Showing papers on "Actuator published in 1988"

Shape memory alloy servo actuator system with electric resistance feedback and application for active endoscope

Abstract: A control system for a shape memory alloy (SMA) servo actuator, and its application to a unique medical tool, are considered. It is thought that the electric resistance value of an SMA can be utilized to monitor the transformation of the SMA directly. Therefore, an antagonistic transformation control scheme using electric resistance feedback is proposed and is verified by several experiments. This control scheme reduces the open-loop hysteresis of an SMA actuator and improves greatly its robustness against heat disturbance due to changes in the cooling condition. Research into the application of the method in an active endoscope is reported. It consists of five segments of 13 mm diameter, 40 mm length each. The bending angle of each segment can be controlled individually from outside by using antagonistic electric resistance feedback without any motion sensors. A model for smooth insertion to the colon is verified. >

Thermally excited silicon microactuators

Abstract: A cantilever-type micromachined silicon actuator based on the bimetal effect used extensively for the fabrication of temperature-controlled electrical switches is described. The silicon actuator consists of a Si-metal sandwich layer and an integrated poly-Si heating resistor as a driving element. Due to the low heat capacity of the transducer element, a high temperature increase per input power unit can be achieved. For a (Si-Au)-cantilever-type actuator, 500- mu m long and several micrometers thick, a specific deflection of approximately 0.1 mu m/K at the free end has been measured. The design considerations, fabrication process, and experimental results of the actuator are discussed. >

Touchscreen CRT with tactile feedback

Abstract: Apparatus for providing tactile feedback in response to the touch input command of a user to the touchscreen of a cathode ray tube in a CRT command and display system. An actuator is provided for imparting motion to the CRT when the actuator is energized. Energization occurs in response to a touch input command of the user to the touchscreen of the CRT. When energized, the actuator provides tactile feedback to the user by imparting motion to the CRT.

Actuator for the frictional engaging device

Abstract: An actuator for a four wheel drive transfer mechanism which is laid in a power transmission device and is controlled by an electrical signal sent from a controlling unit comprises a torque generating mechanism which converts electrical energy into a torque, and a torque-thrust conversion mechanism which converts the torque generated by the torque generating mechanism into a thrust force. The thrust force generated from the torque-thrust conversion mechanism is applied to the frictional engaging device to control torque distribution between front and rear vehicle wheels.

Constant speed holding device

Abstract: A constant speed holding device for a vehicle includes a running speed detector, an aimed speed setting unit, a speed deviation calculating unit for calculating a speed deviation, an acceleration calculating unit, a first pulse width calculating unit responsive to a speed deviation signal from the speed deviation calculating unit and an acceleration signal from the acceleration calculating unit for calculating a pulse width of a first pulse signal having a predetermined period, an acceleration memory unit for storing a value of the acceleration signal in the past, an aimed acceleration generating unit responsive to an output of said acceleration memory for generating a desired aimed acceleration, an acceleration deviation calculating unit responsive to the aimed acceleration signal and the acceleration signal for calculating an acceleration deviation, a second pulse width calculating unit responsive to the acceleration deviation signal for calculating a pulse width of a second pulse signal having a predetermined period, an output pulse selection unit for selecting either the first or the second pulse signals, whichever is suitable, and an actuator responsive to a selected output pulse signal for on-off controlling a throttle valve of an engine of the vehicle based on the pulse width thereof.

The stability of feedback control with nonlinear saturating actuator: time domain approach

Abstract: Sufficient conditions for stability of closed-loop systems with a saturating actuator are derived from the viewpoint of time domain. The Bellman-Gronwall inequality is used to investigate the stability of these systems. Three kinds of controllers are considered to treat this constrained control problem. Finally, an example is given to illustrate the results. >

Hall-effect controller

Abstract: A Hall-effect control apparatus incorporating an actuator member having a magnetic core, and which is pivotally mounted on a base for movement in X-axis and Y-axis directions. An electrically energized coil excited with a. c. voltage produces a fluctuating magnetic field in the vicinity of the core. Four Hall-effect sensors are mounted on the base, and are arranged to sense changes in the a. c. field as the core member moves. The output of the Hall-effect sensors is both d. c. and a. c.; an electrical circuit connected therewith processes these voltages so as to cancel out any d. c. components thereof. The output of the electrical circuit in turn provides two voltages which are indicative of the X-axis and the Y-axis positions of the actuator member. The device is immune to interruption arising from d. c. fields, such as that of the earth; also significant immunity against error due to temperature fluctuations is realizeable, as is immunity to error arising from aging of the various components. There is thus achieved improved accuracy and linearity as compared to the various devices of the prior art.

Combine harvester cleaning apparatus

Abstract: A combine harvester having a threshing and separating mechanism and a grain cleaning mechanism disposed beneath the threshing and separating mechanism and including a grain pan fitted with a movable divider apparatus and operable to receive grain from the threshing and separating mechanism, sieve mechanism operable to receive grain from the grain pan, and a fan operable to blow air through the sieve mechanism, is disclosed wherein an inclination sensing mechanism for sensing the lateral inclination of the combine harvester is operatively associated with an actuator operatively coupled to the grain pan divider apparatus for positionally adjusting the grain pan divider apparatus in response to the output of the inclination sensing mechanism to compensate for any given lateral inclination of the harvester. The sieve mechanism includes sieve sections pivotally mounted for lateral movement about respective fore-and-aft extending axes and operatively coupled to the actuator for positional adjustment thereof to effect a transverse leveling of the sieve mechanism when the combine harvester is laterally inclined.

Tamper-resistant brake actuator

Abstract: The present invention provides a tamper-resistant fluid-operated brake actuator having a power spring housed within a head or cap which is attached to a flange case having one or more diaphragms or pistons responsive to changes of fluid pressure within the brake actuator chambers. In one embodiment, the head is attached to the flange case by a substantially continuous curvilinear annular metal retaining member which must be inelastically deformed or destroyed in order to remove the head from the flange case, thus rendering tampering more difficult. In another embodiment, the annular metal retaining member of the present invention is integral with the actuator head and which is metal-spun or the like onto the flange case.

Vehicle suspension system, and method of operating same

Abstract: An ''active'' suspension system provides two parallel force-transmitting paths between the body and wheel of a vehicle. The first path has a main spring (41), and the second path includes an actuator (42) and a spring (43). LVDT's (53, 55) are arranged to monitor the displacements of the actuator (42) and the spring (43). The actuator is arranged in a high-gain closed position or velocity servoloop. The actual force (Fw) exerted by the suspension system on the body is determined and compared with a desired force (Fc) to produce a force error signal (Fe). The force error signal (Fe) is converted to a command signal supplied to the servoloop. The servoloop operates the actuator (42) so as to continuously drive the force error signal (Fe) toward zero.

Bistable SME actuator with retainer

Abstract: In a bistable shape memory effect, SME, mechanism having first and second opposing shape memory effect, SME, elements (16, 20) moving an actuator (12) along a travel stroke between respective first and second positions upon heating of the respective SME element above its transition temperature mechanical frictional retainers are provided for holding the actuator at the end of its travel stroke, including after cooling of the respective SME element and return repose movement thereof. One embodiment provides a detent retainer (38, 40, 42, 44, 46). Another embodiment provides a friction wedge retainer (12a, 12b, 14a, 14b, 12c, 12d, 14c, 14d). Another embodiment provides a resiliently biased friction member (50, 52) and a lost motion coupling (56, 58) between the actuator and the SME elements.

A new three degrees of freedom electromagnetic actuator

Abstract: The design of an electromagnetic actuator rotating around three independent axes is presented. The actuator consists of a spherical armature moving around its center; inside this armature are situated three fixed inductors. When power is supplied, the three phase windings of each inductor develop a moving magnetic field acting along its own plane of symmetry. The spherical armature of the actuator is made of magnetic steel; on the inner face, a thin layer of copper has been fixed. In that way, each inductor and the portion of armature that is in front of it behaves like a linear induction motor. When the inductors are adequately supplied with electricity the armature moves inside a solid angle. The actuator developed by the authors moves inside a cone, with a maximum deviation of +or-30 degrees . To make it work and to have good positioning, the actuator is equipped with sensors that detect the position of the armature. The electric power is supplied by three PWM transistor inverters, one for each inductor. >

Endoscope with elastic actuator comprising a synthetic rubber tube with only radial expansion controlled by a mesh-like tube

Abstract: An endoscope has a flexible insertion portion having distal and proximal end portions. Elastic actuators for bending the insertion section are mounted in the insertion section. Each elastic actuator has an inner space and is longitudinally expanded/contracted when a fluid is supplied to/discharged from the inner space. A converting unit is provided in the insertion section and converts an expanding/contracting motion of the elastic actuator into a bending motion of the insertion section. The elastic actuator is connected to a control unit for controlling the fluid in the inner space of the elastic actuator.

High performance, high capacity micro-winchester disk drive

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, and 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.

Control of a single-link flexible beam using a Hankel-norm-based reduced order model

Abstract: A single-link flexible beam is an infinite-dimensional system. A full-order model containing all the modes of the system within the bandwidth of the actuator and sensors is presented. Such a model would result in a high-order controller which may not be feasible to implement in practice. Hence, a low-order model for the system is obtained using Hankel norm minimization. A controller is designed for the beam on the basis of the reduced-order model thus obtained. Experimental results show that a controller designed for the reduced-order model guarantees effective vibration control of the flexible beam. >

Transient finite element modeling of solenoid actuators: the coupled power electronics, mechanical, and magnetic field problem

Abstract: A transient 2-D finite element model for fast-acting pulse-width-modulated (PWM) solenoid actuators is presented. The unique feature of this model is that it couples the electrical, mechanical, and magnetic systems of these devices. Transient calculations taking into account the nonlinearity of the magnetic materials, eddy currents, and motion are compared with dynamic test results for a ball-type solenoid. Flexibility of the software allows one to apply it to any type of PWM solenoid actuator and any desired excitation profile. >

Vibration wave motor

Abstract: A vibration wave motor includes a housing, a rotor, a bearing member, a bending-vibration driving transducer having a support shaft and two driving elements and serving as an actuator, and a leaf spring having a pressing protrusion. The transducer is slidable in an opening of the housing along a rotation axis direction of the rotor, and a support shaft of the transducer is rotatably supported and inserted. The transducer is held while being urged by the leaf spring and being in contact with the rotor. Since the transducer is urged by the pressing protrusion of the leaf spring, the leaf spring is in complete contact with the transducer without edge contact so that the two driving elements are evenly in contact with the rotor in a direction perpendicular to the frictional contact surface, thus providing driving conditions of superior conversion efficiency.

Electrically actuated disc brake.

Abstract: The electrically actuated disc brake (10) comprises a caliper (12) having a bore (16) receiving therein an actuating mechanism (90), and an electric motor (40) attached to the caliper housing (12). The actuating mechanism (90) comprises a planetary gear mechanism (50) which includes a sun gear (52), planetary gears (54), and a pair of ring gears (70, 80). An acutator sleeve (68) is disposed about the ring gears (70, 80) and contains a helical groove (69) disposed opposite a complementary-shaped helical groove (89) in a rotatable ring gear (80). The helical grooves (69, 89) receive therebetween a bearing mechanism (85) biased by a spring (87) toward a fixed stop (86) located within the helical grooves (69, 89). Operation of the electric motor (40) effects rotation of the rotatable ring gear (80) and axial displacement of the actuator sleeve (68) into engagement with a thrust pad (96) located adjacent one of the friction elements (18) so that the caliper (12), by reaction, displaces the other friction element (20) into engagement with the rotor (22).

Development of shape-memory alloy actuators. Performance assessment and introduction of a new composing approach

Abstract: A servo actuator using shape-memory alloy (SMA actuator), which performs special functions not found in conventional actuators, is expected to be a new driving source for future robots. This paper evaluates its performance and discusses the fundamental issues in designing such actuators. Being driven by the thermal martensitic transformation of the SMA itself, an SMA actuator is a driving system which can in principle, perform without any frictional parts, can be designed at a high output/weight ratio especially when a light-weight actuator is to be constructed But has low energy efficiency due to its mechanical characteristics of operating at a small temperature difference, and has a relatively low response. Our study shows some ways of overcoming these disadvantages by a special design approach. The method is called ξarray and is characterized by SMA wires being connected in parallel structurally and in series electrically. This approach enables the response to be enhanced due to the increased surface a...

Actuator fault detection and isolation in linear systems

Abstract: A scheme for the detection and isolation of actuator faults in linear systems is proposed. A bank of unknown input observers is constructed to generate residual signals which will deviate in characteristic ways in the presence of actuator faults. Residual signals are unaffected by the unknown inputs acting on the system and this decreases the false alarm and miss probabilities. The results are illustrated through a simulation study of actuator fault detection and isolation in a pilot plant doubleeffect evaporator.

Actuator for friction engagement device

Abstract: Disclosed is an actuator for a friction engagement device of the type adapted to allow power transmission between two shafts by releasing engagement of the friction engagement device concerned. The actuator comprises a torque/thrust conversion device composed of two elements and adapted to effect and release the engagment of the friction engagement device, a pair of gears respectively connected to the two elements, and a torque generating mechanism gear which is engaged with the pair of gears, the gear ratio between the torque generating mechanism gear and one of the pair of gears being slightly different from that between the torque generating mechanism gear and the other of the pair of gears. In this arrangement, the motor torque is directly converted into the power for effecting and releasing the engagement of the friction engagement device, whereby the control method is simplified and the response to the control signal expedited.

Modeling of web conveyance systems for multivariable control

Abstract: A distributed parameter model of the lateral dynamic behavior of a moving web in an n-roller system is proposed A span of web moving longitudinally and under tension is modeled as a beam with shear flexibility (Timoshenko beam) A quasistatic simplification of the model is made on the basis of spectral separation Boundary conditions at the web-roller interface are considered Actuator dynamics are introduced through the formulation of the boundary conditions Closed-loop simulations using a state-space version of the simplified model are in agreement with experimental results >

Latch mechanism for rotary actuator and the like

Abstract: A latch mechanism for use in a disc drive rotary actuator and like magnetic device includes a selectively energizable electromagnet mounted to the actuator and spaced from the magnets, and a ferrous arm pivotally attached between the magnets and the electromagnet whereby the latch arm can assume two stable positions of low magnetic reluctance for stray flux from the magnets. In one position the latch arm pivots towards the magnets and engages the rotary actuator. In the other position, the latch arm pivots towards the electromagnet and disengages the rotary actuator. Positioning of the latch arm is dependent on momentary energization and polarity of the electromagnet.

Shape memory metal precision actuator

Abstract: A shape memory metal actuator for accurately pointing or aligning a moveable piece of equipment or other object. The memory metal components (12, 14, 16, 18) are stretched along their axes and arranged in a push-pull configuration so that one element (14) in the activated state moves the object while another element (18) on the opposite side of the object is strained while it is in the soft state to act as a dynamic damper to prevent overtravel of the object. The wires can be heated with external heaters or by electrical current passed directly therethrough. Two separate actuator assemblies using orthogonal pairs of shaped memory metal wires (42, 44, 46, 48 and 52, 54, 56, 58) are used to enable pivotal movement about a floating pivot point 41, while a cantilevered arrangement of Nitinol bars (88, 90, 92 and 94) are used to enable pivotal movement about a fixed flexure point F.

LQG-control of a highly resonant disk drive head positioning actuator

Abstract: A fast fine-positioning controller has been designed for a rotary-actuator-type magnetic-storage disk drive. The controller was designed using the LQG (linear quadratic Gaussian) methodology and has been implemented on a digital signal processor. It is shown that LQG design is a viable approach, and that various problems associated with the structural resonances of the actuator can be solved. >

Theoretical and experimental investigation of space-realizable inertial actuation for passive and active structural control

Abstract: Inertial reaction devices are investigated for use as passive vibration absorbers and active control actuators for flexible space structures. Absorbers are designed for one- and two-degree-of-freedom structural representations using three parameter optimization techniques. All three yield nearly identical designs and indicate that inertial devices should be tuned to the lowest mode intended to receive increased damping. The optimal passive components of the control actuator are found to be those of the optimal passive vibration absorber. Proof-of-concept laboratory tests were performed on a quasi-free-free beam using inertial reaction devices that are space-realizable, i.e., conceptually capable of functioning in the space environment. The inertial devices were used as both passive absorbers and tuned actuators. Damping was significantly increased using both passive and passive/active techniques. Additional tests indicated the benefits and limitations of actuator tuning and the necessity of performing realistic experiments using space-realizable hardware.

Microprocessor controlled force actuator.

Abstract: The mechanical and electrical design of a prototype force actuator for vibration control of large space structures (LSS) is described. The force actuator is an electromagnetic system that produces a force by reacting against a proof-mass. The actuator has two colocated sensors, a digital microcontroller, and a power amplifier. The total weight of actuator is .998 kg. The actuator has a steady state force output of approximately 2.75 N from approximately 2 Hz to well beyond 1000 Hz.