Variable Moment Arm-based Load Compensation Unit

Variable Moment Arm Load Compensation Unit with Constant Compensation Force via Wire Drum Geometry

This technology is a variable moment arm-based load compensation unit that mechanically offsets moment fluctuations caused by changes in external load positions by adjusting the geometric shape of a wire drum and the deformation of an elastic body.

Conventional counterweight methods increase equipment mass and reduce mobility, while standard spring methods struggle to maintain constant compensation force due to the nonlinearity between gravitational torque and elastic force as positions change. Additionally, methods using motors and sensors lead to higher costs and increased control complexity.

This technology proposes a design where the moment arm length from the wire drum's rotation axis changes according to rotational displacement, compensating for variations in the spring's elastic restoring force through the drum's geometric moment arm. It can be applied to wearable assistive devices and robot arms, achieving precise gravity compensation that maintains a constant force regardless of position.

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Key Features:

• A wire connected to an external load at one end, wound around the wire drum to transmit compensation force
• A wire drum with an outer surface capable of winding the wire, with the other end of the wire fixedly mounted
• A counter-elastic unit that undergoes elastic deformation during the rotation of the wire drum to generate an elastic restoring force
• A drum shape where the moment arm length at the point where the wire is wound changes according to rotational displacement