1988-11-01

Stability Analysis of Engine Revolution by a Chassis and Powertrain Dynamics Simulator 881778

This paper discusses causes and the mechanism of surging, back and forth chassis oscillation which occurs in cars with electronically controlled multi-point gasoline injection systems. This occurs during sharp acceleration, engine braking deceleration, and low speed coasting, at rather low ratio gear positions.
We conclude that the mechanism of surging is parametric coupled oscillation. This conclusion is based on experimental data analysts and parameter sensitivity analysis using a chassis and engine dynamics simulator. The elements of parametric coupled oscillation are: a forcing system composed of engine control systems, engine and power transmission systems; a resonance system composed of axle and frame-body translation systems; a feedback system composed of axle translation systems and wheel revolution systems.
Induced air mass flow and engine revolution speed, used in calculations of gasoline injection amount and ignition timing, differ from those during the period of actual gasoline injection, gasoline-air mixing and mixture induction process into the cylinder. This causes fluctuations in the mixture concentration and ignition timing from the target values, and results in a fluctuation in engine output torque, which develops into surging.
Based on the above discussion, this paper proposes a method to suppress surging, which controls the torque fluctuation by manipulating the air-fuel mixture concentration and ignition timing, taking the relative motion characteristics between the frame-body and axles into account. The method is based on the idea that the fluctuation of output torque generated during one stroke is compensated during the next one. This is effective for acceleration, decerleration and engine rotation speed stabilization in no load idling status.

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