Youngjin Choi

The disturbance observer (DOB) has been widely utilized for high-precision and high-speed motion control applications. In this note, we suggest the robustness measure of the DOB as a criterion to design the robust DOB systems. Also, we suggest its design guidelines especially for second-order systems. Experimental results for an optical disk drive system show the validity of design guidelines.

This paper proposes the walking pattern generation method, the kinematic resolution method of center of mass (CoM) Jacobian with embedded motions, and the design method of posture/walking controller for humanoid robots. First, the walking pattern is generated using the simplified model for bipedal robot. Second, the kinematic resolution of CoM Jacobian with embedded motions makes a humanoid robot balanced automatically during movement of all other limbs. Actually, it offers an ability of whole b

We present a novel normalized least mean square (NLMS) algorithm with robust regularization. The proposed algorithm dynamically updates the regularization parameter that is fixed in the conventional <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$epsilon $</tex> -NLMS algorithms. By exploiting the gradient descent direction we derive a computationally efficient and robust update scheme for the regularization parameter. Through experiments we demons

This paper proposes the indirect zero momentum position (ZMP) controller for biped robot systems and proves its disturbance input-to-state stability (ISS). The ZMP control has been used as a standard method for stable walking control of biped robot systems. Since the ZMP information consists of position and acceleration of the center of gravity (COG) for a biped robot system, the ZMP can be indirectly controlled by the motion of COG. In this paper, the reference COG planner is developed by solvi

Abstract The purpose of this laboratory study was to investigate the effectiveness of vermiculite extract solutions (VES) as a coagulant and of vermiculite as an adsorbent for removal of color from dye wastewater. In coagulation experiments, it was found that VES could be applied to the treatment of dye wastewater with its contents of various cations (e.g. Mg, Fe, Al, Ca, Si etc.) useful for coagulation. Coagulation with VES produced less sludge at a lower coagulant dosage in comparison with to

Co‐firing and shrinkage matching of low‐ and middle‐ permittivity dielectric compositions for the application to a low‐temperature co‐fired ceramics system was investigated. Several glass compositions were initially examined for the low‐temperature firing of middle‐ K ( K ∼20) dielectrics, and their compositions were further modified for shrinkage matching between low‐ K ( K ∼6) and middle‐ K layers. By controlling the processing parameters such as the solid loading ratio and stacking sequence,

This paper suggests an inverse optimal PID control design method to track trajectories in Lagrangian systems. The inverse optimal PID controller exists if and only if the Lagrangian system is extended disturbance input-to-state stable. First, we find the Lyapunov function and the control law that satisfy the extended disturbance input-to-state stability by using the characteristics of the Lagrangian system. The control law has a MID control form and satisfies the Hamilton-Jacobi-Isaacs equation.

The investigation has been carried out by treating 1 m3/day of livestock wastewater for 9 months. The biological process is composed of two reactors connected in series. Each reactor has been designed to stimulate the growth of Bacillus sp., spore-forming aerobic or facultatively anaerobic bacteria. As a consequence, the population of Bacillus sp. is aptly increased via the cycle of sporulation, germination and proliferation. With a predominant growth of Bacillus sp., the microbial activity has

In order for robots to be operated in a variety of environmental conditions, a smooth motion trajectory to goal point is needed in accordance with actuators specifications of the robot. In this paper, a conventional cubic polynomial method for symmetric curve (S-curve) trajectory planning is extended to the smooth (infinitely differentiable and continuous) symmetric and asymmetric curve (AS-curve) trajectory planning derived from a smooth jerk function. In other words, the proposed methods are a

Suboptimal /spl Hscr//sub /spl infin// controller is said to internally stabilize the closed loop transfer matrix. However, the stability of the controller is not assured in the conventional /spl Hscr//sub /spl infin// control theory. An unstable controller can damage the whole system when the sensor fails or actuator saturates. This paper presents a stable n-dimensional /spl Hscr//sub /spl infin// controller and its parameterization for the LTI system based on the sufficient condition for the e