Before revision:  Then the temperature of the water pipe is controlled by a heat source and a small water pump .  Besides, an observer for estimating heat flow is implemented;
After revision:  Then the temperature of the water pipe is controlled by a heat source and a small water pump . We focus on the thermal cue because previous human studies have identified it as part of the touch pleasantness. The robotic cover surface can be regulated to the desired temperature by circulating water through a thermally conductive pipe embedded in the cover, of which temperature is controlled. Besides, an observer for estimating heat flow is implemented;