• 제어로봇시스템학회논문지
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• 제20권5호
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• pp.584-591
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• 2014

This paper presents a novel aided navigation method for AUV (Autonomous Underwater Vehicles). The navigation system for AUV includes several sensors such as IMU (Inertial Measurement Unit), DVL (Doppler Velocity Log) and depth sensor. In general, the $13^{th}$ order INS error model, which includes depth error, velocity error, attitude error, and the accelerometer and gyroscope biases as state variables is used with measurements from DVL and depth sensors. However, the model may degrade the estimation performance of the heading state. Therefore, the $11^{th}$ INS error model is proposed. Its validity is verified by using a degree of observability and analyzing steady state error. The performance of the proposed model is shown by the computer simulation. The results show that the performance of the reduced $11^{th}$ order error model is better than that of the conventional $13^{th}$ order error model.

• 제어로봇시스템학회논문지
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• 제7권10호
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• pp.843-848
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• 2001

Most of gimballed inertial navigation systems(GNIS) are calibrated periodically to maintain their inherent accuracy. The existing calibration techniques using the conventional schuler test with the least square method and the multiposition test take a long time and have some problems in procedures. To solve this problem, calibration method using a linear Kalman filter is proposed by us. In this paper, the calibration method by the change of Schuler period is studied in order to improve the calibration performance of the gimballed INS. First of all, it is shown that the observability of Kalman filter is also enhanced the Schuler period is decreased. Simulation results show that the calibration performance using the present scheme is improved according to the decrease of the Schuler period and the calibration time is shortened extremely, too. And our proposed technique shows desirable estimation performance for the g-sensitive errors of inertial sensors in particular.

• ETRI Journal
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• 제39권4호
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• pp.605-613
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• 2017

Simulated fault injection (SFI) is widely used to assess the effectiveness of fault tolerance mechanisms in safety-critical embedded systems (SCESs) because of its advantages such as controllability and observability. However, the long test time of SFI due to the large number of test cases and the complex simulation models of modern SCESs has been identified as a limiting factor. We present a method that can accelerate an SFI tool using a checkpoint forwarding (CF) technique. To evaluate the performance of CF-based SFI (CF-SFI), we have developed a CF mechanism using Verilog fault-injection tools and two systems under test (SUT): a single-core-based co-simulation model and a triple modular redundant co-simulation model. Both systems use the Verilog simulation model of the OpenRISC 1200 processor and can execute the embedded benchmarks from MiBench. We investigate the effectiveness of the CF mechanism and evaluate the two SUTs by measuring the test time as well as the failure rates. Compared to the SFI with no CF mechanism, the proposed CF-SFI approach reduces the test time of the two SUTs by 29%-45%.

• Journal of Mechanical Science and Technology
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• 제16권12호
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• pp.1583-1593
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• 2002

This paper discusses the model validation and vibration suppression of an AMB flexible rotor via additional LQG controller. The main difficulty in the vibration suppression of the flexible rotor using AMB is to realize a controller that can minimize resonance without injuring the stabilized rigid modes. In order to solve this problem, simple scheme for system modeling and controller design are developed. Firstly, the AMB flexible rotor is stabilized with a PID controller, which leads to a new stable rotor-bearing system. Then, authors propose the model validation procedure using measured open-loop frequency responses to obtain an accurate model of the AMB flexible rotor system. After that, LQG controller with modal weighting is designed to suppress resonances of the stable rotor-bearing system. Due to the poor controllability and observability of flexible modes compared to rigid ones, balancing of two Gramians is prerequisite for the fair LQG controller design. Simulation with step disturbance and experimental results of unbalance response up to 10,000 rpm verified the effectiveness of the proposed scheme.

• 대한기계학회논문집B
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• 제41권3호
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• pp.199-204
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• 2017

열전소자를 이용하여 고온의 표면을 능동적으로 냉각하여 적외선 방사량을 줄이는 기술을 소개한다. 공력가열이나 자체 발열 등에 의한 고온 표면 환경을 구현하였고, 여기에 열전소자를 설치하여 냉각하였을 때의 표면 온도와 적외선 방사량을 상용 수치해석 소프트웨어를 사용하여 계산하였다. 이를 통해 특정 환경에서 열전냉각소자를 이용하여 고온 표면에 있어 외부 환경과 비교했을 때의 적외선 방사량 대비를 이론적으로 완전히 제거할 수 있음을 확인하였다.

• 제어로봇시스템학회논문지
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• 제8권7호
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• pp.547-555
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• 2002

This paper proposes a stabilizing controller for the multirate sampled-data systems, which have a periodic output measurement scheme, in case of the open-loop unstable plant. A sufficient condition for maintaining observability in the multirate sampled-data systems is derived and a design strategy for filtered disturbance rejection is proposed. We also propose a design method for the plant output estimator. It is shown that the proposed pre-stabilizing controllers can stabilize the plant through the simulations. The proposed controller has IMC structure, and can be decomposed into the pre-stabilizing controller, the plant output estimator, the filtered disturbance estimator and the inverse of the fast pre-stabilized plant model. We assume that the plant is open-loop unstable and the disturbance consists of a sum of finite number of sinusoids with different frequencies. Some examples are presented for illustrations.

• Smart Structures and Systems
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• 제10권4_5호
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• pp.353-373
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• 2012

The instrumented Canton Tower is a 610 m high-rise structure, which has been considered as a benchmark problem for structural health monitoring (SHM) research. In this paper, an improved automatic modal identification method is presented based on a natural excitation technique in conjunction with the eigensystem realization algorithm (NExT/ERA). In the proposed modal identification method, damping ratio, consistent mode indicator from observability matrices (CMI_O) and modal amplitude coherence (MAC) are used as criteria to distinguish the physically true modes from spurious modes. Enhanced frequency domain decomposition (EFDD), the data-driven stochastic subspace identification method (SSI-DATA) and the proposed method are respectively applied to extract the modal parameters of the Canton Tower under different environmental conditions. Results of modal parameter identification based on output-only measurements are presented and discussed. User-selected parameters used in those methods are suggested and discussed. Furthermore, the effect of environmental conditions on the dynamic characteristics of Canton tower is investigated.

• 한국항공우주학회지
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• 제45권8호
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• pp.671-677
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• 2017

본 논문은 관성항법시스템(Inertial Navigation System)과 비전 센서(Vision Sensor)를 활용한 통합 항법시스템의 성능 향상을 위한 INS/멀티비전 통합항법 시스템을 제시하였다. 기존의 단일 센서나 스테레오 비전(Stereo vision)을 활용한 경우 측정되는 랜드마크의 수가 적을 경우 필터가 발산하는 문제가 발생할 수 있다. 이러한 문제를 해결하기 위해 본 논문에서는 3개의 비전 센서를 동체를 기준으로 $0^{\circ}$, $120^{\circ}$, $-120^{\circ}$으로 설치하여 단일 센서로 사용되는 경우보다 성능이 향상됨을 수치 시뮬레이션을 통하여 검증하였다.

• 한국정보과학회논문지:시스템및이론
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• 제30권2호
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• pp.99-107
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• 2003

본 논문에서는 RTL 회로에 대한 테스트 용이도 분석방식과 테스트 용이화 설계 방식을 제안한다. RTL 회로에 대하여 제어도와 관측도를 분석하고 테스트 용이도를 높이기 위하여 테스트용 멀티플렉서의 삽입 위치를 결정한다. 그리고 삽입해야 할 테스트용 멀티플렉서의 우선순위를 결정하여 우선순위가 높은 몇 개의 테스트용 멀티플렉서만을 삽입한다. 제안하는 테스트 용이화 설계 방식은 우선순위가 높은 멀티플렉서만을 삽입함으로써 면적 오버헤드를 최소할 수 있다. 실험을 통해 주사 방식을 적용했을 때보다 적은 면적 증가율을 보이며, 높은 고장 검출율과 테스트 패턴의 효율을 얻을 수 있다. 그리고 주사 방식에 비해 테스트 패턴을 삽입하는데 필요한 시간이 적음을 확인하였다.

• ETRI Journal
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• 제34권1호
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• pp.44-54
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• 2012

Because of the intrinsic lack of internal-system observability and controllability in highly integrated multicore processors, very restricted access is allowed for the debugging of erroneous chip behavior. Therefore, the building of an efficient debug function is an important consideration in the design of multicore processors. In this paper, we propose a flexible on-chip debug architecture that embeds a special logic supporting the debug functionality in the multicore processor. It is designed to support run-stop-type debug functions that can halt and control the execution of the multicore processor at breakpoint events and inspect the possible causes of any errors. The debug architecture consists of the following three functional components: the core debug support block, the multicore debug support block, and the debug interface and control block. By embedding this debug infrastructure, the embedded processor cores within the multicore processor can be debugged simultaneously as well as independently. The debug control is performed by employing a JTAG-based scanning operation. We apply this on-chip debug architecture to build a debugger for a prototype multicore processor and demonstrate the validity and scalability of our approach.