IDENTIFICATION OF FAULTS IN DRIVES BASED ON OPTIMAL CONTROL METHODS
Abstract
The paper exams the problem of identifying faults in the drives of robotic systems, the dy-namics model of which is described by linear differential equations. It is proposed to search for a solution to the fault identification problem based on the solution of an auxiliary optimal control problem for a dynamical system in which the role of an unknown vector function describing emerging faults is performed by some auxiliary control, which should provide a minimum for the residual functional. Based on the solution of the auxiliary optimal control problem, a fault diag-nostic observer is proposed. In this case, the fault itself is found through the solution of the corre-sponding algebraic Riccati equation and the differential equation for the auxiliary variable. Un-like popular approaches to solving the problem of fault identification based on observers operat-ing in a sliding mode, the proposed method allows us to expand the class of systems for which the identification problem can be solved. It is known that the methods of sliding mode observers de-sign impose certain restrictions on the systems under consideration. The proposed approach based on optimal control can also give results for systems with nonlinear dynamics. In this case, methods of approximate solution of optimal control problems based on the representation of the system in linear form with state-dependent coefficients (the so-called State-dependent Riccati Equation, SDRE) are likely to be effective. The improvement of the proposed method in this direction will be the subject of further research. The stated theory is shown on the example of fault identification in a DC drive. Different cases are considered for a system with complete observations (the entire state vector is known) and with incomplete observations. It was shown during the simulation that the quality of faults identification can be improved by selecting the appropriate values of the pen-alty matrices in the residual functional, while it is possible to achieve good diagnostics separately through various channels of faults occurrence. The paper presents recommendations on the choice of penalty matrices. The simulation results confirmed the operability of the diagnostic observers synthesized using the proposed method
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