This paper extends the constrain-move strategy for four robots lifting an object in a distributed manner. Ahmadabadi et al. (1996, 1998) have successfully applied constrain-move to three robots, but due to existence of redundancy in vertical forces in a team of four robots, this protocol is not applicable to such systems in its original form. In the presented cooperation strategy, the robots support the load on its bottom face and there is no lateral artificial constraint on the object. The distributed coordination protocol is designed in such a way that with minimum volume of communication and implementing their own local sensors, the robots can lift the object while its Euler angles and robot-object contact are controlled. Stability condition for the system is attained mathematically. Simulation results are given to support the applicability of the presented system.
['Majid Nili Ahmadabadi', 'Shaahin Mehdinezhad Rushan', 'Zhi-Dong Wang', 'E. Nakano']
A constrain-move based distributed cooperation strategy for four object lifting robots