Nonlinear Power Control of an Internal Combustion Engine Without Throttle Actuator

A system consisting of an internal combustion engine (ICE) directly coupled to an electric machine for power generation as in range extenders is considered in this brief. The engine power is mostly controlled by acting on the throttle. A second control loop regulates the air-to-fuel ratio by measuring the exhaust oxygen and acting on the fuel-mass flow, whereas the electric machine is usually considered only for the energy conversion. In this brief, the influence of the throttle and the generator speed on the power control is studied. Moreover, a control strategy is proposed that, by acting on the generator, allows the power control without the need of a throttle actuator. The baseline system was compared with the proposed control strategy. The power control leads to a nonlinear control system that is dealt with via feedback linearization. The control strategy was designed and tested in an experimental prototype. The results validate the proposed control structure that ensures a high fuel conversion efficiency within a wide power range and foregoes the throttle actuator. The highest possible fuel conversion efficiency difference in the operation range is 10%.