Robot arm equipped with a gravity compensation device

Gravity-Compensated Robot Arm Combining a Dual Parallel Four-Bar Linkage and a Spring Counterbalancer

This technology is a robot arm equipped with a gravity compensation device that places an elastic member-based counterbalancer on the pitch joint of a multi-degree-of-freedom robot arm, linking it with a parallel four-bar linkage structure to mechanically offset gravity torque caused by self-weight and secure the joint's range of motion.

Existing parallel four-bar linkage-based gravity compensation devices have technical limitations, such as a range of motion restricted to less than 180 degrees due to dead-point issues, and wire or belt-based systems that suffer from poor durability and reproducibility.

This technology proposes a method that utilizes a dual parallel four-bar linkage mechanism and configures a counterbalancer module—including a connecting rod, slider, guide bar, and spring—on the first and second links, respectively, to compensate for gravity torque during link rotation using the spring's restoring force. It can be applied to industrial robot arms and collaborative robots, significantly reducing actuator capacity and energy consumption while expanding the range of motion.

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Key Features:

• A second link main body and a second link joint body connected to the first link via a first pitch joint
• A third link connected to the second link via a second pitch joint, forming a dual parallel four-bar linkage
• A first pitch joint drive unit supported by the first link to rotate the second link
• A counterbalancer including a connecting rod, slider, guide bar, and spring to offset gravity torque during link rotation

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This invention was developed with support from the Ministry of Trade, Industry and Energy for the development of next-generation manufacturing robot technology for workspace sharing and smart factory applications.