Microprocessor controlled natural gas carburetor

The goal of the microprocessor controlled natural gas carburetor is to accurately regulate stoichiometric air-to-fuel ratio in a natural gas internal combustion engine. In previous work, a standard natural gas carburetor was adapted to allow stepper motor adjustment of the spring preload on the carburetor diaphragm. This system was characterized by acceptable steady-state performance, but sluggish response to transients. In current work, a 2.8 L engine is instrumented with an exhaust gas oxygen (EGO) sensor, providing closed-loop feedback to a dedicated microprocessor. The EGO sensor indicates deviation from stoichiometric operation. The control hardware includes comparators which test the EGO sensor voltage. An Intel 8031 microprocessor responds accordingly to comparator outputs, and controls the stepper motor (adjusting air-to-fuel ratio), implementing a "bang-bang" control scheme. Results are discussed and possible improvements are suggested.<>