Active fault tolerant scheme for variable speed drives under actuator and sensor faults

In this paper, an active fault tolerant control (AFTC) architecture is suggested for nonlinear systems, where actuator and sensor faults are addressed. The nonlinear structure is specially suited to describe some electric motors, and the ideas here developed can be applied to design more reliable variable speed drives. The AFTC scheme departs from a nominal control law previously designed. The fault diagnosis and isolation (FDI) structure is carried out in two stages. First, a fault condition is detected, and next a fault isolation and identification is performed. Hence, according to the FDI structure, the control algorithm can follow four scenarios: (i) operate in open-loop, (ii) replace missing/erroneous sensors by virtual ones, (iii) adjust the references for a faulty actuator, and (iv) reconfigure the control law. The application to a DC motor in parallel configuration is illustrated, and the evaluation is carried experimentally in a 2 HP test-bed.