H∞RL

For autonomous mobile robots, it is important to identify the position where the robot located with high accuracy. Conventional two methods, dead reckoning method, and landmark method have following defects: 1) dead reckoning method estimates the position of the robot by counting the rotation of the wheels so that accumulation error of measurement is unavoidable, 2) landmark method requires to place the landmarks beforehand.

Proposing method called "Cooperative Positioning System (CPS)" enables to identify the positions of moving robots with high accuracy even on rough and/or unknown terrain by positive use of multiple robots. Fig. 1 shows an example of CPS, which uses three moving robots. When robot 3 come to the position P3, robots 1 and 2 measure azimuth and elevation angles θ1, θ2, φ1, and φ2 relative to the robot 3 and identify its position. Then, robot 1, for example, moves forward as indicated by the dotted line and stops then robot 2 and 3 measure the relative angles to the robot 1 in the same way as previous measurement. This motion and measurement is repeated until they reach the destination.

Photo. 1 shows our first prototype machine model CPS-I. The models have a mechanism consists of two laser scanner, one of them is the laser slit light scanner which scans horizontally, and another is the laser spot beam scanner which scans vertically to detect photo sensors equipped on other robots. Experiments demonstrated that the average of positioning accuracy was in an average 0.92 % of travel distance.

Photo. 2 shows second prototype machine model CPS-II. This model consists of one parent robot equipped with high accuracy laser range finder and capable of searching and tracing a corner cube mounted on the children robots. Experimental result showed that the positioning accuracy could be 0.12 % of traveling distance when 3 children robots were used.

Photo.3 shows third prototype machine model CPS-III. This model can move in outdoor environment. Experimental result of long distance measurement showed that, as shown in Fig. 2, the positioning accuracy could be 0.30 % for position and 0.40 degrees for attitude where total travel distance and maximum difference of elevation are 323.9 m and 10.2 m, respectively.