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Dual-encoder based robot joint torque measurement system

Listed on
2026-07-13
Robot-related Technology Robot Arm/Manipulator Sensing/Perception
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Dual-Encoder-Based Robot Joint Torque Measurement System with Reducer Eccentricity Error Compensation

This technology is a torque measurement system that precisely estimates joint torque by modeling and compensating for mechanical eccentricity errors within the reducer in a dual-encoder system—using both input and output encoders—and calculating the torsion angle from the angular deviation that occurs under load.

Existing robot joint torque measurement methods have faced structural limitations, such as the high cost of dedicated force/torque sensors, reduced joint stiffness in strain-gauge-based systems, and the low accuracy and difficulty of modeling reducer friction in current-based methods.

This technology proposes a method that models and stores mechanical eccentricity errors under no-load conditions using functions such as polynomials or Fourier series. During operation, it subtracts the compensation function value from the angular deviation to derive the pure torsion angle, which is then multiplied by the joint stiffness to calculate torque. It serves as an innovative solution for collaborative robots and precision assembly equipment, enabling precise force control without the need for expensive torque sensors.

Key Features:
  • A drive unit that generates driving torque and an output link that rotates by receiving the driving torque
  • An input-side encoder that detects the driving rotation angle and an output-side encoder that detects the output rotation angle
  • A torque calculation unit that determines the torsion angle based on the angular deviation between the driving rotation angle and the output rotation angle
  • Calculates joint torque after modeling and compensating for eccentricity errors that occur in a no-load state

This invention was developed with support from the Ministry of Trade, Industry and Energy for the development of deep reinforcement learning-based collaborative technology capable of intelligently responding to unstructured work environments, such as assembly tasks.

Korea University
Jae-Bok Song | Seo-Hyun Kim | Ji-Hoon Maeng
Document
Date of application:
2021-03-03
|
Patent registration number:
10-2425658
Industry
robot•automation
Technology
Robotics
Optics•Sensor
Country
Korea
Family Patent

N/A

Price
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