In order to improve the transient and static performances of an engine speed control system in a wide speed range, this paper presents an adaptive double closed-loop control strategy. The control scheme possesses intake manifold pressure inner closed-loop adaptive proportional-integral control and engine speed outer closed-loop adaptive proportional-integral control for achieving the tracking precision in a wide range of speed, as well as adaptive nonlinearity and feedforward compensators for overcoming parameter uncertainty and nonlinearity. The whole closed-loop system's stability and the speed tracking convergence are ensured theoretically by the Lyapunov stability theory and the LaSalle invariant principle. The effectiveness of the proposed control strategy is validated through the operation results on the simulator of a V6 engine exploited by the Research Committee of the Society of Instrument and Control Engineers of Japan. KEYWORDS adaptive update, double closed loop, engine speed control system, nonlinearity compensation, parameter uncertainty
INTRODUCTIONWith increasing concern for cleaner environment and fuel conservation, the requirements for vehicle performance, such as drivability, fuel economy, and emissions, have become increasingly higher. For both conventional vehicles and developing hybrid electric vehicles (HEVs), the internal combustion engine (ICE) is indispensable and ubiquitous in nature; hence, control for engine operating performance has been a fundamental issue in the automotive control research field. 1,2 From the view of their essential roles, the engine control inputs contain the fuel injection regulating the stoichiometric air-to-fuel ratio accurately, the throttle angle managing the engine speed in the wide range, and the spark advance generating the engine torque. The speed control problem of the ICE through the angular position of the throttle valve has been one of the key concerns for idle speed, 3-6 cold start, 7 stop-go cruise, 8 and speed regulation 9-16 of the ICE in conventional vehicles and for wide-range speed tracking [17][18][19][20] of ICEs operating at higher speeds in HEVs.The core of engine speed control is to improve the performance of speed responses in any operating condition, thereby, to achieve the drivability and fuel consumption performances. Although many control approaches have been provided for engine speed systems, precise speed control for ICEs during transient operation modes is still a challenging issue. The challenge mainly stems from the uncertainties of the system behavior. While the engine is operating at a wide range of speed variation, the system's physical parameters are uncertain with the impacts of the air path, fuel efficiency, air-to-fuel ratio, spark timing, and so on. To solve the parameter uncertainty problem in the model-based control design of the engine speed system, a lot of efforts have been made from two aspects. On the one hand, the identification/calibration technique is adopted to obtain the physical parameters Int J Adapt Control...