A minimalist underactuated architecture with one finger and one motor, achieving deterministic adaptive grasping. The tripartite advantages of single-motor drive + adaptive enveloping + positional determinism – finding the optimal balance between dexterity, cost, and engineering complexity for humanoid robot hands.
Features
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Underactuated minimalist architecture – one servo drives one finger
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Deterministic underactuation – balancing adaptability and position controllability
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Lightweight and modular design – suitable for integration into humanoid robot end effectors
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Flexible contact and transmission redundancy – improving grasping robustness
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Extreme cost control – BOM-friendly dexterous hand solution
Specifications
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Degrees of Freedom (DoF): Single finger: 2 DoF (proximal phalanx + distal phalanx), underactuated implementation； Whole hand: Right index and middle fingers each 2 DoF, thumb 1 DoF (rotation), total 5 DoF (two-finger opposing configuration)
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Load capacity: ≥1 kg
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Weight: Approx. 80–120 g (including housing and silicone pads, excluding servos); whole hand to be measured
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Dimensions: Approximately 1:1 adult hand scale, designed for humanoid robot end effectors
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Grasping range: Can grasp cylindrical objects of diameter 20–80 mm and irregular objects via adaptive enveloping
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Number of actuators: Only 1 servo per finger (index/middle finger each 1, thumb 1), total 3 servos
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Transmission form: Double four-bar linkage + ball-head link + torsional spring flexible constraint
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Contact protection: Silicone pads on fingertip/finger pad for anti-slip and cushioning
Cost
Total BOM cost for the whole hand (three fingers) is approximately 1230 RMB, mainly including:
| Servo | Cost |
|---|---|
| feetech hl-3915-c001 x2 | approx. 240 RMB each |
| feetech SCS2332-c003 | approx. 150 RMB each |
| Circuit board | approx. 450 RMB |
| 3D printing | approx. 150 RMB |
Assembly demonstration
See project files – demonstration video and assembly video.