A new control system for permanent magnet synchronous motor electric drives with asignificant torsion vibration mode in the mechanical coupling is presented based entirely on sliding modeprinciples to achieve robustness against external load torques and parametric modelling uncertainties. Theuser is only required to provide the demanded position and specify the settling time, no controller tuningbeing necessary. The vector control condition of keeping the direct axis current component approximatelyzero is satisfied as well as controlling either the rotor or load position to follow the demanded position withprescribed closed loop dynamics. To avoid control chatter, a boundary layer is introduced by replacing therelay control switching transfer characteristic (signum function) by a high gain having the same controlsaturation limits. Any steady state errors with a constant demanded rotor angle due to the finite value of theaforementioned gain are eliminated by means of an outer integral control loop. The simulations predict thatthe desired robustness will be achieved.
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