Abstract: An electric linear actuator has a housing, an electric motor mounted on the housing, a speed reduction mechanism, and a ball screw mechanism. The ball screw mechanism has a nut and screw shaft. Both have helical screw grooves. The screw shaft is inserted into the nut, via a large number of balls. A sleeve is secured on the housing to prevent rotation of the screw shaft relative to the housing. At least one axially extending recessed groove is formed on the inner circumference of the sleeve. At least one guide pin, mounted on the end of the screw shaft, engages the recessed groove. A tapering chamfered portion is formed on the end of the nut.

Abstract: Moving magnet actuators (MMAs) are direct-drive, single-phase electromagnetic linear actuators that provide frictionless and backlash-free motion over a range of several millimeters. This paper investigates the feasibility of using MMAs to simultaneously achieve large range, high speed, and high motion quality in flexure-based nanopositioning systems. Component and system level design challenges and associated tradeoffs in meeting the aforementioned nanopositioning performance are discussed and derived. In particular, it is shown that even as the overall size of a traditional MMA is varied, the actuation force remains directly proportional to the square root of the actuator's moving magnet mass and the square root of power consumed. This proportionality constant, identified as the dynamic actuator constant, serves as a figure of merit for MMAs. When an MMA is employed in a flexure-based nanopositioning system, this constant directly impacts the system-level positioning performance in terms of range, resolution, speed, and temperature rise. This quantitative determination highlights the significance of incorporating a thermal management system for heat dissipation, minimizing noise and harmonic distortion in the current driver, and improving the force-stroke uniformity of the actuator. Based on this understanding, a single-axis nanopositioning system, which simultaneously achieves 10 mm range, 4 nm resolution, open-loop natural frequency of 25 Hz, and temperature rise of less than 0.5 °C, is designed, fabricated, and tested. Preliminary controller design and closed-loop operation highlight the potential and limitations of MMAs in large-range, high-speed nanopositioning.

Abstract: A robotic submersible includes a housing having a body and a tail In another aspect, a pump and a pump tank adjust the buoyancy of a submersible housing In a further aspect, a first linear actuator controls the pump and/or a buoyancy, and/or a second linear actuator controls a position of a battery and/or adjusts a center of gravity Another aspect includes a pump and at least one linear actuator that control gliding movements of the housing In still a further aspect, a motor couples a tail with a body, such that the motor controls the movements of the tail to create a swimming movement Moreover, an additional aspect provides a controller selectively operating the pump, first actuator, second actuator, and motor to control when swimming and gliding movements occur

Abstract: Various embodiments related to hydraulic actuators and active suspension systems as well as their methods of use are described.

Abstract: Series Elastic Actuators (SEAs) have several benefits for force controlled robotic applications. Typical SEAs place an elastic element between the motor and the load, increasing shock tolerance, allowing for more accurate and stable force control, and creating the potential for energy storage. This paper presents the design of a compact, lightweight, low-friction, electromechanical linear SEA used in the lower body of the Tactical Hazardous Operations Robot (THOR). The THOR SEA is an evolutionary improvement upon the SAFFiR SEA [1]. Design changes focused on reducing the size and fixed length of the actuator while increasing its load capacity. This SEA pairs a ball screw-driven linear actuator with a configurable elastic member. The elastic element is a titanium leaf spring with a removable pivot, setting the compliance to either 650 or 372 [kN/m]. The compliant beam is positioned parallel to the actuator, reducing overall packaging size by relocating the space required for spring deflection. Unlike typical SEAs which measure force through spring deflection, the force applied to the titanium beam is measured through a tension/compression load cell located in line with each actuator, resulting in a measurable load range of +/−2225 [N] at a tolerance of +/−1 [N]. A pair of universal joints connects the actuator to the compliant beam and to the robot frame. As the size of each universal joint is greatly dependent upon its required range of motion, each joint design is tailored to fit a particular angle range to further reduce packaging size. Potential research topics involving the actuator are proposed for future work.Copyright © 2014 by ASME

Abstract: Dual-range stages are demanded in precision positioning applications that call for fine resolution in a smaller motion range and coarse resolution in a larger range. Traditional dual-range stages are realized using two actuators, which complicates the mechanism and control design procedures. This paper presents the design and testing of a novel dual-range, dual-resolution precision positioning stage driven by a single linear actuator. The stage structure is devised with leaf flexures to achieve a large stroke. Strain sensors are employed to provide different resolutions in the two motion ranges. To quantify the design of the motion ranges and fine/coarse resolution ratio, analytical models are established and verified through finite element analysis simulations. A proof-of-concept prototype is fabricated for experimental investigations and the experimental results validate the effectiveness of the proposed design. The reported ideas can also be extended to the design of multi-axis micropositioning stages.

Abstract: For a humanoid robot to have the versatility of humans, it needs to have similar motion capabilities. This paper presents the design of the hip joint of the Tactical Hazardous Operations Robot (THOR), which was created to perform disaster response duties in human-structured environments. The lower body of THOR was designed to have a similar range of motion to the average human. To accommodate the large range of motion requirements of the hip, it was divided into a parallel-actuated universal joint and a linkage-driven pin joint. The yaw and roll degrees of freedom are driven cooperatively by a pair of parallel series elastic linear actuators to provide high joint torques and low leg inertia. In yaw, the left hip can produce a peak of 115.02 [Nm] of torque with a range of motion of −20° to 45°. In roll, it can produce a peak of 174.72 [Nm] of torque with a range of motion of −30° to 45°. The pitch degree of freedom uses a Hoeken’s linkage mechanism to produce 100 [Nm] of torque with a range of motion of −120° to 30°.Copyright © 2014 by ASME

Abstract: The present invention relates to a height-adjustable table (1) height-adjusting arrangement (100) for adjusting the height of the table (1), wherein the height-adjusting arrangement (100) comprises at least one leg, each leg having an inner tubular member (112) and an outer tubular member (113) arranged for telescopic movement relative to each other, and a linear actuator (114) coupled to said tubular members (112, 113) and which is configured to provide the telescopic movement between the tubular members (112, 113), and an electric motor connected to the linear actuator (114) and configured to operate the linear actuator for providing telescopic movement between the tubular members. The height-adjusting arrangement (100) further comprises an eye detection unit arranged to detect the position of a user's eyes. The height-adjusting arrangement (100) is configured for control of the height of the height-adjustable table (1) based on the detected position of a user's eyes.

Abstract: This paper introduces an impact drive mechanism (IDM) that utilizes the rapid contraction property of shape memory alloy (SMA) wire. In this study, possible structures for an SMA-wire-based IDM actuator are investigated, and a prototype actuator comprising a main body, an inertia body, an SMA wire, and a bias spring is developed. To verify the applicability of the prototype actuator as a positioning device, driving experiments were conducted under various conditions. The experimental results demonstrated that the prototype actuator enables bidirectional step-like movement with several step sizes by changing the profile of applied voltage, such as amplitude, duty cycle, and frequency. In addition, we developed PI-controller-based position control systems by using these three parameters as control input; the control characteristics and potential applications of each method were discussed. These results implied that the SMA-wire-based IDM actuator has the potential to be used as a new linear actuator in sub-millimeter order driving.

Abstract: An active suspension system is configured in a strut arrangement. The active suspension system comprises a hydraulic actuator and a hydraulic pump/electric motor assembly, wherein the actuator movement is preferably in lockstep with the hydraulic motor-pump and electric motor-generator combination. Torque in the electric motor is instantaneously controlled by a controller to create an immediate force change on the hydraulic actuator. The hydraulic actuator is configured so that it can be used as a strut whereby the actuator has sufficient structural rigidity to carry the applied suspension loads while capable of supplying damper forces in at least three quadrants of the force velocity graph of the suspension actuator operation. Embodiments disclosed include low cost active suspension systems for a MacPherson strut application.

Abstract: An electronic, high-efficiency vehicular transmission, an overrunning, non-friction coupling and control assembly and switchable linear actuator device for use in the assembly and the transmission are provided. The device controls the operating mode of at least one non-friction coupling assembly. The device has a plurality of magnetic sources which produce corresponding magnetic fields to create a net translational force. The net translational force comprises a first translational force caused by energization of at least one electromagnetic source and a magnetic latching force based upon linear position of a permanent magnet source along an axis.

Abstract: A portable container lift or weighing system includes lifting units, each including a hydraulic linear actuator and a mounting arrangement for mounting the actuator to a shipping container. The system includes a number of portable components, that can be handled by a single worker. The system may provide a means for weighing the container.

Abstract: This paper proposes position and force control of a screw motor with power-saving axial-gap displacement adjustment. The motor has a helical-shape mover, which moves in a helical-shape stator without contact. Due to the fabrication process, the actual helical shapes of the mover and the stator are not completely uniform, and the air-gap length between the mover and the stator slightly changes, depending on the mover rotation angle. The d-axis current remains a finite value, and copper loss arises even when the mover is located at the center between the stator cores. A power-saving axial-gap displacement adjustment method is proposed to solve this problem. The proposed control is experimentally verified.

Abstract: Device and apparatus for controlling the operating mode of a coupling assembly, coupling and control assembly and electric motor disconnect and pass through assemblies are provided. The device is a switchable linear actuator device to control the operating mode of a coupling assembly. A plurality of magnetic sources produce corresponding magnetic fields to create a net translational force. A stator structure includes at least one electromagnetic source and a translator structure includes a permanent magnet source magnetically coupled to the stator structure across a radial air gap. The translator structure is supported for translational movement relative to the stator structure along an axis between first and second stable axial end positions which correspond to first and second operating modes of the coupling assembly and an unstable axial equilibrium position between the end positions. The translator structure translates along the axis between the different positions upon experiencing the net translational force.

Abstract: Synopsis Trotting, bipedal running, and especially hopping have long been considered the principal bouncing gaits of legged animals. We use the radial-leg spring constant krad to quantify the stiffness of the physical leg during bouncing gaits. The radial-leg is modeled as an extensible strut between the hip and the ground and krad is determined from the force and deflection of this strut in each instance of stance. A Hookean spring is modeled in-series with a linear actuator and the stiffness of this spring krad is determined by minimizing the work of the actuator while reproducing the measured force-deflection dynamics of an individual leg during trotting or running, and of the paired legs during hopping. Prior studies have estimated leg stiffness using kleg, a metric that imagines a virtual-leg connected to the center of mass. While kleg has been applied extensively in human and comparative biomechanics, we show that krad more accurately models the spring in the leg when actuation is allowed, as is the case in biological and robotic systems. Our allometric analysis of krad in the kangaroo rat, tammar wallaby, dog, goat, and human during hopping, trotting, or running show that krad scales as body mass to the two-third power, which is consistent with the predictions of dynamic similarity and with the scaling of kleg. Hence, two-third scaling of locomotor spring constants among mammals is supported by both the radial-leg and virtual-leg models, yet the scaling of krad emerges from work-minimization in the radial-leg model instead of being a defacto result of the ratio of force to length used to compute kleg. Another key distinction between the virtual-leg and radial-leg is that krad is substantially greater than kleg, as indicated by a 30–37% greater scaling coefficient for krad. We also show that the legs of goats are on average twice as stiff as those of dogs of the same mass and that goats increase the stiffness of their legs, in part, by more nearly aligning their distal limb-joints with the ground reaction force vector. This study is the first allometric analysis of leg spring constants in two decades. By means of an independent model, our findings reinforce the two-third scaling of spring constants with body mass, while showing that springs in-series with actuators are stiffer than those predicted by energy-conservative models of the leg.

Abstract: Many robotic joints powered by linear actuators suffer from a loss of torque towards the limits of the range of motion. This paper presents the design of a fully backdriveable, force controllable rotary actuator package employed on the Tactical Hazardous Operations Robot (THOR). The assembly pairs a ball screw-driven linear Series Elastic Actuator (SEA) with a planar straight line mechanism. The mechanism is a novel inversion of a Hoeken’s four-bar linkage, using the ball screw as a linear input to actuate the rotary joint. Link length ratios of the straight line mechanism have been chosen to optimize constant angular velocity, resulting in a nearly constant mechanical advantage and peak torque of 115 [Nm] throughout the 150° range of motion. Robust force control is accomplished through means of a lookup table, which is accurate to within ±0.62% of the nominal torque profile for any load case.Copyright © 2014 by ASME

Abstract: The deformable fluid actuators available on the market, i.e. pneumatic muscles and pneumatic springs, are designed to mainly exert compressive or tensile forces. This paper deals with a novel fluid deformable actuator, with three membranes, called BiFAc3, whose particular feature is the ability to exert both tensile and compressive forces. The structure of the actuator is based on three cylindrical coaxial nonisotropic membranes connected to two end plates, whose original shape allows the independent supply of the three internal chambers. The first part of the paper deals with the internal structure and the geometry of the actuator, describes the operating principle and presents a prototype. The second part presents a modelling methodology that can be used to design and analyse the actuator in dynamic applications. The mathematical model of the actuator is based on three different levels of complexity which correspond to three consecutive design stages. The model has been experimentally validated: it is a...

Abstract: A fault-tolerant machine used for safety-critical tasks must a) guarantee at least a reduced-performance operation in case of partial machine fault and b) guarantee avoidance of drive mechanical jam/stall in case of total machine fault, to allow for the intervention of the back-up systems. Classical hydrostatic transmissions used on board ships for critical tasks such as rudder and stabilizing fin steering gears fulfill both the requirements a), b) above, but recent proposals for substitution with full-electric drives (rotary motors coupled with multistage reduction gears) usually do not. Especially the requirement b) needs particular attention and increased complexity when dealing with geared drives. This paper proposes a linear permanent-magnet direct drive fulfilling both the requirements above, for (but not limited to) rudder/fin steering gears. The absence of gears grants the requirement b), whereas the full-modular structure satisfies a), with independently fed stator modules and multiple inverters. This paper addresses some fault scenarios including electrical failures, in the machine winding (short-circuited coils) and in the inverters (trip of one or more units). The performance degradation is studied and assessed for the cases considered by both simulations and measurements on a prototype.

Abstract: A new rotary normal stress electromagnetic actuator for fast steering mirror (FSM) is presented. The study includes concept design, actuating torque modeling, actuator design, and validation with numerical simulation. To achieve an FSM with compact structure and high bandwidth, the actuator is designed with a cross armature magnetic topology. By introducing bias flux generated by four permanent magnets (PMs), the actuator has high-force density similar to a solenoid but also has essentially linear characteristics similar to a voice coil actuator, leading to a simply control algorithm. The actuating torque output is a linear function of both driving current and rotation angle and is formulated with equivalent magnetic circuit method. To improve modeling accuracy, both the PM flux and coil flux leakages are taken into consideration through finite element simulation. Based on the established actuator model, optimal design of the actuator is presented to meet the requirement of our FSM. Numerical simulation is then presented to validate the concept design, established actuator model, and designed actuator. It is shown that the calculated results are in a good agreement with the simulation results.

Abstract: The present disclosure is directed to recumbent exercise machines and associated systems and methods. In one embodiment, for example, a recumbent exercise apparatus can include a seat, two linear guide tracks forward of the seat, and two pedal assemblies movably coupled to corresponding linear guide tracks positioned forward of the seat. The pedal assemblies can be configured to move back and forth along the linear guide tracks. The recumbent exercise apparatus can further include linear actuators operably coupled to each of the linear guide tracks and configured to move the linear guide tracks up and down in a vertical direction. The pedal assemblies can be configured to move in elliptical patterns when the pedal assemblies move back and forth along the linear guide tracks and the linear actuators move the linear guide tracks up and down.

Abstract: Described herein are systems and devices for counterbalancing a surgical robotic system using a counterbalanced Z-axis drive. The counterbalanced Z-axis drive includes a self-centering ball screw assembly having a linear actuator and a counter weight. The counter weight is configured to substantially support a load associated with an arm of the robotic system when the driving portion is engaged or disengaged. In some embodiments, the counterbalanced Z-axis drive controls the arm and a movable effector mounted on the arm. Also disclosed herein are systems and devices for direct drive actuation of rotary axes of the arm which reduce the size and weight of the arm.

Abstract: This research investigated the magnetic and mechanical characteristics of a linear actuator by using structural and magnetic finite element analyses as well as experimental verification. The response time to reach the steady state of vibration was investigated through the equivalent mass---spring---damper system of the linear actuator. The response time can be reduced by increasing the magnetic force or by decreasing the mass. In the case of decreasing the mass, the spring constant should also be decreased in order to maintain the same natural frequency. However, reduction of both the mass and stiffness decreases the vibration magnitude because it is proportional to the spring constant. The results show that the ideal method to reduce response time without decreasing vibration magnitude is to increase magnetic force. Finally, this research proposes a novel design of a linear actuator with a large magnetic force to reduce the response time.

Abstract: Deep-sea master-slave hydraulic manipulator is among most commonly tools equipped on remotely-operated vehicles or human occupied vehicles. The design and realization of a 7-Function master-slave hydraulic manipulator can be used in 7000 meters depth is proposed. Linear actuator, rotary actuator and cycloid motor are the three basic modules of the slave arm. A double-screw-pair swing rotary actuator is designed as the rotary actuator, which realized rotary driving, multi-path oil and electric cable passing through and rotary angle measuring. Based on the reliable running experiments on land, a pressure experiment system to test the manipulator's index of 7000m depth is proposed. In the experiment system, the master controller with the whole system's power supply and experiment monitor are placed outside of the pressure cabin. And the slave arm, slave controller, hydraulic system, underwater light and cameras are inside the cabin. The pressure experimenting process is described in detail. Also, during the exciting experiment, some abjective things were also present, such as the rotary actuator rotating slow even stop rotating in high pressure environment. Complementary experiments aiming at problem arose in the whole system testing had to be done lately. The whole system's and complementary experiment show that the manipulator satisfy 7000m design depth index.

Abstract: A linear actuator includes a gearbox, a motor structure, a lead screw, a telescopic tube, a quick release mechanism and a buffer mechanism. The motor structure is connected to the gearbox. The lead screw has a part inside the gearbox and the other part outside. The telescopic tube has a nut screwed with the lead screw. The quick release mechanism inside the gearbox is coupled to a cylindrical coupling member and a worm gear. The cylindrical coupling member is rotated with the lead screw, and the worm gear is driven by the motor structure to clutch the cylindrical coupling member. The buffer mechanism is installed at the external periphery of the lead screw and between the nut and gearbox for absorbing impact forces.

Abstract: By wire technology is recently developed to improve the reliability, safety, and performance of vehicular drive technology. Brake system is the most important control system for vehicle safety. By wire technology development has encouraged the development of brake by wire systems to reduce traditional mechanical and hydraulic systems usage in automobiles. This paper proposes a novel brake by wire controller that uses a reaction force based bilateral motor controlling method. The proposed system uses two linear actuators with disturbance observer and reaction force observers to provide pedal force amplification and pedal retraction capabilities. The system includes a force controller to provide pedal feel to drivers. Electro mechanical brake position control is used to provide the brake force. The proposed system is simulated for different conditions to measure the performance and robustness. The simulation results provide evidence for robustness, force amplification, and pedal and brake retraction capabilities of the system.

Abstract: A fluid control system for delivery of a liquid includes a pneumatic drive that incorporates a linear actuator to effect known volume changes in a gas reservoir. The gas reservoir is in fluid communication with a gas-side reservoir that is separated from a fluid-side reservoir by a flexible membrane. Movement of the linear actuator effects positive or negative volume differences on the gas in the gas-side reservoir, resulting in a decrease or increase in pressure of the gas that is transmitted to the fluid-side reservoir to draw fluid, primarily liquid, in from a source or deliver liquid out to a sink. In another aspect, a mechanism is provided for the detection and elimination of air bubbles in the fluid path.