Robot vacuum cleaner

1.1 is a front view of a robot vacuum cleaner showing our new design;

1.2 is a rear view thereof;

1.3 is a left view thereof;

1.4 is a right view thereof;

1.5 is a top view thereof;

1.6 is a bottom view thereof;

1.7 is a front, right and top perspective view thereof;

1.8 is a rear, right and top perspective view thereof showing the robot vacuum cleaner in charging; and

1.9 is a rear, right and top perspective view thereof showing the robot vacuum cleaner in another way of charging.

Features shown within the broken lines form no part of the claimed design.