Adaptive Coordinated Motion Constraint Control for Cooperative Multi-manipulator Systems

A cooperative multi-manipulator system is a nonlinear, time-varying, strong coupling system with multiple inputs and outputs. Because of external disturbance, load change and other factors, a cooperative multi-manipulator system needs to address the problems of uncertain environment interaction, feasible control methods and coordinated planning. In this study, the coordinated motion of a multi-manipulator is divided into two types: coupling and superposition motions. An adaptive coordinated motion constraint scheme is proposed for the two different motion forms. The coupled and superposition motions were investigated by coordinating a carrying task and a circle drawing task, respectively, and the effectiveness of the adaptive coordinated motion scheme was verified. Based on the adaptive kinematics constraint algorithm of the multi-manipulator, co-simulation analysis of the multi-manipulator coordinated motion is conducted. Simulation results show that the multi-manipulator preserves the coordination relationship at all points of the trajectory planning path and has a good motion effect. Finally, an experimental platform for a cooperative multi-manipulator system was built to conduct experimental research on the coordinated motion of the multi-manipulator. Experimental results show that the proposed adaptive motion constraint control scheme for cooperative multi-manipulator systems has a good coordination effect, strong adaptivity and high-control precision.

A Novel Method of Prescribed Constraint Control Without Initial Condition of Nonlinear Systems

A novel constraint control strategy without initial condition of constrained variables is investigated based on backstepping technique for nonlinear systems. In this paper, the novel constraint control strategy is presented for a class of strict-feedback nonlinear systems with actuator saturation and external disturbances by using a nonlinear mapping and a novel performance constraint function. In this control strategy, there are two prescribed constraint functions, the design of these functions is not related to the initial conditions of the constrained variables. Unlike the existing constraint control method without initial condition, the proposed method gives a new solution. It can guarantee that the constraint variable gets into a prescribed constraint region from any initial value no later than a setting time. And the setting time is a design parameter, it can be set arbitrarily. A prescribed performance constraint tracking controller is designed in this paper. It can make that the tracking error of the nonlinear system is constrained to a given region no later than the given setting time, and the transient and steady state performance of the system are ensured. Finally, the proposed method is compared with the existing method, the effectiveness and superiority of the proposed method are demonstrated by two practical examples.