Turn assist device for vehicle, turn assist method for vehicle, and computer-readable medium storing turn assist program

A non-transitory computer readable medium storing a turn assist program executed by a controller for a vehicle, the vehicle including wheels including a front wheel and a rear wheel, a rear wheel steering device that adjusts a steered angle of the rear wheel, and a steering wheel, the front wheel being configured to be steered in accordance with a steering operation of the steering wheel, the turn assist program being configured to cause the controller to execute:

• a time obtaining process that obtains collision prediction time, the collision prediction time being a predicted value of an amount of time before the vehicle collides with an obstacle in a case in which the vehicle is approaching the obstacle;
• a turn assist process in a case in which the steering operation of the steering wheel is in progress in a situation in which the collision prediction time is shorter than or equal to determination prediction time, the turn assist process assisting turning of the vehicle by outputting a command for steering the rear wheel to the rear wheel steering device;
• and
• a target value obtaining process that obtains a lateral acceleration target value based on a vehicle speed and a steering angle of the steering wheel, the lateral acceleration target value being a target value of a lateral acceleration of the vehicle, wherein
• the turn assist process includes:
• an in-phase process that outputs, to the rear wheel steering device, a command for steering the rear wheel in a same direction as a steering direction of the front wheel, and
• a counter-phase process that outputs, to the rear wheel steering device, a command for steering the rear wheel in a direction opposite to the steering direction of the front wheel when a difference between an actual value of the lateral acceleration of the vehicle and the lateral acceleration target value exceeds a difference determination value during execution of the in-phase process.

A turn assist method for a vehicle, the vehicle including wheels including a front wheel and a rear wheel, a rear wheel steering device that adjusts a steered angle of the rear wheel, and a steering wheel, the front wheel being configured to be steered in accordance with a steering operation of the steering wheel, the turn assist method comprising:

• obtaining collision prediction time, the collision prediction time being a predicted value of an amount of time before the vehicle collides with an obstacle in a case in which the vehicle is approaching the obstacle;
• obtaining a lateral acceleration target value based on a vehicle speed and a steering angle of the steering wheel, the lateral acceleration target value being a target value of a lateral acceleration of the vehicle;
• and
• executing a turn assist process in a case in which the steering operation of the steering wheel is in progress in a situation in which the collision prediction time is shorter than or equal to determination prediction time, the turn assist process assisting turning of the vehicle by outputting a command for steering the rear wheel to the rear wheel steering device, wherein
• the turn assist process includes:
• an in-phase process that outputs, to the rear wheel steering device, a command for steering the rear wheel in a same direction as a steering direction of the front wheel, and
• a counter-phase process that outputs, to the rear wheel steering device, a command for steering the rear wheel in a direction opposite to the steering direction of the front wheel when a difference between an actual value of the lateral acceleration of the vehicle and the lateral acceleration target value exceeds a difference determination value during execution of the in-phase process.