In recent years, more and more industrial robots have been applied to modern manufacturing systems. They need to be fast, smooth and precise to ensure high productivity and quality in many fields. Therefore, they should be designed to move smoothly with high speed and precision under kinematical and geometrical constraints. In particular, smoothness in motion is essentially required in the delicate industrial setting such as spot-welding or precise assembly, and what is important is that the planned trajectories should be continuous within the capability of actuators.

Han Chol Jun, a researcher at the Institute of Robotics, has proposed a method of planning the expanded S-curve trajectory of robotic manipulators to minimize execution time as well as to achieve smoother trajectory generation in the deceleration stage for point-to-point motions.

The simulation results of 3 DOF and 6 DOF robotic manipulators show that the proposed approach effectively reduces the jerk and snap (the derivative of jerk) in the deceleration stage while decreasing the total execution time. Also, the analysis of a single DOF mass-spring-damper system indicates that the residual vibration could be reduced to 10% more than the benchmark techniques.

For more information, please refer to his paper “An asymmetric S-curve trajectory planning based on an improved jerk profile” in “Robotica” (SCI).

An electrostatic precipitator is essential for thermal power plants, cement plants, chemical plants and mines. Its function is to clean the particulate dust contained in the smoke and gas that are discharged from the processes, thus improving the environmental pollution caused by them and improving the quality of air.

A high-voltage rectifier transformer, one of the most important parts of electrostatic precipitation equipment, is a kind of special transformer. The high-voltage rectifier transformer for electrostatic precipitation is a transformer operated under constantly varying load conditions, i.e., no-load, rated, and short-circuit conditions, and properly setting and accurately calculating the short-circuit voltage in its design is important to ensure efficient manufacturing cost and safe operation.

Yu Kwang Chol, a section head at the Faculty of Electrical Engineering, analyzed and compared the calculation methods of leakage reactance traditionally used in transformer design, and proposed an approach to calculate the leakage reactance more accurately using ANSYS Maxwell for two-winding transformers with different winding heights and a large number of windings.

He verified the accuracy of the proposed method by comparing it with conventional leakage reactance calculation methods and analyzing the error of the experimental results.

The result of the analysis shows that the ANSYS Maxwell program is a more precise and easy tool for calculating the leakage inductance and short-circuit voltage of transformers.

You can find the details in his paper “Research on the Method of Calculating Short-circuit Voltage for High-voltage Rectifier Transformer for Electrostatic Precipitation by Using the ANSYS Maxwell” in “Journal of Electrical Power & Energy Systems” (EI).

Industrially, direct reduction of iron oxides is a strong endothermic reaction, so only the temperatures above 1 000 to 1 100℃ enable reduction reactions to proceed at a rapid rate.

However, it is thermodynamically impossible to industrially enforce the reduction process by solid carbon since the temperature does not rise to 1 100℃ in the sponge iron manufacturing process and to more than 1 350℃ in the case of granulated iron. In other words, if the feed is not mixed evenly, CO gas will not participate in the reduction reaction but will be gone. In addition, the CO₂ produced by indirect reduction is not modified to CO, so the carbon required by the sponge iron manufacturing process is two to three times more than the theoretical amount.

Therefore, making coal composite iron ore with fine iron concentrate and coal powder to produce reduced iron can further improve the reduction reaction characteristics of iron oxide and reduce coal consumption.

Ro Myong Su, a researcher at the Faculty of Metallic Engineering, has investigated the characteristics of direct reduction reactions by solid carbon and decided the optimum reduction conditions of the coal composite iron ore—the main materials in a new smelting reduction iron-making furnace.

Firstly, he conducted a softening test to choose the optimum agglomerant. Secondly, he investigated the effect of factors on the reduction characteristics of coal composite iron ore by the mass flop-out method, and decided the optimum reduction conditions.

The results show that the optimum reduction conditions for more than 80% of the reduction ratio in the case of direct reduction of coal composite iron ore by solid carbon are as follows: temperature 1 250℃, carbon-containing ratio 1 and its size 30mm.