Direct torque and flux control of IPM synchronous motor drive using input-output feedback linearization approach

A novel direct torque and flux controlled interior permanent magnet synchronous motor drive is proposed based on the nonlinear model presented in the stator flux reference frame. An input-output feedback linearization technique is employed to linearize the nonlinear dynamics of the motor and enable a precise control over the linearized system in a wide range of operation by means of the well-developed linear controllers. In this case, a modified variable gain PI controller handles the control task in the speed closed loop which is capable of superior performance to classical PI in terms of overshooting, settling performance as well as disturbance rejection. The challenging task of parameters estimation is also carried out with two online parameter estimators which operate in parallel. An adaptive estimation unit is in charge of stator resistance and magnetic flux values while the direct and quadrature axis inductances are estimated through recursive least square method. In fact, such a combination of estimators features the proper rate of estimation for motor parameters while avoiding the heavy computational burden of RLSE for simultaneous estimation of four motor parameters. The overall stability of the proposed IOFL controller is analytically proven through Lyapunov theory. The effectiveness of the presented scheme is also verified through simulation studies.