Abstract: The demand for actuators featuring biomimetic properties, such as linearity, high power density and compliance, is growing in microrobotics and bioengineering. In the present paper a novel linear actuator is presented. It exploits the electromechanochemical phenomena of -electron conjugated conducting polymers, occuring when ionic species are exchanged with the surrounding medium, i.e. solid or liquid electrolyte. In our experiments, a polypyrrole film doped with benzensulphonate anions is considered as the conducting polymer and a liquid electrolyte bath as the ionic reservoir. The actuating properties of the material are investigated and quantified in terms of both isotonic displacement and isometric developed force. A lumped parameter, muscle-like model of the system is proposed and verified with respect to the experimental data. The results of the electromechanical characterization and the goodness of fit of the model provide favourable indications for the utilization of the material as an effective muscle-like linear actuator, once the response time is decreased by means of a suitable scaling down of the film thickness.

Abstract: Actuator rate saturation is an important factor adversely affecting the stability and performance of aircraft flight control systems. It has been identified as a catalyst in pilot-induced oscillations, some of which have been catastrophic. A simple design technique is described that utilizes software rate limiters to improve the performance of control systems operating in the presence of actuator rate saturation. As described, the technique requires control effectors to be ganged such that any effector is driven by only a single compensated error signal. Using an analysis of the steady-state behavior of the system, requirements are placed upon the type of the loop transmissions and compensators in the proposed technique. Application of the technique to the design of a multi-input/multi-output, lateral-directional control system for a simple model of a high-performance fighter is demonstrated as are the stability and performance improvements that can accrue with the technique.

Abstract: A linear actuator including a socket on a first element of a motor vehicle steering column, an expandable nut loosely disposed in the socket, and a screw shaft rotatably supported on a second element of the steering column. The expandable nut consists of a front segment facing a distal end of the screw shaft and a back segment behind the front segment. An inside screw thread in the back segment of the expandable nut is angularly phased relative to an inside screw thread in the front segment. The expandable nut self-aligns with the screw shaft when the latter is screwed into the inside screw thread in the front segment. An outboard end of the thread groove in the screw shaft defining the outside screw thread thereon spreads apart the front and back segments of the expandable nut to positions resiliently wedged between the screw shaft and the socket to eliminate lash between the screw shaft and the first element of the steering column. In a preferred embodiment, the expandable nut is a molded plastic nut having front and back segments connected by an integral living hinge.

Abstract: An electrohydraulic control system includes a hydraulic pump (44) coupled to a bidirectional electric motor (12) and having ports (50, 52) for supplying hydraulic fluid in either of two flow directions as a function of direction of rotation of the motor. A hydraulic actuator (18) is coupled to the pump ports for receiving fluid in either of two flow directions. An electronic controller (32) is connected to in or more sensors (34) operatively coupled to the actuator, so that the motor is controlled as a function of motion of the actuator. The bidirectional electric motor is a fluid-cooled motor, and the system includes valves (22, 24) for routing hydraulic fluid through the motor housing between the pump and the actuator.

Abstract: A linear actuator has four drive gears which engage two racks. The actuator movable member may comprise two racks which have gear teeth which face inwardly and towards each other, or a single rack which has gear teeth which faces outwardly. In either case, four gear drives to engage the rack, two gear drives on each side. A plurality of linear actuators may be used to provide for position control in two or more directions. Control is provided by a servo mechanism.

Abstract: A linear solenoid valve is composed of a pressure regulating section and an actuator section. In the pressure regulating section, a valve spool is slidably disposed and is biased in one direction by a single elastic member. The actuator section generates a thrust force and transmits that generated thrust force in an opposite direction to the pressure regulating section via a shaft. The actuator section is a movable magnet type linear actuator which includes three serially disposed coils and two permanent magnets disposed within the coils with like poles of the permanent magnets facing each other. The linear solenoid valve generates a stable control pressure which is large in proportion to input current, while generation of hysteresis and of radial load in the actuator section is avoided and responsiveness is improved.

Abstract: An active nonlinear vibration absorber for flexible structures is developed. The absorber exploits the inherent quadratic nonlinearity of the actuator material Terfenol-D to produce a two-to-one autoparametric resonance between the forced vibrations of a structure and a second-order analog controller circuit. Nonlinear resonance of this type exhibits the well-known saturation phenomenon. When the structure is forced near resonance, its response saturates to a small value. This type of control has been demonstrated by previous researchers using linear actuators where nonlinearities were introduced via the analog circuit. In contrast, we use the natural nonlinearity of the Terfenol-D material to achieve the same results. We develop the theory and present experimental results for the control of the first and second modes of a cantilever beam. We also consider the application of the strategy experimentally when the forcing is due to a rotating imbalance. In this case, the excitation source is nonideal. Our results indicate that the saturation based control technique implemented with a Terfenol-D actuator constitutes an effective nonlinear vibration absorber.

Abstract: An actuator has a linearly elongate frame, side, end, and top covers detachably and selectively mounted on side surfaces of the frame, a table mechanism displaceable in the axial direction of the frame in response to energization of an electric motor, and a ball screw for transmitting drive forces from the electric motor to the table mechanism. The operator can select various actuator configurations depending on the environment in which the actuator is to be installed and the application in which the actuator is to be used. In the preferred embodiment, the ball screw is used in combination with a piston/cylinder arrangement for moving the table mechanism in a linear direction. The piston/cylinder having a magnetic coupling for coupling the piston to the table mechanism.

Abstract: In this paper for the first time a modular built dynamic microsystem consisting of a combination of two separately fully functional fluidic devices fabricated by the LIGA-technique is presented. One of the two devices is a fluidic micro-oscillator, which needs only one fluid supply to generate an oscillating fluid jet at its two output ports. The other device is a linear actuator in which the fluidic energy is transformed into mechanical energy via a double acting piston placed in a linear actuator housing. Together the two devices form a dynamic microsystem which can be used in medical application.

Abstract: An electrically actuated hydraulic power cylinder (10, 100, 200) for use in a vehicle braking system. The power cylinder includes an electric motor (12, 102, 202), a rotary-to-linear actuator for converting rotary motion of the electric motor to a linear motion, and a hydraulic cylinder. In a preferred embodiment, the rotary-to-linear actuator is a roller screw assembly (14, 104, 204). The roller screw assembly converts rotational motion generated by the motor into axial movement of a piston which is disposed within the hydraulic cylinder. The movement of the piston pressurizes a volume of fluid. The pressurized fluid flows through an outlet port (20) connected to either a single wheel brake cylinder (21) or a plurality of wheel brake cylinders, thereby actuating the associated wheel cylinder. In a specific embodiment of the invention, the roller screw assembly is incorporated into the internal structure of the motor for compactness and weight reduction. Also, the hydraulic cylinder may be integrated into a wheel brake assembly for compactness and weight reduction.

Abstract: A micro-gripper actuated by laser power has been developed. The laser-powered micro-gripper is designed for handing micro-objects in very narrow space or overly crowded places, consists of a laser-powered linear actuator and a photoformed micro-gripper. This linear actuator's maximum output power was 2.3 mN and the stroke length was 900 /spl mu/m, and the total dimension of the linear actuator is about 25 mm in length and 2 mm in diameter.

Abstract: The Far Ultraviolet Spectroscopic Explorer (FUSE) spacecraft requires a micropositioning linear actuator. The actuatorneeds to provide a moderately long stroke (>4OOtm), high accuracy (>±2j.tm), low power (4 Watts), simple control, and arelatively small package, for X-axis mirror positioning. These requirements could not be met by traditional linear actuatortechnologies. A new High Output Paraffin (HOP) actuator was designed to meet these specific requirements. This paperdescribes the design, qualification, and use of this actuator. HOP actuators have been used for many different applications inaerospace mechanical systems. Motion from these actuators is provided by the paraffm expansion during a solid-to-liquidphase change. The principles of operation for the actuator and the control philosophy ofthe system are discussed. Results ofsystem performance, including a total displacement of greater than 800j.tm, displacement rates in the 1 lOOim/min range, anaccuracy of and a life time of 15,000 full displacement cycles are discussed. The advantages and disadvantages ofthe HOP, as well as design and implementation considerations, are also discussed.

Abstract: The paper outlines DLR’s new 4-finger hand characterized by the fact that all 12 active joints (3 for each finger) are integrated into the fingers or the palm. With 112 sensors, around 1000 mechanical and around 1500 electrical components the new hand is one of the most complex robot hands ever built. Its key element is the „artificial muscle ®“ a small but powerful linear actuator, which seems to be one of the first real electromechanical alternatives to hydraulic or pneumatic actuators.

Abstract: The vehicle has a rectangular seat support frame (3) installed horizontally in the longitudinal direction of the vehicle. On its rear corner facing the longitudinal centre axis, the seat frame is connected by a mounting to a guide rail (2) vertically fixed in the vehicle and along which is effected the raising and lowering movements. The lifting unit has a linear actuator (4) parallel to the guide rail and driven by an electric motor (5).

Abstract: A sample handling mechanism including a direct drive carrier for positioning multiple trays or carousels of sample vials and a direct drive carousel handling mechanism that eliminates pulleys and belts and the problems associated therewith. The carousels handled by the sample handling mechanism are individually identifiable, stackable and include a viewing area for identifying and viewing the individual sample vials grouped in a respective carousel. The sample handling mechanism consists of two logical drive modules. A single center line or axis of rotation is effected in each of the drive modules. The two logical drive modules include a carrier mechanism that transports a plurality of sample carousels to a sampling station, and a carousel drive mechanism which engages a single carousel and presents the appropriate vial to be sampled. The carrier mechanism includes a multi-position spoke-like carrier portion that is driven by a single drive shaft coupled to a gear reduction stepper motor by a coupling. The carousel drive mechanism includes a linear actuator portion and a rotary actuator portion on a common center line or axis. The linear actuator portion effects engagement and disengagement of the rotary actuator portion with a properly positioned carousel, and includes a linear actuator stepper motor with a motor shaft attached to a lift housing. The lift housing holds the rotary actuator portion.

Abstract: The locking device comprises resilient repulsion means (58) which react between a fixed body (16) and one or more rolling members (42) and which tend to urge these members in the direction of wedging between two wedging surfaces (34, 36) associated with the body (16) and with the rod (12) of the actuator (10), respectively. A control piston (48) is arranged so as to engage the rolling members (42) in order to urge them in the release direction under the effect of a thrust exerted on the piston in the opposite direction to the force exerted by the resilient means (54).

Abstract: This paper presents the dynamic analysis of a reciprocating actuation system based on moving magnet actuator for gas compression. For the analysis of the linear actuator, an axisymmetric finite element method (FEM) considering the saturation effect of the magnetic material is used, and electrical circuit equation, mechanical dynamic equation and pressure dynamics are coupled. In the FE analysis, we adopt a moving line technique to save computation time and to perform the process efficiently. The pressure dynamics of the gas in the compressor is modeled by using the law of thermodynamics. The analysis results compare fairly well with experimental ones.

Abstract: The paper presents the theoretical analysis and experimental results of path tracking control of a class of vehicles widely used in underground mining operations. A vehicle consists of the front and rear units hinged together, where each unit has only one pair of nonsteerable wheels. Steering is performed by changing the angle between the front and rear units by means of a (pair of) hydraulic cylinders (linear actuators). In operation this vehicle moves in either forward or backward directions. Path tracking control problem is of the main importance in order to follow the relatively narrow mining corridors. It consists of using the sensory information to measure the deviations in position and orientation from the path to be followed. Based upon these two tracking errors a feedback system must govern the appropriate steering action.

Abstract: A microengine uses two synchronized linear actuators as a power source and converts oscillatory motion from the actuators into constant rotational motion via direct linkage connection to an output gear or wheel. The microengine provides output in the form of a continuously rotating output gear that is capable of delivering drive torque at a constant rotation to a micromechanism. The output gear can have gear teeth on its outer perimeter for directly contacting a micromechanism requiring mechanical power. The gear is retained by a retaining means which allows said gear to rotate freely. The microengine is microfabricated of polysilicon on one wafer using surface micromachining batch fabrication.

Abstract: PROBLEM TO BE SOLVED: To open/close fingers at high speed, to improve responsiveness, to reduce noises and further to simplify a structure by providing a crimping part having a supporting member for fingers, electromagnetic actuator for reciprocatively moving an output part, and link mechanism for opening/closing the fingers while being interlocked with the output part SOLUTION: The main part of a motor-driven artificial hand is composed of a crimping part 1 for freely turnably supporting 1st and 2nd fingers 11 and 12 through a supporting member 13, linear actuator 2 as the electromagnetic actuator for linearly moving an output part 21, link mechanism 3 for opening/ closing the respective fingers 11 and 12 of the crimping part 1 while being interlocked with the linear motion of the output part 21, and wrist part 4 connected to the linear actuator 2 Therefore, any decelerating mechanism or transforming mechanism constituted in the conventional motor-driven artificial hand with a miniaturized motor as a driving source is unnecessitated Further, since the output of the linear actuator 2 is directly transmitted to the link mechanism 3, the speed for opening/closing the fingers 11 and 12 is accelerated and responsiveness can be improved

Abstract: An anti-rotation mechanism in a linear actuator has outer and inner cylinders, affords high accuracy and rigidity, is simple in structure, not requiring the use of a tie rod, and is inexpensive to manufacture. The outer cylinder 3 has both end portions 3 of circular cross section and an intermediate portion whose inner surface has an axially uniform non-circular cross-sectional shape including a rotation inhibiting surface 3F. The inner cylinder 4 has a collar 7 on the outer peripheral surface which is guided and supported slidably by the intermediate portion of the outer cylinder and has a conforming non-circular cross-sectional shape including a flat surface 7B for sliding engagement with the rotation inhibiting surface 3F to inhibit rotation of the inner cylinder.

Abstract: The robot has upper (2) and lower (1) tables, linked by six linear actuators (3-8), forming a triangulation. The robot is controlled using an inverse mathematical model of its operation, with appropriate inputs. The inputs generate set values for length of each linear actuator to achieve required position and orientation of the upper table. Each linear actuator is fitted with an encoder measuring its extension. The position of the top table is measured using signals from six encoders attached to a telescopic rod (12) coupling the upper and lower tables. These encoders give measures of each of the six degrees of freedom of the robot, for comparison (38) with set values.

Abstract: A hydraulic device provided with a plurality of hydraulic actuators (12,13,14) directly connected to a hydraulic pump (1) for control. A hydraulic pump is operable in both rotational directions when the electric motor (6) is rotated forwards and in reverse. Ports (15-17,18-20) of each hydraulic actuator are connected via a connecting line in parallel with ports (2,4) of the hydraulic pump. A plurality of electromagnetic valves (22,23,24) are provided in the connecting lines to the hydraulic actuators. By opening or closing each electromagnetic valve, the operation of the associated hydraulic actuator is controlled. The operation direction of each hydraulic actuator is controlled by rotating the electric motor clockwise or counterclockwise. Further, a position sensor (36) is provided for detecting displacement of the specified hydraulic actuator and the electric motor is controlled based on a signal transmitted from the position sensor.

Abstract: A method and apparatus wherein a travel limit/dampening device is coupled to the end of a screw of a linear ball screw actuator device for limiting the travel of an actuator extension coupled to a nut supported for linear driven displacement in either direction along the screw. The travel limit/dampening device includes a gas shock supported within a double acting reaction device reactive axially between the nut and screw when the extension is fully retracted and extended, respectively, to collapse the shock absorber and thereby dampen the movement of the extension at each end of its stroke.

Abstract: In an electrically-operated disc brake assembly for vehicles, friction members 10, 11 are applied to a rotatable brake disc 4 by brake-applying means which includes an electric motor 6, gearbox 7, and a linear actuator 12 in the form of a screw device driven by the motor to apply an axially-directed brake-applying force to a piston 13 abutting the friction member via hydraulic fluid trapped within space 25. In operation, if the piston 13 has been moved relative to a "roll-back" seal 15 to accommodate wear of the friction member, the effective volume of space 25 will be increased on retraction of piston 16 of the screw device, thus allowing hydraulic fluid to flow into the space 25 from reservoir 28 via one-way valve 26. The gearbox 7 may be omitted, and the screw device may include ball or roller screws.

Abstract: To prevent a ball-threaded shaft from slipping out of a linear actuator, a linear actuator 10 has an output shaft 18 threaded in a nut 16 for moving forward and backward linearly with respect to an outer tube 22 secured to a housing 20. Linear reciprocating movement of the nut 16 is effected by a ball-threaded shaft 14 rotated normally and reversely by a driving motor 12. The shaft is held against axial displacement by a bearing assembly 8 having an axial disk 32 secured to a proximal end 24 of the ball-threaded shaft 14. On the nut side of the disk within the assembly are disposed a first tension receiving rotational body 36, a thrust bearing 45 and a second tension receiving rotational body 58. The assembly 8 is retained by a tension stopper 62 spread and inserted into an annular central groove 60 in the tube 22. The second tension receiving rotational body 58 is formed with a reduced diameter preventing circumferential surface 66 corresponding to an inner peripheral circumferential surface of the C-shaped tension stopper 62. Even if tension and a rotating force are exerted on the tension stopper 62, causing it to be reduced in diameter, the inner peripheral surface thereof comes into contact with the reduced diameter preventing surface 66.

Abstract: Evaluation of optimum pressing force, namely pre-load for a slider to obtain superior operation condition of a surface acoustic wave (SAW) motor is described. As a first experiment, we used steel balls for sliders. The steel balls that we used were 0.5, 1 and 2 mm diameter to change contact conditions such as contact pressure, contact area and deformation of the stator and the slider. As a result, the deformation of the stator and the slider by the pre-load should be half of the normal vibration amplitude. This condition was independent to the diameter of the balls. The maximum driving force was 0.95 mN and the driving force density was 50 N/mm/sup 2/. Secondly, in order to enlarge the contact area, multi contact points slider was made on trial. As a result, the driving force became 25 mN, 25 times as high as the first result, 0.95 mN. The SAW motor has high potential to be a large output force, quick response, long traveling distance and low in profile micro linear actuator.