Damping control device and damping control method for vehicle

A damping control device for a vehicle, comprising:

• a control force generating device configured to generate vertical control force between a vehicle body of the vehicle and at least one wheel suspended from the vehicle body by a suspension;
• and
• an electronic control unit configured to reduce, by controlling the control force generating device to change the control force, vibration of the vehicle body that is caused by vertical vibration occurring in the wheel in response to vertical road surface displacements while the vehicle is traveling, the vertical vibration being transmitted to the vibration of the vehicle body via the suspension, wherein:
• the suspension is configured to generate, in a vertical direction between the wheel and the vehicle body, a suspension force that is based on a relative displacement related value related to a vertical relative displacement between the wheel and the vehicle body;
• the suspension force to be actually generated by the suspension is larger than a theoretical suspension force proportional to the relative displacement related value as an amplitude of the vibration occurring in the wheel due to the road surface displacements decreases, and the suspension force is theoretically represented by an expression including a spring term proportional to the relative displacement;
• a magnitude of a component corresponding to the spring term in the suspension force to be actually generated by the suspension is larger than a magnitude of the spring term as the amplitude of the vibration occurring in the wheel due to the road surface displacements decreases;
• and
• the electronic control unit is configured to
• calculate an amplitude index indicating an amplitude of road surface displacement related values related to the road surface displacements in a predetermined sampling zone,
• determine a control gain to increase, as the amplitude indicated by the amplitude index decreases, a magnitude of a target control force that is a target value of the control force at a timing when a predetermined period has elapsed from a current time,
• calculate, based on the control gain and the road surface displacement related values at a predicted passing position where the wheel is predicted to pass at the timing when the predetermined period has elapsed from the current time, the target control force in a direction in which a component of the suspension force that corresponds to a value related to a vertical displacement of the wheel at the predicted passing position is canceled out,
• control the control force generating device to generate the control force to agree with the target control force at the timing when the wheel passes through the predicted passing position, and
• calculate the target control force at a magnitude of a value obtained by multiplying together the control gain and the road surface displacements determined based on the road surface displacement related values at the predicted passing position, and in a direction in which a component of the spring term that corresponds to the vertical displacement of the wheel at the predicted passing position is canceled out.