# Motion Characteristics of Self-Sensing Piezoelectric Actuator for Yarn Micro-Gripper
## 4 Conclusions  
In this paper, we attempt to apply a piezoelectric yarn gripper with self-sensing instead of a conventional electromagnetic one to improve the performance of weaving machines. The comparison between experimental working capability and targets is shown in Table 4 and obtains the following conclusions:  
1. The BPBA has a working length of 41 mm and a width of 7.2 mm. Mechanical and electrical modeling is performed according to the structure of the piezoelectric actuator, and the working range of the actuator can be estimated according to the theoretical values, which proves that the piezoelectric actuator of this structure meets the working requirements of yarn clamping. At the same time, the self-sensing circuits based on charge detection are carried out on the basis of the physical model, and the non-zero amplification bias current and driver leakage resistance are further compensated.
2. The maximum clamping stroke of the clamping device is about 1668 \(\upmu\)m, and the maximum output force is about 776 mN, which meet the working requirements of yarn clamping. Compared with domestic and foreign micro-grippers, the clamping range and end clamping force are both improved.
3. By studying the negative correlation between the clamping distance and the end output force, the clamping distance can be decided according to the size of the target, so as to realize effective clamping for different targets.
4. The motion characteristics of the BPBA are analyzed by a high-speed camera, which shows a fast response speed and meets the requirements of a high-speed loom of 1000-1200 r/min. At the same time, its high response stability is greatly improved compared with the traditional electromagnetic-type yarn gripper
5. The maximum relative error between the self-sensing output force and the force measured by the external sensor was found to be 1.6%, and the average relative error was found to be 0.74%. These values are the same as or better than previously reported displacement force self-sensing techniques using charge and voltage measurements.  
Future work will focus on the design optimization of this BPBA to obtain a better structure of smaller size. The gripper is well suited for any application scenario in which micron-sized objects are clamped, moved, and positioned during high-speed movement of the weaving machine. Thus, the potential for continued exploration of application  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Micro-Gripper** & **Size** & **Clamping Stroke** & **Clamping Force** & **Response Speed** & **Force Sensing** \\  & **/mm** & **/\(\upmu\)m** & **/\(\upmu\)N** & **/\(\upmu\)ns** & **Relative Error** \\ \hline Target & - & 560 & 500 & 50 & 1\% \\ \hline BPBA & 41 \(\times\) 7.2 \(\times\) 0.79 & 1668 & 776 & 24 & 0.74\% \\ \hline \hline \end{tabular}
\end{table}
Table 4: Structure parameters of piezoelectric cantilever beams.  
scenarios for grippers also exists. Combined with better sensing and detection strategies, the gripper can realize functions such as gripping, movement, and state detection of micron-scale objects.  
Conceptualization, Y.S., L.P. and Y.Q.; Methodology, Y.S.; Software, Y.S.; Validation, Y.S. and Y.Q.; Formal Analysis, Y.S.; Investigation, Y.Q.; Resources, L.P. and X.R.; Data Curation, X.R.; Writing--Original Draft Preparation, Y.S.; Writing--Review and Editing, X.R.; Visualization, Y.S.; Supervision, L.P.; Project Administration, L.P.; Funding Acquisition, L.P. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Key R&D Projects of the Science and Technology Department of Zhejiang Province [Grant No. 2024C01124].  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors would like to thank Zhejiang Sci-Tech University for engaging in useful discussion on topics relevant to this work.  
The authors declare no conflicts of interest.