Design and fabrication of an affordable, high-performance life-size humanoid robotic hand with integrated nanocomposite strain sensors

Abstract This paper presents the design and fabrication of Fil3D-Hand, a humanoid robotic hand with five fingers integrating nanocomposite filament strain sensors to monitor finger movements. The objective is to replicate the functionality of the human hand through an affordable design, with potential applications in humanoid robotics and prosthetic rehabilitation. Based on the investigation of the human hand’s anatomical structure and existing robotic hands, the mechanical design of Fil3D-Hand is elaborated. The kinematics analysis and finger workspace are formulated and illustrated using the Denavit-Hartenberg (D-H) convention and numerical simulations. The proposed design features 17 degrees of freedom, weighs 2.4 kg (including the forearm and 12 servo motors), and achieves a fabrication cost of less than $350. The Fil3D hand’s size is approximately 1.2 the size of the real human hand, allowing for enhanced versatility while maintaining a naturalistic appearance. This design strategy ensures a cost-effective, tendon-driven underactuated mechanism, utilizing servo motors for precise control of finger joints. It also integrates 14 filament strain sensors for accurate monitoring of finger positions. Experimental results demonstrate the performance of these sensors, revealing a highly linear correlation ( $$ R^2 = 0.9964 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>R</mml:mi> <mml:mn>2</mml:mn> </mml:msup> <mml:mo>=</mml:mo> <mml:mn>0.9964</mml:mn> </mml:mrow> </mml:math> ) between the finger’s proximal angles and the strain sensor resistance, guaranteeing precise real-time monitoring of finger movements. Evaluation of the Fil3D-Hand’s performance highlights its excellent grasping capabilities, showcasing its potential in practical applications.