Piezo-driven Actuator Research Articles

A novel micro drill design based on Ros-DrillⒸ.

This paper presents the development of a novel micro drill device for single living organisms. Currently, microinjection for mice and some other species is performed with the help of piezo-driven actuators with a very small amount of mercury column in the proximal end of the pipette in order to increase the success rate. However, the toxicity of mercury exhibits a risk factor both for the operator and the injected cells. Therefore, mercury-free devices have become a necessity. Here, a novel micro drill is developed based on the same principle of Ros-DrillⒸ piercing approach; piercing via rotational movements. The new drill is driven by a brushless motor, and it incorporates the micropipette holder. Both the amplitude and the frequency of rotational oscillations can be adjusted in very wide ranges. The experiments reveal that the drill is suitable for different tasks such as microinjection and biopsy of different organisms. It presents good performance in terms of success rate, ease of usage, compactness and compatibility with different manipulation systems.

Comparative study of spectral-element and finite-volume solvers for direct numerical simulation of synthetic jets

Direct Numerical Simulations of synthetic jet flow fields issuing in a quiescent environment, performed by means of two extensively used open-source computational fluid dynamics (CFD) codes, Nek5000 and OpenFOAM solver pimpleFoam, are reported and compared. While the former employs a high-order spectral-element method, the latter is based on finite-volume, lower-order schemes. The present paper specifically refers to SJ fields produced by slotted orifice piezo-driven actuators. The dimensionless flow parameters adopted to perform the simulations basically match the experimental data of Yao et al. (2006), whilst a reasonably simplified geometry of the actuator is adopted. Results are generally in good agreement with the experimental data for both codes, in terms of first- and second-order moments of the long-time and phase-averaged velocity field, as well as of global engineering quantities. The performances of the two codes are compared thoroughly, with regard to accuracy and computer load as well. Overall, when high-fidelity of simulations is required for the problem under study, Nek5000 is found to be computationally more efficient.

On the correlation between the structure and one stepping characteristic of a piezo-driven rotary actuator

The parasitic motion principle was recently proposed to design piezo-driven actuators. Based on this principle, linear and rotary actuators with features of compact structure, large motion range, high velocity and high positioning resolution have been reported. However, some shortcomings such as the backward motion and the nonlinearity still exist and their causes are not clarified. To find potential reasons leading to these shortcomings, one stepping characteristic of a piezo-driven rotary actuator designed by the parasitic motion principle was investigated in this paper, and the correlation between the structure and one stepping characteristic was attempted to be established by theoretical analysis and simulations. Analysis results indicated that the nonlinearity in one stepping characteristic of the rotary actuator was correlated to the small gap between the inner and outer rings of the bearing as well as the self-deformation of the flexible gripper after the contact stiffness between the flexible gripper and the rotor reaches to the maximum value. The backward motion could be mainly resulted from the non-ideal driving wave. These analysis results enhance the understanding of the parasitic motion principle, which are meaningful for design and performance improvement of the parasitic motion principle linear or rotary actuators.

Finite Element Simulations of an Inchworm Type Piezo-Driven Rotary Actuator

The inchworm-driven actuator is an important type of piezo-driven actuators, which has high loading capacity, large motion range and high motion accuracy but involves complex structures, control and motion processes. In this paper, an inchworm type piezo-driven rotary actuator was introduced. Static and modal analyses of key units of the rotary actuator such as the clamping unit and the driving unit were carried out by finite element simulations to ensure that key units of the rotary actuator have enough strength and good dynamic characteristics. These simulation results will be helpful to improve structure design of the inchworm actuator.

In situcycling and mechanical testing of silicon nanowire anodes for lithium-ion battery applications

In this work, we investigate the mechanical properties of silicon nanowires, which have been subjected to in situ electrochemical alloying and de-alloying with lithium inside a scanning electron microscope (SEM). Following de-alloying, in situ tensile testing of wires was performed inside a SEM using a microelectromechanical force sensor and a piezo-driven actuator. Compared to pristine silicon nanowires, the de-alloyed wires show a significant decrease in both their elastic modulus as well as in their ultimate tensile strength with indications that the newly formed amorphous silicon layer changes the mechanical properties of the wire.

Six-DOF micro-manipulator based on compliant parallel mechanism with integrated force sensor

This paper describes the design of a micro-scale manipulator based on a six-DOF compliant parallel mechanism (CPM), which is featured by piezo-driven actuators and integrated force sensor capable of delivering six-DOF motions with high precision and providing real-time force information for feedback control. Particularly, the position and screw-based Jacobian analyses of the CPM are presented. Then, the compliance model and the workspace evaluation of the CPM are proposed in order to account for the compliance and obtain design guidelines. Finally, the integrated sensor is introduced. The static features of such a mechanism include high positioning accuracy, structural compactness and smooth and continuous displacements.

Experimental and numerical studies of synthetic jets driven by a dual-diaphragm piezoelectric actuator

The applications of piezoelectric synthetic jet actuators have shown great potential as active flow control devices. The objective of this study is to investigate the flow phenomenon of a synthetic jet generated by a dual-diaphragm piezo-driven actuator. In this analysis, the computational approach adopted unsteady three-dimensional conservation equations of mass and momentum for examining the development process of synthetic jets. The moving boundary was also treated to represent the motion of the piezo diaphragm. Experimentally, a flow visualization system was employed to acquire the particle-streak images scattered from red fluorescent spheres for observing the synthetic jet flow. The jet velocity along the centre-line was also measured by using a hot-wire anemometer. The system test results demonstrated a satisfactory functioning of the actuator for producing synthetic jets. The predictions were then compared with the visualized particle-streak images and the measured centre-line velocity of the synthetic jet to validate the computer software. In the near-field, both simulation results and experimental observations revealed the time-cyclical formation and advection of a vortex pair in a full sinusoidal actuation cycle at an operating frequency of 4 Hz. When the vortex pair travelled well downstream, the ambient air from the vicinity of the slot was entrained into the cavity of the actuator. However, the overall far-field flow pattern, characterized by longitudinal decay of the centre-line velocity and lateral spreading, resembled a conventional continuous air-jet in essence.

Design and Optimization of an XYZ Parallel Micromanipulator with Flexure Hinges

In this paper, a nearly decoupled XYZ translational compliant parallel micromanipulator (CPM) is designed for micro/nano scale manipulation with features of piezo-driven actuators and flexure hinges. The CPM structure improvement is made to enlarge the workspace and eliminate or reduce the stress stiffening, buckling phenomenon, and parasitic motions of the original XYZ CPM, which leads to a new CPM with a more compact structure. The CPM kinematics, parasitic motions, and workspace are determined analytically, and the mathematical models describing statics and dynamics of the CPM are established to evaluate its related performances, which are verified by the finite element analysis (FEA) undertaken in ANSYS environment. Based on the analytic models, the CPM dimensions have been optimized by resorting to the particle swarm optimization (PSO) approach, which produces a CPM having minimum parasitic motions and satisfying other performance specifications as validated by the FEA simulations.

Piezo Driven 3 D.O.F. Actuator for Robot Hands

Robot arms such as those used for assembling optical parts or semiconductors require high positioning accuracy. However, the most accurate robot arms at present can be positioned to an accuracy of 10μm at best. In order to realize accurate arm positioning, robots should be equipped with precise positioning actuators. This paper describes an accurate, lightweight piezo-driven actuator. The actuator functions using an inchworm movement and is driven by six piezoelectric elements. It moves precisely along the X, Y, and <I>θ</I> axes. A step translation of 4.2μm, step rotation of 0.52mrad, and closed-loop positional accuracy of ±0.05μm are achieved. Also discussed is the mechanical relationship between the piezoelectric elements holding the actuator and the plate.