Research On Stability Hierarchical Control Method Of Redundantly Driven Mobile Robot Under Uncertain Network Delays

The field of mobile robots applications have expanded rapidly in recent years,but traditional two-wheel-drive mobile robots cannot meet the demands of high-speed,heavyduty scenarios.The redundant drive mobile robot with four-wheel steering has obvious superiority of operational stability,flexibility,carrying capacity,and ground adaptability.Under the network communication process,such mobile robots exist uncertain time delays.At the same time,it is difficult to take into account the four-wheel coordinated movement under redundant characteristics for conventional methods,which seriously affects the stability and accuracy of system control.In this regard,this thesis researches on the fourwheel redundant driving mobile robot and proposes a layered control method for stability under uncertain network time delays.The purpose of the method is to realize high-stability and high-precision control under four-wheel distributed coordination under four-wheel distributed coordination through time-delay stability yaw moment control and adaptive fault-tolerant control distribution.The specific content of this research thesis is as follows:Firstly,by analyzing the lateral dynamic characteristics of the redundantly driven mobile robot,a discrete dynamic model considering the time-varying uncertain network delay is established.At the same time,an uncertain network delay estimation scheme based on a flutter-free super spiral is designed.By constructing a sliding mode surface,the finite time convergence of the estimation error is ensured.On this basis,the framework of stability hierarchical control under uncertain network time-delay estimation is proposed.Furthermore,for the dynamic control problem of redundantly driven mobile robots under uncertain network time delays,a min-max robust predictive stability yaw moment controller is designed.On the one hand,the matrix polytope model of the uncertain system is used to quantitatively describe the uncertain terms introduced by the stochastic timevarying network delay.On the other hand,combined with the delay estimation,a robust predictive control algorithm based on min-max system is proposed.Specifically,by establishing the infinite time domain min-max robust performance optimization target and constructing linear matrix inequality,the optimal yaw rate and centroid side slip angle control law are obtained.Combining theoretical analysis and simulation,the feasibility and system progressive stability of the proposed algorithm are verified.Subsequently,for the distributed coordination problem of four-wheel independent driving and independent steering of redundant driving mobile robot,an adaptive faulttolerant control allocation algorithm considering actuator drive failure was presented.In particular,a four-wheel independent drive/brake mechanism allocation criterion is constructed and fault factors are introduced to characterize the actuators that drive faults.On this basis,a torque fault-tolerant allocation algorithm based on model predictive control is designed.Through online adjustment of model parameters and using rolling optimization and feedback correction,the fault-tolerant torque input sequence is optimized.The simulation test verifies the effectiveness of the proposed algorithm and the robustness of the closed-loop system when the redundant drive mobile robot actuator fails.Finally,an experimental test scheme is proposed.An experimental platform for a fourwheel redundant driving mobile robot is built and the performance test of the stability hierarchical control method is carried out.The results show that the proposed algorithm has good control robustness under time-varying uncertain network time delays.It has strong fault tolerance to the failure of the underlying actuators,which can ensure the stable control of redundantly driven mobile robots.