Consensus Control Of Nonlinear Multi-agent Systems With Different Constraints

With the wide application of wireless communication and networked technology in control theory,multi-agent system(MAS),which integrates sensing,communication,decision-making and actuator,has been widely concerned.Multi-agent systems can complete different tasks through coordination control.As the basis of coordination control,consensus has attracted much academic and industrial attention in recent years,in which lots of resources have been devoted to investigate consensus control problem.However,consensus of multi-agent systems faced with many difficulties due to the diversity of task requirements and the complex working environment.For example,the task space state in the industrial environment is generally difficult to measure;military tasks require higher consensus error precision and fast convergence speed;there often exist delays in network environment and uncertainties in system models.Therefore,for different mission requirements,it is particularly necessary to study how to achieve consensus control of MAS with different constraints,especially the consensus control of nonlinear MAS.Hence,combined with the idea of hierarchical control and advanced control strategy,this thesis studied the consensus control strategy of nonlinear multi-agent system with different constraints.The research work of this thesis mainly includes the following aspects:(1)For the consensus control problem of nonlinear MAS with unmeasurable velocity,a finite-time observer is firstly proposed based on the second-order sliding mode,which realizes the fast observation of velocity.Then,a distributed consensus controller is proposed based on the first-order sliding mode,in order to reduce the chattering of sliding mode controller,the boundary layer based and super-twisting algorithm based sliding mode controllers are further proposed,which improve the serious chattering problem in control inputs.Under the proposed observer and controllers,the nonlinear MAS can asymptotically achieve consensus without velocity information.(2)For the output consensus control problem of heterogeneous nonlinear MAS with unmeasurable state information,an internal reference model is firstly designed,which can achieve any desired consensus value.Then,an output consensus controller is proposed based on distributed parallel compensation and internal reference model framework,and then a necessary and sufficient condition is given,which improved output consensus condition.Under the proposed control law,the heterogeneous nonlinear MAS that described by T-S fuzzy model can achieve output consensus.(3)For the finite-time consensus control problem of nonlinear MAS with convergence error bounds constraint,a distributed consensus controller is firstly proposed based on barrier function.By using the nonlinear transform of convergence error bound into sliding mode function variable,a fast terminal sliding mode continuous surface is designed by a switching approach,then a distributed controller is proposed by fuzzy approximation and adaptive theory to realize consensus control with system uncertainties.Finally the finite-time consensus convergence condition is given through the Lyapunov method.(4)For the finite-time consensus control problem of nonlinear MAS with unknown time-varying communication delay,an auxiliary system is firstly designed according to the hierarchical control idea to pretreatment the neighbour information with unknown time-varying delay.Then the stable condition of the auxiliary system is given according to the finite-time small gain theorem.A distributed finite-time consensus controller is proposed by using the recursive Lyapunov function method to achieve finite-time tracking to the auxiliary system,and the stable gain condition is given.Under the proposed controller,the agents can achieve consensus and the robustness of the system to time delay is improved.(5)For the consensus based formation control problem of nonlinear MAS with uncertain system parameter and unmeasurable task space speed,a reference formation system is designed,in which the leader velocity is considered to be constant and time-varying,respectively.Then a consensus formation controller is designed based on the bearing rigidity theory,the stability conditions of the closed-loop cascade system using input and output characteristics of the system is analyzed.Then,we considered the task space speed be unmeasurable,in order to avoid directly designing the task space speed observer under the condition of parameter uncertainty,we designed a task space position observer instead and then achieve consensus formation control.Then consensus formation control problem based on bearing rigidity is solved,and the time-varying formation control of the nonlinear multi-agent system is realized.