Abstract: A piezoelectric-driven actuator based on coupling motion has been proposed and tested to achieve a large linear working stroke with high resolution. “Z-shaped” flexure hinges are exploited for the symmetric flexure hinge mechanism to reduce the structural stress. Coupling motion is obtained by placing this symmetric flexure hinge mechanism with an angle of $\theta =20^\circ $ to the slider. Experimental results indicate that linear motion with a large working stroke is effectively obtained by this coupling motion; the maximum motion speed is $V_{s}=$ 6057 μm/s and the maximum output force is $F_{g}=$ 350 g. Additionally, the influences of input frequency $f$ and input voltage $U_{e}$ are investigated, and the system kinetic model is established to better analyze the performance of this designed piezoelectric-driven linear actuator.

Abstract: Haptic interfaces are mechatronic devices designed to render tactile sensations; although they are typically based on robotic manipulators external to the human body, recently, interesting wearable solutions have been presented. Toward a more realistic feeling of virtual and remote environment interactions, we propose a novel wearable skin stretch device for the upper limb called “hBracelet.” It consists of two main parts coupled with a linear actuator. Each part contains two servo actuators that move a belt. The device is capable of providing distributed mechanotactile stimulation on the arm by controlling the tension and the distance of the two belts in contact with the skin. When the motors spin in opposite directions, the belt presses into the user's arm, while when they spin in the same direction, the belt applies a shear force to the skin. Moreover, the linear actuator exerts longitudinal cues on the arm by moving the two parts of the device. In this letter, we illustrate the mechanical structure, working principle, and control strategies of the proposed wearable haptic display. We also present a qualitative experiment in a teleoperation scenario as a case study to demonstrate the effectiveness of the proposed haptic interface and to show how a human can take advantage of multiple haptic stimuli provided at the same time and on the same body area. The results show that the device is capable of successfully providing information about forces acting at the remote site, thus, improving telepresence.

Abstract: We propose a micro linear ultrasonic motor, which is one of the smallest linear actuators that can generate practical force. Such a small actuation mechanism can be used for a wide range of applications, such as auto-focus systems used in thinner cell phones and smaller endoscopes. In this paper, we design the micro linear ultrasonic motor and evaluate the performance of the prototype motor. The size of the prototype stator with piezoelectric elements measures 2.6 mm in height, 2.6 mm in width, and 2.2 mm in depth (the length in slider travel direction). There is a hole of 1.4 mm in diameter at the stator center, and the slider inserted into the hole moves back and forth when voltages are applied to the piezoelectric elements. By optimizing the preload between the stator and slider experimentally, the motor thrust force has been improved to over 10 mN, which is a practical force for moving small objects. Experiments clarify the output characteristics in response to the input voltages. Finally, a maximum thrust force of 20 mN has been obtained at applied voltages with an amplitude of 150 V p−p .

Abstract: A magnetic screw is a new type of high force density linear actuator. One of the key challenges for realization of the magnetic screw concept is the manufacturing process of its helical permanent-magnet (PM) poles. Structure simplification and simple assembly process are essential in promoting the development of the magnetic screw. This paper studies several PM configurations employed to realize the magnetic screw and proposes a new structure, which can well approximate the helical magnetic poles in a very simple way. The electromagnetic performances are assessed analytically and by time-stepping finite-element analysis (FEA). Finally, both the analytical model and the FE results are validated by experiments based on a prototype machine.

Abstract: Modern industrial facilities, as well as vehicles and many other assets, are becoming highly automated and instrumented. As a consequence, actuators are required to perform a wide variety of tasks, often for linear motion. However, the use of tools to monitor the condition of linear actuators is not widely extended in industrial applications. This paper presents a data-based method to monitor linear electro-mechanical actuators. The proposed algorithm makes use of features extracted from electric current and position measurements, typically available from the controller, to detect and diagnose mechanical faults. The features are selected to characterize the system dynamics during transient and steady-state operation and are then combined to produce a condition indicator. The main advantage of this approach is the independence from a need for a physical model or additional sensors. The capabilities of the method are assessed using a novel experimental linear actuator test rig specially designed to recreate fault scenarios under different operating conditions.

Abstract: Despite offering many advantages over traditional rigid actuators, soft pneumatic actuators suffer from a lack of comprehensive, computationally efficient models and precise embedded control schemes without bulky flow-control valves and extensive computer hardware. In this article, we consider an inexpensive and reliable soft linear actuator, called the reverse pneumatic artificial muscle (rPAM), which consists of silicone rubber that is radially constrained by symmetrical double-helix threading. We describe analytical and numerical static models of this actuator, and compare their performance against experimental results. To study the application of rPAMs to operate underlying kinematic linkage skeletons, we consider a single degree-of-freedom revolute joint that is driven antagonistically by two of these actuators. An analytical model is then derived, and its accuracy in predicting the static joint angle as a function of input pressures is presented. Using this analytical model, we perform dynamic characterization of this system. Finally, we propose a sliding-mode controller, and a sliding mode controller augmented by a feed-forward term to modulate miniature solenoid valves that control air flow to each actuator. Experiments show that both controllers function well, while the feed-forward term improves the performance of the controller following dynamic trajectories.

Abstract: The tubular linear switched reluctance actuator (TLSRA) is presented in this paper to propel linear compressors with oscillatory motion. The proposed TLSRA possesses the advantages of higher force density and shorter magnetic flux paths in comparison with conventional LSRAs and are much more suitable for applications to reciprocating oscillation due to absence of any coils and magnets on the mover in comparison with linear actuators with moveable permanent magnets. The analytical expression of gap permeance is proposed for fast machine design and optimization. The designed thrust force characteristics are verified by finite-element analysis (FEA) and the experiment. The dynamic model of the linear compressor propelled by the proposed TLSRA is presented. The simulated and experimental results demonstrate that the developed TLSRA can be applied to linear oscillatory motion and that the developed linear compressor propelled by the proposed TLSRA is effective and feasible.

Abstract: High power-to-weight ratio soft artificial muscles are of overarching importance to enable inherently safer solutions to human–robot interaction. Traditional air-driven soft McKibben artificial muscles are linear actuators, and it is impossible for them to realize bending motions through use of a single muscle. More than two McKibben muscles are normally used to achieve bending or rotational motions, leading to heavier and larger systems. In addition, air-driven McKibben muscles are highly nonlinear in nature, making them difficult to be controlled precisely. An shape memory alloy (SMA)-fishing-line-McKibben (SFLM) bending actuator has been developed. This novel artificial actuator, made of an SMA-fishing-line muscle and a McKibben muscle, was able to produce the maximum output force of 3.0 N and the maximum bending angle (the rotation of the end face) of 61°. This may promote the application of individual McKibben muscles or SMA-fishing-line muscles alone. An output force control method for the SFLM is proposed, and based on MATLAB/Simulink software, an experiment platform is set up and the effectiveness of control system is verified through output force experiments. A three-fingered SFLM gripper driven by three SFLMs has been designed for a case study and for which the maximum carrying capacity is 650.4 ± 0.2 g.

Abstract: The future trend of mechanical systems is to substitute most of them by permanent magnet (PM) and/or electromagnetic based ones. This current research highlights a paradigm for future studies of the advanced direct-drivable safe and precise motion actuators, and headlines design, modeling, simulation, and implementation-based control of a novel RotLin (rotary–linear) radial gap helical machine. The machine is comprised of stator, midlayer rotor, and the inner layer translator. This is a hybrid of magnetic screw with a synchronous motor by modifying the design concept. Structurally, it is made using smartly piecewise helical-shaped PM that are radially magnetized, and helically layered on both rotor and translator. This machine has a wide range of applications, it can be used for linear actuation or for wave energy harvesting. The three-dimensional finite element analysis simulation results and calculations confirmed the realization of rotary and linear motions. To confirm this model, a prototype was enacted and experimental verifications of its performance in terms of direct-drive position and speed control were conducted. This compact machine can realize high thrust-force densities when used as a linear actuator.

Abstract: Force-controllable actuators are essential for guaranteeing safety in human–robot interactions. Magnetic lead screws (MLSs) transfer force without requiring contact between parts. These devices can drive the parts with high efficiency and no frictional contact, and they are force limited when overloaded. We have developed a novel MLS that does not include spiral permanent magnets and an MLS-driven linear actuator (MLSDLA) that uses this device. This simple structure reduces the overall size of the device and improves productivity because it is constructed by a commonly used machined screw as a screw. The actuator can drive back against an external force and it moves flexibly based on the magnetic spring effect. In this paper, we propose a force estimation method for the MLSDLA that does not require separate sensors. The magnetic phase difference, as measured from the angular and linear displacements of the actuator, is used for this calculation. The estimated force is then compared against measurements recorded with a load sensor in order to verify the effectiveness of the proposed method.

Abstract: Dielectric elastomers (DE), known as electromechanical transducers, have been widely used in the field of sensors, generators, actuators and energy harvesting for decades. A large number of DE actuators including bending actuators, linear actuators and rotational actuators have been designed utilizing an experience design method. This paper proposes a new method for the design of DE actuators by using a topology optimization method based on pairs of curves. First, theoretical modeling and optimization design are discussed, after which a rotary dielectric elastomer actuator has been designed using this optimization method. Finally, experiments and comparisons between several DE actuators have been made to verify the optimized result.

Abstract: This paper presents the multiphysics optimization of a new class of nanopositioning actuators, termed as flexure-based electromagnetic linear actuator (FELA). The optimization is carried out analytically based on the derived closed-form magnetic field, force, and thermal models, while its objectives include the maximizing of force generation and minimizing of thermal generation, which are both crucial for the nanopositioning actuators. The optimization results show that the new version of FELA achieved 67.3% improvement in force generation for certain current and 46.2% thermal reduction for certain output force, compared to the previous version of FELA with the same size, which was optimized using the numerical methods. The optimization results are also validated by the experiments of the new version FELA prototype, where 56.2% improvement in current–force sensitivity and 43% above reduction in thermal power are demonstrated experimentally. Furthermore, by utilizing the established modeling framework, several fundamental questions on the design of FELA are answered theoretically in this paper, such as the effect about the uniform and radial magnetization of the permanent magnet and the performance tradeoff between the different number of magnet segments.

Abstract: In surgical procedures such as brachytherapy, biopsies and drainages, how to precisely place the needle inside the body is crucial for the performance of such surgeries. In last two decades, robot-aided needle placement has gradually been a trend for better security and accuracy. However, existing successful medical robot systems leave some common drawbacks: expensive, bulky, and high operation complexity, which motivates the development of more compact, affordable, and functional robots. This paper introduces a novel robot based on a 2-CRRR-CRR parallel manipulator (PM) for single needle insertion with high accuracy, where C denotes a cylindrical joint and R a revolute joint. Via screw theory, the mobility of the robot is analyzed, which meets the requirement of remote-center-of-motion (RCM). Its kinematic analysis is presented and singular configurations are identified based on the Jacobian matrix. Furthermore, the link dimensions of the robot are optimized by considering motion/force transmissibility and practical limits to generate singularity-free and high-performance workspace around the incision point. The design and feasibility of the proposed robot are validated by preliminary motion experiments with a prototype. The two advantages of the proposed robot are a singularity-free workspace with good motion/force transmissibility and high rigidity due to three fixed linear actuators in parallel architecture.

Abstract: Although 3D printing has the potential to provide greater customization and to reduce the costs of creating actuators for industrial applications, the 3D printing of actuators is still a relatively new concept. We have developed a pneumatic actuator with 3D-printed parts and placed sensors for position and force control. So far, 3D printing has been used to create pneumatic actuators of the bellows type, thus having a limited travel distance, utilizing low pressures for actuation and being capable of only limited force production and response rates. In contrast, our actuator is linear with a large travel distance and operating at a relatively higher pressure, thus providing great forces and response rates, and this the main novelty of the work. We demonstrate solutions to key challenges that arise during the design and fabrication of 3D-printed linear actuators. These include: (1) the strategic use of metallic parts in high stress areas (i.e., the piston rod); (2) post-processing of the inner surface of the cylinder for smooth finish; (3) piston head design and seal placement for strong and leak-proof action; and (4) sensor choice and placement for position and force control. A permanent magnet placed in the piston head is detected using Hall effect sensors placed along the length of the cylinder to measure the position, and pressure sensors placed at the supply ports were used for force measurement. We demonstrate the actuator performing position, force and impedance control. Our work has the potential to open new avenues for creating less expensive, customizable and capable actuators for industrial and other applications.

Abstract: We demonstrate thin-film repulsive-force electrostatic actuators that employ a new electrode pattern and are useful for low-force actuation applications. Compared to prior patterns, the new electrode geometry increases electrostatic force production by an order of magnitude (at equal voltages) and eliminates the most common shorting failure modes. These electrostatic actuators have stable open-loop operation with no pull-in instability, low mechanical hysteresis, and peak force in rest configurations. The actuators are fabricated with a planar, flex-circuit manufacturing process, allowing production at scale and over large areas. Two-layer out-of-plane linear actuators (25 × 10 mm electrode area) were characterized: with 0–1000 V inputs (40 × 106 V/m), blocked normal forces of 9.03 mN (36.1 Pa) were generated, and controllable linear displacements up to 511 μm were measured across an open loop bandwidth of 43 Hz. Finally, we present a 290 mg 1-DoF micro-mirror system for laser beam steering that employs a two-layer out-of-plane rotational actuator for open-loop stable operation with controlled angular displacements up to 5.1° at 1000 V/16 Hz.

Abstract: Electromagnetic design of a moving magnet frictionless linear actuator with self-holding functionality for mechanical gear shifting in a transmission application is presented. The actuator consists of a tubular magnetic circuit with stationary armature and axially moving rotating permanent magnet assembly with radial magnetisation in the air gap. The armature contains a two-piece magnetic core with a space for a winding. The effects of armature slot opening and magnetic circuit materials on the self-holding force and the acting force are studied in the whole moving range. The designed moving magnet linear actuator improves the performance of the vehicle by enabling shift times below 50 ms with no energy consumption between the shifts.

Abstract: A new 2R1T (R: rotation, T: translation) parallel manipulator (PM), called Tex3, is proposed. The Tex3 PM is a 2PUR-PRU PM consisting of 9 joints with 12 DOFs (degrees of freedom), and can be actuated by fixed linear actuators. Mobility analysis shows that it is an RPR-equivalent PM whose finite motion is the product of a rotation (R) followed by a translation (P) and another rotation (R). Inverse position and velocity analyses are discussed. Furthermore, the local transmission index and good transmission workspace are used to evaluate the motion/force transmissibility of the proposed PM. The singularity loci of the proposed PM are obtained according to the motion/force transmissibility, corresponding to the inverse, forward and combined kinematic singularity. The constraint singularity is also discussed. Finally, link parameters are optimized to obtain an improved good transmission workspace. Because of its minimum DOF of joints and fixed linear actuators, the Tex3 PM has good kinematic performance and is suited to the high-speed machining of workpieces with curved surfaces.

Abstract: This paper investigates a novel miniature-size resonant moving-magnet linear actuator designs to be used in miniature linear compressor applications. The miniature linear actuator has a slotless stator and a tubular topology. It utilizes moving magnets in which the magnets are lined up in the Halbach array structure. Finite-element and analytical analyses of the actuator are performed to determine the flux density and thrust force. Experimental thrust force behavior at the resonant frequency is determined. It is shown that the finite-element method simulation, analytical, and experimental results agree with each other.

Abstract: Autonomous deployment and shape reconfiguration of structures is a crucial field of research in space exploration with emerging applications in the automotive, building and biomedical industries Challenges in achieving autonomy include: bulky energy sources, imprecise deployment, jamming of components and lack of structural integrity Leveraging advances in the fields of shape memory polymers, bistability and 3D multi-material printing, we present a 3D printed programmable actuator that enables the autonomous deployment and shape reconfiguration of structures activated though surrounding temperature change Using a shape memory polymer as the temperature controllable energy source and a bistable mechanism as the linear actuator and force amplifier, the structures achieve precise geometric activation and quantifiable load bearing capacity The proposed unit actuator integrates these two components and is designed to be assembled into larger deployable and shape reconfigurable structures First, we demonstrate that the activation of the unit actuator can be sequenced by tailoring each shape memory polymer to a different activation time Next, by changing the configuration of the actuator, we demonstrate an initially flat surface that transforms into a pyramid or a hyperbolic paraboloid, thus demonstrating a multi-state structure Load bearing capability is demonstrated for both during activation and in the operating state

Abstract: Efficient actuation is an important requirement in electromechanical designs. Although hydraulic actuators are used extensively when high-magnitude forces are present in heavy machinery, they are n...

Abstract: Wireless actuation by magnetic fields allows for the operation of untethered miniaturized devices, e.g. in biomedical applications. Nevertheless, generating large controlled forces over relatively large distances is challenging. Magnetic torques are easier to generate and control, but they are not always suitable for the tasks at hand. Moreover, strong magnetic fields are required to generate a sufficient torque, which are difficult to achieve with electromagnets. Here, we demonstrate a soft miniaturized actuator that transforms an externally applied magnetic torque into a controlled linear force. We report the design, fabrication and characterization of both the actuator and the magnetic field generator. We show that the magnet assembly, which is based on a set of rotating permanent magnets, can generate strong controlled oscillating fields over a relatively large workspace. The actuator, which is 3D-printed, can lift a load of more than 40 times its weight. Finally, we show that the actuator can be further miniaturized, paving the way towards strong, wirelessly powered microactuators.

Abstract: Stepper motor is a common linear actuator in automation This motor is used in the design of one axis automated cutter motion control with a linear slide The cutter required a high precision motion and location control to avoid miss-cut condition With the advantage of parallelism of FPGA, a precise stepper motor control signal is generated to drive the stepper motor Concurrent logic circuit in FPGA calculated the distance and direction of motion in synchronize mode Trapezoidal velocity profile and motion control are implemented using finite state machine (FSM) in FPGA The distance resolution per step achieved in this study is 1588µm for 8-microstep configuration The FPGA stepper motor controller consumes only 1 % logic source on Altera DE2 FPGA board

Abstract: Soft robotic actuators are well suited for use in exoskeleton applications due to their innate compliance and low weight. We have developed a wearable soft robotic sleeve that uses fiber reinforced elastomeric enclosures (FREEs) to provide actuation and stiffness at the elbow for augmented lifting and carrying ability. The sleeve includes novel linear and helical actuator architectures to induce and resist joint movement respectively, and is intended to be comfortable, lightweight, and low profile. We developed test protocols to measure actuation and stiffness performance of different helical and linear architectures, and to compare helical and linear actuator groups when used individually and together. Our findings indicate that nested linear actuators have superior contraction ratios compared to parallel linear actuators, resulting in greater angular displacement. Stiffness from helical actuators increased with pressure and number of parallel actuators. A combined linear-helical actuator configuration considerably outperformed helical and linear actuator groups when used on their own.

Abstract: The direct kinematics problem of parallel mechanisms, that is, determining the pose of the manipulator platform from the linear actuators’ lengths, is, in general, uniquely not solvable. For this reason, instead of measuring the lengths of the linear actuators, we propose measuring their orientations and, in most cases, also the orientation of the manipulator platform. This allows the design of a low-cost sensor system for parallel mechanisms that completely renounces length measurements and provides a unique solution of their direct kinematics.

Abstract: The Large Synoptic Survey Telescope 1 (LSST) is an altitude-azimuth mounted three mirror telescope and camera. The primary (M1) and tertiary (M3) mirrors are integrated into a single, monolithic borosilicate substrate 8.42 m diameter. The annular secondary (M2) mirror is located above the M1M3 mirror and the camera is nested inside the M2. The M1M3 mirror is supported on a mirror cell by two independent systems: one system is for Active Mode and the other for Static Mode. During observing, or Active Mode 2 , the M1M3 mirror is supported by an array of 156 support and figure control actuators consisting of 268 pneumatic cylinders that react to gravity and inertial loads and provide figure error correction. Load cells on the actuators measure forces that are communicated to the M1M3 control system. However, the figure actuators do not define the mirror position. This is defined with six axially stiff linear actuators called hardpoints 3 arranged in a hexapod pattern to restrain rigid body motion of the mirror in a kinematic fashion. By adjusting the length of each hardpoint, the mirror can be adjusted in all six degrees of freedom with respect to the cell. Displacement sensors and load cells on the hardpoints communicate displacements and forces to the control system, which processes the telemetry and issues force corrections to the figure actuators to zero out any loads and moments on the hardpoints. In Static Mode, the M1M3 mirror is no longer supported by figure actuators and the position sensing of the hard point hexapod is inactive. A second support system consisting of 288 wire rope isolators called Static Supports come into play. The static supports mechanically capture the mirror whether in Active or Static Mode and in the event the mirror experiences motion beyond the active motion range in any direction. The static supports also safely support the mirror during seismic events for all elevation angles. In active mode, the static supports do not contact the mirror and thus, do not affect the mirror positioning or figure. This paper focuses on the detailed design, development, testing, integration, and current status of the M1M3 pneumatic figure actuators.

Abstract: Design of a mini prototype wave energy converter (WEC) system is considered in this paper. The prototype is based on permanent magnet linear generator (PMLG) with planar structure. The main objective of this work is to create a simple and low cost prototype of WEC system for study and teaching purposes. In the design procedure, optimization of the detailed parameters to obtain the output power with the barrier of physical dimensions is considered. The PMLG is combined with a linear actuator based on DC motor, sensors and data acquisition devices to represent a WEC system. The experimental test is performed to investigate the efficiency of the designed PMLG.

Abstract: Overrunning, non-friction coupling and control assemblies, a switchable linear actuator device and a reciprocating electromechanical apparatus for use in the assemblies are provided. The device and apparatus control the operating mode of at least one non-friction coupling assembly. The device and apparatus have 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. One or more cams are utilized to control whether a locking member either couples or uncouples its corresponding coupling assembly.