Piezo Unit Research Articles

A planar piezoelectric motor of two dimensional XY motions driven by one cross-shaped piezoelectric unit: A new principle.

We present a two-degree-of-freedom piezoelectric motor, which is driven by a simple cross-shaped piezo unit. Here, not only the structure of high novelty and simplicity but also the working principle is new. The cross-shaped piezo unit is sandwiched between top and bottom guiding plates with roughly equal pressing forces applied between the four free ends of the piezo unit and the plates. The working principle is as follows: A pair of opposite arms of the piezo unit quickly and simultaneously expand and contract periodically in the X direction, which results in a vanishing total friction force in the X direction; meanwhile, the other two arms in the Y direction deform slowly in a push-pull manner, which will move the aforementioned X-direction arms a step in the Y direction; then, the Y direction piezo arms restore their initial states slowly one by one. Repeating these actions will produce continuous stepping in the Y direction. Because the structure is symmetric in X and Y directions, we can similarly produce stepping in the X direction. The advantages are obvious: compact, rigid, and planar, which are all important for high stability and, hence, crucial in building an atomically resolved scanning probe microscope.

Machine Tool and Technology for Manufacturing of Micro-structures by Micro Dry Electrical Discharge Milling

This paper presents a new machine tool concept for micro dry electrical discharge milling. It includes two different motion systems, EDM spindle and EDM generator, as well as the control system. The feed motion is realised with high-precision linear axes and the high-dynamic motion, needed for the gap width control, with a two axes piezo unit. A control system is based on the Open Source development platforms. It includes several microcontrollers, with each controlling individual subsystems of the machine. The hybrid EDM generator is based on the high speed GaN FET transistors, which allow to control charging and discharging phase of the capacitor without using resistance.

A Force and Displacement Self-Sensing Piezoelectric MRI-Compatible Tweezer End Effector With an On-Site Calibration Procedure

This paper describes a self-sensing technique for a piezoelectrically driven magnetic resonance imaging (MRI)-compatible tweezer style end effector, suitable for robot assisted MRI guided surgery. Nested strain amplification mechanisms are used to amplify the displacement of the piezo actuators to practical levels for robotics. By using a hysteretic piezoelectric model and a two port network model for the compliant nested strain amplifiers, it is shown that force and displacement at the tweezer tip can be estimated if the input voltage and charge are measured. One piezo unit is used simultaneously as a sensor and an actuator, preserving the full actuation capability of the device. An on-site calibration procedure is proposed that calibrates the combined electromechanical model without requiring specific loading conditions on the inner piezoelectric actuators. Experimental validation shows an average of 12% error between the self-sensed and true values.

Mechanical characterization of a piezo-operated thermal imprint system

Dynamic agitation during imprint is investigated as a means to reduce the imprint temperature of thermoplastic materials. The imprint system used consists of a stepping motor and a piezo unit as the main components. The motor controls the working point of the system, and a sinusoidal motion of the piezo unit (3 piezos at 120° with respect to each other) superimposes an additional dynamic excitation. The system was characterized with respect to its mechanical behavior by exploiting analogies between mechanical and electrical quantities. The results show that the system can be operated at a frequency of up to about 60 Hz and that the piezos act as a dynamic motion source in the system. First imprint experiments with polystyrene at 100 °C indicate the potential of this frequency-assisted imprint technique.

Production of cloned mice by somatic cellnuclear transfer

Although it has now been 10 years since the first cloned mammals were generated from somatic cells using nuclear transfer (NT), the success rate for producing live offspring by cloning remains < 5%. Nevertheless, the techniques have potential as important tools for future research in basic biology. We have been able to develop a stable NT method in the mouse, in which donor nuclei are directly injected into the oocyte using a piezo-actuated micromanipulator. Although manipulation of the piezo unit is complex, once mastered it is of great help not only in NT experiments but also in almost all other forms of micromanipulation. In addition to this technique, embryonic stem (ES) cell lines established from somatic cell nuclei by NT can be generated relatively easily from a variety of mouse genotypes and cell types. Such NT-ES cells can be used not only for experimental models of human therapeutic cloning but also as a backup of the donor cell's genome. Our most recent protocols for mouse cloning, as described here, will allow the production of cloned mice in > or = 3 months.

Unit injectors with piezo actuator for Euro 4 diesel engines

Diesel engines will only conform to the impending European and North American emissions limits with high performance injection systems. Together with Volkswagen, Siemens VDO Automotive has therefore developed the piezo unit injector (PUI), which allows more than 2,000 bar peak injection pressure and even more precise control of the injection process and injection quantities. The unit injector diesel engines with these PUI elements have unrivalled acoustic properties and conform to the exhaust standard Euro 4.

A resonance shear force rheometer modeled as simple oscillating circuit

A novel resonance method for studying the viscoelasticity of very thin liquid films and elastic materials is developed using a shear force apparatus. The shear stress created by an oscillating piezo unit attached to leaf springs is recorded as the lateral displacement by capacitance probe. The oscillation frequency is varied around the resonance frequency of the mechanical system in order to trace the amplitude and the phase of the resonance peak. Two reference states are obtained: the resonance of free oscillations in air and one under constrain introduced by the cantilever spring in contact with the shear mechanical unit. The presence of a liquid film changes these resonance states depending on the film thickness and the cantilever load. A simple mechanical model is proposed entrapping the contribution of different parts in effective spring, mass, and damping constants. The model separates the effect of the liquid film from the background oscillation of the mechanical parts. The method is applied here to investigate the elastic contact between two solid surfaces.