Asynchronous observer for a copier paper path

A copier contains optical sensors along its paperpath to detect sheet positions and velocities. A measurement occurs when a sheet crosses a sensor. The measurement time may not coincide with the controller sample time. This paper presents an approach to more accurately process the asynchronous measurements without increasing the sampling frequency. An oversampled Kalman filter is used in between two controller sampling instants. The observer sampling rate remains equal to the controller sampling rate without loss in performance, since the Kalman filter equations can be evaluated in batch at the controller sampling instants. A look-up table reduces the computational load.