Worldwide Research on Open Innovation in SMEs

Research on open innovation (OI) has increased in recent years, showing its potential in various areas of knowledge. Its relation to small and medium-sized enterprises has attracted the attention of academics. This article aims to evaluate the intellectual structure of the scientific study of OI, and its close relationship with various scientific fields, through a bibliometric analysis of this academic field using the Scopus database and the application of the VOSviewer software. The methodology comprises a rigorous systematic and transparent process divided into four phases: (i) the establishment of search criteria for the research field, through a literature review for its selection; (ii) the selection of the database, the establishment of the search equation and extraction of information; (iii) the application of inclusion and exclusion criteria for the selected documents and an explanation of the usefulness of the software; and (iv) the analysis of the results through the approaches of scientific output performance and bibliometric mapping. The results show an increasing trend of IO publications in SMEs, consolidated in 396 articles with contributions from 65 countries and 947 authors. The intellectual structure shows seven themes related to firm performance, R&D networks, business management, business models, capabilities and knowledge transfer. This study contributes to the field by providing an overview of IO in SME contexts. It also provides insightful information to policymakers for developing policies for firm economic growth.

Barrier Lyapunov function-based adaptive prescribed performance control of the PMSM used in robots with full-state and input constraints

The permanent magnet synchronous motor is extensively used in robots due to its superior performances. However, robots mostly operate in unstructured and dynamically changing environments. Therefore, it is urgent and challenging to achieve high-performance control with high security and reliability. This paper investigates an accelerated adaptive fuzzy neural prescribed performance controller for the PMSM to solve chaotic oscillations, prescribed output performance constraint, full-state constraints, input constraints, uncertain time delays, and unknown external disturbances. First, for ensuring the permanent magnet synchronous motor with higher security, faster response speed, and lower tracking error simultaneously, a novel unified prescribed performance log-type barrier Lyapunov function is proposed to handle both prescribed output performance constraint and full-state constraints. Subsequently, a continuous differentiable constraint function-based model is introduced for solving input constraints nonlinearity. The Lyapunov–Krasovskii functions are utilized to compensate the uncertain time delays. Besides, a type-2 sequential fuzzy neural network is exploited to approximate unknown nonlinearities and unknown gain. For the “explosion of complexity” associated with backstepping, a tracking differentiator is integrated into this controller. Furthermore, a speed function is introduced in the backstepping technique for accelerated convergence. On the basis of above works, the accelerated adaptive backstepping controller is achieved. And the presented controller can ensure that all the closed-loop signals are ultimate boundedness, and all state variables are restricted in the prespecified regions and the permanent magnet synchronous motor successfully escapes from chaotic oscillations. Finally, the simulation results verify the effectiveness of the proposed controller.

Piezoelectric stick-slip actuators with flexure hinge mechanisms: A review

Piezoelectric stick-slip actuators (PSSAs) are famous for ultimate working condition adaptability, simple structure, and positioning accuracy. To meet the demand of industrial application, lots of PSSAs designed with flexure hinge mechanisms (FHMs-PSSAs) have been developed to realize the requirements of translational motion, rotational motion, multi-degree-of-freedom (multi-DOF) motion. The output performance of the FHMs-PSSAs has been greatly improved, including load capacity, speed, and accuracy; moreover, some approaches to solve the problem of the backward motion are provided as well. In this work, the working principle of FHMs-PSSAs is introduced, and the excitation signals applicable to FHMs-PSSAs are summarized. Based on the current research and development status, the progress of structure design of FHMs-PSSAs is introduced in accordance with translatory FHMs-PSSAs, rotary FHMs-PSSAs, and multi-DOF FHMs-PSSAs. Additionally, the developed analysis methods and design schemes to improve the performance are introduced, including theoretical analysis methods, consistency scheme of forward and reverse performance, suppression scheme of the backward motion, and improvement scheme of positioning accuracy. The significance of this work can be regarded as a further supplement to the previous review articles on the PSSAs, which will provide a reference and guidance for the future development of FHMs-PSSAs.

Analysis of Preload of Three-Stator Ultrasonic Motor

The pre-pressure device of the ultrasonic motor plays a vital role in the design of the entire motor structure, the contact state of the stator and rotor of the motor, dynamic properties of the stator, friction and wear characteristics of the rotor; even the mechanical behaviors of the entire electric machinery have a profound impact. Appropriate pre-pressure is conducive to the smooth operation of the ultrasonic motor, so that the output performance remains excellent, reducing wear and effectively extend the service life of the motor. Therefore, the research on pre-stress is of great significance, as it can better optimize the structure of the three-stator ultrasonic motor and lay the foundation for the stable operation of the motor. First, this paper introduces the construction of the motor as a whole and the pre-pressure device briefly described the working mechanism of the motor, and then introduces the influence of the pre-pressure on the stator and rotor contact models, the position of the constant velocity point, and the modal frequency. Finally, the motor output under different pre-pressures is discussed. The performance experiment has determined the optimal pre-pressure interval, which provides help for its subsequent optimization.

Theoretical Analysis and General Characteristics for Nonlinear Vibration Energy Harvesters

In this paper, we present a systematic theoretical and numerical study of the output performance of nonlinear energy harvesters. The general analytical expression of output power for systems with different combinations of nonlinear stiffness and nonlinear damping, as well as symmetrical and asymmetrical systems, have been derived based on harmonic balance method, observing compliance with numerical results. We theoretically prove that there is a limit power for all nonlinear systems which is determined exclusively by the vibrator mass, excitation acceleration, and mechanical damping. The results also indicate that for symmetrical stiffness systems, the asymmetrical damping components have no effect on the output performance. Additionally, we derived semi-analytical solutions of the matching loads and numerically investigated the influence of nonlinear coefficients on the output power with matched load. When the load matches device parameters and is much larger than the internal resistance, the equivalent time-average damping is equal to the mechanical damping. Although the matching load and output power vary with the nonlinear coefficients, the normalized power and matching resistance ratio follow a power function, named matching power line, which is independent of the structural parameters. With the improvement of the equivalent time-average short-circuit damping in the vibration range, the normalized power moves to the right end of the matching power line, and the output power approach to the limit power. These conclusions provide general characteristics of nonlinear energy harvesters, which can be used to guide the design and optimization of energy harvesters.

Implementation of a number recognition algorithm built using a neural network on the BASYS3 FPGA panel

In recent years, some field programmable valve arrays (FPGAs) based on CNN release phase accelerators have been introduced. FPGA is widely used in portable devices. They can be programmed to achieve higher concurrency and provide better performance. The power consumption of the FPGA is lower than that of GPUs with the same workload. These reasons make the FPGA suitable for implementing the CNN release phase. They can provide relative output performance for GPUs and achieve low power consumption, which is very important for portable devices. To effectively implement the CNN output phase on the FPGA, the design should have high parallelism, and the hardware resources used should be minimized to reduce the area and power consumption. In the process of working with the help of a neural network, an algorithm for recognizing handwritten numbers is implemented. A special architecture is being created to implement a neural network at the appatent level. The performance during operation and power consumption is comparable to the performance of the processor and the GPU.

Efficient Key-Value Data Placement for ZNS SSD

Log-structured merge-tree (LSM-Tree)-based key–value stores are attracting attention for their high I/O (Input/Output) performance due to their sequential write characteristics. However, excessive writes caused by compaction shorten the lifespan of the Solid-state Drive (SSD). Therefore, there are several studies aimed at reducing garbage collection overhead by using Zoned Namespace ZNS; SSD in which the host can determine data placement. However, the existing studies have limitations in terms of performance improvement because the lifetime and hotness of key–value data are not considered. Therefore, in this paper, we propose a technique to minimize the space efficiency and garbage collection overhead of SSDs by arranging them according to the characteristics of key–value data. The proposed method was implemented by modifying ZenFS of RocksDB and, according to the result of the performance evaluation, the space efficiency could be improved by up to 75%.

Virtual Space Vector Pulse Width Modulation for Asymmetric T-Type Neutral Point Clamped 3-Level Inverter

This paper proposes a novel 3-phase asymmetric 3-level T-type NPC inverter and studies its PWM performance using a virtual space vector pulse width modulation control strategy. Firstly, the mathematical model and characteristics of this economical topology are described. Then, a virtual space vector approach is proposed to build a space vector diagram for designing SVPWM control. Similar to the conventional 3-level NPC inverter, the asymmetric inverter can also work with the neutral point voltage self-balancing in a fundamental period, which enables employment of this topology in various applications. Finally, simulation and experiment results under different load conditions have shown good output performance of the asymmetric 3-level topology. Similar tests are also performed on both conventional 2-level and 3-level inverters for comparison. For an almost similar number of different voltage vectors in the space vector diagram, the asymmetric 3-level topology can compete with conventional 3-level inverters for low-cost applications. The obvious benefit of the asymmetric 3-level inverter is a smaller number of switches devices while it can achieve output performance similar to that of the conventional 3-level. The comparative investigation also shows that the total loss given by SVPWM for the asymmetric 3-level configuration is lower than that of the traditional 3-level inverter.