PMSM Sensorless Control Based On Fourth-Order Sliding Mode Observer

With large torque inertia ratio, high energy density and high efficiency among their many excellent features, permanent magnet synchronous motors (PMSMs) have been widely used in various applications such as aerospace, electric vehicles, household appliances and industrial control. The exact position of the rotor is key to the vector control of PMSMs, and this paper is a study on the sensorless control of PMSMs based on a fourth-order sliding mode observer. The main work includes:A brief instruction is made to the coordinate transformation, the mathematical model and the principle of vector control of PMSM under static and rotary coordination systems, respectively. Subsequency, a discussion is delivered for the speed regulating scheme of PMSM under vector control.The pricinple and application of sliding mode observer are elaborated. A fourth-order sliding mode observer is established for the counter-electronotive force and the current of PMSM. PMSM sensorless speed control structure and simulation model is established based on fourth-order sliding mode observer. And the simulation results showed that the algorithm of fourth-order sliding mode observer which is worked in the PMSM sensorless control system is effective and reasonable.The control system of the software and hardware are designed using the TMS320LF2407A chip. To the hardware, each part of the control circuit, protection circuit and detection circuit are thoroughly discussed. The control software is being programmed with C and assembly language. And then, the flow charts of main program and each interrupt program are given. The preliminary experimental results reflect the relationship between the counter-electromotive and speed, verify the correct and reasonable of the algorithm proposed in this paper.