Control of Multiple Degree of Freedom Fast Tool Stages for Noncircular Turning Process : 비원형 회전가공을 위한 다중자유도 기구 제어

다국어 초록 (Multilingual Abstract)

"There are a lot of cases in the industrial control area where the reference and/or disturbance signals are periodic. To utilize this specific characteristic of the periodic signal in control system design, a variety of repetitive controllers has been developed and applied to several applications. One of the manufacturing applications is the noncircular turning process.
The goal of the proposed research is to extend the capability of the noncircular turning process. The major work of this research can be divided into three sections:
(1) A prototype variable rake angle mechanism has been developed and controlled. The objective of the variable rake angle mechanism is to provide another degree of freedom to the conventional noncircular turning process in parallel fashion, so that the rotational tool mechanism can compensate for the rake angle change caused by the noncircular cam profile itself. Kinematics, dynamics, and design of the variable rake angle mechanism are discussed. The equations of motion of the variable rake, angle mechanism are derived and numerical analysis of the equations of motion is presented. Experimental results on the variable rake angle mechanism support the design concept and control approach.
(2) A robust repetitive controller is designed for a dual stage actuator system and it demonstrates the tracking performance improvement through a dual stage actuator system. The dual stage actuator system has a piezoelectric actuator inside of the hollow piston of an electrohydraulic actuator system, so it has another degree of freedom in serial fashion in addition to the main tool motion. Cascading two SISO control loops results in the squaring effect on the overall sensitivity function and improves the tracking performance. Experimental and simulation results show the effectiveness of the dual stage actuator system for the noncircular turning process.
(3) A new discrete-time robust repetitive controller design with improved performance is proposed. The basic idea to improve the tracking performance at fundamental frequencies is to achieve the squaring effect on the sensitivity function. The fundamental frequencies are defined as integer multiples of the frequency of the periodic signal. Conceptually, the goal is the same as that of the dual stage actuator system, even though it is proposed to use the modified q(z, z-1) filter structure instead of adding another actuator stage in series. It is shown that this design method improves not only tracking performance but also robustness for small variations in the period of the periodic signal. A systematic controller design methodology is presented to guarantee the robust stability. Experimental and simulation results from an electrohydraulic actuator system validate this approach.

목차 (Table of Contents)

• Chapter 1 Introduction = 1
• 1.1 Scope of this Research = 1
• 1.2 Literature Review on Repetitive Control = 3
• 1.3 Overview of this Dissertation = 5
• Chapter 2 Development and Control of a Variable Rake Angle Mechanism = 8
• 2.1 Introduction = 8
• 2.2 Design of the Variable Rake Angle Mechanism = 10
• 2.3 Kinematics, Dynamics and Modeling = 17
• 2.3.1 Kinematics and Stiffness = 17
• 2.3.2 Formulation of the Equations of Motion via Lagrange's Equations = 23
• 2.3.3 Numerical Evaluation of the Equations of Motion = 32
• 2.3.4 Modeling = 35
• 2.4 Robust Repetitive Controller Design and Experimental Results = 38
• 2.5 Chapter Summary = 47
• Chapter 3 Control of a Dual Stage Actuator System for Noncircular Cam Turning Process = 48
• 3.1 Introduction = 48
• 3.2 Modeling of the Dual Stage Actuator System = 50
• 3.3 Robust Repetitive Controller Design = 55
• 3.3.1 Finite Wordlength Errors and Optimal Realization = 61
• 3.4 Simulation and Experimental Results = 72
• 3.5 Chapter Summary = 76
• Chapter 4 Robust Repetitive Controller Design with Improved Performance = 80
• 4.1 Introduction = 80
• 4.2 Robust Repetitive Controller Design = 83
• 4.2.1 The Sampling Theorem: Spectral Sampling = 83
• 4.2.2 Modified q(z, z-1 ) Filter Structure = 85
• 4.2.3 Proposed Design Method = 89
• 4.3 Design Example: Simulation and Experimental Results = 95
• 4.4 Chapter Summary = 102
• Chapter 5 Conclusions = 103
• 5.1 Summary of Main Results = 103
• 5.2 Recommendations for Future Research = 105
• Appendix = 107
• A.1 Models and Controllers for the Variable Rake Angle Mechanism = 107
• A.2 Discrete-Time Plant Models and Controller Realizations for the Dual Stage Actuator System = 110
• A.3 Design Parameters and Controller Realizations for the Design Example in Robust Repetitive Controller Design with Improved Performance = 113
• References = 117
• Vita = 123