The dissertation is devoted to solving the actual and important scientific and applied problem of improving the control efficiency of a piezoelectric micromanipulator based on linear piezoelectric motors on standing acoustic waves with a rectangular resonator in the micro- and nanospeed ranges, which was achieved due to the further development and improvement of existing control methods piezoelectric micromanipulator, development of hardware and software solutions, their implementation and control systems based on them.
Effectiveness here means the desired compliance with the following criteria:
- a wide range of movement speed;
- low vibration level;
-accuracy of positioning;
-maneuverability (accurate and quick reaction to the control command).
An analysis of the design of the micromanipulator, as well as its basic component – a linear piezoelectric motor, was carried out. The properties of the resonator of the piezoelectric motor, as well as the conditions for the formation of two mutually perpendicular mechanical oscillations in it for the emergence of a motion ellipse, were studied. This made it possible to evaluate the motor's capabilities, advantages and disadvantages in the context of its application in a micromanipulation system, as well as to determine ways to obtain improved characteristics of the final device. It has been established that the main advantages of this type of engine are the ability to maintain a position without applying additional energy and high start-stop characteristics (the possibility of almost instantaneous start and stop of the engine).
A research of the linear guides of piezoelectric motors, namely the angles of deviation of Pitch, Yaw and Roll from the rectilinear movement of the motor carriage (working tool of the manipulator) was carried out, which made it possible to estimate the amount of deviation of the working tool of the manipulator depending on its length. A mathematical model of the movement of the working tool of the manipulation system under the influence of Pitch and Yaw angular deviations has been developed, which makes it possible to algorithmically compensate the deviation data to minimize the positioning error of the micromanipulator, taking into account the experimental data obtained during the study of the guide motors.
With the help of the Comsol Multiphysics software complex, the simulation of mechanical vibrations of the piezoelectric resonator of the engine was carried out, which made it possible to confirm the necessity of choosing the right electrical resonance peak of the engine during its control.
On the basis of experimental studies of the engine characteristics, the model of mechanical oscillations of the resonator was confirmed, namely, that the resonance characteristic of the engine has two resonance peaks and the most effective method of controlling the engine speed is to adjust the excitation frequency in the zone of the right slope of the right resonance peak.
The method of controlling a piezoelectric motor with a rectangular resonator based on pulse width modulation (PWM) has been improved by minimizing the speed of the motor during its start and stop, which allowed to reduce the noise and vibration level by 2-10 times when working in the micro range.
The method of controlling the piezoelectric motor was further developed, which provided a speed control mode in the nanorange due to the use of a fixed number of excitation pulses (up to 20 in a sequence) with regulation of the frequency of following these sequences, which was formed by a mechanical means of controlling a micromanipulator (joystick, trackball), which made it possible to increase maneuverability by more than 2 times.
The method of increased positioning accuracy of the piezoelectric micromanipulator in automatic mode has been improved due to the avoidance of over-adjustments by changing the movement of the manipulator during continuous movement to a step mode of movement followed by a stop at the positioning point.
Algorithmic and software solutions for the implementation of improved methods of controlling a piezoelectric micromanipulator / motor and a control system based on them were developed, which allowed to achieve a speed control range of 140 mm/s - 0.05 mm/s, positioning accuracy with the encoder version (5-10) μm and, as a result, on average, increased the efficiency of the micromanipulator system in comparison with existing solutions by 2 times.
The means of controlling the parameters of new piezoelectric motors have been created, which allow to measure the characteristics of the piezoelectric resonator, to study the accuracy of movements of linear guides, and to measure vibration effects when researching new methods of controlling a piezoelectric motor, and to reduce the time of their testing by an average of 1.5-2 times.
