Driveline Launch Control by a Test-Based Nonparametric QFT Method

Abstract

A novel Nonparametric (NP) Nonlinear Quantitative Feedback Theory (QFT) robust control design method is experimentally applied to the driveline launch, tracking and shuffle control problem. In the experimental setup the engine Air Bleed Valve (ABV) duty cycle (DTY) is used as an excitation input signal and the vehicle wheel speed is the controlled output. The input signal is formed as PRBS with different amplitudes and different Perturbation Periods (PPs). The NP-QFT design technique uses the discrete Hilbert transform to determine the necessary phase shift to produce the stable minimum phase (SMP) nominal plant required by the QFT approach for the non minimum phase (NMP) driveline plant. The tracking performance for the driveline with the designed controller is tested on a chassis dynamometer by several step speed demands and was found to fall within the specified response boundaries. The controlled system disturbance rejection is tested by applying a step torque to the chassis dynamometer rollers against the wheel rotation direction. The resulting speed disturbance is rejected and remains within the required limits. In contrast to previously proposed techniques the new approach does not require any parametric model and relies entirely on the non-parametric frequency response characterisation of the vehicle driveline dynamics which can be obtained quickly from experimental input output data. The NP-QFT technique is entirely systematic and does not rely on trial and error (cut and try) procedures and should significantly speed the industrial development of driveline control systems.