###### Abstract  
A numerical and experimental investigation of a flat, cross-shaped piezoelectric rotary motor is presented. The design and configuration of the motor allow it to be mounted directly to the printed circuit board or integrated into the other system where mounting space is limited. The design of the motor is based on the cross-shaped stator with 16 piezo ceramic plates, which are glued on it. The rotor is placed at the center of the stator and consists of two hemispheres, a shaft, and a preloading spring. Special clamping of the stator was developed as well. It consists of four V-shaped beam structures that allow it to rigidly clamp the stator with reduced damping effect to vibrations. The operation principle of the motor is based on the first in-plane bending mode of the cross-shaped stator. The motor excitation is performed through four harmonic signals, which have a phase difference of \(\pi\)/2. A numerical investigation of the motor was conducted to optimize the geometrical parameters of the stator and to analyze the displacement characteristics of the contacting point. The prototype of the motor was made, and the electrical, as well as rotation speed characteristics of the motor, were measured. The results of the experimental investigation showed that the motor is able to provide a maximum rotation speed of 972.62 RPM at 200 V\({}_{\text{P-P}}\) when the preload force of 22.65 mN was applied. p ezoelectric motor; flat cross-shaped stator; bending vibrations 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 July 2020 2020 July 2020 2020 July 2020 2020 20  
the printed circuit board (PCB) [11]. Despite this, there is a high demand for small size rotary motors that have a simple design, are scalable, and are well suitable for mounting directly on PCB [12]. [PERSON] and et al. reported on the 3-DOF motor based on cross-beam structure [13]. The motor was based on cross-beam shaped stator with 16 piezo ceramic plates which were glued around the free end of each beam. Excitation of the motor was performed by applying two harmonic signals with phase difference by \(\pi\). The operation principle of the motor is based on the superposition of bending vibration in the \(Z\) direction and two longitudinal vibrations in X and Y directions. A combination of these vibration modes allows one to obtain three types of elliptical motions, which are used to spin a spherical rotor around three axes. The numerical and experimental investigations showed that the maximum rotation speed of 363 RPM about the X-axis was obtained. Furthermore, it has been reported that rotation speeds about Y and Z axes are slightly lower compared to X-axis but are suitable for practical usage. [PERSON] and [PERSON] reported on the motor based on the octagonal plate [14]. The design of the motor was based on an octagonal piezoelectric plate, the thickness of the plate was 3 mm and it had a diameter of 25 mm. Two alumina eyelets were placed at the center of the octagonal plate and were used as the contact elements with increased friction. The operation of the motor was based on the first and second in-plane vibration modes of the plate. The combination of two different modes was used to generate normal and tangential forces and, as a result, generate the elliptical motion of the eyelets. Excitation of the vibrations was performed using four signals with different frequencies and phases. Numerical and experimental investigation revealed that the proposed motor is able to provide an output force of 20 mN and a maximum speed of 70 mm/s. [PERSON] and et al. reported on the cross-shaped ultrasonic motor for low voltage excitation [15]. The proposed design of the motor was based on 8 thin cantilevers composed of the cross-shaped stator, 16 piezo ceramic plates, and a double conical rotor placed at the center of the stator.