Ultra-Low-Impedance Robotic Gripper for High-Bandwidth and Transparent Physical Interaction
2026-08-10 • Robotics
Robotics
AI summaryⓘ
The authors designed a new robotic gripper with three fingers that uses special motors and a simple gear system to make it both strong and easy to move. Their design puts the heavy parts close to the base to keep the moving fingers light. Tests showed the gripper can hold objects with decent force while staying sensitive and quick to respond, without needing extra sensors. This approach helps balance power, precision, and flexibility in robot hands.
robotic gripperdirect-drive motorsdifferential transmissiongrasping forcemechanical impedanceproprioceptionkinematic dexteritymotor inertiasensorless force estimation
Authors
Joon Lee, Ari Choi, Seokhwan Jeong
Abstract
Conventional robotic grippers often use high-ratio transmissions to generate grasping torque and external force sensors to measure physical interaction. High-ratio transmissions increase friction, reflected inertia, and mechanical impedance, while external sensors add hardware complexity. To address these trade-offs, this study proposes a novel 9-DOF, three-fingered Differential Direct-Drive (DDD) gripper that combines DD motors with a low-ratio (1:2) differential transmission. The mechanism centralizes actuator mass at the base to minimize moving-link inertia, while the differential architecture couples two motors in parallel to amplify torque during flexion. Experiments show that the prototype delivers a nominal grasping force of approximately 18 N and a fingertip force of 4.7 N, while maintaining a low motor contribution to system inertia (0.236%) and low passive mechanical impedance, with a maximum measured value of 50.1 N/m when the motors are unpowered. The proposed hardware addresses the trade-offs among torque, physical transparency, and kinematic dexterity, providing a foundation for high-bandwidth interaction and sensorless proprioceptive force estimation.