Showing papers on "Actuator published in 1989"

Compact cable transmission with cable differential

Abstract: A pretensioned cable transmits power along a first support member (link) from a rotary actuator to a rotating output joint, typically an output pulley fixed to a second link arm but rotatable in a coupling between the first and second links. A reducer, typically two sets of coupled idler pulleys of different diameter, is mounted at a point removed from the actuator, and preferably as close as possible to the output joint. An axially split spool mounted on the actuator output wraps the outgoing and returning cable sections on different halves of the spool in opposite directions to provide pretensioning of the cable in the entire cable circuit at one point. To form a differential, a pretensioned cable carried on paired pulleys having smooth outer surfaces parallel to the axis of rotation couples the pulleys. The pulleys have axes of rotation that can intersect and their cable carrying surfaces are closely spaced, preferably by less than half the width of the cable. The outer surfaces can be stepped to accommodate two or more cables for bi-directional operation, or to create a conventional differential with a spider. The links and pulleys of the transmission are long and narrow. This high aspect ratio provides a compact configuration that is conducive to whole arm manipulations where any exterior surface of the links can engage an object. A low inertia, low friction brushless D.C. motor operating under the control of a pulse width modulated controller responsive to the current drawn by the motor, in combination with the cable transmission of this invention, provide excellent force control.

Remotely controllable power control system

Abstract: A remotely controllable power control system wherein the power supplied to a load may be varied locally via an actuator, positionable through a continuous range, on a wall control or from a remote location using a remote control device not electrically wired to the wall control. The load control system includes a transmitter and a wall control/receiver, each having a control actuator for adjusting the power supplied to the load. Control can be obtained by either the transmitter or the wall control/receiver immediately upon manipulation of either control actuator, with the adjustment in power level occurring substantially instantaneously. Communication between the transmitter and the wall control/receiver is by digitally encoded infrared signal.

Improving the efficiency of time-optimal path-following algorithms

Abstract: A method is presented which significantly improves the computational efficiency of time-optimal path-following planning algorithms for robot manipulators with limited actuator torques. Characteristics switching points are identified and characterized analytically as functions of the single parameter defining the position along the path. Limit curves are then constructed from the characteristic switching points, in contrast with the so-called maximum velocity curve approach of existing methods. An efficient algorithm is proposed which utilizes the characteristics of the defined concepts. The algorithm can also account for viscous friction effects and smooth state-dependent actuator bounds. A numerical example, while showing the consistency of the algorithm with the existing techniques, demonstrates its potential for increasing computational efficiency by several orders of magnitude. >

Robot Path Planning with Obstacles, Actuator, Gripper, and Payload Constraints

Abstract: A method is presented to obtain the time-optimal motions for robotic manipulators. It considers the full nonlinear dynamics of the manipulator, its actuator saturation limits, and gripper and payload constraints. It also accounts for both the presence of obstacles in the work space and restrictions on the motion of the manipulator's joints. The method is computationally practical and has been implemented for the optimal trajectory planning of general six degree-of-freedom manipulators. Examples are presented that demonstrate the substantial improvement in manipulator performance that can be achieved using this method.

Magnetic disk drive incorporating a magnetic actuator lock and a very small form factor

Abstract: The invention provides a magneticf actuator lock for the head positioning actuator of a disk drive. The magnetic actuator lock comprises a magnet, and first and second stop means, one of which is attached to the head positioning actuator. The stop means constitute a low reluctance pathway for magnetic flux, thus attracting and "latching" the two stop means together. This magnetic actuator lock does not require an additional permanent magnet but may use the magnetic force of the permanent magnet in a voice coil motor.

Position controlling apparatus

Abstract: The position controlling apparatus of this invention is to curve an endoscope insertable part or a catheter and is provided with an actuator having a shape memorizing alloy body. The shape memorizing alloy body is heated or cooled by a driving appartaus and the actuator is displaced by such heating or cooling. The difference between the actual displacement of the actuator driven by the driving apparatus and the objective displacement of the actuator is output by a comparing means which operates the driving apparatus on the basis of this difference. A resistance value detecting circuit detects the resistance value of the shape memorizing alloy body varying when the shape memorizing alloy body is heated or cooled. The detected value detected by the resistance value detecting circuit is input into a controlling apparatus which controls the driving apparatus on the basis of the detected value and the preset used temperature range of the shape memorizing alloy body.

Rubber gas actuator driven by hydrogen storage alloy for in-pipe inspection mobile robot with flexible structure

Abstract: The authors describe rubber actuators using a hydrogen storage alloy for an in-pipe inspection robot, which is capable of moving inside pipelines with inner diameter as small as 2 in. Rubber actuators with both stretching and shrinking capability are shown for realization of such a robot. The proposed robot uses twelve actuators, including six kinds of independently controlled actuators, so that it si more flexible and adaptable in motion: it can move in an inchworm mode through pipelines, it is adaptive for changing pipe diameters, and it is able to pass over the L- and T-joints of pipelines. The robot actuators can initially be achieved and prepared by hydrogen gas. The control method is also shown, with a T-joint movement as an example. >

Digital servo valve system

Abstract: A novel digital servo valve system for use in displacing an actuator is capable of operating either in closed or open loop mode. The system includes a controller that compares computed values of actuator parameters with preselected parameter values and iteratively determines therefrom command signals for the servo valve. The servo valve is characterized by a ball screw mechanism that eliminates mechanical backlash and a torsion bar which increases radial and angular compliance. A servo valve provided according to the present invention also displays reduced flow forces using a simple, inexpensive valve body in combination with a uniquely configured displaceable spool.

Conscious effort safety switch

Abstract: A three-position electrical switch includes a rocker-type actuator adapted to be pivoted within a housing in opposite directions from a neutral position to first and second actuated positions in order to close first and second sets of switch contacts The actuator carries a latch which normally engages the housing to prevent the actuator from being pivoted from its neutral position to either of its switch-closed positions By manually sliding the latch and then pivoting the actuator, the actuator may be moved to either of its switch-closed positions; the two-step operation requiring a conscious effort and protecting against accidental actuation of the switch The actuator is frictionally maintained in both of its switch-closed positions but may be returned to its neutral or switch-open position by a simple single motion thereby enabling rapid and easy opening of the switch

Dynamical Feedback Compensator for Uncertain Time-Delay Systems Containing Saturating Actuator

Abstract: The problem of the stabilization of an uncertain time-delay system with a saturating actuator is discussed. These uncertainties may be linear, non-linear, and/or time-varying, but only the upper bounds are known. A linear dynamical feedback compensator is used to stabilize this uncertain saturating and time-delay system. The concept of matrix measure and the comparison theory are employed to investigate the robust stability condition which assures asymptotic stability. One example is given to illustrate the application of the proposed design method.

Multiple model adaptive controller for the STOL F-15 with sensor/actuator failures

Abstract: A multiple-model adaptive controller that provides for reconfiguration in response to sensor and/or actuator failures is developed for an approach and landing profile for the short-take-off-and-landing (STOL) F-15 aircraft. Each elemental controller within the multiple model controller is based on a command-generator-tracker/proportional-plus-integral/Kalman-filter design employing reduced-order models, and each assumes a particular system status: no failures or a single failed surface or sensor. Filter residual monitoring is used as the mechanism for selecting the appropriate weighting coefficients for blending the outputs of the elemental controllers. The entire controller is evaluated against a higher order truth model with a selected failure, and the process is repeated for all failure modes of interest. >

Magnetic parking device for disk drive

Abstract: A magnetic parking device for locking an actuator in a disk drive (30) over a transducer landing zone (61). A magnetically permeable capture member (100) provided on an actuator arm (50) magnetically interacts with a permanent locking magnet (90) thereby locking a transducer (38) in the landing zone (61). A bucking coil (85) is provided arranged about the permanent locking magnet (90) for passing a current to generate a magnetic field with polarity opposite that provided by the permanent locking magnet (90) to neutralize the magnetic field to release the actuator from the parked state.

Active vibration control of flexible rotors: an experimental and theoretical study

Abstract: This paper develops the authors' earlier work on vibration control of multi-mode rotor-bearing systems. It shows how a single magnetic actuator can be used to estimate system characteristics and apply the optimum control force needed to minimize synchronous vibration. In the application considered here, a rotor is supported on oil-film bearings. The algorithm determines the optimum control force without prior knowledge of the bearing or rotor characteristics or the distribution of out-of-balance forces. A rig is described and used to illustrate the application of the theoretical work.

Actuators for micro robots

Abstract: The problem of scaling robot actuators down to microscopic scale is examined in a review. It is shown that several forces scale well into the micro domain. These include electrostatics, hydraulics, pneumatics, and biological forces. Electromagnetic forces have a less favorable scaling. The scaling of electrostatics and electromagnetics is explained, and two electrostatic actuators are presented. The first actuator is a harmonic electrostatic motor. This motor uses rolling surfaces that reduce friction, and has an integral gear reduction that increases the torque output of the motor. The second actuator is designed to move fibers into alignment with other fibers. >

Integrated distributed sensing and active vibration suppression of flexible manipulators using distributed piezoelectrics

Abstract: Structural oscillation of flexible robot manipulators would severely hamper their operation accuracy and precision. This article presents an integrated distributed sensor and active distributed vibration actuator design for elastic or flexible robot structures. The proposed distributed sensor and actuator is a layer, or multilayer of piezoelectric material directly attached on the flexible component needed to be monitored and controlled. The integrated piezoelectric sensor/actuator can monitor the oscillation as well as actively and directly constrain the undesirable oscillation of the flexible robot manipulators by direct/converse piezoelectric effects, respectively. A general theory on the distributed sensing and active vibration control using the piezoelectric elements is first proposed. An equivalent finite element formulation is also developed. A physical model with distributed sensor/actuator is tested in laboratory; and a finite element model with the piezoelectric actuator is simulated. The distributed sensing and control effectiveness are studied.

Convex analysis and global optimization of joint actuator location and control problems

Abstract: It is shown that the optimal value of the continuous-time linear-quadratic problem regarded as a function of the system model and index parameters exhibits properties (convexity, concavity, and monoticity) specially suitable for optimization purposes. Based on this fact, a procedure for the global solution determination of eventually nonconvex problems, involving the above-mentioned function, is proposed. Such problems embody some known designs, such as filtering under noise uncertainty or precision constraints and optimal actuator/sensor location. The last problem is deeply analyzed, and two practical applications, namely satellite attitude control and large flexible system control, are included. >

Dual mode actuator for disk drive useful with a portable computer

Abstract: A portable computer having an associated disk drive includes a voltage multiplier coupled between a microprocessor and a head positioning actuator that operates in two modes. In a moderate performance mode, the dual mode actuator operates with the power supplied by a storage battery or by a commercial power source with the voltage multiplier turned off. In a high performance mode, the voltage multiplier under control of the microprocessor boosts the voltage supplied to the actuator so that more power is made available for fast head positioning and job execution with an improvement in computer performance.

Method and system for controlling a pressure regulator

Abstract: A method and system are provided for controlling a pressure regulator and an electric actuator mechanism for operating the pressure regulator by modifying a generated error signal as a function of at least one correction factor so that the actuator mechanism is controlled as a function of the actual level of regulated control fluid pressure to compensate for varying system operating conditions. A first correction factor is generated as a function of the difference between an actual pressure differential signal and an expected pressure differential signal. A second correction factor is based on the level of a feedback signal which is a function of the actual pressure of the regulated control fluid. An error signal generated by the method and system defines a ramp signal, wherein the shape of the ramp signal is defined by a data matrix of actual pressure differentials. The ramp signal may have a linear, exponential or a constant accelerationdeceleration shape. Preferably, the pressure regulator is a pilot operated pressure regulator and the actuator mechanism includes an up solenoid and a down solenoid.

Voice coil activated disk drive parking device with magnetic bias

Abstract: A parking device (66) for parking the actuator (30) and the heads (32) in a disk drive (20) utilizes the magnetic field provided by the magnet (50a, 50b) in the actuator (30). A permeable latch return (82) provided in the magnetic field creates an attractive force which biases the parking device (66) to a latched position. A coil (80), provided on the parking device (66), passes an electric current in the magnetic field provided by the actuator (30) to create a force which releases the parking device (66).

A linear SMA motor as direct-drive robotic actuator

Abstract: A push-pull actuator for commanding the motion of the interphalangeal joints of anthropomorphic robotic hands is proposed. The actuator, based on coil springs, made of the shape-memory alloy Nitinol, is compact enough to be easily incorporated into the phalangeal structure of a robotic finger, thus eliminating the complex routing of the cables and tendons usually adopted for transmitting motion from conventional actuators (e.g. DC servomotors) to the joints. The performance of the SMA actuator is illustrated, and the concepts of temperature, strain, and stress limits for the control of the whole push-pull actuating system are emphasized. The methods adopted to improve the usually limited frequency response of SMA actuators are also described. Finally, the control of the whole system and some experimental results demonstrating promising actuator performance are discussed. >

Pre-tensioned shape memory actuator

Abstract: A pre-tensioned shape memory actuator for providing remote actuation at relatively high loads. The actuator utilizes a two-way shape memory alloy which is pre-tensioned to a pre-tensioned position, then partially compressed to a position intermediate its original position and the pre-tensioned position so as to allow the actuator unit to then fore-shorten back to the original position when heated, and to expand back to the intermediate position when again allowed to cool. The alloy is a part of a clamping device which applies compressive force to a work object at the intermediate position under normal temperatures and releases the compressive force when heated. Upon cooling, the cycle is completed as the memory alloy reverts to the intermediate position and once again applies the compressive force to the work object.

Estimator positioning system and method.

Abstract: A system and method for controlling the movement of a member, particularly the heads of a disk file, to a specified position in a predetermined path, makes use of an electromagnetic actuator responsive to control signals and of position reference information and a transducing means for reading such information to produce a position signal. The position signal is sampled regularly and, together with the actuator control signal, used to update a velocity estimator. During the deceleration phase of the movement, a new actuator control signal is generated at each sample time from the square of the estimated velocity divided by the computed distance-to-go to the specified position.

Master cylinder assembly

Abstract: A master cylinder assembly and a motor vehicle power assist actuator utilizing the master cylinder assembly. In one form of the invention, a clutch actuator is provided in which the clutch may be actuated in the usual manner by depression of the clutch pedal to move the piston in the master cylinder assembly under the urging of the push rod or, in a power mode of the actuator, movement of the gear shift lever of the vehicle is sensed by a logic module whereupon the electric motor of the master cylinder assembly is energized in a sense to move the ball screw to apply a power assist force to the annular outer periphery of the rear end of the piston and thereby effect disengagement of the clutch. In another embodiment of the invention, the signal to the logic module to enable energization of the motor is generated by a switch connected to the clutch pedal so that the force for disengaging the clutch includes a manual force applied by the push rod and a power force applied by a ball screw. In a further embodiment of the invention, the master cylinder assembly is utilized in a power assist brake actuator wherein a proportional potentiometer senses the pivotal movement of the brake pedal and provides a power assist, via the logic module, to the ball screw that is proportional to the extent of pivotal movement of the brake pedal.

Toggle-acting dispensing closure with impact resistance

Abstract: A toggle-acting dispensing closure which is resistant to inadvertent actuation during shipping and handling prior to purchase. A deformable resistance post is provided on the body of the closure and interferes initially with the pivoting of the actuator except when a substantially higher force than normally used to pivot the actuator is applied. After the first operation by applying the substantially higher force, the actuator may be operated by the application of a customary lower operating force to the actuator.

Actuator design for rotor control

Abstract: Active control of dynamical behavior of rotor systems involves the following modeling of the rotor system including active elements as a control process, positioning of actuators and sensors, implementation of problem-adapted control concepts. The key to attaining the desired influence on the dynamic behavior of rotor systems lies in the presence of suitable actuators. Some types of actuators (magnetic, electrohydraulic and piezoelectric) will be discussed and their respective drawbacks indicated. Their design will be outlined and functional correlations will be presented. Theoretical and experimental results demonstrate that an improvement of the system dynamics by the use of control forces is always possible.