## 5 Conclusions and Future Research Direction
### Future Research Direction  
Future research on precision rotational motion mechanisms and their driving methods can be explored in depth in the following directions:  
1. Develop high-strength composite materials such as carbon nanotube-reinforced TPU and self-healing coatings such as ceramic-based gradient coatings, combined with laser melting additive manufacturing to achieve a lightweight and fatigue-resistant design of key components such as gears and cams. Regarding the tooth surface wear of planetary cycloidal reducers, super-lubricating coating technology can be explored. Breakthroughs are needed in room-temperature superconducting materials or magnetocaloric cooling technology to address the bottleneck of superconducting cooling for magnetic gears.
2. Embedding fibre optic or piezoelectric sensors in the mechanism to monitor real-time tooth contact stress and bearing temperature rise, and predicting wear trends through deep learning algorithms to achieve adaptive adjustment of the lubrication system. For piezoelectric ultrasonic motors, it is necessary to develop resonance frequency self-tracking technology to suppress efficiency degradation caused by load disturbances.
3. Combining magnetic levitation non-contact transmission with piezoelectric energy recovery to construct a low friction, high-efficiency composite drive system. For example, in a wave energy converter, a magnetic guide screw is used to efficiently convert linear motion into rotational kinetic energy, while vibration energy is recovered through piezoelectric materials.
4. Inspired by biological joints, design a flexible multilink mechanism that utilises the phase transition characteristics of shape memory alloys to achieve variable stiffness adjustment. Promote the standardisation of modular driving units and support rapid reconstruction and fault redundancy of robot joints.
5. A multi-scale dynamic model of the mechanism is constructed using artificial intelligence and topology optimisation algorithms. The impact of assembly errors on motion accuracy is quantified through digital twin technology, and design parameters are iteratively optimised by combining actual working condition data.  
[PERSON] was responsible for the conception and design, acquisition of data, analysis, and interpretation of data, drafting the initial manuscript, and critically revising it for important intellectual content. [PERSON] proposed a research topic and was responsible for the numerical analysis of the manuscript, and provided valuable suggestions for the manuscript. [PERSON] was responsible for designing the conception, interpreting data, and reviewing all manuscript drafts. [PERSON] and [PERSON] collected data and images, completed the follow-up information, and wrote a draft. [PERSON] and [PERSON] were responsible for conception and design and reviewing all manuscript drafts. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Natural Science Foundation of Shandong Province (No. ZR2024 QE358) and the Doctoral Research Fund Project of Shandong Jianzhu University (Grant No. X21030Z), and Shandong Province Science and Technology based Small and Medium sized Enterprises Innovation Capability Enhancement Project (No. 2023 TSC0190, No. 2024 TSC0342).  
**Institutional Review Board Statement**: Not applicable.  
**Informed Consent Statement**: Not applicable.  
**Data Availability Statement**: Not applicable.  
**Conflicts of Interest**: The authors declare no conflicts of interest.