Do Robots Really Need Anthropomorphic Hands? -- A Comparison of Human and Robotic Hands

Human manipulation skills represent a pinnacle of their voluntary motor functions, requiring the coordination of many degrees of freedom and processing of high-dimensional sensor input to achieve such a high level of dexterity. Thus, we attempt to answer whether the human hand, with its associated biomechanical properties, sensors, and control mechanisms, is an ideal that we should strive for in robotics-do we really need anthropomorphic robotic hands? This survey can help practitioners to make the trade-off between hand complexity and potential manipulation skills. We provide an overview of the human hand, a comparison of commercially available robotic and prosthetic hands, and a systematic review of hand mechanisms and skills that they are capable of. This leads to follow-up questions. What is the minimum requirement for mechanisms and sensors to implement most skills that a robot needs? What is missing to reach human-level dexterity? Can we improve upon human dexterity? Although complex five-fingered hands are often used as the ultimate goal for robotic manipulators, they are not necessary for all tasks. We found that wrist flexibility and finger abduction/adduction are often more important for manipulation capabilities. Increasing the number of fingers, actuators, or degrees of freedom is not always necessary. Three fingers often are a good compromise between simplicity and dexterity. Non-anthropomorphic hand designs with two opposing pairs of fingers or human hands with six fingers can further increase dexterity, suggesting that the human hand is not the optimum. Consequently, we argue for function-based rather than form-based biomimicry.

💡 Research Summary

The paper investigates whether robotic manipulators must emulate the human hand’s full anatomical complexity to achieve dexterous manipulation. It begins with a comprehensive overview of human hand biomechanics, detailing the joint hierarchy (carpus, metacarpals, MCP, PIP, DIP, and the saddle‑shaped TMC joint), the roughly 20 degrees of freedom, and the over‑30 intrinsic and extrinsic muscles that generate force through tendons. The authors emphasize that muscle redundancy and tendon coupling limit true independence of each joint, and that wrist mobility together with finger abduction/adduction (especially at the MCP) plays a pivotal role in overall hand versatility. The hand’s soft cover—muscle tissue and highly innervated skin—provides a high force‑to‑weight ratio (up to 662 N grip) and rich tactile feedback via four primary mechanoreceptors (Merkel, Meissner, Pacinian, Ruffini) plus proprioceptive organs (muscle spindles, Golgi tendon organs). This multimodal sensing occupies about 20 % of the somatosensory cortex and underlies fine object exploration, texture discrimination, and dynamic grip control.

The authors then compare a wide range of commercially available robotic and prosthetic hands. While many designs strive for five‑finger, fully actuated configurations, real‑world competition data (Amazon Picking Challenge, DARPA Robotics Challenge) reveal a dominance of simpler under‑actuated three‑ or four‑finger hands and even non‑hand solutions such as suction cups or body‑powered hooks. The review maps hand features to manipulation skill categories (grasp, rotate, insert, assemble) and quantifies “manipulable degrees of freedom”. Their analysis shows that increasing finger count or actuator number yields diminishing returns; instead, ensuring wrist flexibility and finger ab‑/adduction dramatically expands the reachable skill set.

A key finding is that a three‑finger architecture—two opposing fingers plus a supporting finger—offers a sweet spot between mechanical simplicity, control tractability, and functional dexterity. Moreover, non‑anthropomorphic configurations (e.g., two opposing pairs of fingers or a six‑finger layout) can outperform human‑shaped hands on specific tasks, suggesting that the human hand is not the optimal universal solution. Consequently, the authors advocate for function‑based biomimicry: design robotic hands by first defining the required manipulation tasks, then selecting the minimal set of joints, actuators, and tactile/force sensors needed to accomplish those tasks, rather than copying human anatomy wholesale. This perspective provides a practical roadmap for developing cost‑effective, robust manipulators that approach or exceed human‑level dexterity in targeted applications.