Their first strong point is the absence of induction windings, manufactured, as a rule, from copper or aluminum wire, and a ganged core. Their working element is made of piezoelectric ceramics, one of the few materials now used in engineering capable of transforming electric energy into mechanical energy with fantastic efficiency exceeding 90% for some types. It allows for the manufacture of unique instruments in which electric oscillation is directly transformed into rotational motion of the rotor. In the process a force developed on the axle of such an engine is so great that it excludes the need to use any mechanical gear for increasing the torque. FEEs are significantly smaller in dimensions and weight in comparison with electromagnetic engines having similar power characteristics. The absence of winding impregnated with gluing compositions makes them suitable for use in a vacuum. FEEs have significant moments of self-braking (up to 50% of the torque max value) with no supply voltage thanks to their design features. It allows for extremely small quantified angular movements (from units of angular seconds) without application of any special measures. This property is connected with the near-continuous nature of piezoengine operation. The piezoelement actually transforming electric oscillation into mechanical ones is supplied not with direct voltage but with alternating resonance frequency voltage. A very small angular movement of the rotor may be achieved by delivering one or two pulses. For example, some PEE prototypes with an operating rotation frequency equal to 0.2-6 rps, after a single pulse is delivered on plates of the piezoelement, will ideally case ensure rotor angular movement equal to 1/9 900 000 - 1/330 000 of the circle, i. e. 0.1 3 - 3.9 angular seconds.

We have developed engine designing principles which improve this parameter by one order of magnitude. It is known that it is practically impossible to achieve such results through the use of traditional electric devices. One of the most important properties of PEEs is the possibility (and sometimes simply the necessity) for controlling their operation with the help of a processor or a computer.

We have developed several PEE-based devices, and shall dwell on only two of them.

The first one is a model of the "artificial kidney" monitor. The GAMBRO model supplied to the USSR during the last 20 years was taken as a basis. If the standard drive is replaced by a PEE with similar parameters, which we have developed, its cost will be reduced several times. The second one is a model of the peristalsis pump with dimensions 100x90x21 mm and weight about 200 g. The power consumed is 8 Wt. The capacity of the pump is 70 ml/min. The use of such pumps in research equipment, for instance, for titration, dispensing liquids, etc., is extremely promising especially in those cases when connection with a processor or a computer is required.

PEEs may also be successfully used in those engineering fields where minimum angular movements must be achieved. For example, in astronomy, in space research when accurate positioning by rather small objects (stars) is required; in accelerators where the energy beam must be kept within strictly determined geometrical coordinates; in research of a crystallographic form (for positioning the goniometer head), in robotics, etc. Such devices offer clear prospects for use in computers because their use would allow for a two or three time increase in the recording density on existing magnetic disks. By increasing the accuracy of positioning the readout head it is possible to expand the memory volume at least twice, retaining all the remaining computer characteristics.

In a short article it is impossible to cover all PEE applications. We have highlighted only those that most clearly demonstrate the advantages of this new type of electric device.

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