7-DoF Robot Arm

A robot arm with one more joint than a 6-axis arm, letting the same hand pose be reached many ways.

A 7-DoF robot arm has 7 joints in series, one more than the 6 needed to fix an end effector's pose, which is called kinematic redundancy. The benefit is that infinitely many joint-angle combinations produce the same end-effector pose, so the controller can adjust the elbow position within the null space, meaning the part of joint motion that doesn't change the end-effector pose, to avoid obstacles, singular configurations, and joint limits, while also moving in a way closer to a human arm, since a human shoulder, elbow, and wrist together also have roughly 7 degrees of freedom. The tradeoff is that inverse kinematics no longer has a unique solution, requiring an extra parameter such as the arm angle, or numerical optimization, to pick one. Representative products include the Franka Panda/FR3, KUKA LBR iiwa, and Kinova Gen3; humanoid robots such as AgiBot's Expedition A2 also use 7-DoF arms.

ExampleThe DROID dataset was collected at multiple labs using Franka Panda 7-DoF robot arms.

Also called

7-Axis Robot Arm, Redundant Manipulator

Related

Kinematic Redundancy · Null Space · Swivel Angle · 6-Axis Robot Arm · Franka Emika Panda / Franka Research 3 · KUKA LBR iiwa

Sources

DROID: A Large-Scale In-the-Wild Robot Manipulation Dataset
Robotic arm - Wikipedia