Model-Based Levitation Control of A 100 kW Bearingless Electric Motor

The use of magnetically levitated rotors for various applications, especially in pumps and compressors, has seen an unprecedented rise in the last few years. Bearingless motors combine levitation and torque production capabilities. They offer more compact footprint and require less power electronics compared to more traditional active magnetic bearing supported motors. A lot of significance has been attached to reducing cost, complexity and broadening applicability of the magnetically levitated rotors. Hence, the levitation control of rotors in such bearingless machines has become quite an interesting topic of research. Digital control strategies need to be adopted for proper levitation control of rotors. Furthermore, it has to be kept in mind that these rotors cannot afford to have too many oscillations under different environmental conditions because oscillations can eventually lead to instability and heavy losses. This thesis presents a state-of-the-art model-based digital control of the levitation of a 100 kW bearingless electric motor where the point-mass of the rotor is considered. This motor has a rated speed of 22000 rpm. The entire bearingless motor system is converted into state-space models by taking into account the bearingless machine's nominal operating points and conditions. Then, a model-based controller with Pincer's conditions, coupled with an estimator with Kalman filtering, integral action and state-command path, is implemented and tested for the levitation control. FEM derived Simulink model of the bearingless motor is tested to verify the proposed control strategies. The closed-loop poles and zeroes, step responses of the closed-loop system and the frequency responses are also recorded from the simulations. In the end, the control of the rotor is investigated with five different combinations involving controller, estimator, integrator and state-command path. Comparisons are conducted on the the proposed control strategies and conclusions are drawn based on the findings

Third International Symposium on Magnetic Suspension Technology

In order to examine the state of technology of all areas of magnetic suspension and to review recent developments in sensors, controls, superconducting magnet technology, and design/implementation practices, the Third International Symposium on Magnetic Suspension Technology was held at the Holiday Inn Capital Plaza in Tallahassee, Florida on 13-15 Dec. 1995. The symposium included 19 sessions in which a total of 55 papers were presented. The technical sessions covered the areas of bearings, superconductivity, vibration isolation, maglev, controls, space applications, general applications, bearing/actuator design, modeling, precision applications, electromagnetic launch and hypersonic maglev, applications of superconductivity, and sensors

Control System Commissioning of Fully Levitated Bearingless Machine

The bearingless permanent magnet synchronous motor (BPMSM) is a compact motor structure that combines the motoring and bearing functions based on well-designed integrated windings for generating both torque and magnetic suspension force. In order to achieve a successful high-performance control design for the BPMSM, an adequate model of the rotor dynamics is essential. This paper proposes simplified multiple-input and multiple-output (MIMO) control approaches, namely the pole placement and the linear-quadratic regulator (LQR), that allow to carry out identification experiments in full levitation. Additionally, the stability of the MIMO levitation controller is verified with the rotation tests. Compared with other recently published works, the novelty of this paper is to experimentally demonstrate that a stable fully levitated five-degrees-of-freedom (5-DOF) operation of a bearingless machine can be achieved by the proposed approach, and thereby, options for commissioning of such a system are obtained

Power-Sharing Control in Bearingless Multi-Sector and Multi-Three-Phase Permanent Magnet Machines

This paper deals with the power-sharing control of bearingless multi-sector and multi-three-phase permanent magnet machines. The proposed control strategy allows to distribute the power flows among the three-phase inverters supplying the machine during bearingless operation of the drive. The control technique is based on the extension of the vector space decomposition modeling approach. The components producing the electromagnetic torque, i.e. the q-axis currents, are controlled independently from the d-axis ones, also with the aim of managing the power flows among the three-phase systems. Conversely, the d-axis currents are exploited for the generation of the radial forces needed to levitate the rotor, while considering the compensation of the forces caused by the q-axis currents in case of unbalanced power sharing strategy. The validity of the proposed method is confirmed by simulations and experimental tests on a prototyped bearingless multi-sector permanent magnet synchronous machine. The proposed approach is a contribution to the development of advanced control systems employing multiphase drives in the field of bearingless and multiport applications

Drag reducing polymers as simple indicators of hemolytic potential in biomechanical devices

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 23-24).An experimental study was carried out to determine if drag reducing polymers can be simple indicators of hemolytic potential in biomechanical devices. Specifically, three different blood pumps, known as a left ventricle assist devices (LVADs) were operated in a test loop using an aqueous solution of polyethylene glycol (PEO, MW = 5000 kDa), a known drag reducing polymer. The pumps were operated under controlled parameters and the change in viscosity (cP) and drag reduction (%DR) for each pump was monitored over the specified time period. The CentriMag® (CM) was used to confirm the drag reducing behavior of PEO, while HeartMate® II (HM II) and HeartMate® III (HM III) were used to determine if there was a correlation between experimental results and actual hemolysis results. Experimental results showed that the mathematical difference between the average final and initial viscosity of HM II was greater than the difference for HM III. HM II had a difference of 0.21 cP and HM III had a difference of 0.16 cP. Hemolysis results using bovine blood showed that HM II had a higher hemolysis rate of 3.80 +/- 1.11 g/day and a higher milligram normalized index of hemolysis of 0.0393 +/- 0.0155. The average hemolysis rate for HM III was 1.38 +/- 0.63 g/day and the milligram normalized index of hemolysis (mg N.I.H.) was 0.571 +/- 0.333. This positive correlation shows that PEO can be a simple indicator of hemolytic potential for biomechanical devices. More data and experimentation is needed to further understand the behavior of PEO and it's ability to indicate hemolytic potential using a wider range of biomechanical devices.by Sarah Shieh.S.B

Magnetic Bearings

The term magnetic bearings refers to devices that provide stable suspension of a rotor. Because of the contact-less motion of the rotor, magnetic bearings offer many advantages for various applications. Commercial applications include compressors, centrifuges, high-speed turbines, energy-storage flywheels, high-precision machine tools, etc. Magnetic bearings are a typical mechatronic product. Thus, a great deal of knowledge is necessary for its design, construction and operation. This book is a collection of writings on magnetic bearings, presented in fragments and divided into six chapters. Hopefully, this book will provide not only an introduction but also a number of key aspects of magnetic bearings theory and applications. Last but not least, the presented content is free, which is of great importance, especially for young researcher and engineers in the field

Development of a Pediatric cardiac assist Maglev pump for use with a universal driver system.

Heart failure (HF) remains the leading cause of death, affecting 26 million adults worldwide and 6.5 million adults in the United States. Pediatric HF patients have been a historically underserved population with few options for mechanical circulatory support (MCS) therapy, a leading treatment as an alternative to heart transplantation. To address this clinical need, the Inspired Universal MagLev System is being developed; a low cost, universal magnetically levitated extracorporeal MCS system with interchangeable single-use pumps that will ultimately provide adult and pediatric patients ventricular and respiratory assist therapies. The Inspired Pediatric VAD is the first single-use pump application for this MCS system and is specifically designed for pediatric circulatory support. This dissertation describes the development efforts to design and evaluate iterative impeller and pump housings for the Inspired Pediatric VAD. Requirements for the Inspired Pediatric VAD design include the need to generate the appropriate hemodynamic parameters (pressures and flows) for pediatric patients, and miniaturization of the pump and impeller to accommodate the pediatric population. Traditional pump theory and design methods were applied to aid in the unique design of the VAD impeller and pump housing, resulting in multiple design iterations. Two impeller and pump designs (V1, V2) were virtually constructed using computer-aided design (CAD) software. Three-dimensional flow and pressure features were analyzed using computational fluid dynamics (CFD) analysis. Simulated pump designs (V1, V2) were operated at 15% higher rotational speeds (~5000 rpm) than initially estimated (4255 rpm) to achieve the desired operational point (3.5 L/min flow at 150 mmHg). V2 design outperformed V1 by generating up to 30% higher pressures at all simulated rotational speeds and with 5% lower priming volume. Simulated hydrodynamic performance (flow, pressure and hydraulic efficiency) of VAD V2 compared favorably to current commercially available MCS devices. A prototype of the Inspired Pediatric VAD V2 was fabricated, the magnitude and range of hydraulic torque and forces of the impeller were quantified, and the hydrodynamic performance benchmarked. A static mock flow loop model containing a heated blood analogue solution was created to test the pump over a range of rotational speeds (500 - 6000 RPM), flow rates (0 - 3.5 L/min), and pressures (0 to ~420 mmHg). The device was initially powered by a shaft driven DC motor, which was used to calculate the fluid torque acting on the impeller. Additional CFD simulations of VAD V2 were compared against the empirical bench-top data at select rotational speed and flow rate conditions. Empirically, the pediatric VAD produced flows as high as 4.3 L/min against a pressure of 127 mmHg at 6000 RPM. Based on the performance of the first two VAD design iterations, a final design iteration, VAD V3, was achieved. Hydrodynamic performance of VAD V3 was numerically assessed using CFD simulations. The results indicated no change in flow and pressure head performance compared to the previous device design (V2). Shear stress and flow residence time volumetric distributions were generated over a range of pump rotational speeds and flow rates. At the lowest pump operating point (3000 RPM, 0.50 L/min, 75 mmHg), 79% of the pump volume was in the shear stress range of 0 – 10 Pa with \u3c 1% of the volume in the critical range of 150 – 1000 Pa associated with potential for increased risk of clinically-significant blood damage. At higher speed and flow (5000 RPM, 3.50 L/min, 176 mmHg), 65% of the volume resided in the 0 – 10 Pa range compared to 2.3% at 150 – 1000 Pa. The initial results from the computational characterization of the Inspired Pediatric VAD V3 were encouraging, and based on the overall research performed to date, future work will include pre-clinical testing of VAD V3 in static and dynamic mock flow loop and acute large animal model studies to further assess device function, hydrodynamic performance, hemodynamic response, and hemocompatibility

Studies on 1-Axis Self-Bearing Motor at Low Temperature

九州工業大学博士学位論文 学位記番号：工博甲第523号 学位授与年月日：令和3年3月25日第1章 序論|第2章 １軸制御型セルフベアリングモータの開発|第3章 セルフベアリングモータの低温用遠心ポンプへの応用|第4章 ゼロパワー制御を用いた磁気軸受の温度補償|第5章 ゼロパワー制御を用いた温度補償のセルフベアリングモータへの応用|第6章 結論九州工業大学令和2年