Trilateral localization algorithm is determined by measuring the global coordinates of known reflection plate and the distance between the AGV, to realize the positioning, as shown in figure 3-34, measurement for AGV to A, B, C three baffle distance for Ra, Rb, Rc, respectively is A, B, C three points as the center of the circle, Ra, Rb, Rc for the radius of circle, the position of AGV on the intersection of three circle, this method compared with triangulation not only fast, but also easier to implement.