Driving assistance device, vehicle control system, and driving assistance method for frontal collision detection and avoidance

A driving assistance device mounted in a vehicle with an automated driving control device for automatically controlling steering, acceleration, and deceleration of the vehicle in either of a first state in which a driver is not gripping a steering operation element and a second state in which the driver is gripping the steering operation element, the driving assistance device comprising:

• a storage medium storing computer-readable instructions;
• and
• at least one processor connected to the storage medium, the at least one processor executing the computer-readable instructions to:
• refer to an output of a detection device for detecting that a first object is located in front of the vehicle;
• recognize a lane where the vehicle is located based on the output of the detection device;
• detect, based on a sensor output, whether the driver is gripping the steering operation element;
• determine an avoidance trajectory to avoid a collision with the first object by steering based on the output of the detection device;
• execute one or both of instructing a brake device of the vehicle to stop the vehicle or instructing a steering device of the vehicle to avoid a collision with the first object by steering in response to determining that an indicator value that decreases as the vehicle approaches the first object is less than a first threshold;
• execute a first preliminary operation in response to determining that the indicator value is less than a second threshold;
• execute a second preliminary operation in response to determining that the indicator value is less than a third threshold and determining, at a time point when the indicator value is less than the third threshold, that there is no available travel path along which the vehicle is able to travel on either lateral side of a second object after the vehicle avoids the collision with the first object utilizing automatic steering control;
• and
• accelerate an operation start condition of the second preliminary operation when the automated driving control device is operating in the second state as compared with when the automated driving control device is not operating,
• wherein
• the first threshold is less than the second threshold and the second threshold is less than the third threshold,
• the second preliminary operation includes at least one of outputting braking force, displaying information, outputting sound, or outputting vibration,
• accelerating the operation start condition of the second preliminary operation includes at least one of increasing an amount of the braking force, advancing a start timing of the second preliminary operation, or strengthening an output mode of the displaying, the sound, or the vibration,
• the at least one processor causes an output device to output information for prompting the driver to grip the steering operation element in synchronization with the second preliminary operation when the automated driving control device is operating in the first state,
• after the output device is allowed to output the information, the at least one processor advances an operation timing of the second preliminary operation when the driver is not gripping the steering operation element as compared with when the driver is gripping the steering operation element,
• the second preliminary operation is performed in multiple steps,
• the vehicle has five driving modes from mode A to mode E,
• in mode A, neither a task of monitoring a forward direction of the vehicle nor a task of gripping of a steering wheel is imposed on the driver,
• in mode B, the task of monitoring the forward direction of the vehicle is imposed on the driver but the task of gripping the steering wheel is not imposed on the driver,
• in mode C, the task of monitoring the forward direction of the vehicle and the task of gripping the steering wheel are imposed on the driver,
• in mode D, a task in which a degree of driving operation is required for at least one of steering, acceleration, and deceleration of the vehicle is imposed on the driver,
• in mode E, manual driving in which both steering and acceleration/deceleration is required is performed, and
• the processor further executes the computer-readable instructions to:
• when the automated driving control device is operating in the mode C, advance the operation timing of the second preliminary operation as compared with when the automated driving control device is operating in the mode D or E, and
• when the automated driving control device is operating in the mode A or B, delay the operation timing of the second preliminary operation as compared with when the automated driving control device is operating in the mode D or E.