회전형 2단 도립진자의 구조 제안 및 swing-up 제어

주도윤,정종익,이영삼 제어로봇시스템학회 2023 제어로봇시스템학회 국내학술대회 논문집 Vol.2023 No.6

모델기반 swing-up 제어를 위한 2단 도립진자의 구조 설계 및 계수 추정에 대한 연구

주도윤,최창규,정종익,이영삼 제어·로봇·시스템학회 2022 제어·로봇·시스템학회 논문지 Vol.28 No.9

Mathematical models and parameters with high accuracy are required for the swing-up control of a double inverted pendulum. This study proposes a mechanical structure of a double inverted pendulum having excellent matching characteristics with a mathematical model. The implementation of a parameter estimation method based on nonlinear optimization, which is essential for swing-up control, is also proposed. The proposed structure of a double inverted pendulum eliminates backlash using the direct drive of a BLDC motor, minimizes the unmodeled frictional force through bearing cleaning and oiling, minimizes unnecessary load torque using the double support of a timing pulley shaft and power transmission through a coupling, and constrains the pendulum rotation to one degree-of- freedom by adopting a dual-bearing joint. In addition, both 3D printing and CNC milling are appropriately used to satisfy the requirements for each mechanical part. The swing motion of the manufactured double inverted pendulum is measured using the lab-built light-weight rapid control prototyping 02 (LW-RCP02). The proposed parameter estimation method based on nonlinear optimization is implemented to match the response trajectory of the actual double inverted pendulum with that of a Simulink model implemented as an S-function. Finally, the effectiveness of the proposed double inverted pendulum design and parameter estimation method is confirmed by showing that the mathematical model that, based on the parameters estimated using the proposed method, accurately describes the response characteristics of the double inverted pendulum. .

LW-RCP를 이용한 2단 도립진자의 천이 제어

정종익,주도윤,Yusuke Fujiyama,이영삼 제어·로봇·시스템학회 2023 제어·로봇·시스템학회 논문지 Vol.29 No.9

This study investigates the transition control problem for a double inverted pendulum system, which has one stable and three unstable equilibrium points. We propose a method for implementing transition control using a lab-built double inverted pendulum and extend swing-up control to achieve this. The proposed method uses a two-degree-of-freedom control structure that combines feedforward and feedback controls. To obtain the feedforward trajectories offline, we construct an optimal control problem with two-point boundary values that has constraints on the dynamic equations, boundary values at the equilibrium points, and input and output constraints. We use energy as the cost of the optimal control problem and employ a direct collocation method to transform the continuous-time optimal control problem with constraints into a nonlinear optimization problem. During real-time control, we use a time-varying LQ controller as a feedback controller to compensate for the uncertainty of feedforward control and accurately follow the feedforward trajectories. We implement the proposed transition control based on high-level thinking using the lab-built light-weight rapid control prototyping (LW-RCP) system to shorten the design time and provide useful information in the design and experiment processes. Finally, we perform an actual transition control experiment and validate the performance of the proposed method using the experimental results. .

LW-RCP를 이용한 실물 시스템에 대한 강화학습 기반의 제어기 개발 환경

이태건,주도윤,이영삼 제어·로봇·시스템학회 2023 제어·로봇·시스템학회 논문지 Vol.29 No.7

In recent years, reinforcement learning (RL)-based controller design methods have emerged as a powerful alternatives to traditional methods, providing a novel paradigm that overcomes limitations associated with the need for accurate model information. In this paper, we propose a development environment for RL-based controllers in real-world systems by integrating MATLAB/Simulink, Python, and the LW-RCP (Light-weight Rapid Control Prototyping) system developed by the authors’ laboratory. The proposed development environment utilizes LW-RCP’s library block in a Simulink-based RL controller model, enabling real-time experiments on real-world systems, and stores state information data in MATLAB’s workspace. Python obtains this data through the Python API after each episode and uses it to iteratively enhance the RL agent’s policy by using RL algorithms. Updated parameter values for the agent’s policy neural network are then sent back to MATLAB's workspace, enabling convenient updates to the deep neural network-based policy controller block in Simulink. This development environment greatly reduces the time and trial and error in configuring real-time system controllers by providing LW-RCP with all necessary functions. Moreover, the efficient data acquisition and integration between MATLAB and Python workspaces facilitate the learning process and reflection of results in Simulink-based controllers. We demonstrate the effectiveness and convenience of the proposed environment through its successful application to the swing-up control problem of a single inverted pendulum. .

Sim-to-Real 강화학습 기법을 활용한 Recovery 특성을 갖는 2단 도립진자 제어

이태건,주도윤,이영삼 대한전기학회 2023 전기학회논문지 Vol.72 No.12

In recent years with the rapid advancement of artificial intelligence, there has been extensive research to address control problems, which was previously unsolvable with traditional control techniques, using reinforcement learning-based controllers. This paper discusses a challenge in controlling a double inverted pendulum system. With the commonly used 2-DOF control technique, once the swing-up control is performed and a strong disturbance is applied, the system becomes uncontrollable and fails to perform another swing-up. However, the reinforcement learning-based controller proposed in this paper overcomes this limitation using the Sim-to-Real learning technique. To ensure successful application of Sim-to-Real learning, this paper proposes a design method for the real-world system that minimizes the reality gap, a chronic issue with the Sim-to-Real technique. Utilizing these techniques, we introduce a characteristic termed 'recovery property' denoting the ability to recover from strong disturbances, a feature difficult to achieve with traditional control methods. We design a controller with this characteristic and validate its successful operation in a real-world system.

3단 도립진자의 구조 제안 및 LW-RCP02를 이용한 Swing-up Control의 구현

최창규,주도윤,정종익,이영삼 제어·로봇·시스템학회 2022 제어·로봇·시스템학회 논문지 Vol.28 No.10

In this paper, we propose a new structure for a triple inverted pendulum with easy construction properties. We also implement a swing-up control for the proposed triple inverted pendulum using a lab-built rapid control prototyping environment known as light-weight rapid control prototyping 02 (LW-RCP02). The swing-up control of a triple inverted pendulum has a two-degree-of-freedom structure and requires a very accurate mathematical model. The proposed triple inverted pendulum adopts the same method that was developed for a double inverted pendulum by the authors’ laboratory to achieve excellent matching properties with the model. For free rotation of three pendulums, a hollow shaft revolute joint that can be used with a slip ring is newly proposed. Swing-up control of a triple inverted pendulum is implemented using Simulink and LW-RCP02. Moreover, a two-degree-of-freedom control structure combining feedforward and feedback is adopted for swing-up control of a triple inverted pendulum. We implement the parameter estimation method for the triple inverted pendulum and calculate the trajectory for feedforward control using estimated parameters and the direct transcription method. The uncertainty of feedforward control is compensated by adding a time-varying LQ feedback controller. As the sampling frequency of the implemented controller is 1KHz, real-time control is achievable using a standard PC. .

3 자유도 Stewart Platform과 LW-RCP를 이용한 Ball and Plate 시스템 구현에 관한 연구

후지야마 유우스게,주도윤,이영삼 대한전기학회 2023 전기학회논문지 Vol.72 No.8

A ball and plate system is widely recognized as an effective educational tool for teaching students about the principles of automatic control. This paper presents a practical implementation method of a ball and plate system specifically designed for undergraduate students studying automatic control. Our proposed implementation method incorporates a 3-degree-of-freedom (3-DOF) Stewart platform to manipulate the plate. This allows students to gain hands-on experience in studying the kinematics of a parallel robot. Additionally, it offers not only pitch and roll motion of the plate but also vertical motion, thereby extending the scope of control problems from 2-DOF to 3-DOF. To facilitate seamless integration with the educational environment, we have designed an interface board for data acquisition and motor driving. This interface board can be used in conjunction with a lab-built LW-RCP system, enabling students with limited experience in embedded systems or programming to easily design real-time controllers using the Simulink environment. The proposed implementation method is demonstrated by constructing and showing a regulation and tracking control system for the ball and plate system.

제어시스템 강좌의 온라인 수업 효율향상을 위한 교육환경 개발

이영삼(Young Sam Lee),주도윤(Doyoon Ju),최창규(Changkyu Choi) 제어로봇시스템학회 2021 제어·로봇·시스템학회 논문지 Vol.27 No.12

In recent years, lectures on control systems have focused on hands-on experience using actual control equipment than before. However, the online education triggered compulsorily by the Covid-19 pandemic poses has restricted the construction of an education environment for hands-on experience. In this study, we proposed an economical and compact experimental environment for control education that enables hands-on experience even through online education. To this end, we utilized a light weight rapid control prototyping (LW-RCP), which is a lab-built RCP environment, and the environment was constructed using 3D printing. In the proposed environment, LW-RCP enabled students to focus on the learning and application of related control concepts, without the inconvenience of manual C-coding and the possibility of debugging errors. In addition, the proposed control equipment, which was manufactured using 3D printing, is an inexpensive equipment with a sufficiently small size that can be placed on a desk. Owing to the low cost and small size of the proposed environment, each student can have his/her own experimental equipment, which will enable a hands-on experience even through online education. Online education is expected to expand more and more in the future as it exhibits various advantages and potentials from traditional face-to-face classes. The proposed educational environment is expected to play a meaningful role in satisfying the demands of hands-on experience for control-related lectures.