• 한국통신학회논문지
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• 제39C권11호
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• pp.1023-1030
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• 2014

배열 안테나를 이용한 빔 제어 알고리즘은 교란 신호의 대응을 위한 방식으로 주로 사용된다. 그러나 동일한 수신 전력 및 신호 개수라도 신호의 위치에 따라 성능이 변화한다. 본 논문에서는 신호의 위치관계가 빔 제어 알고리즘의 성능에 미치는 영향을 분석하였다. 이를 위해 원하는 신호와 간섭 신호들이 이루는 각도의 최소값을 '신호 이격도'로 정의하고, LCMV와 PM을 대상으로 하여 신호 이격도에 따른 빔 제어 알고리즘의 C/N0 성능 관계를 분석하였다. 모의실험을 위해 GPS 신호 및 교란 신호가 자유도에 비해 많이 존재하는 환경을 설정하고 수신기의 자세와 위치를 변경시켜 다양한 신호 이격도를 얻도록 하였다. 또한, 수신 전력의 손실 요인을 적용하여 JSR과 신호 이격도가 항재밍 성능에 미치는 영향을 살펴보았다. 연구를 통해 신호 이격도의 증가에 따라 빔 제어 알고리즘의 성능이 향상하는 경향성이 있으며, 신호 이격도가 신호 개수와 JSR에 비해 항재밍 성능에 더 큰 영향을 미치게 됨을 확인하였다.

• 농업과학연구
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• 제38권1호
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• pp.121-128
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• 2011

I/An electro-hydraulic transmission having advantages of convenience, safety, simple linking and high power, and an electronic control system were designed and fabricated. In this study, characteristics of the control system were investigated through outdoor tests for evaluation of installation of the system on a combine. Major findings were as followings. 1. Experiment for performance evaluation of the control system was conducted on concrete road. With steering lever in neutral position, driving HST swash plate and left/right wheel speed increased in proportion to driving lever angle. In case of steering control, steering swash plate angle changed in proportion to steering lever angle. This should cause increase in outer wheel speed, but it was observed that HST swash plate was controlled toward neutral to maintain the speed before steering. As a result, speed before steering was maintained despite the change in outer wheel speed by steering HST swash plate angle change. 2. It was observed that the HST system enabled steering with outer wheel maintained at constant speeds while inner wheel speed decreased, which was more stable than conventional mechanical links. In addition, for the selected 5 criteria, experiment showed satisfactory results and it was judged that installation on real vehicle would be feasible. 3. The control system showed response property of appropriate forward/reverse movement and lift/right steering, without causing any problems during experiment on concrete. Result of response property experiment on field operation also showed appropriate control over forward/reverse movement and left/right steering.

• 대한조선학회논문집
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• 제32권4호
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• pp.27-37
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• 1995

본 연구에서는 대양을 항행하는 선박의 자동조타 시스템의 정량적 평가, 해석을 위해서 추진 에너지 손실의 관점에서 성능평가지수를 도출하였다. 그 결과 성능평가지수는 침로편차, 타각, 회두각속도의 제곱평균치로써 구성됨을 밝혔고, 아울러 각 제곱평균치의 계수는 선박의 유체역학적 특성에 의해서 결정됨을 알 수 있었다. 또한 성능평가지수는 자동조타 시스템에 불규칙 외란이 입력으로 작용하였을 때, 주파수 응답법과 시뮬레이션 기법에 의해서 정도 높게 계산될 수 있음을 밝혔다. 대표적 해상 상태에서 광석운반선과 소형 어선에 대한 시계산 결과, 주파수 응답법은 작은 외란하에서 시스템이 선형인 경우에는 유용하지만, 비교적 큰 외란하에서 또는 시스템 내부에 비선형 요소가 있는 경우에는 시뮬레이션 기법이 보다 정확하고 유용함을 알 수 있었다.

• 한국자동차공학회논문집
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• 제5권6호
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• pp.155-166
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• 1997

In this study, a simulation tool is developed in order to investigate non steady-state cornering performance of 6WD/6WS special-purpose vehicles. 6WD vehicles are believed to have good performance on off-the-road maneuvering and to have fail-safe capabilities. But the cornering performances of 6WS vehicles are not well understood in the related literature. In this paper, 6WD/6WS vehicles are modeled as a 18 DOF system which includes non-linear vehicle dynamics, tire models, and kinematic effects. Then the vehicle model is constructed into a simulation tool using the MATLAB /SIMULINK so that input/output and vehicle parameters can be changed easily with the modulated approach. Cornering performance of the 6WS vehicle is analyzed for brake steering and pivoting, respectively. Simulation results show that cornering performance depends on the middle-wheel steering as well as front/rear wheel steering. In addition, a new 6WS control law is proposed in order to minimize the sideslip angle. Lane change simulation results demonstrate the advantage of 6WS vehicles with the proposed control law.

• 한국인터넷방송통신학회논문지
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• 제24권1호
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• pp.23-30
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• 2024

본 논문에서는 광대역 특성을 가지는 능동위상배열 안테나의 설계, 검증 및 분석에 대하여 기술하였다. 능동위상 배열 안테나를 항공기 혹은 미사일에 적용하려면 배열 안테나의 소형화 및 광각 빔조향 특성을 확보하는 것은 피할 수 없는 안테나 설계 고려 사항이 될 수 있다. 특히 전자적으로 광각 빔조향 시 능동반사계수 특성은 시스템의 생존 및 성능 측면에서 최소화되어야 하는 설계 파라미터이다. 광대역 특성 및 광각 빔조향에 적합한 복사 소자로 본 논문에서는 Step Flared Notch(SFN)를 적용한 배열 구조를 설계하고 구좌표계 θ 각도 기준 최대 40° 빔조향에 따른 능동반사계수를 최소화하였다. 복사소자의 대역폭은 Ka대역에서 능동반사 기준으로 3GHz를 확인하였다. 또한 실제 제작된 8by8 배열 안테나는 근접전계 시험을 통해 복사소자의 단일 패턴을 측정하고, 수학적으로 합성하여 탐색기 시스템에 사용하는 송/수신빔을 예측하여 성능을 분석하였다.

• 센서학회지
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• 제10권5호
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• pp.329-336
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• 2001

This paper describes the steering control and geomagnetism cancellation for an autonomous vehicle using an MR sensor. The magneto-resistive (MR) sensor obtains the vector summation of the magnetic fields from embedded magnets and the Earth. The vehicle is controlled by the magnetic fields from embedded magnets. So, geomagnetism is the disturbance in the steering control system. In this paper, we propose a new method of the sensor arrangement in order to remove the geomagnetism and vehicle body interference. The proposed method uses two MR sensors located in a level plane and the steering controller has been developed. The controller has three input variables ($dB_x$, $dB_y$, $dB_z$) using the measured magnetic field difference, and an output variable (the steering angle). A simulation program was developed to acquire the data to teach the neural network, in order to test the ability of a neural network to learn the steering control process. Also, the computer simulation of the vehicle (including vehicle dynamics and steering) was used to verify the steering performance of the vehicle controller using the neural network. From the simulation and field test, good result was obtained and we confirmed the robustness of the neural network controller in a real autonomous vehicle.

• 드라이브 ㆍ 컨트롤
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• 제14권2호
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• pp.16-22
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• 2017

This paper presents the algorithm of an adaptive model-free-control-based steering control for multi-axle all-terrain cranes for which the recursive least squares with forgetting are applied. To optimally control the actual system in the real world, the linear or nonlinear mathematical model of the system should be given for the determination of the optimal control inputs; however, it is difficult to derive the mathematical model due to the actual system's complexity and nonlinearity. To address this problem, the proposed adaptive model-free controller is used to control the steering angle of a multi-axle crane. The proposed model-free control algorithm uses only the input and output signals of the system to determine the optimal inputs. The recursive least-squares algorithm identifies first-order systems. The uncertainty between the identified system and the actual system was estimated based on the disturbance observer. The proposed control algorithm was used for the steering control of a multi-axle crane, where only the steering input and the desired yaw rate were employed, to track the reference path. The controller and performance evaluations were constructed and conducted in the Matlab/Simulink environment. The evaluation results show that the proposed adaptive model-free-control-based steering-control algorithm produces a sound path-tracking performance.

• 한국자동차공학회논문집
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• 제22권6호
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• pp.59-67
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• 2014

A numerical model and a controller of Active Front wheel Steer (AFS) system are designed in this study. The AFS model consists of four sub models, and the AFS controller uses sliding mode control and PID control methods. To test this model and controller an Integrated Dynamics Control with Steering (IDCS) system is also designed. The IDCS system integrates an AFS system and an ARS (Active Rear wheel Steering) system. The AFS controller and IDCS controller are compared under several driving and road conditions. An 8 degree of freedom vehicle model is also employed to test the controllers. The results show that the model of AFS system shows good kinematic steering assistance function. Steering ratio varies depends on vehicle velocity between 12 and 24. Kinematic stabilization function also shows good performance because yaw rate of AFS vehicle tracks the reference yaw rate. IDCS shows improved responses compared to AFS because body side slip angle is also reduced. This result also proves that AFS system shows satisfactory result when it is integrated with another chassis system. On a split-m road, two controllers forced the vehicle to proceed straight ahead.

• 대한기계학회논문집A
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• 제24권6호
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• pp.1479-1490
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• 2000

The design process of the motor driven tilt/telescopic steering column is established by axiomatic design approach in conceptual design stage. By selecting independent design variables for improvin g performance of the steering system, each detailed design can be carried out independently. In the detailed design, the safety in crash environment and vibration reduction are considered. An occupant analysis code SAFE(Safety Analysis For occupant crash Environment) is utilized to simulate the body block test. Segments, contact ellipsoids and spring-damper elements are used to model the steering column in SAFE. The model is verified by the result of the body block test. After the model is validated, the energy absorbing components are designed using an orthogonal array. Occupant analyses are performed for the cases of the orthogonal array. Final design is determined for the minimum occupant injury. For vibrational analysis, a finite element model of the steering column is defined for the modal analysis. The model is validated by the vibration experiment. Size and shape variables are selected for the optimization process. An optimization is conducted to minimize the weight subjected to various constraints.

• 한국음향학회지
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• 제23권3호
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• pp.206-213
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• 2004

본 논문에서는 수중에서 빠른 속도로 기동하는 표적 환경에 적합한 조향각 오차 보정기법을 제안한다. 기존의 협대역 조향각 오차 보정기법에서는 다수의 시간 데이터 단편을 이용한 반면, 제안한 기법은 하나의 시간 데이터 단편에서 다수의 주파수 성분들로부터 모드 공분산행렬을 구성하고, 이를 이용하여 얻어진 광대역 MVDR (Minimum Variance Distortionless Response) 빔출력을 최대화시키는 조향각 오차를 추정함으로써 짧은 관측시간 내에 정확한 표적의 방위각을 추정할 수 있다. 모의신호와 실제 해상 실험 데이터를 이용하여 제안한 기법의 성능을 기존의 기법과 비교, 분석하였다.