Feed forward disturbance rejection by a multiple FIFO approach for transient operation of an engine test bench

Frequency bandwidth is a critical property of engine test benches, and is becoming the longer the more important especially in view of hybrid vehicle applications. A critical limiting factor of the bandwidth is the damping of the connection between engine and brake. To overcome this limit, a setup consisting of a stiff connection and an active rejection of the torque ripple has been proposed. Based on repeatability of a working cycle of a combustion engine, prediction and rejection of disturbance is possible for a given value of the system delay. However the delay is spread in different operating points, and its value is in general non known and subject to drastic changes during transient operations. This problem is tackled here by resorting to a time-shift adaptation based on a bank of FIFO memories along with a switching rule depending on the transient operating points - as opposed to stationary operating points. The algorithm is tested in simulation and furthermore applied to a real test bench. The results show the effectiveness of the proposed method.