Vehicle travel control apparatus

A vehicle travel control apparatus having a vehicle speed control unit which controls a vehicle speed of an own vehicle on the basis of a target vehicle-to-vehicle distance between the own vehicle and a preceding vehicle in front thereof set beforehand, comprising:

• a vehicle-to-vehicle distance detection unit which detects a vehicle-to-vehicle distance between the own vehicle and the preceding vehicle in front thereof;
• an external situation recognition unit which recognizes an external situation in the surroundings of the own vehicle;
• an utility function determination unit which determines a particular utility function from a plurality of utility functions based on the target vehicle speed and the detected vehicle speed, wherein each of the utility functions represents a predetermined functional relationship between a manipulated variable for vehicle speed control, which is a manipulated variable for controlling the vehicle speed of the own vehicle, and a utility index value, which is an index value representing an effectiveness degree of controlling the vehicle speed of the own vehicle according to each value of the manipulated variable for vehicle speed control;
• a travel inhibition degree function determination unit which determines a particular travel inhibition degree function from a plurality of travel inhibition degree functions based on the recognized external situation, wherein each of the travel inhibition degree functions represents a predetermined functional relationship between the manipulated variable for vehicle speed control and a travel inhibition degree index value which is an index value representing an inhibition degree of the travel of the own vehicle expected in the case where the vehicle speed of the own vehicle is controlled according to each value of the manipulated variable for vehicle speed control;
• and
• an appropriateness function determination unit which determines a particular appropriateness function by combining the particular utility function and the particular travel inhibition degree function, wherein the particular appropriateness function represents a relationship between the manipulated variable for vehicle speed control and an appropriateness of each value of the manipulated variable for vehicle speed control;
• wherein the vehicle speed control unit is configured to calculate the appropriateness of each value of the manipulated variable for vehicle speed control using the particular appropriateness function, and to control the vehicle speed of the own vehicle by manipulating a driving/braking force of the own vehicle according to the value of the manipulated variable for vehicle speed control corresponding to a highest calculated appropriateness.