• Transactions on Control, Automation and Systems Engineering
• /
• 제4권2호
• /
• pp.169-175
• /
• 2002

A sliding mode control of spacecraft attitude tracking with actuator, especially reaction wheel, is presented. The sliding mode controller is derived based on quaternion parameterization for the kinematic equations of motion. The reaction wheel dynamic equations represented by wheel input voltage are presented. The input voltage to wheel is calculated from the sliding mode controller and reaction wheel dynamics. The global asymptotic stability is shown using a Lyapunov analysis. In addition the robustness analysis is performed for nonlinear system with parameter variations and disturbances. It is shown that the controller ensures control objectives for the spacecraft with reaction wheels.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1999년도 제14차 학술회의논문집
• /
• pp.41-44
• /
• 1999

Nonlinear sliding surface design in variable structure systems for spacecraft attitude control problems is studied. A robustness analysis is performed for regular form of system, and calculation of actuator bandwidth is presented by reviewing sliding surface dynamics. To achieve non-singular attitude description and minimal parameterization, spacecraft attitude control problems are considered based on modified Rodrigues parameters(MRP). It is shown that the derived controller ensures the sliding motion in pre-determined region irrespective of unmodeled effects and disturbances.

• 제어로봇시스템학회논문지
• /
• 제12권10호
• /
• pp.1018-1021
• /
• 2006

This paper presents an LMI-based method to design sliding mode observers for a class of uncertain time-delay systems. Using LMIs we derive an existence condition of a sliding mode observer guaranteeing a stable sliding motion. And we give explicit formulas of the observer gain matrices. Finally, we give a simple LMI-based design algorithm, togeter with a numerical design example.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제53권6호
• /
• pp.408-414
• /
• 2004

In this paper, a disturbance observer based sliding mode control is proposed to attenuate disturbance responses in an active magnetic bearing system, which is subject to base motion. An algorithm which decouples disturbance observation dynamics from sliding mode dynamics is suggested. This algorithm preserves the robustness of the sliding mode control and satisfies reachability condition in the presence of external disturbance and parameter uncertainties. Along with experimental results, it is shown that the proposed control is effective in disturbance rejection without any additive disturbance measurement.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 추계학술대회논문집 I
• /
• pp.219-224
• /
• 2001

An accurate tip position control of a single-link flexible manipulator subjected to torque disturbance is achieved by utilizing so called sliding mode controller with disturbance estimation (SMCDE). After formulating the governing equation of motion in the state 1pace representation, a stable sliding surface is designed via the LQR method. The SMCDE is then synthesized by integrating equivalent sliding mode controller with the disturbance estimator which is featured by an integrated average value of the imposed disturbance over a certain sampling period. The regulating tip motion of the flexible manipulator is evaluated by employing the proposed SMCDE.

• 대한기계학회논문집A
• /
• 제33권9호
• /
• pp.982-989
• /
• 2009

Parallel Kinematic Mechanism (PKM) is a device to perform the various motion in three-dimensional space and it calls for six degree of freedom. For example, Parallel Kinematic Mechanism is applied to machine tools, medical equipments, MEMS, virtual reality devices and flight motion simulators. Recently, many companies have tried to develop new Parallel Kinematic Mechanism in order to improve the cycle time and the precisional tolerance. Parallel Kinematic Mechanism uses general universal joint and spherical joint, but such joints have accumulated tolerance problems. Therefore, it causes position control problem and dramatically life time reduction. This paper focused on the rolling element to improve sliding precision in new sliding ball joint development. Before the final design and production, it was confirmed that new sliding ball joint held a higher load and a good geometrical structure. FEM analysis showed a favorable agreement with tensile and compressive testing results by universal testing machine. In conclusions, a new sliding ball joint has been developed to solve a problem of accumulated tolerance and verified using tensile and compressive testing as well as FEM analysis.

• 대한기계학회논문집A
• /
• 제29권8호
• /
• pp.1123-1131
• /
• 2005

In this paper, a formulation for a spatial sliding joint, which a general multibody can move along a very flexible cable, is derived using absolute nodal coordinates and non-generalized coordinate. The large deformable motion of a spatial cable is presented using absolute nodal coordinate formulation, which is based on the finite element procedures and the general continuum mechanics theory to represent the elastic forces. And the non-generalized coordinate, which is neither related to the inertia forces nor external forces, is used to describe an arbitrary position along the centerline of a very flexible cable. In the constraint equation for the sliding joint, since three constraint equations are imposed and one non-generalized coordinate is introduced, one constraint equation is systematically eliminated. Therefore, there are two independent Lagrange multipliers in the final system equations of motion associated with the sliding joint. The development of this sliding joint is important to analyze many mechanical systems such as pulley systems and pantograph/catenary systems for high speed-trains.

• 한국항해항만학회지
• /
• 제35권7호
• /
• pp.575-580
• /
• 2011

It is important to understand the trajectory of structure in launching process because of the short time of launching process may result in unexpected accidents or damage to structures. The high risk of structural failure is not avoidable without the fully comprehension of changing forces in launching procedure. The commercial software can evaluate the motion of launching event in calm water condition but there is the limitation of research application because of the programmed commercial software. The launching process of the spar hull is suggested with stage concept that is divided into 10 stages in time domain. A force equilibrium diagram is derived for each stage where the changes of force vector and motion characteristics take place. In particular, the effects of changes in buoyancy and drag force due to the progressive submergence of the spar hull are taken into account by means of a touch length concept. The results contained in this paper provide the valuable information of the trajectory motion evaluation with suggested methods in spar launching process with sliding barge. Furthermore, the presented stage concept and touch length concept will provide basic knowledge for understanding launching process and help to develop further research area for launching analysis.

• 정보처리학회논문지B
• /
• 제12B권2호
• /
• pp.157-166
• /
• 2005

3차원 가상현실 내에서 캐릭터 움직임 동작의 기술은 기존 방식인 키프레임 기법에 의존하던 것이 점차 동작 제어 기법을 활용하고, 보다 사실적이고 자연스러운 움직임을 생성해 내고자 하는 방향으로 발전해 가고 있다. 그러나 이러한 동작 제어 기법을 통해 가상현실의 지형 성질에 따라 적응적인 캐릭터의 동작을 표현하는데 한계가 있다. 즉, 대부분의 가상환경에서 캐릭터의 걷는 움직임은 일정하고 단조로운 동작만을 반복하여 표현하고 있어 관찰자로 하여금 지루함을 느끼게 하고, 지형의 조건이나 형태에 맞지않게 캐릭터의 발끝이 지면에 스며들거나 떠있는 등의 부자연스러운 동작으로 인해 사실감을 저하시킨다. 본 논문에서는 적은 매개변수들과 역운동학 방법을 적용하여 기본 걷기 동작을 표현하고, 지면의 성질을 마찰계수로 대표시켜 지면에 적응적인 걷기 동작의 생성 방법을 제안한다. 제안된 방법에서는 구심력과 마찰계수를 결합한 후, 이를 근거로하여 한 주기 동안의 걷는 동작을 분석하고 이를 기반으로 동작에 필요한 매개변수를 조정하여 지질에 따른 적응적인 캐릭터의 걷기 동작을 생성한다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 춘계학술대회논문집
• /
• pp.842-847
• /
• 2002

One of the challenging problems with bicycle simulators is to deal with the inherent unstable bicycle dynamics that is coupled with rider's motion. For the bicycle dynamics calculation and the real time simulation, it is necessary to identify the control inputs from the rider as well as the virtual environments. The six control forces of the Stewart platform-based motion system are used for estimation of the rider's action force, which is one of the important control inputs, but of which the direct measurement is impractical. For the effective estimation of the rider's action force, the dynamics model of the motion system is derived incorporated with both analytical and experimental methods and the sliding mode controller with perturbation estimation is developed.