• Journal of Mechanical Science and Technology
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• 제15권4호
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• pp.433-440
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• 2001

A new design of the sliding mode control is proposed for the uncertain linear time-varying second order system. The proposed control drives system states to the target point in the minimum time with specified ranges of parametric uncertainties and disturbances. One of the advantages of the proposed control scheme is that the control inputs do not go beyond saturation limits of the actuators. The other advantage is that the minimum arrival time and the acceleration of the second order actuators system can be estimated with given parametric bounds and can be expressed in the closed from; conversely, the designer can select actuators based on the condition of the minimum arrival time to the target point. The superior performance of the proposed control scheme to other sliding mode controllers is validated by computer simulations.

• 드라이브 ㆍ 컨트롤
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• 제13권4호
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• pp.52-58
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• 2016

The mechanical design for biped walking of a humanoid robot doing the Argentina Tango is presented in this paper. Biped walking has long been studied in the area of robotic locomotion. The aim of this paper is to implement an Argentina Tango dancer-like walking motion with a humanoid robot by using a trajectory generation scheme. To that end, this paper uses blending polynominals whose parameters are determined based on PSO (Particle Swarm Optimization) according to conditions that make the most of the Argentina Tango's characteristics. For the stability of biped walking, the ZMP (Zero Moment Point) control method is used. The feasibility of the proposed scheme is evaluated by simulating biped walking with the 3D Simscape robot model. The simulation results show the validity and effectiveness of the proposed method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.315-318
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• 1995

In this paper, an optimal trunk trajectory for stable walking of biped robots is expressed as a simple differential equation, which is then solved by numerical methods. We used ZMP (Zero Moment Point), the virtual total ground reaction point within the region of the supporting food, as the criterion of stability of biped robot walking. If the ZMP is located outside of the stable region in dynamic walking, biped robots fall down. The biped robot considered in this paper consists of two legs and a trunk. The trajectories of the two legs and the ZMP of the biped robot are determined such that they are similar ti those of a human. Based upon those trajectories, the trunk trajectory is solved by numerically integrating differential dynamic equations. Leg motions are controlled by the computed torque control method. The effectiveness of control algorithm as well as the trajectories is confirmed by computer simulations.

• 전기학회논문지
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• 제63권9호
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• pp.1273-1280
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• 2014

This paper considers a GPS anti-spoofing problem. Spoofing is an intentional interference that mislead the GNSS receiver. The spoofing attack is very significant since the target receiver is not aware of being attacked from spoofing. Accelerometers can be used to detect the spoofing signal by being compared with the acceleration obtained from GPS information using Kalman filter. In this paper we propose an N by N-point average and M-point window algorithm to detect GPS spoofing by using accelerometers and GPS outputs. The performance of the proposed algorithm is analyzed using actual vehicle trajectory and spoofing trajectory generated from INS and GPS toolbox for simulation.

• International Journal of Control, Automation, and Systems
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• 제4권1호
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• pp.42-52
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• 2006

In order to utilize hydrodynamic drag force on articulated robots moving in an underwater environment, an optimum motion planning procedure is proposed. The drag force acting on cylindrical underwater arms is modeled and a directional drag measure is defined as a quantitative measure of reaction force in a specific direction in a workspace. A repetitive trajectory planning method is formulated from the general point-to-point trajectory planning method. In order to globally optimize the parameters of repetitive trajectories under inequality constraints, a 2-level optimization scheme is proposed, which adopts the genetic algorithm (GA) as the 1st level optimization and sequential quadratic programming (SQP) as the 2nd level optimization. To verify the validity of the proposed method, optimization examples of periodic motion planning with the simple two-link planner robot are also presented in this paper.

• 한국기계기술학회지
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• 제20권6호
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• pp.912-916
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• 2018

Crawling robots are advantageous in overcoming obstacles. These robots have characteristics such as light weight and outstanding mobility. In case of large robots, they have difficulties passing narrow gaps or entering the cave. In this paper, we propose a milli-scale hexapedal robot using 4-bar linkages. Two conditions are necessary to enable efficient walking. In short, the trajectory of the foot must be elliptical, and the lowest point of the foot should be the same. These conditions are satisfied with a novel leg design. The robot has a pair of three legs and the legs are coupled to operate simultaneously. Each set of the legs are installed to robot's both sides and the legs satisfy the equal lowest foot point and elliptical trajectory. As a result, this hexapedal robot can crawl with 0.56m/s speed.

• The Korean Journal of Ecology
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• 제27권1호
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• pp.27-33
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• 2004

Cryptomeria japonica plantation was monitored every year during 15 years from 1983 to 1997 for stem diameter and volume. The reciprocal equation, 1/Y = A + B/N, was applied to the relationship between cumulative volume Y and cumulative number N from the largest tree in the stand each year. The parameters A and B, which means respectively the reciprocal of an asymptotic value of total stand stem volume and the reciprocal of the maximum stem volume, are related by a power function. The power functional relationship between A and B derived a linear relationship of B-points ( $N_{B}$, $V_{B}$; $N_{B}$ = B/A, $Y_{B}$ = 1/2A) of each Y-N curve on log-log coordinates. The gradient of B-point line was so steep that the Y-N curve moved parallel upward year by year. The time trajectory of mean stem volume (W) and density ($\rho$) provided evidence in favor of the 3/2 power law of self-thinning, because the gradient of W - $\rho$ trajectory on log-log coordinates approximated to -3/2 at the final stage of stand development. On the basis of the results of Y-N curves and W - $\rho$ trajectory, the time trajectory of maximum stem volume $W_{max obs}$ and $\rho$ was derived theoretically. The gradient of $W_{max obs}$ - $\rho$ trajectory on log-log coordinates is calculated to be -0.6105 at the final stage. The gradient of $W_{max obs}$ - $\rho$ trajectory was steeper than that of W - $\rho$ trajectory at the early stage, while the former is gentler than the latter at the later stage.stage.e.age.e.

• Journal of Astronomy and Space Sciences
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• 제22권4호
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• pp.451-462
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• 2005

향후 우리나라의 화성 탐사선 개발을 대비하여 B-평면 조준법(B-plane targeting method)을 이용한 최적 궤적 보정 기동(Optimal Trajectory Correction Maneuver, TCM)의 설계에 대한 연구를 수행하였다. 궤적 보정 기동을 설계하기 위하여 요구되는 화성 탐사 임무의 각 단계별 비행 궤적 및 궤도 정보 역시 이 연구를 통해 개발된 알고리즘을 이용하여 산출 할 수 있으며, 관련 정보는 임무 설계시 필요로 하는 최소의 섭동력들을 고려한 상황에서 산출되었다. 항행 단계에서의 탐사선은 다양한 섭동력에 의한 영향 또는 순간 기동의 오차로 기인된 비행 궤적의 오차로 인하여 목표한 위치에 도달하지 못할 수 있다. 따라서 탐사선의 적절한 비행 궤적을 유지하고 목표하고자 한 지점에 정확하게 도달시키기 위하여 도착 행성의 위치에 대하여 설정된 B-평면 좌표계를 이용하여 탐사선의 방향을 조준하여 줄 필요가 있다. NPSOL 소프트웨어를 사용하여 관련 최적해를 도출하였으며 임무동안 수행되는 기동의 총 크기를 최소화 시키도록 목적함수를 설정하였다. 수행되는 기동의 횟수는 설계자가 임의로 설정($1\~5$회)할 수 있도록 하였으며 그 시기 역시 조정 변수로 설정 할 수 있다. 마지막으로 화성 도착시 설정된 B-평면 좌표의 위치가 최종 구속조건으로 적용되어 최적화 문제를 완성하게 된다. 이 연구를 통하여 지구 출발에서부터 화성 도착, 그리고 임무 수행을 위한 포획궤도에 이르기까지 전반적인 임무 설계 및 해석이 가능하게 되었으며, 항행 단계에서 이루어지는 궤적 보정 기동의 최적 시기 및 크기 또한 분석이 가능하게 되었다. 이 연구를 통하여 개발된 알고리즘을 이용하여 향후 우리나라의 화성 탐사 임무의 설계, 분석이 가능하다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1171-1172
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• 2013

• 한국컴퓨터그래픽스학회논문지
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• 제5권2호
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• pp.33-41
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• 1999

본 논문은 동적인 균형을 위한 새로운 동작변환 기법을 제시한다. 이는 불균형한 동작을 원래의 동작 특성을 최대한 보존하면서 균형잡힌 동작으로 고쳐주는 새로운 동작 편집 기법으로서, 정적 균형만을 다루었던 기존의 연구와는 달리, 동적인 동작의 균형잡기 문제를 해결한다. 이 알고리즘은 두발 로봇의 균형제어에 널리 쓰이는 개념인 zero moment point (ZMP)의 자취를 구한 후, 이를 분석하는 방법을 통해서 실현되며 구체적으로는 다음과 같은 네단계로 이루어진다. 먼저, 동작 데이타를 스플라인커브로 피팅한다. 그 다음 이 데이타를 사용하여 ZMP 자취를 계산하여, 동작중에 불균형이 되는 부분을 찾는다. 여기서, 불균형은 ZMP 자취가 지지영역 밖으로 벗어나는 구간으로 정의된다. 다음으로 벗어난 ZMP 자취를 지지영역 안으로 투영시켜 새로운 ZMP 자취를 구한다. 마지막으로 구해진 새로운 ZMP 자취에 부합하도록 원래의 동작을 수정한다. 이 과정은 원래의 동작을 최대한 보존할 수 있도록 constrained optimization problem으로 수식화된다. 우리는 실험을 통해 이 알고리즘이 kinematic한 방법으로 편집된 동작에 역학적 사실성을 보장하는 유용한 방법임을 입증한다.