There are few self-gap-detecting electromagnetic suspension (EMS) systems robust enough against variation of coil resistance. The authors succeeded in providing much robustness against the variation of coil resistance with a self-gap-detecting EMS system. An adaptive control for coil resistance and an exciting voltage compensator for differences between the coil resistances were applied to the self-gap-detecting EMS system. This paper proposes this new self-gap-detecting technique. The adaptive controller and the exciting voltage compensator will be explained. The experimental results will show a validity of the technique.
Worldwide high speed Maglev (> 400km/h) developments refer to Maglev such as the Japanese JR-Maglev MLX, the German Transrapid and the USA Inductrack Maglev. Other world projects exist such as the Japan HSST (< 300km/h) and the China HTC. The JR-Maglev, the Transrapid and the HSST have reached industrial levels. The Swissmetro Project presents a unique aspect of Maglev: it is designed to work under partial vacuum (< 10kPa) in two tunnels and for high speeds (>400km/h). The authors investigate new possibilities to combine both the propulsion and the levitation. In order to minimize the heat due to the motor levitation and guidance losses, a polarized excitation is proposed. The use of permanent magnet NdFeB for the excitation is still not applied for high speed Maglev, requiring mechanical power greater than 6MW. Such a solution only appears in Urban Rapid Transit Maglev (<160km/h), such as the USA MagneMotion M3 and the General Atomic Urban Maglev. For Swissmetro, the authors study the polarized inductors for the levitation, implying a polarized synchronous linear motor. The polarization is obtained with permanent magnets NdFeB. This paper presents some key issues related to such technical choices. The motor design is described and the power balance is presented. The thermal behavior is analyzed using a numerical platform of the complete vehicle-tunnel system, based on computation of the air flow dynamic.
Recently, pumps used in extremely low temperature such as 77K are found to be necessary. They are expected to use for rocket engines and hydrogen stations for fueled vehicles. Generally, conventional magnetic bearings do not work in the extremely low temperature. Therefore, we have studied magnitic bearings for these pumps. Self-sensing technique is tried to apply to magnetic bearings. If self-sensing magnetic bearings were made, we could apply the self-sensing magnetic bearing to liquid nitrogen pumps. In this paper, we propose a prototype self-sensing magnetic bearing and study the static and dynamic characteristics. The dynamic characteristics in the air and in liquid nitrogen are also discussed.
We propose a magnetic levitation system for an X-Y Linear Synchronous Motor (LSM). This system uses an X-Y LSM armature as the primary side and a 4-pole-type yoke hybrid electromagnet for the secondary side. There are some advantages in using a magnetic levitation system for an X-Y LSM, including decreased friction and abrasion due to the non-contacting operation. In this paper, I-PD(integral- proportional-derivative) control was used for the 4-pole-type yoke hybrid electromagnet, and the controller was designed with a Kessler form, a Manabe form, and with state feedback control. We compared the characteristics associated with changes in the gap for the different cases.
This paper analyses the dynamic performance of flat single-sided Permanent Magnet Linear Synchronous Motors (PMLSMs) employed as actuators, when the alternate motion and the attractive or repulsive forces between the primary and the secondary are controlled simultaneously. The control of the normal forces when the motor is in dynamic operation provides multiples advantages, such as the reduction of friction forces and audible noise, and the minimization of mechanical stresses of guides and supports. Two PMLSM prototypes, one with a ferromagnetic primary core, and another with a non-magnetic armature, were tested under these special operation conditions. A modified Rotor Flux Oriented Control (RFOC) strategy was employed to carry out the tests, and several conclusions were taken. The main purposes of this study are to show the feasibility of the simultaneous control of motion and normal forces employing vector control techniques and to analyse the dynamic response of the prototypes.
Dealing with position control of Linear Induction Motors (LIM), most strategies in bibliography are based on Secondary Flux Oriented Control (SFOC) and Direct Thrust Control (DTC). However, SFOC of linear induction motors needs complex identification methods to compensate parameter variation during operation, mainly due to local heating and end-effects. On the other hand, DTC based methods for LIMs present thrust ripple and have problems at low and zero speeds. In this paper, a new Indirect Thrust Control (ITC) based strategy for position control of linear induction motors that makes up for these drawbacks is presented. The position control loop design methodology and the method for automatic adjustment of compensators are described. Experimental results are presented to evaluate the performance and sensitivity of the control strategy. Finally, some conclusions are drawn about the applicability of the new algorithm that demonstrate the main advantages versus SFOC and DTC.
The successful extension of semiconductor technology to fabricate mechanical parts of the sizes from 10 to 100 micrometers opened wide ranges of possibilities for micromechanical devices and systems. The fabrication technique is called micromachining. Micromachining processes are based on silicon integrated circuits (IC) technology and used to build three-dimensional structures and movable parts by the combination of lithography, etching, film deposition, and wafer bonding. Microactuators are the key devices allowing MEMS to perform physical functions. Some of them are driven by electric, magnetic, and fluidic forces. Some others utilize actuator materials including piezoelectric (PZT, ZnO, quartz) and magnetostrictive materials (TbFe), shape memory alloy (TiNi) and bio molecular motors. This paper deals with the development of MEMS based microactuators, especially linear drives, following my own research experience. They include an electrostatic actuator, a superconductive levitated actuator, arrayed actuators, and a bio-motor-driven actuator.
This paper deals with an application of H∞ DIA control to the magnetically levitated steel plates. Our goal in this research is to suspend two thin steel plates stably by using four electromagnets without any physical contacts. We apply the robust H∞ DIA control approach to the magnetically levitated steel plates. The H∞ DIA control problem treats a mixed Disturbance and an Initial state uncertainty Attenuation and it is expected to provide a good transient property to a control system. Experimental results show that the proposed robust control approach is effective for suppressing an elasticity vibration of steel plates.
This paper presents electrostatically controlled linear inchworm actuator for precise step and parallel motion. Electrostatically controlled linear inchworm actuator can provide a high accuracy (nm order), a large stroke (mm order) and parallel motion of multi sliders. Micro electro mechanical systems technology allows batch fabricated multi sliders. Batch-fabricated multi sliders can be driven by a proposed strategy based on an inchworm motion. Electrostatically controlled linear inchworm actuator employs an electrostatic clutch mechanism in order to control motion transmission from a piezoelectric oscillator to multi sliders for the inchworm motion. Independent control of motions of multi sliders arranged on a single driving system with the piezoelectric oscillator will be presented. This paper reports design, fabrication and demonstration of a proposed system, followed by a prospect of our study toward dynamic gain equalizer as optical application.
The paper presents a design procedure for a novel linear electromechanical actuator from a basic concept to a prototype with optimized characteristics. The actuator itself is a complex electromechanical system combining features of the active magnetic bearing (suspended mass in the order of 0.3kg) and the linear Lorentz actuator (long stroke range—50mm). During the design procedure the analysis and selection of the magnetic materials are carried out. A parametric search with respect to main design variables is performed. Special attention is paid to the development of the analytical model that is an essential tool for future optimization. A design procedure leads to modifications in dimensions and coils arrangement. An improved prototype is designed and manufactured. The results obtained by the finite element method (FEM) and analytical modeling are validated by measurements.
The paper reports the results of levitation tests carried out by using an experimental ring device employing a cooled high critical temperature superconductor ring interacting with magnetic field generated by two different types of circular tracks. The tracks are composed of homopolar permanent magnets arranged in loose soft iron slot with and without magnetic side rims. The experimental device reproduces, by analogy, the magneto-dynamic behaviour of a magnetically levitated vehicle with superconductors on board, riding above a magnetic guideway. Two types of inductors have been replaced on the experimental device achieving two different configurations of system that are described and examined. Lift and guidance forces have been tested in a wide range of work conditions and the levitation performances are compared and discussed.
Diamagnetic levitation is the only passive levitation at room temperature. It is interesting to use this principle for a contactless conveyor in applications where friction and wear-particle contamination should be avoided such as in a microfactory. Using planar arrangements of permanent magnets, it is indeed possible to levitate a conveyor made of diamagnetic materials. In this article the authors are investigating the use of diamagnetic levitation in conjunction with various contact-less drive concepts to design a totally contact-free conveyor to carry small components in microfactories.
The author has been active in the development of levitation devices for precision positioning during the last 18 years. Principal among the techniques studied has been the use of two-force or levitation linear motors. These motors have been designed into stages for precision positioning in lithography, scanned probe microscopy, and other precision measurement systems. In such devices, the use of levitation linear motors allows the control of six stage degrees of freedom to nanometer resolution with a single moving part. This paper presents an overview of the operating principles, electromagnetic configurations, and system level performance of levitation linear motors for precision applications. The configuration of such motors is most commonly an iron-free permanent magnet array in the Halbach configuration which is driven by an iron-free multiphase coil set. By properly choosing the phase drive currents, forces in levitation and translation can be controlled. This opens possibilities for novel positioning system configurations and performance capabilities.
Currently, the demand for high force density linear actuators is being met almost exclusively by employing a leadscrew and nut to transform rotary motion to linear motion. This paper describes an alternative technology, viz. a linear magnetic gear, which employs rare-earth magnets and which could be used in conjunction with a conventional linear actuator. Simulation studies have shown that such a gear has a highly competitive force transmission density.
An accurate thrust control of permanent magnet linear synchronous motors (PMLSM) is more efficient with a fine knowledge of the harmonics value of the electromotive force (EMF). This is often difficult to obtain experimentally for a PMLSM. As a consequence, this paper deals with the study of the non-sinusoidal EMF of a PMLSM using the 3D Finite-Element Method (FEM). Two potential formulations are used to consider several cases. Afterwards, for the same accuracy, the computation times are examined. The results of the FEM are compared to those given by the measurements from a test bench composed of a Siemens LIMES400/120 linear motor and a dSPACE DS1005 real-time controller board. Finally, the advantages and the limitations of the FE Analysis will be discussed.
A three axes synchronous linear permanent magnet excited motor consisting of solid spherical shaped stator and rotor yokes is used to adjust an air borne telescope for infrared starlight observation. Details of the motor design and measurements of the completed motor system will be presented.
This paper presents how to compensate for the non-sinusoidal electromotive force (EMF) of the permanent magnet linear synchronous motor (PMLSM) with a multiple-frequency resonant controller. After the modeling of the non-sinusoidal EMF in a PMLSM, the multiple-frequency resonant controller is proposed to control the PMLSM in order to compensate for the negative influence of such EMF. After explaining the discrete resonant controller theory, the effectiveness of the suggested method is verified on a test bench equipped with a Rexroth LSP120C linear motor and a dSPACE DS1005 real-time controller board.
This paper proposes a new force sensor-less robust tracking servo system, which detects and suppresses both the periodic disturbance and the sudden disturbance without force sensor. The proposed system estimates both the periodic disturbance and the sudden disturbance by using a new sudden disturbance observer and the memory of tracking error. In the proposed system, the influence of sudden disturbance is suppressed by the proposed sudden disturbance observer. On the other hand, the influence of periodic disturbance is suppressed by means of ZPET feed-forward servo system, respectively. The experimental results point out that the proposed tracking servo system has a precise tracking response against both the periodic disturbance and the sudden disturbance.
In this paper, the voltage sag compensation by parallel type compensator with series inductor is presented. The parallel type compensator injects the current into the system so that the voltage across the series inductor can instantaneously compensate the voltage at the load. The three types of current injection control schemes are explained, analyzed and compared. The effect and solution for compensating voltage sags by parallel type compensator with series inductor are explained. Simulations of voltage sag compensation demonstrated the validation of the proposed control schemes.
A newly proposed Energy-Compensating Active Control is implemented to reduce the return current noise which is caused by inverter-driven electric car systems. The Energy-Compensating Active Control detects the energy charged at the filter capacitor, reduces the energy and current of the noise frequency component by simple feedback loop incorporated with the conventional motor torque controller. No additional sensors or circuit arrangements are necessary, therefore the return current can be attenuated effectively without any further cost. The return current with an inverter system is measured using a current probe and a FFT analyzer, and it is shown that the 25Hz noise current is reduced by up to 10dB with the control. The results explain that the low frequency return current noise can be attenuated with the simple control scheme, which would expectedly reduce the size of filter reactors and capacitors to meet with the current limit level of signaling system's track relays.
A zero-bias-current self-sensing active magnetic bearing is proposed. One degree-of-freedom (DOF) of the rotor is controlled by a pair of electromagnets which are alternatively energized by the proposed circuit. The rotor position of the one DOF is measured by using both electromagnets: the non-energized electromagnet also contributes to the position sensing. The proposed method gives good linearity in the position estimation. The controller of the magnetic levitation consists of a digital signal processor, DSP, which compensates the nonlinearity of the magnetic force and achieves good damping. In the experiment, the rotor can run at 45000min-1.
New type of remote support system for handicapped persons is proposed in this paper. Body-Braille system is consisted of six small vibrators which have been used in cellular phones. And this system is put on the any part of human body. Supports method are similar to usual Braille, and the impaired persons acquire the communication or information about circumferences by reading the vibration patterns on the skin which are consisted of six on-off vibrations of small motors. This paper has shown the remote support system and experiment in which Body-Braille system and cellular phone are connected to realize its functions. The deaf-blind persons have cellular phone with small camera, and remote supporter can get the necessary information by receiving images from the phone, and then send recognition result to subject using Body-Braille. From the results of the experiment, proposed support system has been clarified to be effective.
This paper verifies experimentally validity of the dynamic vector simulators for self-excited hybrid-field synchronous motors (SelE-HFSMs) that have rotor field by both permanent magnet and diode-shorted field winding. The dynamic vector simulators in form of vector block diagrams was originally proposed by the author and have attractive features and usefulness. Its validity has been confirmed in sense of consistency with the associated dynamic mathematical models, but not from viewpoints of experiments using actual SelE-HFSMs. This paper verifies experimentally the validity.
For small induction motors, various methods to measure the inertia moment have been proposed. And these methods are relatively easy and the accuracy is also expected. In this letter, it is proposed to determine the mechanical loss by the deceleration method assuming the value of the inertia moment to be known.