Non-linear feedback controller for internal combustion engine

Claim 1

A non-linear feedback controller for an internal combustion engine, the controller determining a control quantity which is feedback-input to the internal combustion engine according to a dynamic physical model of said internal combustion engine, the model being obtained by approximation from an equation of motion of said internal combustion engine and a mathematical formula expressing mass conservation of the quantity of intake air sucked into said internal combustion engine, thereby controlling the rotational speed of said internal combustion engine, said controller comprising: operating condition detecting means for detecting at least an intake pressure equivalent quantity which is equivalent to an intake pressure of said internal combustion engine and a rotational speed equivalent quantity which is equivalent to a rotational speed of said internal combustion engine; opening area control means for controlling the opening area of an intake passage of said internal combustion engine in accordance with an external command manipulating quantity; control means for calculating a control quantity concerned with the control of the opening area of the intake passage of said internal combustion engine from at least the intake pressure equivalent quantity and rotational speed equivalent quantity detected by said operating condition detecting means by using a parameter set on the basis of the dynamic physical model of said internal combustion engine; and compensating means for outputting a manipulating quantity to said opening area controlling means in such a manner that, when the intake pressure equivalent quantity detected by said operating condition detecting means is equal to or less than a critical pressure equivalent quantity, a value which is determined on the basis of the control quantity calculated by said control means and a predetermined constant is defined as a manipulating quantity; whereas, when the intake pressure equivalent quantity exceeds the critical pressure equivalent quantity, a value obtained by compensating said control quantity in accordance with said intake pressure equivalent quantity is defined as a manipulating quantity.