Expansion and optimization of the CoaxHaptics-3RRR system through the integration of a gripper mechanism

Kurzfassung

This work presents the expansion and structural optimization of the CoaxHaptics-3RRR, a haptic interface developed at the German Aerospace Center (DLR) based on a Spherical Parallel Manipulator (SPM). The primary objective is to integrate an additional degree of freedom (DoF) in the form of a gripping mechanism to provide the operator with active haptic feedback.

Initially, the technical and ergonomic requirements for the integrating of the gripping mechanism are specified. Accordingly, a concept for the optimization and integration of the actuation system and the redesign of the key elements of the CoaxHaptics-3RRR device has been developed. This includes the introduction of a novel design variant of a cardan joint, the Hollow Cardan, which enables torque transmission from the base to the end-effector for the newly integrated gripping DoF. Additionally, it facilitates continuous torque transmission when the end-effector is tilted within its workspace.

Based on the optimized design, two gripper interfaces are developed: a rotational gripper and a linear gripper. Both designs incorporate a capstan drive, a cable-based mechanism for low friction and backlash-free torque transmission.

Finally, the design of the CoaxHaptics-3RRR device has been expanded and optimized. This device is manufactured and assembled in a functional demonstrator that exhibits low friction and low inertia behavior, as well as increased structural integrity.