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Light-weight actuator and drive systems

The motor concept

Both the DLR-gripper and the joint drives of our light-weight robot make use of the same motor concept based on our own redesign of commercially available two-phase stepping motors of the ESCAP type. These motors were basically attractive for our light-weight goals because they show up

• very low rotor inertia (flat disc)
• small size, low weight (1,5 N) but relatively high torque (0,33 Nm), the rotor permanent magnets being integrated into a rare earth disc with large pdiameter
• high positioning accuracy (25 pole pairs).

All modern robot control approaches are based on commanding joint torques. Due to friction etc. this is not feasible with standard robots today. Thus we have developed an inductive torque-measurement system that may be seen as an integral part of the gearing system. The implementation of appropriate nonlinear joint torque feedback laws is in preparation.