Control Methods Of Nonlinear Multi-agent Systems With Nonsmooth Actuator Constraints

Multi-agent system(MAS)has been widely concerned in military,industrial and agricultural fields,such as formation cruise,intelligent transportation,intelligent logistic and geographic information acquisition.In practical application,MAS is characterized by uncertainty and nonlinearity due to unknown external disturbance and parameter perturbation.In addition,it is due to the diversities on working environment and task requirements that the cooperative control of MAS is limited by performance constraints.In order to achieve the high-performance control of nonlinear MAS,this paper focuses on performance constraints which nonlinear MAS with nonsmooth actuator constraints may suffer,such as the prescribed bounds of errors and finite-time convergence.By integrating the existing intelligent control strategy,distributed control algorithms are designed to satisfy the actuator constraints and performance constraint.The main research contents of this paper are as follows.(1)For uncertain nonlinear MASs with unknown dead zones and faults in one-way communication networks,a distributed control scheme is designed to solve the problem of consistent tracking control.Neural network is used to approximate uncertain function.A bound estimation method is used to estimate the maximum effects of unknown dead zones and faults.Based on the distributed backstepping technology,a distributed consistent tracking control scheme is proposed.This scheme can ensure that each follower with unknown dead zones and failures will uniformly track the leader.(2)For heterogeneous uncertain nonlinear MASs with unknown input constraints,a distributed finite-time control scheme is designed to solve the problem of finite-time uniform tracking control.A general input constraint model is proposed by summarizing the characteristics of common actuator constraint models.In order to realize the finite-time dynamic tracking of heterogeneous followers with unknown input constraints,a distributed finite-time consistent tracking control scheme is proposed by combining fraction-order feedback method and neural networks.On this basis,by changing the fraction-order feedback coefficient,this scheme is further extended to non-finite time consistent control.(3)For second-order uncertain nonlinear MASs with time-varying dead zones in one-way communication network,a distributed fixed-time control scheme is designed to solve the problem of fixed-time consistent tracking control.In order to compensate the time-varying dead zone in a fixed time,a bound estimation method is introduced to estimate the dead-zone effect,and a fixed-time adaptive law is designed.According to the characteristics of system uncertainties,two distributed fixed-time consistent tracking control schemes are proposed respectively by using neural network and some ingenious processing methods.Under the proposed control schemes,all the followers with time-varying dead zones can track the leader with sufficient precision within a predetermined time.(4)For high-order uncertain nonlinear MASs with time-varying faults in one-way communication networks,a distributed smooth fixed-time control scheme is designed to solve the problem of smooth fixed-time consistent tracking control.By designing smooth switching and adopting dynamic surface control,a distributed smooth fixed-time control framework is proposed to completely eliminate singularities and chattering problems.In order to realize the fixed-time compensation of time-varying faults under the smooth fixed-time control framework,based on the bound estimation method,two continuous adaptive laws are designed.Then,a smooth fixed-time fault-tolerant uniform tracking control scheme is proposed to ensure that all control signals are continuous,smooth and bounded.(5)For uncertain nonlinear MASs with unknown hysteresis in one-way communication networks,a distributed prescribed-time control scheme is designed to solve the problem of prescribed-time containment control.Firstly,a prescribed-time convergence technique is proposed to achieve convergence of error and reduce overshoot.Then,by using fuzzy logic system approximate unknown continuous function in the process of controller design and introducing Nussbaum function to deal with the direction of actuator hysteresis,a distributed prescribed-time containment control scheme is put forward to ensure that each follower with unknown hysteresis converges to a convex hull with prescribed precision in prescribed time.