## 4 Common Driving Methods for Rotating Motion Mechanisms
### Pneumatic Drive
#### 4.3.2 Pneumatic Artificial Muscles  
[PERSON] et al. [185] proposed a rotational drive unit that combines compliance and high precision by combining pneumatic artificial muscles (PAMs) with inclined plate structures, as shown in Figure 95. The linear contraction force of PAMs is converted into rotational torque through the inclined plate structure, and the normal force is transmitted through the four pivot bearings, avoiding the stick-slip phenomenon of traditional aerodynamics. By independently adjusting the pressure of each PAM and controlling the total torque and system stiffness, high precision positioning and flexible motion can be achieved. Dynamic adjustment of system stiffness is achieved through pressure regulation to adapt to different load requirements. A 16-bit encoder and proportional valve control are used to achieve fine motion. However, the rotary drive unit has a large volume and weight, requiring lightweight improvements and independent control of multiple proportional valves. The system is complex and costly, with a maximum pressure limit of 600 kPa, which may limit torque output. Table 22 summarizes and compares the driving performance of the different pneumatic drives mentioned above. Figure 94: Multi-mode pneumatic motor based on rigid-flexible coupling structure. (**a**) Assembly drawing. (**b**) Driving principle. (**c**) Prototype. Figure 95: Realised modular laboratory test stand with five PAMs. In precision rotary motion mechanisms, pneumatic drive technology has demonstrated unique advantages due to its environmental compatibility, fast response, and adaptability to harsh working conditions. However, the coordinated control of high precision and high torque output still faces challenges due to core issues such as nonlinear hysteresis effects, material elastic deformation, and system inertia. The current research focuses on multimodal drive architecture and biomimetic structural innovation: a multi-mode pneumatic motor based on rigid-flexible coupling achieves rapid switching between continuous rotation and step mode through a dynamic coupling mechanism of silicone tube deformation and roller thrust. However, its step accuracy is constrained by the viscoelastic hysteresis and dynamic inertia disturbance of the silicone tube, and the fatigue resistance of silicone material limits its lifespan under high pressure conditions; The integrated design of pneumatic artificial muscles (PAMs) and inclined plate structures breaks through the bottleneck of stick slip effect in traditional pneumatic systems through a geometric conversion mechanism of linear contraction force rotational torque and a dynamic stiffness adjustment strategy. However, the system complexity brought by multi-valve independent control, the torque output threshold caused by material pressure limit, and the lightweight requirements of modular structures still need to be urgently addressed. The future development trend will revolve around multi-level optimisation of materials structure control: developing composite flexible materials with super elasticity and low creep characteristics to enhance deformation controllability; Using topology optimisation and additive manufacturing technology to achieve high power to weight ratio design of driving units; Integrating pressure flow collaborative compensation algorithm with high-resolution encoder feedback, a nonlinear hysteresis feedforward disturbance observation closed-loop control system is constructed. In addition, pneumatic electro-hydraulic hybrid drive, variable stiffness joints based on pneumatic impedance adjustment, and collaborative control of distributed pneumatic arrays will become important directions to break through the bottleneck of accuracy torque response speed trade-off, promoting the deep application of pneumatic drive technology in precision assembly, flexible surgical instruments, and adaptive robots.