Smart Material Robotic Leg Using FBG Sensors for Proprioceptive Controller

This letter presents the development of a smart robotic leg constructed with bioinspired 3-D printed bones, overlaid with carbon fiber reinforced polymer (CFRP). Quasi-distributed fiber Bragg gratings (FBGs) sensors are placed using the finite element method (FEM) and embedded into each limb of the leg to provide proprioception regarding environmental forces. Consequently, the construction of the robotic leg comprises femur, tibia, and foot segments interconnected by mechanical joints actuated by servomotors. Furthermore, the process of obtaining transfer functions and fine-tuning proportional–integral–derivative (PID) controllers is conducted using the Ziegler–Nichols method. However, the performance of the leg equipped solely with classic PID controllers exhibits limitations in executing certain movements, particularly under heightened environmental demands. Leveraging the linearity of the sensitivity response of smart limbs, a strain-to-applied-force ratio is obtained. Thus, a color map interface illustrates the real-time response of the leg to external forces. Finally, an adaptive control loop based on fuzzy logic is proposed to enhance the leg's control performance.