Sensorless position control of DC actuators for automotive applications

Among automotive actuators, those equipping power windows, seat and mirror positioning require a quite precise position control, either for easy of usage, either for safety reasons. Noticeable cost reductions can be obtained on such kind of actuators by elimination of Hall effect position sensors. This can be accomplished by sensorless estimating the position of the shaft. Unfortunately, because of their limited precision classic sensorless methods based on integration of the armature voltage are not suitable for such specific application. The method proposed in this paper allows to estimate the position of the rotor shaft by detecting periodical oscillations of the armature current caused by rotor slotting. A key feature of the developed angular position estimation algorithm is that its precision is sufficient to correctly drive a window lift, also performing soft landing and pinch protection, while being suitable to be implemented even on low cost 10 MHz, 8-bit microcontrollers with few kilobites of memory.