60 research outputs found
An Unknown-Input-Observer Based Approach for Cyber Attack Detection in Formation Flying UAVs
No full textIn this paper we studied a possible cyber attack detection on a network of UAVs in a formation ying set up. The communication network of the UAVs in the formation makes them vulnerable to a potential attack from malicious adversaries. We will consider two types of attacks: A node attack on the UAVs and a deception attack on the communication between the UAVs. We propose Unknown Input Observer based distributed fault detection scheme to detect a cyber attack and identify the compromised UAV in the formation setup. In the first part of the paper, UAVs formation control will be presented where the UAVs cooperate among themselves for a shared task using inter vehicle communication. A consensus algorithm is used to reach a pre-spesified formation. In the second part, a node and a communication path deception cyber attacks on the UAV's network are considered with their respective models in the formation setup. For these cyber attacks detection, a bank of Unknown Input Observer (UIO) are used and presented with the sufficient conditions for existence of the proposed observer in the UAV formation setup. A residual generated using the bank of UIOs are used to detect and to identify the compromised UAV in the formation setup
Rethinking Educati. in Ethiopia. Tekeste Negash, Nordiska Afrikainstitutet, Uppsala, 1996, 118 pages .
No full textTekeste Negash, the author of The Crises ofEthiopia Education: some implications fornation building (t 990), has' recently comeout with a book, Rethinking Education inEthiopia. He analyses educational issues andpolices in Ethiopia from the historical andcontemporary perspectives in relation to thedevelopment of the country. He alsoforwards recommendations some. of whichare in fact controversial
가상 물리 시스템에 대한 강인한 네트워킹 및 가상 공격 탐지
No full text학위논문(박사) - 한국과학기술원 : 항공우주공학과, 2018.8,[vi, 93 p. :]The threats on cyber-physical system have changed much into a level of sophistication that elude the traditional security and protection methods. A paradigm shift is necessary to incorporate a proactive approach on top the reactive protection methods employed in dealing with the evolving threats. This work addresses a proactive and reactive approaches to the cyber security of a formation flying UAVs. In the proactive approach, resilient formation control of UAVs in the presence of non-cooperative (defective or malicious) UAVs are presented. The problem of network resilient consensus in the presence of misbehaving nodes based on local information is dealt with fault-tolerant consensus algorithm. In the proposed framework, a graph-theoretic property of network robustness conveying the notion of a direct information exchange between two sets of UAVs in the network is introduced to analyze the behavior and convergence of the distributed consensus algorithm. A distributed control policy is developed to maintain the network connectivity threshold to satisfy the topological requirement put forward for the resiliency of the consensus algorithm. The reactive approach deals with attack/fault detection and isolation of the compromised UAV in the network. In the multi-agent formation control, fault detection and Isolation (FDI) in control systems theory is used to detect and isolate the malicious agents using only local information. In this aspect, a bank of Unknown Input Observer (UIO) based distributed fault detection schemes, along with a rule based on residuals generated using the bank of UIOs, are proposed to detect the attacks and to identify the compromised UAV in the formation. Furthermore, an algorithm is developed to remove the faulty UAV from the network and isolate the compromised UAV once an attack is detected, while maintaining the flight formation with a missing UAV node. Various numerical examples are presented to show the applicability of both proactive and reactive approach used in deal with the cyber attack treat on a formation flying UAVs.한국과학기술원 :항공우주공학과
SVM-Based Fault Type Classification Method for Navigation of Formation Control Systems
No full textIn this paper, we propose a fault type classification algorithm for a networked multi-robot formation control. Both actuator and sensor faults of a robot are considered as node fault on the networked system. The Support Vector Machine (SVM) based classification scheme is proposed in order to classify the fault type accurately. Basically, the graph-theoretic approach is used for modeling the multi-agent communication and to generate the formation control law. A numerical simulation is presented to confirm the performance of proposed fault type classification method. © Springer International Publishing AG, part of Springer Nature 2019
Genetic Algorithm Based Linear Quadratic Regulator Design For Stabilization Of Active Magnetic Bearing System With Decoupler
No full textThe Active Magnetic Bearing system (AMB) is a mechatronic tool which is used to suspend
spinning parts of a machine so that they rotate without contact to the stationary part of the machine.
AMBs are fundamentally unstable, highly nonlinear and non-minimum phase systems. As a result,
this thesis provides research efforts focused on developing the best state-feedback control system
for the AMB System's stability. To solve the laborious manual tuning of the weighting matrices
in the design of the linear quadratic regulator the genetic algorithm (GA) is used. The system’s
mathematical model has been developed and also the properties of the uncontrolled system have
been analyzed. The model developed shows that the AMB system considered is a 2x2 MIMO
system. Therefore, the interaction of the inputs with the outputs has been analyzed using relative
gain array analysis. It is observed from the simulation results that the GA-tuned LQR has resulted
better performance compared to the manually tuned LQR considering the main control loops
(highly interacting I/O pairs). But the GA tuned LQR has successfully reduced the unwanted
undershoot resulted by the inputs in the outputs as a result of slight coupling. From this, the
proposed controller for the loosely interacting input-output pairs the GA-tuned LQR has managed
to reduce the undershoot by 66.54%. This demonstrates that the GA-tuned significantly lessened
the undesirable effect of the inputs on the output
Distributed Observes for Cyberattack Detection and Isolation in Formation-Flying Unmanned Aerial Vehicles
No full textAn improved trajectory tracking control of quadcopter using a novel Sliding Mode Control with Fuzzy PID Surface.
No full textThis paper presents Super Twisting Sliding Mode Control with a novel Fuzzy PID Surface for improved trajectory tracking of quadrotor unmanned aerial vehicles under external disturbances. First, quadrotor dynamic model with six degrees of freedom (6-DOF) is developed using Newton-Euler Method. Then, a robust Sliding Mode Control based on a new Fuzzy PID Surface is designed to be capable of automatically adjusting its gain parameters. The proposed SMC controller applies super twisting algorithm with PID surface to reduce chattering and a fuzzy logic controller to automatically adjust the gain parameters in order to enhance robustness. Furthermore, the solution to stability has been given by the Lyapunov method. The controller's performance is tested through various trajectories, parameter variations, and disturbance scenarios, comparing it with recent alternatives such as Sliding Mode Control, Fuzzy Sliding Mode Control, and Fuzzy Super Twisting Sliding Mode Control using numerical simulations. The simulation results show that the proposed controller has better tracking performance, parameter variation handling, and disturbance rejection capability compared with the aforementioned controllers. Additionally, the control efforts of the proposed method are minimal and smooth, proving it to be an economically feasible controller and operationally safe for the quadrotor
Cubature Kalman Filter Based Fault Detection and Isolation for Formation Control of Multi-UAVs
No full textIn this paper we studied a system fault detection and isolation in a networked Multi-UAVs formation flight set-up using a Cubature Kalman Filter (CKF). Both actuator and sensor faults of a UAV are considered as an agent node fault on the system of UAVs in the formation flight. The CKF based fault detection scheme developed is used in order to detect a system wide fault in the formation flight. Furthermore, the graph theoretic approach used for modeling the multi agent UAV's communication is exploited to isolate the faulty UAV (node) from the flight formation. A numerical simulation is presented to confirm the proposed fault detection and isolation (FDI) performance
Litter decomposition of six tree species on indigenous agroforestry farms in south-eastern Ethiopia in relation to litterfall carbon inputs and modelled soil respiration
No full textThe indigenous agroforestry systems practised by smallholders in south-eastern Ethiopia have high biodiversity and productivity. However, little is known about their carbon (C) inputs and outputs. We carried out a 1-year litterbag study to determine leaf litter decomposition k constants for six woody species common to these agroforestry systems. The k values were then used to calculate the decomposition C losses from measured litterfall C fluxes and the results compared to modelled soil respiration (Rs) C losses. Litterbag weight loss at the end of the year was 100% or nearly so, k values 2.582-6.108 (yr(-1)) and half-life 41-112 days. k values were significantly (p = 0.023) correlated with litter N contents, nearly so with C/N ratios (p = 0.053), but not with other nutrients (Ca, Mg and K), and negatively correlated with temperature (p = 0.080). Using species, farm elevation, temperature and litter quality as predictors, partial least squares regression explained 48% of the variation in k. Depending on species, estimated decomposition C losses from litterfall were 18 to 58% lower than annual litterfall C inputs. Using a heterotrophic respiration (Rh) to Rs ratio of 0.5, modelled Rh C losses were 89 to 238% of litterfall decomposition C losses estimated using k values. However, using an Rh/Rs ratio of 0.27, which is appropriate for tropical humid forests, Rh C losses were 11 to 138% of estimated litterfall decomposition C losses. Our decomposition and soil respiration estimates indicate that litterfall is sufficient to maintain soil organic C contents and thereby the soil fertility of these unique agroforestry systems.Peer reviewe
An Eigenstructure Assignment Embedded Unknown Input Observe Approach for Actuator Fault Detection in Quadrotor Dynamics
No full textApplication of Unmanned Areal Vehicles for both civilian and military demands improved safety conditions to avoid potential malfunction and accidents in critical mission deployment. This paper presents a method for fault detection and identification (FDI) of actuator fault of a quadrotor. A combination of an Unknown Input Observer (UIO) and Beard Basic Fault Detection Filters (BFDF) are used to generate robust and directional residual using unknown input and eignestructure assignment respectively for fault identification and isolation. The uni-directional behavior of the residual will be exploited to isolate the source of the fault by comparing with known or predefined fault directions. The actuator faults are modeled as a loss of effectiveness, Lock-In-Place, Float and Hard Over Failure. The FDI system is used to detect and isolate the actuator faults in quadrotor actuator ( motors). A numerical simulation is done to demonstrate the effectiveness of the UIO and BFDF based FDI algorithm on a model quadrotor
- …
