Real Implementation of Fault-Tolerant Control via Synchronous Methodology for Robot Manipulators

Abstract

During the past few decades, fault-tolerant control has been introduced to enhance safety and acceptable performance when faults occur in the system. In this dissertation, a real implementation of fault estimation (FE) and fault-tolerant control (FTC) for a robot manipulator based on synchronous technique is presented. First, the forward kinematics of the robot manipulator was investigated, and then, inverse kinematics problem was studied using both Pieper and numerical methods. In this study, Lagrangian method was used for the dynamic model of robot manipulator which plays an important role in FE and FTC. Moreover, the mathematical definition of faults has been showed. However, the exact dynamic model of robot manipulator is difficult to determine in a real system. Therefore, the least-square method was applied to identify the dynamic parameters of a real robot manipulator. After that, the point-to-point control and force control were implemented to verify the effectiveness of the hardware setup as well as the dynamic model of a robot manipulator. To implement fault-tolerant control, the estimator was designed to estimate and identify the faults within one step. The extended state observer (ESO), which is easy to implement and fast to compute, was used to estimate the lumps of uncertainties, disturbances and faults. The active fault-tolerant control (AFTC) based on the ESO and super twisting sliding mode control was evaluated for the effectiveness of AFTC. By using the conventional controller in AFTC, the system responds slowly and the performance decreases when faults occur due to the picking phenomenal effect of the FE and slow response of AFTC. However, the AFTC has capable of handling the high magnitude of faults which common in real systems. Therefore, we proposed the AFTC with synchronous sliding mode control (AFTC-SSMC). Due to the ability to make the error at each joint simultaneously approach to zero, the proposed control can reduce the impact of picking phenomena and provide fast recovery compare to the conventional controller. Moreover, due to the constraint inside the synchronous control, the system is able to deal with high magnitude faults. The next proposed AFTC has been developed with the ability to converge in finite-time of controller. In this proposed AFTC, the synchronous terminal sliding mode control (S-TSMC) with ESO has been combined with two novel synchronization position errors. The first proposed synchronization position error is based on the combination of novel synchronization error and coupling position error. The second proposed synchronization position error uses only the novel synchronization position error to reduce the disadvantage of conventional coupling position error in real system. All the proposed AFTCs are proved to be stable based on Lyapunov theory. To implement the proposed AFTC in a real robot manipulator system, a simulation model of the robot was created in Solidworks and then imported into Matlab Simulink to verify the proposed AFTC. After applying to the simulation system, the proposed AFTC was implemented on SAMSUNG 3-DOF FARA-AT2 robot manipulator using FPGA-Labview NI-PXI.