Showing papers on "Actuator published in 2001"

Full thickness resection device control handle

Abstract: A control mechanism for a resectioning device, comprises a first actuator coupled to a flexible drive shaft for actuating a first mechanism when operated in a first direction and for actuating, when operated in a second direction, a second mechanism and a first lockout mechanism coupled to the first actuator for preventing actuation of the first actuator in the second direction before a predetermined amount of actuation in the first direction has been completed. Furthermore, mechanisms are provided to control the release during operation in a second direction of torsional energy stored in a flexible drive shaft during operation in a first direction.

DLR-Hand II: next generation of a dextrous robot hand

Abstract: This paper outlines the 2nd generation of multisensory hand design at DLR, based on the results of the DLR Hand I we analysed. An open skeleton structure for better maintenance with semi-shell housing and the new automatically reconfigurable palm have been equipped with more powerful actuators to reach 30 N on the fingertip. The newly designed sensors as the 6-DOF fingertip force torque sensor, the integrated electronics and the new communication architecture with a reduction of cabling to the hand to only 12 lines, are outlined. The Cartesian impedance control of all the fingers completes the new 13-DOF hand.

Adaptive state feedback and tracking control of systems with actuator failures

Abstract: Direct adaptive-state feedback control schemes are developed for linear time-invariant plants with actuator failures with characterizations that some of the plant inputs are stuck at some fixed or varying values which cannot be influenced by control action. Conditions and controller structures for achieving plant-model state matching in the presence of actuator failures are derived. Adaptive laws are designed for updating the controller parameters when both the plant parameters and actuator-failure parameters are unknown. Closed-loop stability and asymptotic-state tracking are ensured. Simulation results show that desired system performance is achieved with the developed adaptive actuator failure compensation control designs.

Piezoelectric Actuation: State of the Art

Abstract: Significant advances in smart material actuators have taken place in the past decade. The holy grail of actuator research is an architecture that can generate high displacement and force throughout a broad frequency range while not consuming a significant amount of electrical power. The large appeal of using smart material actuators stems from their high mechanical energy density. However, all smart material actuators generally have at least one shortcoming involving either mechanical stroke, force, or frequency capability. Whenever speed is a consideration, piezoelectric actuation is the most commonly employed. The purpose of this paper is to review the most current trends in piezoelectric actuation architectures. The paper does not present the theoretical details of each actuator, but instead strives to highlight the novel concepts used in each design to overcome the stroke limitation of the material.

Electronic apparatus vibration generator, vibratory informing method and method for controlling information

Abstract: An electronic device drives an oscillatory actuator to cause generation of vibration when it is detected that an operation input to a touch panel or operation key has been received. The electronic device causes, by this vibration, the touch panel and operation key to vibrate in a direction perpendicular to their respective front surfaces. Alternatively, the housing of the electronic device is made to vibrate. Further, the oscillatory actuator has a weight, a support member for supporting the weight to allow it to reciprocate, and connected to the touch panel or housing or other vibratory member of the electronic device, or vibratory member of the base member of the oscillatory actuator in contact with the vibratory member, and a mechanism for imparting a magnetic force or electrostatic force to cause reciprocal movement of the weight.

A methodology and model for the pull-in parameters of electrostatic actuators

Abstract: This paper presents a generalized model for the pull-in phenomenon in electrostatic actuators with a single input, either charge or voltage. The pull-in phenomenon of a general electrostatic actuator with a single input is represented by an algebraic equation referred to as the pull-in equation. This equation directly yields the pull-in parameters, namely, the pull-in voltage or pull-in charge and the pull-in displacement. The model presented here permits the analysis of a wide range of cases, including nonlinear mechanical effects as well as various nonlinear, nonideal, and parasitic electrical effects. In some of the cases, an analytic solution is derived, which provides physical insight into how the pull-in parameters depend upon the design and properties of the actuator. The pull-in equation can also yield rapid numerical solutions, allowing interactive and optimal design. The model is then utilized to analyze analytically the case of a Duffing spring, previously analyzed numerically by Hung and Senturia, and captures the variations of the pull-in parameters in the continuum between a perfectly linear spring and a cubic spring. Several other case studies are described and analyzed using the pull-in equation, including parallel-plate and tilted-plate (torsion) actuators taking into account the fringing field capacitance, feedback and parasitic capacitance, trapped charges, an external force, and large displacements.

Directional tactile feedback for haptic feedback interface devices

Abstract: Directional haptic feedback provided in a haptic feedback interface device. An interface device includes at least two actuator assemblies, which each include a moving inertial mass. A single control signal provided to the actuator assemblies at different magnitudes provides directional inertial sensations felt by the user. A greater magnitude waveform can be applied to one actuator to provide a sensation having a direction approximately corresponding to a position of that actuator in the housing. In another embodiment, the actuator assemblies each include a rotary inertial mass and the control signals have different duty cycles to provide directional sensations. For power-consumption efficiency, the control signals can be interlaced or pulsed at a different frequency and duty cycle to reduce average power requirements.

Modeling of shape memory alloy actuator and tracking control system with the model

Abstract: There has been great demand for shape memory alloy (SMA) actuators within the field of micro-machines. However, the thermomechanical behavior of SMA actuators is too complicated to accurately predict their response. Moreover the tracking control accuracy of SMA actuators is limited due to the inherent hysteresis nonlinearity. The paper presents a model of an SMA actuator for use in mechanical design and a control system for compensating the hysteresis. First, the model based on constitutive laws developed by Brinson et al. (1996) and our proposed hysteresis model is demonstrated. Next, we propose a control system composed of a proportional integral derivative (PID) feedback loop and a feedforward loop. In the feedforward loop, the desired control input corresponding to the desired displacement is obtained from a static SMA model derived by modifying the classic Preisach hysteresis model. We also propose a method for identifying parameters of the hysteresis model. This methods demands only measurement of the major loop. Application of the control system to our developed SMA actuator shows that the tracking control performance is improved.

Disk drive actuator arm with microactuated read/write head positioning

Abstract: The present invention is embodied in an actuator arm which is mounted to a primary actuator. The primary actuator positions the actuator arm, with a read/write head mounted to the actuator arm, across a data storage disk. The actuator arm comprises an inboard portion, an outboard portion and a pair of bimorph actuators. The inboard portion has a longitudinal axis and is attached to the primary actuator. The outboard portion has the read/write head mounted onto it. The pair of bimorph actuators are deflectable together in a common direction and are connected between the inboard and the outboard portions. Upon deflection of the bimorph actuators in the same direction, the outboard portion is translated along an at least nearly straight line transverse to the longitudinal axis of the inboard portion. This transverse motion allows the read/write head to be kept substantially within a plane parallel to the surface of the data storage disk, preventing damage caused by possible contact between slider and the disk surface from rolling the slider due to out-of-plane motions. Further, the use of bimorph actuators provide increased displacements of the read/write head. Also, since the head displacement is not a function of microactuator's position along the actuator arm, the actuator arm can be shorter, allowing for use in compact disk drives.

Micro magnetic silicone elastomer membrane actuator

Abstract: We present results of the design, fabrication, and testing of a microfabricated, membrane-type magnetic actuator. Magnetic pieces made of electroplated Permalloy (Ni80Fe20) are embedded in a thin flexible membrane made of silicone elastomer. When an external magnetic field is applied, a torque generated on the magnetic pieces produces membrane displacement. Permalloy pieces that are 100-mm-wide, 870mm-long, and 22-mm-thick are strategically positioned in a 2-mm-square, 40-mm-thick polydimethylsiloxane (PDMS) membrane (Sylgard 184). This design, produced through numerical simulations, is optimized to realize large membrane displacements. Tests performed on this membrane actuator showed displacements >80 mm in the presence of a 2:85 10 5 A/m external magnetic field. Larger displacements are possible with greater magnetization fields. This type of membrane actuator can be applied to the fabrication of tetherless micropumps for use in microfluidic systems. # 2001 Elsevier Science B.V. All rights reserved.

Applications of dielectric elastomer actuators

Abstract: Dielectric elastomer actuators, based on the field-induced deformation of elastomeric polymers with compliant electrodes, can produce a large strain response, combined with a fast response time and high electromechanical efficiency. This unique performance, combined with other factors such as low cost, suggests many potential applications, a wide range of which are under investigation. Applications that effectively exploit the properties of dielectric elastomers include artificial muscle actuators for robots; low-cost, lightweight linear actuators; solid- state optical devices; diaphragm actuators for pumps and smart skins; acoustic actuators; and rotary motors. Issues that may ultimately determine the success or failure of the actuation technology for specific applications include the durability of the actuator, the performance of the actuator under load, operating voltage and power requirements, and electronic driving circuitry, to name a few.

Inverse feedforward controller for complex hysteretic nonlinearities in smart-material systems

Abstract: Undesired complex hysteretic nonlinearities are present to a varying degree in virtually all smart-material-based sensors and actuators provided they are driven with sufficiently high amplitudes. In motion and active vibration control applications, for example, these nonlinearities can excite unwanted dynamics, which leads in the best case to reduced system performance and in the worst case to unstable system operation. This necessitates the development of purely phenomenological models that characterize these nonlinearities in a way that is sufficiently accurate, amenable to a compensator design for actuator linearization, and efficient enough for use in real-time applications. To fulfil these demanding requirements, this article describes a new compensator design method for invertible complex hysteretic nonlinearities that is based on the so-called Prandtl-Ishlinskii hysteresis operator. The parameter identification of this model can be formulated as a quadratic optimization problem, which produces the best L 2 2 -norm approximation for the measured output-input data of the real hysteretic nonlinearity. Special linear inequality constraints for the parameters guarantee the unique solvability of the identification problem and the invertability of the identified model. This leads to a robustness of the identification procedure against unknown measurement errors, unknown model errors, and unknown model orders. The corresponding compensator can be directly calculated and thus efficiently implemented from the model by analytical transformation laws. Finally, the compensator design method is used to generate an inverse feedforward controller for the linearization of a magnetostrictive actuator. In comparision to the conventionally controlled magnetostrictive actuator, the nonlinearity error of the inverse controlled magnetostrictive actuator is lowered from about 30% to about 3%.

Diagnostic Lamb waves in an integrated piezoelectric sensor/actuator plate: analytical and experimental studies

Abstract: The objective of this study is to model the diagnostic transient waves in an integrated piezoelectric sensor/actuator plate with a view to using it as a first step towards establishing an entire structural health monitoring system and to provide experimental verification of the proposed models. PZT ceramic disks are surface mounted on an aluminum plate acting as both actuators and sensors to generate and collect A0 mode Lamb waves. Mindlin plate theory is adopted to model the propagating waves by taking both transverse shear and rotary inertia effects into account. Actuator and sensor models are both proposed. The interaction between an actuator and the host plate is modeled based on classical lamination theory. The converse piezoelectric effect of the actuator is treated as an equivalent bending moment applied to the host plate. The sensor acts as a capacitor that converts the sensed strain change into a voltage response. An analytical expression for the sensor output voltage in terms of the given input excitation signal is derived, and then experimental work is performed to verify the accuracy of the analytical model. Experimental results show that single-mode Lamb waves in the plate can be successfully generated and collected through the integrated PZT disks. The experiment also shows that the predicted sensor output for both amplitude and phase agrees well with experimentally collected data.

Proprioceptive golf club with analysis, correction and control capabilities

Abstract: A method of analyzing the swing of a sport implement and player over time in three dimensional space involving implanting implement sensors at numerous locations in the implement adapted for measurement of linear motion on three axes and angular motion on said three axes, such as: linear motion inertial sensors; angular motion sensors; axial strain gauges; flexural strain gauges; and torsional strain gauges. Player sensors are set at a number of locations on the player's body, also adapted for measurement of linear motion on three axes and angular motion on said three axes. Data from the sensor suites are communicated via a wireless communications device to a processing unit by: infrared; radio frequency; or the Bluetooth system. Data is processed from the sensor units to derive an output communicated to the player via an interface such as: visual graphics display; text display; sound interface; tactile device; and vibratory device. The output includes an actuator signal communicated to actuator units engaging at least two actuatable portions of the sport implement moveable relative to each other, such as: solenoids; fluid power cylinders; piezoelectric actuators; magnetic actuators; magneto-restrictive actuators; and rheological fluid actuators.

System for wirelessly supplying a large number of actuators of a machine with electrical power

Abstract: A configuration for supplying a large number of actuators with electrical power without using wires includes at least one primary winding that is fed from a medium-frequency oscillator. Each actuator has at least one secondary winding that is suitable for drawing power from a medium-frequency magnetic field.

Microfabricated double-throw relay with multimorph actuator and electrostatic latch mechanism

Abstract: This invention is a new type of relay that incorporates the functional combination of multimorph actuator elements with electrostatic state holding mechanisms in the development of a micromachined switching device. This combination of elements provides the benefits of high-force multimorph actuators with those of zero-power electrostatic capacitive latching in microfabricated relays with high reliability and low power consumption. The operation of the relay invention allows for several stable states for the device: a passive state using no power, an active state driving the multimorph actuator with some power, and a latched state electrostatically holding the switch state requiring essentially no power. Multimorph actuators covered by this invention include piezoelectric, thermal, and buckling multimorph actuation mechanisms. These devices use one or more sets of actuator armatures in cantilever or fixed-beam configurations, and use one or more sets of electrostatic latch electrodes for state holding.

Passivity-based stability and control of hysteresis in smart actuators

Abstract: The past decade has seen an increase in the use of smart materials in actuator design, notably for inclusion in active structures such as noise-reducing paneling or vibration-controlled buildings. Materials such as shape memory alloys (SMAs), piezoceramics, magnetostrictives and others all offer exciting new actuation possibilities. However, all of these materials present an interesting control challenge due to their nonlinear hysteretic behavior in some regimes. We look at the energy properties of the Preisach hysteresis model, widely regarded as the most general hysteresis model available for the representation of classes of hysteretic systems. We consider the ideas of energy storage and minimum energy states of the Preisach model, and derive a passivity property of the model. Passivity is useful in controller design, and experimental results are included showing control of a differential shape memory alloy actuator using a passivity-based rate controller.

Piezoelectric microactuators with substantially fixed axis of rotation and magnified stroke

Abstract: An actuator is coupled between a head and a flexure, the actuator providing submicron positioning of the head while reducing undesirable vibrations of the flexure. The actuator includes a stator and a rotor, with a plurality of deformable elements coupled between the stator and the rotor. In one aspect the rotor, stator and deformable elements are constructed so that the rotor has a substantially fixed axis of rotation relative to the stator, and the actuation of a transducer in the head is magnified. In another aspect the rotor is coupled to the head so that the axis of rotation is substantially aligned with the center of mass of the head and rotor, increasing the frequency at which the actuator can move the head and reducing vibrations in the flexure caused by actuation of the head.

Variable area nozzle for gas turbine engines driven by shape memory alloy actuators

Abstract: A gas turbine engine includes a variable area nozzle having a plurality of flaps. The flaps are actuated by a plurality of actuating mechanisms driven by shape memory alloy (SMA) actuators to vary fan exist nozzle area. The SMA actuator has a deformed shape in its martensitic state and a parent shape in its austenitic state. The SMA actuator is heated to transform from martensitic state to austenitic state generating a force output to actuate the flaps. The variable area nozzle also includes a plurality of return mechanisms deforming the SMA actuator when the SMA actuator is in its martensitic state.

Hydraulic control system for downhole tools

Abstract: A hydraulic control system for downhole tools enables convenient selection and actuation of a well tool assembly from among multiple well tool assemblies installed in a well. Each well tool assembly includes a control module having a selecting device and a fluid metering device. A predetermined range of pressure levels on one of multiple hydraulic lines causes the well tool assembly to be selected for actuation, a differential between pressure on that hydraulic line and pressure on another hydraulic line determines a manner of actuating the selected well tool assembly, and pressure fluctuations on one of the hydraulic lines causes fluid to be transferred from another hydraulic line to an actuator of the well tool assembly.

Portable electronic equipment, electronic equipment, oscillation generator, reporting method by oscillation, and report control method

Abstract: PROBLEM TO BE SOLVED: To enable a user to easily confirm acceptance of an operation input or response of electronic equipment to the operation input without seeing a picture. SOLUTION: A CPU 113 drives an oscillation actuator 115 through a driving signal generation circuit 114 to generate oscillation when detecting acceptance of an operation input to a touch panel 102 or an operation key. The touch panel 102 and the operation key are oscillated in the direction perpendicular to their surfaces by this oscillation. Or the casing of a PDA(Personal Digital Assistant) 10 is oscillated. The oscillation actuator 115 is provided with a weight body, a support member which supports this weight body so that it can be reciprocated in air and is connected to a member to be oscillated of the PDA 10 like the touch panel 102 or the casing of a base member of the oscillation actuator 115 brought into contact with the above member to be oscillated, and a mechanism which gives kinetic power like magnetic power or electrostatic power to reciprocate the weight body.

A critical analysis of electric shunt circuits employed in piezoelectric passive vibration damping

Abstract: Vibration damping of an elastic structure can be obtained by bonding a piezoelectric actuator onto the vibrating structure, and by shunting the actuator to a suitable electric resonant circuit, tuned to the structural eigenmode to be damped. The achievable damping depends on the particular electric circuit used. In this paper three different electric shunt circuits are analyzed and their performances are compared. In particular, the optimal values of the electric components belonging to each shunt circuit and the corresponding exponential time decay rates of the free vibrations relevant to the controlled structural eigenmode are explicitly determined, also taking into account the inherent structural damping. Finally, some experimental results are reported, obtained by using two of the shunt circuits analyzed, which are in good agreement with the theoretical predictions.

Disk drive for storing sector-reconstruction sectors and for storing a sector-reconstruction status in sectors distributed around a disk

Abstract: A disk drive is disclosed comprising a disk, a head, and an actuator for actuating the head radially over the disk. The disk comprises a plurality of tracks, wherein each track comprises a plurality of sectors. The plurality of sectors comprise a plurality of data sectors for storing data and at least one sector-reconstruction (SR) sector for storing redundancy data generated in response to the data stored in at least one of the data sectors. At least two of the plurality of sectors of a track are for storing a SR status indicating a validity of the SR sector stored on the track.

A new method for compensating actuator delay in real-time hybrid experiments

Abstract: We developed an on–line experimental system for conducting hybrid experiments in real time. It combines a computer, which conducts vibration simulation and generates a control signal, and a hydraulic actuator, which conducts a vibration experiment driven by the control signal. This system compensates for actuator delay and thus enables experiments to be carried out in real time. We evaluated the stability of the experiments with respect to the mass of the structure under excitation, and we developed a new method for compensating actuator delay in order to increase the stability condition. In this method, the compensated control signal is generated from the simulation results by using not only displacement but also velocity and acceleration. This method provides a stability criterion (allowable ratio of mass of the structure under excitation to that of a numerical model) about three times larger than that from the current method.

Piezoelectric actuator and pump using same

Abstract: Thin chamber diaphragm-operated fluid handling devices, including thin chamber pumps and thin chamber valves, facilitate device compactness and, in some configurations, self-priming. Diaphragm actuators of the thin chamber devices either comprise or are driven by piezoelectric materials. The thinness of the chamber, in a direction parallel to diaphragm movement, is in some embodiments determined by the size of a perimeter seal member which sits on a floor of a device cavity, and upon which a perimeter (e.g. circumferential or peripheral portion) of the diaphragm actuator sits. The diaphragm actuator is typically retained in a device body between the floor seal member and another seal member between which the perimeter of the actuator is sandwiched. The devices have an input port and an output port.

Ultra precision positioning system for servo motor–piezo actuator using the dual servo loop and digital filter implementation

Abstract: The ultra precision positioning technique has become one of the important parts in the development of precision machines. For positioning systems having a long stroke with ultra precision, a combined system including a global stage (coarse stage) and a micro stage (fine stage) is designed in this paper. A ball screw based servo motor is used as the global stage and a piezo actuator as the micro stage, in which some design parameters are analysed. To improve positional accuracy and remove the noise components of motion, the digital Chebyshev filter has been designed and implemented. The implemented digital filter has been found to improve accuracy by as much as three times. Positional accuracy has been readily achieved within 10 nm over the typical 200 mm stroke, and therefore this technique can be applied to develop high precision semiconductor equipment such as lithography steppers and probers.

Shape memory polymer actuator and catheter

Abstract: An actuator system is provided for acting upon a material in a vessel. The system includes an optical fiber and a shape memory polymer material operatively connected to the optical fiber. The shape memory polymer material is adapted to move from a first shape for moving through said vessel to a second shape where it can act upon said material.