THE MINISTRY OF EDUCATION AND TRAINING THAI NGUYEN UNIVERSITY NGUYEN THI THANH BINH Title: IMPROVING THE CONTROL QUALITY OF MAGNETIC BEARINGS Speciality: Control Engineeering and Automation. Research code: 62.52.02.16 DOCTORAL DISSERTATION ABSTRACT Supervisors 1. Prof. Dr Do Khac Duc 2. Assoc.Prof. Dr Nguyen Nhu Hien Thai Nguyen - 2013 Training Institution: Thai Nguyen University of technology – Thai Nguyen University. Supervisors 1. Prof. Dr Do Khac Duc 2. Assoc.Prof. Dr Nguyen Nhu Hien Phản biện 1: PGS. TS. Bùi Quốc Khánh Phản biện 2: PGS. TS. Phạm Ngọc Tiệp The dissertation will be defended in front of council in Univeristy Level at: Trường Đại học Kỹ thuật Công nghiệp Thái Nguyên - Đại học 1 DOCTORAL DISSERTATION ABSTRACT Introduction Overview There is no direct contact between the stationary and moving parts, so the magnetic bearings has important applications and efficiency for the rotating machines with high speeds (from 5000 r/ min to 10,000 r/min), requiring great precision, working in environments not using lubricants (temperature, pressure very high or very low). Currently, research is focusing on the following four directions: 1.1 Research and apply in industrial and biomedical devices. 1.2. Research to reduce the size of the magnetic bearing. 1.3. Research to work in special environments such as vacuum, temperature, pressure very high or very low 1.4. Research to apply modern controllers. Dissertation’s content will research following the 4 th trend. Motivation of topic Unlike mechanical bearings, magnetic bearings have no contact between the stationary and moving elements. Thus, magnetic bearings used in electric motors are considered as an advanced and environmentally friendly technology. They strongly contribute in raising the rotational speed to the engine and help the engine be applied in the special environment that common engine with ball mechanical bearing can not work or work with very high maintainance cost. The studies about magnetic bearings typically are in the developed countries such as Japan, America, France, Germany and Switzerland. Currently, the applicability of electric motor using magnetic bearings is necessary in many areas; the study of manufacturing electric motors using magnetic bearings and applications is also being promoted in developing countries such as China, Korea, Brazil 2 Magnetic bearings used in electric motors currently classify as the high-tech products containing many levels of intelligence and also the new green technology products, although there are limitations in the use of wide available due to the large size and high cost but in the near future when the researchers succeed in reducing the cost, the replacement of electric motor using magnetic bearings in the field of clean technology, medical equipment, defense equipment and industrial space, will be inevitable. The important part of the magnetic bearings is the controller. Currently the controller for the magnetic bearings is low quality as maladaptive, unsustainable, control signals are not limited. This fact is due to the dynamics of the magnetic bearing is highly nonlinear, and the method of designing the controller for nonlinear systems (including magnetic bearings) under the effect of external disturbance and containing changing parameters during operation have not been studied and developed completely in order to the apply to design the controller to ensure that the magnetic bearing is capable of performing well in any mode working. So study to design the controller in order to improve the quality of magnetic bearing is necessary. Objects and scope of research - Controlling radial magnetic bearing 4 DOFs, in the drive system using synchronous electric motors, stimulating by permanent magnet and blocking motion along axis, working with high speed. - The research of this dissertation limits in building mathematical description having the impact of disturbance and uncertainty parameters to synthesize nonlinear control system under the equation Euler - Largrange (EL) with enough structure - nonlinear channel separation, to improve the control quality compared with classical linear control system. 3 Research Methodology - Based on the mechanical, electrical and magnetic laws to calculate dynamics for a radial magnetic bearing 4 DOFs. - The mathematical description of the radial magnetic bearings 4DOFs in the form of EL. - Design the controller of nonlinear channel separation for the magnetic bearings. - Research magnetic bearing by simulation. - Empirical study on the magnetic bearing. The content and scope of the problem will be studied in depth, resolution and prospects for achieving results - Develop mathematical description of magnetic bearing 4 DOFs, under the radial force. - Design to control nonlinear channel separation for system under the effects of noise and uncertainty parameter. - Simulations and experiments on the control system in laboratory equipment. The theoretical and practical meaning of topics - This is a new problem to be studied in Vietnam and is one of the first scientific studies of the magnetic bearings announcing in Viet Nam and is a new research direction having highly promising application in scientific research… - The results of the research will be the reference to students and graduate students. From the results of the research will serve as a basis for many subsequent studies, in order to widespread application of the electric magnetic bearing to drive system in Vietnam, especially in systems with special requirements (speed high, high or low temperature, vacuum, not lubrication, ). Layout of the dissertation The dissertation consists of 4 chapters, 97 pages (including references), 61 references, 64 figures and graphs. 4 Chapter 1: Overview of the magnetic bearing 1.1. The concept of the shaft and drive shaft bearing - Presentation of the basic concepts of bearing and magnetic bearings - Classification of magnetic bearings and identifying the research object is active magnetic bearings (AMB). - Trình bày nguyên lý nâng dùng lực từ a) Displacement sensor Controller Power amplifier b) Figure 1.6: a) Shape and b) the basic elements of magnetic bearing Contro ller Electromagnetic actuator Power amplifier Rotor Rotor Rotor weight mg Magnetic force f m Electromagnetics (Stator) Sensor Figure 1.7: Structure of AMB 1 DOF 5 1.2. Theory, research-orientation of topics 1.2.1. Overview of research in Viet Nam and in the world 1.2.2. Research in the Viet Nam In Vietnam today only at Hanoi University of Technology and Thai Nguyen University of Technology are now studying. 1.2.3. Research in the world Presenting some of the results of research works from around the world in recent years from 2003 to 2009. 1.3. Conclusion of Chapter 1 Chapter 1 has solved some problems: - Introducing the most generalized definitions of bearing and magnetic bearing. - Select the type of active magnetic bearings to research. - Orientation of research is to apply modern control methods to control the magnetic bearings in the drive systems. - Propose the control method PD to compensate gravity, nonlinear channel separation based on EL description for the enough structure system to design controller for the magnetic bearing system. On the basis of preliminary studies on the magnetic bearing, chapter 2 will study in depth the dynamics of magnetic bearing under radial force to describe mathematically the drive system using magnetic bearings 4 DOFs. Chapter 2: The mathematical description of the active magnetic bearing 2.1. Introduction Principles of magnetic bearing are a electric magnet instead of creating shaft torque, it generates displacement forces in the x and y axis, these forces are automatically adjusted to maintain the gap between stator and rotor around the nominal value 6 2.2. Mathematical basis of magnetic levitating system - According to [1] magnetic levitating system was studied on the basis of approximations based on assumptions such as: flux is closed completely in the ferromagnetic core, not consider at the saturation mode etc - The calculation is based on the average length of the path of magnetic field and the length of the air gap to the nominal value x 0 . 2.2.1. Magnetic flux density of the magnetic circuit With these assumptions have not leakage flux, we have: 0 0 I 0 0 0 0 2 1 2 a C C I r r a r r S Ni Ni x l l l l x S                                (2.6) 2.2.2. Reluctance R and the inductance L of the magnetic circuit The components of magnetomotive force, flux, relectance and the invariable magnetic circuit are considered as components corresponding to the voltage, current, resistance and power (DC) in the circuit. The main difference is that reluctance is an energy storage component rather than dissipating energy component. Source "DC" – N i performs for the magnetomotive force due to the currents on the coil generated. 2.2.3. Electromagnetic force including the magnetic saturation of core of steel Electromagnetic force including the magnetic saturation of core of steel is determined [1]: 2 2 2 2 a 0 a 0 a 2 2 0 C I C I 0 0 r r r r W 2 S N i S N i 1 F x 2 l l l l 2x 2x                                 (2.16) 2.2.4. Electromagnetic force not including the magnetic saturation of core of steel 7 Figure 2.3. Some of the typical structure of the active magnetic bearing Electromagnetic force not including the magnetic saturation of core of steel is determined [1]: 2 2 2 2 2 0 a 0 a 0 a 2 2 0 0 0 Ni 1 i i 1 F S N S K ; K N S 2x 4 x x 4                    (2.17) 2.2.5. The relationship between electromagnetic forces and currents in the AMB When changing the current i compared to the nominal polarized current i 0 , it will alter the electromagnetic force and after transforming, we have the basic equation to describe the motion of an object is levitated by the electromagnetic force in a fixed direction [23]: a n mx K i K x    (2.24) The model built for magnetic bearing from the above will be generalized for magnetic bearings 4DOFs. 2.3. Building a mathematical model of magnetic levitating system using 4 poles 2.3.1. The structural form of the current magnetic bearing and researching trend. 4-pole active magnetic bearing is actively promoted to research [5, 6], [14, 15] and is attracting the attention of many manufacturers (Synchrony, Mutecs). This is the trend that author will research. 8 2.3.2 Structure of the magnetic levitating system 4 degrees of freedom 2.3.3 Building the mathematical model This part studies to build mathematical model of the magnetic bearing 4 DOFs based on the analysis of the equivalent circuit diagram of the motion x, y. After analyzing and transformation, we have a mathematical model describing the magnetic bearing: The total flow of flux: 0 1 1 1 1 0 2 2 2 0 0 1 2 0 1 1 1 1 0 2 2 2 0 0 1 2 0 2 2 2 2 0 2 2 2 0 0 1 2 2 2 ( ) ( ) ( ) (2 ) ( ) (2 ) p x x xc bx p x x xc bx p x x xc bx x xc bx H x x Ni S x x x x H x x Ni S x x x x H x x Ni S x x x x                                                                                        0 2 2 0 2 2 2 0 0 1 2 (2.30) ( ) (2 ) p x H x x Ni S x x x x                                                  Radial active magnetic bearing Radial active magnetic bearing Actuator and Sensor Control System (Hardware and Software) Control System Interface [...]... technology, Thai Nguyen University, Vol 1, 1-2008 8 "Research on the non-contact drive system using the magnetic suspension," the ministry level project, code: TN01-B2009-08 Project manager: Nguyen Thi Thanh Binh . THE MINISTRY OF EDUCATION AND TRAINING THAI NGUYEN UNIVERSITY NGUYEN THI THANH BINH Title: IMPROVING THE CONTROL QUALITY OF MAGNETIC BEARINGS Speciality: Control. Prof. Dr Do Khac Duc 2. Assoc.Prof. Dr Nguyen Nhu Hien Phản biện 1: PGS. TS. Bùi Quốc Khánh Phản biện 2: PGS. TS. Phạm Ngọc Tiệp The dissertation will be defended in front of council. is active magnetic bearings (AMB). - Trình bày nguyên lý nâng dùng lực từ a) Displacement sensor Controller Power amplifier b) Figure 1.6: