Thesis of Ayad Al Dujaili

Fault Diagnosis and Fault Tolerant Control Design for Physically Linked 2WD Mobile Robots Systems

In harsh environments resulting from natural disasters or industrial accidents, reducing human interventions by increasing robotic operations is desirable. The main challenges to be considered are not only that the robots should be able to go over long distances and operate for relatively long periods, but also make the global system tolerant to actuators’ failures. In this thesis, to overcome these challenges, systems composed of multi-linked two-wheel drive (2WD) mobile robots are considered. The objective of these multi-robot systems is to asymptotically track a reference trajectory, despite the presence of actuator faults. In this thesis, we design original Fault Tolerant Control (FTC) schemes. Some of them are passive methods, i.e. robust control laws to given failures, and other ones are active FTC which include a Fault Diagnosis (FD) algorithm that detects, localizes and estimates the faults, and adapt the control actions to the faulty situations. Several passive FTC strategies are proposed to deal with the unknown failure pattern matrix in the dynamic control law. Firstly, multiple dynamic controllers are designed, each one aiming at compensating a specific combination of actuator faults; a switching mechanism selects the proper controller. Secondly, a control solution which is well-suited for n-linked robots (n≥ 2) is presented. The provided solution is based on transforming the considered model into the canonical chained form, then a recursive technique is used to derive the kinematic control law. Based on this, multiple dynamic controllers are designed considering all possible failure cases. From these dynamic controllers, an appropriate one is selected to generate the applied control signal by the control switching mechanism. Thirdly, in order to design a FTC for multi-linked 2WD robots with friction and actuator faults, the same kinematic control law is used, but another dynamic control which does not use the control switching mechanism is proposed. To cover all possible actuator failures and to deal with friction, a multi design integration based adaptive method is proposed. An active FTC scheme is designed where a nonlinear adaptive observer is used to estimate the actuator faults, which are modeled as multiplicative and additive faults changing the torque inputs on the wheels, and also to estimate the states of the system, making the non-measured states available for the feedback control law. The proposed active FTC scheme provides fault estimation and fault tolerance. Simulation results are presented all along the thesis to verify the validity of the proposed control algorithms and to show the performance of the FTC schemes.


Directeurs de thèse : COCQUEMPOT Vincent, EL BADAOUI EL NAJJAR Maan Rapporteurs : HOBLOS Ghaleb, MARX Benoit Examinateurs : TALJ Reine, MERZOUKI Rochdi

Thesis of the team defended on 19/03/2018