Flexible Shaft as Remote and Elastic Transmission for Robot Arms

Research on human-friendly robots focuses on safety through software and hardware. Hardware-based safety offers a significant advantage over software-based safety if an accurate hardware model is integrated into the solution. Design of elastic and off-joint actuation has established safety by hardware, where the inherent qualities of elastic and lightweight nature make the robot safe for interaction. Combining series elastic actuators with cable/belt pulley-based remote transmission offers inherently safe hardware design, albeit with increased design and modeling complexity. This paper introduces remote and elastic actuation as a single-element solution for robot arm design using a flexible shaft. The test-bench approach studies the remote and elastic effects of a flexible shaft-based transmission for a robot. A set of nine flexible shafts, differing in length and diameter, are used for benchmarking as 3-D surface empirical maps to facilitate their optimal selection for robot design. An example 3 Degree Of Freedom (DOF) robot arm using a flexible shaft as a remote and elastic actuator is designed and modeled. A low-level control based on a flexible shaft is proposed, backed by the experimental results.