An event-driven invocation mechanism for the feedback scheduler is also developed. Simulation results show that the proposed approach is efficient in dealing with channel capacity variations and noise interference, thus providing an enabling technology for control over WLAN.Comment: 17 pages, 12 figures; Open Access at http://www.mdpi.org/sensors/papers/s8074265.pd

Wireless sensor network system for indoor air quality supervision

U okviru diplomskog rada razvijen je sustav nadzora kvalitete zraka u zatvorenim prostorima. Sustav je razvijen koristeći koncept bežične senzorske mreže. Sustav prikuplja podatke s terena čiji su izvori senzorski čvorovi, a ponori distribuirane instance korisničke aplikacije. Senzorska mreže u konačnici prikuplja podatke o: • zadimljenosti prostorije, • količini lebdećih čestica u zraku, • grubu detekciju količine štetnog plina u prostoriji, • mjerenje temperature i • iznos relativne vlažnosti zraka. Senzorski čvorovi raspoređeni su u promatranom objektu, a prikupljeni podaci su proslijeđeni centralnom poslužitelju. Centralni poslužitelj je realiziran Internet aplikacijom. U okviru rada obrađene su osnove kakvoće zraka, zatim je opisan osnovni princip definiranja sustava (bežične senzorske mreže) s predloškom za izvedbu zadanog sustava. Obrađene su potrebne jedinice, među kojima su senzori za mjerenje potrebnih fizikalnih veličina, bežični komunikacijski moduli i mikroupravljački uređaji. Opisana je priprema okoline i konfiguracije, primjerice na usmjerniku za definiranu funkcionalnost prenošenja podataka iz senzorske mreže do korisničke aplikacije. Opisana je izrada korisničke aplikacije čime je dovršena izrada funkcionalnosti sustava. U konačnici izvedena su mjerenja prijema paketa kako bi se doznala ograničenja sustava, vezana uz domet i strategiju postavljanja komunikacijskih čvorova. U zaključku su predložena moguća unapređenja postojećeg rješenja ili mogućnosti prenamjene sustava.This thesis goes through a study and a practical development of a system of indoor air quality management. Indoor air quality management system is been developed with the wireless sensor network concept in its focus. This system is capable of collecting data from a distributed network of sensor nodes. Visualization of data is made by a service of user applications which are distributed to network clients. Sensor network collects data about: • amount of smoke in an object, • amount of particle matter in the air of an object, • approximation on the amount of harmful gas or gases in the object, • current temperature, • and amount of relative humidity. Sensor nodes are deployed to a selected complex, collected data is been forwarded to a central server. Server is implemented as a web application. Thesis elaborates the basic principle of defining the system (of wireless sensor networks) with its model for the performance measurement. Study on all necessary components is been presented, including sensors, wireless modules and microcontrollers. Basic settings and preparation of the environment is been defined, e.g. for the functionality of relaying data from sensor network to the user application. Afterwards, one can find notations on a development of the user application which completes the functionality of the proposed system. Finally, measurement are been presented on the packet reception rate, which can indicate on the limitations of the system doe to the propagation of packets in indoor environment. Measurement can be used as a indication for strategies on setting up network configuration and node distribution. In the conclusion there are proposed improvements for the selected solution or possibilities of functionality conversion