Design and Control of an Innovative Hydraulic Underactuated Hand (Hyd-U Hand) Based on a Neural Network Inverse Model Feedforward Controller

For biomedical and rescue applications, this paper presents the Hyd-U hand, a compact, hydraulically actuated underactuated robotic hand designed to enhance payload capability in dexterous manipulation. With a payload-to-weight ratio of 22.14 (16,kg payload, 722.6,g self-weight), it is ideal for applications requiring high force and low weight, such as field rescue and mobile robotics. The system integrates three key innovations: •Electro-hydraulic underactuation: Combines a single-acting hydraulic cylinder with truss-pulley transmission and cable-driven fingers to enable sensor-free adaptive grasping •Hybrid PID-NNIM control: Implements neural network inverse modeling (NNIM) with PWM current sensing to achieve μ0.05 mm displacement precision •Embedded high-force manipulation: Miniaturized servo driver enables responsive operation in unstructured environments Experimental results demonstrate the Hyd-U hand's stable grasping of objects with varying shapes and weights, showcasing its repeatability and responsiveness in dynamic, unstructured environments.