Transfer Depends on Acquisition: Analyzing Manipulation Strategies for Robotic Feeding

Successful robotic assistive feeding depends on reliable bite acquisition and easy bite transfer. The latter constitutes a unique type of robot-human handover where the human needs to use the mouth. This places a high burden on the robot to make the transfer easy. We believe that the ease of transfer not only depends on the transfer action but also is tightly coupled with the way a food item was acquired in the first place. To determine the factors influencing good bite transfer, we designed both skewering and transfer primitives and developed a robotic feeding system that uses these manipulation primitives to feed people autonomously. First, we determined the primitives' success rates for bite acquisition with robot experiments. Next, we conducted user studies to evaluate the ease of bite transfer for different combinations of skewering and transfer primitives. Our results show that an intelligent food item dependent skewering strategy improves the bite acquisition success rate and that the choice of skewering location and the fork orientation affects the ease of bite transfer sianificantly.