Large Output Force Research Articles

Polymer actuators of fluorene derivatives with enhanced inner channels and mechanical performance

A novel ion-exchange polymer-metal composite (IPMC) actuator is fabricated by sandwiching sulfonated fluorene blocked polysulfone (SDPF-b-PSU) between two Pt nanograin sheets. With increased concentration of chlorosulfonic acid, the SDPF-b-PSU film with more sulfonic groups exhibits strong ion exchange capacity, high Li+ ion conductivity, and ordered phase separation, which may contain an increased number of cations and possess larger and better interconnected inner channels for ion migration, thus providing the power to produce large force and power outputs. The SDPF-b-PSU film also exhibits enhanced mechanical performance and water uptake when compared to the pure Nafion film, providing a strong, hydrated matrix to support IPMC functions. At the driving voltage of 4V, the SDPF-b-PSU actuator exhibits a strong force output which is 11 folds higher than that of the pure Nafion actuator.

Structure and control strategy for a piezoelectric inchworm actuator equipped with MEMS ridges

Compared with conventional piezoelectric inchworm actuators (PIAs), which rely on a frictional mechanism to produce large stroke and force outputs, PIAs equipped with MEMS ridges can achieve much higher power density in small geometries through the interlocking of micro-ridges. This is promising for future adaptive space structure applications. However, from a practical perspective, achieving stable interlocking MEMS ridges remains challenging, and so an accurate structural assembly and effective control strategy are required. This paper presents an actuator with a simple structure, thus simplifying the assembly process and reducing assembly errors, and then designs a reasonable control strategy that compensates for hysteresis and the uncertain compression of the structure induced by acting against external loads of different stiffness. Finally, the stable interlocking of MEMS ridges is experimentally validated by measuring the significant improvement in PIA load capacity.

Adaptive control of hydraulic position servo system using output feedback

Due to the properties such as small size-to-power ratio, large force output capability and fast response, the hydraulic position servo system is widely used in industrial automation fields. High-pr...

Electromagnetic and Thermal Analyses of High-Performance Magnetic Shape Memory Actuators for Valve Applications

Magnetic shape memory (MSM) alloys are relatively new smart alloys, which have enormous potential to be used in actuators, sensors, and other electrical devices. Their large strain and considerable stress output can be controlled by magnetic fields or mechanical stresses. Maximum magnetic field-induced strain varies from 6% to 12% of the MSM element’s length depending on its microstructure. However, very low operational temperature limit is one of the main drawbacks of conventional MSM alloys. This makes their application in high-performance actuators challenging due to considerable power losses. This paper discusses different MSM actuator designs, optimized particularly for large force output for pneumatic electromagnetic valve applications. The thermal problem is addressed through analyzing the heat transfer conditions of each particular design and the effects of different cooling systems. An energy-efficient operating cycle for varying actuator loads that takes advantage of the shape memory effect is also proposed. This allows the minimization of energy losses, resulting in an acceptable increase in the temperature ensuring stable continuous actuation.

Design of a MEMS-based motion stage based on a lever mechanism for generating large displacements and forces

Conventional miniaturized motion stages have a volume of 50–60 cm3 and a range of motion around 100 μm. Micro-electro-mechanical systems (MEMS)-based motion stages have been good alternatives in some applications for small footprint, micron-level accuracy, and a lower cost. However, existing MEMS-based motion stages are able to provide a force of μN level, small displacements (less than tens of microns), and need additional features for practical applications like a probe or a stage. In this paper, a single degree of freedom motion stage is designed and analyzed for a larger displacement, a larger output force, a smaller out-of-plane deformation, and a bigger moving stage for further applications. For these purposes, the presented motion stage is designed with a thermal actuator, folded springs, and a lever, and it is experimentally characterized. Furthermore, three different types of flexure joints are investigated to characterize their capabilities and suitability to serve as the revolute joint of the lever: a beam, a cartwheel, and a butterfly flexure. The presented motion stage has a moving stage of 15 mm × 15 mm and shows a maximum displacement over 80 μm, and out-of-plane deformation under a weight of 120 μN less than 2 μm. The force generated by the actuator is estimated to be 68.6 mN.

A MEMS XY-stage integrating compliant mechanism for nanopositioning at sub-nanometer resolution

This paper reports a microelectromechanical systems (MEMS) based XY-stage integrating compliant motion amplification mechanism for nanopositioning at sub nanometer resolution. The MEMS stage is driven by bidirectional Z-beam electrothermal actuators that generate large output forces to actuate the motion amplification mechanism. The motion amplification mechanisms are used in their inverse (motion reduction) mode to convert micrometer input displacements (from the Z-beam actuators) into nanometer output displacements at a constant motion reduction ratio with good linearity. This unique design significantly enhances the positioning resolution of the XY-stage. An analytical model is developed to predict output displacements of the XY-stage as a function of the input voltages applied to the Z-beam actuators, and the predicted results agree with the experimental results. Capacitive displacement sensors are arranged along both X- and Y-axes for measuring the input displacements of the amplification mechanisms, enabling closed-loop nanopositioning control of the XY-stage. The device calibration results show that, within an actuation voltage of ±15 V, the MEMS stage offers a motion range close to ±1 μm and a displacement resolution better than 0.3 nm −1.

Research and simulation of piezo hydraulic actuator

A piezoelectric stack with its large output force and small displacement cannot satisfy the requirement of the opening of the cone valve core of the actual situation. Piezoelectric hydraulic actuator AMESIM model was established, and the influence on the output displacement and the driving force factors related to simulation and analysis was determined. The results show that the area of the piezoelectric stack has no effect on the output displacement of piezoelectric hydraulic actuator, but with the increase of the area of the maximum output of the piezoelectric hydraulic actuator drive led to nonlinear growth. In the simulation range of 0~60 Hz, the former has better vibration suppression effect than the latter. At some frequencies, the body vibration suppression ability can reach 6.4 times that of the latter.

Research and simulation of piezo hydraulic actuator

A piezoelectric stack with its large output force and small displacement cannot satisfy the requirement of the opening of the cone valve core of the actual situation. Piezoelectric hydraulic actuator AMESIM model was established, and the influence on the output displacement and the driving force factors related to simulation and analysis was determined. The results show that the area of the piezoelectric stack has no effect on the output displacement of piezoelectric hydraulic actuator, but with the increase of the area of the maximum output of the piezoelectric hydraulic actuator drive led to nonlinear growth. In the simulation range of 0~60 Hz, the former has better vibration suppression effect than the latter. At some frequencies, the body vibration suppression ability can reach 6.4 times that of the latter.

A high-force, out-of-plane actuator with a MEMS-enabled microscissor motion amplifier

The design, fabrication, and demonstration of a set of 2 mm2, high-force actuators that combine piezoelectric in-plane actuators with MEMS-enabled scissor mechanisms (motion amplifiers) to simultaneously produce high out-of-plane forces and large out-of-plane displacements are presented. The microscissor motion amplifier employs two layers of lithographically-patterned SU-8 microstructure laminated with a thin film of structural polyimide and adhesive to form hinges. Performance is optimized by varying layer thickness and adhesive types. Measured displacements of >3 μm and measured forces of >5 mN are observed, corresponding to a displacement per unit area of 1.6 μm/mm2 and a force per unit area of 2.6 mN/mm2. Cyanoacrylate adhesive provides superior performance to silicone adhesive, with larger force output. Thicker polyimide hinges provide smaller displacement but greater force than thinner polyimide hinges. These powerful, compact actuators have significant potential for high-force applications like tactile displays and micropumps.

Contributed Review: Application of voice coil motors in high-precision positioning stages with large travel ranges.

Recent interest in high-precision positioning stages with large travel ranges has sparked renewed attention to the development of voice coil motors (VCMs). Due to their large output force, VCMs can actuate more complicated flexure structures, eliminate rail friction, and improve positioning speed. The VCM structure is both compact and flexible; hence, it is convenient to design VCMs for a variety of stage structures. Furthermore, VCMs combined with other actuators are able to achieve large travel ranges with high precision. In this paper, we summarize the principles and control methods of a typical VCM, and we analyze its properties, including thrust force, acceleration, and response time. We then present recent research on high-precision VCM positioning stages with large travel ranges.

Design and experimental research of an improved stick–slip type piezo-driven linear actuator

A piezo-driven linear actuator based on the improved stick–slip principle is developed in this article. With the help of two piezo-stacks and flexure hinges, the preload force can be changed, so the designed actuator can realize relatively large linear ranges and large output force. The designed actuator mainly consists of the mover, the stator, two piezo-stacks, an adjusting stage and the base. The working principle and theoretical analysis are described. A prototype actuator was fabricated and a series of experiments were carried out to investigate the work characteristics of it. Experimental results indicate that the maximum speed is about 3.086 mm/s and the maximum output force is 0.98 N. They are both improved compared with the traditional stick–slip motion. Experimental results confirm that the proposed actuator can realize large output force relatively and different motion speeds with high accuracy under different driving voltages and frequencies.

A 3-DOF MEMS Electrostatic Piston-Tube Actuator

A three-degrees-of-freedom microelectromechanical systems (MEMS) electrostatic actuator was developed, fabricated, and tested. The actuator utilizes a piston-tube configuration that enables the use of electrodes with a wide area. Therefore, a large output force can be generated. The actuator also utilizes a flexure mechanism in which the in-plane (x-y) stiffness is high compared with the out-of-plane (z-axis) stiffness. This flexure mechanism enables a large translation stroke along the z-axis before experiencing lateral pull-in instability. A prototype of the actuator was able to achieve a pure translation (piston-style motion) of 28 μm at 80 V and an angle of rotation of 0.78° at 70 V. A mass of 1 mg was translated 24 μm at 80 V, indicating the ability of the actuator to provide high output force. The actuator was fabricated using the Micralyne MicraGEM-Si MEMS fabrication process, in which the pistons and tubes are fabricated in the device layers of two bonded Silicon on insulator (SOI) wafers. The misalignment between the pistons and the tubes using this process was ~0.005 of the gap between adjacent pistons and tubes. This amount of misalignment leads to a negligible lateral instability effect.

Design and Characterization of a Large Displacement Electro-thermal Actuator for a New Kind of Safety-and-Arming Device

Abstract The design, fabrication and characterization of a distinctive electro-thermal MEMS safety-and-arming device are presented in this paper. The device is comprised of a V-shape actuator and a micro lever. The V-shape actuator can generate a large output force but small displacement; thus, it is necessary to design a micro lever to amplify the insufficient displacement, which can broaden the device applications in different fields. The temperature distribution, the maximum displacement and the step response time of the actuator are analyzed and validated by the finite element analysis software ANSYS. The whole device is fabricated on SOI (Silicon-on-Insulator) wafer, and MUMPs process is introduced. The characterized performance of the device shows output displacement at more than 150 µm within 17 V driving voltage, and the consuming power is about 1.53 W. The chip size is about 5 × 5 × 0.5 mm3, which can be easily integrated with other micro devices.

Review of properties of magnetic shape memory (MSM) alloys and MSM actuator designs

Magnetic shape memory alloys are a new group of "smart" materials that exhibit large strain of 6-12% when subjected to magnetic fields. This indicates their enormous potential to be used in different electromagnetic (EM) devices such as actuators, sensors, energy harvesters and dampers. Shape change in MSM materials is controlled by magnetic field and doesn't involve phase transformation, allowing it to overcome a number of disadvantages of conventional shape memory alloys (SMAs). MSM devices are capable of producing large force and stroke output in considerably small dimensions. At the same time they can have fast response and potentially very long lifetime. This paper discusses different modern designs and approaches to MSM actuator design with their advantages and disadvantages. An overview on characteristics of MSM alloys is also presented in order to highlight how different properties of the material influence the total output of a device.

Piezoelectric inertial rotary actuators based on asymmetrically clamping structures

This paper presents innovative piezoelectric inertial rotary actuators based on asymmetrically clamping structures, which apply magnetic force to improve driving performance. By using a pretightening force control device, the designed actuators can realize high accuracy and stability. To test the influence of magnetic force on the driving property, two types of actuators are fabricated and investigated. Piezoelectric-driven force is the only driving source of the first actuator type, whereas magnetic force is applied to the second actuator type. An experimental system is built to test the performance of the actuators under different frequencies, voltages, and pretightening torques. Experimental results indicate that the stable minimum output stepping angle is 0.85μrad under a square signal of 20V, 6Hz and a pretightening torque of 2.475Nmm. Under the condition of 8Hz and 100V, the maximum angle velocity and output force can reach 4.02rad/s and 0.98N, respectively. The proposed actuators not only achieve a stable and accurate rotary motion but also realize a large output force and a fast velocity, thus contributing to the application of pretightening force control device and magnetic force.

Hydraulic System Design of Hydraulic Actuators for Large Butterfly Valves

Hydraulic control systems of butterfly valves are presently valve-controlled and pump-controlled. Valve-controlled hydraulic systems have serious power loss and generate much heat during throttling. Pump-controlled hydraulic systems have no overflow or throttling losses but are limited in the speed adjustment of the variable-displacement pump, generate much noise, pollute the environment, and have motor power that does not match load requirements, resulting in low efficiency under light loads and wearing of the variable-displacement pump. To overcome these shortcomings, this article designs a closed hydraulic control system in which an AC servo motor drives a quantitative pump that controls a spiral swinging hydraulic cylinder, and analyzes and calculates the structure and parameters of a spiral swinging hydraulic cylinder. The hydraulic system adjusts the servo motor’s speed according to the requirements of the control system, and the motor power matches the power provided to components, thus eliminating the throttling loss of hydraulic circuits. The system is compact, produces a large output force, provides stable transmission, has a quick response, and is suitable as a hydraulic control system of a large butterfly valve.

Parallel Vibration Isolation Platform Using Magnetorheological Technology

Within this work, a six-axis parallel vibration isolation platform with semi-active control ability is investigated. Traditional magnetorheological (MR) dampers could supply large output force and long stroke, but it also comes with a large self-weight. This problem is more serious when several MR dampers are needed in a parallel platform. Firstly, a double-piston MR damper have been developed, which will brings a small self-weight feature to the damper. Hyperbolic tangent model have been used to describe damper's nonlinear hysteresis. Using six of this double-piston MR damper, a parallel vibration isolation platform based on a cubic Stewart platform mechanism has been designed. Dynamical model of this platform has been built and simulated. Numerical simulation results in frequency domain indicate that the parallel semi-active vibration isolation platform has desirable vibration isolation properties in all six axes.

Note: A rigid piezo motor with large output force and an effective method to reduce sliding friction force

We present a completely practical TunaDrive piezo motor. It consists of a central piezo stack sandwiched by two arm piezo stacks and two leg piezo stacks, respectively, which is then sandwiched and spring-clamped by a pair of parallel polished sapphire rods. It works by alternatively fast expanding and contracting the arm/leg stacks while slowly expanding/contracting the central stack simultaneously. The key point is that sufficiently fast expanding and contracting a limb stack can make its two sliding friction forces well cancel, resulting in the total sliding friction force is <10% of the total static friction force, which can help increase output force greatly. The piezo motor's high compactness, precision, and output force make it perfect in building a high-quality harsh-condition (vibration resistant) atomic resolution scanning probe microscope.

Polymer-Based Wireless Resonant Magnetic Microrobots

This paper presents a new generation of wireless resonant magnetic microactuator (WRMMA) type microrobot, named PolyMite. A polymer is used as a spring material in the design of the PolyMite. Compared with the previous generation of such devices, the use of a polymer, i.e., SU-8, as a spring material enables the design of a stable spring system without a significant increase in stiffness. A speed of over 20 mm/s (40 body lengths per second) was measured when the PolyMite was driven in air. Micromanipulation abilities of the PolyMites in wet environments have also been demonstrated. The agents were capable of transporting microobjects such as light polystyrene beads and heavier glass beads in water. The large output force, remote actuation, and biocompatible outer surface (SU-8 and gold) make the PolyMite an exciting candidate for biomedical applications.

Smart Skin and Actuators for Morphing Structures

Morphing technology on aircrafts has found increased interest over the last decade because it is likely to enhance performance and efficiency over a wider range of flight conditions. The key technologies in morphing aircrafts include adaptive structures, deformable smart skin, driving actuators, flight dynamics and flight control. Among them, the deformable smart skin and light-weight driving actuators have been the main obstacles to the real-world implementation of the morphing aircraft. The difficulties in the smart skin rest on the contradiction between its ability to resist aerodynamic load in the normal direction and the in-plane flexibility for morphing functions. This contradiction cannot be solved by using sophisticated properties of the skin materials. It can only be solved by new skin structures, which give anisotropic stiffness for bending and in-plane deformation. In this article two skin structures for morphing aircrafts, the wavy skin structure and the honeycomb skin structure, are introduced. The actuators for morphing aircrafts are required to have large stroke, large output force, good compactness, and good controllability. In this article, piezoelectric-hydraulic actuators are introduced.