“…Assume each robot has one neighbor at least. According to Lemma 1, we propose a collision avoidance algorithm based on [10], [11], [14]- [16], [19], which consists of 6 steps: (1) Positions P ci (x ci , y ci ) in initial group are separated into .. = y f i+j , all of these positions P f i , P f i+1 , ...P f i+j in each set of final group are reordered according to x f i , and at the same time the positions with the same subscripts P ci , P ci+1 , ...P ci+j in the associated set of initial group also are reordered according to x ci . (4) Similar to (3), if y ci − y ci+k < ε, (k = 1, ..., j), P ci , P ci+1 , ...P ci+j of each set are reordered again according to x ci , and P f i , P f i+1 , ...P f i+j coordinated positions in final group are also reordered according to fig.…”