# Development of Piezoelectric Inertial Rotary Motor for Free-Space Optical Communication Systems
## 1 Introduction
The motor also demonstrated high torque density and rapid response times, particularly under varying loads, with rapid acceleration to desired speeds, making it highly effective for precise positioning in space environments [28]. [PERSON] et al. developed a rotary piezoelectric motor using a rectangular frame with four actuators, enabling direct conversion of vibrational energy into rotational motion. This design is noted for its compactness and efficiency, attributes that are particularly beneficial in space applications where equipment space is at a premium. The actuators are activated by synchronized sawtooth signals, optimizing the response time and reducing energy consumption, thus aligning with the energy efficiency requirements of modern space missions. Motor motion characteristics include precise control of rotational speed, with smooth acceleration curves and minimal vibration during operation. The design demonstrated excellent torque generation and fine-tuned angular displacement control, essential for applications requiring high-precision positioning in space. Furthermore, the motor exhibited rapid response to changes in the signal, ensuring stable performance under various operational loads and environmental conditions, further underscoring its suitability for space missions [29]. [PERSON] et al. introduced a resonant inertial impact rotary piezoelectric motor featuring a self-clamping structure, which dynamically adjusts the contact force to optimize torque and enhance efficiency. The design focuses on high-speed rotational capabilities and precision, facilitated by the motor resonant operation on piezoelectric vibrations. Such features are essential for high-stakes applications in space exploration and satellite maneuvering, where precise and reliable actuation is critical [30]. Therefore, on the basis of the state of the art, the inertial piezoelectric motors stand out among piezoelectric actuation systems due to their ability to combine high precision with simple mechanical design and excitation schematics [31; 32]. Compared to traveling wave motors, inertial motors exhibit lower mass, volume, and structural complexity which are critical parameters for space applications [33]. Moreover, inertial motors and actuators, despite their design, can be driven in two modes, that is, resonance and non-resonance, which expands the flexibility of their application [34]. Finally, the simplicity in achieving rotary and linear motions without complex assemblies makes inertial motors and actuators highly adaptable to applications with constraints of size and weight [35]. This article presents both numerical and experimental studies of the piezoelectric inertial rotary motor whose target application is FSO systems. The main advantages, compared to the state of the art, of proposed motor design are small size and mass, simple and well-scalable design, and the possibility of direct motor integration to the printed circuit board (PCB). These physical advantages of the proposed motor are archived via a novel approach of motor structural design which allows composing three piezoelectric bimorph plates to one structure via a connection cylinder with reduced structural stiffness. Such composition of the motor allows to increase displacement amplitudes of contacts and, as a result, the dynamic characteristics of the whole motor. Finally, the main goal of this work is to investigate how a lightweight piezoelectric inertial motor operates under temperature conditions that are close to conditions that occur during FSO system operation and how these conditions impact the motor performance and motor excitation conditions. The numerical and experimental investigations were performed and have shown that the proposed motor design is capable of proposing stable and suitable motion characteristics in the temperature ranges which occur during FSO systems operation.