Student Number 90323119 Author Wei-Feng Kang(康瑋峰) Author's Email Address No Public. Statistics This thesis had been viewed 2661 times. Download 2468 times. Department Mechanical Engineering Year 2002 Semester 2 Degree Master Type of Document Master's Thesis Language English Title Improving contouring accuracy of high-feed CNC machine tools Date of Defense 2003-07-07 Page Count 47 Keyword feedforword control friction quadrant glitches Abstract As the development in industry, time and quality are more and more important in manufacturing industry. Therefore, automatic manufacturing machines are tending to high speed and high precision. This thesis is aimed to eliminate tracking error of traveling a circular profile on the CNC machine tools. Friction is one of the most significant source of nonlinear disturbance for the motion control which caused by the relative motion of different contact surface at the low velocity. The nonlinear component of friction such as static friction (stiction) and the Coulomb friction should be overcome so that the tracking error will be eliminated. When the X-Y tables are tracking a circular profile, quadrant glitches appear at ninety degrees intervals, i.e. the motion of one axis has a zero velocity crossing and reverses direction.
The quadrant glitches were due to friction brought about transient phenomenon. Therefore, we will solve the transient phenomenon. We will make the system to reach steady state quickly, we may anticipate compensating a value when the motion of one axis has a zero velocity crossing and reverses direction. We will observe the system dynamic before traversing a circular profile, and to obtain a compensated value on off-line.
In addition, we designed the feedforward and P feedback tracking controllers. The research adopts feedforward controller to improve the tracking performance of the system.
Finally, the above servo loop control of tracking a circular profile on CNC machine tools is verified by the simulation and experimental results.
Table of Content 摘要i
第四章 PC BASED CNC 架構介紹及實驗架構vi
TABLE OF CONTENTSIII
LIST OF FIGUREV
LIST OF TABLESVII
LIST OF TABLESVII
CHAPTER 1 INTRODUCTION1
1.1BACKGROUND AND MOTIVATION1
CHAPTER 2 INTRODUCTION TO QUADRANT GLITCHES AND FRICTION COMPENSATION4
2.1.1 Low Velocity Friction5
2.1.2 Model of Friction7
2.1.3 Transient phenomenon due to friction9
2.2 FRICTION COMPENSATION12
CHAPTER 3 DESIGN OF TRACKING CONTROLLERS14
3.2 SERVO CONTROL ANALYSIS OF CNC MACHINE TOOLS14
3.3 FEEDFORWARD CONTROLLER16
CHAPTER 4 INTRODUCTION TO PC BASED CNC19
4.1 INTRODUCTION TO PC BASED CNC CONFIGURATION19
4.1.1 Motion Control Card (PCC1620)20
4.2 EXPERIMENT FRAME24
4.2.1 System Model27
CHAPTER 5 EXPERIMENT RESULTS AND DISCUSSION30
5.1 CONFIGURATION OF EXPERIMENT30
5.2 EXPERIMENT RESULTS31
5.2.1 Experiment Results of the friction compensation of traversing a circular profile32
5.2.2 Experiment Results of applying the feedforwad control to enhance contouring motion precision39
CHAPTER 6 CONCLUSION AND FUTRUE WORK45
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Advisor Pi-Cheng Tung(董必正)
90323119.pdf Date of Submission 2003-07-08