Robot Joint Unit

Robot Joint Unit with Suppressed Torque Ripple Using Cross-Roller Bearings and Spoke Structure

This technology is a robot joint unit that accurately measures output torque by placing a torque sensor between the flexspline and the output section of a harmonic drive, while supporting the base and output sections with cross-roller bearings to suppress deformation caused by external forces and crosstalk resulting from torque ripple.

When using harmonic drive reducers, it has been difficult to accurately measure joint output torque due to torque ripple caused by input rotation speed and torque sensor deformation from external moment loads.

This technology proposes a method that places cross-roller bearings between the base and output sections to support external forces, and uses a Wheatstone bridge configuration to process signals from multiple spokes and sensor gauges arranged at 90-degree intervals to cancel out torque ripple. It can be applied to force-controlled joints in collaborative robots, providing reliable torque signals even in environments with external disturbances.

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Key Features:

• A drive unit including a base and an input shaft disposed on the side of the base to receive input torque from a motor
• A harmonic drive reduction unit that receives input torque from the input shaft and increases torque through reduction
• An output unit that converts the reduced torque received from the reduction unit into output torque and rotates to output it externally
• A torque sensor disposed between the output unit and the reduction unit to precisely detect the output torque on the output unit side

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This invention was developed with support from the Korea Institute for Robot Industry Advancement under the Ministry of Knowledge Economy for autonomous intelligent manipulation for service robots.