• Advances in aircraft and spacecraft science
• /
• v.6 no.5
• /
• pp.349-369
• /
• 2019

In the design of flight control systems there are issues that deserve special consideration and attention such as external perturbations or systems failures. A Simple Adaptive Controller (SAC) that does not require a-priori knowledge of the faults is proposed in this paper with the aim of realizing a fault tolerant flight control system capable of leading the pitch motion of an aircraft. The main condition for obtaining a stable adaptive controller is the passivity of the plant; however, since real systems generally do not satisfy such requirement, a properly defined Parallel Feedforward Compensator (PFC) is used to let the augmented system meet the passivity condition. The design approach used in this paper to synthesize the PFC and to tune the invariant gains of the SAC is the Population Decline Swarm Optimization ($P_DSO$). It is a modification of the Particle Swarm Optimization (PSO) technique that takes into account a decline demographic model to speed up the optimization procedure. Tuning and flight mechanics results are presented to show both the effectiveness of the proposed $P_DSO$ and the fault tolerant capability of the proposed scheme to control the aircraft pitch motion even in presence of elevator failures.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.17 no.3
• /
• pp.266-273
• /
• 2012

In this paper, the new open fault detection and tolerant operation method for 3 phase PWM rectifier is proposed. When open fault occurred on the inverter switches of 3 Phase PWM rectifier, the DC link voltage ripple is increased because the input current of the faulty phase is distorted. In this case, the quality of electric power would decrease, and the life time of DC link capacitor is decreased. The open fault is detected by a simple MRAS(Model Reference Adaptive System) without additional hardware sensors, and the tolerant operation carried out by turning on the opposite switch of the faulty switch without any redundancy. By the proposed method, the faulty phase input current can be controlled, so that 3-phase input current is balanced relatively under the faulty condition and the voltage ripple of DC link output is reduced. The validity of the proposed technique is proved on the 6kW 3-phase PWM rectifier system by simulation and experiment.

• Journal of Institute of Control, Robotics and Systems
• /
• v.17 no.11
• /
• pp.1067-1073
• /
• 2011

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.

• Journal of Institute of Control, Robotics and Systems
• /
• v.17 no.11
• /
• pp.1154-1158
• /
• 2011

In this paper, we discuss an observer-based fault tolerant controller design for the T-S (Takagi-Sugeno) fuzzy system with exogenous disturbance. To derive robust controller design conditions, we use $H_{\infty}$ design technique. The design conditions are derived in terms of linear matrix inequalities. An illustrative example is provided to show the effectiveness of the proposed methodology.

• Journal of Institute of Control, Robotics and Systems
• /
• v.18 no.5
• /
• pp.407-412
• /
• 2012

In this paper, we discuss an observer-based fault tolerant controller design for the unmanned aerial vehicle (UAV) systems with exogenous disturbance. To derive robust controller design conditions, we use $H_{\infty}$ design technique. The design conditions are derived in terms of linear matrix inequalities. An illustrative example is provided to show the effectiveness of the proposed methodology.

• Journal of Power Electronics
• /
• v.18 no.2
• /
• pp.558-572
• /
• 2018

In addition to its modular nature, a Hybrid Modular Multilevel Converter (HMMC) assembled from half-bridge and full-bridge sub-modules, is able to block DC faults with a minimum number of switching devices, which makes it attractive for high power applications. This paper introduces a control strategy based on the Root-Least Square (RLS) algorithm to estimate the capacitor voltages instead of using direct measurements. This action eliminates the need for voltage transducers in the HMMC sub-modules and the associated communication link with the central controller. In addition to capacitor voltage balancing and suppression of circulating currents, a fault tolerant control unit (FTCU) is integrated into the proposed strategy to modify the parameters of the HMMC controller. On advantage of the proposed FTCU is that it does not need extra components. Furthermore, a fault detection unit is adapted by utilizing a hybrid estimation scheme to detect sub-module faults. The behavior of the suggested technique is assessed using PSCAD offline simulations. In addition, it is validated using a real-time digital simulator connected to a real time controller under various normal and fault conditions. The proposed strategy shows robust performance in terms of accuracy and time response since it succeeds in stabilizing the HMMC under faults.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.1
• /
• pp.59-70
• /
• 2022

In this paper, we proposed an active fault tolerant control (AFTC) method for the position control of a quadrotor with complete loss of effectiveness of one motor. We obtained the dynamics of a quadrotor using Lagrangian equation without small angle assumption. For detecting the fault on a motor, we designed a fault detection module, which consists of the fault detection and diagnosis (FDD) module and the fault detection and isolation (FDI) module. For the FDD module, we designed a nonlinear observer that observes the states of a quadrotor based on the obtained dynamics. Using the observed states of a quadrotor, we designed residual signals and set the appropriate threshold values of residual signals to detect the fault. Also, we designed an FDI module to identify the fault location using the designed additional conditions. To make a quadrotor track the desired path after detecting the fault of a motor, we designed a fault tolerant controller based on the multiple sliding surface control (MSSC) technique. Finally, through simulations, we verified the effectiveness of the proposed AFTC method for a quadrotor with complete loss of effectiveness of one motor.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.12
• /
• pp.2579-2585
• /
• 2009

It is an important problem without system breaking. Like this, to make a computer system operate normally, various commercial fault tolerant techniques are used. Almost commercial products of fault tolerant system consume much cost. This paper proposes kernel hardening technique that are reducing panic using DLM modue in Linux USB driver. I experimented the design technique in Linux O.S. By the experiment, the suggesting technique which includes USB module with DLMis working well.

• Journal of Power Electronics
• /
• v.18 no.1
• /
• pp.56-69
• /
• 2018

In this paper, an improved Space Vector Modulation (SVM) based fault tolerant operation on a nine-level Cascaded H-Bridge (CHB) inverter with an additional backup circuit is proposed. Any type of fault in a power converter may result in a power interruption and productivity loss. Three different faults on H-bridge modules in all three phases based on the SVM approach are investigated with diagrams. Any fault in an inverter phase creates an unbalanced output voltage, which can lead to instability in the system. An additional auxiliary unit is connected in series to the three phase cascaded H-bridge circuit. With the help of this and the redundant switching states in SVM, the CHB inverter produces a balanced output with low harmonic distortion. This ensures high DC bus utilization under numerous fault conditions in three phases, which improves the system reliability. Simulation results are presented on three phase nine-level inverter with the automatic fault detection algorithm in the MATLAB/SIMULINK software tool, and experimental results are presented with DSP on five-level inverter to validate the practicality of the proposed SVM fault tolerance strategy on a CHB inverter with an auxiliary circuit.

• The Journal of the Korea Contents Association
• /
• v.6 no.10
• /
• pp.126-133
• /
• 2006

Application software streaming is a virtualization technology that enables users to use applications without installation on her/his computer. With application streaming service, a client immediately starts and uses the application as if it were installed. The application can be executed while executable codes for the application may still be streamed. Since the software streaming is based on networks, its service is affected by network failures. Network failures may cause the streamed application to stop, and to make it worse, also the system may crash because executable codes for the application can't be streamed from the streaming server. Using the Pareto principle (80 vs. 20 rule), users can be served continuously with the minimum functions that are frequently used, pre-fetched and cached if we provide a more intelligent and fault-tolerant streaming technique. This paper proposes the concept and technique named Evergreen. Using the Evergreen technique, users can continue using the streamed application while a network failure occurs, although user can access only the streamed code. We also discuss the implementation of Evergreen technique in details.