Prescribed time tracking control without velocity measurement for dual-arm robots

This paper studies the prescribed time control of dual-arm robots without velocity measurement. Firstly, according to the position/force constraint relationship between the dual arms and the grasped object, the comprehensive dynamic model is established with the object position in Cartesian space, then the system motion model independent of the internal force is obtained. Secondly, a settling-time regulator related to convergence time and tracking accuracy is constructed, then the prescribed time tracking problem boils down to the output error constraint problem. Furthermore, a new constraint transformation function is introduced to change the output error constraints to ensure the boundedness of the new error variables. Finally, combined with the velocity observer and backstepping technique, the position controller and hybrid position/internal force controller are designed respectively. The remarkable features include: (1) Both position control and internal force control are considered, which is helpful to realize the coordinated movement of the dual-arm system and the stable grasping of the object; (2) There is no requirement to measure the velocity of the object, which avoids the expensive velocity sensor and its interference; (3) Compared with the existing control methods, the convergence time and tracking accuracy in the position control can be preset manually.