Zebra Tape Butt Joint Algorithm for Torsional Vibrations

Abstract

At the development stage of automobile constructions, many powertrain configurations may be considered. Due to complicated coupling mechanisms, the natural frequencies of the combined system are difficult to predict. It is therefore necessary to run tests on automotive subsystems under realistic operating conditions. To completely understand the dynamic behaviour, a study of both torsional and translational motions along the driveshaft is necessary. Torsional vibrations can conveniently be measured at any point along a rotating shaft by using a zebra tape that overcomes the drawbacks of existing systems which are either expensive or require time-consuming and difficult shaft modifications. Zebra tapes however require a dedicated DSP processing due to the butt joint of the two tape ends. This paper presents a new algorithm to correct the tacho moments obtained from pulses generated with a high quality zebra tape glued on a rotating shaft with torsional vibrations. Due to the misalignment of the stripe pattern at the joint of the two tape ends, the tacho moments are not evenly distributed over the shaft. The angle between subsequent tacho moments is exactly the same except at the butt joint. The algorithm first identifies the position and angular interval at the butt joint by using an angle estimator function and a dedicated spline interpolation and FIR bandpass filter. This information then allows to reconstruct the exact angle evolution and perform a proper torsional vibration analysis. First, the principles of the butt joint correction algorithm are discussed. Then, an error analysis is performed on a simulated dataset, evaluating the accuracy of the algorithm in the presence of torsional vibrations.