Kyung-Tae Hong

Input shaping and VSC of container cranes

A dual-stage control strategy for container cranes is investigated. The first stage control is a modified input shaping control to reduce residual vibrations at the target position and to limit the sway angle of the payload during the traveling. The second stage control is a nonlinear control for the quick suppression of the residual sway while lowering the container at the target trolley position. The secondary control combines the partial feedback linearization to account for the unknown nonlinearities as much as possible and the variable structure control to account for the unmodeled dynamics and disturbances. Computer simulation results are provided.

Kinematic optimal design of a new parallel-type rolling mill : paramill

In this paper, a kinematic optimal design of a new parallel-type rolling mill based upon two Stewart platform manipulators is investigated. To provide the end-effector (work roll) with sufficient d.o.f. and to achieve the structural stability of each stand, a parallel manipulator with six legs is considered. The objective of this new parallel-type rolling mill is to pursue an integrated control of the strip thickness, strip shape, pair-crossing angle, uniform wear of the rolls and strip tension. By splitting the weighted Jacobian matrices into two parts, the linear velocity, angular velocity, force and moment transmissibilities are analyzed. A manipulability measure, as the ratio of the manipulability ellipsoid volume and the condition number of a split Jacobian matrix, is defined. The two kinematic parameters, the radius of the base and the angle between two neighboring joints, are optimally designed by maximizing the global force manipulability measure defined in the entire workspace. The maximum exerting force needed in hydraulic actuators is also calculated using the kinematic structure determined and the Plücker coordinates introduced. Simulation results are provided.

RIDE COMFORT VALUES OF FOUR KOREAN CARS IN HIGHWAYS

Vibrations on the floor in a car are transmitted to the foot, hip, and back from the seat. Human body recognizes these vibrations, but the sensitivity for each vibration is different. To evaluate these vibrations, RMS(root mean square) of accelerations, VDV(vibration does value), percent vibration, and SEAT (Seat Effective Amplitude Transmissibility) value are commonly used. For the SEAT value calculation, the PSD (Power Spectral Density) of the accelerations at the seat and the PSD of the floor are used with the frequency weighting function. If the SEAT value is less than 1, the vibration level on the seat is less than the floor, which means seat is effective to reduce the vibration. In this paper, four types of cars, i.e., a small size car of 1300cc gasoline engine, a mid-size car of 1800 gasoline engine, a full-size luxurious car of 3600cc gasoline engine, and a SUV (sport utility vehicle) of 2900 diesel engine are used and compared ride comforts using SEAT values. Experiments were carried on a highway near the suburb of Busan metro-politan city in South Korea. To compare ride comforts, the SEAT values in dynamic state are compared. Several air cells are installed in the seat cushion to improve seat comfort and to adjust seat properties by changing the air pressure. From the real car experiments, optimum air cell pressure depending on the vehicle speeds and road conditions are recommended.Copyright

Modified Smith Predictor Design for a Reclaimer

Abstract In this paper, a modified Smith predictor in the presence of input and output disturbances as well as modeling uncertainty is investigated. The modified Smith predictor includes the feedforward Smith predictor and the compensator that approximates the inverse of time-delay. Assuming a multiplicative uncertainty, a robust stability criterion and a compensator design criterion are derived. The modified Smith predictor is applied to a reclaimer, which is used in the raw yard of a steel plant and has a large output time-delay. The system identification method is used to find out a nominal model. The uncertainty bound is quantified in the frequency domain through an uncertainty quantification method. Simulation results are provided.

Self-Tuning Gain-Scheduled Skyhook Control for Semi-Active Suspension Systems: Implementation and Experiment

In this paper, a self-tuning gain-scheduled skyhook control for semi-active suspension systems is investigated. The dynamic characteristics of a continuously variable damper including electro-hydraulic pressure control valves is analyzed. A 2-d.o.f. time-varying quarter-car model that permits variations in sprung mass and suspension spring coefficient is considered. The self-tuning skyhook control algorithm proposed in this paper requires only the measurement of body acceleration. The absolute velocity of the sprung mass and the relative velocity of the suspension deflection are estimated by using integral filters. The skyhook gains are gain-scheduled in such a way that the body acceleration and the dynamic tire force are optimized. An ECU prototype is discussed. Experimental results using a 1/4-ear simulator are discussed. Also, a suspension ECU prototype targeting real implementation is provided.

Exponential Stabilization of an Axially Moving Tensioned Strip by Passive Damping and Boundary Control

Abstract In this paper, an active vibration control of a translating tensioned steel strip in the zinc galvanizing line is investigated. The dynamics of the moving strip is modeled as an Euler-Bernoulli beam with nonlinear tension. The control objective is to suppress the transverse vibrations of the strip via boundary control. A right boundary control law based upon the Lyapunov’s second method is derived. It is revealed that a time-varying boundary force and a suitable passive damping at the right boundary can successfully suppress the transverse vibrations. The exponential stability of the closed loop system is proved. The effectiveness of the control laws proposed is demonstrated via simulations.

Engine-Transmission Control for Smooth Shifting Using a Robust Adaptive Scheme with Intelligent Supervisor

Abstract In this paper, a robust adaptive control scheme with an intelligent supervisor for vehicle powertrain systems is investigated. The control objectives are to provide smooth shift transients for passenger comfort and to improve components durability. The reaction carrier speed and the turbine speed during the inertia phase are controlled to track their desired speeds. The boundedness of all signals in the closed loop system and the convergence of the reaction carrier speed error near to zero are guaranteed by applying the Lyapunov stability analysis. The adaptive compensation controller with an intelligent supervisor is implemented to keep the turbine speed error near to zero and the deviation of the shift duration within an allowable range. The proposed control algorithm is implemented and evaluated on an experimental test setup.