Drive assist device, and drive assist method

A drive assist device comprising:

• an ECU configured to:
• determine a first recommended operation timing that indicates a timing at which a first driving operation to change a behavior of a vehicle is performed based on an index relating to a relative relationship between the vehicle and a target object;
• estimate, at a timing earlier than the first recommended operation timing, whether a driver of the vehicle performs the first driving operation at the first recommended operation timing;
• determine to execute the drive assist of the vehicle in a case where it is estimated that the driver does not perform the first drive operation at the first recommended operation timing;
• control, in response to the ECU executing the drive assist control, the vehicle to perform at least one from among avoiding the target object and stabilizing a behavior of the vehicle,
• wherein, the ECU is configured to make the first recommended operation timing such that the first recommended operation timing becomes early as a vehicle width direction component of the relative speed between the vehicle and the target object decreases or the vehicle width direction component of the relative distance between the vehicle and the target object increases,
• wherein, in a case where the lateral sensed approach is smaller than a predetermined threshold value, the index is calculated using following Equation (1),
• T_PRE={(V+B·Ax)+K1·Vd}/{L+K2·D} (1), and
• wherein, in a case where a lateral sensed approach, which is expressed by a ratio of the vehicle width direction component of a relative speed between the vehicle and the target object and the vehicle width direction component of the relative distance, is equal to or greater than the predetermined threshold value, the ECU is configured to calculate the index using following Equation (2),
• T_PRE=(V+B·Ax)/L (2)
• wherein in the Equations (1) and (2), T_PRE is the index, V is the vehicle travelling direction component of the relative speed, Vd is the vehicle width direction component of the relative speed, Ax is a deceleration of the vehicle, L is the vehicle travelling direction component of the relative distance, D is the vehicle width direction component of the relative distance, B is a predetermined coefficient, and K1 and K2 are arbitrary coefficients.