Automatic speed control device, automatic speed control method, and automatic speed control program

An automatic speed control method for automatically controlling a speed of a vehicle, the automatic speed control method comprising:

• setting an upper limit lateral acceleration degree which is an upper limit value of a lateral acceleration degree allowed while the vehicle is running;
• acquiring a value of a curvature parameter relating to curvature of a road on which the vehicle is scheduled to run;
• calculating a speed of the vehicle at which if the vehicle runs on that road, the lateral acceleration degree of the vehicle becomes the upper limit lateral acceleration degree, based on the curvature parameter of the road, and setting the calculated speed as the upper limit speed;
• and
• controlling the speed of the vehicle to be less than or equal to the upper limit speed, wherein
• the upper limit lateral acceleration degree when the vehicle is running on a connecting road merging with a main road of a motorway or a connecting road branching off from a main road is lower than the upper limit lateral acceleration degree when the vehicle is running on a main road of a motorway,
• a predetermined reference upper limit speed is set as an upper limit speed when a speed of the vehicle corresponding to the upper limit lateral acceleration degree is faster than the reference upper limit speed,
• if, while running on the connecting road, the vehicle is decelerated until the lateral acceleration degree becomes less than a predetermined reacceleration upper limit speed, then is reaccelerated, the reacceleration upper limit speed is set as an upper limit speed when a speed of the vehicle corresponding to the upper limit lateral acceleration degree is faster than the reacceleration upper limit speed, and
• the reacceleration upper limit speed is lower than the reference upper limit speed.

A non-transitory computer medium having recorded thereon a computer program for automatically controlling a speed of a vehicle, the computer program causing a computer to execute a process comprising:

• setting an upper limit lateral acceleration degree which is an upper limit value of a lateral acceleration degree allowed while the vehicle is running;
• acquiring a value of a curvature parameter relating to curvature of a road on which the vehicle is scheduled to run;
• calculating a speed of the vehicle at which if the vehicle runs on that road, the lateral acceleration degree of the vehicle becomes the upper limit lateral acceleration degree, based on the curvature parameter of the road, and setting the calculated speed as the upper limit speed;
• and
• controlling the speed of the vehicle to be less than or equal to the upper limit speed, wherein
• the upper limit lateral acceleration degree when the vehicle is running on a connecting road merging with a main road of a motorway or a connecting road branching off from a main road is lower than the upper limit lateral acceleration degree when the vehicle is running on a main road of a motorway,
• a predetermined reference upper limit speed is set as an upper limit speed when a speed of the vehicle corresponding to the upper limit lateral acceleration degree is faster than the reference upper limit speed,
• if, while running on the connecting road, the vehicle is decelerated until the lateral acceleration degree becomes less than a predetermined reacceleration upper limit speed, then is reaccelerated, the reacceleration upper limit speed is set as an upper limit speed when a speed of the vehicle corresponding to the upper limit lateral acceleration degree is faster than the reacceleration upper limit speed, and
• the reacceleration upper limit speed is lower than the reference upper limit speed.