Frequency compensation control method for opposed-piston two-stroke folded-cranktrain engine's common rail system by loop-shaping theory

A frequency compensation control method for the opposed-piston two-stroke folded-cranktrain (OPFC) diesel engine's common rail system is presented as a result of the study of the loop-shaping theory. A common rail working process and the classical frequency control theory are combined to construct a frequency restriction of common rail pressure. A frequency compensator is utilized to improve the robustness of multiplicative perturbations and disturbance. The loop-shaping method has been applied to design the common rail pressure controller of the OPFC diesel engine. Simulation and bench test results show that in the condition of perturbation that comes from the effect of injection, multi-injection, fuel pumping of a pre-cylinder, and instantaneous pressure fluctuation, the controller indicates high precision. Compared with the original controller, this method improves the control precision by 67.3%.