AC Actuation Research Articles

Micro-Nanometer Positioning Control of Bimodal Ultrasonic Motor Based on Wavelet Differential Actuation Pattern

This paper has developed the bimodal USM a novel actuation pattern, which can actuate the bimodal USM in nanometer magnitude with single actuation pattern instead of combination control of AC actuation pattern, pulse actuation pattern and DC actuation pattern. The novel actuation pattern utilizes a single chip micro-computer to produce a kind of wavelet actuation unit which contains several sine voltage waves with different amplitudes, each wavelet actuation unit is exerted on bimodal USM according to the instruction, by which the step control is obtained. Across the two electrodes of bimodal USM, the differential wavelet actuation voltages are applied to reduce the moving distance of each actuation step, thus the nanometer magnitude actuation sensitivity is achieved. The grating is used as position sensor and the subdivision formulae of mutual compensation functions are adopted to promote the real-time response. The experiment indicated that, with the novel wavelet differential actuation pattern, the actuation characteristic of bimodal USM was improved, the micro-nanometer positioning control was easy to be implemented and the important positioning control parameters under every different actuation conditions could be obtained through the study in the process of actuation.

Resonant Pull-In Condition in Parallel-Plate Electrostatic Actuators

Electrostatic parallel-plate actuators are a common way of actuating microelectromechanical systems, both statically and dynamically. In the static case, the stable actuation voltages are limited by the static pull-in condition, which indicates that the travel range is approximately limited to 1/3 of the initial actuation gap. Under dynamic actuation conditions, however, the stable voltages are reduced, whereas the travel range can be much extended. This is the case with the dynamic pull-in and the resonant pull-in conditions (RPCs). Using energy analysis, this paper extends the study of pull-in instability to the resonant case and derives the analytical RPC. This condition predicts snapping or pull-in of the structure for a given domain of dc and ac actuation voltages versus quality factor, taking into account the nonlinearities due to large amplitudes of oscillation. Experimental results are presented to validate the analytically derived RPC.

Electromagnetic fuzzy logic scheme for the characterization of ac actuators

This paper presents a novel electromagnetic fuzzy logic (EMFL) scheme to predict the performance characteristics of ac actuators. The uniqueness of this technique is in the ability of the fuzzy scheme to change its properties in order to accurately characterize the performance of ac actuators for a range of design parameters. This approach is applied to a prototype ac actuator under motion to static conditions.

A single-layer PDMS-on-silicon hybrid microactuator with multi-axis out-of-plane motion capabilities-part II: fabrication and characterization

This paper reports on fabrication and characterization of a new electrostatic microactuator that achieves out-of-plane multi-axis motion with a single silicon device layer. The multi-axis motion with the simple actuator design is possible by incorporating a three-dimensional (3-D) polydimethylsiloxane (PDMS) microstructure. This paper develops a new device processing method named "Soft-Lithographic Lift-Off and Grafting (SLLOG)" to fabricate the previously designed PDMS-on-silicon hybrid actuator structure. SLLOG is a low-temperature (less than 150/spl deg/C) process that allows replica molded PDMS microstructures to be integrated in silicon micromachined device patterns. The fabricated actuator is characterized using laser vibrometry. The experimental results demonstrate actuation motions achieved in three independent axes with fast dynamic response reaching a bandwidth of about 5 kHz. The fabricated PDMS-on-silicon actuator yields a vertical displacement up to 5 /spl mu/m and rotational motions with a 0.6-/spl deg/ tilting angle at a 40-V peak-to-peak ac actuation voltage.

Ni-Mn-Ga AC engineering properties

Magnetic-field-induced strains in Ni-Mn-Ga alloys have shown promise since their recent discovery. Large, free strains and moderate AC strains that provide mechanical work have already been demonstrated by this author and others. If the development of this ferromagnetic shape memory alloy (FSMA) is to continue towards application, its preparation and processing need to routinized so that its properties are as consistent as possible. Here, a first look into the AC stiffness, susceptibility, magneto-mechanical coefficient and coupling coefficient properties will be shown and their dependencies interpreted. Close to the austenite start temperature, results shown here may indicate better AC actuation performance 10-20°C below the martensite transformation temperature due to lattice softening. Through these results, an engineer will start to understand some of the technical issues necessary for designing FSMAs into applications.

Ac field-induced actuation of single crystal Ni–Mn–Ga

Single crystals of Ni–Mn–Ga have shown 6% field induced strain in quasistatic actuation against an applied load. Here we report the ac actuation response and a magnetostrictivity constant of an off-stoichiometry single crystal of Ni–Mn–Ga measuring approximately 14×5.6×1 mm. This sample shows a maximum 3% strain under a bias stress of 1.1–1.5 MPa. The deficit between the low-frequency ac field-induced strain and the 6% dc results are discussed. Additionally, the ε–H indicate a peak differential value for d13 of 1%/kOe (13×10−8 m/A) which is about two times that of Terfenol-D.

A 3D design optimisation of electromagnetic low-voltage linear actuators based on FE force computation

Experience and exploring the linear AC and DC actuators confirm the necessity of the computation of forces distribution as the step preceding their optimal design. This paper expresses an approach to computations of different forces of low‐voltage linear actuators acting on both mechanical and/or electrical parts. The computations are based on magnetic coenergy concept associated with virtual work method and simulated by step displacement of the armature from the total open through total closed position. The magnetic coenergy is numerically computed through the flux‐linkage approach, where the magnetic field distribution is obtained by applying the finite element method in 3D‐domain.

Commande numérique simplifiée et robuste d'actionneurs asynchrones de faible puissance

High performance motion control with AC actuators needs complex control strategies. The control strategies lead frequently to algorithms requiring powerfull microprocessors for their digital implementation. In a previous paper published in the ''Journal de Physique III'', we evolved an approach of the control of small power permanent magnets synchronous actuators which allows to design and to implement control algorithms requiring only a reduced computation power, while maintaining satisfactory static and dynamic performance and a good insensitivity to perturbations and parameter uncertainties. In this paper, we extend this approach to the control of small power induction actuators.

Diagnostic testing of valves fitted with electric actuators / Diagnoseprüfungen an Armaturen mit Stellantrieben

A mobile diagnosis system for valves fitted with AC actuators was developed. This system records electrical and mechanical data during valve actuation. Evaluation of this data makes it possible to assess reliably the functional status of the valve/actuator unit and to establish incipient or existing deficiencies. Appropriate maintenance measures can then be initiated