If a user selects auto-follow mode, then the user interface shows an indoor map and marks the location of user and the
robot-car (Figure 4(b)). The location of the user and the robot-car is determined by the positioning algorithm. The
robot-car determines a suitable route from the robot-car's location to the user's location according to the location
information. If the ultrasound sensor detects an obstacle, then the robot-car will modify its original route to avoid the
obstacle. Figure 4(c) shows the manual control interface. There are five buttons to control the robot-!.9/*,2#ments as
follows: forward motion, backward motion, turn left, turn right, and stop. These control commands are transmitted via
the wireless network. Figure 4(d) shows the data query control interface. The user can find a list of historical commands for
both the auto-follow mode and the manual control mode