Electromagnetic Force Actuators Research Articles

Comparison of Floating Offshore Wind Turbine Tower Deflection Mitigation Methods Using Nonlinear Optimal-Based Reduced-Stroke Tuned Vibration Absorber

Tower fatigue and strength are crucial operational concerns of floating offshore wind turbines (FOWTs) due to the escalation of the vibration phenomena observed on these structures as compared to land-based ones. FOWT towers are excited by wave and wind polyperiodic disturbances yielding continual transient states of structural vibration that are challenging for vibration mitigation systems. Thus, the paper investigates a novel implementation of nonlinear optimal-based vibration control solutions for the full-scale, tension leg platform (TLP)-based, NREL 5MW wind turbine tower-nacelle model with a 10-ton tuned vibration absorber (TVA), equipped with a magnetorheological (MR) damper, located at the nacelle. The structure is subjected to excessive wave and wind excitations, considering floating platform motions derived from model experiments in a wave tank. The MR damper operates simultaneously with an electromagnetic force actuator (forming a hybrid TVA) or independently (a semiactive TVA). The study includes both actuators’ nonlinearities and dynamics, whereby the former are embedded in the Hamilton-principle-based nonlinear control solutions. The TVA is tuned either to the NREL 5MW tower-nacelle 1st bending mode frequency (TVA-TN) or to the TLP surge frequency (TVA-TLP). The optimal control task was redeveloped concerning the TVA stroke and transient vibration minimisation, including the implementation of the protected structure’s acceleration and relative displacement terms, as well as the nonzero velocity term in the quality index. The regarded model is embedded in a MATLAB/Simulink environment. On the basis of the obtained results, the TVA-TN solution is by far superior to the TVA-TLP one. All the regarded TVA-TN solutions provide a tower deflection safety factor of ca. 2, while reference systems without any vibration reduction solutions or with a passive TVA-TLP are at risk of tower structural failure as well as the hybrid TVA-TLP system. The obtained TVA stroke reductions of 25.7%/22.0% coincide with 3.6%/10.3% maximum tower deflection reductions for the semiactive/hybrid TVA-TN case (respectively) with regard to the previously developed approaches. Moreover, these reductions are obtained due to the sole control algorithm enhancement; thus, no additional resources are necessary, while this attainment is accompanied by a reduction in the required MR damper force. The lowest obtained TVA stroke amplitude of 1.66 m is guaranteed by the newly introduced semiactive control. Its hybrid equivalent ensures 8% lower primary structure deflection amplitude and reduced nacelle acceleration levels thanks to the utilisation of the force actuator of the relatively low power (ca. 6 kW); the trade-off is an increased TVA stroke amplitude of 2.19 m, which, however, is the lowest among all the tested hybrid solutions. The analysed reference passive TVA systems, along with a modified ground-hook hybrid solution, can hardly be implemented in the nacelle (especially along the demanding side–side direction). The latter, being the well-proven hybrid solution for steady-state tower deflection minimisation, yielded unsatisfactory results. The achievements of the study may be used for an effective design of a full-scale vibration reduction system for the TLP-based floating wind turbine structure.

Automatically tuned boring bar system

This paper introduces a boring bar system which includes an automatically tuned internal vibration absorber, called a tuned mass damper (TMD). The TMD head can be attached to boring bars with a wide range of lengths. An electromagnetic impulse force actuator is developed to measure the frequency response function (FRF) of the boring bar with an integrated power screw. A portable servo motor is attached to the power screw for adaptive tuning of the vibration damper's stiffness. The measurement and tuning cycle is automated until the negative real part of the FRF is optimized to maximize the chatter-free depth of cut. The system is experimentally validated on boring bars with a wide range of length to diameter ratios.

A novel compliant mechanism based system to calibrate spring constant of AFM cantilevers

Calibrating spring constant of atomic force microscope (AFM) cantilevers is necessary for the measurement of micro/nano newton forces, which are commonly-used in the characterization of micro/nano functional surfaces and materials, cell manipulation, and many more applications. This paper presents a novel compliant mechanism based system to calibrate the spring constant of AFM cantilevers. The calibration system is mainly composed of a compliant suspension mechanism and an electromagnetic force actuator, where two kinds of compliant structures of “L” shape flexures and “Archimedes” planar flexures are assembled in parallel to achieve compact devices, respectively. The characteristics of the suspension mechanism are investigated by analytical model and finite element analysis (FEA). Furthermore, a prototype of the calibration system is established and experimental tests are carried out to verify the performance. An electromagnetic force actuator is employed to provide calibration force. Meanwhile, a capacitance sensor is utilized to monitor the displacement of the suspension mechanism. The calibration results of AFM cantilevers reveal that the compliant mechanism based calibration system has a good performance and it can calibrate the spring constant of AFM cantilevers accurately and effectively.

Development and type test of ZW-126/D2000-40 vacuum circuit breaker with controlled switching technology

A ZW-126/D2000-40 type single-break vacuum circuit breaker(VCB) with controlled switching technology is designed and produced in this paper. The results of type test based on IEC and GB standards are presented. A 126 kV single-break vacuum interrupter (VI) with 3/4 coil axial magnetic field (AMF) contacts is used in the VCB, which can interrupt short current of 40 kA. The external insulation of the VI is provided by SF6 at 0.1 MPa. In order to match the 126kV single-break VI and controlled switching device, a long-stroke electro-magnetic force actuator (EMFA) with 16kN closing holding force and 3.5 m/s average opening speed is designed. Moreover, a position tracking controlled switching device based on closed-loop control by the technology of fuzzy control algorithm and pules width modulation is applied to the controlled switching device. This device is applied to control the coil current of EMFA and the electromagnetic force, so as to control the EMFA to follow the ideal position curve. The type tests of 126kV VCB are all passed according to the IEC62271-100 and GB1984-2014, including dielectric tests, basic short-circuit tests, short-line fault test, out-of-phase test, etc. The strong capacitive current breaking capacity and mechanical strength of the VCB are proved by the capacitive current switching test of class C2, electrical endurance test of class E2 and mechanical endurance test of class M2. The electromagnetic compatibility (EMC) tests are passed according to the IEC61000-4. The controlled switching test of capacitive current was successful according to IEC62271-302 and GB/T30846-2014, and the controlled switching accuracy is less than ±0.5 ms. The test results showed that the VCB has excellent performance, which has broad application prospects in special occasions at 126 kV voltage level, such as switching capacitor and no-load transformer, etc.

Structure design and experimental investigation of a multi-function stylus profiling system for characterization of engineering surfaces at micro/nano scales

A novel multi-function stylus profiling system has been developed for characterizing surface properties at micro/nanometer scales. The multi-function stylus profiling system provides, within one set-up arrangement, measurements of topography, friction, Young’s modulus and hardness of a surface. The measurement is based on point-by-point scanning so that the four measured functions can be correlated in space and in time. It targets an area that is of growing importance to a wide range of technologies where function-orientated surfaces/coatings are in demand. The essential part of the multi-function stylus profiling system is a special sensing probe, which has an electromagnetic force actuator and three precision capacitive sensors for simultaneous measurements of surface height/deformation and friction force between the probe tip and the surface being scanned. The system provides a controllable loading force in a range of 0.05–20 mN. The topography measurement has a maximum range of 20 µm. The scanning area of 100 µm × 100 µm is closed-loop controlled with an accuracy of 1 nm. Design, analysis, and experimental investigation of the multi-function stylus profiling system are carried out. Evaluations are carried out on certain material surfaces to demonstrate the capability of the system.

Development of a novel 3-DOF suspension mechanism for multi-function stylus profiling systems

This paper proposes a novel 3-DOF suspension mechanism for multi-function stylus profiling systems. Incorporating an electromagnetic force actuator, the 3-DOF suspension mechanism provides a controlled loading force. For reasons of the thermal and mechanical stability, a triangular flexure structure is utilized to support the stylus. The stiffness matrix method is used to establish the analytical stiffness model of the 3-DOF suspension mechanism. Considering the 3-DOF suspension mechanism as a 3-DOF lumped-mass-spring system, the dynamic model is established. Finite element analysis (FEA) is used to validate the established static and dynamic models of the 3-DOF suspension mechanism. A prototype is fabricated and experimental tests are carried out to characterize the mechanism’s performance. The results show that the 3-DOF suspension mechanism provides a controlled force in a range of up to 10 mN and has a working range in excess of 10 μm with a first natural frequency of 342 Hz in Z axis, indicating good capability for multi-function measurements at the micro/nano scale.

Automatic presser‐foot force control for industrial sewing machines

PurposeThe purpose of this paper is to develop and test control methods for real‐time automatic presser‐foot force control in industrial sewing machines. In this work, a closed‐loop controller that controls presser‐foot maximum vertical displacement is presented and compared to existing solutions that adjust force depending on sewing speed. Automatic force control can reduce problems such as stitch irregularity, stitch distortions and material damage, besides making material handling easier.Design/methodology/approachAn electromagnetic force actuator was integrated in an industrial lockstitch machine. A computer‐based control system was designed implementing either speed‐variable force control, closed‐loop control, or emulating a traditional constant‐force system. Maximum presser‐foot displacement values were measured and analysed in relevant sewing situations, and seam quality was assessed.FindingsConstant‐force control does not allow optimal force setting at all speeds. Speed‐variable force control is an improvement, but requires empirical setting of the speed‐force relation, not always assuring optimal operation. Closed‐loop control adapts force to the requirement of each sewing situation more precisely. Sewing quality is good and material handling is eased.Research limitations/implicationsThe actuator has to be optimised regarding response time and maximum force. Some aspects in the behaviour of the control system and actuator have to be further studied.Practical implicationsThe proposed control system enables the automatic setting and adaptation of force to all sewing situations, making material handling easier at low speeds without compromising feeding performance at high speed. The closed‐loop controller may be used as a teach‐in system for speed‐dependent control.Originality/valueThis is the first prototype of a closed‐loop control system for presser‐foot force on a lockstitch sewing machine and the first comparative study of control methods for presser‐foot force control.

1P1-V07 マイクロ多分岐切換バルブチップの開発 : 電磁気力アクチュエータおよび円弧形状ソレノイド内臓モデルの検討(ナノ・マイクロ流体システム)

1P1-V07 マイクロ多分岐切換バルブチップの開発 : 電磁気力アクチュエータおよび円弧形状ソレノイド内臓モデルの検討(ナノ・マイクロ流体システム)

Size Effect on Tensile Strength of Surface-Micromachined Al-3%Ti Thin Films

A new tensile tester using an electromagnetic-force actuator (voice coil) was developed to measure the mechanical characteristics of surface-micromachined thin film materials. The tester has a load cell with maximum capacity of 0.5N and a non-contact position measuring system based on the principle of capacitance micrometry with 0.1nm resolution for displacement measurement. The tester was applied for tensile testing of Al-3%Ti thin films with dimensions of 1000μm long, 50-480μm wide and 1.0 and 1.1 μm thick. The Al-3%Ti is commonly used in RF(radio frequency) microelectromechanical systems(MEMS) switch. The specimen with holes and bridges was designed for easy tensile test. The holes at center of grip end are able to make alignment and gripping easy. The bridges are to remove the side supports easily and extract specimen from wafer without sawing. It was found that the mean tensile strengths of Al-3%Ti are 140-380MPa, depending on the width of specimens and converging to a certain tensile strength as the width decreases.

Study of the fast-closing switch used for fault current limiters in power system

This paper presents a new type of fault current limiter (FCL) based on fast-closing switch, which is composed of a capacitor bank and a reactor in series. The main control component is a fast-closing switch connected in parallel with the capacitors, which is driven by the electromagnetic repulsion force. It can response the order within 1 ms. When fault occurs, the switch closes and the capacitors are bypassed, and the fault current is limited by the reactor. Simulation analysis and experiment show that the electromagnetic repulsion force actuator can meet the demand of fast-closing switch, it is feasible to develop the FCL with low cost and high reliability.

Experimental Implementation of Active Control to Reduce Annoying Floor Vibrations

When excessive levels of floor vibration disturb the occupants or impair the function of a facility, repair measures are often sought. This paper discusses the role of damping and the application of active control in reducing unacceptable floor motion. The practical implementation of active control, using an electromagnetic force actuator in a computer controlled velocity feedback loop, is also described. Finally, experimental results for two temporary installations, an office floor and a chemistry laboratory floor, are presented to illustrate the effectiveness of the active control scheme.

A controlled-force stylus displacement probe

A novel design of displacement profiler with a controllable stylus force is presented. It provides highly controlled conditions for contact measurement of, for example, small step heights or surface roughness. Incorporating an electromagnetic force actuator and force feedback control, the profiler provides electronically selectable contact force in the range of 0.01–10 mN and gives a constant static and dynamic loading. In a typical configuration, it has a range of a few micrometers with a discrimination to better than 1 nm at a bandwidth higher than that of a conventional stylus instrument.

Design of a Hydraulic Actuator for Active Control of Rotating Machinery

A hydraulic actuator was designed and is described herein. This actuator consists of: a pump, which generates the nominal pressure, a hydraulic servovalve, and a thin elastic plate, which transduces the generated pressure variations into forces acting on a mass, which simulates the bearing of a rotor system. An actuator characteristic number is defined to provide a base for an optimum design of force actuators with combined weight, frequency, and force considerations. This characteristic number may also be used to compare hydraulic and electromagnetic force actuators. In tests this actuator generated 182.3 N force at a frequency of 100. Hz. and a displacement amplitude of 5.8×10−5 m.

An Optimized Magnet-Coil Force Actuator and Its Application to Precision Elastic Mechanisms

Sprung translation mechanisms driven by electromagnetic force actuators are often used to produce controllable motions. This paper is concerned with one family of such devices incorporating linear spring mechanisms suitable for short-range, high-precision applications. In these, a permanent magnet is attached to the movable translating stage which is, in turn, surrounded by a solenoid coil attached to a fixed datum. Design considerations are discussed, principally an optimum dimensional design for a uniformly wound circular cylindrical coil. Design models are verified by the construction of a simple device in steel and aluminium which demonstrates an open-loop positional accuracy of better than 0.5 per cent over a displacement range of 100 nm to 50 μm.