# The Development of a Soft Robot Hand with Pin-Array Structure
## 6 Conclusions  
This paper proposed, designed, developed and studied a soft robot hand with pin-array structure, which has the following conclusions:  
1. The grasping mode of CTSA was studied: the pin array slides up and down to realize the self-adaption to the shape and size of the target object, and then all the pins are gathered to the center to grasp an object.
2. According to the CTSA mode and the shortage of CTSA hand, a soft robot hand with pin-array structure (CTSA-II hand) was designed and a theoretical model was established. The CTSA-II hand has the characteristics of simple structure and easy assembly. Theoretical modeling analysis shows that CTSA-II can provide sufficient grasping force for conventional small objects, and can be stable when working. The factors affecting the grasping force CTSA-II hand were studied theoretically.
3. A series of prototypes of CTSA-II hand with different numbers of pins were developed and a large number of gripping experiments were carried out. The CTSA-II hand prototype has the advantages of small size, light weight, and easy assembly. Through a large number of experiments, the CTSA-II has a high degree of fit to the object when grasping the object, sufficient grasping force, high grip reliability, and good fault tolerance rate of the object position information.  
In the follow-up work, the main problems to be solved are: (1) implementing automated crawling and studying a reasonable set of crawling strategies; (2) optimizing the design of the CTSA-II hand and forming a normalized design system to optimize the CTSA-II hand design with optimal parameters for different gripping situations.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Number of Pins** & **Offset Distance** & **0 mm** & **2.5 mm** & **5 mm** & **7.5 mm** & **10 mm** & **12.5 mm** & **15 mm** \\ \hline
8 & 100\% & 100\% & 100\% & 100\% & 60\% & 30\% & 10\% \\
10 & 100\% & 100\% & 100\% & 90\% & 70\% & 30\% & 20\% \\
12 & 100\% & 100\% & 100\% & 90\% & 50\% & 20\% & 0 \\ \hline \hline \end{tabular}
\end{table}
Table 6: The effect of the offset distance of the object on the grasping performance.  
**Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2076-3417/9/5/1011/s1](http://www.mdpi.com/2076-3417/9/5/1011/s1)]([http://www.mdpi.com/2076-3417/9/5/1011/s1](http://www.mdpi.com/2076-3417/9/5/1011/s1)), MovieS1: Driving experiment without grabbing an object; MovieS2: Grasping experiments of conventional objects; MovieS3: Working with the robotic arm.  
**Author Contributions:** The individual contributions of authors: conceptualization, H.F. and W.Z.; methodology, H.F.; validation, H.F.; formal analysis, H.F.; investigation, W.Z.; resources, W.Z.; data curation, H.F.; writing of original draft preparation, H.F.; writing of review and editing, H.F. and W.Z.; visualization, H.F.; project administration, W.Z.; funding acquisition, W.Z.  
**Funding:** This research was supported by the National Natural Science Foundation of China (No. 51575302), Beijing Natural Science Foundation (No. JJ70005) and National Key R&D Program of China (No. 2017 YFE0113200).  
**Conflicts of Interest:** The authors declare no conflicts of interest.