Improving engine control reliability through software optimization

This paper discusses optimization of software control strategy for eliminating "hitching" and "ringing" in a diesel engine powertrain. Slow- and high-amplitude oscillation of the entire vehicle powertrain under steady pedal position at idle is called "ringing", and similar behavior under cruisecontrol conditions is called "hitching". The intermittent nature of these conditions posed a particular challenge in arriving at proper design alternatives. Zero-point-proportional dynamic S/N ratio was used to quantify vibration and tracking accuracy under six driving conditions, which represented noise factors. An L1 8 orthogonal array explored combinations of six software strategy control factors associated with controlling fuel delivery to the engine. The result was between 4 and 10 dB improvement in vibration reduction, resulting in virtual elimination of the hitching condition. As a result of this effort, a 12 Repair/1000 vehicle reliability (eight million dollar warranty) problem was eliminated. The robust design methodology developed in this application may be used for a variety of applications to optimize similar feedback control strategies.