In the rapidly evolving field of humanoid robotics, the dexterous hand serves as a critical functional terminal, enabling complex interactions and tasks. As a researcher deeply involved in this domain, I have observed that while significant progress has been made in enhancing the practical performance of humanoid robotic hands—such as grasping and manipulation—their morphological expression remains undervalued. Morphology is not merely about external appearance; it is intrinsically linked to internal structure and plays a pivotal role in human-robot interaction by influencing visual perception and emotional connection. This article presents an innovative morphological design method for humanoid robotic hands, leveraging artistic anatomy principles to bridge the gap between aesthetic appeal and engineering functionality. By employing Kansei engineering for quantitative analysis of perceptual descriptors, establishing aesthetic templates, and facilitating engineering transformation, this approach integrates art and science to achieve a harmonious balance in humanoid robot hand design.
The current landscape of humanoid robotic hands is dominated by functional priorities, often resulting in bulky, disproportionate, and structurally unrealistic forms. For instance, many existing dexterous hands exhibit issues like oversized dimensions and distorted proportions when compared to the human hand, which typically measures around 190 mm in length for adult males. This misalignment not only detracts from visual appeal but also hinders the establishment of natural emotional bonds with users. In my work, I have identified a significant research gap in morphological design methodologies for humanoid robots, where subjective aesthetic evaluations are seldom quantified or integrated into engineering processes. Traditional industrial design approaches often prioritize functional modules first, leading to compromises in aesthetics. However, the fusion of artistic aesthetics and technological advancements is essential for creating humanoid robotic hands that are both highly functional and visually pleasing.
To address these challenges, I developed a method that draws on artistic anatomy principles, which abstract and generalize the structural and dynamic relationships of the human hand. This method involves a systematic process of quantitative analysis, template construction, and engineering translation. The core idea is to translate the abstract notions of beauty and affinity into measurable engineering parameters, ensuring that the humanoid robot hand not only performs reliably but also resonates with users on an emotional level. The following sections detail this methodology, including the use of surveys, hierarchical analysis, and the creation of a standard hand aesthetic template, all aimed at achieving high anthropomorphic fidelity in humanoid robotic hands.
The first step in this process was to conduct a quantitative analysis of perceptual descriptors using Kansei engineering. I designed a survey model based on existing dexterous hand samples to evaluate morphological performance, focusing on attributes like “beauty and affinity.” In the survey, 30 participants rated eight hand samples on a five-point Likert scale, ranging from -10 (no beauty or affinity) to 10 (excellent beauty and affinity). The results indicated overall low scores, highlighting the need for improvement. From this, I extracted higher-rated samples for a second round of testing, which identified key factors influencing morphological evaluation: proportion, appearance, construction, and motion bionics. These factors collectively point to a high degree of anthropomorphic imitation, underscoring the user’s reference to the human hand as a benchmark for humanoid robot design.
Using hierarchical analysis, I derived a structured framework for engineering transformation. The base layer emphasized “beauty and affinity” and “high anthropomorphic fidelity,” while subsequent layers broke down into indicators like proportion, appearance, construction, and motion bionics. This led to the identification of critical engineering challenges, such as high-density integration of drive systems in compact spaces. The hierarchical analysis table below summarizes this derivation process:
| Layer | Description |
|---|---|
| Base Layer | Beauty and Affinity, High Anthropomorphic Fidelity |
| Indicator Layer | High Integration |
| Decomposition Layer | Proportion, Appearance, Structure |
| Element Layer | Proportion, Appearance Modeling, Construction, Motion Bionics |
| Cognition Layer | Artistic Anatomy Abstraction Methods |
| Guidance Layer | Proportional Relations and Aesthetic Template, Hard Materials, Non-Contrasting Colors, Anthropomorphic Forms and Joint Structures, “Dexterity,” Direct Force Transmission, Built-In Drive |
| Expansion Layer | Golden Ratios for Hand and Parts, Balanced Male-Female Hand Features, Abstract Translation of Geometric Joint Axes, Simulation of Muscle-Tendon Stretch, Simulation of Bone-Joint Motion |
| Technical Layer | Finger Length, Palm Length and Width/Thickness, Finger Segment Length and Diameter Trends, Palm Arc and Surface Curvature, Male Hand Robustness, Female Hand Slenderness, Non-Orthogonal Joint Axes to Orthogonal Transformation, Freedom Degree Mapping, Abstract Structures like Links and Levers, Full Active Distributed Drive, Simulation of Independent Functions, Simplification of Complex Joint Motions to Rotational Forms |
| Indicator Layer | Detailed Data Extraction, Verification, and Calibration |
This framework enabled the translation of subjective aesthetic criteria into objective engineering targets, with a focus on minimizing the size of the humanoid robot hand while maintaining functionality. For example, the drive system integration was identified as a major bottleneck, requiring innovative solutions to reduce dimensions without compromising performance.
Next, I constructed a standard hand aesthetic template using 3D digital modeling, guided by artistic anatomy principles. This template balanced male and female hand characteristics to achieve a universal aesthetic form, with a target length of 190 mm to match the average adult male hand. The template incorporated proportional data derived from artistic anatomy, such as the golden ratio, to define the relationships between different hand parts. The mathematical expression for proportion can be represented as: $$ \frac{L_{\text{palm}}}{L_{\text{finger}}} = \phi \approx 1.618 $$ where \( L_{\text{palm}} \) is the palm length and \( L_{\text{finger}} \) is the finger length, following the golden ratio \( \phi \). This approach ensured that the humanoid robot hand exhibited a harmonious and natural appearance, reducing the subjective bias often associated with aesthetic design.
The aesthetic template also addressed the integration of engineering constraints, such as structural stability and operational precision. By abstracting the complex biological structures of the human hand—like bones and tendons—into simplified geometric forms, the template facilitated the transition to manufacturable entities. This abstraction is crucial for humanoid robot hands, as it allows for the replication of key functionalities without the need for exact biological mimicry. The template served as a foundational model for subsequent design and manufacturing phases, ensuring that aesthetic integrity was maintained throughout the engineering process.
In the design and manufacturing phase, I focused on overcoming the challenge of high-density drive system integration within a compact space. This involved several key steps, each informed by artistic anatomy principles. First, I translated the complex motions of the human hand into engineering-friendly mechanisms. For instance, the “rolling + sliding” motion of human hand joints was abstracted into pure rotational movements, which are easier to implement in a humanoid robot hand. The kinematic transformation can be described by: $$ \theta_{\text{joint}} = f(\alpha, \beta) $$ where \( \theta_{\text{joint}} \) represents the joint angle, and \( \alpha \) and \( \beta \) are parameters derived from the abstraction of biological motion. This simplification allowed for the use of axis-based mechanisms, reducing volume and manufacturing complexity while preserving essential functionalities.
Second, I addressed the non-orthogonal joint axes of the human hand by extracting critical motion features—flexion-extension and abduction-adduction—and converting them into orthogonal geometric states. This transformation enabled the mapping of human hand joints to engineering joints, resulting in a total of 22 degrees of freedom (DOF) for the humanoid robot hand. The DOF distribution included 6 orthogonal joint axes for dual DOF and 10 axis-rotation joints for single DOF, all driven by 22 motor modules in a fully active, distributed manner. Compared to existing humanoid robot hands like Tesla Optimus, which uses a combination of active and passive drives, this design offers superior precision and eliminates coupling interference. The DOF mapping can be summarized as: $$ \text{Total DOF} = \sum_{i=1}^{6} \text{Dual DOF}_i + \sum_{j=1}^{10} \text{Single DOF}_j = 22 $$ This high level of articulation allows the humanoid robot hand to mimic human hand movements with remarkable accuracy, enhancing both functionality and visual realism.
Third, I implemented avoidance processing inspired by joint decoupling characteristics. In the human hand, joints operate independently to achieve precise motions, a feature replicated in the humanoid robot hand through multi-motor drives. To prevent interference between components, I designed avoidance mechanisms at joint areas, such as isolating the fifth metacarpal to allow inward flexion during grasping. This not only improved the bionic posture but also enhanced the overall aesthetic by maintaining smooth, continuous curves. The avoidance design can be modeled using geometric constraints: $$ d_{\text{min}} \geq \delta $$ where \( d_{\text{min}} \) is the minimum distance between moving parts, and \( \delta \) is a safety threshold to prevent collisions. This approach ensured that the humanoid robot hand could perform complex gestures without mechanical issues, contributing to its lifelike appearance.
Fourth, I integrated mechanisms and electromechanical systems to achieve bionic mimicry. For example, I designed joint motion chains inspired by artistic anatomy, using “mortise-and-tenon” configurations to map joint morphology and function. This design improved visual coherence, addressing common issues like “awkward joints” noted in user surveys. The electrical wiring layout was optimized based on human ligament distribution, increasing internal space utilization and visual harmony. The compact arrangement of drive units—integrating custom servo motors and reduction mechanisms—enabled the equivalent of muscle-tendon system dynamics. The performance metrics of the resulting humanoid robot hand, named Dexterous Hand A, are summarized in the table below, compared to other leading products:
| Product | DOF | Drive Method | Sensing | Output Force | Speed | Precision | Sensitivity |
|---|---|---|---|---|---|---|---|
| Shadow Hand | 20 Active, 4 Passive | Distributed, External | Tactile | N/A | N/A | N/A | N/A |
| DexHand | 12 Active, 8 Passive | Centralized + Distributed, Internal | Tactile | 15 kg | N/A | N/A | N/A |
| Tesla Optimus | 17 Active | Centralized + Distributed, Internal | Vision, Tactile | N/A | N/A | N/A | N/A |
| Dexterous Hand A | 22 Active | Distributed, Internal | Dynamic Tactile Array (DTA) | 20 N per Fingertip | 4 Hz/s | 1 mm Spatial Resolution | 6,000 Pressure Levels, 180 Hz Frame Rate |
As shown, Dexterous Hand A excels in size, full active DOF, dynamic tactile sensing, and distributed internal drive, positioning it as a leading solution in humanoid robot hand design. The integration of electronic skin further enhanced its realism, with considerations for curvature changes and strain thresholds to ensure stress-free application.
Upon completion, Dexterous Hand A was evaluated through a follow-up survey using the same semantic differential method. Twenty participants rated it alongside previously high-scoring samples, and it achieved significantly higher scores in “beauty and affinity,” validating its superior morphological performance. The hand was officially unveiled at the IEEE International Conference on Robotics and Automation (ICRA 2025), where it received widespread acclaim for its aesthetic and functional advancements. This recognition underscores the success of the artistic anatomy-based approach in creating a humanoid robot hand that meets dual high standards of aesthetics and engineering.
In conclusion, the morphological design method presented here, rooted in artistic anatomy principles, enables a synergistic integration of art and technology for humanoid robotic hands. By quantifying aesthetic perceptions and translating them into engineering strategies, this approach bridges the gap between subjective beauty and objective functionality. Future work should expand the research scope, refine methodologies, and conduct long-term dynamic studies to further advance humanoid robot hand design. This method not only enhances the visual appeal of humanoid robots but also fosters more natural and empathetic human-robot interactions, paving the way for broader applications in fields like healthcare, manufacturing, and service robotics.