Because the GPS signal is very bad in the indoor environment, it is difficult for the robot to rely on this technology to achieve indoor positioning. Although the navigation can be realized by locating known landmarks or special marks through optical camera or lidar sensor (LIDAR), the former has high requirements for light environment, while the latter module is expensive and very power consuming.
Given these limitations, scientists at the University of California, San Diego studied Wi Fi access points that have spread across most buildings for location navigation。 Using its own low-cost Wi Fi transceiver, the robot continuously sends and receives radio signals to these access points. The return signal it receives is specific to each access point and comes from a certain angle and distance - the latter depends on the length of time between the robot sending the signal and receiving the response.
By measuring how the angle and distance of each point signal change when the robot moves, the on-board computer can determine the current position of the robot relative to all access points. The camera can still be used, but it is mainly used for obstacle avoidance or recognition.
The system was tested on the first floor of an office building, in which a wheeled robot had to walk around the floor several times while crossing a narrow corridor in bright and dim light. It is found that the positioning and mapping functions of this technology are consistent with those provided by the system based on camera and lidar.
"We can use basically free Wi Fi signals for robust and reliable sensing in visually challenging environments. In these scenarios, Wi Fi sensing may replace expensive lidar and supplement other low-cost sensors, such as cameras," said Aditya Arun, a doctoral student in electrical and computer engineering.
The study, led by Professor Dinesh Bharadia, will be presented at the 2022 International Conference on Robotics and automation (ICRA) in Philadelphia this week.