A cascade control system is a multi-loop control system that can be implemented effectively for a controlled object that is capable of measuring any intermediate control variable directly affecting the primary control variable. In cascade control systems, the intermediate sensor and controller are used to effectively reject the disturbances before they affect the primary control variable.

In a cascade control system, the inner loop control system is usually designed as a fast response system, and the outer loop control system is designed as a little slower system than the inner loop system.

Due to the good disturbance rejection and fast convergence performance, many studies have been conducted to design a sliding mode control (SMC) for the inner loop controller of a cascade system. With the improvement of chattering effect, SMC controllers have been used for not only the inner loop system, but also the outer loop control system.

To the best of our knowledge, no efforts have been focused on the relationship between the outer loop sliding surface and the inner loop sliding surface of cascade control systems.

Kim Sok Min, a researcher at the Faculty of Automatics, designed the inner loop sliding surface as a hierarchical sliding surface containing the outer loop sliding surface, and proposed a hierarchical sliding mode controller so as to reduce the outer loop reaching phase and improve the entire convergence. Furthermore, in order to improve the steady-state performance, he designed an adaptive PID sliding surface to improve the reaching phase using the proportional-integral-differential (PID) sliding surface.

The numerical simulations verified the excellent performance of the proposed design method.

If more information is needed, you can refer to his paper “An improved fast convergent sliding mode control design of a cascade system based on the hierarchical structure and an adaptive PID sliding surface” in “Second International Conference on Electronics, Electrical, and Control System (EECS 2025)” (EI).

You can find the details in his paper “Data-Driven Design of Fractional Order H^∞ Controller by Convex Optimization” in “International Journal of Dynamics and Control” (EI).

Flow shop scheduling with blocking time is a problem with zero buffer and it has been widely studied in recent years. In particular, minimizing makespan is the most popular objective function in blocking flow shop scheduling problems. Hence, it is urgent to develop an effective algorithm for minimizing the makespan in the blocking flow shop.

So far, many researches have been conducted on blocking flow shop scheduling for minimizing makespan, but no literature presents a mathematical model considering the machine blocking time for this problem.

Rim Kum Chol, a researcher at the Faculty of Automatics, proposed a flow shop scheduling model aimed at makespan minimization considering the machine blocking, and an improved genetic algorithm based on some genetic operations tailored to the problem.

First, he presented a mathematical model of the blocking flow shop scheduling problem by introducing the new consideration of machine blocking. Second, he proposed an improved genetic algorithm using some tailored genetic operators such as the order crossover and the fragment inversion interchange mutation.

The proposed algorithm can be applied to not only blocking flow shop scheduling problems but also other scheduling problems and even to many optimization problems with some modifications.

For more information, please refer to his paper “Improved Genetic Algorithm for Flow Shop Scheduling Problem with Machine Blocking to Minimize Makespan” in “Second International Conference on Intelligent Transportation and Smart Cities (ICITSC 2025)” (EI).