Study on Implementation of Constant Current Control...

Jo Sep 6, 2024

Ozone has strong oxidation ability and very strong reactivity with organic and inorganic substances. It also leaves no secondary contaminants, which makes it applicable in a variety of ways in many fields including chemical industry, medicine, light industry, agriculture, water treatment, etc.

With the expansion of application of ozone generators over a long period since its appearance, the power supply of ozone generation has been made in various types and many achievements have been made in the research for power quality improvement.

Nowadays, an ozone generator based on dielectric barrier discharge (DBD) is popular and the high-voltage and high-frequency inverter power supply is essential in power mode.

Hwang Kum Song, a researcher at the Nano Physics Engineering Institute, has proposed a method for a feedback control of the discharge current in a DBD type high-frequency and high-voltage power supply to keep the discharge intensity of the ozone generator constant and to improve the power efficiency.

He mapped the discharge current model of the DBD inverter source, which is subject to strong nonlinearity and model uncertainty, to a dynamic linearization (DL) model to design a model-free adaptive control (MFAC) algorithm, and conducted a simulation on Matlab Simulink. He designed an MFA controller with the control object equivalent to the simplest dynamic linear model.

The strong nonlinearity and model uncertainty inherent in the control objective reduce the control effectiveness of conventional control approaches (PID control or fuzzy-PID control) and complicates the application of intelligent control approaches.

However, MFAC method, which requires no model of a plant and only controls the input and output data of the system, is more effective in constant-current control of the DBD ozone generator. MFA controller based on compact form dynamic linearization is convenient for implementation because of its simple structure and low computational cost. In addition, optimizing the parameters of the model-free adaptive controller can achieve more flexible adaptation of the controller, eliminate most of the overshoot and improve the response speed.

The simulation results showed the improved effectiveness of the model-free adaptive controller compared to the PID controller or the fuzzy-PID controller.

Kyongdang of Koguryo

Jo Sep 5, 2024

Kyongdang was a civilian education establishment of the Koguryo age.

Koguryo people, regardless of their high or low social standings, liked learning, so they built a large house called kyongdang for educating young people including children.

The education at kyongdang was aimed at cultivating patriotism and talent, and courage and strength.

Those who attended kyongdang learnt to read and acquired knowledge of history and other fields day and night.

In addition, they built up their physical strength, training in several military arts like archery, horse riding, swordsmanship, etc.

It has been said that many kyongdang graduates with literary and military accomplishments played a big part in the battles against foreign invaders.

Inverse Dynamic Analysis of 3-DOF Parallel Manipula...

Jo Sep 4, 2024

Parallel manipulators are closed-loop mechanical structures presenting very good performance in terms of accuracy, rigidity and ability to move large loads. Generally, the mechanism has two platforms: one is attached to the fixed reference frame and the other performs arbitrary motions in its workspace. Some moving legs similar to those of serial robots connect the moving platform to the fixed platform. Spherical joints, revolution joints or prismatic joints connect the elements of the robot to one another.

Recently, much effort has been devoted to the kinematic and dynamic analysis of fully parallel manipulators. The dynamic analysis was usually conducted by analytical methods of classical mechanics in which projection and resolution of equations on the reference axes are written in a considerable number of cumbersome, scalar relations and the solutions are rendered by large-scale computation together with time-consuming computer codes.

Pang Thae Jin, a researcher at the Robotics Institute, has established a new method for inverse dynamic analysis of a 3-DOF parallel manipulator with three actuators using an approach based on the principle of virtual work.

The new approach is far more efficient, and it can eliminate all forces of internal joints and directly determine the time-history evolution of torques and powers required by the three actuators.