Push-pull Actuator Research Articles

Mirrorless MEMS imaging: a nonlinear vibrational approach utilizing aerosol-jetted PZT-actuated fiber MEMS scanner for microscale illumination.

This study introduces a novel image capture and lighting techniques using a cutting-edge hybrid MEMS scanner system designed for compact microscopic imaging. The scanner comprises a tapered optical fiber waveguide and innovative aerosol-jet printed PZT (lead zirconate titanate) bimorph push-pull actuators on a stainless-steel substrate, effectively addressing issues that are commonly associated with PZT on silicon substrates such as fracture and layer separation. By leveraging nonlinear vibration, the scanner achieves a spiral scan pattern from a single signal input, in addition to the expected two-dimensional scanning and target illumination from two phase-shifted inputs. This capability is further enhanced by a novel process to taper the optical fiber, which reduces illumination scattering and tunes the fiber to the resonant frequencies of the scanner. The precisely tapered tip enables large fields of view while maintaining independent 2-axis scanning through one-degree-of-freedom actuation. Experimental validation showcases the successful generation of a spiral scan pattern with a 60 μm diameter scan area and a 10 Hz frame rate, effectively reconstructing scanned images of 5 μm lines, cross patterns (15 μm in length with a 5 μm gap), and structures of a Psychodidae wing.

Design and Experimental Characterization of a Push-Pull Flexible Rod-Driven Soft-Bodied Robot

Soft robots with a well-balanced performance in terms of dexterity, accuracy, and payload have a great potential for application. Balancing safe human-robot interaction with operation performance enables the use of soft robot in biomedical fields, among others, such as surgery, rehabilitation and elder care. In this letter, we present a rod-driven soft robot (RDSR) where the flexible rods embedded in the silicone-based body provide a double push-pull actuation, to satisfy the needs of balanced performance. The RDSR can realize multi DOFs movement with elongation, contraction and bending. For trajectory tracking, Gaussian process model enables RDSR to achieve more accurate motion control with an RMSE within 2.8 mm compared to the constant curvature model with that within 10.8 mm. Comparative experiments demonstrate that the workspace, vertical and lateral stiffness of the RDSR are up to 5, 2.6 and 5.2 times that of an analogous tendon-driven soft robot (TDSR), respectively. Additionally, the RDSR possesses the ability, that the TDSR does not have, to actively apply pushing perpendicular to an inclined plane. Based on numerical Jacobian matrix, the maximum force along target direction is greater than 4 N for a 30 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> plane. Furthermore, pick-and-place tests validate that our soft robot, with large workspace, precise and steady motion, is capable of conducting object manipulation tasks.

Piezo stepping actuator design with macrometer range and sub micrometer precision

A piezoelectric actuator is a device that provides a large displacement with micro-meter accuracy and nanometer resolution. The displacement accomplished by the piezo stepping actuator was in steps. This mechanism provides high precision, accuracy, and resolution with low power consumption. A stepping linear motion of the actuator based on the piezo stepping actuator was proposed in this work. The stepping motion of the piezo stepping actuator was attained with the help of four push–pull actuators, four lock-release actuators, and two flexural amplified piezoelectric (FAP) actuators. The designed actuator provided a large range of linear displacements with high accuracy. The designed configuration and working principle of the piezo stepping actuator are discussed. Finite element analysis was carried out on the final assembly of the piezo stepping actuator for the maximum displacement obtained from the supporting block. A suitable stepping frequency for the smooth operation of the piezo stepping actuator was adopted. The push-pull actuator, lock-release actuator, FAP actuator, and base assembly were fabricated and tested for displacement values.

A Variable Curvature Model for Multi-Backbone Continuum Robots to Account for Inter-Segment Coupling and External Disturbance

Multi-backbone continuum robots demonstrated potentials for dexterous manipulation with proper payload capability in minimally invasive surgeries. Most prior works assume constant curvature shapes of the continuum segments in the modeling and control of the multi-backbone continuum robots. The actuation coupling effects between adjacent continuum segments and the segments' variable curvature shapes under environmental interactions have not been fully addressed by a static-kinematic model specifically for multi-backbone continuum robots. This letter hence proposes a variable curvature model for multi-backbone continuum robots with relatively low bending curvature based on the Cosserat rod theory. The model focuses on the major factors that affect the robot's shape: the length-prescribed push-pull actuation, the elastic elongation of the backbone rods, and the external loads. With five assumptions made to simplify the constraints in the multi-backbone continuum robot, a compact statics-kinematics formulation is derived with computational performance acceptable for real-time control. Experiments were conducted on a continuum robotic system to quantify the modeling accuracy and computational efficiency. The proposed model was shown to have substantially improved accuracy over the constant curvature model. The average computational time for solving the inverse kinematics was 0.7ms on a 2.6 GHz Intel i7-5600U platform, which is promising for real-time control.

Validation and optimization of a compact push-pull rubber actuator energized by an outer coil of shape memory wire

The authors have formerly published the analytical model and finite element validation of a push-pull actuator made by winding a thin shape memory wire on a solid rubber cylinder. The cylinder provides elastic backup for the wire upon cooling down and transforms its circumferential contraction into a magnified axial elongation upon heating up. Building on that study, this paper accomplishes three tasks: (1) build prototype actuators and perform simple tests to validate the theory; (2) develop simple procedures for the optimal design of the actuator starting from high-level engineering specifications; (3) envision how the present concept could be improved by replacing the rubber block with a compliant lattice-like or shell-like scaffold with designed properties to further enhance the axial stroke.

Design and Fabrication of a Push-Pull Electrostatic Actuated Cantilever Waveguide Scanner.

The paper presents a novel fully integrated MEMS-based non-resonating operated 2D mechanical scanning system using a 1D push-pull actuator. Details of the design, fabrication and tests performed are presented. The current design utilizes an integrated electrostatic push-pull actuator and a SU-8 rib waveguide with a large core cross section (4 μm in height and 20 μm in width) in broadband single mode operation (λ = 0.4 μm to 0.65 μm). We have successfully demonstrated a 2D scanning motion using non- resonating operation with 201 Hz in vertical direction and 20 Hz in horizontal direction. This non-resonating scanner system has achieved a field of view (FOV) of 0.019 to 0.072 radians in vertical and horizontal directions, with the advantage of overcoming its frequency shift caused by fabrication uncertainties. In addition, we observed two fundamental resonances at 201 and 536 Hz in the vertical and horizontal directions with corresponding displacements of 130 and 19 μm, or 0.072 and 0.0105 radian field of view operating at a +150 V input. A gradient index (GRIN) lens is placed at the end of the waveguide to focus the diverging beam output from the waveguide and a 20 μm beam diameter is observed at the focal plane. The transmission efficiency of the waveguide is slightly low (~10%) and slight tensile residual stress can be observed at the cantilever portion of the waveguide due to inherent imperfections in the fabrication process.

A push-pull double-contact MEMS relay fabricated by MetalMUMPs process

This document presents a push-pull double-contact MEMS (Micro ElectroMechanical System) relay. The MEMS relay is electrostatic driven and laterally actuating. Two push-pull structures form two parallel contacts for the proposed MEMS relay, which can make the contact resistance of the MEMS relay be smaller. The push and pull actions of the push-pull actuators can be accomplished simultaneously using only one action signal. In addition, high inductance DC bias line and substrate removal are used for additional electrical and/or thermal isolation. The fabrication of the proposed switch is based on the standard MetalMUMPs process. The measured pull-in voltage is 116 V and the switch-ON delay is 44 μs. Contact resistance of the MEMS relay is less than 1 Ω when the stress voltage exceeds 120 V.

2D MEMS electrostatic cantilever waveguide scanner for potential image display application

This paper presents the current status of our micro-fabricated SU-8 2D electrostatic cantilever waveguide scanner. The current design utilizes a monolithically integrated electrostatic push-pull actuator. A 4.0 μm SU-8 rib waveguide design allows a relatively large core cross section (4μm in height and 20 μm in width) to couple with existing optical fiber and a broad band single mode operation (λ= 0.7μm to 1.3μm) with minimal transmission loss (85% to 87% output transmission efficiency with Gaussian beam profile input). A 2D scanning motion has been successfully demonstrated with two fundamental resonances found at 202 and 536 Hz in vertical and horizontal directions. A 130 μm and 19 μm, corresponding displacement and 0.062 and 0.009 rad field of view were observed at a +150V input. Beam divergence from the waveguide was corrected by a focusing GRIN lens and a 5mm beam diameter is observed at the focal plane. The transmission efficiency is low (~10%) and cantilever is slightly under tensile residual stress due to inherent imperfection in the process and tooling in fabrication. However, 2D light scanning pattern was successfully demonstrated using 1-D push-pull actuation.

Development of a Compact Deformable Mirror Using Push-Pull Actuators

A small deformable mirror which realizes concave shape as well as convex shape has been developed. In addition, this deformable mirror was developed to realize long term stability. For this purpose, a new push-pull actuator using two multilayered piezoelectric actuators aligned inline was designed. In this process, a practical method for simulating the property of piezoelectric actuator in the finite element method was proposed. From the experimental results, it was confirmed that newly developed deformable mirror has the ability to make complex profiles. Furthermore, efficiency of proposed simulation method was also confirmed.

Modular System for Testing the Performance of Poly-Articulate Robotic Structures

This paper presents a modular system for testing the performance of a poly-articulate robotic arm (snake like) with the push-pull actuation redundancy. Mechanical structure contains modules that allow testing of robots with different structures of the robotic arm (discrete hyper-redundant, continuous). Sensory system can be configured depending on the product and testing program adapting the sensors of position, velocity, time and vibrations. The monitoring system developed allows the automatic calibration of actuators and sensors, data and signal acquisition.

MEMS Based Mechanical Resonant Push-Pull Scanning Endoscope

Here we present a microfabricated SU-8 cantilever scanner. Current SU-8 rib waveguide design improved the output beam diameter of our previous design from ~50μm to ~5.0μm, further improves our spatial resolution. The proposed rib waveguide design also allows a relatively large waveguide cross section (4μm in height and 55μm in width) and broader wavelength range in single-mode operation (λ= 0.7μm to 1.3μm) with a minimum transmission loss (85% output transmission efficiency with Gaussian beam profile input). Our design also provides a new means to create a 2-D raster scanning pattern using a microfabricated push-pull actuator, verified by a transient finite element analysis (FEA). The scanner's line resolution and field of view (FOV) have been optimized through a parametric study using modal and harmonic analyses. This optical scanner may find application in the area of endoscopy, where there is a need for a minimally invasive device that reduces patient discomfort.

Pneumatic Push-Pull Actuator for an Active Suspension

The following contribution describes the design and validation of a pneumatic push-pull actuator used for vibration isolation. A point of major interest is to evaluate the influence of active controllable forces in pull-direction in addition to forces in push direction, in order to prevent the system from hitting into the bumpers in case of large excitations.In a first step, the model of the pneumatic cylinder and the valve is derived and linearized and a strategy to control the force of the pneumatic actuator is presented. In the next step a vibration controller is designed for a 1 DOF model of a quarter cabin of a commercial vehicle based on the Skyhook-principle. By using further control concepts, it is possible to use the developed control-concept for the overall cabin with its three degrees of freedom.The derived control concepts are evaluated regarding to the amount of vibration suppression and regarding to the possibility of preventing the system from hitting into the bumpers using a hydraulic test bench. While the comfort cannot be improved using the pneumatic push-pull actuator, the system can be operated safely without reaching the mechanical end stops. Finally an advanced system configuration improving the comfort and preventing from hitting into the bumpers at the same time is presented, which can be realized by an actuator combination consisting of an air spring and a fluidic muscle.

Correction of low order aberrations using continuous deformable mirrors

By analyzing the Poisson equation describing the static behavior of membrane and bimorph deformable mirrors and biharmonic equation describing the continuous facesheet mirror with push-pull actuators, we found that to achieve a high quality correction of low-order aberrations these mirrors should have sufficient number of actuators positioned outside the correction aperture. In particular, any deformable mirror described by the Poisson equation requires at least two actuators to be placed outside the working aperture per period of the azimuthal aberration of the highest expected order. Any deformable mirror described by the biharmonic equation, such as a continuous facesheet mirror with push-pull actuators, requires at least four actuators to be placed outside the working aperture per period of the azimuthal aberration of the highest expected order, and these actuators should not be positioned on a single circle.

Some Factors Affecting Design, Construction, And Testing of High Reliability Relays

This paper describes some improvements in design, manufacturing, and testing of 2-pole and 4-pole 5-ampere high reliability relays of low profile and small volume. Design features contributing to long life and high reliability at full load or dry-circuit load include elimination of contact buttons, push-pull actuation rather than spring bias of common contacts, gold plating as a lubricant for armature pivots, peeling rather than sliding contact action to prevent sticking, improved methods of outgassing and sealing, and other features. Reasons are given to justify several unusual design features, including the orientation of contact blades with respect to the header and the use of coil cores working magnetically in parallel. Improved miss-testing equipment includes testing at both polarities, detection of make-before-break errors, and emphasizes suppression of inductive transients.