Tactile sensors with visible light feedback functions, such as wearable displays and electronic skin and biomedical devices, are becoming increasingly important in various fields. However, existing methods cannot meet the application requirements for the tactile perception of intensity feedback and extended intersection due to their limited light‐mapping performance and insufficient portability. Herein, a freely constructible self‐powered visual tactile sensor is proposed, which consists of a high‐output triboelectric nanogenerator (TENG) and a visual light source. The transferred charge of the TENG is enhanced to 746 nC by the structural design of the triboelectric material and device, which can easily drive the light source to generate a light signal with a brightness of 9.8 cd m−2. Notably, the application of the TENG enables to realization visual sensing of the palm‐grasp state and strength feedback without an external power supply. This visual feedback and power‐free tactile sensors are expected to have potential application in the field of artificial intelligence as a new interactive medium for smart protective clothing and robotics.

Wearable Triboelectric Visual Sensors for Tactile Perception

Flux-switching permanent magnet (FSPM) machines have received an intense amount of research interest in recent years, due to their advantages of high torque/power density, favorable thermal management, as well as passive and robust rotor structure. The purpose of this two-part companion articles is to provide a comprehensive overview of FSPM machines in terms of opportunities and challenges. In the early part of this two-part series, the operating principle, the modeling methods, the various machine topologies of FSPM machines, as well as the comparison with other PM machines, have been analyzed and investigated. Building upon Part (I), this article covers the analysis and design of winding configurations, the practical techniques to minimize the cogging torque and torque ripple, the control strategies, the technical challenges, as well as the emerging trends of FSPM machines. Moreover, the key features of the FSPM machines, including the merits and demerits of such machines as well as their associated techniques, are highlighted and summarized.

Flux-Switching Permanent Magnet Machines: A Review of Opportunities and Challenges-Part II: Design Aspects, Control, and Emerging Trends

Cellulose template-based triboelectric nanogenerators for self-powered sensing at high humidity

Applications of switched reluctance machine (SRM) are increasing in the industry due to their many desirable features. This study proposes a hybrid analytical model (HAM) of the SRM for the hardware-in-the-loop (HIL) simulation. To obtain satisfactory accuracy, the phase flux linkage is solved by the magnetic equivalent circuit (MEC) method when the stator and rotor poles overlap, and by the space harmonic method (SHM) when the poles do not overlap. The backward Euler and Newton-Raphson methods are used to calculate the exciting current, while the Gaussian quadrature is used to compute the electromagnetic torque in the HIL simulation. The digital hardware implementation of computation components are developed on the field-programmable gate array by exploiting the parallel hardware architecture and fully pipelined arithmetic processing. To highlight the performance of the HAM, the captured real-time results are compared with the off-line transient solution obtained through the co-simulation of Ansys Maxwell
 ®
, Ansys Simplorer
 ®
, and Simulink
 ®
, which model the SRM, drive circuit, and control system, respectively.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-epa.2016.0831

Hybrid analytical model of switched reluctance machine for real-time hardware-in-the-loop simulation

This paper analyzes the flux characteristics and normal force of the double-sided switched reluctance linear machine (SRLM) under the asymmetric air gap. The magnetic equivalent circuit (MEC) of the machine and the details of the flux paths configuration at six distinct mover positions under the asymmetric air gap are included. Then, six special mover position magnetization curves are calculated by solving the MEC with the method of Gauss–Seidel. The magnetic flux-linkage model and thrust model based on six distinct mover positions are established by analytical polynomial. Three-dimensional (3-D) finite-element method (FEM) simulation and the experimental study with the prototype hardware are carried out to validate the accuracy of the MEC model calculated for the flux linkage and normal force. The six distinct mover positions flux linkage and normal force calculated by the MEC are consistent with the 3-D FEM calculated data and experimental data. It indicates that the proposed method to calculate the flux linkage and the normal force is feasible and effective. The dynamic analysis is also conducted. The simulated phase current waveforms are also consistent with the experimental results. It indicates that the presented method can be used to simulate the phase current under the asymmetry air gap effectively. The normal force under different asymmetry rates is analyzed, which provides the theoretical basis for reducing the unbalanced force of the double-sided SRLM.

Flux Characteristics Analysis of a Double-Sided Switched Reluctance Linear Machine Under the Asymmetric Air Gap

With the vigorous development of the Internet of Things and artificial intelligence, the active sensing system based on triboelectric nanogenerators plays an excellent performance potential and application value as a pioneering technology for smart manufacturing. Nevertheless, achieving material innovation to strike a good balance between active sensing systems and environmental friendliness remains a difficult task. As the most abundant biopolymer on earth, the sustainability potential and excellent performance of cellulose are of great importance for the development of smart sensing systems. This review intends to provide a new perspective on the sustainability of smart active sensing systems to design and fabricate cellulosic triboelectric materials for self‐powered sensing systems. Herein, the structure and advantageous properties of cellulosic triboelectric materials are briefly described. Furthermore, the structure–property–application relationship of the materials is addressed from the perspective of material design and structure optimization. Next, the latest applications of cellulose triboelectric materials are comprehensively described in smart sensing fields such as environmental monitoring, smart home, smart medical, human–machine interaction, and the Internet of everything. Lastly, the current challenges and future developments of cellulose triboelectric materials for smart sensor systems are presented.

Sustainable Triboelectric Materials for Smart Active Sensing Systems

The voltage pulse injection method is widely used at the starting and low-speed sensorless operation of the rotary switched reluctance machine (SRM) and the linear SRM (LSRM). The conventional methods for the inductance estimation in voltage pulse injection, the current peak value method, and the current slope difference method have a limitation that the iron losses in the controlled SRMs/LSRMs should be negligible. In this study, a new inductance estimation method in the voltage pulse injection is proposed considering the iron losses. Assuming that the iron-loss currents in the energising and de-energising intervals are almost equal, the inductance estimations in the two intervals are conducted, respectively, and the actual inductance values without the influence of the iron losses can be obtained by a special operation of the two calculated inductance values. Take a designed LSRM as a test object, the results of the proposed method coincide well with the actual values as compared with the conventional methods. The novel inductance estimation can be utilised in the SRMs/LSRMs without the limitation of the iron losses, and then it can further improve the accuracy of the sensorless control in the voltage pulse injection method.

Inductance estimation method for linear switched reluctance machines considering iron losses

Due to the manufacturing inaccuracies or wear, the mover eccentricity of the double-sided linear switched reluctance machine (DLSRM) is practically inevitable, which gives rise to undesirable unbalanced normal force (UNF). This study investigates the UNF reduction methods in the eccentric DLSRM. According to the finite element analysis and magnetic circuit analysis, the flux distributions and the UNF of the healthy and eccentric DLSRM are compared, and it is proved that removing the mover yoke can alleviate the UNF in the eccentric situation. Furthermore, the effects of the stator winding connections on UNF are analysed via a transient two-dimensional finite element model. It shows that the UNF can also be reduced by connecting the coils of the windings in parallel. For verifying the two proposed methods, a prototype experimental platform is established, and the experimental results validate the analyses.

Jinxia Yuan

Papers

Wearable Triboelectric Visual Sensors for Tactile Perception

Sustainable Triboelectric Materials for Smart Active Sensing Systems

Inductance estimation method for linear switched reluctance machines considering iron losses

Influence of mover yoke and winding connections on unbalanced normal force for double-sided linear switched reluctance machine