## 4 Conclusions  
This paper introduces a novel TM-UAV to maximize the horizontal pulling force and the yaw moment. Compared to extensive research on existing TM-UAVs, the pitch-axis tilting mechanism called Tilt-X is proposed. Compared to other TM-UAVs, it could maximize the horizontal pulling force, since all rotors tilt in the same direction, and the yaw moment, since two rotors tilt in one direction and the other two tilts in the other direction, resulting in producing the moment in the yaw axis. Based on this configuration, it is expected that the proposed Tilt-X can be applied in the following aerial manipulation scenarios:  
1. Performing aerial horizontal interactions to attach or detach objects on a wall, including surveillance equipment, environmental monitoring instruments, and building inspection devices;
2. Performing aerial torsional interactions to turn valves, such as fire hydrant valves and pipeline valves.  
In addition, this work presented the rigid body model and the dynamic model of the proposed mechanism. A series of experiments demonstrate the capabilities of this design and verify the accuracy of the mathematical model. However, there are still some discrepancies between the theoretical values and the experimental values, which are unavoidable with manual open-loop control without feedback. Future work will involve designing an automatic feedback closed-loop controller to reduce the error between the experimental and theoretical values of pulling force and yaw moment by real-time control of the propeller tilt angles. This will improve the accuracy of the wrench applied to the environment through force and moment control. Additionally, the Tilt-X experiments presented in this paper for the translation experiment and rotation experiment are not actual flight experiments. Whether or not Tilt-X can perform the aforementioned aerial horizontal interactions and aerial torsional interactions in a real environment remains to be verified. Therefore, research on Tilt-X performing actual APhI tasks will be conducted in the future.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app1416181/s1](https://www.mdpi.com/article/10.3390/app1416181/s1)]([https://www.mdpi.com/article/10.3390/app1416181/s1](https://www.mdpi.com/article/10.3390/app1416181/s1)), Video S1: Movie clip about experimental setup and procedure  
Conceptualization, S.Y.K.; methodology, X.T. and S.Y.K.; software, X.T.; validation, X.T.; formal analysis, X.T. and S.Y.K.; writing--original draft preparation, X.T.; writing--review and editing, X.T. and S.Y.K.; visualization, X.T.; supervision, S.Y.K.; project administration, S.Y.K.; funding acquisition, S.Y.K. All authors have read and agreed to the published version of the manuscript.  
This paper was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2022R1A2C2008422) and by the \"Regional Innovation Strategy (RIS)\" through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (MOE) (2021 RIS-002).  
**Institutional Review Board Statement:** This article does not contain any studies with human participants or animals performed by any of the authors.  
**Informed Consent Statement:** This article does not contain patient data.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.  
**Conflicts of Interest:** The authors declare no conflicts of interest.