rotation of the second frame 26 can drive the counterweight 19 to rotate together at that time the gravity center of the sensing ball will be changed in the plane perpendicular to the rotating shaft of the second frame and an eccentric force is produced correspondingly in this direction so that the sensing ball moves under the action of the eccentric force in particular when the second frame 26 rotates according to i direction as shown the sensing ball rolls in b direction and when the second frame 26 rotates according to ii direction the sensing ball rolls back and forth in a direction when the first frame 7 is kept static relative to the second frame 26 and they are in mutually perpendicular positions when the first frame 7 rotates it drives the second frame 26 to rotate together at that time the gravity center of the sensing ball will be changed in the plane perpendicular to the rotating shaft of the first frame 7 and an eccentric force is produced correspondingly so that the sensing ball moves under the action of the eccentric force in particular when the first frame 7 rotates according to iii direction as shown the sensing ball rolls in d direction and when the first frame 7 rotates according to iv direction the sensing ball rolls in c direction when two sets of drive systems are used to drive the first frame and the second frame respectively the sensing ball can move in four.