Fault-tolerant Cooperative Control Strategy Research Articles

Fault-Tolerant Cooperative Control Design of Multiple Wheeled Mobile Robots

This brief investigates fault-tolerant cooperative control (FTCC) strategies for multiple differentially driven autonomous wheeled mobile robots (WMRs) in the presence of actuator faults during formation operation. First, for normal/fault-free cases and for preparation to the faults occurrence cases, an integrated approach combining input-output feedback linearization and distributed linear model predictive control techniques is designed and implemented on a team of WMRs to accomplish a formation task. Second, when actuator faults occur in one of the robots of the team, two cases are explicitly considered: 1) if the faulty robot cannot complete its assigned task due to a severe fault, then the faulty robot has to get out from the formation mission, and an FTCC strategy is designed such that the tasks of the WMRs team are reassigned to the remaining healthy robots to complete the mission with graceful performance degradation and 2) if the faulty robot can continue the mission with degraded performance, then the other team members reconfigure their controllers considering the capability of the faulty robot. Thus, the FTCC strategy is designed to re-coordinate the motion of each robot in the team. Within the proposed scheme, a fault detection and diagnosis unit using a two-stage Kalman filter to detect and diagnose actuator faults is presented. Then, the FTCC problem is formulated as an optimal assignment problem, where a Hungarian algorithm is applied. Moreover, a collision avoidance algorithm based on mechanical impedance principle is proposed to avoid the potential collision between the healthy robots and the faulty ones. Formation operation of the robot team is based on a leader-follower approach, while the control algorithm is implemented in a distributed manner. The results of real experiments demonstrate the effectiveness of the proposed FTCC scheme in different fault scenarios.

Real-Time Fault-Tolerant Cooperative Control of Multiple UAVs-UGVs in the Presence of Actuator Faults

This paper investigates fault-tolerant cooperative control (FTCC) strategy for a team of unmanned aerial vehicles (UAVs) and unmanned ground vehicles (UGVs) in the presence of actuator faults. When actuator faults occur in one or more of the UGVs, two cases are considered: 1) the faulty UGV cannot complete its assigned task due to a severe fault occurrence, it has to get out from the formation mission. Then, FTCC strategy is designed to re-assign the mission to the remaining healthy vehicles; and 2) the faulty UGV can continue the mission with degraded performance, then the other team members will reconfigure their controllers considering the capability of faulty UGV. Thus, the FTCC strategy is designed to re-coordinate the motion of each UAV-UGV in the team. FTCC problem is formulated as an optimal assignment problem, where a Hungarian algorithm is applied. Simulation results and real-time experiments are presented in order to demonstrate the effectiveness of the proposed FTCC scheme in different fault scenarios.

Fault tolerant cooperative control for multiple unmanned aerial vehicle systems with plugging operations

A tracking problem for a group of multiple unmanned aerial vehicle (Multi-UAV) systems with agent faults is investigated. A neighbouring rule-based cooperative control algorithm is proposed such that the Multi-UAV systems can follow the common reference signals in a fault free situation. Once in the presence of faults that change the dynamics of the agents, a fault tolerant cooperative control strategy based on the plugging operations (with a minor adjustment of connection) is employed in order to make each agent continue to follow the reference signals without increasing the number of weak points. Moreover, the utilised plugging operations do not need to reconfigure any individual’s self control law or stop the faulty agents. Simulation results show the effectiveness of the proposed methods.

Fault-Tolerant Cooperative Control of Multiple Wheeled Mobile Robots Under Actuator Faults

This paper investigates fault-tolerant cooperative control (FTCC) strategies for multiple autonomous differentially-driven wheeled mobile robots (WMRs) in the presence of actuator faults during formation operation. Initially, an integrated approach with a decentralized linear model predictive control (MPC) and an input-output feedback linearization is designed and implemented on a team of WMRs in order to accomplish a formation task under normal conditions (i.e., fault-free cases). The linear model of each robot with nonlinear dynamics is found through feedback linearization, while MPC is subsequently applied to the linear model of each robot to perform the formation control. When actuator faults occur in one of the robots of the team, the faulty robot is not able to complete its assigned task anymore due to the fault, and the faulty robot has to get out from the formation mission. An FTCC strategy is designed with the tasks of the WMRs team are re-assigned to the remaining healthy vehicles to still complete the mission but with graceful performance degradation. Formation operation of the robot team is based on a leader-follower approach, while the control algorithm is implemented in a decentralized manner. Simulation results are presented to demonstrate the performance of the designed algorithm in several fault scenarios.

Extremum Seeking Based Fault-Tolerant Cooperative Control for Multiagent Systems

We propose a novel fault-tolerant cooperative control strategy for multiagent systems. A set of unknown input observers for each agent are constructed for fault detection. Then a real-time adaptive extremum seeking algorithm is utilized for adaptive approximation of fault parameter. We prove that the consensus can be still reached by regulating the interconnection weights and changing the connection topology of the fault agent. A numerical simulation example is given to illustrate the feasibility and effectiveness of the proposed method.