Showing papers on "Actuator published in 1993"

Fabrication and operation of polyimide bimorph actuators for a ciliary motion system

Abstract: In order to extract macroscopic mechanical work out of microelectromechanical systems, we have proposed the concept of distributed micromotion systems (DMMS). The key idea of DMMS is to coordinate simple motions of many microactuators in order to perform a task. Design, fabrication, and operation of a type of DMMS, called a ciliary motion system, are presented. A bimorph thermal actuator using two types of polyimides with different thermal expansion coefficients and a metallic microheater in between them was fabricated. The cantilever-shaped actuator curled up from the substrate owing to the residual stress in polyimides which built up during the cooling process after they were cured at 350 degrees C. It flattened and moved downward by flowing current in the heater. The dimensions of the cantilever were 500 mu m in length, 100 mu m in width, and 6 mu m in thickness. The tip of the cantilever moved 150 mu m in the direction vertical to the substrate and 80 mu m in the horizontal direction; these were the maximum displacements obtained with 33 mW dissipated in the heater. The cut-off frequency was 10 Hz. On a 1-cm-square substrate, 512 cantilevers were fabricated to form an array. Two sets of cantilevers were placed opposing to each other. We operated them in coordination to mimic the motion and function of cilia and carried a small piece of a silicon wafer (2.4 mg) at 27-500 mu m/s with 4-mW input power to each actuator. >

Finite Element Modeling of Piezoelectric Sensors and Actuators

Abstract: A finite element formulation for vibration control of a laminated plate with piezoelectric sensors/actuators is presented. Classical laminate theory with the induced strain actuation and Hamilton's principle are used to formulate the equations of motion. The total charge developed on the sensor layer is calculated from the direct piezoelectric equation. The equations of motion and the total charge are discretized with four-node, 12-degreeof-freedom quadrilateral plate bending elements with one electrical degree of freedom. The piezoelectric sensor is distributed, but is also integrated since the output voltage is dependent on the integrated strain rates over the sensor area. Also, the piezoelectric actuator induces the control moments at the ends of the actuator. Therefore, the number, size, and locations of the sensors/actuators are very important in the control system design. By selective assembling of the element matrices for each electrode, responses with various sensor/actuator geometries can be investigated. The static responses of a piezoelectric bimorph beam are calculated. For a laminated plate under the negative velocity feedback control, the direct time responses are calculated by the Newmark-/? method, and the damped frequencies and modal damping ratios are derived by modal state space analysis.

Active Vibration Control of Laminated Composite Plates Using Piezoelectric Devices: A Finite Element Approach

Abstract: A finite element formulation is presented for modeling the behavior of laminated composites with integrated piezoelectric sensors and actuators. This model is valid for both con tinuous and segmented piezoelectric elements that can be either surface bonded or embedded in the laminated plate. The present model takes into account the mass and the stiffness of the piezoelectric patches. The formulation is based on the first-order shear deformation theory, which is applicable for both thin and moderately thick plates. An additional feature of the present model is that it does not introduce the voltage as an additional degree of freedom. The charge/current generated by the sensor and the response of the plate to an actuator voltage can be computed independently. These features are then coupled with a constant-gain negative-velocity/positive-position feedback control algorithm to actively control the transient response of the plate in a closed loop. Numerical results are presented which indicate the increase in...

Remotely activated endoscopic tools such as endoscopic biopsy forceps

Abstract: Remote control actuators for endoscopic tools are provided. Each remote control actuator includes a driver, a coupler which couple the endoscopic tool to the driver, a power source which power the driver, and a controller coupled to the power source and/or the driver for controlling the power applied to the driver. In conjunction with the controller, a user interface is preferably provided for user control of the remote control actuator which actuates the endoscopic tool. In addition, a sensing/feedback mechanism is preferably provided between the driver and the endoscopic tool and is coupled to the controller and/or the power source. The sensing/feedback mechanism senses the amount of tension or compression on the pull wire(s) of the endoscopic tool and provides a related signal to the controller so that the force applied to the endoscopic tool may be regulated. Various types of power sources are disclosed including electric, mechanical, hydraulic, and pneumatic. Various types of drivers are disclosed, including a motor/linear actuator, a hydraulic or pneumatic piston, and a motor with or without reduction gears coupled to a pulley and belt or a sprocket and chain or a rack and pinion. In addition, several couplers, controllers, user interfaces, and sensing/feedback mechanisms are disclosed.

Shape memory alloy film actuated microvalve

Abstract: A sub-miniature valve which provides an actuator of shape memory alloy film coupled so as to move a poppet adjacent to a valve port The shape memory alloy film actuator is thermally cycled through its phase change transition temperature, resulting in either a contraction or elongation of the actuator This causes the poppet to move relative to the port and either increase or decrease fluid flow The shape memory alloy film is biased toward its deformed position when cooled below its transition temperature The valve can be electrically operated with commonly available voltages, including those used for micro-electronics The relatively large forces and displacements achieved using the shape memory alloy film provide less restriction and greater flow than in other similarly sized valves

Moving magnet-type actuator

Abstract: In a moving magnet type actuator, a magnet moving body including at least two permanent magnets of which same poles are confronting each other and an intermediate magnetic substance. The magnet moving body is movably arranged inside at least three coils. The at least three coils are connected so that current flows in different directions with a zone between the permanent magnets as a boundary. Whereby thrust and efficiency of the moving magnet type actuator is improved.

Laparoscopic instrument with bendable shaft and removable actuator

Abstract: A laparoscopic surgical device has a shaft with an operative tip and a manually operable actuator provided at the proximal end of the shaft for actuating the operative tip. The orientation of the actuator with respect to the shaft of the instrument is adjustable prior to the performance of an operation with the operative tip. The modification of the actuator orientation can be effectuated prior to or upon an insertion, into a patient during a laparoscopic operation, of a distal end portion of the device including the operative tip of the shaft.

Exact Solutions for Static Analysis of Intelligent Structures

Abstract: Exact solutions for static analysis of simply supported rectangular plate-type intelligent structures are presented. The intelligent structure proposed here is composed of a laminated substrate of graphite/epox y composite coupled with distributed sensor and actuator layers of a biaxially polarized piezoelectric polymer, polyvinylidene fluoride (PVDF). The study aims at investigating the capability of the actuator and sensor layers to cause and sense the deformations, respectively, of the substrate of the intelligent structure. The results show that the effectiveness of the piezoelectric actuator layer to cause induced strain actuation in the structure significantly increases with the decrease in the length to thickness ratio of the substrate.

Compound stage MEM actuator suspended for multidimensional motion

Abstract: A microelectromechanical compound stage microactuator assembly capable of motion along x, y, and z axes for positioning and scanning integrated electromechanical sensors and actuators is fabricated from submicron suspended single crystal silicon beams. The microactuator incorporates an interconnect system for mechanically supporting a central stage and for providing electrical connections to componants of the microactuator and to devices carried thereby. The microactuator is fabricated using a modified single crystal reactive etching and metallization process which incorporates an isolation process utilizing thermal oxidation of selected regions of the device to provide insulating segments which define conductive paths from external circuitry to the actuator components and to microelectronic devices such as gated field emitters carried by the actuator.

Braided pneumatic actuator control of a multi-jointed manipulator

Abstract: Problems with control and compliance of pneumatic systems have prevented their widespread use in advanced robotics. However, their compactness, power/weight ration and safety are factors that could potentially be exploited in sophisticated dexterous manipulator designs. This paper reports on the design of a dexterous manipulation with three fingers and an opposal thumb powered by 18 new compact braided pneumatic muscle actuators (PMA). These muscles (which are variants on the McKibben Muscle design) have considerable power output potential, combined with controllable motion and inherent compliance to prevent damage to handled objects. When arranged as antagonistic pairs the joints of the gripper can be driven independently. Using experimental data a system model can be developed and control of these muscles can be explored showing that accurate regulated performance is feasible. >

Piezoelectric actuator design for vibration suppression - Placement and sizing

Abstract: The authors consider the problem of simultaneous placement and sizing of distributed piezoelectric actuators to achieve the control objective of damping vibrations in a uniform beam. For several closed-loop performance measures they obtain optimal placement and sizing of the actuators using a simple numerical search algorithm. These measures are applied to a specific example of a simply supported beam with piezoelectric actuators, and their relative effectiveness is discussed. >

Sensor/Actuator Failure Detection in the VISTA F-16 by Multiple Model Adaptive Estimation

Abstract: Multiple model adaptive estimation (MMAE) is applied to the Variable Inflight Stability Test Aircraft (VISTA) F-16 flight control system at a low dynamic pressure flight condition (0.4M at 20000 ft). Single actuator and sensor failures are first, followed by dual actuator and sensor failures. The system is evaluated for complete or "hard" failures, patial or "soft" failures, and combinations of hard and soft actuator and sensor failures. Residual monitoring is discussed for single and dual failure scenarios. Performance is enhanced by the application of a modified Bayesian form of MMAE, scalar residual monitoring to reduce ambiguities, automatic dithering where advantageous, and purposeful commands.

Piezoelectric Actuator Models for Active Sound and Vibration Control of Cylinders

Abstract: Analytical models for piezoelectric actuators, adapted from flat plate concepts, are developed for noise and vibration control applications associated with vibrating circular cylinders. The loadings applied to the cylinder by the piezoelectric actuators for the bending and in-plane force models are approximated by line moment and line force distributions, respectively, acting on the perimeter of the actuator patch area. Coupling between the cylinder and interior acoustic cavity is examined by studying the modal spectra, particularly for the low-order cylinder modes that couple efficiently with the cavity at low frequencies. Within the scope of this study, the in-plane force model produced a more favorable distribution of low-order modes, necessary for efficient interior noise control, than did the bending model.

Fabrication of distributed electrostatic micro actuator (DEMA)

Abstract: A distributed electrostatic micro actuator (DEMA) has been proposed. The actuator has many small driving units which consist of two wave-like insulated electrodes. Both ends of insulated electrodes are connected to each other, and the driving unit has narrow gap for deformation caused by electrostatic forces. The driving units have large area of electrodes and are distributed in series and in parallel. So, a strong electrostatic force can be obtained, and the deformation and the generated force of the actuator would be large. Macro model of the DEMA was fabricated with polyimide films, and the deformation of the actuator was measured. When the applied voltage was 200 V, the deformation ratio was 36%. A micro actuator was fabricated by use of photolithography and electroplating. The displacement of 28 mu m was observed when applied voltage was 160 V. Experimental results of the micro actuator were compared with the results simulated by finite element method (FEM) analysis. >

Evaluation of approaches to active compressor surge stabilization

Abstract: Recent work has shown that compression systems can be actively stabilized against the instability known as surge, thereby realizing a significant gain in system mass flow range. Ideally, this surge stabilization requires only a single sensor and a single actuator connected by a suitable control law. Almost all research to date has been aimed at proof of concept studies of this technique, using various actuators and sensor combinaltons. In contrast, the work reported here can be regarded as a step toward developing active control into a practical technique. In this context, the paper presents the first systematic definition of the influence of sensor and actuator selection on increasing the range of stabilized compressor performance

Method and apparatus for fail-safe control of at least one electro-mechanical or electro-hydraulic component

Abstract: A fault management apparatus and method are described for a system that includes at least one electro-mechanical or electro-hydraulic component, such as a system valve or main discharge pump in a process plant or water transmission line. An actuator is electrically coupled to the component for application of control signals to selectively actuate or de-actuate the component. A standby power supply, in the form of a uninterruptible power supply (UPS) stores sufficient electrical energy to energize the valve and/or the discharge pump to change the states thereof from one operational state to another. The UPS has sufficient electrical capacity to close a system valve to its fail-safe condition. The actuator can be actuated in a number of different ways, including sensing of failure of main power, manual activation or sensing of some emergency condition. Logic circuit, which may be in the form of relay or other logic, and preferably a programmable logic circuit (PLC) is used and programmed to sense the external conditions which require shutdown of the system, in which case the energy stored in the standby power supply is applied to the actuator and the component. The PLC is advantageously programmed to shutdown the system, when necessary, in accordance with a timed sequence, checking or monitoring a system at each step of the sequence as to the continued existence of the condition which required shutdown. Similarly, when the system is automatically returned on line, the PLC is advantageously programmed to check the system along each step of the sequence to insure that all of the conditions are acceptable for return of the system to the on-line condition.

Flextensional "moonie" actuators

Abstract: In recent years, piezoelectric and electrostrictive ceramics have been used in many actuators applications. A new type of composite actuator, which is based on the concept of a flextensional transducer, has been developed. (1-6) This ceramicmetal composite actuator, or "moonie" consists of either a piezoelectric ceramic disk or a multilayer stack sandwich between two specially designed metal end caps. This new design provides a sizeable displacement, as well as a large generative force. In other words, it bridges the gap between the two most common types of actuator; the multilayer and bimorph (7).

Method and apparatus for structural actuation and sensing in a desired direction

Abstract: An apparatus, system and method for actuating or sensing strains in a substrate which includes at least one actuator/sensor element which has transverse and longitudinal axes. The actuator/sensor element is attached to the substrate in such a manner that the stiffness of the actuator/sensor element differs in the transverse and longitudinal axes. In this manner, it is possible to sense or actuate strains in the substrate in a desired direction, regardless of the passive stiffness properties of the substrate, actuator element or sensor element. An isotropic actuator/sensor element attached to a substrate in this manner can then operate in an anisotropic way. In a preferred embodiment, the actuator/sensor element is bonded to the substrate at an area of attachment occupying only the central third of the actuator/sensor element in its longitudinal axes. The actuator/sensor element may be a piezoelectric, magnetostrictive, thermally actuated lamina (including bi-metallic) or shape memory alloy element.

Helicopter active noise control system

Abstract: An active noise control (ANC) system (10) for a helicopter that is operative to effectively nullify one or more high frequency vibrations emanating from the main transmission gearbox thereof at the gearbox/airframe interface, thereby significantly reducing the interior noise levels of the helicopter, that is design optimized to minimize the number of actuators required, and that is design optimized to minimize contamination forces arising from operation of the system actuators. The ANC system includes modified transmission beams (12) that are mechanically stiffened to function as rigid bodies with respect to the one or more of the high frequency vibrations, a plurality of actuators (20) disposed in combination with the modified transmission beams (12), a plurality of sensors (30) disposed in combination with the modified transmission beams (12) in a colinear, spaced apart functional correlation with respective actuators (20), and controllers (40) interconnecting individual actuators (20) with respective functionally correlated sensors (30). Each transmission beam (12) may be mechanically stiffened in its entirety or only at localized segments adjacent each mounting hardpoint (14) thereof. Each sensor (30) is operative to detect a single dimensional component of the one or more high frequency vibrations and to generate a signal representative thereof. Each controller (40) is operative in response to such signal to generate a command signal to control operation of the respective actuator (20). Each actuator (20) is operative in response to command signals to generate dimensional counterforces having a frequency, magnitude, and phase to effectively nullify the respective dimensional component of the one or more high frequency vibrations emanating from the transmission gearbox. Each actuator (20) is further operative in response to such command signals to generate cancelling forces to counteract contaminating forces arising from operation of the actuators (20).

Shape memory alloy actuator

Abstract: A shape memory alloy actuator is disclosed. In one arrangement, a louvered window covering, such as a vertical or horizontal venetian blind, is provided with a thermal actuator to automatically rotate slats forming the louvered window covering between open and closed positions. The actuator includes at least one shape memory alloy spring that, when heated above a predetermined temperature, extends to engage and move a rack that drives a pinion gear. The pinion gear rotates, through a coupling mechanism, a rod extending the length of the blind. A second shape memory alloy spring may be installed to rotate the rod in the opposite direction. The rod intercouples the slats in a manner such that the rotation of the rod rotates the slats in unison between closed and open positions. The shape memory alloy spring may be heated with a current supplied by a controller in response to a predetermined environmental condition. The venetian blind mechanism's manual actuation would not be compromised or interfered with by the thermal actuator of the use of the thermal actuator because the thermal actuator is not physically coupled to the blind except intermittently.

Piezoelectric actuator for optical alignment screws

Abstract: A piezoelectric actuator for rotating a shaft associated with an optical mount positioning system in which the actuator moves in first direction at a slow enough velocity to maintain engagement between the actuator and shaft to drive the shaft in the desired direction, and the actuator moves in a second direction at a sufficiently high acceleration and velocity to cause the actuator to lose engagement with the shaft and slip, thereby achieving motion of the shaft in only the desired direction.

Optimization of noncollocated sensor/actuator location and feedback gain in control systems

Abstract: An analytical model is developed for structural control optimization in which both noncollocated sensor/actuator placement and feedback control gain are considered as independent design variables. Two different control algorithms-active damping control and optimal output feedback control-are applied to derive the control input, and the optimal set of solutions is determined by the modified method of feasible direction. Analytical results show that noncollocated sensor/actuator location can lead to instability of the closed-loop system; however, the optimal sensor/actuator location, together with the optimal feedback control gain, can stabilize the structural control systems. In addition, the performance of both active damping control and LQ control can be maximized.

Spatially distributed SMA actuator film providing unrestricted movement in three dimensional space

Abstract: A flexible VLSI film containing shape memory alloy (SMA) actuator elements and associated control and driver circuitry is wrapped around any bendable element such as a flexible, hollow tube, catheter tube or the like. The SMA actuator elements are thus spatially distributed around the circumference of the bendable element. The SMA actuator elements are selectively resistively heated with an electric current through associated decode and driver circuitry, thereby causing a portion of the film to contract. The radical distribution of the SMA actuator elements across the surface of the VLSI actuator film is such that when properly activated, a device sheathed with the VLSI film is capable of executing highly dexterous maneuvers in three-dimensional space, which was not heretofore possible. The actuator elements are self-guided in that control circuitry, decode circuitry and associated microprocessors, including position mapping means are fabricated in VLSI integrally with the SMA actuator elements. Alternatively, a microprocessor controller may be located at a remote location while communicating with associated driver circuitry on the actuator film.

Improvement on characteristics of linear oscillatory actuator for artificial hearts

Abstract: The authors discuss improvements to develop a simple structured, permanent magnet single-winding linear oscillatory actuator (LOA) for total implantable artificial heart actuators. Two methods for improving the starting thrust of the LOA are considered: one is improvement by structural analysis; another is improvement by the exciting current control. In the first method, the starting thrust could be improved by the authors' investigations into the mover diameter, stator inductor shoe dimension and other factors. In the second, the current waveforms to obtain arbitrarily static thrust characteristics with respect to displacement were calculated. >

Vibration control of a laminated plate with piezoelectric sensor/actuator: finite element formulation and modal analysis

Abstract: The combined effects of passive and active control on the vibration control of a com posite laminated plate with piezoelectric sensors/actuators are investigated. Finite element formula tion and mo...

Adaptive Tracking Control of an Air Powered Robot Actuator

Abstract: An adaptive controller is presented for a one-degree-of-freedom pneumatic actuator. The control law uses full-state feedback for simultaneous parameter identification and tracking control. For position control, a pneumatic actuator with high bandwidth is difficult to obtain because of the compressibility of air and the nonlinear characteristics of air flowing through a variable area orifice. Most previous controllers for gas powered actuators were relatively limited fixed gain or on-off type controllers with low tracking accuracy. Experimental results demonstrate that tracking performance comparable to electric servomotors can be obtained using the algorithm presented despite the nonlinearities and compressibility of air