Researchers have developed a plant-inspired pneumatic soft physiotherapy actuator with variable-stiffness layers, addressing the challenges of low surface stiffness and inherent hysteresis in soft materials. The design mimics the morphology and behavior of clover, incorporating a three-layer mortise-and-tenon structure filled with 2.5 mm polyoxymethylene (POM) blocking particles. This configuration prevents particle rearrangement under load, ensuring consistent stiffness across different operating conditions—a key improvement over traditional particle-blocking methods.
Key takeaways
- The actuator combines a strain layer for pneumatic bending and a variable-stiffness layer controlled by negative pressure, enabling adjustable rigidity for different therapy sites.
- A Prandtl-Ishlinskii (P-I) hysteresis model, with parameters identified via the Levenberg-Marquardt algorithm, accurately captures the system's nonlinear behavior.
- A fast terminal sliding mode controller compensates for hysteresis and disturbances, reducing tracking errors compared to PID and adaptive control in simulations.
- Experimental prototypes, fabricated using 3D-printed molds, achieved predetermined bending angles and delivered physiotherapy forces up to 1.61 N, with stiffness-dependent force output.
This work offers a practical approach for integrating soft actuators into rehabilitation and massage robotics, where precise force and angle control are critical. The combination of mechanical design and advanced control could enhance the safety and adaptability of human-robot interaction in therapeutic applications.
Source: 《机器人》期刊 (robot.sia.cn) · Published 2026-03-15 · “受植物启发的变刚度理疗执行器设计与分析”