Equation (3) is the motion equation of actinomorphic soft robot. The content of unknown vector x is accord the current robot locomotion modal. Base on the result of locomotion modal analysis, there are three kinds of the unknowns: In condition one, the unknowns is all about the position information. In condition two, the unknowns include a set of friction forces of static arm and others are position of moving arm. In condition 3, by equaling the two static arms as one static arm with equivalent braced-force, the motion matrix dimension is reduced to (3m-1)×(3m-1). The unknowns are a set of forces of two static arm’s resultant friction and 3m-6 positions of moving arm. Hence, yielding the vector x as: