Closed loop engine roughness control

Abstract

A closed loop engine roughness fuel control for an internal combustion engine operative to maintain the operation of the engine at a predetermined roughness level is disclosed herein. The control measures two rotational intervals within each torque impulse imparted to the engine's crankshaft by the combustion process and generates a speed normalized engine roughness signal indicative of the engine's actual roughness. The engine roughness signal is multiplied by the engine speed and summed with a reference signal to generate a bias signal operative to modify the quantity of fuel being delivered to the engine maintaining the operation of the engine at a predetermined roughness level. A signal indicative of the first derivative of the engine speed is also summed with the reference and roughness signal to compensate for false roughness signals generated during transient modes of operation. A start enrichment circuit, activated when the engine speed is below a predetermined speed, causes the roughness control to output a fixed bias signal indicative of the engine having a roughness level greater than the desired roughness level. The fixed bias signal causes the fuel control computer to increase the quantity of fuel to the engine to enhance starting of the engine and until the engine reaches the predetermined speed.