Zero-power Control Research Articles

Design of Zero-Power Control Strategy With Resisting Tilt of Hybrid Magnetic Levitation System

Traditional multipoint hybrid maglev systems cannot realize the zero-power horizontal levitation state under eccentric load, which means the steady-state current is zero, and the air gap of each magnet is equal. This article proposes a new maglev system with two rotary magnets to solve this problem. The two magnets can move on an annular guideway to counteract the moment caused by the eccentric load. At first, we established the linear parameter varying model of this maglev system. Then, the control strategy is designed, which consists of a zero-power horizontal levitation controller and rotation controller. The levitation control is realized by introducing feedback of integral current and deviation of air gap in the proportional-derivative control system. The rotation controller employs a centroid observer and centroid Jacobian. It outputs the rotating angle at the demand of the zero-power and horizontal levitation. Experimental results demonstrate that the proposed maglev system has a better zero power and horizontal levitation performance than without rotary magnets. The direction of the air gap variation is opposite to that of the loading direction. The variation size of air gap length depends on the load weight, whereas rotation angle is related to the load weight and loading position.

Zero-Power and Anti-Tilt Control of a 3-DOF Magnetic Levitation System with rotatable HEM

Zero-Power and Anti-Tilt Control of a 3-DOF Magnetic Levitation System with rotatable HEM

Active system with zero-compliance and zero-power characteristics

This paper focuses on compatibility of zero-compliance and zero-power characteristics in a single system. To realize such compatibility, a horizontal zero-compliance system is developed, in which a zero-power controlled voice coil motor is connected with a normal spring (positive stiffness) in series. Since the zero-power control results zero-current in the steady states, permanent magnets are attached with the developed system to provide bias forces in the steady state. The compatibility of zero-compliance and zero-power with integral control is investigated as well. Because an integral controlled system consumes power even in the steady state, low positive stiffness and deformations in the positive and negative isolators are kept equal in the developed system to reduce such power consumption. The developed zero-compliance system with zero-power and integral controls individually is studied theoretically as well.

Development of 3-DOF active controlled magnetic suspension system with common magnetic pole.

A compact active three-degree-of-freedom magnetic suspension system is fabricated which has a new configuration of magnetic poles. The fabricated magnetic suspension system has a differential structure consisting of an upper and a lower electromagnets. The electromagnet consists of four poles with coils and a single common pole whose opposite plane of the floator has a permanent magnet to achieve zero power control. Modal control is applied because local zero power control may make the whole system unstable when the number of control channel are larger than the number of freedom of motion to be controlled. The system parameters of each mode are identified experimentally to design the modal control system. The characteristics of the fabricated magnetic suspension system are studied experimentally.

Development of a Compact Axial Active Magnetic Bearing with a Function of Two-Tilt-Motion Control

A compact axial active magnetic bearing with a function of two-tilt-motion control is fabricated which has a new configuration of magnetic poles. They consist of four cylindrical poles with coils and a single common pole whose opposite plane of the rotor has a permanent magnet to achieve multi-degree-of-freedom zero power control. Modal control is applied because local zero power control may make the whole system unstable when the number of control channels is larger than the number of freedoms of motion to be controlled. In the developed system, a disk-shape rotor is sandwiched between two axial magnetic bearing stators that are operated differentially. Such a configuration makes it possible to rotate the rotor without disturbing the axial motion. The characteristics of the fabricated magnetic bearing system including rotation are studied experimentally.

Realization of Zero-power Control in a Two-degree-of-freedom Parallel Magnetic Suspension System

Realization of Zero-power Control in a Two-degree-of-freedom Parallel Magnetic Suspension System

Zero Power Control Based on External Force Feedback for Helical Motor

Zero Power Control Based on External Force Feedback for Helical Motor

Zero-power control of double parallel magnetic suspension system with parallel connected coils

Parallel magnetic suspension has been proposed where multiple floators are controlled with a single power amplifier. The feasibility of voltage-controlled double parallel magnetic suspension with parallel connected coils has been already demonstrated in the previous work. This study focuses on the zero-power control in a voltage-controlled double parallel suspension system with parallel connected coils. In this system, there are three methods of achieving zero-power control: feeding back the control voltage, either or the sum of the coil currents. This paper shows the conditions for the system with each zero-power controller to be controllable, and compares their performances.

B02 電磁石が並列接続された並列二重磁気浮上システムのゼロパワー制御(M-OS1-1:高機能な制御を用いたシステム,M-OS1 磁気浮上・磁気軸受の制御,「海を越え,国を越え,世代を超えて!」)

Parallel magnetic suspension has been proposed where multiple floators are controlled with a single power amplifier. The feasibility of voltage-controlled double parallel magnetic suspension with parallel connected coils has been already demonstrated in the previous work. This study focuses on the zero-power control in a voltage-controlled double parallel suspension system with parallel connected coils. In this system, there are three methods of achieving zero-power control: feeding back the control voltage, either or the sum of the coil currents. This paper shows the conditions for the system with each zero-power controller to be controllable, and compares their performances.

Design, Fabrication, and Operating Test of the Prototype HTS Electromagnet for EMS-Based Maglev

The prototype high-Tc superconducting electromagnet (HTS-EM) for high-speed EMS Maglev was successfully demonstrated in EMS system up to the vehicle running speed of 500 km/h. The EM was designed to interface with the existing propulsion system used in the German high-speed Maglev. The rating levitation force of the EM was designed to correspond to the weight of the EM at a 20 mm levitation gap. Electromagnetic forces were simulated and compared with the test results in order to verify the design feasibility of the HTS-EM. Operating tests revealed that the HTS-EM was fully operational in zero-power control mode. However, the operating current of the HTS coil was affected by the control current when the guideway disturbance occurred. The design feasibility and operability of the HTS-EM was verified in the study.

836 多重式磁気浮上システムの開発 : 第12報:電圧制御形並列磁気浮上におけるゼロパワー制御

This paper discusses the feasibility of zero-power control in voltage-controlled parallel magnetic suspension systems. Parallel magnetic suspension systems are classified into two types based on the connection of the multiple coils: series connection and parallel connection. To achieve zero-power control, the integral of current is fed back in the former type whereas the integral of voltage is fed back in the latter. It is proved that each parallel magnetic suspension system incorporating the zero-power controller can assign the poles arbitrarily when the original system is controllable. It is also shown analytically that the current converges to zero in the steady state even when stepwise disturbances act on the floators in both designed systems.

A General Approach for DP Weathervane Control: Experimental Results

With oil exploration occurring at increasing distances from the shore, the use of DP vessels becomes economically attractive for oil transfer and transportation. This operation has some peculiarities, such as the possibility to change the DP vessel heading in order to reduce DP thrust utilization. However, calculation of the optimum heading is not simple, due to uncertainties at wave and current estimation. Moreover, these factors are not constant along time, and the system must adapt with the changes to keep the optimum position.This paper presents and test a new method to define the heading set-point based on the theory of Zero Power Control. This method has important advantages over traditional weathervane control method, such as an effective control of all horizontal movements and the possibility to define any reference-point, not only points located at the vessel bow.

Development of High Speed Flywheel Rotated in a Vacuum Chamber

For the development of high speed flywheel rotation in a vacuum chamber, technology for establishing ultra low loss magnetic bearings and measures for preventing spillover vibration are necessary. For these purposes, tests on two rigs, one involving active magnetic bearings (AMBs) and the other, a medium-size flywheel, were conducted in the present study. With the former, a technique for reducing AMB loss was investigated. In the latter, many trials were carried out in an attempt to find a means for preventing spillover vibration. Based on the results, two important findings were made.First, AMB loss could be reduced to 1/6 of that in conventional control through the use of zero-power control and homo-polar magnetic poles. Secondly, flywheel rotation as high as 12,000 rpm was possible with no significant vibration through phase lead adjustment and the use of a stabilizing filter. Both these possibilities may be attributed to the very precise measurement of natural frequency and the damping ratio.

A modified zero-power control and its application to vibration isolation system

In this paper we present an improved zero-power controlled magnetic suspension system that has the capability to adjust stiffness. The conventional zero-power control system produces constant negative stiffness, and the stiffness solely depends on the capacity of the permanent magnets or the gap–force coefficient of the magnets. This becomes an obstacle to the fields of application of zero-power control where the adjustment of stiffness is necessary, such as developing a vibration isolation system. In this research, the basic zero-power control system is modified such that it can adjust stiffness by adding a minor proportional feedback of displacement to the zero-power controller. Finally, a vibration isolation system is developed by combining a positive stiffness spring in series with a negative stiffness suspension realized by the modified zero-power controller. The proposed control system and the developed vibration isolation system are investigated both analytically and experimentally.

A three-axis vibration isolation system using modified zero-power controller with parallel mechanism technique

This paper proposes a module-type three-degree-of-freedom vibration isolation system using modified zero-power control. Three vibration isolation modules are connected together using parallel mechanism to control 3-DOF motions. Each module consists of a common base, an individual middle mass and a common isolation table. The base to the middle mass is suspended by positive springs generated by active and passive system, and the middle mass and the isolation table is connected by negative spring realized by active-type modified zero-power control. The developed system could realize zero-compliance to direct disturbances as well as good ground vibration isolation. Furthermore, the isolation table is supported by a weight support mechanism for supporting heavy payloads. In the previous research, a concentrated middle mass with redundant actuators, in the vertical and horizontal directions, were used. Therefore, a vibration isolation system is proposed in this work using modular concept to overcome those drawbacks. Each module is controlled separately by decentralized control technique, and three modules can be used for three-degree-of-freedom of motion control. Therefore, no redundancy of actuator is occurred. Moreover, an improved zero-power controller is presented that can adjust negative stiffness instead of conventional zero-power controller. The results obtained from analytical and experimental studies show that the modular technique is reliable and efficient approach to vibration control, and represents a suitable alternative to the conventional active vibration isolation systems.

Zero-Power Control of Parallel Magnetic Suspension Systems

This paper discusses the feasibility of zero-power control in parallel magnetic suspension systems. In parallel magnetic suspension systems, multiple floators are suspend with a single power amplifier. The zero-power control has been used in magnetic suspension systems with permanent magnets providing bias flux. This control realizes the steady states where the attractive force produced by the permanent magnets balances the weight of the suspended object and the electromagnet coil current converges to zero. This paper shows that parallel magnetic suspension systems incorporating zero-power control can assign the poles arbitrary if the original parallel suspension systems are controllable. The feasibility of the zero-power control in a parallel magnetic suspension is demonstrated experimentally.

Two-Axis Magnetic Suspension System with Dual Variable Flux-Path Units

A flux-path control magnetic suspension system with multiple magnetic sources is realized. The principle of the flux-path control magnetic suspension system is to control flux from a permanent magnet to the floator, and the attractive force acting on the floator by the motion control of control plates inserted between the permanent magnet and the floator. Stable suspension and 3-DOF control with a single magnetic source was achieved. However, the horizontal control force was much less than the vertical control force. Multiple magnetic source system can overcome such problem. A variable flux-path unit is developed for the realization of multiple magnetic source system. An experimental apparatus with two variable flux-path units is constructed. Stable levitation is achieved by applying PD and PID controls. In addition, stable levitation with zero-power control is also achieved.

Motion Tests on a Levitated Body Using a Magnetic Levitation System for Three-Dimensional Motion with Partial Zero Power Control

This paper proposes a partial zero-power controller to move a levitated body under energy-saving conditions using a magnetic levitation device that allows three-dimensional motion. Modeling was specifically performed to control the feedback of each independent x-, y-, and z-direction in a controlled system. The z-direction was controlled by using voltage integration with zero power while the x- and y- directions were manipulated with positioning control. After doing experiments on horizontal displacement on the three points on the x-z plane, we verified that the levitated body smoothly shifted to its required value for the x- and y- directions and it moved with zero-power input voltage toward the z-direction.

Application of Feedforward Control to A Vibration Isolation System Using Negative Stiffness Suspension

This paper presents a vibration isolation system using negative stiffness suspension. The vibration isolation system is developed by combining a positive stiffness suspension in series with a negative stiffness suspension. The developed system could realize zero-compliance to direct disturbance, as well as ground vibration isolation. In the previous system, the ground vibration and, the static and low frequency sinusoidal direct disturbances were efficiently suppressed. However, there was a reverse action in case of impulse or step wise disturbance. Therefore, a peak was appeared which was, sometimes, larger than the displacement caused by the step load. This unpleasant response might hamper the objective function of many advanced systems. In this research, a feedforward controller is added in combination with zero-power control to overcome this problem. Some experimental results are presented to verify the proposed control system in a vibration isolation apparatus.

Development of an Active Vibration Isolation System Using Linearized Zero-Power Control With Weight Support Springs

This paper presents a hybrid vibration isolation system using linearized zero-power control with weight support springs. The isolation system, fundamentally, is developed by linking a mechanical spring in series with a negative stiffness spring realized by zero-power control in order to insulate ground vibration as well as to reject the effect of on-board-generated direct disturbances. In the original system, the table is suspended from the middle table solely by the attractive force produced by the magnets and therefore, the maximum supporting force on the table is limited by the capacity of the permanent magnets used for zero-power control. To meet the growing demand to support heavy payload on the table, the physical model is extended by introducing an additional mechanism-weight support springs, in parallel with the above system. However, the nonlinearity of the zero-power control instigates a nonlinear vibration isolation system, which leads to a deviation from zero compliance to direct disturbance. Therefore, a nonlinear compensator for the zero-power control is employed furthermore to the system to meet the ever-increasing precise disturbance rejection requirements in the hi-technology systems. The fundamental characteristics of the system are explained analytically and the improved control performances are demonstrated experimentally.