We designed a four-legged linear ultrasonic motor with a new structure. It uses the in-plane first-order longitudinal vibration mode and the out-of-plane anti-symmetric vibration mode, which are superimposed to produce linear motion. The motor consists of a stator and four groups of eight piezoelectric ceramic sheets. Under the excitation of a two-phase high voltage signal, the out-of-plane bending vibration and in-plane longitudinal vibration are generated in the stator. These vibrations alternately drive the motor through the front two driving feet and the back two driving feet, which leads to an elliptical motion. Thus, the four feet can effectively drive a slider to move in a straight line. An experimental prototype was fabricated with a size of 600 × 160 mm. The experimental results show that with a 200 V driving voltage, the maximum translational speed can reach 135 mm/s and the maximum thrust is 3.6 N. The motor has the advantages of simple structure and high output efficiency, which make it have a good prospect in precision systems and industrial applications.

In order to achieve the application of ultra-sonic motors in small pan/tilt/zoom (PTZ), this study designed a light arc-shaped ultrasonic motor where the first-order longitudinal vibration mode and the second-order bending vibration mode were superimposed in the stator plane, in order to drive the rotation of the rotor. The stator was fabricated by phosphorous bronze and piezoelectric ceramic. ANSYS was used to simulate the motor performance in order to optimize its size and determine its operating mode. The motion trail of the end surface of the driving feet was also simulated. The frequency and amplitude of the motor prototype were measured using a three-dimensional (3D) laser vibration meter. The results, which were in good agreement with the simulation results, demonstrated that the prototype exhibited favorable vibration characteristics. The mechanical characteristics of the prototype were also tested. At an operating frequency of 126.5 kHz and an excitation signal of 350V_pp, the maximum rotating speed of the motor reached up to 230 rpm. Finally, the output torque of the motor configurations with single-stator and double-stator were proposed respectively was investigated. The output torque of the motor under the single-stator configuration reached up to 2.6×10^-2 N·m, The double-stator which was 1.5 times greater than that under of single stator configuration. Conclusively, the designed motor is characterized by its light weight, high torque, and favorable output performances.

Traditional ultrasonic motors can usually produce either linear or rotational motion. Piezoelectrically driven structures with multiple degrees of freedom require two or more ultrasonic motors, and the manufacturing process is associated with some problems related to their complex structure and difficult control. This study proposes a new structure of a multi-degree-of-freedom piezoelectric crawling robot. Four modes are selected as the working modes, and mode superposition is used to produce the linear and rotational motion of the robot. This structure is designed based on a combination of size and topological optimization to adjust the frequency response consistency of the motor. The performance of the motor was tested on surfaces with different roughnesses. Its performance on the desk surface was the best. Its maximum linear speed is 37 mm/s, and its maximum rotational speed is 6.28 rad/s. The performance tests were performed under different loads. The linear motion speed of the motor reached its maximum value at 29.2 kHz, and the rotational motion speed reached its maximum value at 32.1 kHz.

Knowledge learning is a vital pre-factor and the driving force of green enterprise innovation; hence, meriting the numerous academic research and accumulated relevant literature. In this paper, the meta-analysis methodology was used to explore the direction and intensity of the influence of knowledge learning on green enterprise innovation, taking 32 independent documents as research samples. Meta-analysis results showed that the search breadth and the search depth of green resources and the green resources absorption and integration have significant positive effects on the green innovation of enterprises, among which green resources absorption and integration were the most important. Further, the research on the moderating effect found that the measurement method of green innovation affected the relationship between knowledge learning and green enterprise innovation; however, the moderating effect of the research object was not pronounced.

The traveling-wave rotary ultrasonic motor (TRUM) technique has become increasingly mature deepening of related research and development of related technology. The unique friction drive mode of a TRUM provides the advantages of a low speed, large torque, fast response, and a self-locking feature for power failure but also suffers from a relatively low efficiency. Regarding speed control, the commonly used approach of combining frequency modulation and speed regulation has provided the advantages of high precision and a wide range. Still, the load-carrying capacity of a TRUM is reduced when the driving frequency deviates from the resonant point, which is not conducive to the characteristics of low speed and large torque of the TRUM. To address this limitation, this study uses the pre-pressure and designs an electromagnetic clutch-type variable pre-pressure self-adjusting ultrasonic motor based on the TRUM-70 hollow ultrasonic motor. In addition, the force and motion analyses are conducted on the core components, and the basic parameters of the electromagnetic mechanism are calculated according to the specific design requirements. Furthermore, the Maxwell equation is used to simulate the designed magnetic circuit, and a prototype is fabricated and assembled. The feasibility of the proposed motor design is verified through experimental study, and the performance of the motor is compared with those of conventional ultrasonic motors. The experimental results show that the proposed electromagnetic clutch-type variable pre-pressure ultrasonic motor can effectively improve the output efficiency of the motor, especially when the load varies significantly.

Ultrasonic motors have been widely applied and promoted due to their advantages, such as low-speed high torque, fast response, and self-locking upon power loss. However, their working principle relies on contact friction drive, and the magnitude of the applied pre-pressure directly affects their performance output. Traditionally, the magnitude of pre-pressure applied to ultrasonic motors is mainly set during manufacturing and assembly and cannot be adjusted during operation, which also affects the maximization of their performance. To address the above issues, this paper proposes the design of an electromagnet-type variable pre-pressure ultrasonic motor that adjusts the pre-pressure by controlling the driving voltage of the coil. The force and motion analysis of the core components is conducted, and the basic parameters of the electromagnetic mechanism are calculated according to design requirements. An electromagnetic-type variable pre-pressure ultrasonic motor control circuit based on speed feedback is designed, and a control method for the variable pre-pressure motor is proposed. Magnetic circuit simulation is conducted, and internal structural size parameters are optimized. Finally, experiments are conducted on the processed prototype. The results show that using the electromagnet-type variable pre-pressure ultrasonic motor can achieve speed adjustment through pre-pressure adjustment, maintaining a wide adjustment range under heavy load conditions, which is conducive to achieving a better low-speed high-torque output.