Donggil Kim

Fault-tolerant control strategy based on control allocation using smart actuators

This paper presents a networked fault-tolerant control strategy based on control allocation which is applied to a modern aircraft. The proposed method utilizes the benefits of networked control system architecture in which smart sensors/actuators are interconnected through a bi-directional digital communication network. A smart actuator, the paper focuses on, is capable of providing the supervisor level with various information on the device itself. This information on the device condition is then used to tolerate faulty actuators by re-allocating redundant actuators. Simulation results with an aircraft show that the proposed method can achieve a fast and effective compensation in the presence of actuator faults.

A Flight Control Strategy Using Robust Dynamic Inversion based on Sliding Mode Control

Dynamic inversion (DI) is a control synthesis technique that steers the system states to track the desired trajectory by cancelling the original dynamics. However, it is impossible to achieve perfect cancellation of the original dynamics in real applications, robustness problem must be considered in designing DI controller. In this paper, robust dynamic inversion (RDI) control strategy based on sliding mode control (SMC) is proposed. Different from the previous works of achieving robustness in DI controller, the proposed RDI controller is designed inherently robust. Moreover, robust observer strategy based on the RDI controller is also proposed in this paper. Numerical simulations with application to the AV-8A Harrier aircraft demonstrate the effectiveness of the proposed method.

Fault-Tolerant Networked Control Systems Using Control Allocation for Failures in Multiple Control Surfaces

In this paper, the methodology of a CA (Control Allocation) based FTNCS (Fault-Tolerant Networked Control System) is proposed. Control allocation is a control surface management technique by redistributing the redundant control surfaces in overactuated systems. In modern high performance aircrafts, they adopt many redundant control surfaces to provide high performance and to satisfy various tactical requirements. Moreover, redundant control surfaces provide an opportunity to compensate performance degradation due to failures in more than one actuator by re-allocating redundant control surfaces. Simulation results with an F-18 HARV demonstrate that the proposed CA based FTNCS can achieve a fast and accurate tracking performance even in the presence of actuator faults.

Smart Actuator-Based Fault-Tolerant Control for Networked Safety-Critical Embedded Systems

In this paper, a fault-tolerant control method is presented with an application to steer-by-wire (SBW) system. SBW is a network-based vehicle steering system in which the mechanical linkage and hydraulics are replaced by electrical motors and fieldbus networks. Since failure of a steering system may result in a catastrophic accident, SBW can be considered as a safety-critical embedded system for which very high level of dependability must be satisfied. This paper proposes an effective control strategy to tolerate faulty actuators. The proposed method has a simple structure to be implemented on low cost embedded processors. The reconfiguration strategy consists of two fold: i) a smart actuator of which embedded microprocessor provides the fast and accurate diagnostic information through a time-triggered fieldbus, and ii) an IMC-PID controller which is capable of tolerating the effect of faults based on the diagnostic information being sent from the smart actuator. Simulation results with a SBW model show that the proposed method can enhance the system dependability in the presence of faults without using any redundant actuators.

Time-triggered wireless sensor network for feedback control

A communication network for use in feedback control must satisfy strict requirements on the reliable and deterministic behavior. However, wireless sensor networks such as ZigBee may introduce randomly varying delays into the system, resulting in the performance degradation or even the instability. In this paper we propose a deterministic wireless network that can be used for feedback control. The proposed approach is based on a time-triggered mechanism implemented on top of the IEEE802.15.4 standard. The effectiveness of the proposed method is demonstrated through a set of experiments on feedback control of a DC motor.

Luminescence characteristics for identifying irradiated black soybeans.

PURPOSE Considering the commercial use of food irradiation and the prevalence of international trade of irradiated food and agricultural commodities, black soybeans originating from China or Korea were irradiated at 0-5 kGy. Photostimulated luminescence (PSL) and thermoluminescence (TL) were investigated for their ability to identify characteristics that would distinguish irradiated from non-irradiated samples. MATERIALS AND METHODS Dried black soybeans [Glycine max (L.) Merr.] were irradiated using a Co-60 gamma irradiator or an electron-beam accelerator and then analysed by PSL and TL. RESULTS PSL photon counts were higher in irradiated samples than in non-irradiated ones and increased with applied doses, making it possible to distinguish irradiated from non-irradiated samples. The TL analysis revealed glow curves (TL₁) with low intensity for non-irradiated samples but a higher intensity (approximately 200°C) for irradiated samples, showing increased intensities with radiation dose. The minerals were re-irradiated at 1 kGy and the second TL glow curve (TL₂) was measured. Based on the calculated TL ratios (TL₁/TL₂) and the shape of TL₁ glow curves, the irradiated samples could be distinguished from non-irradiated ones. CONCLUSIONS PSL and TL are effective screening and reference methods for distinguishing gamma ray or electron beam irradiated black soybeans from non-irradiated black soybeans.

IEEE1588-based clock synchronization for embedded networked system with sRIO

Serial RapidIO (sRIO) has been widely used for switched interconnection of embedded systems. Clock synchronization is very essential for a networked embedded system to use multiple processors that are separated. This paper presents an IEEE1588 based clock synchronization method for an embedded system in which processors are interconnected through a sRIO network. A set of experiments with an experimental setup demonstrate that the proposed approach satisfies the synchronization precision of 20 ms without using any extra hardware for synchronization.

Fault-Tolerant Clock Synchronization for Time-Triggered Wireless Sensor Network*

Wireless sensor networks have been employed in a wide range of industry thanks to the benefits of mobility, flexibility and low cost. However, the unreliability of wireless networks is a great challenge to be used in feedback control. In order to offer reliable and deterministic wireless communications, time-triggered mechanisms are commonly used. This paper presents a fault-tolerant clock synchronization method that can be used for a time-triggered wireless network. The effectiveness of the proposed method is demonstrated through a set of experiments.

A DETERMINISTIC WIRELESS NETWORK FOR FEEDBACK CONTROL BASED ON IEEE 802.15.4

Abstract Networked feedback control systems, which have been adopted across the wide range of industries, suffer from limitations in mobility and flexibility because of the network wires. A wireless communication network, such as ZigBee based on the IEEE 802.15.4 standard, may be considered as an effective alternative to overcoming this problem. However, a communication network for use in feedback control must satisfy strict requirements on the deterministic behavior in terms of message latency and jitter. The ZigBee protocol however may introduce significant delays, which are randomly varying with time, into the system. This paper presents a deterministic wireless network that can be used for feedback control systems. The proposed approach is based on a time-triggered mechanism implemented on top of the IEEE 802.15.4 standard. The effectiveness of the proposed method is investigated using a series of experiments on the control of DC motors. Copyright

PO-203 Peroxiredoxin 5 in colon cancer promotes epithelial-mesenchymal transition

Introduction Globally, colorectal cancer (CRC) is common cause of cancer-related deaths. The high mortality rate of patients with colon cancer is due to cancer cell invasion and metastasis. Initiation of the epithelial-to-mesenchymal transition (EMT) is essential for the tumorigenesis. Peroxiredoinxs (PRX1-6) have been reported to be overexpressed in various tumour tissues, and involved to be responsible for tumour progression. However, the exact role of PRX5 in colon cancer remains to be investigated enhancing proliferation and promoting EMT properties. Material and methods In this study, we constructed stably overexpressing PRX5 and suppressed PRX5 expression in CRC cells. Results and discussions Our results revealed that PRX5 overexpression significantly enhanced CRC cell proliferation, migration, and invasion. On the other hand, PRX5 suppression markedly inhibited these EMT properties. PRX5 was also demonstrated to regulate the expression of two hallmark EMT proteins, E-cadherin and Vimentin, and the EMT-inducing transcription factors, Snail and Slug. Moreover, in the xenograft mouse model, showed that PRX5 overexpression enhances tumour growth of CRC cells. Thus, our findings first provide evidence in CRC that PRX5 promotes EMT properties by inducing the expression of EMT-inducing transcription factors. Conclusion Therefore, PRX5 can be used as a predictive biomarker and serves as a putative therapeutic target for the development of clinical treatments for human CRC.