Showing papers on "Actuator published in 1991"

Piezoelectric Actuators for Distributed Vibration Excitation of Thin Plates

Abstract: The results demonstrate that modes can be selectively excited and that the geometry of the actuator shape markedly affects the distribution of the response among modes. It thus appears possible to tailor the shape of the actuator to either excite or suppress particular modes leading to improved control behavior

Induced strain actuation of isotropic and anisotropic plates

Abstract: The development and experimental verification of the induced strain actuation of plate components of an intelligent structure is presented. Equations relating the actuation strains, created by induced strain actuators, to the strains induced in the actuator/substrate system are derived for isotropic and anisotropic plates. Plate strain energy relations are also developed. Several exact solutions are found for simple actuator/substrate systems, and a general procedure for solving the strain energy equations with a Rayleigh-Ritz procedure is formulated. Approximate Ritz solutions lead to both an understanding of the system design parameters, and to detailed models of cantilever plate systems. Simple test articles were used to verify the accuracy of the basic induced strain actuator/substrate system models, and cantilever plate test articles were built and tested to verify the ability of the models to predict the strains induced in systems with extensive stiffness coupling and complicated boundary conditions.

Development of flexible microactuator and its applications to robotic mechanisms

Abstract: A flexible microactuator (FMA) driven by an electropneumatic (or electrohydraulic) system has been developed. The FMA has three degrees of freedom, pitch, yaw, and stretch, and these are suitable movements for miniature robotic mechanisms such as fingers, arms, or legs. The construction is of fiber-reinforced rubber, and the mechanism is very simple. Gentle miniature robots with no conventional links can be designed using this design. The FMA's basic characteristics and its applications to certain robot mechanisms are presented. Serially connected FMAs act as a miniature robot manipulator. The kinematics and control algorithm for this type of robot are presented. FMAs combined in parallel act as a multifingered robot hand, with each FMA representing a finger. An algorithm for the cooperative control of such FMAs, the stable region for holding, and its performance are presented. >

A dual-stage magnetic disk drive actuator using a piezoelectric device for a high track density

Abstract: A dual-stage actuator has been developed using a piezoelectric device for a magnetic disk drive with a high track density over 15 kTPI. This actuator uses a VCM (voice coil motor) rotary actuator as a coarse actuator and a piezoelectric actuator installed in a head-arm as a fine actuator. The stroke of the fine actuator is 4.6 mu m, which is sufficient for a track pitch of 1.5 mu m at 17 kTPI. The head position is detected by an optical method using a dot-pattern etched on a disk. The authors describe the design of the dual-stage actuator, including structural analysis, its static and dynamic characteristics, the dual-stage feedback control system. Experimental results of tracking with high accuracy on a 3.5-in disk-drive unit are presented. >

Optimal placement of actuators in actively controlled structures using genetic algorithms

Abstract: The actuator location selection problem is cast in the framework of a zero-one optimization problem. A genetic algorithmic approach is developed. To obtain successive generations that yield the solution corresponding to the maximum fitness value, this approach involves three basic operations: reproduction, crossover, and mutation.

Scanning probe microscopy

Abstract: A probe (600) arranged to oppose a sample (500) is coupled to a driving portion (400) constituted by an actuator (250) capable of obtaining a large expansion/contraction amount and an actuator (350) capable of obtaining a small expansion/contraction amount. In order to keep the gap length between the sample (500) and the probe (600) constant, a first gap length control system (200) drives the actuator (250) and a second gap length control system (300) having a driving time constant smaller than that of the first gap length control system (200) drives the actuator (350) in response to changes in gap length between the sample (500) and the probe (600).

Semiconductor transducer or actuator utilizing corrugated supports

Abstract: A semiconductor transducer or actuator is disclosed. The transducer and actuator each include a deflecting member with corrugations producing increased vertical travel which is a linear function of applied force. An accurate and easily controlled method that is insensitive to front-to-back alignment is also disclosed for forming uniform corrugations of precise thickness; independent of the thickness of the deflecting member. The cross-sectional shape of the corrugations is not limited by the etching technique, so that any configuration thereof is enabled.

Seismic‐response‐controlled structure with active mass driver system. Part 1: Design

Abstract: An Active Mass Driver (AMD) system is proposed to suppress actively the response of a building to irregular external excitations such as earthquakes and typhoons. This system has been introduced to an actual ten-storey office building for the first time in the world. The system controls the motions of a structure by means of an external energy supply. It consists of an auxiliary mass installed in a building and an actuator that operates the mass and produces a control force which counters disturbances to the building. The design method of the AMD system, including the location of the installation and the capacity and stability of the system, is proposed. Simplification of the control algorithm is also described.

Piezoelectric modal sensor/actuator pairs for critical active damping vibration control

Abstract: Incorporating the piezoelectric effect into classical laminate plate theory, distributed sensors and actuators capable of sensing and controlling the modal vibration of a one‐dimensional cantilever plate are derived theoretically and verified experimentally. It is shown that critical damping of a particular mode can be achieved using such a modal sensor/actuator combination as long as the vibrational amplitude of the controlled structure does not saturate the modal actuator. Since the sensor signal is proportional to the modal coordinate time derivative, velocity feedback control can be employed without using any element tuned to the resonant frequency in the feedback controller. Therefore, the sensitivity of the closed‐loop performance and stability to resonant frequency variations is minimized. By eliminating electromagnetic interference and ground loop noise, critical damping is experimentally demonstrated for the first mode of a one‐dimensional cantilever plate using PVF2 as the sensor/actuator material.

Blood pump actuator

Abstract: An implantable blood pump actuator uses an efficient direct drive voice coil linear motor to power an hydraulic piston. The motor is immersed in oil and has but one moving part, a magnet which is attached to the piston. The piston is supported using a linear double acting hydrodynamic oil bearing that eliminates all wear and will potentially give an infinitely long life. There are no flexing leads, springs to break or parts to fatigue. A total artificial heart embodiment is very light, small, and as efficient as present prosthesis. The motor uses two commutated coils for high efficiency and has inherently low side forces due to the use of coils on both the inside and outside diameters of the magnet. The motor is cooled by forced convection of oil from the piston motion and by direct immersion of the coils in the oil. The highly effective cooling results in a smaller lighter weight motor.

Longitudinal-effect type laminar piezoelectric/electrostrictive driver, and printing actuator using the driver

Abstract: A laminar longitudinal-effect type piezoelectric or electrostrictive driver which is displaced upon application of an electric field thereto. The driver includes laminar electro-mechanical converting elements each undergoes a displacement in a direction of the electric field due to the longitudinal mode of the reverse piezoelectric effect or the electrostrictive effect, and the temperature compensating elements each of which is interposed between the appropriate adjacent two laminar electro-mechanical converting elements. The temperature compensating elements have a higher coefficient of linear thermal expansion in the direction of the electric field or direction of displacement of the driver. The driver is suitably usable for an actuator for operating a print element of a printer, for example.

Optimal placement of piezoelectric actuators and polyvinylidene fluoride error sensors in active structural acoustic control approaches

Abstract: Optimization of the location of a rectangular piezoelectric actuator and both the size and location of a rectangular surface strain error sensor constructed from polyvinylidene fluoride (PVDF) for active structural acoustic control (ASAC) is studied in this work. An algorithm is proposed for choosing the optimal actuator/sensor configuration for controlling sound from a baffled simply supported plate excited harmonically, and the resulting acoustic response is predicted from analytical models. These results are compared to those measured in the lab on a test rig duplicating the appropriate boundary conditions and situated in an anechoic chamber. Results from a single optimally located control actuator are compared to those from control with a nonoptimally positioned actuator as well as multiple control actuators. In addition, either microphones are used to provide error information in the test cases or a single optimally located and dimensioned PVDF error sensor is implemented as the cost function. Results from this study indicate that optimization of control actuators and error sensors provides a method for realizing adaptive structures for active structural acoustic control (ASAC), rivaling in importance the performance increases gained when acoustic control is achieved with microphone error sensors and multiple control actuators.

Microfabricated actuator with moving permanent magnet

Abstract: A microactuator is presented which uses electromagnetic force generation within micromachined silicon devices. A rare-earth permanent magnet is bonded on a movable micromachined silicon plate suspended by thin silicon beams. A monolithically integrated planar coil is used to generate a magnetic field which forces the magnet to move vertically. Using a magnet with a dimension of 1.5*1.5*1.0 mm/sup 3/ and a 17-turn coil driven with 300 mA, a static elevation of 70 mu m has been achieved. The actuator concept offers a variety of application-specific design possibilities. The use of a moving permanent magnet allows a magnetic coupling of the actuator force to the environment. By integrating a magnetic field sensor and signal processing, an active, controlled microsystem can be realized. High, long-range forces can be generated in order to realize devices with large deflections. >

Giant magnetostrictive alloy (GMA) applications to micro mobile robot as a micro actuator without power supply cables

Abstract: The authors describe an in-pipe micro mobile robot with a new actuator called the giant magnetostrictive alloy (GMA), which requires no power supply cables. The cableless micro mobile robots can be controlled by the magnetic fields supplied by the outer side. The mechanism of the motions is based on an inch-worm-type mobile mechanism. Two mechanisms are discussed here: (1) the reversible motion and (2) the one-way motion mechanisms. The sizes of the robots are 21 mm in diameter for the reversible motion of the macro model and 6 mm in diameter for the one-way motion of the micro model. The motion is controlled by the regulated motion of the outer electromagnetic coil, so that the in-pipe micro mobile can follow the outer coil. These micro cableless mobile robots may be suitable for small pipe inspections and for application in the biomedical field. >

Vibration control of a two-link flexible robot arm

Abstract: Analysis and experimentation are described for a two-link apparatus in which both members are very flexible. Attention is focused on endpoint position control for point-to-point movements, assuming a fixed reference frame for the base, with two rotary joints. Each link in instrumented with acceleration sensing and is driven by a separate motor equipped with velocity and position sensing. The control perspective adopted is to implement a two-stage control in which the vibration control problem for fine motion endpoint positioning is considered separately from the gross motion, large angle skew problem. In the first stage the control law shapes the actuator inputs for the large angle movement in such a way that minimal energy is injected into the flexible modes, while in the second phase an endpoint acceleration feedback scheme is employed in independent joint control for vibration suppression at the link endpoints. >

An integrated approach to controls and diagnostics using the four parameter controller

Abstract: A foundation for an integrated approach to the design of controls and diagnostics in reliable control systems is presented. The control module and diagnostic module of the control system are designed together, instead of independently, thereby accounting for the interactions which occur between these two modules in a functioning control system. The four-parameter controller, a generalization of the two-parameter controller, is used. This controller has two vector inputs and two vector outputs, and, correspondingly, is composed of four matrix parameters. The additional controller output may be viewed as a diagnostic output which is monitored to detect and isolate sensor and actuator faults. A parameterization of all four parameter controllers is developed. The fundamental limitations and inherent tradeoffs governing the design of controls and diagnostics are delineated. Special attention is given to the issues of control/diagnostic interaction and uncertainty. Several means for resolving these design tradeoffs are proposed and illustrated by an example involving a jet engine. >

Methods of conditioning fluid in an electronically-controlled unit injector for starting

Abstract: Herein are disclosed methods of conditioning fluid, such as damping fluid, in an electronically-controlled unit injector in order to facilitate quick starting of an engine. Fluid normally used to dampen the motion of an electrical actuator assembly of the unit injector can remain in the actuator assembly after the engine is stopped. If too much fluid remains and cools off in the actuator assembly, quick starting of a cold engine may be hindered. Each of the above methods expels and/or heats up at least a portion of the remaining fluid in the actuator assembly while the engine is at rest and thereby enables quicker response of the actuator assembly when the engine is started. Such quicker response improves the fuel injection delivery capability and timing accuracy of the unit injector during engine startup.

Test and Theory for Piezoelectric Actuator-Active Vibration Control of Rotating Machinery

Abstract: The application of piezoelectric actuators for active vibration control (AVC) of rotating machinery is examined Theory is derived and the resulting predictions are shown to agree closely with results of tests performed on an air turbine driven-overhung rotor The test results show significant reduction in unbalance, transient and sub-synchronous responses Results from a 30-hour endurance test support the AVD system reliability Various aspects of the electro-mechanical stability of the control system are also discussed and illustrated Finally, application of the AVC system to an actual jet engine is discussed

Robot and robot actuator module therefor

Abstract: An actuator module for inducing the relative motion of robot members joined in a robot joint includes a Ferguson epicyclic gear train, integral motor and integrated control means. The gear train comprises a plurality of base gears connected to the robot members and a plurality of planet gear carriers, each planet gear carrier having a plurality of planet gears rotatably mounted therein. A motor integrated with certain gear train components induces the rotation of the planet gear carriers about or within the base gears. Because of the Ferguson paradox, this induces the motion of base gears connected to one robot member relative to those connected to the other robot member, which in turn causes the relative motion of the robot members. The actuator module can be configured as dual substantially symmetric systems and may comprise multiple stages of epicyclic gearing.

Volumetric pump with spring-biased cracking valves

Abstract: A volumetric pump and method for displacing a predetermined quantity of fluid at a predefined cracking pressure, independent of supply and output pressures. The volumetric pump (30) includes an inlet cracking valve (46), an outlet cracking valve (52), and a plunger (48) for displacing fluid from a pumping portion (34b) of flexible tubing (34) that extends through the volumetric pump (30). The pumping portion (34b) of the flexible tube (34) fills with liquid when the inlet cracking valve (46) is fully opened and is urged to expand by jaws (236) on pivotally-mounted arms (234). The arms are forced to pivot, as tubing reshaper rollers (160), disposed on the plunger (48), roll along the inner surface (232) of each arm. During a pumpback-pressurization segment of the pumping cycle, the inlet cracking valve (46) applies a cracking force to the flexible tubing (34), while the plunger (48) compresses the pumping portion (34b) of the flexible tubing (34) sufficiently to develop a cracking pressure that displaces excess fluid back through the inlet cracking valve (46) toward a container (32). After the excess fluid has been forced from the pumping portion (34b) of the flexible tubing (34), a pumping segment of the cycle begins, wherein the inlet cracking valve (46) closes fully and the outlet cracking valve (52) applies a cracking force to compress the flexible tubing (34). Fluid is then forced by the plunger (48) from the pumping portion (34b) of the flexible tubing (34) into a distal portion (34c). The volumetric pump (30) compensates for variations in elasticity of the flexible tubing (34) that would otherwise cause variations in the cracking pressure, using balance blocks (42 and 58). A volumetric pump (400) for use with a cassette (300) comprises a second embodiment of the volumetric pump, in which inlet and outlet cracking valves are defined in respect to the forces applied by actuators against a flexible membrane (340) in the cassette, while a plunger (326) displaces fluid from a pumping chamber (380) in the cassette. Volumetric pump (400) applies appropriate forces to an inlet valve actuator (319) and an outlet valve actuator (332) to achieve cracking and closure forces, just as in the first embodiment.

Bending and Shape Control of Beams Using SMA Actuators

Abstract: Two new configurations for enhanced bending control of beams with in duced strain actuators are presented. In the first configuration the actuator is external to the beam and passes through selective points on the beam. Since the actuator is outside the beam, differential movement between the actuator and the beam is possible; this results in enhanced bending due to the buckling action of the actuator force. Before actual buckling, there is a fairly large useful range of enhanced bending. In this range the beam displace ments are much greater than can be obtained by embedded or surface bonded actuators. The theoretical formulation for this configuration and its experimental verification is pre sented.

Distributed modal identification and vibration control of continua : theory and applications

Abstract: Conventional transducers and actuators are "discrete" in nature, i.e., they usually measure and control spatially discrete locations. These discrete devices become useless when they are placed at modal nodes or lines. In this paper, a generic "distributed" modal identification and vibration control theory for sensing and control of continua, e.g., shells, plates, cylinders, beams, etc., is proposed. The generic theory is derived for a thin shell coupled with two electroded piezoelectric layers. One piezoelectric layer serves as a distributed sensor and the other a distributed actuator. The sensor output, or a reference signal, is processed, amplified, and fed back into the distributed actuator. Due to the converse effect, the injected high voltage induces in-plane strains which result in counteracting moments used to suppress the shell oscillation. System dynamic equations and state equations are also derived. The theory shows that the distributed sensor can identify all vibration modes and the distributed actuators also control all modes. Simplification of the generic theory to other geometries is also demonstrated.

Head position control system for fixed drive including position encoder, temperature sensor and embedded fine servo information

Abstract: A micro-Winchester disk drive subsystem includes a data block sequencer, cache memory and interface for a host computing machine. The drive includes a base and a plurality of non-removable directly rotated disks forming data storage surfaces. A balanced rotary head transducer actuator is mounted to the base for a plurality of data transducer heads among a multiplicity of concentric data tracks formed on each data storage surface of each of the disks. The track following servo system includes a position encoder coupled between the actuator structure and the base, prerecorded data track centerline information at a radially outermost region and at a radially innermost region of each data surface, and a temperature sensor for sensing temperature of the base at the vicinity of the position encoder. An actuator driver circuit is connected to supply electrical driving current to the actuator structure; and, a single, time divided multi-tasked digital including an analog to digital converter is connected to receive the position information from the position encoder, centerline information from the disk surfaces read by the data transducer and temperature sensed by the temperature sensor during a calibration operation in one phase of its operational cycle, the other phase being devoted to supervision data block handling functions of disk drive data block sequencer cache memory and interface. During track following operations, centerline information is derived from information obtained in the calibrate operation. The temperature sensor is periodically checked and recalibration is carried out when drive temperature changes.

Active Vibration Control of the Axially Moving String in the S Domain

Abstract: A new method is presented for active vibration control of the axially moving string, one of the most common models of axially moving continua. The control is formulated in the Laplace transform domain. The transfer function of a closed-loop system, consisting of the plant, a feedback control law and the dynamics of the sensing and actuation devices, is derived. Analysis of the root loci of the closedloop system gives two stability criteria. Stabilizing controller design is carried out of both collocation and noncollocation of the sensor and actuator. It is found that all the modes of vibration can be stabilized and that in principle the spillover instability can be avoided. Also, the steady-state response of the stabilized string to periodic, external excitation is presented in closed form.

Active vehicle suspension with brushless dynamoelectric actuator

Abstract: A vehicle suspension uses actuators between sprung and unsprung masses, each actuator comprising a brushless dynamoelectric machine having a low inertia rotor engaged with a rotary/linear motion converter or conversion between dynamoelectric machine torque and linear actuator force. A control circuit for each machine applies current from an electric power source to the dynamoelectric machine in response to rotor position sensors and an input control signal to produce a desired actuator force providing motoring or generating action by the dynamoelectric machine. A common supply bus connecting the electric power source and dynamoelectric machines allows the dynamoelectric machines in generating mode to provide electric power to the dynamoelectric machines in motoring mode. Transient storage capacitors across the supply bus, current limiting from the supply bus to the storage battery, a dump resistance and dump switch responsive to battery voltage, and a supplementary alternator are also provided.

Contact perpendicular recording on rigid media

Abstract: The authors describe integrated head/flexure structures which have an effective mass of about 300 mu g, evidence no indication of head crash, and hold the potential for very low wear of both head and media, when operating in continuous sliding contact at media velocities of 15 m/s or greater. A perpendicular probe type transducer was constructed as an integral part of a thin dielectric flexure. Initial recording performance on two-layer perpendicular media indicates promise for achieving very high linear and track densities, and the extremely small mass facilitates the design of servo systems and actuators capable of substantially reducing track access time. >

Operation apparatus for vehicle automatic transmission mechanism

Abstract: An operation apparatus for a vehicle automatic transmission mechanism includes first and second actuators (22A, 22B), connected in parallel with a hydraulic valve (16), for driving the hydraulic valve (16) to switch a travel range of an automatic transmission mechanism (12), a control unit (30) for controlling the first and second actuators (22A, 22B), and a transmission operation unit (10) for outputting a range signal indicating a presently set travel range to the control unit (30). The transmission operation unit (10) includes a stroke contact type operation switch (18) on which travel ranges to be set are sequentially aligned along a predetermined path. The control unit (30) includes a first CPU (30A), connected to the first actuator (22A), for controlling a driving operation of the first actuator, a second CPU (30B), connected to the second actuator (22B), for controlling a driving operation of the second actuator, and a third CPU (30C), connected to the first and second CPUs (30A, 30B), for setting, in a driving state, one of the first and second actuators (22A, 22B) connected to one of the first and second CPUs (30A, 30B), which CPU serves as a main unit, for monitoring system failed states of the first and second CPUs, for, when the third CPU determines that a system failed state occurs, inhibiting the driving operation of the actuator (22A, 22B) connected to the system-failed CPU, and for permitting the driving operation of the actuator (22A, 22B) connected to the CPU which does not suffer from the system failed state.

Rotary inertial latch for disk drive actuator

Abstract: A rotary inertial latch (19) is disclosed for maintaining the actuator (12) of a disk drive (10) in its proper position when the drive is not in operation.

Adaptive Pneumatic Force Actuation and Position Control

Abstract: In this paper an implementation of an adaptive control law for a pneumatic actuator is presented. Pneumatic actuators are of particular interest for robotic applications because of their large force output per unit weight, and their low cost. Stabilization of a pneumatic actuator is difficult if a high bandwidth closed-loop system is desired. This is because of the compressibility of air, and of the nonlinear characteristics of air flowing through a variable area orifice. Further complications arise from the geometry of the mechanism because the equations of motion are highly nonlinear. The order of the dominant dynamics is shown to vary with the position of the mechanism.