## 3 Novel Rotating Motion Mechanism
### Multi-Link Rotating Mechanism
#### 3.5.3 Cycloid Reducer
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Types** & **Advantages** & **Disadvantages** & **Applications** \\ \hline Cam connecting rod and planetary gear & High stability, compact structure, high speed operation, and reliability & The cost is high, and the connecting rod requires high manufacturing accuracy & High speed, low-damage vegetable transplanner and automated agricultural \\ Planetary gear and crank rocker propeller mechanism [133] & Real-time pitch control simplifies the transmission control of the system & Easy to wear and tear, poor vibration reduction & Ship propulsion, uncrewed aerial vehicles \\ Universal RV reducer [134] & High transmission ratio and strong ability to withstand torque, high precision, and low recoil & High cost and difficult maintenance & Industrial robot joints and other high transmission-ratio, high precision-demand scenarios \\ New two-stage cycloidal reducer [135] & Small size, phase difference offsets centrifugal vibration, and single-tooth stress safety & Complex design and assembly, low efficiency & Compact and high transmission ratio scenarios, such as robot joints \\ New single-stage precision cycloidal reducer [136] & High transmission efficiency, strong torsional stiffness, and simplified structure & High cost: the manufacturing process requires high & High efficiency and low friction loss scenarios, such as precision standards & High efficiency and low precision scenarios, such as precision instruments \\ \hline \hline \end{tabular}
\end{table} 
Table 15: Comparison of planetary rotary transmission mechanisms. Figure 76: Transmission principles and structural design of three different single-stage cycloidal pin reducers: (**a**) traditional cycloidal pin reducer, (**b**) precision cycloidal pin reducer (model: F4 CF), and (**c**) proposed new cycloidal pin reducer. The research status of planetary rotary transmission mechanisms presents characteristics of multidimensional innovation and engineering application expansion. Its core advantages lie in high transmission ratio, compact structure, and controllable dynamic performance. However, it faces cost, wear suppression, and manufacturing accuracy challenges. In agricultural automation, the combination mechanism of cam linkage and planetary gear (such as a vegetable translpater) adjusts the swing of the sun gear through the cam profile to optimise the variable speed rotation trajectory, significantly improving the stability and efficiency of the operation. However, the lack of adaptability to high precision linkage manufacturing and dynamic loads limits its large-scale application. In biomimetic propulsion systems, the collaborative design of planetary gears and crank rocker arms achieves superior biomimetic motion performance through dynamic pitch adjustment. However, the physical coupling mechanism between friction, wear, and vibration suppression must be further modelled. In the field of reducers, traditional RV reducers dominate in industrial robot joints with their two-stage gear pair design (planetary cycloid), but their complex assembly and maintenance costs have become bottlenecks for industrial promotion. The new two-stage cycloidal reducer improves compactness by offsetting centrifugal vibration through phase difference and integrating components, but the nonlinear characteristics of tooth contact still limit transmission efficiency and dynamic response. The precision single-stage cycloidal reducer replaces sliding friction with rolling friction, increasing transmission efficiency to 83.39%, revealing the importance of material interface optimisation and tolerance collaborative design.