Frequency domain synthesis of an idle speed control system for a fuel injected engine

Presented in this paper is a methodology for designing feedback controllers for systems with parallel loops where the control objective is to maintain its operating condition within a small tolerance despite an external disturbance. Specifically, the system output due to the external disturbance is required to remain within a prespecified range subjected to the constraint that each control effort is limited by its hardware. The methodology presented is in the frequency domain and based on the premise that feedback is necessitated by plant uncertainty and external disturbances. Therefore, the amount of feedback used must be contingent on the amount of uncertainty present in the system. The cost of using feedback to reduce system sensitivity and achieve disturbance rejection is reflected in the bandwidth of the controller which for all practical purposes must be minimized. Demonstrating the methodology will be a controller design of the idle speed control for a V-6 fuel injected engine modeled as a system with parallel loops.