Smart Foot Based on FBG Integrated in Composite Material and Adaptive Fuzzy Controller

In this letter, we present the design and development of a smart foot using fiber Bragg gratings (FBGs) sensors embedded in carbon fiber-reinforced polymer (CFRP) due to its resistance, small dimensions, and immunity to electromagnetic interference. To manufacture the CFRP foot, a 3-D mold based on human anatomy is modeled and 3-D-printed to support the curvature maintenance while the curing process. Subsequently, four FBG sensors are embedded to monitor different equivalent parts of the human anatomy in the foot: calcaneus, metatarsal bones, proximal phalanges, and middle phalanges using the wavelength shift method. These signals provide proprioception for make-decision to control the movement of the robotic foot. As the actuator structure, a servo motor is developed to the ankle joint using a dc motor, to move the foot by steel cables. Given the nonlinear nature of the system due to the use of elastic components, including CFRP foot deformations and a mechanical drive system with springs cushioning, an adaptive fuzzy-proportional–integral–derivative (FPID) control strategy is presented. As a result, there is an improvement in proprioception for controllers through experiments with variations in load and movement in the system, suggesting a path for humanoid robots and active prosthetic feet.