Design and Evaluation of Haptic Interface Wiggling Method for Remote Commanding of Variable Stiffness Profiles

Unlike many traditional stiff position-controlled robots, new collaborative robots interact with humans and operate in an environment that is often unpredictable and unknown. For safe and effective executions of manipulation tasks within such an environment, the robot requires to modulate its compliance. Therefore, the human operator must have a system that enables an intuitive demonstration of compliance skills to the robot. Ideally, this should also be possible through teleoperation in order to have the ability to demonstrate skills at a distance, such as in remote home care applications or any other scenario where the skilled operators are not physically present all the time. Existing state-of-the-art methods for remote demonstration of impedance skills only enable limited modulation of the stiffness matrix, or they are too complex and cumbersome for practical applications. This research tries to overcome these limitations and proposes a teleoperated stiffness commanding method that enables a complete modulation of the stiffness matrix in 3 degrees of freedom. The method uses the same haptic device hardware as used for controlling the robot manipulator motion, hence it does not require extra specialised equipment for stiffness commands. By wiggling the endpoint of the haptic device, the stiffness is commanded to the robot and also fed back to the operator through haptic and visual feedback. To evaluate the performance and acceptance of the system, we performed a user study where the participants had to demonstrate various interaction behaviour to the remote robot. The results show how varying system parameters (i.e., degrees of freedom, orientation, and size of the stiffness commands) influence the performance of the system and user acceptance.