케이블 구동 유연 로봇의 위치 추적 제어를 위한 고급 제어 프레임워크의 설계, 모델링 및 개발 : DESIGN, MODELING, AND DEVELOPMENT OF ADVANCED CONTROL FRAMEWORK FOR POSITION TRACKING CONTROL OF CABLE-DRIVEN FLEXIBLE ROBOTS

다국어 초록 (Multilingual Abstract)

Modern robotics increasingly demands systems that combine precise motion control, robust stability, and adaptability to diverse operational requirements. Traditional rigid-link manipulators, with their well- established theoretical frameworks and widespread industrial deployment, have demonstrated high accuracy and reliability in performing structured tasks. However, as robotic systems evolve toward more complex functions, these conventional architectures reveal inherent limitations. Their design concentrates significant actuator mass on the joints, leading to complex joint dynamics, high inertia, and control schemes that are effective but not easily extendable to more flexible or highly coupled structures. Such constraints motivate the exploration of alternative robotic architectures that can offer new performance characteristics and open pathways to advanced control methodologies.
The cable-driven flexible robot (CDFR) represents one such architecture. Unlike conventional manipulators, the CDFR employs remotely located actuators connected to the robot body through cables. This configuration fundamentally alters the distribution of dynamics in the system. While it enables more versatile structural arrangements and introduces novel mechanical properties, it also creates significant challenges in modeling and control. The inherent compliance of the cable transmission system produces nonlinear dynamics, complex coupling effects, and high sensitivity to parameter variations. As a result, dynamic behavior is difficult to capture accurately, and traditional linear control approaches often prove insufficient. These challenges make the CDFR both an attractive research subject and a demanding testbed for advanced modeling and control strategies.
This thesis addresses these challenges with contributions that span the design, analysis, and control of CDFR. First, a complete prototype system is developed, integrating actuator placement, cable routing, and modular robot configuration. This system provides a concrete foundation for studying the dynamic properties of CDFRs and evaluating control methods in practical conditions.
Second, the kinematic formulation of the CDFR is developed. Due to the large number of degrees of freedom (DOF) and the constraints imposed by cable routing, kinematic analysis becomes computationally challenging and resource intensive. To address this difficulty, the Jacobian Pseudoinverse method is employed as an efficient approach to solve the forward and inverse kinematics of the system. This method provides a stable mapping between actuator inputs and end-effector motions, even in the presence of redundancy. To validate the accuracy and reliability of the kinematic formulation, several predefined trajectories, such as linear, circular, and triangle paths, are designed and executed. The successful reproduction of these trajectories confirms the correctness of the kinematic models and their suitability for subsequent controller development.
In addition, the dynamic modelling of the CDFR is established based on the Euler–Lagrange formulation. This approach systematically incorporates kinetic and potential energy terms to derive the equations of motion for the robot. The resulting model captures the nonlinear effects introduced by cable elasticity, joint coupling, and load-dependent variations, as well as the influence of external disturbances. By applying the Euler–Lagrange framework, the dynamic equations reflect both the distributed compliance of the cable-driven structure and the complex interactions among multiple DOF. This comprehensive analysis provides fundamental insights into the system’s motion behaviour, force distribution, and stability characteristics, forming a solid theoretical foundation for designing advanced control strategies.
Third, an advanced nonlinear control strategy is proposed, combining Fast Terminal Sliding Mode Control (FTSMC) with an Extended State Observer (ESO). FTSMC is employed to guarantee finite-time convergence of tracking errors and robust trajectory tracking even under nonlinear and uncertain conditions. Compared with conventional sliding mode control, proposed approach accelerates the convergence rate and reduces steady-state error. Nevertheless, the success of FTSMC depends on accurate system state information, which is difficult to obtain in practice due to unknown parameters, modeling errors, and external disturbances. To overcome this limitation, the ESO is introduced to estimate system states and disturbances in real time with high precision. By combining FTSMC with ESO, a robust control framework is established that enhances tracking performance, disturbance rejection, and overall system stability.
Furthermore, the proposed models and control framework are validated through comprehensive simulations in MATLAB/Simulink which are conducted under diverse conditions, including parameter variations, external disturbances, and nonlinear effects, to evaluate the performance of the proposed control scheme. The results show improved tracking accuracy and robustness compared to conventional controllers. Experimental studies on the constructed prototype further confirm the feasibility of the approach. Data collected from experiments consistently demonstrate that the FTSMC–ESO method provides higher stability, better disturbance rejection, and more reliable trajectory tracking than baseline methods.
In conclusion, this thesis provides a complete framework for the study of CDFR. It integrates systematic prototype development, rigorous kinematic and dynamic analysis, and the design of an advanced nonlinear control scheme based on FTSMC and ESO. Together, these contributions advance both the theoretical understanding and practical control of CDFRs. The results not only clarify the fundamental properties of the system but also demonstrate effective methods to achieve precise and robust control under nonlinear and uncertain conditions, establishing a solid foundation for future research and application of CDFR.

목차 (Table of Contents)

• Acknowledgments i
• Contents ii
• List of Figures iv
• List of Tables v
• Abbreviations v
• ABSTRACT vii
• Chapter 1 INTRODUCTION 1
• 1.1 Overview 1
• 1.2 Research Objectives 3
• 1.3 Limitations 4
• 1.4 Outline 4
• Chapter 2 INTRODUCTION TO RESEARCH ON CABLE-DRIVEN FLEXIBLE ROBOTS 6
• 2.1 Introduction 6
• 2.2 The comparison between continuum and parallel CDFR 7
• 2.2.1 The cable-driven parallel robots 7
• 2.2.2 The cable-driven continuum robots 8
• 2.2.3 The comparison of Parallel and Continuum cable-driven robots 9
• 2.3 The structural design of CDFR 10
• Chapter 3 FORWARD AND INVERSE KINEMATIC ANALYSIS OF CABLE-DRIVEN FLEXIBLE ROBOTS 13
• 3.1 The Kinematic analysis of CDFR 13
• 3.1.1 Forward Kinematic of CDFR 13
• 3.1.2 Inverse Kinematic of CDFR 15
• 3.2 Results and discussion 16
• 3.2.1 Simulation Configuration 16
• 3.2.2 Simulation Results 18
• 3.2.3 Experimental 20
• 3.3 Conclusion 22
• Chapter 4 DYNAMIC MODELLING AND ADVANCED CONTROL DESIGN FOR CABLE-DRIVEN FLEXIBLE ROBOTS 23
• 4.1 Introduction 23
• 4.2 Dynamic Modelling 25
• 4.2.1 Preliminary 25
• 4.2.2 CDFR system modelling 27
• 4.3 Fast Terminal Sliding Mode Control 28
• 4.3.1 Fast Terminal Sliding Mode Control Design 29
• 4.3.2 Lyapunov Stability Proof 30
• 4.4 Extended State Observer 31
• 4.4.1 Extended State Observer Design 31
• 4.4.2 Lyapunov Stability Proof 33
• 4.5 Proposed Control Scheme 35
• 4.5.1 Proposed control design 35
• 4.5.2 Lyapunov Stability Proof 36
• Chapter 5 SIMULATION RESULTS 39
• 5.1 Simulation Configurations 39
• 5.2 Simulation Parameters 40
• 5.2.1 Parameter Selection for Simulation 40
• 5.2.2 Guidelines for Parameter Tuning 41
• 5.3 Simulation Results (case 1) 43
• 5.4 Simulation Results (case 2) 48
• 5.4.1 Simulation Configuration 48
• 5.4.2 Simulation Results 49
• Chapter 6 CONCLUSIONS AND FUTURE WORKS 54
• 6.1 Conclusions 54
• 6.2 Future Works 55
• Published papers 56
• A. International Journal (Submission) 56
• B. International Conference 56
• References 56