Joint control and end-effector control are the two most dominant control methods for robot arms within the robot learning literature. Joint control, while precise, often suffers from inefficient training; end-effector control boasts data-efficient training but sacrifices the ability to perform tasks in confined spaces due to limited control over the robot joint configuration. This paper introduces a novel action space formulation: End-Effector-Elbow (E3), which addresses the limitations of existing control paradigms by allowing the control of both the end-effector and elbow of the robot. E3 combines the advantages of both joint and end-effector control, offering fine-grained comprehensive control with overactuated robot arms whilst achieving highly efficient robot learning. E3 systematically outperforms other action spaces, when precise control over the robot configuration is required, both in simulated and real environments.
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