Consensus And Formation Control Of Underactuated Multi-robot Systems

The underactuated robots are the robots which have less control inputs than the degree of freedom dimension,they are widely existed in civil,military,nuclear industry and aerospace and other fields.Due to the advantages of underactuated robots,such as light weight,low energy consumption and high flexibility,the control research is of great significance.According to the diversity of underactuated robots,it is difficult to find a common control method suitable for all underactuated systems,so that the researchs on underactuated robots mainly focus on one kind of system.At present,most researches on multi-robot systems are based on the full actuated linear or simple nonlinear systems.In this paper,we take two classical underactuated models of the underactuated robotic arm based on the Lagrangian model and the quadrotor aircraft as examples,aimming at the consensus and formation control problems of underactuated multi-robot systems,the main works are as follows:Firstly,finite time control for the underactuated robotic arm with uncertainties is investigated.Based on the idea of terminal sliding mode and the linear transformation method,finite time extended state observer is proposed to estimate the system uncertainties.By introducing the adaptive control,the modified nonsingular terminal sliding mode controller is proposed to make the underactuated robotic arm achieve finite time stability.Meanwhile,combined with the high gain observer,the output feedback controller with multi-time-scale structure is designed for the quadrotor aircraft with uncertainties,so that it can reach finite time stability.Secondly,finite time consensus for the underactuated multiple robotic arm systems is investigated.An adaptive finite time consensus control strategy is proposed,which is independent from the imformation of the system model and becomes insensitive to the high frequency disturbance,so that it has a stronger applicability and robustness.The stability analysis is presented based on Lyapunov stability theory and the adding a power integrator technique.Thirdly,considering about the limited communication resources in the non-ideal communication network,event-triggered finite time consensus control strategy is designed for the underactuated multiple robotic arm systems,which is based on the event-triggered control mechanism and the idea of integral sliding mode control.Event-triggered finite time bounded consensus of underactuated multiple robotic arm systems is obtained,which not only can save the communication energy,but also reduce the trigger frequency of the controller.Meanwhile,the parameter setting method for high performance consistency control is presented according to Lyapunov stability theory and Zeno behavior is excluded absolutely.Then,combined with an extended high-gain observer with two-time-scale structures,an effective distributed formation control strategy is designed for a group of quadrotor aircrafts.According to the singular perturbation method and integral sliding mode technique,it can impel multiple quadrotor aircrafts to track the desired trajectory and achieve a predesigned formation shape,which provides the stability analysis of each subsystem.Finally,considering about the time-varying formation control problem of multiple quadrotor aircrafts,a dynamic event-triggered control strategy is proposed based on the singular perturbation theory,which is ensure to achieve formation while acquiring satisfactory resource efficiency.The system stability in each time scale is presented and Zeno behavior is excluded.Compared with the static event-triggered mechanism,it can make a tradeoff between high-performance formation control and reducing the number of triggered events.